Using High Spatial Resolution to Improve BOLD fMRI Detection at 3T

PubMed Central

Claise, Béatrice; Jean, Betty

2015-01-01

For different functional magnetic resonance imaging experiments using blood oxygenation level-dependent (BOLD) contrast, the acquisition of T 2*-weighted scans at a high spatial resolution may be advantageous in terms of time-course signal-to-noise ratio and of BOLD sensitivity when the regions are prone to susceptibility artifacts. In this study, we explore this solution by examining how spatial resolution influences activations elicited when appetizing food pictures are viewed. Twenty subjects were imaged at 3 T with two different voxel volumes, 3.4 μl and 27 μl. Despite the diminution of brain coverage, we found that high-resolution acquisition led to a better detection of activations. Though known to suffer to different degrees from susceptibility artifacts, the activations detected by high spatial resolution were notably consistent with those reported in published activation likelihood estimation meta-analyses, corresponding to taste-responsive regions. Furthermore, these regions were found activated bilaterally, in contrast with previous findings. Both the reduction of partial volume effect, which improves BOLD contrast, and the mitigation of susceptibility artifact, which boosts the signal to noise ratio in certain regions, explained the better detection noted with high resolution. The present study provides further evidences that high spatial resolution is a valuable solution for human BOLD fMRI, especially for studying food-related stimuli. PMID:26550990

Single-trial EEG-informed fMRI reveals spatial dependency of BOLD signal on early and late IC-ERP amplitudes during face recognition.

PubMed

Wirsich, Jonathan; Bénar, Christian; Ranjeva, Jean-Philippe; Descoins, Médéric; Soulier, Elisabeth; Le Troter, Arnaud; Confort-Gouny, Sylviane; Liégeois-Chauvel, Catherine; Guye, Maxime

2014-10-15

Simultaneous EEG-fMRI has opened up new avenues for improving the spatio-temporal resolution of functional brain studies. However, this method usually suffers from poor EEG quality, especially for evoked potentials (ERPs), due to specific artifacts. As such, the use of EEG-informed fMRI analysis in the context of cognitive studies has particularly focused on optimizing narrow ERP time windows of interest, which ignores the rich diverse temporal information of the EEG signal. Here, we propose to use simultaneous EEG-fMRI to investigate the neural cascade occurring during face recognition in 14 healthy volunteers by using the successive ERP peaks recorded during the cognitive part of this process. N170, N400 and P600 peaks, commonly associated with face recognition, were successfully and reproducibly identified for each trial and each subject by using a group independent component analysis (ICA). For the first time we use this group ICA to extract several independent components (IC) corresponding to the sequence of activation and used single-trial peaks as modulation parameters in a general linear model (GLM) of fMRI data. We obtained an occipital-temporal-frontal stream of BOLD signal modulation, in accordance with the three successive IC-ERPs providing an unprecedented spatio-temporal characterization of the whole cognitive process as defined by BOLD signal modulation. By using this approach, the pattern of EEG-informed BOLD modulation provided improved characterization of the network involved than the fMRI-only analysis or the source reconstruction of the three ERPs; the latter techniques showing only two regions in common localized in the occipital lobe. Copyright © 2014 Elsevier Inc. All rights reserved.

Spatial band-pass filtering aids decoding musical genres from auditory cortex 7T fMRI.

PubMed

Sengupta, Ayan; Pollmann, Stefan; Hanke, Michael

2018-01-01

Spatial filtering strategies, combined with multivariate decoding analysis of BOLD images, have been used to investigate the nature of the neural signal underlying the discriminability of brain activity patterns evoked by sensory stimulation -- primarily in the visual cortex. Reported evidence indicates that such signals are spatially broadband in nature, and are not primarily comprised of fine-grained activation patterns. However, it is unclear whether this is a general property of the BOLD signal, or whether it is specific to the details of employed analyses and stimuli. Here we performed an analysis of publicly available, high-resolution 7T fMRI on the response BOLD response to musical genres in primary auditory cortex that matches a previously conducted study on decoding visual orientation from V1.  The results show that the pattern of decoding accuracies with respect to different types and levels of spatial filtering is comparable to that obtained from V1, despite considerable differences in the respective cortical circuitry.

Lower Working Memory Performance in Overweight and Obese Adolescents Is Mediated by White Matter Microstructure

PubMed Central

Alarcón, Gabriela; Ray, Siddharth; Nagel, Bonnie J.

2017-01-01

Objectives Elevated body mass index (BMI) is associated with deficits in working memory, reduced gray matter volume in frontal and parietal lobes, as well as changes in white matter (WM) microstructure. The current study examined whether BMI was related to working memory performance and blood oxygen level dependent (BOLD) activity, as well as WM microstructure during adolescence. Methods Linear regressions with BMI and (1) verbal working memory BOLD signal, (2) spatial working memory BOLD signal, and (3) fractional anisotropy (FA), a measure of WM microstructure, were conducted in a sample of 152 healthy adolescents ranging in BMI. Results BMI was inversely related to IQ and verbal and spatial working memory accuracy; however, there was no significant relationship between BMI and BOLD response for either verbal or spatial working memory. Furthermore, BMI was negatively correlated with FA in the left superior longitudinal fasciculus (SLF) and left inferior longitudinal fasciculus (ILF). ILF FA and IQ significantly mediated the relationship between BMI and verbal working memory performance, whereas SLF FA, but not IQ, significantly mediated the relationship between BMI and accuracy of both verbal and spatial working memory. Conclusions These findings indicate that higher BMI is associated with decreased FA in WM fibers connecting brain regions that support working memory, and that WM microstructural deficits may underlie inferior working memory performance in youth with higher BMI. Of interest, BMI did not show the same relationship with working memory BOLD activity, which may indicate that changes in brain structure precede changes in function. PMID:26708324

Biophysical and physiological origins of blood oxygenation level-dependent fMRI signals.

PubMed

Kim, Seong-Gi; Ogawa, Seiji

2012-07-01

After its discovery in 1990, blood oxygenation level-dependent (BOLD) contrast in functional magnetic resonance imaging (fMRI) has been widely used to map brain activation in humans and animals. Since fMRI relies on signal changes induced by neural activity, its signal source can be complex and is also dependent on imaging parameters and techniques. In this review, we identify and describe the origins of BOLD fMRI signals, including the topics of (1) effects of spin density, volume fraction, inflow, perfusion, and susceptibility as potential contributors to BOLD fMRI, (2) intravascular and extravascular contributions to conventional gradient-echo and spin-echo BOLD fMRI, (3) spatial specificity of hemodynamic-based fMRI related to vascular architecture and intrinsic hemodynamic responses, (4) BOLD signal contributions from functional changes in cerebral blood flow (CBF), cerebral blood volume (CBV), and cerebral metabolic rate of O(2) utilization (CMRO(2)), (5) dynamic responses of BOLD, CBF, CMRO(2), and arterial and venous CBV, (6) potential sources of initial BOLD dips, poststimulus BOLD undershoots, and prolonged negative BOLD fMRI signals, (7) dependence of stimulus-evoked BOLD signals on baseline physiology, and (8) basis of resting-state BOLD fluctuations. These discussions are highly relevant to interpreting BOLD fMRI signals as physiological means.

Biophysical and physiological origins of blood oxygenation level-dependent fMRI signals

PubMed Central

Kim, Seong-Gi; Ogawa, Seiji

2012-01-01

After its discovery in 1990, blood oxygenation level-dependent (BOLD) contrast in functional magnetic resonance imaging (fMRI) has been widely used to map brain activation in humans and animals. Since fMRI relies on signal changes induced by neural activity, its signal source can be complex and is also dependent on imaging parameters and techniques. In this review, we identify and describe the origins of BOLD fMRI signals, including the topics of (1) effects of spin density, volume fraction, inflow, perfusion, and susceptibility as potential contributors to BOLD fMRI, (2) intravascular and extravascular contributions to conventional gradient-echo and spin-echo BOLD fMRI, (3) spatial specificity of hemodynamic-based fMRI related to vascular architecture and intrinsic hemodynamic responses, (4) BOLD signal contributions from functional changes in cerebral blood flow (CBF), cerebral blood volume (CBV), and cerebral metabolic rate of O2 utilization (CMRO2), (5) dynamic responses of BOLD, CBF, CMRO2, and arterial and venous CBV, (6) potential sources of initial BOLD dips, poststimulus BOLD undershoots, and prolonged negative BOLD fMRI signals, (7) dependence of stimulus-evoked BOLD signals on baseline physiology, and (8) basis of resting-state BOLD fluctuations. These discussions are highly relevant to interpreting BOLD fMRI signals as physiological means. PMID:22395207

Intersession reliability of fMRI activation for heat pain and motor tasks

PubMed Central

Quiton, Raimi L.; Keaser, Michael L.; Zhuo, Jiachen; Gullapalli, Rao P.; Greenspan, Joel D.

2014-01-01

As the practice of conducting longitudinal fMRI studies to assess mechanisms of pain-reducing interventions becomes more common, there is a great need to assess the test–retest reliability of the pain-related BOLD fMRI signal across repeated sessions. This study quantitatively evaluated the reliability of heat pain-related BOLD fMRI brain responses in healthy volunteers across 3 sessions conducted on separate days using two measures: (1) intraclass correlation coefficients (ICC) calculated based on signal amplitude and (2) spatial overlap. The ICC analysis of pain-related BOLD fMRI responses showed fair-to-moderate intersession reliability in brain areas regarded as part of the cortical pain network. Areas with the highest intersession reliability based on the ICC analysis included the anterior midcingulate cortex, anterior insula, and second somatosensory cortex. Areas with the lowest intersession reliability based on the ICC analysis also showed low spatial reliability; these regions included pregenual anterior cingulate cortex, primary somatosensory cortex, and posterior insula. Thus, this study found regional differences in pain-related BOLD fMRI response reliability, which may provide useful information to guide longitudinal pain studies. A simple motor task (finger-thumb opposition) was performed by the same subjects in the same sessions as the painful heat stimuli were delivered. Intersession reliability of fMRI activation in cortical motor areas was comparable to previously published findings for both spatial overlap and ICC measures, providing support for the validity of the analytical approach used to assess intersession reliability of pain-related fMRI activation. A secondary finding of this study is that the use of standard ICC alone as a measure of reliability may not be sufficient, as the underlying variance structure of an fMRI dataset can result in inappropriately high ICC values; a method to eliminate these false positive results was used in this study and is recommended for future studies of test–retest reliability. PMID:25161897

Multiple sclerosis-related white matter microstructural change alters the BOLD hemodynamic response.

PubMed

Hubbard, Nicholas A; Turner, Monroe; Hutchison, Joanna L; Ouyang, Austin; Strain, Jeremy; Oasay, Larry; Sundaram, Saranya; Davis, Scott; Remington, Gina; Brigante, Ryan; Huang, Hao; Hart, John; Frohman, Teresa; Frohman, Elliot; Biswal, Bharat B; Rypma, Bart

2016-11-01

Multiple sclerosis (MS) results in inflammatory damage to white matter microstructure. Prior research using blood-oxygen-level dependent (BOLD) imaging indicates MS-related alterations to brain function. What is currently unknown is the extent to which white matter microstructural damage influences BOLD signal in MS. Here we assessed changes in parameters of the BOLD hemodynamic response function (HRF) in patients with relapsing-remitting MS compared to healthy controls. We also used diffusion tensor imaging to assess whether MS-related changes to the BOLD-HRF were affected by changes in white matter microstructural integrity. Our results showed MS-related reductions in BOLD-HRF peak amplitude. These MS-related amplitude decreases were influenced by individual differences in white matter microstructural integrity. Other MS-related factors including altered reaction time, limited spatial extent of BOLD activity, elevated lesion burden, or lesion proximity to regions of interest were not mediators of group differences in BOLD-HRF amplitude. Results are discussed in terms of functional hyperemic mechanisms and implications for analysis of BOLD signal differences. © The Author(s) 2015.

Sex differences in the neural substrates of spatial working memory during adolescence are not mediated by endogenous testosterone

PubMed Central

Alarcón, Gabriela; Cservenka, Anita; Fair, Damien A.; Nagel, Bonnie J.

2014-01-01

Adolescence is a developmental period characterized by notable changes in behavior, physical attributes, and an increase in endogenous sex steroid hormones, which may impact cognitive functioning. Moreover, sex differences in brain structure are present, leading to differences in neural function and cognition. Here, we examine sex differences in performance and blood oxygen level-dependent (BOLD) activation in a sample of adolescents during a spatial working memory (SWM) task. We also examine whether endogenous testosterone levels mediate differential brain activity between the sexes. Adolescents between ages 10 and 16 completed a SWM functional magnetic resonance imaging (fMRI) task, and serum hormone levels were assessed within seven days of scanning. While there were no sex differences in task performance (accuracy and reaction time), differences in BOLD response between girls and boys emerged, with girls deactivating brain regions in the default mode network and boys showing increased response in SWM-related brain regions of the frontal cortex. These results suggest that adolescent boys and girls adopted distinct neural strategies, while maintaining spatial cognitive strategies that facilitated comparable cognitive performance of a SWM task. A nonparametric bootstrapping procedure revealed that testosterone did not mediate sex-specific brain activity, suggesting that sex differences in BOLD activation during SWM may be better explained by other factors, such as early organizational effects of sex steroids or environmental influences. Elucidating sex differences in neural function and the influence of gonadal hormones can serve as a basis of comparison for understanding sexually dimorphic neurodevelopment and inform sex-specific psychopathology that emerges in adolescence. PMID:25312831

Functional localization of the human color center by decreased water displacement using diffusion-weighted fMRI.

PubMed

Williams, Rebecca J; Reutens, David C; Hocking, Julia

2015-11-01

Decreased water displacement following increased neural activity has been observed using diffusion-weighted functional MRI (DfMRI) at high b-values. The physiological mechanisms underlying the diffusion signal change may be unique from the standard blood oxygenation level-dependent (BOLD) contrast and closer to the source of neural activity. Whether DfMRI reflects neural activity more directly than BOLD outside the primary cerebral regions remains unclear. Colored and achromatic Mondrian visual stimuli were statistically contrasted to functionally localize the human color center Area V4 in neurologically intact adults. Spatial and temporal properties of DfMRI and BOLD activation were examined across regions of the visual cortex. At the individual level, DfMRI activation patterns showed greater spatial specificity to V4 than BOLD. The BOLD activation patterns were more prominent in the primary visual cortex than DfMRI, where activation was localized to the ventral temporal lobe. Temporally, the diffusion signal change in V4 and V1 both preceded the corresponding hemodynamic response, however the early diffusion signal change was more evident in V1. DfMRI may be of use in imaging applications implementing cognitive subtraction paradigms, and where highly precise individual functional localization is required.

Multiband multi-echo imaging of simultaneous oxygenation and flow timeseries for resting state connectivity.

PubMed

Cohen, Alexander D; Nencka, Andrew S; Lebel, R Marc; Wang, Yang

2017-01-01

A novel sequence has been introduced that combines multiband imaging with a multi-echo acquisition for simultaneous high spatial resolution pseudo-continuous arterial spin labeling (ASL) and blood-oxygenation-level dependent (BOLD) echo-planar imaging (MBME ASL/BOLD). Resting-state connectivity in healthy adult subjects was assessed using this sequence. Four echoes were acquired with a multiband acceleration of four, in order to increase spatial resolution, shorten repetition time, and reduce slice-timing effects on the ASL signal. In addition, by acquiring four echoes, advanced multi-echo independent component analysis (ME-ICA) denoising could be employed to increase the signal-to-noise ratio (SNR) and BOLD sensitivity. Seed-based and dual-regression approaches were utilized to analyze functional connectivity. Cerebral blood flow (CBF) and BOLD coupling was also evaluated by correlating the perfusion-weighted timeseries with the BOLD timeseries. These metrics were compared between single echo (E2), multi-echo combined (MEC), multi-echo combined and denoised (MECDN), and perfusion-weighted (PW) timeseries. Temporal SNR increased for the MECDN data compared to the MEC and E2 data. Connectivity also increased, in terms of correlation strength and network size, for the MECDN compared to the MEC and E2 datasets. CBF and BOLD coupling was increased in major resting-state networks, and that correlation was strongest for the MECDN datasets. These results indicate our novel MBME ASL/BOLD sequence, which collects simultaneous high-resolution ASL/BOLD data, could be a powerful tool for detecting functional connectivity and dynamic neurovascular coupling during the resting state. The collection of more than two echoes facilitates the use of ME-ICA denoising to greatly improve the quality of resting state functional connectivity MRI.

Task Dependence, Tissue Specificity, and Spatial Distribution of Widespread Activations in Large Single-Subject Functional MRI Datasets at 7T

PubMed Central

Gonzalez-Castillo, Javier; Hoy, Colin W.; Handwerker, Daniel A.; Roopchansingh, Vinai; Inati, Souheil J.; Saad, Ziad S.; Cox, Robert W.; Bandettini, Peter A.

2015-01-01

It was recently shown that when large amounts of task-based blood oxygen level–dependent (BOLD) data are combined to increase contrast- and temporal signal-to-noise ratios, the majority of the brain shows significant hemodynamic responses time-locked with the experimental paradigm. Here, we investigate the biological significance of such widespread activations. First, the relationship between activation extent and task demands was investigated by varying cognitive load across participants. Second, the tissue specificity of responses was probed using the better BOLD signal localization capabilities of a 7T scanner. Finally, the spatial distribution of 3 primary response types—namely positively sustained (pSUS), negatively sustained (nSUS), and transient—was evaluated using a newly defined voxel-wise waveshape index that permits separation of responses based on their temporal signature. About 86% of gray matter (GM) became significantly active when all data entered the analysis for the most complex task. Activation extent scaled with task load and largely followed the GM contour. The most common response type was nSUS BOLD, irrespective of the task. Our results suggest that widespread activations associated with extremely large single-subject functional magnetic resonance imaging datasets can provide valuable information about the functional organization of the brain that goes undetected in smaller sample sizes. PMID:25405938

Caffeine reduces resting-state BOLD functional connectivity in the motor cortex.

PubMed

Rack-Gomer, Anna Leigh; Liau, Joy; Liu, Thomas T

2009-05-15

In resting-state functional magnetic resonance imaging (fMRI), correlations between spontaneous low-frequency fluctuations in the blood oxygenation level dependent (BOLD) signal are used to assess functional connectivity between different brain regions. Changes in resting-state BOLD connectivity measures are typically interpreted as changes in coherent neural activity across spatially distinct brain regions. However, this interpretation can be complicated by the complex dependence of the BOLD signal on both neural and vascular factors. For example, prior studies have shown that vasoactive agents that alter baseline cerebral blood flow, such as caffeine and carbon dioxide, can significantly alter the amplitude and dynamics of the task-related BOLD response. In this study, we examined the effect of caffeine (200 mg dose) on resting-state BOLD connectivity in the motor cortex across a sample of healthy young subjects (N=9). We found that caffeine significantly (p<0.05) reduced measures of resting-state BOLD connectivity in the motor cortex. Baseline cerebral blood flow and spectral energy in the low-frequency BOLD fluctuations were also significantly decreased by caffeine. These results suggest that caffeine usage should be carefully considered in the design and interpretation of resting-state BOLD fMRI studies.

Quasi-periodic patterns (QPP): large-scale dynamics in resting state fMRI that correlate with local infraslow electrical activity.

PubMed

Thompson, Garth John; Pan, Wen-Ju; Magnuson, Matthew Evan; Jaeger, Dieter; Keilholz, Shella Dawn

2014-01-01

Functional connectivity measurements from resting state blood-oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI) are proving a powerful tool to probe both normal brain function and neuropsychiatric disorders. However, the neural mechanisms that coordinate these large networks are poorly understood, particularly in the context of the growing interest in network dynamics. Recent work in anesthetized rats has shown that the spontaneous BOLD fluctuations are tightly linked to infraslow local field potentials (LFPs) that are seldom recorded but comparable in frequency to the slow BOLD fluctuations. These findings support the hypothesis that long-range coordination involves low frequency neural oscillations and establishes infraslow LFPs as an excellent candidate for probing the neural underpinnings of the BOLD spatiotemporal patterns observed in both rats and humans. To further examine the link between large-scale network dynamics and infraslow LFPs, simultaneous fMRI and microelectrode recording were performed in anesthetized rats. Using an optimized filter to isolate shared components of the signals, we found that time-lagged correlation between infraslow LFPs and BOLD is comparable in spatial extent and timing to a quasi-periodic pattern (QPP) found from BOLD alone, suggesting that fMRI-measured QPPs and the infraslow LFPs share a common mechanism. As fMRI allows spatial resolution and whole brain coverage not available with electroencephalography, QPPs can be used to better understand the role of infraslow oscillations in normal brain function and neurological or psychiatric disorders. © 2013.

Quasi-periodic patterns (QPP): large-scale dynamics in resting state fMRI that correlate with local infraslow electrical activity

PubMed Central

Thompson, Garth John; Pan, Wen-Ju; Magnuson, Matthew Evan; Jaeger, Dieter; Keilholz, Shella Dawn

2013-01-01

Functional connectivity measurements from resting state blood-oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI) are proving a powerful tool to probe both normal brain function and neuropsychiatric disorders. However, the neural mechanisms that coordinate these large networks are poorly understood, particularly in the context of the growing interest in network dynamics. Recent work in anesthetized rats has shown that the spontaneous BOLD fluctuations are tightly linked to infraslow local field potentials (LFPs) that are seldom recorded but comparable in frequency to the slow BOLD fluctuations. These findings support the hypothesis that long-range coordination involves low frequency neural oscillations and establishes infraslow LFPs as an excellent candidate for probing the neural underpinnings of the BOLD spatiotemporal patterns observed in both rats and humans. To further examine the link between large-scale network dynamics and infraslow LFPs, simultaneous fMRI and microelectrode recording were performed in anesthetized rats. Using an optimized filter to isolate shared components of the signals, we found that time-lagged correlation between infraslow LFPs and BOLD is comparable in spatial extent and timing to a quasi-periodic pattern (QPP) found from BOLD alone, suggesting that fMRI-measured QPPs and the infraslow LFPs share a common mechanism. As fMRI allows spatial resolution and whole brain coverage not available with electroencephalography, QPPs can be used to better understand the role of infraslow oscillations in normal brain function and neurological or psychiatric disorders. PMID:24071524

Sex differences in the neural substrates of spatial working memory during adolescence are not mediated by endogenous testosterone.

PubMed

Alarcón, Gabriela; Cservenka, Anita; Fair, Damien A; Nagel, Bonnie J

2014-12-17

Adolescence is a developmental period characterized by notable changes in behavior, physical attributes, and an increase in endogenous sex steroid hormones, which may impact cognitive functioning. Moreover, sex differences in brain structure are present, leading to differences in neural function and cognition. Here, we examine sex differences in performance and blood oxygen level-dependent (BOLD) activation in a sample of adolescents during a spatial working memory (SWM) task. We also examine whether endogenous testosterone levels mediate differential brain activity between the sexes. Adolescents between ages 10 and 16 years completed a SWM functional magnetic resonance imaging (fMRI) task, and serum hormone levels were assessed within seven days of scanning. While there were no sex differences in task performance (accuracy and reaction time), differences in BOLD response between girls and boys emerged, with girls deactivating brain regions in the default mode network and boys showing increased response in SWM-related brain regions of the frontal cortex. These results suggest that adolescent boys and girls adopted distinct neural strategies, while maintaining spatial cognitive strategies that facilitated comparable cognitive performance of a SWM task. A nonparametric bootstrapping procedure revealed that testosterone did not mediate sex-specific brain activity, suggesting that sex differences in BOLD activation during SWM may be better explained by other factors, such as early organizational effects of sex steroids or environmental influences. Elucidating sex differences in neural function and the influence of gonadal hormones can serve as a basis of comparison for understanding sexually dimorphic neurodevelopment and inform sex-specific psychopathology that emerges in adolescence. Copyright © 2014 Elsevier B.V. All rights reserved.

Comparison of block and event-related experimental designs in diffusion-weighted functional MRI.

PubMed

Williams, Rebecca J; McMahon, Katie L; Hocking, Julia; Reutens, David C

2014-08-01

To compare diffusion-weighted functional magnetic resonance imaging (DfMRI), a novel alternative to the blood oxygenation level-dependent (BOLD) contrast, in a functional MRI experiment. Nine participants viewed contrast reversing (7.5 Hz) black-and-white checkerboard stimuli using block and event-related paradigms. DfMRI (b = 1800 mm/s(2)) and BOLD sequences were acquired. Four parameters describing the observed signal were assessed: percent signal change, spatial extent of the activation, the Euclidean distance between peak voxel locations, and the time-to-peak of the best fitting impulse response for different paradigms and sequences. The BOLD conditions showed a higher percent signal change relative to DfMRI; however, event-related DfMRI showed the strongest group activation (t = 21.23, P < 0.0005). Activation was more diffuse and spatially closer to the BOLD response for DfMRI when the block design was used. DfMRIevent showed the shortest TTP (4.4 ± 0.88 sec). The hemodynamic contribution to DfMRI may increase with the use of block designs. © 2013 Wiley Periodicals, Inc.

Stimulated Raman and Brillouin scattering of polarization-smoothed and temporally smoothed laser beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berger, R.L.; Lefebvre, E.; Langdon, A.B.

1999-04-01

Control of filamentation and stimulated Raman and Brillouin scattering is shown to be possible by use of both spatial and temporal smoothing schemes. The spatial smoothing is accomplished by the use of phase plates [Y. Kato and K. Mima, Appl. Phys. {bold 329}, 186 (1982)] and polarization smoothing [Lefebvre {ital et al.}, Phys. Plasmas {bold 5}, 2701 (1998)] in which the plasma is irradiated with two orthogonally polarized, uncorrelated speckle patterns. The temporal smoothing considered here is smoothing by spectral dispersion [Skupsky {ital et al.}, J. Appl. Phys. {bold 66}, 3456 (1989)] in which the speckle pattern changes on themore » laser coherence time scale. At the high instability gains relevant to laser fusion experiments, the effect of smoothing must include the competition among all three instabilities. {copyright} {ital 1999 American Institute of Physics.}« less

Feedback to distal dendrites links fMRI signals to neural receptive fields in a spiking network model of the visual cortex.

PubMed

Heikkinen, Hanna; Sharifian, Fariba; Vigario, Ricardo; Vanni, Simo

2015-07-01

The blood oxygenation level-dependent (BOLD) response has been strongly associated with neuronal activity in the brain. However, some neuronal tuning properties are consistently different from the BOLD response. We studied the spatial extent of neural and hemodynamic responses in the primary visual cortex, where the BOLD responses spread and interact over much longer distances than the small receptive fields of individual neurons would predict. Our model shows that a feedforward-feedback loop between V1 and a higher visual area can account for the observed spread of the BOLD response. In particular, anisotropic landing of inputs to compartmental neurons were necessary to account for the BOLD signal spread, while retaining realistic spiking responses. Our work shows that simple dendrites can separate tuning at the synapses and at the action potential output, thus bridging the BOLD signal to the neural receptive fields with high fidelity. Copyright © 2015 the American Physiological Society.

Spatiotemporal dynamics of the brain at rest--exploring EEG microstates as electrophysiological signatures of BOLD resting state networks.

PubMed

Yuan, Han; Zotev, Vadim; Phillips, Raquel; Drevets, Wayne C; Bodurka, Jerzy

2012-05-01

Neuroimaging research suggests that the resting cerebral physiology is characterized by complex patterns of neuronal activity in widely distributed functional networks. As studied using functional magnetic resonance imaging (fMRI) of the blood-oxygenation-level dependent (BOLD) signal, the resting brain activity is associated with slowly fluctuating hemodynamic signals (~10s). More recently, multimodal functional imaging studies involving simultaneous acquisition of BOLD-fMRI and electroencephalography (EEG) data have suggested that the relatively slow hemodynamic fluctuations of some resting state networks (RSNs) evinced in the BOLD data are related to much faster (~100 ms) transient brain states reflected in EEG signals, that are referred to as "microstates". To further elucidate the relationship between microstates and RSNs, we developed a fully data-driven approach that combines information from simultaneously recorded, high-density EEG and BOLD-fMRI data. Using independent component analysis (ICA) of the combined EEG and fMRI data, we identified thirteen microstates and ten RSNs that are organized independently in their temporal and spatial characteristics, respectively. We hypothesized that the intrinsic brain networks that are active at rest would be reflected in both the EEG data and the fMRI data. To test this hypothesis, the rapid fluctuations associated with each microstate were correlated with the BOLD-fMRI signal associated with each RSN. We found that each RSN was characterized further by a specific electrophysiological signature involving from one to a combination of several microstates. Moreover, by comparing the time course of EEG microstates to that of the whole-brain BOLD signal, on a multi-subject group level, we unraveled for the first time a set of microstate-associated networks that correspond to a range of previously described RSNs, including visual, sensorimotor, auditory, attention, frontal, visceromotor and default mode networks. These results extend our understanding of the electrophysiological signature of BOLD RSNs and demonstrate the intrinsic connection between the fast neuronal activity and slow hemodynamic fluctuations. Copyright © 2012 Elsevier Inc. All rights reserved.

Relationship between BOLD amplitude and pattern classification of orientation-selective activity in the human visual cortex.

PubMed

Tong, Frank; Harrison, Stephenie A; Dewey, John A; Kamitani, Yukiyasu

2012-11-15

Orientation-selective responses can be decoded from fMRI activity patterns in the human visual cortex, using multivariate pattern analysis (MVPA). To what extent do these feature-selective activity patterns depend on the strength and quality of the sensory input, and might the reliability of these activity patterns be predicted by the gross amplitude of the stimulus-driven BOLD response? Observers viewed oriented gratings that varied in luminance contrast (4, 20 or 100%) or spatial frequency (0.25, 1.0 or 4.0 cpd). As predicted, activity patterns in early visual areas led to better discrimination of orientations presented at high than low contrast, with greater effects of contrast found in area V1 than in V3. A second experiment revealed generally better decoding of orientations at low or moderate as compared to high spatial frequencies. Interestingly however, V1 exhibited a relative advantage at discriminating high spatial frequency orientations, consistent with the finer scale of representation in the primary visual cortex. In both experiments, the reliability of these orientation-selective activity patterns was well predicted by the average BOLD amplitude in each region of interest, as indicated by correlation analyses, as well as decoding applied to a simple model of voxel responses to simulated orientation columns. Moreover, individual differences in decoding accuracy could be predicted by the signal-to-noise ratio of an individual's BOLD response. Our results indicate that decoding accuracy can be well predicted by incorporating the amplitude of the BOLD response into simple simulation models of cortical selectivity; such models could prove useful in future applications of fMRI pattern classification. Copyright © 2012 Elsevier Inc. All rights reserved.

Relationship between BOLD amplitude and pattern classification of orientation-selective activity in the human visual cortex

PubMed Central

Tong, Frank; Harrison, Stephenie A.; Dewey, John A.; Kamitani, Yukiyasu

2012-01-01

Orientation-selective responses can be decoded from fMRI activity patterns in the human visual cortex, using multivariate pattern analysis (MVPA). To what extent do these feature-selective activity patterns depend on the strength and quality of the sensory input, and might the reliability of these activity patterns be predicted by the gross amplitude of the stimulus-driven BOLD response? Observers viewed oriented gratings that varied in luminance contrast (4, 20 or 100%) or spatial frequency (0.25, 1.0 or 4.0 cpd). As predicted, activity patterns in early visual areas led to better discrimination of orientations presented at high than low contrast, with greater effects of contrast found in area V1 than in V3. A second experiment revealed generally better decoding of orientations at low or moderate as compared to high spatial frequencies. Interestingly however, V1 exhibited a relative advantage at discriminating high spatial frequency orientations, consistent with the finer scale of representation in the primary visual cortex. In both experiments, the reliability of these orientation-selective activity patterns was well predicted by the average BOLD amplitude in each region of interest, as indicated by correlation analyses, as well as decoding applied to a simple model of voxel responses to simulated orientation columns. Moreover, individual differences in decoding accuracy could be predicted by the signal-to-noise ratio of an individual's BOLD response. Our results indicate that decoding accuracy can be well predicted by incorporating the amplitude of the BOLD response into simple simulation models of cortical selectivity; such models could prove useful in future applications of fMRI pattern classification. PMID:22917989

Ridding fMRI data of motion-related influences: Removal of signals with distinct spatial and physical bases in multiecho data.

PubMed

Power, Jonathan D; Plitt, Mark; Gotts, Stephen J; Kundu, Prantik; Voon, Valerie; Bandettini, Peter A; Martin, Alex

2018-02-27

"Functional connectivity" techniques are commonplace tools for studying brain organization. A critical element of these analyses is to distinguish variance due to neurobiological signals from variance due to nonneurobiological signals. Multiecho fMRI techniques are a promising means for making such distinctions based on signal decay properties. Here, we report that multiecho fMRI techniques enable excellent removal of certain kinds of artifactual variance, namely, spatially focal artifacts due to motion. By removing these artifacts, multiecho techniques reveal frequent, large-amplitude blood oxygen level-dependent (BOLD) signal changes present across all gray matter that are also linked to motion. These whole-brain BOLD signals could reflect widespread neural processes or other processes, such as alterations in blood partial pressure of carbon dioxide (pCO 2 ) due to ventilation changes. By acquiring multiecho data while monitoring breathing, we demonstrate that whole-brain BOLD signals in the resting state are often caused by changes in breathing that co-occur with head motion. These widespread respiratory fMRI signals cannot be isolated from neurobiological signals by multiecho techniques because they occur via the same BOLD mechanism. Respiratory signals must therefore be removed by some other technique to isolate neurobiological covariance in fMRI time series. Several methods for removing global artifacts are demonstrated and compared, and were found to yield fMRI time series essentially free of motion-related influences. These results identify two kinds of motion-associated fMRI variance, with different physical mechanisms and spatial profiles, each of which strongly and differentially influences functional connectivity patterns. Distance-dependent patterns in covariance are nearly entirely attributable to non-BOLD artifacts.

A quantitative comparison of simultaneous BOLD fMRI and NIRS recordings during functional brain activation

NASA Technical Reports Server (NTRS)

Strangman, Gary; Culver, Joseph P.; Thompson, John H.; Boas, David A.; Sutton, J. P. (Principal Investigator)

2002-01-01

Near-infrared spectroscopy (NIRS) has been used to noninvasively monitor adult human brain function in a wide variety of tasks. While rough spatial correspondences with maps generated from functional magnetic resonance imaging (fMRI) have been found in such experiments, the amplitude correspondences between the two recording modalities have not been fully characterized. To do so, we simultaneously acquired NIRS and blood-oxygenation level-dependent (BOLD) fMRI data and compared Delta(1/BOLD) (approximately R(2)(*)) to changes in oxyhemoglobin, deoxyhemoglobin, and total hemoglobin concentrations derived from the NIRS data from subjects performing a simple motor task. We expected the correlation with deoxyhemoglobin to be strongest, due to the causal relation between changes in deoxyhemoglobin concentrations and BOLD signal. Instead we found highly variable correlations, suggesting the need to account for individual subject differences in our NIRS calculations. We argue that the variability resulted from systematic errors associated with each of the signals, including: (1) partial volume errors due to focal concentration changes, (2) wavelength dependence of this partial volume effect, (3) tissue model errors, and (4) possible spatial incongruence between oxy- and deoxyhemoglobin concentration changes. After such effects were accounted for, strong correlations were found between fMRI changes and all optical measures, with oxyhemoglobin providing the strongest correlation. Importantly, this finding held even when including scalp, skull, and inactive brain tissue in the average BOLD signal. This may reflect, at least in part, the superior contrast-to-noise ratio for oxyhemoglobin relative to deoxyhemoglobin (from optical measurements), rather than physiology related to BOLD signal interpretation.

Complex relationship between BOLD-fMRI and electrophysiological signals in different olfactory bulb layers.

PubMed

Li, Bo; Gong, Ling; Wu, Ruiqi; Li, Anan; Xu, Fuqiang

2014-07-15

Blood oxygenation level dependent functional magnetic resonance imaging (BOLD-fMRI), one of the most powerful technologies in neuroscience, measures neural activity indirectly. Therefore, systematic correlation of BOLD signals with other neural activity measurements is critical to understanding and then using the technology. Numerous studies have revealed that the BOLD signal is determined by many factors and is better correlated with local field potentials (LFP) than single/multiple unit firing. The relationship between BOLD and LFP signals under higher spatial resolution is complex and remains unclear. Here, changes of BOLD and LFP signals in the glomerular (GL), mitral cell (MCL), and granular cell layers (GCL) of the olfactory bulb were evoked by odor stimulation and sequentially acquired using high-resolution fMRI and electrode array. The experimental results revealed a rather complex relationship between BOLD and LFP signals. Both signal modalities were increased layer-dependently by odor stimulation, but the orders of signal intensity were significantly different: GL>MCL>GCL and GCL>GL>MCL for BOLD and LFP, respectively. During odor stimulation, the temporal features of LFPs were similar for a given band in different layers, but different for different frequency bands in a given layer. The BOLD and LFP signals in the low gamma frequency band correlated the best. This study provides new evidence for the consistency between structure and function in understanding the neurophysiological basis of BOLD signals, but also reminds that caution must be taken in interpreting of BOLD signals in regard to neural activity. Copyright © 2014 Elsevier Inc. All rights reserved.

The cumulative influence of hyperoxia and hypercapnia on blood oxygenation and R2*

PubMed Central

Faraco, Carlos C; Strother, Megan K; Siero, Jeroen CW; Arteaga, Daniel F; Scott, Allison O; Jordan, Lori C; Donahue, Manus J

2015-01-01

Cerebrovascular reactivity (CVR)-weighted blood-oxygenation-level-dependent magnetic resonance imaging (BOLD-MRI) experiments are frequently used in conjunction with hyperoxia. Owing to complex interactions between hyperoxia and hypercapnia, quantitative effects of these gas mixtures on BOLD responses, blood and tissue R2*, and blood oxygenation are incompletely understood. Here we performed BOLD imaging (3 T; TE/TR=35/2,000 ms; spatial resolution=3 × 3 × 3.5 mm3) in healthy volunteers (n=12; age=29±4.1 years) breathing (i) room air (RA), (ii) normocapnic–hyperoxia (95% O2/5% N2, HO), (iii) hypercapnic–normoxia (5% CO2/21% O2/74% N2, HC-NO), and (iv) hypercapnic–hyperoxia (5% CO2/95% O2, HC-HO). For HC-HO, experiments were performed with separate RA and HO baselines to control for changes in O2. T2-relaxation-under-spin-tagging MRI was used to calculate basal venous oxygenation. Signal changes were quantified and established hemodynamic models were applied to quantify vasoactive blood oxygenation, blood–water R2*, and tissue–water R2*. In the cortex, fractional BOLD changes (stimulus/baseline) were HO/RA=0.011±0.007; HC-NO/RA=0.014±0.004; HC-HO/HO=0.020±0.008; and HC-HO/RA=0.035±0.010; for the measured basal venous oxygenation level of 0.632, this led to venous blood oxygenation levels of 0.660 (HO), 0.665 (HC-NO), and 0.712 (HC-HO). Interleaving a HC-HO stimulus with HO baseline provided a smaller but significantly elevated BOLD response compared with a HC-NO stimulus. Results provide an outline for how blood oxygenation differs for several gas stimuli and provides quantitative information on how hypercapnic BOLD CVR and R2* are altered during hyperoxia. PMID:26174329

Metabolic and vascular origins of the BOLD effect: Implications for imaging pathology and resting-state brain function.

PubMed

Mark, Clarisse I; Mazerolle, Erin L; Chen, J Jean

2015-08-01

The blood oxygenation level-dependent (BOLD) phenomenon has profoundly revolutionized neuroscience, with applications ranging from normal brain development and aging, to brain disorders and diseases. While the BOLD effect represents an invaluable tool to map brain function, it does not measure neural activity directly; rather, it reflects changes in blood oxygenation resulting from the relative balance between cerebral oxygen metabolism (through neural activity) and oxygen supply (through cerebral blood flow and volume). As such, there are cases in which BOLD signals might be dissociated from neural activity, leading to misleading results. The emphasis of this review is to develop a critical perspective for interpreting BOLD results, through a comprehensive consideration of BOLD's metabolic and vascular underpinnings. We demonstrate that such an understanding is especially important under disease or resting conditions. We also describe state-of-the-art acquisition and analytical techniques to reveal physiological information on the mechanisms underlying measured BOLD signals. With these goals in mind, this review is structured to provide a fundamental understanding of: 1) the physiological and physical sources of the BOLD contrast; 2) the extraction of information regarding oxidative metabolism and cerebrovascular reactivity from the BOLD signal, critical to investigating neuropathology; and 3) the fundamental importance of metabolic and vascular mechanisms for interpreting resting-state BOLD measurements. © 2015 Wiley Periodicals, Inc.

Focal BOLD-fMRI changes in bicuculline-induced tonic-clonic seizures in the rat

PubMed Central

DeSalvo, Matthew N.; Schridde, Ulrich; Mishra, Asht M.; Motelow, Joshua E.; Purcaro, Michael J.; Danielson, Nathan; Bai, Xiaoxiao; Hyder, Fahmeed; Blumenfeld, Hal

2010-01-01

Generalized tonic-clonic seizures cause widespread physiological changes throughout the cerebral cortex and subcortical structures in the brain. Using combined blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI) at 9.4 T and electroencephalography (EEG) these changes can be characterized with high spatiotemporal resolution. We studied BOLD changes in anesthetized Wistar rats during bicuculline-induced tonic-clonic seizures. Bicuculline, a GABAA receptor antagonist, was injected systemically and seizure activity was observed on EEG as high amplitude, high-frequency polyspike discharges followed by clonic paroxysmal activity of lower frequency, with mean electrographic seizure duration of 349 s. Our aim was to characterize the spatial localization, direction, and timing of BOLD signal changes during the pre-ictal, ictal and post-ictal periods. Group analysis was performed across seizures using paired t-maps of BOLD signal superimposed on high resolution anatomical images. Regional analysis was then performed using volumes of interest to quantify BOLD timecourses. In the pre-ictal period we found focal BOLD increases in specific areas of somatosensory cortex (S1, S2) and thalamus several seconds before seizure onset. During seizures we observed BOLD increases in cortex, brainstem and thalamus and BOLD decreases in the hippocampus. The largest ictal BOLD increases remained in the focal regions of somatosensory cortex showing pre-ictal increases. During the post-ictal period we observed widespread BOLD decreases. These findings support a model in which “generalized” tonic-clonic seizures begin with focal changes before electrographic seizure onset, which progress to non-uniform changes during seizures, possibly shedding light on the etiology and pathophysiology of similar seizures in humans. PMID:20079442

Distributions of Irritative Zones Are Related to Individual Alterations of Resting-State Networks in Focal Epilepsy

PubMed Central

Song, Yinchen; Sanganahalli, Basavaraju G.; Hyder, Fahmeed; Lin, Wei-Chiang; Riera, Jorge J.

2015-01-01

Alterations in the connectivity patterns of the fMRI-based resting-state networks (RSNs) have been reported in several types of epilepsies. Evidence pointed out these alterations might be associated with the genesis and propagation of interictal epileptiform discharges (IEDs). IEDs also evoke blood-oxygen-level dependent (BOLD) responses, which have been used to delineate irritative zones during preoperative work-up. Therefore, one may expect a relationship between the topology of the IED-evoked BOLD response network and the altered spatial patterns of the RSNs. In this study, we used EEG recordings and fMRI data obtained simultaneously from a chronic model of focal epilepsy in Wistar rats to verify our hypothesis. We found that IED-evoked BOLD response networks comprise both cortical and subcortical structures with a rat-dependent topology. In all rats, IEDs evoke both activation and deactivation types of BOLD responses. Using a Granger causality method, we found that in many cases areas with BOLD deactivation have directed influences on areas with activation (p<0.05). We were able to predict topological properties (i.e., focal/diffused, unilateral/bilateral) of the IED-evoked BOLD response network by performing hierarchical clustering analysis on major spatial features of the RSNs. All these results suggest that IEDs and disruptions in the RSNs found previously in humans may be different manifestations of the same transient events, probably reflecting altered consciousness. In our opinion, the shutdown of specific nodes of the default mode network may cause uncontrollable excitability in other functionally connected brain areas. We conclude that IED-evoked BOLD responses (i.e., activation and deactivation) and alterations of RSNs are intrinsically related, and speculate that an understanding of their interplay is necessary to discriminate focal epileptogenesis and network propagation phenomena across different brain modules via hub-based connectivity. PMID:26226628

Task relevance modulates the cortical representation of feature conjunctions in the target template.

PubMed

Reeder, Reshanne R; Hanke, Michael; Pollmann, Stefan

2017-07-03

Little is known about the cortical regions involved in representing task-related content in preparation for visual task performance. Here we used representational similarity analysis (RSA) to investigate the BOLD response pattern similarity between task relevant and task irrelevant feature dimensions during conjunction viewing and target template maintenance prior to visual search. Subjects were cued to search for a spatial frequency (SF) or orientation of a Gabor grating and we measured BOLD signal during cue and delay periods before the onset of a search display. RSA of delay period activity revealed that widespread regions in frontal, posterior parietal, and occipitotemporal cortices showed general representational differences between task relevant and task irrelevant dimensions (e.g., orientation vs. SF). In contrast, RSA of cue period activity revealed sensory-related representational differences between cue images (regardless of task) at the occipital pole and additionally in the frontal pole. Our data show that task and sensory information are represented differently during viewing and during target template maintenance, and that task relevance modulates the representation of visual information across the cortex.

Spatial and Temporal EEG-fMRI Changes During Preictal and Postictal Phases in a Patient With Posttraumatic Epilepsy.

PubMed

Storti, Silvia F; Del Felice, Alessandra; Formaggio, Emanuela; Boscolo Galazzo, Ilaria; Bongiovanni, Luigi G; Cerini, Roberto; Fiaschi, Antonio; Manganotti, Paolo

2015-07-01

The combined use of electroencephalography (EEG) and functional magnetic resonance imaging (EEG-fMRI) in epilepsy allows the noninvasive hemodynamic characterization of epileptic discharge-related neuronal activations. The aim of this study was to investigate pathophysiologic mechanisms underlying epileptic activity by exploring the spatial and temporal distribution of fMRI signal modifications during seizure in a single patient with posttraumatic epilepsy. EEG and fMRI data were acquired during two scanning sessions: a spontaneous critical episode was observed during the first, and interictal events were recorded during the second. The EEG-fMRI data were analyzed using the general linear model (GLM). Blood oxygenation level-dependent (BOLD) localization derived from the preictal and artifact-free postictal phase was concordant with the BOLD localization of the interictal epileptiform discharges identified in the second session, pointing to a left perilesional mesiofrontal area. Of note, BOLD signal modifications were already visible several seconds before seizure onset. In brief, BOLD activations from the preictal, postictal, and interictal epileptiform discharge analysis appear to be concordant with the clinically driven localization hypothesis, whereas a widespread network of activations is detected during the ictal phase in a partial seizure. © EEG and Clinical Neuroscience Society (ECNS) 2014.

17 CFR 232.307 - Bold face type.

Code of Federal Regulations, 2012 CFR

2012-04-01

... 17 Commodity and Securities Exchanges 2 2012-04-01 2012-04-01 false Bold face type. 232.307 Section 232.307 Commodity and Securities Exchanges SECURITIES AND EXCHANGE COMMISSION REGULATION S-T... face type. (a) Provisions requiring presentation of information in bold face type shall be satisfied in...

17 CFR 232.307 - Bold face type.

Code of Federal Regulations, 2010 CFR

2010-04-01

... 17 Commodity and Securities Exchanges 2 2010-04-01 2010-04-01 false Bold face type. 232.307 Section 232.307 Commodity and Securities Exchanges SECURITIES AND EXCHANGE COMMISSION REGULATION S-T... face type. (a) Provisions requiring presentation of information in bold face type shall be satisfied in...

17 CFR 232.307 - Bold face type.

Code of Federal Regulations, 2014 CFR

2014-04-01

... 17 Commodity and Securities Exchanges 3 2014-04-01 2014-04-01 false Bold face type. 232.307 Section 232.307 Commodity and Securities Exchanges SECURITIES AND EXCHANGE COMMISSION REGULATION S-T... face type. (a) Provisions requiring presentation of information in bold face type shall be satisfied in...

17 CFR 232.307 - Bold face type.

Code of Federal Regulations, 2013 CFR

2013-04-01

... 17 Commodity and Securities Exchanges 2 2013-04-01 2013-04-01 false Bold face type. 232.307 Section 232.307 Commodity and Securities Exchanges SECURITIES AND EXCHANGE COMMISSION REGULATION S-T... face type. (a) Provisions requiring presentation of information in bold face type shall be satisfied in...

17 CFR 232.307 - Bold face type.

Code of Federal Regulations, 2011 CFR

2011-04-01

... 17 Commodity and Securities Exchanges 2 2011-04-01 2011-04-01 false Bold face type. 232.307 Section 232.307 Commodity and Securities Exchanges SECURITIES AND EXCHANGE COMMISSION REGULATION S-T... face type. (a) Provisions requiring presentation of information in bold face type shall be satisfied in...

The effect of boldness on decision-making in barnacle geese is group-size-dependent

PubMed Central

Kurvers, Ralf H. J. M.; Adamczyk, Vena M. A. P.; van Wieren, Sipke E.; Prins, Herbert H. T.

2011-01-01

In group-living species, decisions made by individuals may result in collective behaviours. A central question in understanding collective behaviours is how individual variation in phenotype affects collective behaviours. However, how the personality of individuals affects collective decisions in groups remains poorly understood. Here, we investigated the role of boldness on the decision-making process in different-sized groups of barnacle geese. Naive barnacle geese, differing in boldness score, were introduced in a labyrinth in groups with either one or three informed demonstrators. The demonstrators possessed information about the route through the labyrinth. In pairs, the probability of choosing a route prior to the informed demonstrator increased with increasing boldness score: bolder individuals decided more often for themselves where to go compared with shyer individuals, whereas shyer individuals waited more often for the demonstrators to decide and followed this information. In groups of four individuals, however, there was no effect of boldness on decision-making, suggesting that individual differences were less important with increasing group size. Our experimental results show that personality is important in collective decisions in pairs of barnacle geese, and suggest that bolder individuals have a greater influence over the outcome of decisions in groups. PMID:21123271

The effect of boldness on decision-making in barnacle geese is group-size-dependent.

PubMed

Kurvers, Ralf H J M; Adamczyk, Vena M A P; van Wieren, Sipke E; Prins, Herbert H T

2011-07-07

In group-living species, decisions made by individuals may result in collective behaviours. A central question in understanding collective behaviours is how individual variation in phenotype affects collective behaviours. However, how the personality of individuals affects collective decisions in groups remains poorly understood. Here, we investigated the role of boldness on the decision-making process in different-sized groups of barnacle geese. Naive barnacle geese, differing in boldness score, were introduced in a labyrinth in groups with either one or three informed demonstrators. The demonstrators possessed information about the route through the labyrinth. In pairs, the probability of choosing a route prior to the informed demonstrator increased with increasing boldness score: bolder individuals decided more often for themselves where to go compared with shyer individuals, whereas shyer individuals waited more often for the demonstrators to decide and followed this information. In groups of four individuals, however, there was no effect of boldness on decision-making, suggesting that individual differences were less important with increasing group size. Our experimental results show that personality is important in collective decisions in pairs of barnacle geese, and suggest that bolder individuals have a greater influence over the outcome of decisions in groups.

Top-down regulation of default mode activity in spatial visual attention

PubMed Central

Wen, Xiaotong; Liu, Yijun; Yao, Li; Ding, Mingzhou

2013-01-01

Dorsal anterior cingulate and bilateral anterior insula form a task control network (TCN) whose primary function includes initiating and maintaining task-level cognitive set and exerting top-down regulation of sensorimotor processing. The default mode network (DMN), comprising an anatomically distinct set of cortical areas, mediates introspection and self-referential processes. Resting-state data show that TCN and DMN interact. The functional ramifications of their interaction remain elusive. Recording fMRI data from human subjects performing a visual spatial attention task and correlating Granger causal influences with behavioral performance and blood-oxygen-level-dependent (BOLD) activity we report three main findings. First, causal influences from TCN to DMN, i.e., TCN→DMN, are positively correlated with behavioral performance. Second, causal influences from DMN to TCN, i.e., DMN→TCN, are negatively correlated with behavioral performance. Third, stronger DMN→TCN are associated with less elevated BOLD activity in TCN, whereas the relationship between TCN→DMN and DMN BOLD activity is unsystematic. These results suggest that during visual spatial attention, top-down signals from TCN to DMN regulate the activity in DMN to enhance behavioral performance, whereas signals from DMN to TCN, acting possibly as internal noise, interfere with task control, leading to degraded behavioral performance. PMID:23575842

Comparison of BOLD, diffusion-weighted fMRI and ADC-fMRI for stimulation of the primary visual system with a block paradigm.

PubMed

Nicolas, R; Gros-Dagnac, H; Aubry, F; Celsis, P

2017-06-01

The blood oxygen level-dependent (BOLD) effect is extensively used for functional MRI (fMRI) but presents some limitations. Diffusion-weighted fMRI (DfMRI) has been proposed as a method more tightly linked to neuronal activity. This work proposes a protocol of DfMRI acquired for several b-values and diffusion directions that is compared to gradient-echo BOLD (GE-BOLD) and to repeated spin-echo BOLD (SE-BOLD, acquisitions performed with b=0s/mm 2 ), which was also used to ensure the reproducibility of the response. A block stimulation paradigm of the primary visual system (V1) was performed in 12 healthy subjects with checkerboard alternations (2Hz frequency). DfMRI was performed at 3T with 5 b-values (b=1500, 1000, 500, 250, 0s/mm 2 ) with TR/TE=1004/93ms, Δ/δ=45.4ms/30ms, and 6 spatial directions for diffusion measures. GE-BOLD was performed with a similar block stimulation design timing. Apparent Diffusion Coefficient (ADC)-fMRI was computed with all b-values used. An identical Z-score level was used for all fMRI modalities for the comparison of volumes of activation. ADC-fMRI and SE-BOLD fMRI activation locations were compared in a voxel-based analysis to a cytoarchitectural probability map of V1. SE-BOLD activation volumes represented only 55% of the GE-BOLD activation volumes (P<0.0001). DfMRI activation volumes averaged for all b-values acquired represented only 12% of GE-BOLD (P<0.0001) and only 22% of SE-BOLD activation volumes (P<0.005). Compared to SE-BOLD-fMRI, ADC-fMRI activations showed fewer pixels outside of V1 and a higher average probability of belonging to V1. DfMRI and ADC-fMRI acquisition at 3T could be easily post-processed with common neuro-imaging software. DfMRI and ADC-fMRI activation volumes were significantly smaller than those obtained with SE-BOLD. ADC-fMRI activations were more precisely localized in V1 than those of SE-BOLD-fMRI. This validated the increased capability of ADC-fMRI compared to BOLD to enhance the precision of localizing an fMRI activation in the cyto-architectural zone V1, thereby justifying the use of ADC-fMRI for neuro-scientific studies. Copyright © 2017 Elsevier Inc. All rights reserved.

Evaluation of preprocessing steps to compensate for magnetic field distortions due to body movements in BOLD fMRI

PubMed Central

Barry, Robert L.; Williams, Joy M.; Klassen, L. Martyn; Gallivan, Jason P.; Culham, Jody C.

2009-01-01

Blood-oxygenation-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) is currently the dominant technique for non-invasive investigation of brain functions. One of the challenges with BOLD fMRI, particularly at high fields, is compensation for the effects of spatiotemporally varying magnetic field inhomogeneities (ΔB0) caused by normal subject respiration, and in some studies, movement of the subject during the scan to perform tasks related to the functional paradigm. The presence of ΔB0 during data acquisition distorts reconstructed images and introduces extraneous fluctuations in the fMRI time series that decrease the BOLD contrast-to-noise ratio. Optimization of the fMRI data-processing pipeline to compensate for geometric distortions is of paramount importance to ensure high quality of fMRI data. To investigate ΔB0 caused by subject movement, echo-planar imaging scans were collected with and without concurrent motion of a phantom arm. The phantom arm was constructed and moved by the experimenter to emulate forearm motions while subjects remained still and observed a visual stimulation paradigm. These data were then subjected to eight different combinations of preprocessing steps. The best preprocessing pipeline included navigator correction, a complex phase regressor, and spatial smoothing. The synergy between navigator correction and phase regression reduced geometric distortions better than either step in isolation, and preconditioned the data to make them more amenable to the benefits of spatial smoothing. The combination of these steps provided a 10% increase in t-statistics compared to only navigator correction and spatial smoothing, and reduced the noise and false activations in regions where no legitimate effects would occur. PMID:19695810

Improved sensitivity and specificity for resting state and task fMRI with multiband multi-echo EPI compared to multi-echo EPI at 7 T.

PubMed

Boyacioğlu, Rasim; Schulz, Jenni; Koopmans, Peter J; Barth, Markus; Norris, David G

2015-10-01

A multiband multi-echo (MBME) sequence is implemented and compared to a matched standard multi-echo (ME) protocol to investigate the potential improvement in sensitivity and spatial specificity at 7 T for resting state and task fMRI. ME acquisition is attractive because BOLD sensitivity is less affected by variation in T2*, and because of the potential for separating BOLD and non-BOLD signal components. MBME further reduces TR thus increasing the potential reduction in physiological noise. In this study we used FSL-FIX to clean ME and MBME resting state and task fMRI data (both 3.5mm isotropic). After noise correction, the detection of resting state networks improves with more non-artifactual independent components being observed. Additional activation clusters for task data are discovered for MBME data (increased sensitivity) whereas existing clusters become more localized for resting state (improved spatial specificity). The results obtained indicate that MBME is superior to ME at high field strengths. Copyright © 2015 Elsevier Inc. All rights reserved.

Exploring structure and function of sensory cortex with 7T MRI.

PubMed

Schluppeck, Denis; Sanchez-Panchuelo, Rosa-Maria; Francis, Susan T

2018-01-01

In this paper, we present an overview of 7T magnetic resonance imaging (MRI) studies of the detailed function and anatomy of sensory areas of the human brain. We discuss the motivation for the studies, with particular emphasis on increasing the spatial resolution of functional MRI (fMRI) using reduced field-of-view (FOV) data acquisitions. MRI at ultra-high-field (UHF) - defined here as 7T and above - has several advantages over lower field strengths. The intrinsic signal-to-noise ratio (SNR) of images is higher at UHF, and coupled with the increased blood-oxygen-level-dependent (BOLD) signal change, this results in increased BOLD contrast-to-noise ratio (CNR), which can be exploited to improve spatial resolution or detect weaker signals. Additionally, the BOLD signal from the intra-vascular (IV) compartment is relatively diminished compared to lower field strengths. Together, these properties make 7T functional MRI an attractive proposition for high spatial specificity measures. But with the advantages come some challenges. For example, increased vulnerability to susceptibility-induced geometric distortions and signal loss in EPI acquisitions tend to be much larger. Some of these technical issues can be addressed with currently available tools and will be discussed. We highlight the key methodological considerations for high resolution functional and structural imaging at 7 T. We then present recent data using the high spatial resolution available at UHF in studies of the visual and somatosensory cortex to highlight promising developments in this area. Copyright © 2017 Elsevier Inc. All rights reserved.

Interactions between boldness, foraging performance and behavioural plasticity across social contexts.

PubMed

Ólafsdóttir, Guðbjörg Ásta; Magellan, Kit

2016-01-01

Boldness, the tendency to be explorative, risk prone and proactive, often varies consistently between individuals. An individual's position on the boldness-shyness continuum has many implications. Bold individuals may outperform shyer conspecifics during foraging as they cover more ground, accumulate information more rapidly and make more frequent food discoveries. Individual variation in boldness may also affect behavioural plasticity across environmental contexts, as the time to process new information, the ability to locate and memorise resources and the time and ability to apply prior information in a novel context all differ between individuals. The primary aim of the current study was to examine plasticity in, and covariation between, boldness, foraging speed and foraging accuracy across social foraging contexts. We showed that the stickleback that were shyest when foraging alone became relatively boldest when foraging in a social context and also delayed their entry to a known food patch the most in the presence of conspecifics. These results support the assertion that shyer foragers are more reactive to social cues and add to current knowledge of how an individual's position on the boldness-shyness continuum may correlate to foraging task performance and behavioural plasticity. We conclude that the correlation between boldness and behavioural plasticity may have broad relevance as the ability to adjust or retain behaviours in changing social environments could often have consequences for fitness. Animal personality may affect how much individuals change their behaviour to suit different environments. We studied the link between threespine stickleback personality (boldness or shyness), foraging performance and change in foraging performance when either alone or in the presence of other stickleback. We found that shyer threespine stickleback were more reactive to the presence of other fish when foraging. When observed or joined by other fish, shy stickleback started exploring earlier, but entered a known food patch later, than when alone. Bolder stickleback changed their foraging behaviour much less in the presence of other fish. Our results suggest that how bold or shy individuals are may have important consequences on how well they adjust their foraging behaviour to environmental change.

Computational advances towards linking BOLD and behavior.

PubMed

Serences, John T; Saproo, Sameer

2012-03-01

Traditionally, fMRI studies have focused on analyzing the mean response amplitude within a cortical area. However, the mean response is blind to many important patterns of cortical modulation, which severely limits the formulation and evaluation of linking hypotheses between neural activity, BOLD responses, and behavior. More recently, multivariate pattern classification analysis (MVPA) has been applied to fMRI data to evaluate the information content of spatially distributed activation patterns. This approach has been remarkably successful at detecting the presence of specific information in targeted brain regions, and provides an extremely flexible means of extracting that information without a precise generative model for the underlying neural activity. However, this flexibility comes at a cost: since MVPA relies on pooling information across voxels that are selective for many different stimulus attributes, it is difficult to infer how specific sub-sets of tuned neurons are modulated by an experimental manipulation. In contrast, recently developed encoding models can produce more precise estimates of feature-selective tuning functions, and can support the creation of explicit linking hypotheses between neural activity and behavior. Although these encoding models depend on strong - and often untested - assumptions about the response properties of underlying neural generators, they also provide a unique opportunity to evaluate population-level computational theories of perception and cognition that have previously been difficult to assess using either single-unit recording or conventional neuroimaging techniques. Copyright © 2011. Published by Elsevier Ltd.

Spatial Working Memory Effects in Early Visual Cortex

ERIC Educational Resources Information Center

Munneke, Jaap; Heslenfeld, Dirk J.; Theeuwes, Jan

2010-01-01

The present study investigated how spatial working memory recruits early visual cortex. Participants were required to maintain a location in working memory while changes in blood oxygen level dependent (BOLD) signals were measured during the retention interval in which no visual stimulation was present. We show working memory effects during the…

Can personality predict individual differences in brook trout spatial learning ability?

USGS Publications Warehouse

White, S.L.; Wagner, Tyler; Gowan, C.; Braithwaite, V.A.

2017-01-01

While differences in individual personality are common in animal populations, understanding the ecological significance of variation has not yet been resolved. Evidence suggests that personality may influence learning and memory; a finding that could improve our understanding of the evolutionary processes that produce and maintain intraspecific behavioural heterogeneity. Here, we tested whether boldness, the most studied personality trait in fish, could predict learning ability in brook trout. After quantifying boldness, fish were trained to find a hidden food patch in a maze environment. Stable landmark cues were provided to indicate the location of food and, at the conclusion of training, cues were rearranged to test for learning. There was a negative relationship between boldness and learning as shy fish were increasingly more successful at navigating the maze and locating food during training trials compared to bold fish. In the altered testing environment, only shy fish continued using cues to search for food. Overall, the learning rate of bold fish was found to be lower than that of shy fish for several metrics suggesting that personality could have widespread effects on behaviour. Because learning can increase plasticity to environmental change, these results have significant implications for fish conservation.

Occipital Alpha Activity during Stimulus Processing Gates the Information Flow to Object-Selective Cortex

PubMed Central

Zumer, Johanna M.; Scheeringa, René; Schoffelen, Jan-Mathijs; Norris, David G.; Jensen, Ole

2014-01-01

Given the limited processing capabilities of the sensory system, it is essential that attended information is gated to downstream areas, whereas unattended information is blocked. While it has been proposed that alpha band (8–13 Hz) activity serves to route information to downstream regions by inhibiting neuronal processing in task-irrelevant regions, this hypothesis remains untested. Here we investigate how neuronal oscillations detected by electroencephalography in visual areas during working memory encoding serve to gate information reflected in the simultaneously recorded blood-oxygenation-level-dependent (BOLD) signals recorded by functional magnetic resonance imaging in downstream ventral regions. We used a paradigm in which 16 participants were presented with faces and landscapes in the right and left hemifields; one hemifield was attended and the other unattended. We observed that decreased alpha power contralateral to the attended object predicted the BOLD signal representing the attended object in ventral object-selective regions. Furthermore, increased alpha power ipsilateral to the attended object predicted a decrease in the BOLD signal representing the unattended object. We also found that the BOLD signal in the dorsal attention network inversely correlated with visual alpha power. This is the first demonstration, to our knowledge, that oscillations in the alpha band are implicated in the gating of information from the visual cortex to the ventral stream, as reflected in the representationally specific BOLD signal. This link of sensory alpha to downstream activity provides a neurophysiological substrate for the mechanism of selective attention during stimulus processing, which not only boosts the attended information but also suppresses distraction. Although previous studies have shown a relation between the BOLD signal from the dorsal attention network and the alpha band at rest, we demonstrate such a relation during a visuospatial task, indicating that the dorsal attention network exercises top-down control of visual alpha activity. PMID:25333286

Validation of oxygen extraction fraction measurement by qBOLD technique.

PubMed

He, Xiang; Zhu, Mingming; Yablonskiy, Dmitriy A

2008-10-01

Measurement of brain tissue oxygen extraction fraction (OEF) in both baseline and functionally activated states can provide important information on brain functioning in health and disease. The recently proposed quantitative BOLD (qBOLD) technique is MRI-based and provides a regional in vivo OEF measurement (He and Yablonskiy, MRM 2007, 57:115-126). It is based on a previously developed analytical BOLD model and incorporates prior knowledge about the brain tissue composition including the contributions from grey matter, white matter, cerebrospinal fluid, interstitial fluid and intravascular blood. The qBOLD model also allows for the separation of contributions to the BOLD signal from OEF and the deoxyhemoglobin containing blood volume (DBV). The objective of this study is to validate OEF measurements provided by the qBOLD approach. To this end we use a rat model and compare qBOLD OEF measurements against direct measurements of the blood oxygenation level obtained from venous blood drawn directly from the superior sagittal sinus. The cerebral venous oxygenation level of the rat was manipulated by utilizing different anestheisa methods. The study demonstrates a very good agreement between qBOLD approach and direct measurements. (c) 2008 Wiley-Liss, Inc.

Improved spatial accuracy of functional maps in the rat olfactory bulb using supervised machine learning approach.

PubMed

Murphy, Matthew C; Poplawsky, Alexander J; Vazquez, Alberto L; Chan, Kevin C; Kim, Seong-Gi; Fukuda, Mitsuhiro

2016-08-15

Functional MRI (fMRI) is a popular and important tool for noninvasive mapping of neural activity. As fMRI measures the hemodynamic response, the resulting activation maps do not perfectly reflect the underlying neural activity. The purpose of this work was to design a data-driven model to improve the spatial accuracy of fMRI maps in the rat olfactory bulb. This system is an ideal choice for this investigation since the bulb circuit is well characterized, allowing for an accurate definition of activity patterns in order to train the model. We generated models for both cerebral blood volume weighted (CBVw) and blood oxygen level dependent (BOLD) fMRI data. The results indicate that the spatial accuracy of the activation maps is either significantly improved or at worst not significantly different when using the learned models compared to a conventional general linear model approach, particularly for BOLD images and activity patterns involving deep layers of the bulb. Furthermore, the activation maps computed by CBVw and BOLD data show increased agreement when using the learned models, lending more confidence to their accuracy. The models presented here could have an immediate impact on studies of the olfactory bulb, but perhaps more importantly, demonstrate the potential for similar flexible, data-driven models to improve the quality of activation maps calculated using fMRI data. Copyright © 2016 Elsevier Inc. All rights reserved.

Visual Short-Term Memory Activity in Parietal Lobe Reflects Cognitive Processes beyond Attentional Selection.

PubMed

Sheremata, Summer L; Somers, David C; Shomstein, Sarah

2018-02-07

Visual short-term memory (VSTM) and attention are distinct yet interrelated processes. While both require selection of information across the visual field, memory additionally requires the maintenance of information across time and distraction. VSTM recruits areas within human (male and female) dorsal and ventral parietal cortex that are also implicated in spatial selection; therefore, it is important to determine whether overlapping activation might reflect shared attentional demands. Here, identical stimuli and controlled sustained attention across both tasks were used to ask whether fMRI signal amplitude, functional connectivity, and contralateral visual field bias reflect memory-specific task demands. While attention and VSTM activated similar cortical areas, BOLD amplitude and functional connectivity in parietal cortex differentiated the two tasks. Relative to attention, VSTM increased BOLD amplitude in dorsal parietal cortex and decreased BOLD amplitude in the angular gyrus. Additionally, the tasks differentially modulated parietal functional connectivity. Contrasting VSTM and attention, intraparietal sulcus (IPS) 1-2 were more strongly connected with anterior frontoparietal areas and more weakly connected with posterior regions. This divergence between tasks demonstrates that parietal activation reflects memory-specific functions and consequently modulates functional connectivity across the cortex. In contrast, both tasks demonstrated hemispheric asymmetries for spatial processing, exhibiting a stronger contralateral visual field bias in the left versus the right hemisphere across tasks, suggesting that asymmetries are characteristic of a shared selection process in IPS. These results demonstrate that parietal activity and patterns of functional connectivity distinguish VSTM from more general attention processes, establishing a central role of the parietal cortex in maintaining visual information. SIGNIFICANCE STATEMENT Visual short-term memory (VSTM) and attention are distinct yet interrelated processes. Cognitive mechanisms and neural activity underlying these tasks show a large degree of overlap. To examine whether activity within the posterior parietal cortex (PPC) reflects object maintenance across distraction or sustained attention per se, it is necessary to control for attentional demands inherent in VSTM tasks. We demonstrate that activity in PPC reflects VSTM demands even after controlling for attention; remembering items across distraction modulates relationships between parietal and other areas differently than during periods of sustained attention. Our study fills a gap in the literature by directly comparing and controlling for overlap between visual attention and VSTM tasks. Copyright © 2018 the authors 0270-6474/18/381511-09$15.00/0.

Distinct representations for shifts of spatial attention and changes of reward contingencies in the human brain

PubMed Central

Tosoni, Annalisa; Shulman, Gordon L.; Pope, Anna L. W.; McAvoy, Mark P.; Corbetta, Maurizio

2012-01-01

Success in a dynamically changing world requires both rapid shifts of attention to the location of important objects and the detection of changes in motivational contingencies that may alter future behavior. Here we addressed the relationship between these two processes by measuring the blood-oxygenation-level-dependent (BOLD) signal during a visual search task in which the location and the color of a salient cue respectively indicated where a rewarded target would appear and the monetary gain (large or small) associated with its detection. While cues that either shifted or maintained attention were presented every 4 to 8 seconds, the reward magnitude indicated by the cue changed roughly every 30 seconds, allowing us to distinguish a change in expected reward magnitude from a maintained state of expected reward magnitude. Posterior cingulate cortex was modulated by cues signaling an increase in expected reward magnitude, but not by cues for shifting versus maintaining spatial attention. Dorsal fronto-parietal regions in precuneus and FEF also showed increased BOLD activity for changes in expected reward magnitude from low to high, but in addition showed large independent modulations for shifting versus maintaining attention. In particular, the differential activation for shifting versus maintaining attention was not affected by expected reward magnitude. These results indicate that BOLD activations for shifts of attention and increases in expected reward magnitude are largely separate. Finally, visual cortex showed sustained spatially selective signals that were significantly enhanced when greater reward magnitude was expected, but this reward-related modulation was not observed in spatially selective regions of dorsal fronto-parietal cortex. PMID:22578709

Digital Base Band Converter As Radar Vlbi Backend / Dbbc Kā Ciparošanas Sistēma Radara Vlbi Novērojumiem

NASA Astrophysics Data System (ADS)

Tuccari, G.; Bezrukovs, Vl.; Nechaeva, M.

2012-12-01

A digital base band converter (DBBC) system has been developed by the Istituto di Radioastronomia (Noto, Italy) for increasing the sensitivity of European VLBI Network (EVN) by expanding the full observed bandwidth using numerical methods. The output data rate of this VLBI-backend is raised from 1 to 4 Gbps for each radiotelescope. All operations related to the signal processing (frequency translation, amplification, frequency generation with local oscillators, etc.) are transferred to the digital domain, which allows - in addition to well-known advantages coming from digital technologies - achieving better repeatability, precision, simplicity, etc. The maximum input band of DBBC system is 3.5 GHz, and the instantaneous bandwidth is up to 1 GHz for each radio frequency/intermediate frequency (RF/IF) out of the eight possible. This backend is a highly powerful platform for other radioastronomy applications, and a number of additional so-called personalities have been developed and used. This includes PFB (polyphase filter bank) receivers and Spectra for high resolution spectroscopy. An additional new development with the same aim - to use the DBBC system as a multi-purpose backend - is related to the bi-static radar observations including Radar VLBI. In such observations it is possible to study the population of space debris, with detection of even centimetre class fragments. A powerful transmitter is used to illuminate the sky region to be analyzed, and the echoes coming from known or unknown objects are reflected to one or more groundbased telescopes thus producing a single-dish or interferometric detection. The DBBC Radar VLBI personality is able to realize a high-resolution spectrum analysis, maintaining in the central area the echo signal at the expected frequency including the Doppler shift of frequency. For extremely weak signals a very large integration time is needed, so for this personality different input parameters are provided. The realtime information can then allow exploring easily the desired range of search for unknown or not fully determined orbit objects. These features make Radar VLBI personality most useful in the space debris measurements. DBBC sistēma izstrādāta Noto Radioastronomijas institūtā. Sistēmas galvenaisuzdevums - palielināt visa Eiropas VLBI tīkla jutību - realizēts, palielinotvisas novērojamās joslas platumu un pielietojot ciparu signālu apstrādes metodes.Izejas datu plūsma palielināta no 1 līdz 4 Gbps katram radioteleskopam un visasoperācijas, kas saistītas ar signālu apstrādi (frekvences pārveidošana, pastiprinājums,iekšējie ģeneratori, utt.), realizētas digitālā formā, kas ļauj iegūt nozīmīgusuzlabojumus atkārtojamībā, precizitātē, vienkāršībā, nemaz neminot vispārzināmāspriekšrocības, ko nodrošina digitālo tehnoloģiju izmantošana. Maksimālā ieejassignāla frekvenču josla ir 3.5 GHz, un momentānais joslas platums ir līdz 1 GHz uzkatru no astoņiem iespējamajiem RF/IF kanāliem. Šī datu reģistrācijas sistēma irļoti veiktspējīga platforma ne tikai EVN, bet arī citiem radioastronomijas pielietojumiem,un papildus tiek izstrādāta vesela virkne programmatūras pakotņu, kasvēl vairāk paplašina sistēmas funkcionalitāti. Tas ietver PFB (Polifāzes FiltruBanka) uztvērējus "Spectra”, kas piemēroti augstas izšķirtspējas spektroskopijasvajadzībām. Papildus realizēts jaunas programmatūras risinājums, ar mērķiizmantot DBBC sistēmu kā daudzfunkcionālu datu ciparošanas iekārtu, kasizmantojama bistatiskiem radara novērojumiem, tai skaitā arī radara VLBInovērojumiem. Šāda veida novērojumos tiek pētīta kosmisko atlūzu populācija,nodrošinot iespēju detektēt pat centimetra izmēru objektus. Debess apgabalaapstarošanai tiek izmantots jaudīgs raidītājs, un tiek analizēts atbalss signāls, kasatstarojas no zināmiem vai nezināmiem objektiem un tiek uztverts ar vienu vaivairākiem teleskopiem uz Zemes, tādējādi realizējot vienas antenas vai interferometrisku signāla detektēšanu. DBBC sistēma ar radara VLBI programmatūruspēj realizēt augstas izšķirtspējas spektra analīzi, saglabājot atbalss signālu arsagaidāmo frekvenci centrālajā zonā un ieskaitot nepieciešamās Doplera frekvencesnobīdes korekcijas. Tālāk, izmantojot dažādus ievadparametrus, iespējamspielietot ļoti ilgu integrācijas laiku ārkārtīgi vāju signālu detektēšanai. Izmantojotreālā laika informāciju, turpmāk ir iespējams viegli analizēt nepieciešamo apgabaluun detektēt nezināmus objektus vai objektus ar neprecīzi zināmiem orbītu parametriem.Rakstā izklāstītas paredzamās minētās programmatūras funkcijas un tāsizmantošanas plāni pirmajos novērojumos.

Interpreting BOLD: towards a dialogue between cognitive and cellular neuroscience.

PubMed

Hall, Catherine N; Howarth, Clare; Kurth-Nelson, Zebulun; Mishra, Anusha

2016-10-05

Cognitive neuroscience depends on the use of blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) to probe brain function. Although commonly used as a surrogate measure of neuronal activity, BOLD signals actually reflect changes in brain blood oxygenation. Understanding the mechanisms linking neuronal activity to vascular perfusion is, therefore, critical in interpreting BOLD. Advances in cellular neuroscience demonstrating differences in this neurovascular relationship in different brain regions, conditions or pathologies are often not accounted for when interpreting BOLD. Meanwhile, within cognitive neuroscience, the increasing use of high magnetic field strengths and the development of model-based tasks and analyses have broadened the capability of BOLD signals to inform us about the underlying neuronal activity, but these methods are less well understood by cellular neuroscientists. In 2016, a Royal Society Theo Murphy Meeting brought scientists from the two communities together to discuss these issues. Here, we consolidate the main conclusions arising from that meeting. We discuss areas of consensus about what BOLD fMRI can tell us about underlying neuronal activity, and how advanced modelling techniques have improved our ability to use and interpret BOLD. We also highlight areas of controversy in understanding BOLD and suggest research directions required to resolve these issues.This article is part of the themed issue 'Interpreting BOLD: a dialogue between cognitive and cellular neuroscience'. © 2016 The Author(s).

Attention improves encoding of task-relevant features in the human visual cortex

PubMed Central

Jehee, Janneke F.M.; Brady, Devin K.; Tong, Frank

2011-01-01

When spatial attention is directed towards a particular stimulus, increased activity is commonly observed in corresponding locations of the visual cortex. Does this attentional increase in activity indicate improved processing of all features contained within the attended stimulus, or might spatial attention selectively enhance the features relevant to the observer’s task? We used fMRI decoding methods to measure the strength of orientation-selective activity patterns in the human visual cortex while subjects performed either an orientation or contrast discrimination task, involving one of two laterally presented gratings. Greater overall BOLD activation with spatial attention was observed in areas V1-V4 for both tasks. However, multivariate pattern analysis revealed that orientation-selective responses were enhanced by attention only when orientation was the task-relevant feature, and not when the grating’s contrast had to be attended. In a second experiment, observers discriminated the orientation or color of a specific lateral grating. Here, orientation-selective responses were enhanced in both tasks but color-selective responses were enhanced only when color was task-relevant. In both experiments, task-specific enhancement of feature-selective activity was not confined to the attended stimulus location, but instead spread to other locations in the visual field, suggesting the concurrent involvement of a global feature-based attentional mechanism. These results suggest that attention can be remarkably selective in its ability to enhance particular task-relevant features, and further reveal that increases in overall BOLD amplitude are not necessarily accompanied by improved processing of stimulus information. PMID:21632942

Attention improves encoding of task-relevant features in the human visual cortex.

PubMed

Jehee, Janneke F M; Brady, Devin K; Tong, Frank

2011-06-01

When spatial attention is directed toward a particular stimulus, increased activity is commonly observed in corresponding locations of the visual cortex. Does this attentional increase in activity indicate improved processing of all features contained within the attended stimulus, or might spatial attention selectively enhance the features relevant to the observer's task? We used fMRI decoding methods to measure the strength of orientation-selective activity patterns in the human visual cortex while subjects performed either an orientation or contrast discrimination task, involving one of two laterally presented gratings. Greater overall BOLD activation with spatial attention was observed in visual cortical areas V1-V4 for both tasks. However, multivariate pattern analysis revealed that orientation-selective responses were enhanced by attention only when orientation was the task-relevant feature and not when the contrast of the grating had to be attended. In a second experiment, observers discriminated the orientation or color of a specific lateral grating. Here, orientation-selective responses were enhanced in both tasks, but color-selective responses were enhanced only when color was task relevant. In both experiments, task-specific enhancement of feature-selective activity was not confined to the attended stimulus location but instead spread to other locations in the visual field, suggesting the concurrent involvement of a global feature-based attentional mechanism. These results suggest that attention can be remarkably selective in its ability to enhance particular task-relevant features and further reveal that increases in overall BOLD amplitude are not necessarily accompanied by improved processing of stimulus information.

Blood oxygenation level-dependent (BOLD) contrast magnetic resonance imaging (MRI) for prediction of breast cancer chemotherapy response: a pilot study.

PubMed

Jiang, Lan; Weatherall, Paul T; McColl, Roderick W; Tripathy, Debu; Mason, Ralph P

2013-05-01

To determine whether a simple noninvasive method of assessing tumor oxygenation is feasible in the clinical setting and can provide useful, potentially predictive information. Tumor microcirculation and oxygenation play critical roles in tumor growth and responsiveness to cytotoxic treatment and may provide prognostic indicators for cancer therapy. Deoxyhemoglobin is paramagnetic and can serve as an endogenous contrast agent causing signal loss in echo planar magnetic resonance imaging (MRI) (blood oxygenation level-dependent [BOLD]-MRI). We used BOLD-MRI to provide early evaluation of response to neoadjuvant chemotherapy in patients with locally advanced breast cancer. MRI was performed on 11 patients with biopsy-proven malignancy. MRI exams were scheduled before, during, and after chemotherapy. The BOLD study applied a 6-minute oxygen breathing challenge. Seven patients successfully completed the exams. Before chemotherapy, BOLD contrast enhancement was observed in all tumors, but the patients, who ultimately had complete pathological response, exhibited a significantly higher BOLD response to oxygen breathing. We have successfully implemented an oxygen-breathing challenge BOLD contrast technique as part of the standard breast MRI exam in patients with locally advanced breast cancer. The preliminary observation that a large BOLD response correlated with better treatment response suggests a predictive capability for BOLD MRI. Copyright © 2012 Wiley Periodicals, Inc.

Combination of blood oxygen level–dependent functional magnetic resonance imaging and visual evoked potential recordings for abnormal visual cortex in two types of amblyopia

PubMed Central

Wang, Xinmei; Cui, Dongmei; Zheng, Ling; Yang, Xiao; Yang, Hui

2012-01-01

Purpose To elucidate the different neuromechanisms of subjects with strabismic and anisometropic amblyopia compared with normal vision subjects using blood oxygen level–dependent functional magnetic resonance imaging (BOLD-fMRI) and pattern-reversal visual evoked potential (PR-VEP). Methods Fifty-three subjects, age range seven to 12 years, diagnosed with strabismic amblyopia (17 cases), anisometropic amblyopia (20 cases), and normal vision (16 cases), were examined using the BOLD-fMRI and PR-VEP of UTAS-E3000 techniques. Cortical activation by binocular viewing of reversal checkerboard patterns was examined in terms of the calcarine region of interest (ROI)-based and spatial frequency–dependent analysis. The correlation of cortical activation in fMRI and the P100 amplitude in VEP were analyzed using the SPSS 12.0 software package. Results In the BOLD-fMRI procedure, reduced areas and decreased activation levels were found in Brodmann area (BA) 17 and other extrastriate areas in subjects with amblyopia compared with the normal vision group. In general, the reduced areas mainly resided in the striate visual cortex in subjects with anisometropic amblyopia. In subjects with strabismic amblyopia, a more significant cortical impairment was found in bilateral BA 18 and BA 19 than that in subjects with anisometropic amblyopia. The activation by high-spatial-frequency stimuli was reduced in bilateral BA 18 and 19 as well as BA 17 in subjects with anisometropic amblyopia, whereas the activation was mainly reduced in BA 18 and BA 19 in subjects with strabismic amblyopia. These findings were further confirmed by the ROI-based analysis of BA 17. During spatial frequency–dependent VEP detection, subjects with anisometropic amblyopia had reduced sensitivity for high spatial frequency compared to subjects with strabismic amblyopia. The cortical activation in fMRI with the calcarine ROI-based analysis of BA 17 was significantly correlated with the P100 amplitude in VEP recording. Conclusions This study suggested that different types of amblyopia had different cortical responses and combinations of spatial frequency–dependent BOLD-fMRI with PR-VEP could differentiate among various kinds of amblyopia according to the different cortical responses. This study can supply new methods for amblyopia neurology study. PMID:22539870

Pushing the limits of high-resolution functional MRI using a simple high-density multi-element coil design.

PubMed

Petridou, N; Italiaander, M; van de Bank, B L; Siero, J C W; Luijten, P R; Klomp, D W J

2013-01-01

Recent studies have shown that functional MRI (fMRI) can be sensitive to the laminar and columnar organization of the cortex based on differences in the spatial and temporal characteristics of the blood oxygenation level-dependent (BOLD) signal originating from the macrovasculature and the neuronal-specific microvasculature. Human fMRI studies at this scale of the cortical architecture, however, are very rare because the high spatial/temporal resolution required to explore these properties of the BOLD signal are limited by the signal-to-noise ratio. Here, we show that it is possible to detect BOLD signal changes at an isotropic spatial resolution as high as 0.55 mm at 7 T using a high-density multi-element surface coil with minimal electronics, which allows close proximity to the head. The coil comprises of very small, 1 × 2-cm(2) , elements arranged in four flexible modules of four elements each (16-channel) that can be positioned within 1 mm from the head. As a result of this proximity, tissue losses were five-fold greater than coil losses and sufficient to exclude preamplifier decoupling. When compared with a standard 16-channel head coil, the BOLD sensitivity was approximately 2.2-fold higher for a high spatial/temporal resolution (1 mm isotropic/0.4 s), multi-slice, echo planar acquisition, and approximately three- and six-fold higher for three-dimensional echo planar images acquired with isotropic resolutions of 0.7 and 0.55 mm, respectively. Improvements in parallel imaging performance (geometry factor) were up to around 1.5-fold with increasing acceleration factor, and improvements in fMRI detectability (temporal signal-to-noise ratio) were up to around four-fold depending on the distance to the coil. Although deeper lying structures may not benefit from the design, most fMRI questions pertain to the neocortex which lies within approximately 4 cm from the surface. These results suggest that the resolution of fMRI (at 7 T) can approximate levels that are closer to the spatial/temporal scale of the fundamental functional organization of the human cortex using a simple high-density coil design for high sensitivity. Copyright © 2012 John Wiley & Sons, Ltd.

Typographic coding in lists and bibliographies.

PubMed

Spencer, H; Reynolds, L; Coe, B

1974-09-01

A comparison was made of the effectiveness of ten systems of typographical/spatial coding suitable for use in the presentation of highly structured information such as bibliographic material. With one exception, which requires a bold typeface, the systems tested are all suitable for the preparation of copy on a standard typewriter or an upper and lowercase line printer. Sections of alphabetical author index were typed in each of the ten styles and subjects were asked to look up lists of entries in each style. The most effective system on balance was a two-unit left extension of the first line of each entry.

The influence of spatial resolution and smoothing on the detectability of resting-state and task fMRI.

PubMed

Molloy, Erin K; Meyerand, Mary E; Birn, Rasmus M

2014-02-01

Functional MRI blood oxygen level-dependent (BOLD) signal changes can be subtle, motivating the use of imaging parameters and processing strategies that maximize the temporal signal-to-noise ratio (tSNR) and thus the detection power of neuronal activity-induced fluctuations. Previous studies have shown that acquiring data at higher spatial resolutions results in greater percent BOLD signal changes, and furthermore that spatially smoothing higher resolution fMRI data improves tSNR beyond that of data originally acquired at a lower resolution. However, higher resolution images come at the cost of increased acquisition time, and the number of image volumes also influences detectability. The goal of our study is to determine how the detection power of neuronally induced BOLD fluctuations acquired at higher spatial resolutions and then spatially smoothed compares to data acquired at the lower resolutions with the same imaging duration. The number of time points acquired during a given amount of imaging time is a practical consideration given the limited ability of certain populations to lie still in the MRI scanner. We compare acquisitions at three different in-plane spatial resolutions (3.50×3.50mm(2), 2.33×2.33mm(2), 1.75×1.75mm(2)) in terms of their tSNR, contrast-to-noise ratio, and the power to detect both task-related activation and resting-state functional connectivity. The impact of SENSE acceleration, which speeds up acquisition time increasing the number of images collected, is also evaluated. Our results show that after spatially smoothing the data to the same intrinsic resolution, lower resolution acquisitions have a slightly higher detection power of task-activation in some, but not all, brain areas. There were no significant differences in functional connectivity as a function of resolution after smoothing. Similarly, the reduced tSNR of fMRI data acquired with a SENSE factor of 2 is offset by the greater number of images acquired, resulting in few significant differences in detection power of either functional activation or connectivity after spatial smoothing. © 2013.

Can personality predict individual differences in brook trout spatial learning ability?

PubMed

White, S L; Wagner, T; Gowan, C; Braithwaite, V A

2017-08-01

While differences in individual personality are common in animal populations, understanding the ecological significance of variation has not yet been resolved. Evidence suggests that personality may influence learning and memory; a finding that could improve our understanding of the evolutionary processes that produce and maintain intraspecific behavioural heterogeneity. Here, we tested whether boldness, the most studied personality trait in fish, could predict learning ability in brook trout. After quantifying boldness, fish were trained to find a hidden food patch in a maze environment. Stable landmark cues were provided to indicate the location of food and, at the conclusion of training, cues were rearranged to test for learning. There was a negative relationship between boldness and learning as shy fish were increasingly more successful at navigating the maze and locating food during training trials compared to bold fish. In the altered testing environment, only shy fish continued using cues to search for food. Overall, the learning rate of bold fish was found to be lower than that of shy fish for several metrics suggesting that personality could have widespread effects on behaviour. Because learning can increase plasticity to environmental change, these results have significant implications for fish conservation. Copyright © 2016 Elsevier B.V. All rights reserved.

Predicting the practice effects on the blood oxygenation level-dependent (BOLD) function of fMRI in a symbolic manipulation task

NASA Astrophysics Data System (ADS)

Qin, Yulin; Sohn, Myeong-Ho; Anderson, John R.; Stenger, V. Andrew; Fissell, Kate; Goode, Adam; Carter, Cameron S.

2003-04-01

Based on adaptive control of thought-rational (ACT-R), a cognitive architecture for cognitive modeling, researchers have developed an information-processing model to predict the blood oxygenation level-dependent (BOLD) response of functional MRI in symbol manipulation tasks. As an extension of this research, the current event-related functional MRI study investigates the effect of relatively extensive practice on the activation patterns of related brain regions. The task involved performing transformations on equations in an artificial algebra system. This paper shows that the base-level activation learning in the ACT-R theory can predict the change of the BOLD response in practice in a left prefrontal region reflecting retrieval of information. In contrast, practice has relatively little effect on the form of BOLD response in the parietal region reflecting imagined transformations to the equation or the motor region reflecting manual programming.

Reduced CMRO₂ and cerebrovascular reserve in patients with severe intracranial arterial stenosis: a combined multiparametric qBOLD oxygenation and BOLD fMRI study.

PubMed

Bouvier, Julien; Detante, Olivier; Tahon, Florence; Attye, Arnaud; Perret, Thomas; Chechin, David; Barbieux, Marianne; Boubagra, Kamel; Garambois, Katia; Tropres, Irène; Grand, Sylvie; Barbier, Emmanuel L; Krainik, Alexandre

2015-02-01

Multiparametric quantitative blood oxygenation level dependent (mqBOLD) magnetic resonance Imaging (MRI) approach allows mapping tissular oxygen saturation (StO2 ) and cerebral metabolic rate of oxygen (CMRO2 ). To identify hemodynamic alteration related to severe intracranial arterial stenosis (SIAS), functional MRI of cerebrovascular reserve (CVR BOLD fMRI) to hypercapnia has been proposed. Diffusion imaging suggests chronic low grade ischemia in patients with impaired CVR. The aim of the present study was to evaluate how oxygen parameters (StO2 and CMRO2 ), assessed with mqBOLD approach, correlate with CVR in patients (n = 12) with SIAS and without arterial occlusion. The perfusion (dynamic susceptibility contrast), oxygenation, and CVR were compared. The MRI protocol conducted at 3T lasted approximately 1 h. Regions of interest measures on maps were delineated on segmented gray matter (GM) of middle cerebral artery territories. We have shown that decreased CVR is spatially associated with decreased CMRO2 in GM of patients with SIAS. Further, the degree of ipsilateral CVR reduction was well-correlated with the amplitude of the CMRO2 deficit. The altered CMRO2 suggests the presence of a moderate ischemia explained by both a decrease in perfusion and in CVR. CVR and mqBOLD method may be helpful in the selection of patients with SIAS to advocate for medical therapy or percutaneous transluminal angioplasty-stenting. © 2014 Wiley Periodicals, Inc.

One loop back reaction on power law inflation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abramo, L.R.; Woodard, R.P.

1999-08-01

We consider quantum-mechanical corrections to a homogeneous, isotropic, and spatially flat geometry whose scale factor expands classically as a general power of the comoving time. The effects of both gravitons and the scalar inflaton are computed at one loop using the manifestly causal formalism of Schwinger [J. Math. Phys. {bold 2}, 407 (1961); {ital Particles, Sources and Fields} (Addison, Wesley, Reading, MA, 1970)] with the Feynman rules recently developed by Iliopoulos {ital et al.} [Nucl. Phys. B {bold 534}, 419 (1998)]. We find no significant effect, in marked contrast to the result obtained by Mukhanov and co-workers [Phys. Rev. Lett.more » {bold 78}, 1624 (1998); Phys. Rev. D {bold 56}, 3248 (1997)] for chaotic inflation based on a quadratic potential. By applying the canonical technique of Mukhanov and co-workers to the exponential potentials of power law inflation, we show that the two methods produce the same results, within the approximations employed, for these backgrounds. We therefore conclude that the shape of the inflaton potential can have an enormous impact on the one loop back reaction. {copyright} {ital 1999} {ital The American Physical Society}« less

Uses, misuses, new uses and fundamental limitations of magnetic resonance imaging in cognitive science

PubMed Central

2016-01-01

When blood oxygenation level-dependent (BOLD) contrast functional magnetic resonance imaging (fMRI) was discovered in the early 1990s, it provoked an explosion of interest in exploring human cognition, using brain mapping techniques based on MRI. Standards for data acquisition and analysis were rapidly put in place, in order to assist comparison of results across laboratories. Recently, MRI data acquisition capabilities have improved dramatically, inviting a rethink of strategies for relating functional brain activity at the systems level with its neuronal substrates and functional connections. This paper reviews the established capabilities of BOLD contrast fMRI, the perceived weaknesses of major methods of analysis, and current results that may provide insights into improved brain modelling. These results have inspired the use of in vivo myeloarchitecture for localizing brain activity, individual subject analysis without spatial smoothing and mapping of changes in cerebral blood volume instead of BOLD activation changes. The apparent fundamental limitations of all methods based on nuclear magnetic resonance are also discussed. This article is part of the themed issue ‘Interpreting BOLD: a dialogue between cognitive and cellular neuroscience’. PMID:27574303

Uses, misuses, new uses and fundamental limitations of magnetic resonance imaging in cognitive science.

PubMed

Turner, Robert

2016-10-05

When blood oxygenation level-dependent (BOLD) contrast functional magnetic resonance imaging (fMRI) was discovered in the early 1990s, it provoked an explosion of interest in exploring human cognition, using brain mapping techniques based on MRI. Standards for data acquisition and analysis were rapidly put in place, in order to assist comparison of results across laboratories. Recently, MRI data acquisition capabilities have improved dramatically, inviting a rethink of strategies for relating functional brain activity at the systems level with its neuronal substrates and functional connections. This paper reviews the established capabilities of BOLD contrast fMRI, the perceived weaknesses of major methods of analysis, and current results that may provide insights into improved brain modelling. These results have inspired the use of in vivo myeloarchitecture for localizing brain activity, individual subject analysis without spatial smoothing and mapping of changes in cerebral blood volume instead of BOLD activation changes. The apparent fundamental limitations of all methods based on nuclear magnetic resonance are also discussed.This article is part of the themed issue 'Interpreting BOLD: a dialogue between cognitive and cellular neuroscience'. © 2016 The Authors.

A statistical approach for segregating cognitive task stages from multivariate fMRI BOLD time series.

PubMed

Demanuele, Charmaine; Bähner, Florian; Plichta, Michael M; Kirsch, Peter; Tost, Heike; Meyer-Lindenberg, Andreas; Durstewitz, Daniel

2015-01-01

Multivariate pattern analysis can reveal new information from neuroimaging data to illuminate human cognition and its disturbances. Here, we develop a methodological approach, based on multivariate statistical/machine learning and time series analysis, to discern cognitive processing stages from functional magnetic resonance imaging (fMRI) blood oxygenation level dependent (BOLD) time series. We apply this method to data recorded from a group of healthy adults whilst performing a virtual reality version of the delayed win-shift radial arm maze (RAM) task. This task has been frequently used to study working memory and decision making in rodents. Using linear classifiers and multivariate test statistics in conjunction with time series bootstraps, we show that different cognitive stages of the task, as defined by the experimenter, namely, the encoding/retrieval, choice, reward and delay stages, can be statistically discriminated from the BOLD time series in brain areas relevant for decision making and working memory. Discrimination of these task stages was significantly reduced during poor behavioral performance in dorsolateral prefrontal cortex (DLPFC), but not in the primary visual cortex (V1). Experimenter-defined dissection of time series into class labels based on task structure was confirmed by an unsupervised, bottom-up approach based on Hidden Markov Models. Furthermore, we show that different groupings of recorded time points into cognitive event classes can be used to test hypotheses about the specific cognitive role of a given brain region during task execution. We found that whilst the DLPFC strongly differentiated between task stages associated with different memory loads, but not between different visual-spatial aspects, the reverse was true for V1. Our methodology illustrates how different aspects of cognitive information processing during one and the same task can be separated and attributed to specific brain regions based on information contained in multivariate patterns of voxel activity.

Investigation of BOLD fMRI Resonance Frequency Shifts and Quantitative Susceptibility Changes at 7 T

PubMed Central

Bianciardi, Marta; van Gelderen, Peter; Duyn, Jeff H.

2013-01-01

Although blood oxygenation level dependent (BOLD) functional magnetic resonance imaging (fMRI) experiments of brain activity generally rely on the magnitude of the signal, they also provide frequency information that can be derived from the phase of the signal. However, because of confounding effects of instrumental and physiological origin, BOLD related frequency information is difficult to extract and therefore rarely used. Here, we explored the use of high field (7 T) and dedicated signal processing methods to extract frequency information and use it to quantify and interpret blood oxygenation and blood volume changes. We found that optimized preprocessing improves detection of task-evoked and spontaneous changes in phase signals and resonance frequency shifts over large areas of the cortex with sensitivity comparable to that of magnitude signals. Moreover, our results suggest the feasibility of mapping BOLD quantitative susceptibility changes in at least part of the activated area and its largest draining veins. Comparison with magnitude data suggests that the observed susceptibility changes originate from neuronal activity through induced blood volume and oxygenation changes in pial and intracortical veins. Further, from frequency shifts and susceptibility values, we estimated that, relative to baseline, the fractional oxygen saturation in large vessels increased by 0.02–0.05 during stimulation, which is consistent to previously published estimates. Together, these findings demonstrate that valuable information can be derived from fMRI imaging of BOLD frequency shifts and quantitative susceptibility changes. PMID:23897623

Distinct representations for shifts of spatial attention and changes of reward contingencies in the human brain.

PubMed

Tosoni, Annalisa; Shulman, Gordon L; Pope, Anna L W; McAvoy, Mark P; Corbetta, Maurizio

2013-06-01

Success in a dynamically changing world requires both rapid shifts of attention to the location of important objects and the detection of changes in motivational contingencies that may alter future behavior. Here we addressed the relationship between these two processes by measuring the blood-oxygenation-level-dependent (BOLD) signal during a visual search task in which the location and the color of a salient cue respectively indicated where a rewarded target would appear and the monetary gain (large or small) associated with its detection. While cues that either shifted or maintained attention were presented every 4 to 8 sec, the reward magnitude indicated by the cue changed roughly every 30 sec, allowing us to distinguish a change in expected reward magnitude from a maintained state of expected reward magnitude. Posterior cingulate cortex was modulated by cues signaling an increase in expected reward magnitude, but not by cues for shifting versus maintaining spatial attention. Dorsal fronto-parietal regions in precuneus and frontal eye field (FEF) also showed increased BOLD activity for changes in expected reward magnitude from low to high, but in addition showed large independent modulations for shifting versus maintaining attention. In particular, the differential activation for shifting versus maintaining attention was not affected by expected reward magnitude. These results indicate that BOLD activations for shifts of attention and increases in expected reward magnitude are largely separate. Finally, visual cortex showed sustained spatially selective signals that were significantly enhanced when greater reward magnitude was expected, but this reward-related modulation was not observed in spatially selective regions of dorsal fronto-parietal cortex. Copyright © 2012 Elsevier Ltd. All rights reserved.

Multifaceted brain networks reconfiguration in disorders of consciousness uncovered by co-activation patterns.

PubMed

Di Perri, Carol; Amico, Enrico; Heine, Lizette; Annen, Jitka; Martial, Charlotte; Larroque, Stephen Karl; Soddu, Andrea; Marinazzo, Daniele; Laureys, Steven

2018-01-01

Given that recent research has shown that functional connectivity is not a static phenomenon, we aim to investigate the dynamic properties of the default mode network's (DMN) connectivity in patients with disorders of consciousness. Resting-state fMRI volumes of a convenience sample of 17 patients in unresponsive wakefulness syndrome (UWS) and controls were reduced to a spatiotemporal point process by selecting critical time points in the posterior cingulate cortex (PCC). Spatial clustering was performed on the extracted PCC time frames to obtain 8 different co-activation patterns (CAPs). We investigated spatial connectivity patterns positively and negatively correlated with PCC using both CAPs and standard stationary method. We calculated CAPs occurrences and the total number of frames. Compared to controls, patients showed (i) decreased within-network positive correlations and between-network negative correlations, (ii) emergence of "pathological" within-network negative correlations and between-network positive correlations (better defined with CAPs), and (iii) "pathological" increases in within-network positive correlations and between-network negative correlations (only detectable using CAPs). Patients showed decreased occurrence of DMN-like CAPs (1-2) compared to controls. No between-group differences were observed in the total number of frames CONCLUSION: CAPs reveal at a more fine-grained level the multifaceted spatial connectivity reconfiguration following the DMN disruption in UWS patients, which is more complex than previously thought and suggests alternative anatomical substrates for consciousness. BOLD fluctuations do not seem to differ between patients and controls, suggesting that BOLD response represents an intrinsic feature of the signal, and therefore that spatial configuration is more important for consciousness than BOLD activation itself. Hum Brain Mapp 39:89-103, 2018. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Neural correlates of forward planning in a spatial decision task in humans

PubMed Central

Simon, Dylan Alexander; Daw, Nathaniel D.

2011-01-01

Although reinforcement learning (RL) theories have been influential in characterizing the brain’s mechanisms for reward-guided choice, the predominant temporal difference (TD) algorithm cannot explain many flexible or goal-directed actions that have been demonstrated behaviorally. We investigate such actions by contrasting an RL algorithm that is model-based, in that it relies on learning a map or model of the task and planning within it, to traditional model-free TD learning. To distinguish these approaches in humans, we used fMRI in a continuous spatial navigation task, in which frequent changes to the layout of the maze forced subjects continually to relearn their favored routes, thereby exposing the RL mechanisms employed. We sought evidence for the neural substrates of such mechanisms by comparing choice behavior and BOLD signals to decision variables extracted from simulations of either algorithm. Both choices and value-related BOLD signals in striatum, though most often associated with TD learning, were better explained by the model-based theory. Further, predecessor quantities for the model-based value computation were correlated with BOLD signals in the medial temporal lobe and frontal cortex. These results point to a significant extension of both the computational and anatomical substrates for RL in the brain. PMID:21471389

Electrophysiological correlates of the BOLD signal for EEG-informed fMRI

PubMed Central

Murta, Teresa; Leite, Marco; Carmichael, David W; Figueiredo, Patrícia; Lemieux, Louis

2015-01-01

Electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) are important tools in cognitive and clinical neuroscience. Combined EEG–fMRI has been shown to help to characterise brain networks involved in epileptic activity, as well as in different sensory, motor and cognitive functions. A good understanding of the electrophysiological correlates of the blood oxygen level-dependent (BOLD) signal is necessary to interpret fMRI maps, particularly when obtained in combination with EEG. We review the current understanding of electrophysiological–haemodynamic correlates, during different types of brain activity. We start by describing the basic mechanisms underlying EEG and BOLD signals and proceed by reviewing EEG-informed fMRI studies using fMRI to map specific EEG phenomena over the entire brain (EEG–fMRI mapping), or exploring a range of EEG-derived quantities to determine which best explain colocalised BOLD fluctuations (local EEG–fMRI coupling). While reviewing studies of different forms of brain activity (epileptic and nonepileptic spontaneous activity; cognitive, sensory and motor functions), a significant attention is given to epilepsy because the investigation of its haemodynamic correlates is the most common application of EEG-informed fMRI. Our review is focused on EEG-informed fMRI, an asymmetric approach of data integration. We give special attention to the invasiveness of electrophysiological measurements and the simultaneity of multimodal acquisitions because these methodological aspects determine the nature of the conclusions that can be drawn from EEG-informed fMRI studies. We emphasise the advantages of, and need for, simultaneous intracranial EEG–fMRI studies in humans, which recently became available and hold great potential to improve our understanding of the electrophysiological correlates of BOLD fluctuations. PMID:25277370

Increasing measurement accuracy of age-related BOLD signal change: minimizing vascular contributions by resting-state-fluctuation-of-amplitude scaling.

PubMed

Kannurpatti, Sridhar S; Motes, Michael A; Rypma, Bart; Biswal, Bharat B

2011-07-01

In this report we demonstrate a hemodynamic scaling method with resting-state fluctuation of amplitude (RSFA) in healthy adult younger and older subject groups. We show that RSFA correlated with breath hold (BH) responses throughout the brain in groups of younger and older subjects which RSFA and BH performed comparably in accounting for age-related hemodynamic coupling changes, and yielded more veridical estimates of age-related differences in task-related neural activity. BOLD data from younger and older adults performing motor and cognitive tasks were scaled using RSFA and BH related signal changes. Scaling with RSFA and BH reduced the skew of the BOLD response amplitude distribution in each subject and reduced mean BOLD amplitude and variability in both age groups. Statistically significant differences in intrasubject amplitude variation across regions of activated cortex, and intersubject amplitude variation in regions of activated cortex were observed between younger and older subject groups. Intra- and intersubject variability differences were mitigated after scaling. RSFA, though similar to BH in minimizing skew in the unscaled BOLD amplitude distribution, attenuated the neural activity-related BOLD amplitude significantly less than BH. The amplitude and spatial extent of group activation were lower in the older than in the younger group before and after scaling. After accounting for vascular variability differences through scaling, age-related decreases in activation volume were observed during the motor and cognitive tasks. The results suggest that RSFA-scaled data yield age-related neural activity differences during task performance with negligible effects from non-neural (i.e., vascular) sources. Copyright © 2010 Wiley-Liss, Inc.

Initial Validation for the Estimation of Resting-State fMRI Effective Connectivity by a Generalization of the Correlation Approach.

PubMed

Xu, Nan; Spreng, R Nathan; Doerschuk, Peter C

2017-01-01

Resting-state functional MRI (rs-fMRI) is widely used to noninvasively study human brain networks. Network functional connectivity is often estimated by calculating the timeseries correlation between blood-oxygen-level dependent (BOLD) signal from different regions of interest (ROIs). However, standard correlation cannot characterize the direction of information flow between regions. In this paper, we introduce and test a new concept, prediction correlation, to estimate effective connectivity in functional brain networks from rs-fMRI. In this approach, the correlation between two BOLD signals is replaced by a correlation between one BOLD signal and a prediction of this signal via a causal system driven by another BOLD signal. Three validations are described: (1) Prediction correlation performed well on simulated data where the ground truth was known, and outperformed four other methods. (2) On simulated data designed to display the "common driver" problem, prediction correlation did not introduce false connections between non-interacting driven ROIs. (3) On experimental data, prediction correlation recovered the previously identified network organization of human brain. Prediction correlation scales well to work with hundreds of ROIs, enabling it to assess whole brain interregional connectivity at the single subject level. These results provide an initial validation that prediction correlation can capture the direction of information flow and estimate the duration of extended temporal delays in information flow between regions of interest ROIs based on BOLD signal. This approach not only maintains the high sensitivity to network connectivity provided by the correlation analysis, but also performs well in the estimation of causal information flow in the brain.

Large enhancement of perfusion contribution on fMRI signal

PubMed Central

Wang, Xiao; Zhu, Xiao-Hong; Zhang, Yi; Chen, Wei

2012-01-01

The perfusion contribution to the total functional magnetic resonance imaging (fMRI) signal was investigated using a rat model with mild hypercapnia at 9.4 T, and human subjects with visual stimulation at 4 T. It was found that the total fMRI signal change could be approximated as a linear superposition of ‘true' blood oxygenation level-dependent (BOLD; T2/T2*) effect and the blood flow-related (T1) effect. The latter effect was significantly enhanced by using short repetition time and large radiofrequency pulse flip angle and became comparable to the ‘true' BOLD signal in response to a mild hypercapnia in the rat brain, resulting in an improved contrast-to-noise ratio (CNR). Bipolar diffusion gradients suppressed the intravascular signals but had no significant effect on the flow-related signal. Similar results of enhanced fMRI signal were observed in the human study. The overall results suggest that the observed flow-related signal enhancement is likely originated from perfusion, and this enhancement can improve CNR and the spatial specificity for mapping brain activity and physiology changes. The nature of mixed BOLD and perfusion-related contributions in the total fMRI signal also has implication on BOLD quantification, in particular, the BOLD calibration model commonly used to estimate the change of cerebral metabolic rate of oxygen. PMID:22395206

BOLD magnetic resonance imaging in nephrology

PubMed Central

Hall, Michael E; Jordan, Jennifer H; Juncos, Luis A; Hundley, W Gregory; Hall, John E

2018-01-01

Magnetic resonance (MR) imaging, a non-invasive modality that provides anatomic and physiologic information, is increasingly used for diagnosis of pathophysiologic conditions and for understanding renal physiology in humans. Although functional MR imaging methods were pioneered to investigate the brain, they also offer powerful techniques for investigation of other organ systems such as the kidneys. However, imaging the kidneys provides unique challenges due to potential complications from contrast agents. Therefore, development of non-contrast techniques to study kidney anatomy and physiology is important. Blood oxygen level-dependent (BOLD) MR is a non-contrast imaging technique that provides functional information related to renal tissue oxygenation in various pathophysiologic conditions. Here we discuss technical considerations, clinical uses and future directions for use of BOLD MR as well as complementary MR techniques to better understand renal pathophysiology. Our intent is to summarize kidney BOLD MR applications for the clinician rather than focusing on the complex physical challenges that functional MR imaging encompasses; however, we briefly discuss some of those issues. PMID:29559807

Functional abnormalities in normally appearing athletes following mild traumatic brain injury: a functional MRI study

PubMed Central

Slobounov, Semyon M.; Zhang, K.; Pennell, D.; Ray, W.; Johnson, B.; Sebastianelli, W.

2010-01-01

Memory problems are one of the most common symptoms of sport-related mild traumatic brain injury (MTBI), known as concussion. Surprisingly, little research has examined spatial memory in concussed athletes given its importance in athletic environments. Here, we combine functional magnetic resonance imaging (fMRI) with a virtual reality (VR) paradigm designed to investigate the possibility of residual functional deficits in recently concussed but asymptomatic individuals. Specifically, we report performance of spatial memory navigation tasks in a VR environment and fMRI data in 15 athletes suffering from MTBI and 15 neurologically normal, athletically active age matched controls. No differences in performance were observed between these two groups of subjects in terms of success rate (94 and 92%) and time to complete the spatial memory navigation tasks (mean = 19.5 and 19.7 s). Whole brain analysis revealed that similar brain activation patterns were observed during both encoding and retrieval among the groups. However, concussed athletes showed larger cortical networks with additional increases in activity outside of the shared region of interest (ROI) during encoding. Quantitative analysis of blood oxygen level dependent (BOLD) signal revealed that concussed individuals had a significantly larger cluster size during encoding at parietal cortex, right dorsolateral prefrontal cortex, and right hippocampus. In addition, there was a significantly larger BOLD signal percent change at the right hippocampus. Neither cluster size nor BOLD signal percent change at shared ROIs was different between groups during retrieval. These major findings are discussed with respect to current hypotheses regarding the neural mechanism responsible for alteration of brain functions in a clinical setting. PMID:20039023

Functional quantitative susceptibility mapping (fQSM).

PubMed

Balla, Dávid Z; Sanchez-Panchuelo, Rosa M; Wharton, Samuel J; Hagberg, Gisela E; Scheffler, Klaus; Francis, Susan T; Bowtell, Richard

2014-10-15

Blood oxygenation level dependent (BOLD) functional magnetic resonance imaging (fMRI) is a powerful technique, typically based on the statistical analysis of the magnitude component of the complex time-series. Here, we additionally interrogated the phase data of the fMRI time-series and used quantitative susceptibility mapping (QSM) in order to investigate the potential of functional QSM (fQSM) relative to standard magnitude BOLD fMRI. High spatial resolution data (1mm isotropic) were acquired every 3 seconds using zoomed multi-slice gradient-echo EPI collected at 7 T in single orientation (SO) and multiple orientation (MO) experiments, the latter involving 4 repetitions with the subject's head rotated relative to B0. Statistical parametric maps (SPM) were reconstructed for magnitude, phase and QSM time-series and each was subjected to detailed analysis. Several fQSM pipelines were evaluated and compared based on the relative number of voxels that were coincidentally found to be significant in QSM and magnitude SPMs (common voxels). We found that sensitivity and spatial reliability of fQSM relative to the magnitude data depended strongly on the arbitrary significance threshold defining "activated" voxels in SPMs, and on the efficiency of spatio-temporal filtering of the phase time-series. Sensitivity and spatial reliability depended slightly on whether MO or SO fQSM was performed and on the QSM calculation approach used for SO data. Our results present the potential of fQSM as a quantitative method of mapping BOLD changes. We also critically discuss the technical challenges and issues linked to this intriguing new technique. Copyright © 2014 Elsevier Inc. All rights reserved.

Functional magnetic resonance imaging in chronic ischaemic stroke.

PubMed

Lake, Evelyn M R; Bazzigaluppi, Paolo; Stefanovic, Bojana

2016-10-05

Ischaemic stroke is the leading cause of adult disability worldwide. Effective rehabilitation is hindered by uncertainty surrounding the underlying mechanisms that govern long-term ischaemic injury progression. Despite its potential as a sensitive non-invasive in vivo marker of brain function that may aid in the development of new treatments, blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) has found limited application in the clinical research on chronic stage stroke progression. Stroke affects each of the physiological parameters underlying the BOLD contrast, markedly complicating the interpretation of BOLD fMRI data. This review summarizes current progress on application of BOLD fMRI in the chronic stage of ischaemic injury progression and discusses means by which more information may be gained from such BOLD fMRI measurements. Concomitant measurements of vascular reactivity, neuronal activity and metabolism in preclinical models of stroke are reviewed along with illustrative examples of post-ischaemic evolution in neuronal, glial and vascular function. The realization of the BOLD fMRI potential to propel stroke research is predicated on the carefully designed preclinical research establishing an ischaemia-specific quantitative model of BOLD signal contrast to provide the framework for interpretation of fMRI findings in clinical populations.This article is part of the themed issue 'Interpreting BOLD: a dialogue between cognitive and cellular neuroscience'. © 2016 The Author(s).

Neuronal synchrony and the relation between the blood-oxygen-level dependent response and the local field potential

PubMed Central

Nguyen, Mai; Winawer, Jonathan

2017-01-01

The most widespread measures of human brain activity are the blood-oxygen-level dependent (BOLD) signal and surface field potential. Prior studies report a variety of relationships between these signals. To develop an understanding of how to interpret these signals and the relationship between them, we developed a model of (a) neuronal population responses and (b) transformations from neuronal responses into the functional magnetic resonance imaging (fMRI) BOLD signal and electrocorticographic (ECoG) field potential. Rather than seeking a transformation between the two measures directly, this approach interprets each measure with respect to the underlying neuronal population responses. This model accounts for the relationship between BOLD and ECoG data from human visual cortex in V1, V2, and V3, with the model predictions and data matching in three ways: across stimuli, the BOLD amplitude and ECoG broadband power were positively correlated, the BOLD amplitude and alpha power (8–13 Hz) were negatively correlated, and the BOLD amplitude and narrowband gamma power (30–80 Hz) were uncorrelated. The two measures provide complementary information about human brain activity, and we infer that features of the field potential that are uncorrelated with BOLD arise largely from changes in synchrony, rather than level, of neuronal activity. PMID:28742093

Initial Validation for the Estimation of Resting-State fMRI Effective Connectivity by a Generalization of the Correlation Approach

PubMed Central

Xu, Nan; Spreng, R. Nathan; Doerschuk, Peter C.

2017-01-01

Resting-state functional MRI (rs-fMRI) is widely used to noninvasively study human brain networks. Network functional connectivity is often estimated by calculating the timeseries correlation between blood-oxygen-level dependent (BOLD) signal from different regions of interest (ROIs). However, standard correlation cannot characterize the direction of information flow between regions. In this paper, we introduce and test a new concept, prediction correlation, to estimate effective connectivity in functional brain networks from rs-fMRI. In this approach, the correlation between two BOLD signals is replaced by a correlation between one BOLD signal and a prediction of this signal via a causal system driven by another BOLD signal. Three validations are described: (1) Prediction correlation performed well on simulated data where the ground truth was known, and outperformed four other methods. (2) On simulated data designed to display the “common driver” problem, prediction correlation did not introduce false connections between non-interacting driven ROIs. (3) On experimental data, prediction correlation recovered the previously identified network organization of human brain. Prediction correlation scales well to work with hundreds of ROIs, enabling it to assess whole brain interregional connectivity at the single subject level. These results provide an initial validation that prediction correlation can capture the direction of information flow and estimate the duration of extended temporal delays in information flow between regions of interest ROIs based on BOLD signal. This approach not only maintains the high sensitivity to network connectivity provided by the correlation analysis, but also performs well in the estimation of causal information flow in the brain. PMID:28559793

Increased fMRI Sensitivity at Equal Data Burden Using Averaged Shifted Echo Acquisition

PubMed Central

Witt, Suzanne T.; Warntjes, Marcel; Engström, Maria

2016-01-01

There is growing evidence as to the benefits of collecting BOLD fMRI data with increased sampling rates. However, many of the newly developed acquisition techniques developed to collect BOLD data with ultra-short TRs require hardware, software, and non-standard analytic pipelines that may not be accessible to all researchers. We propose to incorporate the method of shifted echo into a standard multi-slice, gradient echo EPI sequence to achieve a higher sampling rate with a TR of <1 s with acceptable spatial resolution. We further propose to incorporate temporal averaging of consecutively acquired EPI volumes to both ameliorate the reduced temporal signal-to-noise inherent in ultra-fast EPI sequences and reduce the data burden. BOLD data were collected from 11 healthy subjects performing a simple, event-related visual-motor task with four different EPI sequences: (1) reference EPI sequence with TR = 1440 ms, (2) shifted echo EPI sequence with TR = 700 ms, (3) shifted echo EPI sequence with every two consecutively acquired EPI volumes averaged and effective TR = 1400 ms, and (4) shifted echo EPI sequence with every four consecutively acquired EPI volumes averaged and effective TR = 2800 ms. Both the temporally averaged sequences exhibited increased temporal signal-to-noise over the shifted echo EPI sequence. The shifted echo sequence with every two EPI volumes averaged also had significantly increased BOLD signal change compared with the other three sequences, while the shifted echo sequence with every four EPI volumes averaged had significantly decreased BOLD signal change compared with the other three sequences. The results indicated that incorporating the method of shifted echo into a standard multi-slice EPI sequence is a viable method for achieving increased sampling rate for collecting event-related BOLD data. Further, consecutively averaging every two consecutively acquired EPI volumes significantly increased the measured BOLD signal change and the subsequently calculated activation map statistics. PMID:27932947

Increasing measurement accuracy of age-related BOLD signal change: Minimizing vascular contributions by resting-state-fluctuation-of-amplitude scaling

PubMed Central

Kannurpatti, Sridhar S.; Motes, Michael A.; Rypma, Bart; Biswal, Bharat B.

2012-01-01

In this report we demonstrate a hemodynamic scaling method with resting-state fluctuation of amplitude (RSFA) in healthy adult younger and older subject groups. We show that RSFA correlated with breath hold (BH) responses throughout the brain in groups of younger and older subjects, that RSFA and BH performed comparably in accounting for age-related hemodynamic coupling changes, and yielded more veridical estimates of age-related differences in task-related neural activity. BOLD data from younger and older adults performing motor and cognitive tasks were scaled using RSFA and BH related signal changes. Scaling with RSFA and BH reduced the skew of the BOLD response amplitude distribution in each subject and reduced mean BOLD amplitude and variability in both age groups. Statistically significant differences in intra-subject amplitude variation across regions of activated cortex, and inter-subject amplitude variation in regions of activated cortex were observed between younger and older subject groups. Intra- and inter-subject variability differences were mitigated after scaling. RSFA, though similar to BH in minimizing skew in the un-scaled BOLD amplitude distribution, attenuated the neural activity related BOLD amplitude significantly less than BH. The amplitude and spatial extent of group activation were lower in the older than in the younger group prior to and after scaling. After accounting for vascular variability differences through scaling, age-related decreases in activation volume were observed during the motor and cognitive tasks. The results suggest that RSFA-scaled data yield age-related neural activity differences during task performance with negligible effects from non-neural (i.e., vascular) sources. PMID:20665721

Males and females differ in brain activation during cognitive tasks.

PubMed

Bell, Emily C; Willson, Morgan C; Wilman, Alan H; Dave, Sanjay; Silverstone, Peter H

2006-04-01

To examine the effect of gender on regional brain activity, we utilized functional magnetic resonance imaging (fMRI) during a motor task and three cognitive tasks; a word generation task, a spatial attention task, and a working memory task in healthy male (n = 23) and female (n = 10) volunteers. Functional data were examined for group differences both in the number of pixels activated, and the blood-oxygen-level-dependent (BOLD) magnitude during each task. Males had a significantly greater mean activation than females in the working memory task with a greater number of pixels being activated in the right superior parietal gyrus and right inferior occipital gyrus, and a greater BOLD magnitude occurring in the left inferior parietal lobe. However, despite these fMRI changes, there were no significant differences between males and females on cognitive performance of the task. In contrast, in the spatial attention task, men performed better at this task than women, but there were no significant functional differences between the two groups. In the word generation task, there were no external measures of performance, but in the functional measurements, males had a significantly greater mean activation than females, where males had a significantly greater BOLD signal magnitude in the left and right dorsolateral prefrontal cortex, the right inferior parietal lobe, and the cingulate. In neither of the motor tasks (right or left hand) did males and females perform differently. Our fMRI findings during the motor tasks were a greater mean BOLD signal magnitude in males in the right hand motor task, compared to females where males had an increased BOLD signal magnitude in the right inferior parietal gyrus and in the left inferior frontal gyrus. In conclusion, these results demonstrate differential patterns of activation in males and females during a variety of cognitive tasks, even though performance in these tasks may not vary, and also that variability in performance may not be reflected in differences in brain activation. These results suggest that in functional imaging studies in clinical populations it may be sensible to examine each sex independently until this effect is more fully understood.

Prospective MR image alignment between breath-holds: Application to renal BOLD MRI.

PubMed

Kalis, Inge M; Pilutti, David; Krafft, Axel J; Hennig, Jürgen; Bock, Michael

2017-04-01

To present an image registration method for renal blood oxygen level-dependent (BOLD) measurements that enables semiautomatic assessment of parenchymal and medullary R2* changes under a functional challenge. In a series of breath-hold acquisitions, three-dimensional data were acquired initially for prospective image registration of subsequent BOLD measurements. An algorithm for kidney alignment for BOLD renal imaging (KALIBRI) was implemented to detect the positions of the left and right kidney so that the kidneys were acquired in the subsequent BOLD measurement at consistent anatomical locations. Residual in-plane distortions were corrected retrospectively so that semiautomatic dynamic R2* measurements of the renal cortex and medulla become feasible. KALIBRI was tested in six healthy volunteers during a series of BOLD experiments, which included a 600- to 1000-mL water challenge. Prospective image registration and BOLD imaging of each kidney was achieved within a total measurement time of about 17 s, enabling its execution within a single breath-hold. KALIBRI improved the registration by up to 35% as found with mutual information measures. In four volunteers, a medullary R2* decrease of up to 40% was observed after water ingestion. KALIBRI improves the quality of two-dimensional time-resolved renal BOLD MRI by aligning local renal anatomy, which allows for consistent R2* measurements over many breath-holds. Magn Reson Med 77:1573-1582, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

Frequency-Selective Attention in Auditory Scenes Recruits Frequency Representations Throughout Human Superior Temporal Cortex.

PubMed

Riecke, Lars; Peters, Judith C; Valente, Giancarlo; Kemper, Valentin G; Formisano, Elia; Sorger, Bettina

2017-05-01

A sound of interest may be tracked amid other salient sounds by focusing attention on its characteristic features including its frequency. Functional magnetic resonance imaging findings have indicated that frequency representations in human primary auditory cortex (AC) contribute to this feat. However, attentional modulations were examined at relatively low spatial and spectral resolutions, and frequency-selective contributions outside the primary AC could not be established. To address these issues, we compared blood oxygenation level-dependent (BOLD) responses in the superior temporal cortex of human listeners while they identified single frequencies versus listened selectively for various frequencies within a multifrequency scene. Using best-frequency mapping, we observed that the detailed spatial layout of attention-induced BOLD response enhancements in primary AC follows the tonotopy of stimulus-driven frequency representations-analogous to the "spotlight" of attention enhancing visuospatial representations in retinotopic visual cortex. Moreover, using an algorithm trained to discriminate stimulus-driven frequency representations, we could successfully decode the focus of frequency-selective attention from listeners' BOLD response patterns in nonprimary AC. Our results indicate that the human brain facilitates selective listening to a frequency of interest in a scene by reinforcing the fine-grained activity pattern throughout the entire superior temporal cortex that would be evoked if that frequency was present alone. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Altered intraoperative cerebrovascular reactivity in brain areas of high-grade glioma recurrence.

PubMed

Fierstra, Jorn; van Niftrik, Bas; Piccirelli, Marco; Burkhardt, Jan Karl; Pangalu, Athina; Kocian, Roman; Valavanis, Antonios; Weller, Michael; Regli, Luca; Bozinov, Oliver

2016-07-01

Current MRI sequences are limited in identifying brain areas at risk for high grade glioma recurrence. We employed intraoperative 3-Tesla functional MRI to assess cerebrovascular reactivity (CVR) after high-grade glioma resection and analyzed regional CVR responses in areas of tumor recurrence on clinical follow-up imaging. Five subjects with high-grade glioma that underwent an intraoperative Blood Oxygen-Level Dependent (BOLD) MRI CVR examination and had a clinical follow-up of at least 18months were selected from a prospective database. For this study, location of tumor recurrence was spatially matched to the intraoperative imaging to assess CVR response in that particular area. CVR is defined as the percent BOLD signal change during repeated cycles of apnea. Of the 5 subjects (mean age 44, 2 females), 4 were diagnosed with a WHO grade III and 1 subject with a WHO grade IV glioma. Three subjects exhibited a tumor recurrence on clinical follow-up MRI (mean: 15months). BOLD CVR measured in the spatially matched area of tumor recurrence was on average 94% increased (range-32% to 183%) as compared to contralateral hemisphere CVR response, 1.50±0.81 versus 1.03±0.46 respectively (p=0.31). For this first analysis in a small cohort, we found altered intraoperative CVR in brain areas exhibiting high grade glioma recurrence on clinical follow-up imaging. Copyright © 2016 Elsevier Inc. All rights reserved.

Streamlining the use of BOLD specimen data to record species distributions: a case study with ten Nearctic species of Microgastrinae (Hymenoptera: Braconidae)

PubMed Central

Penev, Lyubomir; Ratnasingham, Sujeevan; Smith, M. Alex; Sones, Jayme; Telfer, Angela; deWaard, Jeremy R.; Hebert, Paul D. N.

2014-01-01

Abstract The Barcode of Life Data Systems (BOLD) is designed to support the generation and application of DNA barcode data, but it also provides a unique source of data with potential for many research uses. This paper explores the streamlining of BOLD specimen data to record species distributions – and its fast publication using the Biodiversity Data Journal (BDJ), and its authoring platform, the Pensoft Writing Tool (PWT). We selected a sample of 630 specimens and 10 species of a highly diverse group of parasitoid wasps (Hymenoptera: Braconidae, Microgastrinae) from the Nearctic region and used the information in BOLD to uncover a significant number of new records (of locality, provinces, territories and states). By converting specimen information (such as locality, collection date, collector, voucher depository) from the BOLD platform to the Excel template provided by the PWT, it is possible to quickly upload and generate long lists of "Material Examined" for papers discussing taxonomy, ecology and/or new distribution records of species. For the vast majority of publications including DNA barcodes, the generation and publication of ancillary data associated with the barcoded material is seldom highlighted and often disregarded, and the analysis of those data sets to uncover new distribution patterns of species has rarely been explored, even though many BOLD records represent new and/or significant discoveries. The introduction of journals specializing in – and streamlining – the release of these datasets, such as the BDJ, should facilitate thorough analysis of these records, as shown in this paper. PMID:25473326

Improving temporal resolution in fMRI using a 3D spiral acquisition and low rank plus sparse (L+S) reconstruction.

PubMed

Petrov, Andrii Y; Herbst, Michael; Andrew Stenger, V

2017-08-15

Rapid whole-brain dynamic Magnetic Resonance Imaging (MRI) is of particular interest in Blood Oxygen Level Dependent (BOLD) functional MRI (fMRI). Faster acquisitions with higher temporal sampling of the BOLD time-course provide several advantages including increased sensitivity in detecting functional activation, the possibility of filtering out physiological noise for improving temporal SNR, and freezing out head motion. Generally, faster acquisitions require undersampling of the data which results in aliasing artifacts in the object domain. A recently developed low-rank (L) plus sparse (S) matrix decomposition model (L+S) is one of the methods that has been introduced to reconstruct images from undersampled dynamic MRI data. The L+S approach assumes that the dynamic MRI data, represented as a space-time matrix M, is a linear superposition of L and S components, where L represents highly spatially and temporally correlated elements, such as the image background, while S captures dynamic information that is sparse in an appropriate transform domain. This suggests that L+S might be suited for undersampled task or slow event-related fMRI acquisitions because the periodic nature of the BOLD signal is sparse in the temporal Fourier transform domain and slowly varying low-rank brain background signals, such as physiological noise and drift, will be predominantly low-rank. In this work, as a proof of concept, we exploit the L+S method for accelerating block-design fMRI using a 3D stack of spirals (SoS) acquisition where undersampling is performed in the k z -t domain. We examined the feasibility of the L+S method to accurately separate temporally correlated brain background information in the L component while capturing periodic BOLD signals in the S component. We present results acquired in control human volunteers at 3T for both retrospective and prospectively acquired fMRI data for a visual activation block-design task. We show that a SoS fMRI acquisition with an acceleration of four and L+S reconstruction can achieve a brain coverage of 40 slices at 2mm isotropic resolution and 64 x 64 matrix size every 500ms. Copyright © 2017 Elsevier Inc. All rights reserved.

Decoding the encoding of functional brain networks: An fMRI classification comparison of non-negative matrix factorization (NMF), independent component analysis (ICA), and sparse coding algorithms.

PubMed

Xie, Jianwen; Douglas, Pamela K; Wu, Ying Nian; Brody, Arthur L; Anderson, Ariana E

2017-04-15

Brain networks in fMRI are typically identified using spatial independent component analysis (ICA), yet other mathematical constraints provide alternate biologically-plausible frameworks for generating brain networks. Non-negative matrix factorization (NMF) would suppress negative BOLD signal by enforcing positivity. Spatial sparse coding algorithms (L1 Regularized Learning and K-SVD) would impose local specialization and a discouragement of multitasking, where the total observed activity in a single voxel originates from a restricted number of possible brain networks. The assumptions of independence, positivity, and sparsity to encode task-related brain networks are compared; the resulting brain networks within scan for different constraints are used as basis functions to encode observed functional activity. These encodings are then decoded using machine learning, by using the time series weights to predict within scan whether a subject is viewing a video, listening to an audio cue, or at rest, in 304 fMRI scans from 51 subjects. The sparse coding algorithm of L1 Regularized Learning outperformed 4 variations of ICA (p<0.001) for predicting the task being performed within each scan using artifact-cleaned components. The NMF algorithms, which suppressed negative BOLD signal, had the poorest accuracy compared to the ICA and sparse coding algorithms. Holding constant the effect of the extraction algorithm, encodings using sparser spatial networks (containing more zero-valued voxels) had higher classification accuracy (p<0.001). Lower classification accuracy occurred when the extracted spatial maps contained more CSF regions (p<0.001). The success of sparse coding algorithms suggests that algorithms which enforce sparsity, discourage multitasking, and promote local specialization may capture better the underlying source processes than those which allow inexhaustible local processes such as ICA. Negative BOLD signal may capture task-related activations. Copyright © 2017 Elsevier B.V. All rights reserved.

Spatial working memory impairment in primary onset middle-age type 2 diabetes mellitus: An ethology and BOLD-fMRI study.

PubMed

Huang, Ran-Ran; Jia, Bao-Hui; Xie, Lei; Ma, Shu-Hua; Yin, Jing-Jing; Sun, Zong-Bo; Le, Hong-Bo; Xu, Wen-Can; Huang, Jin-Zhuang; Luo, Dong-Xue

2016-01-01

To explore mild cognitive dysfunction and/or spatial working memory impairment in patients with primary onset middle-age type 2 diabetes mellitus (T2DM] using ethology (behavior tests) and blood oxygen level-dependent functional magnetic resonance imaging (BOLD-fMRI). Eighteen primary onset T2DM patients and 18 matched subjects with normal blood glucose levels were all tested using the Montreal cognitive assessment scale test, the Wechsler Memory Scale Chinese-revised test, and scanned using BOLD-fMRI (1.5T, EPI sequence) while performing the n-back task to find the activation intensity of some cognition-related areas. The ethology results showed that T2DM patients had a mild cognitive impairment and memory dysfunction (P < 0.05). The fMRI scan identified a neural network consisting of bilateral dorsolateral prefrontal cortex (DLPFC), bilateral premotor area (PreMA), bilateral parietal lobe (PA), and anterior cingulate cortex (ACC) / supplementary motor area (SMA) that was activated during the n-back task, with right hemisphere dominance. However, only the right PA and ACC/SMA showed a load effect via quantitative analysis in the T2DM group; the activation intensity of most working memory-related brain areas for the T2DM group were lower than for the control group under three memory loads. Furthermore, we found that the activation intensity of some cognition-related areas, including the right insular lobe, left caudate nucleus, and bilateral hippocampus/parahippocampal gyrus were lower than the control group under the memory loads. Diabetes-related brain damage of primary onset middle-age T2DM patients with right DLPFC-posterior parietal lobe and parahippocampal gyrus default network causes impairment of spatial working memory and mild cognitive dysfunction. © 2015 Wiley Periodicals, Inc.

Spatial heterogeneity of the relation between resting-state connectivity and blood flow: an important consideration for pharmacological studies.

PubMed

Khalili-Mahani, Najmeh; van Osch, Matthias J; de Rooij, Mark; Beckmann, Christian F; van Buchem, Mark A; Dahan, Albert; van Gerven, Johannes M; Rombouts, Serge A R B

2014-03-01

Resting state fMRI (RSfMRI) and arterial spin labeling (ASL) provide the field of pharmacological Neuroimaging tool for investigating states of brain activity in terms of functional connectivity or cerebral blood flow (CBF). Functional connectivity reflects the degree of synchrony or correlation of spontaneous fluctuations--mostly in the blood oxygen level dependent (BOLD) signal--across brain networks; but CBF reflects mean delivery of arterial blood to the brain tissue over time. The BOLD and CBF signals are linked to common neurovascular and hemodynamic mechanisms that necessitate increased oxygen transportation to the site of neuronal activation; however, the scale and the sources of variation in static CBF and spatiotemporal BOLD correlations are likely different. We tested this hypothesis by examining the relation between CBF and resting-state-network consistency (RSNC)--representing average intranetwork connectivity, determined from dual regression analysis with eight standard networks of interest (NOIs)--in a crossover placebo-controlled study of morphine and alcohol. Overall, we observed spatially heterogeneous relations between RSNC and CBF, and between the experimental factors (drug-by-time, time, drug and physiological rates) and each of these metrics. The drug-by-time effects on CBF were significant in all networks, but significant RSNC changes were limited to the sensorimotor, the executive/salience and the working memory networks. The post-hoc voxel-wise statistics revealed similar dissociations, perhaps suggesting differential sensitivity of RSNC and CBF to neuronal and vascular endpoints of drug actions. The spatial heterogeneity of RSNC/CBF relations encourages further investigation into the role of neuroreceptor distribution and cerebrovascular anatomy in predicting spontaneous fluctuations under drugs. Copyright © 2012 Wiley Periodicals, Inc.

Crosslinking EEG time-frequency decomposition and fMRI in error monitoring.

PubMed

Hoffmann, Sven; Labrenz, Franziska; Themann, Maria; Wascher, Edmund; Beste, Christian

2014-03-01

Recent studies implicate a common response monitoring system, being active during erroneous and correct responses. Converging evidence from time-frequency decompositions of the response-related ERP revealed that evoked theta activity at fronto-central electrode positions differentiates correct from erroneous responses in simple tasks, but also in more complex tasks. However, up to now it is unclear how different electrophysiological parameters of error processing, especially at the level of neural oscillations are related, or predictive for BOLD signal changes reflecting error processing at a functional-neuroanatomical level. The present study aims to provide crosslinks between time domain information, time-frequency information, MRI BOLD signal and behavioral parameters in a task examining error monitoring due to mistakes in a mental rotation task. The results show that BOLD signal changes reflecting error processing on a functional-neuroanatomical level are best predicted by evoked oscillations in the theta frequency band. Although the fMRI results in this study account for an involvement of the anterior cingulate cortex, middle frontal gyrus, and the Insula in error processing, the correlation of evoked oscillations and BOLD signal was restricted to a coupling of evoked theta and anterior cingulate cortex BOLD activity. The current results indicate that although there is a distributed functional-neuroanatomical network mediating error processing, only distinct parts of this network seem to modulate electrophysiological properties of error monitoring.

Direct estimation of evoked hemoglobin changes by multimodality fusion imaging

PubMed Central

Huppert, Theodore J.; Diamond, Solomon G.; Boas, David A.

2009-01-01

In the last two decades, both diffuse optical tomography (DOT) and blood oxygen level dependent (BOLD)-based functional magnetic resonance imaging (fMRI) methods have been developed as noninvasive tools for imaging evoked cerebral hemodynamic changes in studies of brain activity. Although these two technologies measure functional contrast from similar physiological sources, i.e., changes in hemoglobin levels, these two modalities are based on distinct physical and biophysical principles leading to both limitations and strengths to each method. In this work, we describe a unified linear model to combine the complimentary spatial, temporal, and spectroscopic resolutions of concurrently measured optical tomography and fMRI signals. Using numerical simulations, we demonstrate that concurrent optical and BOLD measurements can be used to create cross-calibrated estimates of absolute micromolar deoxyhemoglobin changes. We apply this new analysis tool to experimental data acquired simultaneously with both DOT and BOLD imaging during a motor task, demonstrate the ability to more robustly estimate hemoglobin changes in comparison to DOT alone, and show how this approach can provide cross-calibrated estimates of hemoglobin changes. Using this multimodal method, we estimate the calibration of the 3 tesla BOLD signal to be −0.55% ± 0.40% signal change per micromolar change of deoxyhemoglobin. PMID:19021411

Agroforestry, climate change, and food security

USDA-ARS?s Scientific Manuscript database

Successfully addressing global climate change effects on agriculture will require a holistic, sustained approach incorporating a suite of strategies at multiple spatial scales and time horizons. In the USA of the 1930’s, bold and innovative leadership at high levels of government was needed to enact...

Dependence of chromatic responses in V1 on visual field eccentricity and spatial frequency: an fMRI study.

PubMed

D'Souza, Dany V; Auer, Tibor; Frahm, Jens; Strasburger, Hans; Lee, Barry B

2016-03-01

Psychophysical sensitivity to red-green chromatic modulation decreases with visual eccentricity, compared to sensitivity to luminance modulation, even after appropriate stimulus scaling. This is likely to occur at a central, rather than a retinal, site. Blood-oxygenation-level-dependent (BOLD) functional magnetic resonance imaging (fMRI) responses to stimuli designed to separately stimulate different afferent channels' [red-green, luminance, and short-wavelength (S)-cone] circular gratings were recorded as a function of visual eccentricity (±10  deg) and spatial frequency (SF) in human primary visual cortex (V1) and further visual areas (V2v, V3v). In V1, the SF tuning of BOLD fMRI responses became coarser with eccentricity. For red-green and luminance gratings, similar SF tuning curves were found at all eccentricities. The pattern for S-cone modulation differed, with SF tuning changing more slowly with eccentricity than for the other two modalities. This may be due to the different retinal distribution with eccentricity of this receptor type. A similar pattern held in V2v and V3v. This would suggest that transformation or spatial filtering of the chromatic (red-green) signal occurs beyond these areas.

Abnormal medial temporal activity for bound information during working memory maintenance in patients with schizophrenia.

PubMed

Luck, David; Danion, Jean-Marie; Marrer, Corrine; Pham, Bich-Tuy; Gounot, Daniel; Foucher, Jack

2010-08-01

Alterations of binding in long-term memory in schizophrenia are well established and occur as a result of aberrant activity in the medial temporal lobe (MTL). In working memory (WM), such a deficit is less clear and the pathophysiological bases remain unstudied. Seventeen patients with schizophrenia and 17 matched healthy controls performed a WM binding task while undergoing functional magnetic resonance imaging. Binding was assessed by contrasting two conditions comprising an equal amount of verbal and spatial information (i.e., three letters and three spatial locations), but differing in the absence or presence of a link between them. In healthy controls, MTL activation was observed for encoding and maintenance of bound information but not for its retrieval. Between-group comparisons revealed that patients with schizophrenia showed MTL hypoactivation during the maintenance phase only. In addition, BOLD signals correlated with behavioral performance in controls but not in patients with schizophrenia. Our results confirm the major role that the MTL plays in the pathophysiology of schizophrenia. Short-term and long-term relational memory deficits in schizophrenia may share common cognitive and functional pathological bases. Our results provide additional information about the episodic buffer that represents an integrative interface between WM and long-term memory. Copyright 2009 Wiley-Liss, Inc.

Role of Ongoing, Intrinsic Activity of Neuronal Populations for Quantitative Neuroimaging of Functional Magnetic Resonance Imaging–Based Networks

PubMed Central

Herman, Peter; Sanganahalli, Basavaraju G.; Coman, Daniel; Blumenfeld, Hal; Rothman, Douglas L.

2011-01-01

Abstract A primary objective in neuroscience is to determine how neuronal populations process information within networks. In humans and animal models, functional magnetic resonance imaging (fMRI) is gaining increasing popularity for network mapping. Although neuroimaging with fMRI—conducted with or without tasks—is actively discovering new brain networks, current fMRI data analysis schemes disregard the importance of the total neuronal activity in a region. In task fMRI experiments, the baseline is differenced away to disclose areas of small evoked changes in the blood oxygenation level-dependent (BOLD) signal. In resting-state fMRI experiments, the spotlight is on regions revealed by correlations of tiny fluctuations in the baseline (or spontaneous) BOLD signal. Interpretation of fMRI-based networks is obscured further, because the BOLD signal indirectly reflects neuronal activity, and difference/correlation maps are thresholded. Since the small changes of BOLD signal typically observed in cognitive fMRI experiments represent a minimal fraction of the total energy/activity in a given area, the relevance of fMRI-based networks is uncertain, because the majority of neuronal energy/activity is ignored. Thus, another alternative for quantitative neuroimaging of fMRI-based networks is a perspective in which the activity of a neuronal population is accounted for by the demanded oxidative energy (CMRO2). In this article, we argue that network mapping can be improved by including neuronal energy/activity of both the information about baseline and small differences/fluctuations of BOLD signal. Thus, total energy/activity information can be obtained through use of calibrated fMRI to quantify differences of ΔCMRO2 and through resting-state positron emission tomography/magnetic resonance spectroscopy measurements for average CMRO2. PMID:22433047

A Comparison of Product Realization Frameworks

DTIC Science & Technology

1993-10-01

software (integrated FrameMaker ). Also included are BOLD for on-line documentation delivery, printer/plotter support, and 18 network licensing support. AMPLE...are built with DSS. Documentation tools include an on-line information system (BOLD), text editing (Notepad), word processing (integrated FrameMaker ...within an application. FrameMaker is fully integrated with the Falcon Framework to provide consistent documentation capabilities within engineering

Comparison of CO2 in air versus carbogen for the measurement of cerebrovascular reactivity with magnetic resonance imaging.

PubMed

Hare, Hannah V; Germuska, Michael; Kelly, Michael E; Bulte, Daniel P

2013-11-01

Measurement of cerebrovascular reactivity (CVR) can give valuable information about existing pathology and the risk of adverse events, such as stroke. A common method of obtaining regional CVR values is by measuring the blood flow response to carbon dioxide (CO2)-enriched air using arterial spin labeling (ASL) or blood oxygen level-dependent (BOLD) imaging. Recently, several studies have used carbogen gas (containing only CO2 and oxygen) as an alternative stimulus. A direct comparison was performed between CVR values acquired by ASL and BOLD imaging using stimuli of (1) 5% CO2 in air and (2) 5% CO2 in oxygen (carbogen-5). Although BOLD and ASL CVR values are shown to be correlated for CO2 in air (mean response 0.11±0.03% BOLD, 4.46±1.80% ASL, n=16 hemispheres), this correlation disappears during a carbogen stimulus (0.36±0.06% BOLD, 4.97±1.30% ASL). It is concluded that BOLD imaging should generally not be used in conjunction with a carbogen stimulus when measuring CVR, and that care must be taken when interpreting CVR as measured by ASL, as values obtained from different stimuli (CO2 in air versus carbogen) are not directly comparable.

The Multisensory Attentional Consequences of Tool Use: A Functional Magnetic Resonance Imaging Study

PubMed Central

Holmes, Nicholas P.; Spence, Charles; Hansen, Peter C.; Mackay, Clare E.; Calvert, Gemma A.

2008-01-01

Background Tool use in humans requires that multisensory information is integrated across different locations, from objects seen to be distant from the hand, but felt indirectly at the hand via the tool. We tested the hypothesis that using a simple tool to perceive vibrotactile stimuli results in the enhanced processing of visual stimuli presented at the distal, functional part of the tool. Such a finding would be consistent with a shift of spatial attention to the location where the tool is used. Methodology/Principal Findings We tested this hypothesis by scanning healthy human participants' brains using functional magnetic resonance imaging, while they used a simple tool to discriminate between target vibrations, accompanied by congruent or incongruent visual distractors, on the same or opposite side to the tool. The attentional hypothesis was supported: BOLD response in occipital cortex, particularly in the right hemisphere lingual gyrus, varied significantly as a function of tool position, increasing contralaterally, and decreasing ipsilaterally to the tool. Furthermore, these modulations occurred despite the fact that participants were repeatedly instructed to ignore the visual stimuli, to respond only to the vibrotactile stimuli, and to maintain visual fixation centrally. In addition, the magnitude of multisensory (visual-vibrotactile) interactions in participants' behavioural responses significantly predicted the BOLD response in occipital cortical areas that were also modulated as a function of both visual stimulus position and tool position. Conclusions/Significance These results show that using a simple tool to locate and to perceive vibrotactile stimuli is accompanied by a shift of spatial attention to the location where the functional part of the tool is used, resulting in enhanced processing of visual stimuli at that location, and decreased processing at other locations. This was most clearly observed in the right hemisphere lingual gyrus. Such modulations of visual processing may reflect the functional importance of visuospatial information during human tool use. PMID:18958150

Lateralized Spatial and Object Memory Encoding in Entorhinal and Perirhinal Cortices

ERIC Educational Resources Information Center

Bellgowan, Patrick S. F.; Buffalo, Elizabeth A.; Bodurka, Jerzy; Martin, Alex

2009-01-01

The perirhinal and entorhinal cortices are critical components of the medial temporal lobe (MTL) declarative memory system. Study of their specific functions using blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI), however, has suffered from severe magnetic susceptibility signal dropout resulting in poor…

PARTICLE FILTERING WITH SEQUENTIAL PARAMETER LEARNING FOR NONLINEAR BOLD fMRI SIGNALS.

PubMed

Xia, Jing; Wang, Michelle Yongmei

Analyzing the blood oxygenation level dependent (BOLD) effect in the functional magnetic resonance imaging (fMRI) is typically based on recent ground-breaking time series analysis techniques. This work represents a significant improvement over existing approaches to system identification using nonlinear hemodynamic models. It is important for three reasons. First, instead of using linearized approximations of the dynamics, we present a nonlinear filtering based on the sequential Monte Carlo method to capture the inherent nonlinearities in the physiological system. Second, we simultaneously estimate the hidden physiological states and the system parameters through particle filtering with sequential parameter learning to fully take advantage of the dynamic information of the BOLD signals. Third, during the unknown static parameter learning, we employ the low-dimensional sufficient statistics for efficiency and avoiding potential degeneration of the parameters. The performance of the proposed method is validated using both the simulated data and real BOLD fMRI data.

Spatial working memory in neurofibromatosis 1: Altered neural activity and functional connectivity.

PubMed

Ibrahim, Amira F A; Montojo, Caroline A; Haut, Kristen M; Karlsgodt, Katherine H; Hansen, Laura; Congdon, Eliza; Rosser, Tena; Bilder, Robert M; Silva, Alcino J; Bearden, Carrie E

2017-01-01

Neurofibromatosis Type 1 (NF1) is a genetic disorder that disrupts central nervous system development and neuronal function. Cognitively, NF1 is characterized by difficulties with executive control and visuospatial abilities. Little is known about the neural substrates underlying these deficits. The current study utilized Blood-Oxygen-Level-Dependent (BOLD) functional MRI (fMRI) to explore the neural correlates of spatial working memory (WM) deficits in patients with NF1. BOLD images were acquired from 23 adults with NF1 (age M  = 32.69; 61% male) and 25 matched healthy controls (age M  = 33.08; 64% male) during an in-scanner visuo-spatial WM task. Whole brain functional and psycho-physiological interaction analyses were utilized to investigate neural activity and functional connectivity, respectively, during visuo-spatial WM performance. Participants also completed behavioral measures of spatial reasoning and verbal WM. Relative to healthy controls, participants with NF1 showed reduced recruitment of key components of WM circuitry, the left dorsolateral prefrontal cortex and right parietal cortex. In addition, healthy controls exhibited greater simultaneous deactivation between the posterior cingulate cortex (PCC) and temporal regions than NF1 patients. In contrast, NF1 patients showed greater PCC and bilateral parietal connectivity with visual cortices as well as between the PCC and the cerebellum. In NF1 participants, increased functional coupling of the PCC with frontal and parietal regions was associated with better spatial reasoning and WM performance, respectively; these relationships were not observed in controls. Dysfunctional engagement of WM circuitry, and aberrant functional connectivity of 'task-negative' regions in NF1 patients may underlie spatial WM difficulties characteristic of the disorder.

Dual-echo ASL based assessment of motor networks: a feasibility study

NASA Astrophysics Data System (ADS)

Storti, Silvia Francesca; Boscolo Galazzo, Ilaria; Pizzini, Francesca B.; Menegaz, Gloria

2018-04-01

Objective. Dual-echo arterial spin labeling (DE-ASL) technique has been recently proposed for the simultaneous acquisition of ASL and blood-oxygenation-level-dependent (BOLD)-functional magnetic resonance imaging (fMRI) data. The assessment of this technique in detecting functional connectivity at rest or during motor and motor imagery tasks is still unexplored both per-se and in comparison with conventional methods. The purpose is to quantify the sensitivity of the DE-ASL sequence with respect to the conventional fMRI sequence (cvBOLD) in detecting brain activations, and to assess and compare the relevance of node features in decoding the network structure. Approach. Thirteen volunteers were scanned acquiring a pseudo-continuous DE-ASL sequence from which the concomitant BOLD (ccBOLD) simultaneously to the ASL can be extracted. The approach consists of two steps: (i) model-based analyses for assessing brain activations at individual and group levels, followed by statistical analysis for comparing the activation elicited by the three sequences under two conditions (motor and motor imagery), respectively; (ii) brain connectivity graph-theoretical analysis for assessing and comparing the network models properties. Main results. Our results suggest that cvBOLD and ccBOLD have comparable sensitivity in detecting the regions involved in the active task, whereas ASL offers a higher degree of co-localization with smaller activation volumes. The connectivity results and the comparative analysis of node features across sequences revealed that there are no strong changes between rest and tasks and that the differences between the sequences are limited to few connections. Significance. Considering the comparable sensitivity of the ccBOLD and cvBOLD sequences in detecting activated brain regions, the results demonstrate that DE-ASL can be successfully applied in functional studies allowing to obtain both ASL and BOLD information within a single sequence. Further, DE-ASL is a powerful technique for research and clinical applications allowing to perform quantitative comparisons as well as to characterize functional connectivity.

Decoding individual episodic memory traces in the human hippocampus.

PubMed

Chadwick, Martin J; Hassabis, Demis; Weiskopf, Nikolaus; Maguire, Eleanor A

2010-03-23

In recent years, multivariate pattern analyses have been performed on functional magnetic resonance imaging (fMRI) data, permitting prediction of mental states from local patterns of blood oxygen-level-dependent (BOLD) signal across voxels. We previously demonstrated that it is possible to predict the position of individuals in a virtual-reality environment from the pattern of activity across voxels in the hippocampus. Although this shows that spatial memories can be decoded, substantially more challenging, and arguably only possible to investigate in humans, is whether it is feasible to predict which complex everyday experience, or episodic memory, a person is recalling. Here we document for the first time that traces of individual rich episodic memories are detectable and distinguishable solely from the pattern of fMRI BOLD signals across voxels in the human hippocampus. In so doing, we uncovered a possible functional topography in the hippocampus, with preferential episodic processing by some hippocampal regions over others. Moreover, our results imply that the neuronal traces of episodic memories are stable (and thus predictable) even over many re-activations. Finally, our data provide further evidence for functional differentiation within the medial temporal lobe, in that we show the hippocampus contains significantly more episodic information than adjacent structures. 2010 Elsevier Ltd. All rights reserved.

Blood oxygen-level dependent functional assessment of cerebrovascular reactivity: Feasibility for intraoperative 3 Tesla MRI.

PubMed

Fierstra, Jorn; Burkhardt, Jan-Karl; van Niftrik, Christiaan Hendrik Bas; Piccirelli, Marco; Pangalu, Athina; Kocian, Roman; Neidert, Marian Christoph; Valavanis, Antonios; Regli, Luca; Bozinov, Oliver

2017-02-01

To assess the feasibility of functional blood oxygen-level dependent (BOLD) MRI to evaluate intraoperative cerebrovascular reactivity (CVR) at 3 Tesla field strength. Ten consecutive neurosurgical subjects scheduled for a clinical intraoperative MRI examination were enrolled in this study. In addition to the clinical protocol a BOLD sequence was implemented with three cycles of 44 s apnea to calculate CVR values on a voxel-by-voxel basis throughout the brain. The CVR range was then color-coded and superimposed on an anatomical volume to create high spatial resolution CVR maps. Ten subjects (mean age 34.8 ± 13.4; 2 females) uneventfully underwent the intraoperative BOLD protocol, with no complications occurring. Whole-brain CVR for all subjects was (mean ± SD) 0.69 ± 0.42, whereas CVR was markedly higher for tumor subjects as compared to vascular subjects, 0.81 ± 0.44 versus 0.33 ± 0.10, respectively. Furthermore, color-coded functional maps could be robustly interpreted for a whole-brain assessment of CVR. We demonstrate that intraoperative BOLD MRI is feasible in creating functional maps to assess cerebrovascular reactivity throughout the brain in subjects undergoing a neurosurgical procedure. Magn Reson Med 77:806-813, 2017. © 2016 International Society for Magnetic Resonance in Medicine. © 2016 International Society for Magnetic Resonance in Medicine.

Direct evidence for attention-dependent influences of the frontal eye-fields on feature-responsive visual cortex.

PubMed

Heinen, Klaartje; Feredoes, Eva; Weiskopf, Nikolaus; Ruff, Christian C; Driver, Jon

2014-11-01

Voluntary selective attention can prioritize different features in a visual scene. The frontal eye-fields (FEF) are one potential source of such feature-specific top-down signals, but causal evidence for influences on visual cortex (as was shown for "spatial" attention) has remained elusive. Here, we show that transcranial magnetic stimulation (TMS) applied to right FEF increased the blood oxygen level-dependent (BOLD) signals in visual areas processing "target feature" but not in "distracter feature"-processing regions. TMS-induced BOLD signals increase in motion-responsive visual cortex (MT+) when motion was attended in a display with moving dots superimposed on face stimuli, but in face-responsive fusiform area (FFA) when faces were attended to. These TMS effects on BOLD signal in both regions were negatively related to performance (on the motion task), supporting the behavioral relevance of this pathway. Our findings provide new causal evidence for the human FEF in the control of nonspatial "feature"-based attention, mediated by dynamic influences on feature-specific visual cortex that vary with the currently attended property. © The Author 2013. Published by Oxford University Press.

Local activity determines functional connectivity in the resting human brain: a simultaneous FDG-PET/fMRI study.

PubMed

Riedl, Valentin; Bienkowska, Katarzyna; Strobel, Carola; Tahmasian, Masoud; Grimmer, Timo; Förster, Stefan; Friston, Karl J; Sorg, Christian; Drzezga, Alexander

2014-04-30

Over the last decade, synchronized resting-state fluctuations of blood oxygenation level-dependent (BOLD) signals between remote brain areas [so-called BOLD resting-state functional connectivity (rs-FC)] have gained enormous relevance in systems and clinical neuroscience. However, the neural underpinnings of rs-FC are still incompletely understood. Using simultaneous positron emission tomography/magnetic resonance imaging we here directly investigated the relationship between rs-FC and local neuronal activity in humans. Computational models suggest a mechanistic link between the dynamics of local neuronal activity and the functional coupling among distributed brain regions. Therefore, we hypothesized that the local activity (LA) of a region at rest determines its rs-FC. To test this hypothesis, we simultaneously measured both LA (glucose metabolism) and rs-FC (via synchronized BOLD fluctuations) during conditions of eyes closed or eyes open. During eyes open, LA increased in the visual system, and the salience network (i.e., cingulate and insular cortices) and the pattern of elevated LA coincided almost exactly with the spatial pattern of increased rs-FC. Specifically, the voxelwise regional profile of LA in these areas strongly correlated with the regional pattern of rs-FC among the same regions (e.g., LA in primary visual cortex accounts for ∼ 50%, and LA in anterior cingulate accounts for ∼ 20% of rs-FC with the visual system). These data provide the first direct evidence in humans that local neuronal activity determines BOLD FC at rest. Beyond its relevance for the neuronal basis of coherent BOLD signal fluctuations, our procedure may translate into clinical research particularly to investigate potentially aberrant links between local dynamics and remote functional coupling in patients with neuropsychiatric disorders.

Functional magnetic resonance imaging of working memory in Huntington's disease: cross-sectional data from the IMAGE-HD study.

PubMed

Georgiou-Karistianis, Nellie; Stout, Julie C; Domínguez D, Juan F; Carron, Sarah P; Ando, Ayaka; Churchyard, Andrew; Chua, Phyllis; Bohanna, India; Dymowski, Alicia R; Poudel, Govinda; Egan, Gary F

2014-05-01

We used functional magnetic resonance imaging (fMRI) to investigate spatial working memory (WM) in an N-BACK task (0, 1, and 2-BACK) in premanifest Huntington's disease (pre-HD, n = 35), early symptomatic Huntington's disease (symp-HD, n = 23), and control (n = 32) individuals. Overall, both WM conditions (1-BACK and 2-BACK) activated a large network of regions throughout the brain, common to all groups. However, voxel-wise and time-course analyses revealed significant functional group differences, despite no significant behavioral performance differences. During 1-BACK, voxel-wise blood-oxygen-level-dependent (BOLD) signal activity was significantly reduced in a number of regions from the WM network (inferior frontal gyrus, anterior insula, caudate, putamen, and cerebellum) in pre-HD and symp-HD groups, compared with controls; however, time-course analysis of the BOLD response in the dorsolateral prefrontal cortex (DLPFC) showed increased activation in symp-HD, compared with pre-HD and controls. The pattern of reduced voxel-wise BOLD activity in pre-HD and symp-HD, relative to controls, became more pervasive during 2-BACK affecting the same structures as in 1-BACK, but also incorporated further WM regions (anterior cingulate gyrus, parietal lobe and thalamus). The DLPFC BOLD time-course for 2-BACK showed a reversed pattern to that observed in 1-BACK, with a significantly diminished signal in symp-HD, relative to pre-HD and controls. Our findings provide support for functional brain reorganisation in cortical and subcortical regions in both pre-HD and symp-HD, which are modulated by task difficulty. Moreover, the lack of a robust striatal BOLD signal in pre-HD may represent a very early signature of change observed up to 15 years prior to clinical diagnosis. Copyright © 2013 Wiley Periodicals, Inc.

Monaural and binaural contributions to interaural-level-difference sensitivity in human auditory cortex.

PubMed

Stecker, G Christopher; McLaughlin, Susan A; Higgins, Nathan C

2015-10-15

Whole-brain functional magnetic resonance imaging was used to measure blood-oxygenation-level-dependent (BOLD) responses in human auditory cortex (AC) to sounds with intensity varying independently in the left and right ears. Echoplanar images were acquired at 3 Tesla with sparse image acquisition once per 12-second block of sound stimulation. Combinations of binaural intensity and stimulus presentation rate were varied between blocks, and selected to allow measurement of response-intensity functions in three configurations: monaural 55-85 dB SPL, binaural 55-85 dB SPL with intensity equal in both ears, and binaural with average binaural level of 70 dB SPL and interaural level differences (ILD) ranging ±30 dB (i.e., favoring the left or right ear). Comparison of response functions equated for contralateral intensity revealed that BOLD-response magnitudes (1) generally increased with contralateral intensity, consistent with positive drive of the BOLD response by the contralateral ear, (2) were larger for contralateral monaural stimulation than for binaural stimulation, consistent with negative effects (e.g., inhibition) of ipsilateral input, which were strongest in the left hemisphere, and (3) also increased with ipsilateral intensity when contralateral input was weak, consistent with additional, positive, effects of ipsilateral stimulation. Hemispheric asymmetries in the spatial extent and overall magnitude of BOLD responses were generally consistent with previous studies demonstrating greater bilaterality of responses in the right hemisphere and stricter contralaterality in the left hemisphere. Finally, comparison of responses to fast (40/s) and slow (5/s) stimulus presentation rates revealed significant rate-dependent adaptation of the BOLD response that varied across ILD values. Copyright © 2015. Published by Elsevier Inc.

Widespread correlation patterns of fMRI signal across visual cortex reflect eccentricity organization.

PubMed

Arcaro, Michael J; Honey, Christopher J; Mruczek, Ryan E B; Kastner, Sabine; Hasson, Uri

2015-02-19

The human visual system can be divided into over two-dozen distinct areas, each of which contains a topographic map of the visual field. A fundamental question in vision neuroscience is how the visual system integrates information from the environment across different areas. Using neuroimaging, we investigated the spatial pattern of correlated BOLD signal across eight visual areas on data collected during rest conditions and during naturalistic movie viewing. The correlation pattern between areas reflected the underlying receptive field organization with higher correlations between cortical sites containing overlapping representations of visual space. In addition, the correlation pattern reflected the underlying widespread eccentricity organization of visual cortex, in which the highest correlations were observed for cortical sites with iso-eccentricity representations including regions with non-overlapping representations of visual space. This eccentricity-based correlation pattern appears to be part of an intrinsic functional architecture that supports the integration of information across functionally specialized visual areas.

Cortical systems mediating visual attention to both objects and spatial locations

PubMed Central

Shomstein, Sarah; Behrmann, Marlene

2006-01-01

Natural visual scenes consist of many objects occupying a variety of spatial locations. Given that the plethora of information cannot be processed simultaneously, the multiplicity of inputs compete for representation. Using event-related functional MRI, we show that attention, the mechanism by which a subset of the input is selected, is mediated by the posterior parietal cortex (PPC). Of particular interest is that PPC activity is differentially sensitive to the object-based properties of the input, with enhanced activation for those locations bound by an attended object. Of great interest too is the ensuing modulation of activation in early cortical regions, reflected as differences in the temporal profile of the blood oxygenation level-dependent (BOLD) response for within-object versus between-object locations. These findings indicate that object-based selection results from an object-sensitive reorienting signal issued by the PPC. The dynamic circuit between the PPC and earlier sensory regions then enables observers to attend preferentially to objects of interest in complex scenes. PMID:16840559

When the Brain Takes 'BOLD' Steps: Real-Time fMRI Neurofeedback Can Further Enhance the Ability to Gradually Self-regulate Regional Brain Activation.

PubMed

Sorger, Bettina; Kamp, Tabea; Weiskopf, Nikolaus; Peters, Judith Caroline; Goebel, Rainer

2018-05-15

Brain-computer interfaces (BCIs) based on real-time functional magnetic resonance imaging (rtfMRI) are currently explored in the context of developing alternative (motor-independent) communication and control means for the severely disabled. In such BCI systems, the user encodes a particular intention (e.g., an answer to a question or an intended action) by evoking specific mental activity resulting in a distinct brain state that can be decoded from fMRI activation. One goal in this context is to increase the degrees of freedom in encoding different intentions, i.e., to allow the BCI user to choose from as many options as possible. Recently, the ability to voluntarily modulate spatial and/or temporal blood oxygenation level-dependent (BOLD)-signal features has been explored implementing different mental tasks and/or different encoding time intervals, respectively. Our two-session fMRI feasibility study systematically investigated for the first time the possibility of using magnitudinal BOLD-signal features for intention encoding. Particularly, in our novel paradigm, participants (n=10) were asked to alternately self-regulate their regional brain-activation level to 30%, 60% or 90% of their maximal capacity by applying a selected activation strategy (i.e., performing a mental task, e.g., inner speech) and modulation strategies (e.g., using different speech rates) suggested by the experimenters. In a second step, we tested the hypothesis that the additional availability of feedback information on the current BOLD-signal level within a region of interest improves the gradual-self regulation performance. Therefore, participants were provided with neurofeedback in one of the two fMRI sessions. Our results show that the majority of the participants were able to gradually self-regulate regional brain activation to at least two different target levels even in the absence of neurofeedback. When provided with continuous feedback on their current BOLD-signal level, most participants further enhanced their gradual self-regulation ability. Our findings were observed across a wide variety of mental tasks and across clinical MR field strengths (i.e., at 1.5T and 3T), indicating that these findings are robust and can be generalized across mental tasks and scanner types. The suggested novel parametric activation paradigm enriches the spectrum of current rtfMRI-neurofeedback and BCI methodology and has considerable potential for fundamental and clinical neuroscience applications. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

The Response of the Left Ventral Attentional System to Invalid Targets and its Implication for the Spatial Neglect Syndrome: a Multivariate fMRI Investigation.

PubMed

Silvetti, Massimo; Lasaponara, Stefano; Lecce, Francesca; Dragone, Alessio; Macaluso, Emiliano; Doricchi, Fabrizio

2016-12-01

In humans, invalid visual targets that mismatch spatial expectations induced by attentional cues are considered to selectively engage a right hemispheric "reorienting" network that includes the temporal parietal junction (TPJ), the inferior frontal gyrus (IFG), and the medial frontal gyrus (MFG). However, recent findings suggest that this hemispheric dominance is not absolute and that it is rather observed because the TPJ and IFG areas in the left hemisphere are engaged both by invalid and valid cued targets. Because of this, the BOLD response of the left hemisphere to invalid targets is usually cancelled out by the standard "invalid versus valid" contrast used in functional magnetic resonance imaging investigations of spatial attention. Here, we used multivariate pattern recognition analysis (MVPA) to gain finer insight into the role played by the left TPJ and IFG in reorienting to invalid targets. We found that in left TPJ and IFG blood oxygen level-dependent (BOLD) responses to invalid and valid targets were associated to different patterns of neural activity, possibly reflecting the presence of functionally distinct neuronal populations. Pattern segregation was significant at group level, it was present in almost all of the participants to the study and was observed both for targets in the left and right side of space. A control whole-brain MVPA ("Searchlight" analysis) confirmed the results obtained in predefined regions of interest and highlighted that also other areas, that is, superior parietal and frontal-polar cortex, show different patterns of BOLD response to valid and invalid targets. These results confirm and expand previous evidence highlighting the involvement of the left hemisphere in reorienting of visual attention (Doricchi et al. 2010; Dragone et al. 2015). These findings suggest that asymmetrical reorienting deficits suffered by right brain damaged patients with left spatial neglect, who have severe impairments in contralesional reorienting and less severe impairments in ipsilesional reorienting, are due to preserved reorienting abilities in the intact left hemisphere. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Spatial-temporal-spectral EEG patterns of BOLD functional network connectivity dynamics

NASA Astrophysics Data System (ADS)

Lamoš, Martin; Mareček, Radek; Slavíček, Tomáš; Mikl, Michal; Rektor, Ivan; Jan, Jiří

2018-06-01

Objective. Growing interest in the examination of large-scale brain network functional connectivity dynamics is accompanied by an effort to find the electrophysiological correlates. The commonly used constraints applied to spatial and spectral domains during electroencephalogram (EEG) data analysis may leave part of the neural activity unrecognized. We propose an approach that blindly reveals multimodal EEG spectral patterns that are related to the dynamics of the BOLD functional network connectivity. Approach. The blind decomposition of EEG spectrogram by parallel factor analysis has been shown to be a useful technique for uncovering patterns of neural activity. The simultaneously acquired BOLD fMRI data were decomposed by independent component analysis. Dynamic functional connectivity was computed on the component’s time series using a sliding window correlation, and between-network connectivity states were then defined based on the values of the correlation coefficients. ANOVA tests were performed to assess the relationships between the dynamics of between-network connectivity states and the fluctuations of EEG spectral patterns. Main results. We found three patterns related to the dynamics of between-network connectivity states. The first pattern has dominant peaks in the alpha, beta, and gamma bands and is related to the dynamics between the auditory, sensorimotor, and attentional networks. The second pattern, with dominant peaks in the theta and low alpha bands, is related to the visual and default mode network. The third pattern, also with peaks in the theta and low alpha bands, is related to the auditory and frontal network. Significance. Our previous findings revealed a relationship between EEG spectral pattern fluctuations and the hemodynamics of large-scale brain networks. In this study, we suggest that the relationship also exists at the level of functional connectivity dynamics among large-scale brain networks when no standard spatial and spectral constraints are applied on the EEG data.

Frequency-dependent tACS modulation of BOLD signal during rhythmic visual stimulation.

PubMed

Chai, Yuhui; Sheng, Jingwei; Bandettini, Peter A; Gao, Jia-Hong

2018-05-01

Transcranial alternating current stimulation (tACS) has emerged as a promising tool for modulating cortical oscillations. In previous electroencephalogram (EEG) studies, tACS has been found to modulate brain oscillatory activity in a frequency-specific manner. However, the spatial distribution and hemodynamic response for this modulation remains poorly understood. Functional magnetic resonance imaging (fMRI) has the advantage of measuring neuronal activity in regions not only below the tACS electrodes but also across the whole brain with high spatial resolution. Here, we measured fMRI signal while applying tACS to modulate rhythmic visual activity. During fMRI acquisition, tACS at different frequencies (4, 8, 16, and 32 Hz) was applied along with visual flicker stimulation at 8 and 16 Hz. We analyzed the blood-oxygen-level-dependent (BOLD) signal difference between tACS-ON vs tACS-OFF, and different frequency combinations (e.g., 4 Hz tACS, 8 Hz flicker vs 8 Hz tACS, 8 Hz flicker). We observed significant tACS modulation effects on BOLD responses when the tACS frequency matched the visual flicker frequency or the second harmonic frequency. The main effects were predominantly seen in regions that were activated by the visual task and targeted by the tACS current distribution. These findings bridge different scientific domains of tACS research and demonstrate that fMRI could localize the tACS effect on stimulus-induced brain rhythms, which could lead to a new approach for understanding the high-level cognitive process shaped by the ongoing oscillatory signal. © 2018 Wiley Periodicals, Inc.

Extreme brain events: Higher-order statistics of brain resting activity and its relation with structural connectivity

NASA Astrophysics Data System (ADS)

Amor, T. A.; Russo, R.; Diez, I.; Bharath, P.; Zirovich, M.; Stramaglia, S.; Cortes, J. M.; de Arcangelis, L.; Chialvo, D. R.

2015-09-01

The brain exhibits a wide variety of spatiotemporal patterns of neuronal activity recorded using functional magnetic resonance imaging as the so-called blood-oxygenated-level-dependent (BOLD) signal. An active area of work includes efforts to best describe the plethora of these patterns evolving continuously in the brain. Here we explore the third-moment statistics of the brain BOLD signals in the resting state as a proxy to capture extreme BOLD events. We find that the brain signal exhibits typically nonzero skewness, with positive values for cortical regions and negative values for subcortical regions. Furthermore, the combined analysis of structural and functional connectivity demonstrates that relatively more connected regions exhibit activity with high negative skewness. Overall, these results highlight the relevance of recent results emphasizing that the spatiotemporal location of the relatively large-amplitude events in the BOLD time series contains relevant information to reproduce a number of features of the brain dynamics during resting state in health and disease.

Latencies in BOLD response during visual attention processes.

PubMed

Kellermann, Thilo; Reske, Martina; Jansen, Andreas; Satrapi, Peyman; Shah, N Jon; Schneider, Frank; Habel, Ute

2011-04-22

One well-investigated division of attentional processes focuses on alerting, orienting and executive control, which can be assessed applying the attentional network test (ANT). The goal of the present study was to add further knowledge about the temporal dynamics of relevant neural correlates. As a right hemispheric dominance for alerting and orienting has previously been reported for intrinsic but not for phasic alertness, we additionally addressed a potential impact of this lateralization of attention by employing a lateralized version of the ANT, capturing phasic alertness processes. Sixteen healthy subjects underwent event-related functional magnetic resonance imaging (fMRI) while performing the ANT. Analyses of BOLD magnitude replicated the engagement of a fronto-parietal network in the attentional subsystems. The amplitudes of the attentional contrasts interacted with visual field presentation in the sense that the thalamus revealed a greater involvement for spatially cued items presented in the left visual field. Comparisons of BOLD latencies in visual cortices, first, verified faster BOLD responses following contra-lateral stimulus presentation. Second and more importantly, we identified attention-modulated activation in secondary visual and anterior cingulate cortices. Results are discussed in terms of bottom-up and lateralization processes. Although intrinsic and phasic alertness are distinct cognitive processes, we propose that neural substrates of intrinsic alertness may be accessed by phasic alertness provided that the attention-dominant (i.e., the right) hemisphere is activated directly by a warning stimulus. Copyright © 2011 Elsevier B.V. All rights reserved.

Brain atrophy can introduce age-related differences in BOLD response.

PubMed

Liu, Xueqing; Gerraty, Raphael T; Grinband, Jack; Parker, David; Razlighi, Qolamreza R

2017-04-11

Use of functional magnetic resonance imaging (fMRI) in studies of aging is often hampered by uncertainty about age-related differences in the amplitude and timing of the blood oxygenation level dependent (BOLD) response (i.e., hemodynamic impulse response function (HRF)). Such uncertainty introduces a significant challenge in the interpretation of the fMRI results. Even though this issue has been extensively investigated in the field of neuroimaging, there is currently no consensus about the existence and potential sources of age-related hemodynamic alterations. Using an event-related fMRI experiment with two robust and well-studied stimuli (visual and auditory), we detected a significant age-related difference in the amplitude of response to auditory stimulus. Accounting for brain atrophy by circumventing spatial normalization and processing the data in subjects' native space eliminated these observed differences. In addition, we simulated fMRI data using age differences in brain morphology while controlling HRF shape. Analyzing these simulated fMRI data using standard image processing resulted in differences in HRF amplitude, which were eliminated when the data were analyzed in subjects' native space. Our results indicate that age-related atrophy introduces inaccuracy in co-registration to standard space, which subsequently appears as attenuation in BOLD response amplitude. Our finding could explain some of the existing contradictory reports regarding age-related differences in the fMRI BOLD responses. Hum Brain Mapp, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Spatial memory: a Rosetta stone for rat and human hippocampal discourse: Theoretical comment on Goodrich-Hunsaker and Hopkins (2010).

PubMed

Sutherland, Robert J

2010-06-01

The article by Goodrich-Hunsaker and Hopkins (2010, this issue) takes up an important place among in the recent contributions on the role of the hippocampus in memory. They evaluate the effect of bilateral damage to the hippocampus on performance by human participants in a virtual 8-arm radial maze. The hippocampal damage appears to be highly selective and nearly complete. Exactly as with selective hippocampal damage in rats, the human participants showed a deficit in accurately choosing rewarded versus never-rewarded arms and a deficit in avoiding reentering recently visited arms. The results are triply significant: (1) They provide good support for the idea that the wealth of neurobiological information, from network to synapse to gene, on spatial memory in the rat may apply as a whole to the human hippocampal memory system; (2) They affirm the utility of human virtual task models of rat spatial memory tasks; (3) They support one interpretation of the dampening of the hippocampal functional MRI (fMRI) blood oxygen level-dependent (BOLD) signal during performance of the virtual radial arm maze observed by Astur et al. (2005).

Information Operations as a Core Competency

DTIC Science & Technology

2005-01-01

the emerging American way of war means fighting first for information dominance . Nothing better exemplifies this bold push for transformation and... information dominance than the DoD commitment to make information operations (IO) a core military competency. On October 30, 2003, Secretary Rumsfeld

Physiological denoising of BOLD fMRI data using Regressor Interpolation at Progressive Time Delays (RIPTiDe) processing of concurrent fMRI and near-infrared spectroscopy (NIRS).

PubMed

Frederick, Blaise deB; Nickerson, Lisa D; Tong, Yunjie

2012-04-15

Confounding noise in BOLD fMRI data arises primarily from fluctuations in blood flow and oxygenation due to cardiac and respiratory effects, spontaneous low frequency oscillations (LFO) in arterial pressure, and non-task related neural activity. Cardiac noise is particularly problematic, as the low sampling frequency of BOLD fMRI ensures that these effects are aliased in recorded data. Various methods have been proposed to estimate the noise signal through measurement and transformation of the cardiac and respiratory waveforms (e.g. RETROICOR and respiration volume per time (RVT)) and model-free estimation of noise variance through examination of spatial and temporal patterns. We have previously demonstrated that by applying a voxel-specific time delay to concurrently acquired near infrared spectroscopy (NIRS) data, we can generate regressors that reflect systemic blood flow and oxygenation fluctuations effects. Here, we apply this method to the task of removing physiological noise from BOLD data. We compare the efficacy of noise removal using various sets of noise regressors generated from NIRS data, and also compare the noise removal to RETROICOR+RVT. We compare the results of resting state analyses using the original and noise filtered data, and we evaluate the bias for the different noise filtration methods by computing null distributions from the resting data and comparing them with the expected theoretical distributions. Using the best set of processing choices, six NIRS-generated regressors with voxel-specific time delays explain a median of 10.5% of the variance throughout the brain, with the highest reductions being seen in gray matter. By comparison, the nine RETROICOR+RVT regressors together explain a median of 6.8% of the variance in the BOLD data. Detection of resting state networks was enhanced with NIRS denoising, and there were no appreciable differences in the bias of the different techniques. Physiological noise regressors generated using Regressor Interpolation at Progressive Time Delays (RIPTiDe) offer an effective method for efficiently removing hemodynamic noise from BOLD data. Copyright © 2012 Elsevier Inc. All rights reserved.

Task-Related Modulations of BOLD Low-Frequency Fluctuations within the Default Mode Network

PubMed Central

Tommasin, Silvia; Mascali, Daniele; Gili, Tommaso; Assan, Ibrahim Eid; Moraschi, Marta; Fratini, Michela; Wise, Richard G.; Macaluso, Emiliano; Mangia, Silvia; Giove, Federico

2017-01-01

Spontaneous low-frequency Blood-Oxygenation Level-Dependent (BOLD) signals acquired during resting state are characterized by spatial patterns of synchronous fluctuations, ultimately leading to the identification of robust brain networks. The resting-state brain networks, including the Default Mode Network (DMN), are demonstrated to persist during sustained task execution, but the exact features of task-related changes of network properties are still not well characterized. In this work we sought to examine in a group of 20 healthy volunteers (age 33 ± 6 years, 8 F/12 M) the relationship between changes of spectral and spatiotemporal features of one prominent resting-state network, namely the DMN, during the continuous execution of a working memory n-back task. We found that task execution impacted on both functional connectivity and amplitude of BOLD fluctuations within large parts of the DMN, but these changes correlated between each other only in a small area of the posterior cingulate. We conclude that combined analysis of multiple parameters related to connectivity, and their changes during the transition from resting state to continuous task execution, can contribute to a better understanding of how brain networks rearrange themselves in response to a task. PMID:28845420

MEG and fMRI Fusion for Non-Linear Estimation of Neural and BOLD Signal Changes

PubMed Central

Plis, Sergey M.; Calhoun, Vince D.; Weisend, Michael P.; Eichele, Tom; Lane, Terran

2010-01-01

The combined analysis of magnetoencephalography (MEG)/electroencephalography and functional magnetic resonance imaging (fMRI) measurements can lead to improvement in the description of the dynamical and spatial properties of brain activity. In this paper we empirically demonstrate this improvement using simulated and recorded task related MEG and fMRI activity. Neural activity estimates were derived using a dynamic Bayesian network with continuous real valued parameters by means of a sequential Monte Carlo technique. In synthetic data, we show that MEG and fMRI fusion improves estimation of the indirectly observed neural activity and smooths tracking of the blood oxygenation level dependent (BOLD) response. In recordings of task related neural activity the combination of MEG and fMRI produces a result with greater signal-to-noise ratio, that confirms the expectation arising from the nature of the experiment. The highly non-linear model of the BOLD response poses a difficult inference problem for neural activity estimation; computational requirements are also high due to the time and space complexity. We show that joint analysis of the data improves the system's behavior by stabilizing the differential equations system and by requiring fewer computational resources. PMID:21120141

BOLD delay times using group delay in sickle cell disease

NASA Astrophysics Data System (ADS)

Coloigner, Julie; Vu, Chau; Bush, Adam; Borzage, Matt; Rajagopalan, Vidya; Lepore, Natasha; Wood, John

2016-03-01

Sickle cell disease (SCD) is an inherited blood disorder that effects red blood cells, which can lead to vasoocclusion, ischemia and infarct. This disease often results in neurological damage and strokes, leading to morbidity and mortality. Functional Magnetic Resonance Imaging (fMRI) is a non-invasive technique for measuring and mapping the brain activity. Blood Oxygenation Level-Dependent (BOLD) signals contain also information about the neurovascular coupling, vascular reactivity, oxygenation and blood propagation. Temporal relationship between BOLD fluctuations in different parts of the brain provides also a mean to investigate the blood delay information. We used the induced desaturation as a label to profile transit times through different brain areas, reflecting oxygen utilization of tissue. In this study, we aimed to compare blood flow propagation delay times between these patients and healthy subjects in areas vascularized by anterior, middle and posterior cerebral arteries. In a group comparison analysis with control subjects, BOLD changes in these areas were found to be almost simultaneous and shorter in the SCD patients, because of their increased brain blood flow. Secondly, the analysis of a patient with a stenosis on the anterior cerebral artery indicated that signal of the area vascularized by this artery lagged the MCA signal. These findings suggest that sickle cell disease causes blood propagation modifications, and that these changes could be used as a biomarker of vascular damage.

GPS baseline configuration design based on robustness analysis

NASA Astrophysics Data System (ADS)

Yetkin, M.; Berber, M.

2012-11-01

The robustness analysis results obtained from a Global Positioning System (GPS) network are dramatically influenced by the configurationof the observed baselines. The selection of optimal GPS baselines may allow for a cost effective survey campaign and a sufficiently robustnetwork. Furthermore, using the approach described in this paper, the required number of sessions, the baselines to be observed, and thesignificance levels for statistical testing and robustness analysis can be determined even before the GPS campaign starts. In this study, wepropose a robustness criterion for the optimal design of geodetic networks, and present a very simple and efficient algorithm based on thiscriterion for the selection of optimal GPS baselines. We also show the relationship between the number of sessions and the non-centralityparameter. Finally, a numerical example is given to verify the efficacy of the proposed approach.

A Novel Method of Combining Blood Oxygenation and Blood Flow Sensitive Magnetic Resonance Imaging Techniques to Measure the Cerebral Blood Flow and Oxygen Metabolism Responses to an Unknown Neural Stimulus

PubMed Central

Simon, Aaron B.; Griffeth, Valerie E. M.; Wong, Eric C.; Buxton, Richard B.

2013-01-01

Simultaneous implementation of magnetic resonance imaging methods for Arterial Spin Labeling (ASL) and Blood Oxygenation Level Dependent (BOLD) imaging makes it possible to quantitatively measure the changes in cerebral blood flow (CBF) and cerebral oxygen metabolism (CMRO2) that occur in response to neural stimuli. To date, however, the range of neural stimuli amenable to quantitative analysis is limited to those that may be presented in a simple block or event related design such that measurements may be repeated and averaged to improve precision. Here we examined the feasibility of using the relationship between cerebral blood flow and the BOLD signal to improve dynamic estimates of blood flow fluctuations as well as to estimate metabolic-hemodynamic coupling under conditions where a stimulus pattern is unknown. We found that by combining the information contained in simultaneously acquired BOLD and ASL signals through a method we term BOLD Constrained Perfusion (BCP) estimation, we could significantly improve the precision of our estimates of the hemodynamic response to a visual stimulus and, under the conditions of a calibrated BOLD experiment, accurately determine the ratio of the oxygen metabolic response to the hemodynamic response. Importantly we were able to accomplish this without utilizing a priori knowledge of the temporal nature of the neural stimulus, suggesting that BOLD Constrained Perfusion estimation may make it feasible to quantitatively study the cerebral metabolic and hemodynamic responses to more natural stimuli that cannot be easily repeated or averaged. PMID:23382977

Nonlinear correlations impair quantification of episodic memory by mesial temporal BOLD activity.

PubMed

Klamer, Silke; Zeltner, Lena; Erb, Michael; Klose, Uwe; Wagner, Kathrin; Frings, Lars; Groen, Georg; Veil, Cornelia; Rona, Sabine; Lerche, Holger; Milian, Monika

2013-07-01

Episodic memory processes can be investigated using different functional MRI (fMRI) paradigms. The purpose of the present study was to examine correlations between neuropsychological memory test scores and BOLD signal changes during fMRI scanning using three different memory tasks. Twenty-eight right-handed healthy subjects underwent three paradigms, (a) a word pair, (b) a space-labyrinth, and (c) a face-name association paradigm. These paradigms were compared for their value in memory quantification and lateralization by calculating correlations between the BOLD signals in the mesial temporal lobe and behavioral data derived from a neuropsychological test battery. As expected, group analysis showed left-sided activation for the verbal, a tendency to right-sided activation for the spatial, and bilateral activation for the face-name paradigm. No linear correlations were observed between neuropsychological data and activation in the temporo-mesial region. However, we found significant u-shaped correlations between behavioral memory performance and activation in both the verbal and the face-name paradigms, that is, BOLD signal changes were greater not only among participants who performed best on the neuropsychological tests, but also among the poorest performers. The figural learning task did not correlate with the activations in the space-labyrinth paradigm at all. We interpreted the u-shaped correlations to be due to compensatory hippocampal activations associated with low performance when people try unsuccessfully to remember presented items. Because activation levels did not linearly increase with memory performance, the latter cannot be quantified by fMRI alone, but only be used in conjunction with neuropsychological testing. PsycINFO Database Record (c) 2013 APA, all rights reserved.

Iterative approach of dual regression with a sparse prior enhances the performance of independent component analysis for group functional magnetic resonance imaging (fMRI) data.

PubMed

Kim, Yong-Hwan; Kim, Junghoe; Lee, Jong-Hwan

2012-12-01

This study proposes an iterative dual-regression (DR) approach with sparse prior regularization to better estimate an individual's neuronal activation using the results of an independent component analysis (ICA) method applied to a temporally concatenated group of functional magnetic resonance imaging (fMRI) data (i.e., Tc-GICA method). An ordinary DR approach estimates the spatial patterns (SPs) of neuronal activation and corresponding time courses (TCs) specific to each individual's fMRI data with two steps involving least-squares (LS) solutions. Our proposed approach employs iterative LS solutions to refine both the individual SPs and TCs with an additional a priori assumption of sparseness in the SPs (i.e., minimally overlapping SPs) based on L(1)-norm minimization. To quantitatively evaluate the performance of this approach, semi-artificial fMRI data were created from resting-state fMRI data with the following considerations: (1) an artificially designed spatial layout of neuronal activation patterns with varying overlap sizes across subjects and (2) a BOLD time series (TS) with variable parameters such as onset time, duration, and maximum BOLD levels. To systematically control the spatial layout variability of neuronal activation patterns across the "subjects" (n=12), the degree of spatial overlap across all subjects was varied from a minimum of 1 voxel (i.e., 0.5-voxel cubic radius) to a maximum of 81 voxels (i.e., 2.5-voxel radius) across the task-related SPs with a size of 100 voxels for both the block-based and event-related task paradigms. In addition, several levels of maximum percentage BOLD intensity (i.e., 0.5, 1.0, 2.0, and 3.0%) were used for each degree of spatial overlap size. From the results, the estimated individual SPs of neuronal activation obtained from the proposed iterative DR approach with a sparse prior showed an enhanced true positive rate and reduced false positive rate compared to the ordinary DR approach. The estimated TCs of the task-related SPs from our proposed approach showed greater temporal correlation coefficients with a reference hemodynamic response function than those of the ordinary DR approach. Moreover, the efficacy of the proposed DR approach was also successfully demonstrated by the results of real fMRI data acquired from left-/right-hand clenching tasks in both block-based and event-related task paradigms. Copyright © 2012 Elsevier Inc. All rights reserved.

Functional connectivity and activity of white matter in somatosensory pathways under tactile stimulations.

PubMed

Wu, Xi; Yang, Zhipeng; Bailey, Stephen K; Zhou, Jiliu; Cutting, Laurie E; Gore, John C; Ding, Zhaohua

2017-05-15

Functional MRI has proven to be effective in detecting neural activity in brain cortices on the basis of blood oxygenation level dependent (BOLD) contrast, but has relatively poor sensitivity for detecting neural activity in white matter. To demonstrate that BOLD signals in white matter are detectable and contain information on neural activity, we stimulated the somatosensory system and examined distributions of BOLD signals in related white matter pathways. The temporal correlation profiles and frequency contents of BOLD signals were compared between stimulation and resting conditions, and between relevant white matter fibers and background regions, as well as between left and right side stimulations. Quantitative analyses show that, overall, MR signals from white matter fiber bundles in the somatosensory system exhibited significantly greater temporal correlations with the primary sensory cortex and greater signal power during tactile stimulations than in a resting state, and were stronger than corresponding measurements for background white matter both during stimulations and in a resting state. The temporal correlation and signal power under stimulation were found to be twice those observed from the same bundle in a resting state, and bore clear relations with the side of stimuli. These indicate that BOLD signals in white matter fibers encode neural activity related to their functional roles connecting cortical volumes, which are detectable with appropriate methods. Copyright © 2017 Elsevier Inc. All rights reserved.

Differentiating psychopathy from antisocial personality disorder: a triarchic model perspective.

PubMed

Venables, N C; Hall, J R; Patrick, C J

2014-04-01

The triarchic model of psychopathy characterizes the disorder in terms of three distinguishable phenotypic facets: disinhibition, meanness and boldness. The present study sought to (1) inform current debates regarding the role of boldness in the definition of psychopathy and (2) clarify boundaries between psychopathy and antisocial personality disorder (ASPD). This study evaluated the degree to which facets of the triarchic model are represented in the most widely used clinical inventory for psychopathy, the Psychopathy Checklist - Revised (PCL-R), in comparison with ASPD as defined by DSM-IV criteria. Adult male offenders from two distinct correctional settings (n = 157 and 169) were investigated to ensure replicability of findings across samples exhibiting high base rates of psychopathy and antisocial behavior. We found evidence for convergent and discriminant validity of the three triarchic facets in predicting symptomatic components of psychopathy as assessed by the PCL-R. Additionally, and crucially vis-à-vis current debates in the field, we found that boldness contributed incrementally (over and above disinhibition and meanness) to prediction of PCL-R psychopathy, in particular its interpersonal style component, but not ASPD. The three distinct facets of the triarchic model of psychopathy are represented clearly and distinctly in the PCL-R, with boldness through its interpersonal facet, but not in DSM-defined ASPD. Our findings suggest that boldness is central to diagnostic conceptions of psychopathy and distinguishes psychopathy from the more prevalent diagnosis of ASPD.

Metabolism study of boldenone in human urine by gas chromatography-tandem mass spectrometry.

PubMed

Wu, Xinchen; Gao, Feng; Zhang, Wenxin; Ni, Jian

2015-11-10

Boldenone (BOLD), an anabolic steroid, is likely to be abused in livestock breeding and in sports. Although some of BOLD metabolites in human urine, such as 5β-adrost-1-en-17β-ol-3-one (BM1), have been detected, investigations on their excretion patterns for both genders are insufficient. Moreover, little research on 17α-BOLD glucuronide as a metabolite in human urine has been reported. The aim of this study is to make a contribution to the knowledge of 17β-BOLD metabolism in humans. Three male and three female volunteers were orally administrated with 30mg 17β-BOLD. Urine samples were collected and analyzed with gas chromatography-tandem mass spectrometry. The data proved that 17β-BOLD, BM1, and 17α-BOLD were excreted in urine in both free and glucuronic conjugated forms after administration of 17β-BOLD. For most subjects, the urinary concentrations of BM1 were higher than that of 17β-BOLD. 17α-BOLD was excreted in small amounts. 17α-BOLD, 17β-BOLD, and BM1 were present naturally in urine with low concentrations. Administration of 30mg 17β-BOLD could not influence the excretion profiles of urinary androsterone, etiocholanolone, and testosterone/epitestosterone ratio. There were no differences in BOLD metabolic patterns between man and woman. Copyright © 2015 Elsevier B.V. All rights reserved.

Ray tracing: Experience at SRC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Severson, M.

1996-09-01

SHADOW [B. Lai and F. Cerrina, Nucl. Instrum. Methods A {bold 246}, 337 (1986)] is the primary ray-tracing program used at SRC. Ray tracing provides a tremendous amount of information regarding beamline layout, mirror sizes, resolution, alignment tolerances, and beam size at various locations. It also provides a way to check the beamline design for errors. Two recent designs have been ray traced extensively: an undulator-based, 4-meter, normal-incidence monochromator (NIM) [R. Reininger, M.C. Severson, R.W.C. Hansen, W.R. Winter, M.A. Green, and W.S. Trzeciak, Rev. Sci. Instrum. {bold 66}, 2194 (1995)] and an undulator-based, plane-grating monochromator (PGM) [R. Reininger, S.L. Crossley,more » M.A. Lagergren, M.C. Severson, and R.W.C. Hansen, Nucl. Instrum. Methods A {bold 347}, 304 (1994)]. {copyright} {ital 1996 American Institute of Physics.}« less

Widespread correlation patterns of fMRI signal across visual cortex reflect eccentricity organization

PubMed Central

Arcaro, Michael J; Honey, Christopher J; Mruczek, Ryan EB; Kastner, Sabine; Hasson, Uri

2015-01-01

The human visual system can be divided into over two-dozen distinct areas, each of which contains a topographic map of the visual field. A fundamental question in vision neuroscience is how the visual system integrates information from the environment across different areas. Using neuroimaging, we investigated the spatial pattern of correlated BOLD signal across eight visual areas on data collected during rest conditions and during naturalistic movie viewing. The correlation pattern between areas reflected the underlying receptive field organization with higher correlations between cortical sites containing overlapping representations of visual space. In addition, the correlation pattern reflected the underlying widespread eccentricity organization of visual cortex, in which the highest correlations were observed for cortical sites with iso-eccentricity representations including regions with non-overlapping representations of visual space. This eccentricity-based correlation pattern appears to be part of an intrinsic functional architecture that supports the integration of information across functionally specialized visual areas. DOI: http://dx.doi.org/10.7554/eLife.03952.001 PMID:25695154

Blog Impossible

ERIC Educational Resources Information Center

Cole, Meryl B.; Gray, Christian L.; Romaine, Cindy A.

2012-01-01

Amid the sea change that libraries and information centers currently face, people are starting to see compelling solutions and bold initiatives from their colleagues. The challenge now becomes how to "spread the gospel"--how to inform widely dispersed information professionals about the successes they record. In 2011, volunteers within the Special…

The time-course of cortico-limbic neural responses to air hunger.

PubMed

Binks, Andrew P; Evans, Karleyton C; Reed, Jeffrey D; Moosavi, Shakeeb H; Banzett, Robert B

2014-12-01

Several studies have mapped brain regions associated with acute dyspnea perception. However, the time-course of brain activity during sustained dyspnea is unknown. Our objective was to determine the time-course of neural activity when dyspnea is sustained. Eight healthy subjects underwent brain blood oxygen level dependent functional magnetic imaging (BOLD-fMRI) during mechanical ventilation with constant mild hypercapnia (∼ 45 mm Hg). Subjects rated dyspnea (air hunger) via visual analog scale (VAS). Tidal volume (V(T)) was alternated every 90 s between high VT (0.96 ± 0.23 L) that provided respiratory comfort (12 ± 6% full scale) and low V(T) (0.48 ± 0.08 L) which evoked air hunger (56 ± 11% full scale). BOLD signal was extracted from a priori brain regions and combined with VAS data to determine air hunger related neural time-course. Air hunger onset was associated with BOLD signal increases that followed two distinct temporal profiles within sub-regions of the anterior insula, anterior cingulate and prefrontal cortices (cortico-limbic circuitry): (1) fast, BOLD signal peak <30s and (2) slow, BOLD signal peak >40s. BOLD signal during air hunger offset followed fast and slow temporal profiles symmetrical, but inverse (signal decreases) to the time-courses of air hunger onset. We conclude that differential cortico-limbic circuit elements have unique contributions to dyspnea sensation over time. We suggest that previously unidentified sub-regions are responsible for either the acute awareness or maintenance of dyspnea. These data enhance interpretation of previous studies and inform hypotheses for future dyspnea research. Copyright © 2014 Elsevier B.V. All rights reserved.

Task-related modulations of BOLD low-frequency fluctuations within the default mode network

NASA Astrophysics Data System (ADS)

Tommasin, Silvia; Mascali, Daniele; Gili, Tommaso; Eid Assan, Ibrahim; Moraschi, Marta; Fratini, Michela; Wise, Richard G.; Macaluso, Emiliano; Mangia, Silvia; Giove, Federico

2017-07-01

Spontaneous low-frequency Blood-Oxygenation Level-Dependent (BOLD) signals acquired during resting state are characterized by spatial patterns of synchronous fluctuations, ultimately leading to the identification of robust brain networks. The resting-state brain networks, including the Default Mode Network (DMN), are demonstrated to persist during sustained task execution, but the exact features of task-related changes of network properties are still not well characterized. In this work we sought to examine in a group of 20 healthy volunteers (age 33±6 years, 8F/12M) the relationship between changes of spectral and spatiotemporal features of one prominent resting-state network, namely the DMN, during the steady-state execution of a sustained working memory n-back task. We found that the steady state execution of such a task impacted on both functional connectivity and amplitude of BOLD fluctuations within large parts of the DMN, but these changes correlated between each other only in a small area of the posterior cingulate. We conclude that combined analysis of multiple parameters related to connectivity, and their changes during the transition from resting state to steady-state task execution, can contribute to a better understanding of how brain networks rearrange themselves in response of a task.

Neural Correlates Associated with Successful Working Memory Performance in Older Adults as Revealed by Spatial ICA

PubMed Central

Saliasi, Emi; Geerligs, Linda; Lorist, Monicque M.; Maurits, Natasha M.

2014-01-01

To investigate which neural correlates are associated with successful working memory performance, fMRI was recorded in healthy younger and older adults during performance on an n-back task with varying task demands. To identify functional networks supporting working memory processes, we used independent component analysis (ICA) decomposition of the fMRI data. Compared to younger adults, older adults showed a larger neural (BOLD) response in the more complex (2-back) than in the baseline (0-back) task condition, in the ventral lateral prefrontal cortex (VLPFC) and in the right fronto-parietal network (FPN). Our results indicated that a higher BOLD response in the VLPFC was associated with increased performance accuracy in older adults, in both the baseline and the more complex task condition. This ‘BOLD-performance’ relationship suggests that the neural correlates linked with successful performance in the older adults are not uniquely related to specific working memory processes present in the complex but not in the baseline task condition. Furthermore, the selective presence of this relationship in older but not in younger adults suggests that increased neural activity in the VLPFC serves a compensatory role in the aging brain which benefits task performance in the elderly. PMID:24911016

Explaining leptokurtic movement distributions: intrapopulation variation in boldness and exploration.

PubMed

Fraser, D F; Gilliam, J F; Daley, M J; Le, A N; Skalski, G T

2001-08-01

Leptokurtic distributions of movement distances observed in field-release studies, in which some individuals move long distances while most remain at or near their release point, are a common feature of mobile animals. However, because leptokurtosis is predicted to be transient in homogeneous populations, persistent leptokurtosis suggests a population heterogeneity. We found evidence for a heterogeneity that may generate persistent leptokurtosis. We tested individuals of the Trinidad killifish Rivulus hartii for boldness in a tank test and released them back into their native stream. Boldness in the tank test predicted distance moved in the field releases, even after effects of size and sex were removed. Further, data from a 19-mo mark-recapture study showed that individual growth correlated positively with movement in a predator-threatened river zone where the Rivulus population is spatially fragmented and dispersal is likely to be a hazardous activity. In contrast, no such correlation existed in a predator-absent zone where the population is unfragmented. These results show that a behavioral trait, not discernible from body size or sex, contributes to dispersal and that a component of fitness of surviving "dispersers" is elevated above that of "stayers," a fundamental assumption or prediction of many models of the evolution of dispersal through hazardous habitat.

Fast fMRI provides high statistical power in the analysis of epileptic networks.

PubMed

Jacobs, Julia; Stich, Julia; Zahneisen, Benjamin; Assländer, Jakob; Ramantani, Georgia; Schulze-Bonhage, Andreas; Korinthenberg, Rudolph; Hennig, Jürgen; LeVan, Pierre

2014-03-01

EEG-fMRI is a unique method to combine the high temporal resolution of EEG with the high spatial resolution of MRI to study generators of intrinsic brain signals such as sleep grapho-elements or epileptic spikes. While the standard EPI sequence in fMRI experiments has a temporal resolution of around 2.5-3s a newly established fast fMRI sequence called MREG (Magnetic-Resonance-Encephalography) provides a temporal resolution of around 100ms. This technical novelty promises to improve statistics, facilitate correction of physiological artifacts and improve the understanding of epileptic networks in fMRI. The present study compares simultaneous EEG-EPI and EEG-MREG analyzing epileptic spikes to determine the yield of fast MRI in the analysis of intrinsic brain signals. Patients with frequent interictal spikes (>3/20min) underwent EEG-MREG and EEG-EPI (3T, 20min each, voxel size 3×3×3mm, EPI TR=2.61s, MREG TR=0.1s). Timings of the spikes were used in an event-related analysis to generate activation maps of t-statistics. (FMRISTAT, |t|>3.5, cluster size: 7 voxels, p<0.05 corrected). For both sequences, the amplitude and location of significant BOLD activations were compared with the spike topography. 13 patients were recorded and 33 different spike types could be analyzed. Peak T-values were significantly higher in MREG than in EPI (p<0.0001). Positive BOLD effects correlating with the spike topography were found in 8/29 spike types using the EPI and in 22/33 spikes types using the MREG sequence. Negative BOLD responses in the default mode network could be observed in 3/29 spike types with the EPI and in 19/33 with the MREG sequence. With the latter method, BOLD changes were observed even when few spikes occurred during the investigation. Simultaneous EEG-MREG thus is possible with good EEG quality and shows higher sensitivity in regard to the localization of spike-related BOLD responses than EEG-EPI. The development of new methods of analysis for this sequence such as modeling of physiological noise, temporal analysis of the BOLD signal and defining appropriate thresholds is required to fully profit from its high temporal resolution. © 2013.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karen, Romero Sánchez, E-mail: alphacentauri-hp@hotmail.com, E-mail: marcos-vaquezr@hotmail.com, E-mail: isabeldgg@hotmail.com; Vásquez Reyes Marcos, A., E-mail: alphacentauri-hp@hotmail.com, E-mail: marcos-vaquezr@hotmail.com, E-mail: isabeldgg@hotmail.com; González Gómez Dulce, I., E-mail: alphacentauri-hp@hotmail.com, E-mail: marcos-vaquezr@hotmail.com, E-mail: isabeldgg@hotmail.com

The main goal of this project was to create a computer algorithm based on wavelet analysis of BOLD signals, which automatically diagnosed ADHD using information from resting state MR experiments. Male right handed volunteers (infants with ages between 7 and 11 years old) were studied and compared with age matched controls. Wavelet analysis, which is a mathematical tool used to decompose time series into elementary constituents and detect hidden information, was applied here to the BOLD signal obtained from the cerebellum 8 region of all our volunteers. Statistical differences between the values of the a parameters of wavelet analysis wasmore » found and showed significant differences (p<0.02) between groups. This difference might help in the future to distinguish healthy from ADHD patients and therefore diagnose ADHD.« less

Predation environment affects boldness temperament of neotropical livebearers.

PubMed

Rasmussen, Josh E; Belk, Mark C

2017-05-01

Behavioral traits of individuals are important phenotypes that potentially interact with many other traits, an understanding of which may illuminate the evolutionary forces affecting populations and species. Among the five axes of temperament is the propensity to behave boldly in the presence of a perceived risk. To determine the effect of different predatorial regimes on boldness and fearfulness, we assessed the behavior of individuals in a novel portable swim chamber (i.e., forced open-field test) by Brachyrhaphis rhabdophora ( n  = 633). We used an information theoretic framework to compare generalized (logistic) linear fixed-effects models of predatorial regime (predator-free [ n  = 6] and predator [ n  = 4] sites), sex, and standard length (SL). Fish from predator sites were much more fearful in the novel arena than fish from nonpredator sites. This varied by length, but not by sex. At 48 mm SL, fish from nonpredator sites were 4.9 times more likely to express bold behavior (ambulation) in the novel swim chamber as fish from predator sites. Probabilities of "ambulating" within the swim chamber increased with size for nonpredator sites and decreased with size for predator sites.

Information Technology for the Twenty-First Century: A Bold Investment in America's Future. Implementation Plan.

ERIC Educational Resources Information Center

Office of Science and Technology Policy, Washington, DC. National Science and Technology Council.

This document is the implementation plan for the Information Technology for the 21st Century (IT[squared]) initiative. With this initiative, the Federal Government is making an important re-commitment to fundamental research in information technology. The initiative proposes $366 million in increased investments in computing, information, and…

Sustained Spatial Attention to Vibrotactile Stimulation in the Flutter Range: Relevant Brain Regions and Their Interaction

PubMed Central

Goltz, Dominique; Pleger, Burkhard; Thiel, Sabrina; Villringer, Arno; Müller, Matthias M.

2013-01-01

The present functional magnetic resonance imaging (fMRI) study was designed to get a better understanding of the brain regions involved in sustained spatial attention to tactile events and to ascertain to what extent their activation was correlated. We presented continuous 20 Hz vibrotactile stimuli (range of flutter) concurrently to the left and right index fingers of healthy human volunteers. An arrow cue instructed subjects in a trial-by-trial fashion to attend to the left or right index finger and to detect rare target events that were embedded in the vibrotactile stimulation streams. We found blood oxygen level-dependent (BOLD) attentional modulation in primary somatosensory cortex (SI), mainly covering Brodmann area 1, 2, and 3b, as well as in secondary somatosensory cortex (SII), contralateral to the to-be-attended hand. Furthermore, attention to the right (dominant) hand resulted in additional BOLD modulation in left posterior insula. All of the effects were caused by an increased activation when attention was paid to the contralateral hand, except for the effects in left SI and insula. In left SI, the effect was related to a mixture of both a slight increase in activation when attention was paid to the contralateral hand as well as a slight decrease in activation when attention was paid to the ipsilateral hand (i.e., the tactile distraction condition). In contrast, the effect in left posterior insula was exclusively driven by a relative decrease in activation in the tactile distraction condition, which points to an active inhibition when tactile information is irrelevant. Finally, correlation analyses indicate a linear relationship between attention effects in intrahemispheric somatosensory cortices, since attentional modulation in SI and SII were interrelated within one hemisphere but not across hemispheres. All in all, our results provide a basis for future research on sustained attention to continuous vibrotactile stimulation in the range of flutter. PMID:24367642

Age-associated patterns in gray matter volume, cerebral perfusion and BOLD oscillations in children and adolescents.

PubMed

Bray, Signe

2017-05-01

Healthy brain development involves changes in brain structure and function that are believed to support cognitive maturation. However, understanding how structural changes such as grey matter thinning relate to functional changes is challenging. To gain insight into structure-function relationships in development, the present study took a data driven approach to define age-related patterns of variation in gray matter volume (GMV), cerebral blood flow (CBF) and blood-oxygen level dependent (BOLD) signal variation (fractional amplitude of low-frequency fluctuations; fALFF) in 59 healthy children aged 7-18 years, and examined relationships between modalities. Principal components analysis (PCA) was applied to each modality in parallel, and participant scores for the top components were assessed for age associations. We found that decompositions of CBF, GMV and fALFF all included components for which scores were significantly associated with age. The dominant patterns in GMV and CBF showed significant (GMV) or trend level (CBF) associations with age and a strong spatial overlap, driven by increased signal intensity in default mode network (DMN) regions. GMV, CBF and fALFF additionally showed components accounting for 3-5% of variability with significant age associations. However, these patterns were relatively spatially independent, with small-to-moderate overlap between modalities. Independence of age effects was further demonstrated by correlating individual subject maps between modalities: CBF was significantly less correlated with GMV and fALFF in older children relative to younger. These spatially independent effects of age suggest that the parallel decline observed in global GMV and CBF may not reflect spatially synchronized processes. Hum Brain Mapp 38:2398-2407, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Magnetic susceptibility induced echo time shifts: Is there a bias in age-related fMRI studies?

PubMed Central

Ngo, Giang-Chau; Wong, Chelsea N.; Guo, Steve; Paine, Thomas; Kramer, Arthur F.; Sutton, Bradley P.

2016-01-01

Purpose To evaluate the potential for bias in functional MRI (fMRI) aging studies resulting from age-related differences in magnetic field distributions which can impact echo time and functional contrast. Materials and Methods Magnetic field maps were taken on 31 younger adults (age: 22 ± 2.9 years) and 46 older adults (age: 66 ± 4.5 years) on a 3 T scanner. Using the spatial gradients of the magnetic field map for each participant, an echo planar imaging (EPI) trajectory was simulated. The effective echo time, time at which the k-space trajectory is the closest to the center of k-space, was calculated. This was used to examine both within-subject and across-age-group differences in the effective echo time maps. The Blood Oxygenation Level Dependent (BOLD) percent signal change resulting from those echo time shifts was also calculated to determine their impact on fMRI aging studies. Result For a single subject, the effective echo time varied as much as ± 5 ms across the brain. An unpaired t-test between the effective echo time across age group resulted in significant differences in several regions of the brain (p<0.01). The difference in echo time was only approximately 1 ms, however which is not expected to have an important impact on BOLD fMRI percent signal change (< 4%). Conclusion Susceptibility-induced magnetic field gradients induce local echo time shifts in gradient echo fMRI images, which can cause variable BOLD sensitivity across the brain. However, the age-related differences in BOLD signal are expected to be small for an fMRI study at 3 T. PMID:27299727

Against Boldness

ERIC Educational Resources Information Center

Kennedy, Mary M.

2010-01-01

This special issue, "Bold Ideas for a New Era in Teacher Education, Teacher Preparation, and Teacher Practice," seeks to examine the impact of bold ideas on our field. Authors were asked to propose particular bold ideas that they wanted to examine. I proposed to examine the concept of bold ideas itself. In this article, I challenge the notion that…

Functional Neuroanatomy Involved in Automatic order Mental Arithmetic and Recitation of the Multiplication Table

NASA Astrophysics Data System (ADS)

Wang, Li-Qun; Saito, Masao

We used 1.5T functional magnetic resonance imaging (fMRI) to explore that which brain areas contribute uniquely to numeric computation. The BOLD effect activation pattern of metal arithmetic task (successive subtraction: actual calculation task) was compared with multiplication tables repetition task (rote verbal arithmetic memory task) response. The activation found in right parietal lobule during metal arithmetic task suggested that quantitative cognition or numeric computation may need the assistance of sensuous convert, such as spatial imagination and spatial sensuous convert. In addition, this mechanism may be an ’analog algorithm’ in the simple mental arithmetic processing.

Monkey cortex through fMRI glasses

PubMed Central

Vanduffel, Wim; Zhu, Qi; Orban, Guy A.

2015-01-01

In 1998 several groups reported the feasibility of functional magnetic resonance imaging (fMRI) experiments in monkeys, with the goal to bridge the gap between invasive nonhuman primate studies and human functional imaging. These studies yielded critical insights in the neuronal underpinnings of the BOLD signal. Furthermore, the technology has been successful in guiding electrophysiological recordings and identifying focal perturbation targets. Finally, invaluable information was obtained concerning human brain evolution. We here provide a comprehensive overview of awake monkey fMRI studies mainly confined to the visual system. We review the latest insights about the topographic organization of monkey visual cortex and discuss the spatial relationships between retinotopy and category and feature selective clusters. We briefly discuss the functional layout of parietal and frontal cortex and continue with a summary of some fascinating functional and effective connectivity studies. Finally, we review recent comparative fMRI experiments and speculate about the future of nonhuman primate imaging. PMID:25102559

Monkey cortex through fMRI glasses.

PubMed

Vanduffel, Wim; Zhu, Qi; Orban, Guy A

2014-08-06

In 1998 several groups reported the feasibility of fMRI experiments in monkeys, with the goal to bridge the gap between invasive nonhuman primate studies and human functional imaging. These studies yielded critical insights in the neuronal underpinnings of the BOLD signal. Furthermore, the technology has been successful in guiding electrophysiological recordings and identifying focal perturbation targets. Finally, invaluable information was obtained concerning human brain evolution. We here provide a comprehensive overview of awake monkey fMRI studies mainly confined to the visual system. We review the latest insights about the topographic organization of monkey visual cortex and discuss the spatial relationships between retinotopy and category- and feature-selective clusters. We briefly discuss the functional layout of parietal and frontal cortex and continue with a summary of some fascinating functional and effective connectivity studies. Finally, we review recent comparative fMRI experiments and speculate about the future of nonhuman primate imaging. Copyright © 2014 Elsevier Inc. All rights reserved.

Fractal Analysis of Brain Blood Oxygenation Level Dependent (BOLD) Signals from Children with Mild Traumatic Brain Injury (mTBI).

PubMed

Dona, Olga; Noseworthy, Michael D; DeMatteo, Carol; Connolly, John F

2017-01-01

Conventional imaging techniques are unable to detect abnormalities in the brain following mild traumatic brain injury (mTBI). Yet patients with mTBI typically show delayed response on neuropsychological evaluation. Because fractal geometry represents complexity, we explored its utility in measuring temporal fluctuations of brain resting state blood oxygen level dependent (rs-BOLD) signal. We hypothesized that there could be a detectable difference in rs-BOLD signal complexity between healthy subjects and mTBI patients based on previous studies that associated reduction in signal complexity with disease. Fifteen subjects (13.4 ± 2.3 y/o) and 56 age-matched (13.5 ± 2.34 y/o) healthy controls were scanned using a GE Discovery MR750 3T MRI and 32-channel RF-coil. Axial FSPGR-3D images were used to prescribe rs-BOLD (TE/TR = 35/2000ms), acquired over 6 minutes. Motion correction was performed and anatomical and functional images were aligned and spatially warped to the N27 standard atlas. Fractal analysis, performed on grey matter, was done by estimating the Hurst exponent using de-trended fluctuation analysis and signal summation conversion methods. Voxel-wise fractal dimension (FD) was calculated for every subject in the control group to generate mean and standard deviation maps for regional Z-score analysis. Voxel-wise validation of FD normality across controls was confirmed, and non-Gaussian voxels (3.05% over the brain) were eliminated from subsequent analysis. For each mTBI patient, regions where Z-score values were at least 2 standard deviations away from the mean (i.e. where |Z| > 2.0) were identified. In individual patients the frequently affected regions were amygdala (p = 0.02), vermis(p = 0.03), caudate head (p = 0.04), hippocampus(p = 0.03), and hypothalamus(p = 0.04), all previously reported as dysfunctional after mTBI, but based on group analysis. It is well known that the brain is best modeled as a complex system. Therefore a measure of complexity using rs-BOLD signal FD could provide an additional method to grade and monitor mTBI. Furthermore, this approach can be personalized thus providing unique patient specific assessment.

Wavelet analysis of MR functional data from the cerebellum

NASA Astrophysics Data System (ADS)

Romero Sánchez, Karen; Vásquez Reyes, Marcos A.; González Gómez, Dulce I.; Hidalgo Tobón, Silvia; Hernández López, Javier M.; Dies Suarez, Pilar; Barragán Pérez, Eduardo; De Celis Alonso, Benito

2014-11-01

The main goal of this project was to create a computer algorithm based on wavelet analysis of BOLD signals, which automatically diagnosed ADHD using information from resting state MR experiments. Male right handed volunteers (infants with ages between 7 and 11 years old) were studied and compared with age matched controls. Wavelet analysis, which is a mathematical tool used to decompose time series into elementary constituents and detect hidden information, was applied here to the BOLD signal obtained from the cerebellum 8 region of all our volunteers. Statistical differences between the values of the a parameters of wavelet analysis was found and showed significant differences (p<0.02) between groups. This difference might help in the future to distinguish healthy from ADHD patients and therefore diagnose ADHD.

Examining the incremental and interactive effects of boldness with meanness and disinhibition within the triarchic model of psychopathy.

PubMed

Gatner, Dylan T; Douglas, Kevin S; Hart, Stephen D

2016-07-01

The triarchic model of psychopathy (Patrick, Fowles, & Krueger, 2009) comprises 3 phenotypic domains: Meanness, Disinhibition, and Boldness. Ongoing controversy surrounds the relevance of Boldness in the conceptualization and assessment of psychopathy. In the current study, undergraduate students (N = 439) completed the Triarchic Psychopathy Measure (Patrick, 2010) to examine the association between Boldness and a host of theoretically relevant external criteria. Boldness was generally unrelated to either prosocial or harmful criteria. Boldness rarely provided incremental value above or interacted with Meanness and Disinhibition with respect to external criteria. Curvilinear effects of Boldness rarely emerged. The findings suggest that Boldness might not be a central construct in the definition of psychopathic personality disorder. Implications for the 5th edition of the Diagnostic and Statistical Manual of Mental Disorders (American Psychiatric Association, 2013) psychopathic specifier are discussed. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Phenotypic assortment in wild primate networks: implications for the dissemination of information.

PubMed

Carter, Alecia J; Lee, Alexander E G; Marshall, Harry H; Ticó, Miquel Torrents; Cowlishaw, Guy

2015-05-01

Individuals' access to social information can depend on their social network. Homophily-a preference to associate with similar phenotypes-may cause assortment within social networks that could preclude information transfer from individuals who generate information to those who would benefit from acquiring it. Thus, understanding phenotypic assortment may lead to a greater understanding of the factors that could limit the transfer of information between individuals. We tested whether there was assortment in wild baboon (Papio ursinus) networks, using data collected from two troops over 6 years for six phenotypic traits-boldness, age, dominance rank, sex and the propensity to generate/exploit information-using two methods for defining a connection between individuals-time spent in proximity and grooming. Our analysis indicated that assortment was more common in grooming than proximity networks. In general, there was homophily for boldness, age, rank and the propensity to both generate and exploit information, but heterophily for sex. However, there was considerable variability both between troops and years. The patterns of homophily we observed for these phenotypes may impede information transfer between them. However, the inconsistency in the strength of assortment between troops and years suggests that the limitations to information flow may be quite variable.

Scale invariant rearrangement of resting state networks in the human brain under sustained stimulation.

PubMed

Tommasin, Silvia; Mascali, Daniele; Moraschi, Marta; Gili, Tommaso; Assan, Ibrahim Eid; Fratini, Michela; DiNuzzo, Mauro; Wise, Richard G; Mangia, Silvia; Macaluso, Emiliano; Giove, Federico

2018-06-14

Brain activity at rest is characterized by widely distributed and spatially specific patterns of synchronized low-frequency blood-oxygenation level-dependent (BOLD) fluctuations, which correspond to physiologically relevant brain networks. This network behaviour is known to persist also during task execution, yet the details underlying task-associated modulations of within- and between-network connectivity are largely unknown. In this study we exploited a multi-parametric and multi-scale approach to investigate how low-frequency fluctuations adapt to a sustained n-back working memory task. We found that the transition from the resting state to the task state involves a behaviourally relevant and scale-invariant modulation of synchronization patterns within both task-positive and default mode networks. Specifically, decreases of connectivity within networks are accompanied by increases of connectivity between networks. In spite of large and widespread changes of connectivity strength, the overall topology of brain networks is remarkably preserved. We show that these findings are strongly influenced by connectivity at rest, suggesting that the absolute change of connectivity (i.e., disregarding the baseline) may be not the most suitable metric to study dynamic modulations of functional connectivity. Our results indicate that a task can evoke scale-invariant, distributed changes of BOLD fluctuations, further confirming that low frequency BOLD oscillations show a specialized response and are tightly bound to task-evoked activation. Copyright © 2018. Published by Elsevier Inc.

Non-neural BOLD variability in block and event-related paradigms.

PubMed

Kannurpatti, Sridhar S; Motes, Michael A; Rypma, Bart; Biswal, Bharat B

2011-01-01

Block and event-related stimulus designs are typically used in fMRI studies depending on the importance of detection power or estimation efficiency. The extent of vascular contribution to variability in block and event-related fMRI-BOLD response is not known. With scaling, the extent of vascular variability in the fMRI-BOLD response during block and event-related design tasks was investigated. Blood oxygen level-dependent (BOLD) contrast data from healthy volunteers performing a block design motor task and an event-related memory task requiring performance of a motor response were analyzed from the regions of interest (ROIs) surrounding the primary and supplementary motor cortices. Average BOLD signal change was significantly larger during the block design compared to the event-related design. In each subject, BOLD signal change across voxels in the ROIs had higher variation during the block design task compared to the event-related design task. Scaling using the resting state fluctuation of amplitude (RSFA) and breath-hold (BH), which minimizes BOLD variation due to vascular origins, reduced the within-subject BOLD variability in every subject during both tasks but significantly reduced BOLD variability across subjects only during the block design task. The strong non-neural source of intra- and intersubject variability of BOLD response during the block design compared to event-related task indicates that study designs optimizing for statistical power through enhancement of the BOLD contrast (for, e.g., block design) can be affected by enhancement of non-neural sources of BOLD variability. Copyright © 2011. Published by Elsevier Inc.

Quantifying Trust, Distrust, and Suspicion in Human-System Interactions

DTIC Science & Technology

2015-10-26

devices which require subjects to lie in restricted positions ( fMRI ), or to drink hazardous materials (PET), EEG and fNIRS can non-invasively measure... fMRI . Since fNIRS and fMRI both measure elements of the Blood Oxygen Level Dependent (BOLD) signal. Researchers have recently explored the...response inhibition load, verbal working memory load, and spatial working memory load [1, 7]. We have also successfully localized brain regions such as

The neural correlates of volitional attention: A combined fMRI and ERP study.

PubMed

Bengson, Jesse J; Kelley, Todd A; Mangun, George R

2015-07-01

Studies of visual-spatial attention typically use instructional cues to direct attention to a relevant location, but in everyday vision, attention is often focused volitionally, in the absence of external signals. Although investigations of cued attention comprise hundreds of behavioral and physiological studies, remarkably few studies of voluntary attention have addressed the challenging question of how spatial attention is initiated and controlled in the absence of external instructions, which we refer to as willed attention. To explore this question, we employed a trial-by-trial spatial attention task using electroencephalography and functional magnetic resonance imaging (fMRI). The fMRI results reveal a unique network of brain regions for willed attention that includes the anterior cingulate cortex, left middle frontal gyrus (MFG), and the left and right anterior insula (AI). We also observed two event-related potentials (ERPs) associated with willed attention; one with a frontal distribution occurring 250-350 ms postdecision cue onset (EWAC: Early Willed Attention Component), and another occurring between 400 and 800 ms postdecision-cue onset (WAC: Willed Attention Component). In addition, each ERP component uniquely correlated across subjects with different willed attention-specific sites of BOLD activation. The EWAC was correlated with the willed attention-specific left AI and left MFG activations and the later WAC was correlated only with left AI. These results offer a comprehensive and novel view of the electrophysiological and anatomical profile of willed attention and further illustrate the relationship between scalp-recorded ERPs and the BOLD response. © 2015 Wiley Periodicals, Inc.

Audiovisual synchrony enhances BOLD responses in a brain network including multisensory STS while also enhancing target-detection performance for both modalities

PubMed Central

Marchant, Jennifer L; Ruff, Christian C; Driver, Jon

2012-01-01

The brain seeks to combine related inputs from different senses (e.g., hearing and vision), via multisensory integration. Temporal information can indicate whether stimuli in different senses are related or not. A recent human fMRI study (Noesselt et al. [2007]: J Neurosci 27:11431–11441) used auditory and visual trains of beeps and flashes with erratic timing, manipulating whether auditory and visual trains were synchronous or unrelated in temporal pattern. A region of superior temporal sulcus (STS) showed higher BOLD signal for the synchronous condition. But this could not be related to performance, and it remained unclear if the erratic, unpredictable nature of the stimulus trains was important. Here we compared synchronous audiovisual trains to asynchronous trains, while using a behavioral task requiring detection of higher-intensity target events in either modality. We further varied whether the stimulus trains had predictable temporal pattern or not. Synchrony (versus lag) between auditory and visual trains enhanced behavioral sensitivity (d') to intensity targets in either modality, regardless of predictable versus unpredictable patterning. The analogous contrast in fMRI revealed BOLD increases in several brain areas, including the left STS region reported by Noesselt et al. [2007: J Neurosci 27:11431–11441]. The synchrony effect on BOLD here correlated with the subject-by-subject impact on performance. Predictability of temporal pattern did not affect target detection performance or STS activity, but did lead to an interaction with audiovisual synchrony for BOLD in inferior parietal cortex. PMID:21953980

Functional magnetic resonance imaging.

PubMed

Buchbinder, Bradley R

2016-01-01

Functional magnetic resonance imaging (fMRI) maps the spatiotemporal distribution of neural activity in the brain under varying cognitive conditions. Since its inception in 1991, blood oxygen level-dependent (BOLD) fMRI has rapidly become a vital methodology in basic and applied neuroscience research. In the clinical realm, it has become an established tool for presurgical functional brain mapping. This chapter has three principal aims. First, we review key physiologic, biophysical, and methodologic principles that underlie BOLD fMRI, regardless of its particular area of application. These principles inform a nuanced interpretation of the BOLD fMRI signal, along with its neurophysiologic significance and pitfalls. Second, we illustrate the clinical application of task-based fMRI to presurgical motor, language, and memory mapping in patients with lesions near eloquent brain areas. Integration of BOLD fMRI and diffusion tensor white-matter tractography provides a road map for presurgical planning and intraoperative navigation that helps to maximize the extent of lesion resection while minimizing the risk of postoperative neurologic deficits. Finally, we highlight several basic principles of resting-state fMRI and its emerging translational clinical applications. Resting-state fMRI represents an important paradigm shift, focusing attention on functional connectivity within intrinsic cognitive networks. © 2016 Elsevier B.V. All rights reserved.

Shy herbivores forage more efficiently than bold ones regardless of information-processing overload.

PubMed

Tan, Ming Kai; Chang, Chia-Chen; Tan, Hugh T W

2018-04-01

The neural constraint hypothesis is central to understanding decision-making by foraging herbivorous insects which make decisions less efficiently when they face multiple choices for numerous resource types and/or at high densities instead of a fewer choices. Previous studies have also shown the relationship between personality type and decision-making style. How personality types correlate with foraging efficiency among herbivores is however, largely untested. To answer this question, we used a widespread, polyphagous, floriphilic katydid, Phaneroptera brevis (Orthoptera: Tettigoniidae) and two naturalised, Asteraceae, food plants, Bidens pilosa and Sphagneticola trilobata, as model systems. After we determined each katydid's exploration and boldness levels, we examined its foraging efficiency across different combinations of floral resource choice and density. We showed: (1) For the first time within the Tettigonioidea lineage that this katydid exhibits different personality types in exploration and boldness. (2) Contrary to our prediction, we did not find any support for the neural constraint hypothesis because more floral resource choice at a high density did not reduce foraging efficiency. (3) Surprisingly, bold katydids tend to be less efficient foragers than shy ones. Our findings have enhanced understanding of herbivore behavioural ecology and knowledge to better deal with potential pest herbivores. Copyright © 2018 Elsevier B.V. All rights reserved.

16 CFR 1130.6 - Requirements for format of registration forms.

Code of Federal Regulations, 2010 CFR

2010-01-01

... manufacturer's name and mailing address where registration information is to be collected. (c) Font size and typeface. The registration form shall use bold black typeface. The size of the type shall be at least 12... information shall be in capital and lower case type. ...

Global signal modulation of single-trial fMRI response variability: Effect on positive vs negative BOLD response relationship.

PubMed

Mayhew, S D; Mullinger, K J; Ostwald, D; Porcaro, C; Bowtell, R; Bagshaw, A P; Francis, S T

2016-06-01

In functional magnetic resonance imaging (fMRI), the relationship between positive BOLD responses (PBRs) and negative BOLD responses (NBRs) to stimulation is potentially informative about the balance of excitatory and inhibitory brain responses in sensory cortex. In this study, we performed three separate experiments delivering visual, motor or somatosensory stimulation unilaterally, to one side of the sensory field, to induce PBR and NBR in opposite brain hemispheres. We then assessed the relationship between the evoked amplitudes of contralateral PBR and ipsilateral NBR at the level of both single-trial and average responses. We measure single-trial PBR and NBR peak amplitudes from individual time-courses, and show that they were positively correlated in all experiments. In contrast, in the average response across trials the absolute magnitudes of both PBR and NBR increased with increasing stimulus intensity, resulting in a negative correlation between mean response amplitudes. Subsequent analysis showed that the amplitude of single-trial PBR was positively correlated with the BOLD response across all grey-matter voxels and was not specifically related to the ipsilateral sensory cortical response. We demonstrate that the global component of this single-trial response modulation could be fully explained by voxel-wise vascular reactivity, the BOLD signal standard deviation measured in a separate resting-state scan (resting state fluctuation amplitude, RSFA). However, bilateral positive correlation between PBR and NBR regions remained. We further report that modulations in the global brain fMRI signal cannot fully account for this positive PBR-NBR coupling and conclude that the local sensory network response reflects a combination of superimposed vascular and neuronal signals. More detailed quantification of physiological and noise contributions to the BOLD signal is required to fully understand the trial-by-trial PBR and NBR relationship compared with that of average responses. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

Network complexity as a measure of information processing across resting-state networks: evidence from the Human Connectome Project

PubMed Central

McDonough, Ian M.; Nashiro, Kaoru

2014-01-01

An emerging field of research focused on fluctuations in brain signals has provided evidence that the complexity of those signals, as measured by entropy, conveys important information about network dynamics (e.g., local and distributed processing). While much research has focused on how neural complexity differs in populations with different age groups or clinical disorders, substantially less research has focused on the basic understanding of neural complexity in populations with young and healthy brain states. The present study used resting-state fMRI data from the Human Connectome Project (Van Essen et al., 2013) to test the extent that neural complexity in the BOLD signal, as measured by multiscale entropy (1) would differ from random noise, (2) would differ between four major resting-state networks previously associated with higher-order cognition, and (3) would be associated with the strength and extent of functional connectivity—a complementary method of estimating information processing. We found that complexity in the BOLD signal exhibited different patterns of complexity from white, pink, and red noise and that neural complexity was differentially expressed between resting-state networks, including the default mode, cingulo-opercular, left and right frontoparietal networks. Lastly, neural complexity across all networks was negatively associated with functional connectivity at fine scales, but was positively associated with functional connectivity at coarse scales. The present study is the first to characterize neural complexity in BOLD signals at a high temporal resolution and across different networks and might help clarify the inconsistencies between neural complexity and functional connectivity, thus informing the mechanisms underlying neural complexity. PMID:24959130

Integration of EEG source imaging and fMRI during continuous viewing of natural movies.

PubMed

Whittingstall, Kevin; Bartels, Andreas; Singh, Vanessa; Kwon, Soyoung; Logothetis, Nikos K

2010-10-01

Electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) are noninvasive neuroimaging tools which can be used to measure brain activity with excellent temporal and spatial resolution, respectively. By combining the neural and hemodynamic recordings from these modalities, we can gain better insight into how and where the brain processes complex stimuli, which may be especially useful in patients with different neural diseases. However, due to their vastly different spatial and temporal resolutions, the integration of EEG and fMRI recordings is not always straightforward. One fundamental obstacle has been that paradigms used for EEG experiments usually rely on event-related paradigms, while fMRI is not limited in this regard. Therefore, here we ask whether one can reliably localize stimulus-driven EEG activity using the continuously varying feature intensities occurring in natural movie stimuli presented over relatively long periods of time. Specifically, we asked whether stimulus-driven aspects in the EEG signal would be co-localized with the corresponding stimulus-driven BOLD signal during free viewing of a movie. Secondly, we wanted to integrate the EEG signal directly with the BOLD signal, by estimating the underlying impulse response function (IRF) that relates the BOLD signal to the underlying current density in the primary visual area (V1). We made sequential fMRI and 64-channel EEG recordings in seven subjects who passively watched 2-min-long segments of a James Bond movie. To analyze EEG data in this natural setting, we developed a method based on independent component analysis (ICA) to reject EEG artifacts due to blinks, subject movement, etc., in a way unbiased by human judgment. We then calculated the EEG source strength of this artifact-free data at each time point of the movie within the entire brain volume using low-resolution electromagnetic tomography (LORETA). This provided for every voxel in the brain (i.e., in 3D space) an estimate of the current density at every time point. We then carried out a correlation between the time series of visual contrast changes in the movie with that of EEG voxels. We found the most significant correlations in visual area V1, just as seen in previous fMRI studies (Bartels A, Zeki, S, Logothetis NK. Natural vision reveals regional specialization to local motion and to contrast-invariant, global flow in the human brain. Cereb Cortex 2008;18(3):705-717), but on the time scale of milliseconds rather than of seconds. To obtain an estimate of how the EEG signal relates to the BOLD signal, we calculated the IRF between the BOLD signal and the estimated current density in area V1. We found that this IRF was very similar to that observed using combined intracortical recordings and fMRI experiments in nonhuman primates. Taken together, these findings open a new approach to noninvasive mapping of the brain. It allows, firstly, the localization of feature-selective brain areas during natural viewing conditions with the temporal resolution of EEG. Secondly, it provides a tool to assess EEG/BOLD transfer functions during processing of more natural stimuli. This is especially useful in combined EEG/fMRI experiments, where one can now potentially study neural-hemodynamic relationships across the whole brain volume in a noninvasive manner. Copyright © 2010 Elsevier Inc. All rights reserved.

A second-order orientation-contrast stimulus for population-receptive-field-based retinotopic mapping.

PubMed

Yildirim, Funda; Carvalho, Joana; Cornelissen, Frans W

2018-01-01

Visual field or retinotopic mapping is one of the most frequently used paradigms in fMRI. It uses activity evoked by position-varying high luminance contrast visual patterns presented throughout the visual field for determining the spatial organization of cortical visual areas. While the advantage of using high luminance contrast is that it tends to drive a wide range of neural populations - thus resulting in high signal-to-noise BOLD responses - this may also be a limitation, especially for approaches that attempt to squeeze more information out of the BOLD response, such as population receptive field (pRF) mapping. In that case, more selective stimulation of a subset of neurons - despite reduced signals - could result in better characterization of pRF properties. Here, we used a second-order stimulus based on local differences in orientation texture - to which we refer as orientation contrast - to perform retinotopic mapping. Participants in our experiment viewed arrays of Gabor patches composed of a foreground (a bar) and a background. These could only be distinguished on the basis of a difference in patch orientation. In our analyses, we compare the pRF properties obtained using this new orientation contrast-based retinotopy (OCR) to those obtained using classic luminance contrast-based retinotopy (LCR). Specifically, in higher order cortical visual areas such as LO, our novel approach resulted in non-trivial reductions in estimated population receptive field size of around 30%. A set of control experiments confirms that the most plausible cause for this reduction is that OCR mainly drives neurons sensitive to orientation contrast. We discuss how OCR - by limiting receptive field scatter and reducing BOLD displacement - may result in more accurate pRF localization as well. Estimation of neuronal properties is crucial for interpreting cortical function. Therefore, we conclude that using our approach, it is possible to selectively target particular neuronal populations, opening the way to use pRF modeling to dissect the response properties of more clearly-defined neuronal populations in different visual areas. Copyright © 2017 Elsevier Inc. All rights reserved.

Quantification of oxygen changes in the placenta from BOLD MR image sequences

NASA Astrophysics Data System (ADS)

Porras, Antonio R.; Piella, Gemma; You, Wonsang; Limperopoulos, Catherine; Linguraru, Marius George

2017-03-01

Functional analysis of the placenta is important to analyze and understand its role in fetal growth and development. BOLD MR is a non-invasive technique that has been extensively used for functional analysis of the brain. During the last years, several studies have shown that this dynamic image modality is also useful to extract functional information of the placenta. We propose in this paper a method to track the placenta from a sequence of BOLD MR images acquired under normoxia and hyperoxia conditions with the goal of quantifying how the placenta adapts to oxygenation changes. The method is based on a spatiotemporal transformation model that ensures temporal coherence of the tracked structures. The method was initially applied to four patients with healthy pregnancies. An average MR signal increase of 16.96+/-8.39% during hyperoxia was observed. These automated results are in line with state-of-the-art reports using time-consuming manual segmentations subject to inter-observer errors.

Sex differences in a shoaling-boldness behavioral syndrome, but no link with aggression.

PubMed

Way, Gregory P; Kiesel, Alexis L; Ruhl, Nathan; Snekser, Jennifer L; McRobert, Scott P

2015-04-01

A behavioral syndrome is observed in a population when specific behaviors overlap at the individual level in different contexts. Here, we explore boldness and aggression personality spectra, the repeatability of shoaling, and possible associated correlations between the behaviors in a population of lab-reared zebrafish (Danio rerio). Our findings describe a sex-specific boldness-shoaling behavioral syndrome, as a link between boldness and shoaling behaviors is detected. The results indicate that bold males are likely to have a stronger shoaling propensity than shy males for unfamiliar conspecifics. Conversely, bold females are more likely to shoal than shy females, but only when presented with heterospecific individuals. Additionally, aggression does not correlate with boldness or shoaling propensity for either sex. A positive relationship between boldness and shoaling that differs by sex is contrary to most of the present literature, but could help to explain population dynamics and may also have evolutionary implications. Copyright © 2015 Elsevier B.V. All rights reserved.

The neural representation of objects formed through the spatiotemporal integration of visual transients

PubMed Central

Erlikhman, Gennady; Gurariy, Gennadiy; Mruczek, Ryan E.B.; Caplovitz, Gideon P.

2016-01-01

Oftentimes, objects are only partially and transiently visible as parts of them become occluded during observer or object motion. The visual system can integrate such object fragments across space and time into perceptual wholes or spatiotemporal objects. This integrative and dynamic process may involve both ventral and dorsal visual processing pathways, along which shape and spatial representations are thought to arise. We measured fMRI BOLD response to spatiotemporal objects and used multi-voxel pattern analysis (MVPA) to decode shape information across 20 topographic regions of visual cortex. Object identity could be decoded throughout visual cortex, including intermediate (V3A, V3B, hV4, LO1-2,) and dorsal (TO1-2, and IPS0-1) visual areas. Shape-specific information, therefore, may not be limited to early and ventral visual areas, particularly when it is dynamic and must be integrated. Contrary to the classic view that the representation of objects is the purview of the ventral stream, intermediate and dorsal areas may play a distinct and critical role in the construction of object representations across space and time. PMID:27033688

Suppressive and enhancing effects in early visual cortex during illusory shape perception: A comment on.

PubMed

Moors, Pieter

2015-01-01

In a recent functional magnetic resonance imaging study, Kok and de Lange (2014) observed that BOLD activity for a Kanizsa illusory shape stimulus, in which pacmen-like inducers elicit an illusory shape percept, was either enhanced or suppressed relative to a nonillusory control configuration depending on whether the spatial profile of BOLD activity in early visual cortex was related to the illusory shape or the inducers, respectively. The authors argued that these findings fit well with the predictive coding framework, because top-down predictions related to the illusory shape are not met with bottom-up sensory input and hence the feedforward error signal is enhanced. Conversely, for the inducing elements, there is a match between top-down predictions and input, leading to a decrease in error. Rather than invoking predictive coding as the explanatory framework, the suppressive effect related to the inducers might be caused by neural adaptation to perceptually stable input due to the trial sequence used in the experiment.

Role of Prefrontal Persistent Activity in Working Memory

PubMed Central

Riley, Mitchell R.; Constantinidis, Christos

2016-01-01

The prefrontal cortex is activated during working memory, as evidenced by fMRI results in human studies and neurophysiological recordings in animal models. Persistent activity during the delay period of working memory tasks, after the offset of stimuli that subjects are required to remember, has traditionally been thought of as the neural correlate of working memory. In the last few years several findings have cast doubt on the role of this activity. By some accounts, activity in other brain areas, such as the primary visual and posterior parietal cortex, is a better predictor of information maintained in visual working memory and working memory performance; dynamic patterns of activity may convey information without requiring persistent activity at all; and prefrontal neurons may be ill-suited to represent non-spatial information about the features and identity of remembered stimuli. Alternative interpretations about the role of the prefrontal cortex have thus been suggested, such as that it provides a top-down control of information represented in other brain areas, rather than maintaining a working memory trace itself. Here we review evidence for and against the role of prefrontal persistent activity, with a focus on visual neurophysiology. We show that persistent activity predicts behavioral parameters precisely in working memory tasks. We illustrate that prefrontal cortex represents features of stimuli other than their spatial location, and that this information is largely absent from early cortical areas during working memory. We examine memory models not dependent on persistent activity, and conclude that each of those models could mediate only a limited range of memory-dependent behaviors. We review activity decoded from brain areas other than the prefrontal cortex during working memory and demonstrate that these areas alone cannot mediate working memory maintenance, particularly in the presence of distractors. We finally discuss the discrepancy between BOLD activation and spiking activity findings, and point out that fMRI methods do not currently have the spatial resolution necessary to decode information within the prefrontal cortex, which is likely organized at the micrometer scale. Therefore, we make the case that prefrontal persistent activity is both necessary and sufficient for the maintenance of information in working memory. PMID:26778980

Controlled inspiration depth reduces variance in breath-holding-induced BOLD signal.

PubMed

Thomason, Moriah E; Glover, Gary H

2008-01-01

Recent studies have shown that blood oxygen level dependent (BOLD) response amplitude during short periods of breath holding (BH) measured by functional magnetic resonance imaging (fMRI) can be an effective metric for intersubject calibration procedures. However, inconsistency in the depth of inspiration during the BH scan may account for a portion of BOLD variation observed in such scans, and it is likely to reduce the effectiveness of the calibration measurement. While modulation of BOLD signal has been correlated with end-tidal CO2 and other measures of breathing, fluctuations in performance of BH have not been studied in the context of their impact on BOLD signal. Here, we studied the degree to which inspiration depth corresponds to BOLD signal change and tested the effectiveness of a method designed to control inspiration level through visual cues during the BH task paradigm. We observed reliable differences in BOLD signal amplitude corresponding to the depth of inspiration. It was determined that variance in BOLD signal response to BH could be significantly reduced when subjects were given visual feedback during task inspiration periods. The implications of these findings for routine BH studies of BOLD-derived neurovascular response are discussed.

16 CFR 429.1 - The Rule.

Code of Federal Regulations, 2010 CFR

2010-01-01

..., which is in the same language, e.g., Spanish, as that principally used in the oral sales presentation... ten point bold face type the following information and statements in the same language, e.g., Spanish...

16 CFR 437.1 - The Rule.

Code of Federal Regulations, 2011 CFR

2011-01-01

... formula and whether there will be a recognition of goodwill or other intangibles associated therewith in... imprinted thereon in upper and lower case bold-face type of not less than 12 point size: Information for...

16 CFR 437.1 - The Rule.

Code of Federal Regulations, 2012 CFR

2012-01-01

... formula and whether there will be a recognition of goodwill or other intangibles associated therewith in... imprinted thereon in upper and lower case bold-face type of not less than 12 point size: Information for...

From blood oxygenation level dependent (BOLD) signals to brain temperature maps.

PubMed

Sotero, Roberto C; Iturria-Medina, Yasser

2011-11-01

A theoretical framework is presented for converting Blood Oxygenation Level Dependent (BOLD) images to brain temperature maps, based on the idea that disproportional local changes in cerebral blood flow (CBF) as compared with cerebral metabolic rate of oxygen consumption (CMRO₂) during functional brain activity, lead to both brain temperature changes and the BOLD effect. Using an oxygen limitation model and a BOLD signal model, we obtain a transcendental equation relating CBF and CMRO₂ changes with the corresponding BOLD signal, which is solved in terms of the Lambert W function. Inserting this result in the dynamic bioheat equation describing the rate of temperature changes in the brain, we obtain a nonautonomous ordinary differential equation that depends on the BOLD response, which is solved numerically for each brain voxel. Temperature maps obtained from a real BOLD dataset registered in an attention to visual motion experiment were calculated, obtaining temperature variations in the range: (-0.15, 0.1) which is consistent with experimental results. The statistical analysis revealed that significant temperature activations have a similar distribution pattern than BOLD activations. An interesting difference was the activation of the precuneus in temperature maps, a region involved in visuospatial processing, an effect that was not observed on BOLD maps. Furthermore, temperature maps were more localized to gray matter regions than the original BOLD maps, showing less activated voxels in white matter and cerebrospinal fluid.

Modulatory Effects of Modafinil on Neural Circuits Regulating Emotion and Cognition

PubMed Central

Rasetti, Roberta; Mattay, Venkata S; Stankevich, Beth; Skjei, Kelsey; Blasi, Giuseppe; Sambataro, Fabio; Arrillaga-Romany, Isabel C; Goldberg, Terry E; Callicott, Joseph H; Apud, José A; Weinberger, Daniel R

2010-01-01

Modafinil differs from other arousal-enhancing agents in chemical structure, neurochemical profile, and behavioral effects. Most functional neuroimaging studies to date examined the effect of modafinil only on information processing underlying executive cognition, but cognitive enhancers in general have been shown to have pronounced effects on emotional behavior, too. We examined the effect of modafinil on neural circuits underlying affective processing and cognitive functions. Healthy volunteers were enrolled in this double-blinded placebo-controlled trial (100 mg/day for 7 days). They underwent BOLD fMRI while performing an emotion information-processing task that activates the amygdala and two prefrontally dependent cognitive tasks—a working memory (WM) task and a variable attentional control (VAC) task. A clinical assessment that included measurement of blood pressure, heart rate, the Hamilton anxiety scale, and the profile of mood state (POMS) questionnaire was also performed on each test day. BOLD fMRI revealed significantly decreased amygdala reactivity to fearful stimuli on modafinil compared with the placebo condition. During executive cognition tasks, a WM task and a VAC task, modafinil reduced BOLD signal in the prefrontal cortex and anterior cingulate. Although not statistically significant, there were trends for reduced anxiety, for decreased fatigue-inertia and increased vigor-activity, as well as decreased anger-hostility on modafinil. Modafinil in low doses has a unique physiologic profile compared with stimulant drugs: it enhances the efficiency of prefrontal cortical cognitive information processing, while dampening reactivity to threatening stimuli in the amygdala, a brain region implicated in anxiety. PMID:20555311

The translated conceptual survey of physics / stablization of the focal plane in two photon excitation fluorescence microscopy

NASA Astrophysics Data System (ADS)

Wada, Asma

As a reflection of my career to be an effective college physics teacher, my thesis is in two parts. The first is in education research, the focus of this part is to have a tool to evaluate pedagogies I have learned at the school and plan to apply in my classrooms back home. Consequently, this resulted in the development of the translated conceptual survey of physics ( TCSP). (TCSP) was designed by combining some questions from the Force Conceptual Inventory (FCI), and the Conceptual Survey of Electricity and Magnetism (CSEM) to assess student's understanding of basic concepts of Newtonian mechanics and electricity and magnetism in introductory physics. The idea of developing this questionnaire is to use it in classrooms back home as a part of a long term objective to implement what has been realized in the area of education research to improve the quality of teaching physics there. The survey was initially written in English, validated with interviews with native English speakers, translated into Arabic, and then validated via an interview with a native Arabic speaker. We then administered the survey to two different English-speaking intro physics courses and analyzed the results for consistency. The objective of the second part in my thesis is to expand my knowledge in an area of physics that I have interest in, and getting involved in a scientific research to develop skills I need as a teacher. My research is in optical physics, in particular, I am working on one of the challenges in implementing two photon excitation luorescence (TPEF) microscopy in imaging living systems. (TPEF) microscopy has been shown to be an invaluable tool for investigating biological structure and function in living organisms. The utility of (TPEF) imaging for this application arises from several important factors including it's ability to image deep within tissue, and to do so without harming the organism. Both of these advantages arise from the fact that (TPEF) imaging is done with excitation wavelengths in the near infrared (NIR). The (NIR) wavelength regime, 750- 1100nm, penetrates deep (>100 μm) into tissue, and has been used to image to depths of up to 1 mm. Further, the longer excitation wavelengths are less absorbing than the traditional ultraviolet wavelengths used in confocal microscopy, and are consequently less damaging. As a result, (TPEF) is presently the preferred tool for visualizing dynamics by biologists. One important aspect of imaging living systems, however, is that they move! This adds to the challenge of trying to study some particular biological function(s). This thesis begins to address this issue by combining a simple micro controller circuit that can be linked to a remote focusing scheme that will make it possible to lock a focal plane to a specific depth inside a living, moving specimen.

Cross multivariate correlation coefficients as screening tool for analysis of concurrent EEG-fMRI recordings.

PubMed

Ji, Hong; Petro, Nathan M; Chen, Badong; Yuan, Zejian; Wang, Jianji; Zheng, Nanning; Keil, Andreas

2018-02-06

Over the past decade, the simultaneous recording of electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI) data has garnered growing interest because it may provide an avenue towards combining the strengths of both imaging modalities. Given their pronounced differences in temporal and spatial statistics, the combination of EEG and fMRI data is however methodologically challenging. Here, we propose a novel screening approach that relies on a Cross Multivariate Correlation Coefficient (xMCC) framework. This approach accomplishes three tasks: (1) It provides a measure for testing multivariate correlation and multivariate uncorrelation of the two modalities; (2) it provides criterion for the selection of EEG features; (3) it performs a screening of relevant EEG information by grouping the EEG channels into clusters to improve efficiency and to reduce computational load when searching for the best predictors of the BOLD signal. The present report applies this approach to a data set with concurrent recordings of steady-state-visual evoked potentials (ssVEPs) and fMRI, recorded while observers viewed phase-reversing Gabor patches. We test the hypothesis that fluctuations in visuo-cortical mass potentials systematically covary with BOLD fluctuations not only in visual cortical, but also in anterior temporal and prefrontal areas. Results supported the hypothesis and showed that the xMCC-based analysis provides straightforward identification of neurophysiological plausible brain regions with EEG-fMRI covariance. Furthermore xMCC converged with other extant methods for EEG-fMRI analysis. © 2018 The Authors Journal of Neuroscience Research Published by Wiley Periodicals, Inc.

Disentangling neural processes of egocentric and allocentric mental spatial transformations using whole-body photos of self and other.

PubMed

Ganesh, Shanti; van Schie, Hein T; Cross, Emily S; de Lange, Floris P; Wigboldus, Daniël H J

2015-08-01

Mental imagery of one's body moving through space is important for imagining changing visuospatial perspectives, as well as for determining how we might appear to other people. Previous neuroimaging research has implicated the temporoparietal junction (TPJ) in this process. It is unclear, however, how neural activity in the TPJ relates to the rotation perspectives from which mental spatial transformation (MST) of one's own body can take place, i.e. from an egocentric or an allocentric perspective. It is also unclear whether TPJ involvement in MST is self-specific or whether the TPJ may also be involved in MST of other human bodies. The aim of the current study was to disentangle neural processes involved in egocentric versus allocentric MSTs of human bodies representing self and other. We measured functional brain activity of healthy participants while they performed egocentric and allocentric MSTs in relation to whole-body photographs of themselves and a same-sex stranger. Findings indicated higher blood oxygen level-dependent (BOLD) response in bilateral TPJ during egocentric versus allocentric MST. Moreover, BOLD response in the TPJ during egocentric MST correlated positively with self-report scores indicating how awkward participants felt while viewing whole-body photos of themselves. These findings considerably advance our understanding of TPJ involvement in MST and its interplay with self-awareness. Copyright © 2015 Elsevier Inc. All rights reserved.

Identification of Chemicals of Interest to the Department of Defense and U.S. Air Force Among the U.S. Environmental Protection Agency’s Integrated Risk Information System Chemicals that are Due for Reassessment of their Toxicity Values

DTIC Science & Technology

2010-03-16

Exceeded at ERP Soil and Groundwater Sites 86 A-2a. Identification of IRIS Chemicals of Interest on the ATSDR CERCLA Priority List of Hazardous...the Number (Bold Font) of Air Force ERP Samples in Which They Were Detected 317 A-4d. Air Force ERP Soil Samples: IRIS Chemicals of Interest...Ranked by the Number (Bold Font) of Air Force ERP Soil Samples in Which They Were Detected 333 A-4e. Air Force ERP Groundwater Samples: IRIS Chemicals of

Plasticity in animal personality traits: does prior experience alter the degree of boldness?

PubMed

Frost, Ashley J; Winrow-Giffen, Alexandria; Ashley, Paul J; Sneddon, Lynne U

2007-02-07

Theoreticians predict that animal 'personality' traits may be maladaptive if fixed throughout different contexts, so the present study aimed to test whether these traits are fixed or plastic. Rainbow trout (Onchorhyncus mykiss) were given emboldening or negative experiences in the forms of watching bold or shy individuals responding to novelty or winning or losing fights to examine whether prior experience affected boldness. Bold individuals that lost fights or watched shy demonstrators became more shy by increasing their latency to approach a novel object, whereas shy observers that watched bold demonstrators remained cautious and did not modify their responses to novelty. Shy winners became bolder and decreased their latency to approach a novel object, but shy losers also displayed this shift. In comparison, control groups showed no change in behaviour. Bold fishes given negative experiences reduced their boldness which may be an adaptive response; however, shy fishes may base their strategic decisions upon self-assessment of their relative competitive ability and increase their boldness in situations where getting to resources more quickly ensures they outcompete better competitors.

Development and validation of a liquid chromatography-tandem mass spectrometry method for the separation of conjugated and unconjugated 17alpha- and 17beta-boldenone in urine sample.

PubMed

Gasparini, Mara; Assini, Walter; Bozzoni, Eros; Tognoli, Nadia; Dusi, Guglielmo

2007-03-14

Natural occurrence or illegal treatment of boldenone (BOLD) presence in cattle urine is under debate within the European Union. Separation of conjugated and unconjugated forms of 17alpha-boldenone (alpha-BOLD) and 17beta-boldenone (beta-BOLD) and presence of related molecules as androsta-1,4-diene-3,17-dione (ADD) appear critical points for the decision of an illegal use. The aim of this study is a new analytical approach of BOLD and ADD confirmation in cattle urine. The separation between conjugated and unconjugated forms of BOLD was obtained by a preliminary urine liquid-liquid extraction step with ethyl acetate. In this step the organic phase extracts only unconjugated BOLD and ADD, while BOLD in conjugated form remain in urine phase. Afterwards the urine phase, contains conjugated BOLD, was subjected to an enzymatic deconjugation. Solid-phase extraction (OASIS-HLB Waters) was used for the purification and concentration of analytes in organic and urine phases and liquid chromatography ion electrospray tandem mass spectrometry (LC-MS-MS) was applied for the confirmation of BOLD and ADD, using deuterium-labelled 17beta-boldenone (BOLD-d3) as internal standard. The method was validated as a quantitative confirmatory method according to the Commission Decision 2002/657/CE. The results obtained demonstrate that the developed method show very high specificity, precision, trueness and ruggedness. Decision limits (CCalpha) smaller than 0.5 ng mL(-1) were obtained for each analyte.

Retinotopic mapping with Spin Echo BOLD at 7 Tesla

PubMed Central

Olman, Cheryl A.; Van de Moortele, Pierre-Francois; Schumacher, Jennifer F.; Guy, Joe; Uğurbil, Kâmil; Yacoub, Essa

2010-01-01

For blood oxygenation level-dependent (BOLD) functional MRI experiments, contrast-to-noise ratio (CNR) increases with increasing field strength for both gradient echo (GE) and spin echo (SE) BOLD techniques. However, susceptibility artifacts and non-uniform coil sensitivity profiles complicate large field-of-view fMRI experiments (e.g., experiments covering multiple visual areas instead of focusing on a single cortical region). Here, we use SE BOLD to acquire retinotopic mapping data in early visual areas, testing the feasibility of SE BOLD experiments spanning multiple cortical areas at 7 Tesla. We also use a recently developed method for normalizing signal intensity in T1-weighted anatomical images to enable automated segmentation of the cortical gray matter for scans acquired at 7T with either surface or volume coils. We find that the CNR of the 7T GE data (average single-voxel, single-scan stimulus coherence: 0.41) is almost twice that of the 3T GE BOLD data (average coherence: 0.25), with the CNR of the SE BOLD data (average coherence: 0.23) comparable to that of the 3T GE data. Repeated measurements in individual subjects find that maps acquired with 1.8 mm resolution at 3T and 7T with GE BOLD and at 7T with SE BOLD show no systematic differences in either the area or the boundary locations for V1, V2 and V3, demonstrating the feasibility of high-resolution SE BOLD experiments with good sensitivity throughout multiple visual areas. PMID:20656431

Structural and functional neuroplasticity in human learning of spatial routes.

PubMed

Keller, Timothy A; Just, Marcel Adam

2016-01-15

Recent findings with both animals and humans suggest that decreases in microscopic movements of water in the hippocampus reflect short-term neuroplasticity resulting from learning. Here we examine whether such neuroplastic structural changes concurrently alter the functional connectivity between hippocampus and other regions involved in learning. We collected both diffusion-weighted images and fMRI data before and after humans performed a 45min spatial route-learning task. Relative to a control group with equal practice time, there was decreased diffusivity in the posterior-dorsal dentate gyrus of the left hippocampus in the route-learning group accompanied by increased synchronization of fMRI-measured BOLD signal between this region and cortical areas, and by changes in behavioral performance. These concurrent changes characterize the multidimensionality of neuroplasticity as it enables human spatial learning. Copyright © 2015 Elsevier Inc. All rights reserved.

The Effect of Letter-stroke Boldness on Reading Speed in Central and Peripheral Vision

PubMed Central

Bernard, Jean-Baptiste; Kumar, Girish; Junge, Jasmine; Chung, Susana T.L.

2013-01-01

People with central vision loss often prefer boldface print over normal print for reading. However, little is known about how reading speed is influenced by the letter-stroke boldness of font. In this study, we examined the reliance of reading speed on stroke boldness, and determined whether this reliance differs between the normal central and peripheral vision. Reading speed was measured using the rapid serial visual presentation paradigm, where observers with normal vision read aloud short single sentences presented on a computer monitor, one word at a time. Text was rendered in Courier at six levels of boldness, defined as the stroke-width normalized to that of the standard Courier font: 0.27, 0.72, 1, 1.48, 1.89 and 3.04× the standard. Testings were conducted at the fovea and 10° in the inferior visual field. Print sizes used were 0.8× and 1.4× the critical print size (smallest print size that can be read at the maximum reading speed). At the fovea, reading speed was invariant for the middle four levels of boldness, but dropped by 23.3% for the least and the most bold text. At 10° eccentricity, reading speed was virtually the same for all boldness <1, but showed a poorer tolerance to bolder text, dropping by 21.5% for 1.89x boldness and 51% for the most bold (3.04x) text. These results could not be accounted for by the changes in print size or the RMS contrast of text associated with changes in stroke boldness. Our results suggest that contrary to the popular belief, reading speed does not benefit from bold text in the normal fovea and periphery. Excessive increase in stroke boldness may even impair reading speed, especially in the periphery. PMID:23523572

The effect of letter-stroke boldness on reading speed in central and peripheral vision.

PubMed

Bernard, Jean-Baptiste; Kumar, Girish; Junge, Jasmine; Chung, Susana T L

2013-05-24

People with central vision loss often prefer boldface print over normal print for reading. However, little is known about how reading speed is influenced by the letter-stroke boldness of font. In this study, we examined the reliance of reading speed on stroke boldness, and determined whether this reliance differs between the normal central and peripheral vision. Reading speed was measured using the rapid serial visual presentation paradigm, where observers with normal vision read aloud short single sentences presented on a computer monitor, one word at a time. Text was rendered in Courier at six levels of boldness, defined as the stroke-width normalized to that of the standard Courier font: 0.27, 0.72, 1, 1.48, 1.89 and 3.04× the standard. Testings were conducted at the fovea and 10° in the inferior visual field. Print sizes used were 0.8× and 1.4× the critical print size (smallest print size that can be read at the maximum reading speed). At the fovea, reading speed was invariant for the middle four levels of boldness, but dropped by 23.3% for the least and the most bold text. At 10° eccentricity, reading speed was virtually the same for all boldness <1, but showed a poorer tolerance to bolder text, dropping by 21.5% for 1.89× boldness and 51% for the most bold (3.04×) text. These results could not be accounted for by the changes in print size or the RMS contrast of text associated with changes in stroke boldness. Our results suggest that contrary to the popular belief, reading speed does not benefit from bold text in the normal fovea and periphery. Excessive increase in stroke boldness may even impair reading speed, especially in the periphery. Copyright © 2013 Elsevier Ltd. All rights reserved.

Connectivity Reveals Sources of Predictive Coding Signals in Early Visual Cortex During Processing of Visual Optic Flow.

PubMed

Schindler, Andreas; Bartels, Andreas

2017-05-01

Superimposed on the visual feed-forward pathway, feedback connections convey higher level information to cortical areas lower in the hierarchy. A prominent framework for these connections is the theory of predictive coding where high-level areas send stimulus interpretations to lower level areas that compare them with sensory input. Along these lines, a growing body of neuroimaging studies shows that predictable stimuli lead to reduced blood oxygen level-dependent (BOLD) responses compared with matched nonpredictable counterparts, especially in early visual cortex (EVC) including areas V1-V3. The sources of these modulatory feedback signals are largely unknown. Here, we re-examined the robust finding of relative BOLD suppression in EVC evident during processing of coherent compared with random motion. Using functional connectivity analysis, we show an optic flow-dependent increase of functional connectivity between BOLD suppressed EVC and a network of visual motion areas including MST, V3A, V6, the cingulate sulcus visual area (CSv), and precuneus (Pc). Connectivity decreased between EVC and 2 areas known to encode heading direction: entorhinal cortex (EC) and retrosplenial cortex (RSC). Our results provide first evidence that BOLD suppression in EVC for predictable stimuli is indeed mediated by specific high-level areas, in accord with the theory of predictive coding. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Cholinergic enhancement reduces functional connectivity and BOLD variability in visual extrastriate cortex during selective attention.

PubMed

Ricciardi, Emiliano; Handjaras, Giacomo; Bernardi, Giulio; Pietrini, Pietro; Furey, Maura L

2013-01-01

Enhancing cholinergic function improves performance on various cognitive tasks and alters neural responses in task specific brain regions. We have hypothesized that the changes in neural activity observed during increased cholinergic function reflect an increase in neural efficiency that leads to improved task performance. The current study tested this hypothesis by assessing neural efficiency based on cholinergically-mediated effects on regional brain connectivity and BOLD signal variability. Nine subjects participated in a double-blind, placebo-controlled crossover fMRI study. Following an infusion of physostigmine (1 mg/h) or placebo, echo-planar imaging (EPI) was conducted as participants performed a selective attention task. During the task, two images comprised of superimposed pictures of faces and houses were presented. Subjects were instructed periodically to shift their attention from one stimulus component to the other and to perform a matching task using hand held response buttons. A control condition included phase-scrambled images of superimposed faces and houses that were presented in the same temporal and spatial manner as the attention task; participants were instructed to perform a matching task. Cholinergic enhancement improved performance during the selective attention task, with no change during the control task. Functional connectivity analyses showed that the strength of connectivity between ventral visual processing areas and task-related occipital, parietal and prefrontal regions reduced significantly during cholinergic enhancement, exclusively during the selective attention task. Physostigmine administration also reduced BOLD signal temporal variability relative to placebo throughout temporal and occipital visual processing areas, again during the selective attention task only. Together with the observed behavioral improvement, the decreases in connectivity strength throughout task-relevant regions and BOLD variability within stimulus processing regions support the hypothesis that cholinergic augmentation results in enhanced neural efficiency. This article is part of a Special Issue entitled 'Cognitive Enhancers'. Copyright © 2012 Elsevier Ltd. All rights reserved.

Cholinergic enhancement reduces functional connectivity and BOLD variability in visual extrastriate cortex during selective attention

PubMed Central

Ricciardi, Emiliano; Handjaras, Giacomo; Bernardi, Giulio; Pietrini, Pietro; Furey, Maura L.

2012-01-01

Enhancing cholinergic function improves performance on various cognitive tasks and alters neural responses in task specific brain regions. Previous findings by our group strongly suggested that the changes in neural activity observed during increased cholinergic function may reflect an increase in neural efficiency that leads to improved task performance. The current study was designed to assess the effects of cholinergic enhancement on regional brain connectivity and BOLD signal variability. Nine subjects participated in a double-blind, placebo-controlled crossover functional magnetic resonance imaging (fMRI) study. Following an infusion of physostigmine (1mg/hr) or placebo, echo-planar imaging (EPI) was conducted as participants performed a selective attention task. During the task, two images comprised of superimposed pictures of faces and houses were presented. Subjects were instructed periodically to shift their attention from one stimulus component to the other and to perform a matching task using hand held response buttons. A control condition included phase-scrambled images of superimposed faces and houses that were presented in the same temporal and spatial manner as the attention task; participants were instructed to perform a matching task. Cholinergic enhancement improved performance during the selective attention task, with no change during the control task. Functional connectivity analyses showed that the strength of connectivity between ventral visual processing areas and task-related occipital, parietal and prefrontal regions was reduced significantly during cholinergic enhancement, exclusively during the selective attention task. Cholinergic enhancement also reduced BOLD signal temporal variability relative to placebo throughout temporal and occipital visual processing areas, again during the selective attention task only. Together with the observed behavioral improvement, the decreases in connectivity strength throughout task-relevant regions and BOLD variability within stimulus processing regions provide further support to the hypothesis that cholinergic augmentation results in enhanced neural efficiency. PMID:22906685

Enhancement of Temporal Resolution and BOLD Sensitivity in Real-Time fMRI using Multi-Slab Echo-Volumar Imaging

PubMed Central

Posse, Stefan; Ackley, Elena; Mutihac, Radu; Rick, Jochen; Shane, Matthew; Murray-Krezan, Cristina; Zaitsev, Maxim; Speck, Oliver

2012-01-01

In this study, a new approach to high-speed fMRI using multi-slab echo-volumar imaging (EVI) is developed that minimizes geometrical image distortion and spatial blurring, and enables nonaliased sampling of physiological signal fluctuation to increase BOLD sensitivity compared to conventional echo-planar imaging (EPI). Real-time fMRI using whole brain 4-slab EVI with 286 ms temporal resolution (4 mm isotropic voxel size) and partial brain 2-slab EVI with 136 ms temporal resolution (4×4×6 mm3 voxel size) was performed on a clinical 3 Tesla MRI scanner equipped with 12-channel head coil. Four-slab EVI of visual and motor tasks significantly increased mean (visual: 96%, motor: 66%) and maximum t-score (visual: 263%, motor: 124%) and mean (visual: 59%, motor: 131%) and maximum (visual: 29%, motor: 67%) BOLD signal amplitude compared with EPI. Time domain moving average filtering (2 s width) to suppress physiological noise from cardiac and respiratory fluctuations further improved mean (visual: 196%, motor: 140%) and maximum (visual: 384%, motor: 200%) t-scores and increased extents of activation (visual: 73%, motor: 70%) compared to EPI. Similar sensitivity enhancement, which is attributed to high sampling rate at only moderately reduced temporal signal-to-noise ratio (mean: − 52%) and longer sampling of the BOLD effect in the echo-time domain compared to EPI, was measured in auditory cortex. Two-slab EVI further improved temporal resolution for measuring task-related activation and enabled mapping of five major resting state networks (RSNs) in individual subjects in 5 min scans. The bilateral sensorimotor, the default mode and the occipital RSNs were detectable in time frames as short as 75 s. In conclusion, the high sampling rate of real-time multi-slab EVI significantly improves sensitivity for studying the temporal dynamics of hemodynamic responses and for characterizing functional networks at high field strength in short measurement times. PMID:22398395

The physics of functional magnetic resonance imaging (fMRI)

NASA Astrophysics Data System (ADS)

Buxton, Richard B.

2013-09-01

Functional magnetic resonance imaging (fMRI) is a methodology for detecting dynamic patterns of activity in the working human brain. Although the initial discoveries that led to fMRI are only about 20 years old, this new field has revolutionized the study of brain function. The ability to detect changes in brain activity has a biophysical basis in the magnetic properties of deoxyhemoglobin, and a physiological basis in the way blood flow increases more than oxygen metabolism when local neural activity increases. These effects translate to a subtle increase in the local magnetic resonance signal, the blood oxygenation level dependent (BOLD) effect, when neural activity increases. With current techniques, this pattern of activation can be measured with resolution approaching 1 mm3 spatially and 1 s temporally. This review focuses on the physical basis of the BOLD effect, the imaging methods used to measure it, the possible origins of the physiological effects that produce a mismatch of blood flow and oxygen metabolism during neural activation, and the mathematical models that have been developed to understand the measured signals. An overarching theme is the growing field of quantitative fMRI, in which other MRI methods are combined with BOLD methods and analyzed within a theoretical modeling framework to derive quantitative estimates of oxygen metabolism and other physiological variables. That goal is the current challenge for fMRI: to move fMRI from a mapping tool to a quantitative probe of brain physiology.

The physics of functional magnetic resonance imaging (fMRI)

PubMed Central

Buxton, Richard B

2015-01-01

Functional magnetic resonance imaging (fMRI) is a methodology for detecting dynamic patterns of activity in the working human brain. Although the initial discoveries that led to fMRI are only about 20 years old, this new field has revolutionized the study of brain function. The ability to detect changes in brain activity has a biophysical basis in the magnetic properties of deoxyhemoglobin, and a physiological basis in the way blood flow increases more than oxygen metabolism when local neural activity increases. These effects translate to a subtle increase in the local magnetic resonance signal, the blood oxygenation level dependent (BOLD) effect, when neural activity increases. With current techniques, this pattern of activation can be measured with resolution approaching 1 mm3 spatially and 1 s temporally. This review focuses on the physical basis of the BOLD effect, the imaging methods used to measure it, the possible origins of the physiological effects that produce a mismatch of blood flow and oxygen metabolism during neural activation, and the mathematical models that have been developed to understand the measured signals. An overarching theme is the growing field of quantitative fMRI, in which other MRI methods are combined with BOLD methods and analyzed within a theoretical modeling framework to derive quantitative estimates of oxygen metabolism and other physiological variables. That goal is the current challenge for fMRI: to move fMRI from a mapping tool to a quantitative probe of brain physiology. PMID:24006360

Continuous EEG-fMRI in Pre-Surgical Evaluation of a Patient with Symptomatic Seizures: Bold Activation Linked to Interictal Epileptic Discharges Caused by Cavernoma.

PubMed

Avesani, M; Formaggio, E; Milanese, F; Baraldo, A; Gasparini, A; Cerini, R; Bongiovanni, L G; Pozzi Mucelli, R; Fiaschi, A; Manganotti, P

2008-04-07

We used continuous electroencephalography-functional magnetic resonance imaging (EEG-fMRI) to identify the linkage between the "epileptogenic" and the "irritative" area in a patient with symptomatic epilepsy (cavernoma, previously diagnosed and surgically treated), i.e. a patient with a well known "epileptogenic area", and to increase the possibility of a non invasive pre-surgical evaluation of drug-resistant epilepsies. A compatible MRI system was used (EEG with 29 scalp electrodes and two electrodes for ECG and EMG) and signals were recorded with a 1.5 Tesla MRI scanner. After the recording session and MRI artifact removal, EEG data were analyzed offline and used as paradigms in fMRI study. Activation (EEG sequences with interictal slow-spiked-wave activity) and rest (sequences of normal EEG) conditions were compared to identify the potential resulting focal increase in BOLD signal and to consider if this is spatially linked to the interictal focus used as a paradigm and to the lesion. We noted an increase in the BOLD signal in the left neocortical temporal region, laterally and posteriorly to the poro-encephalic cavity (residual of cavernoma previously removed), that is around the "epileptogenic area". In our study "epileptogenic" and "irritative" areas were connected with each other. Combined EEG-fMRI may become routine in clinical practice for a better identification of an irritative and lesional focus in patients with symptomatic drug-resistant epilepsy.

The physics of functional magnetic resonance imaging (fMRI).

PubMed

Buxton, Richard B

2013-09-01

Functional magnetic resonance imaging (fMRI) is a methodology for detecting dynamic patterns of activity in the working human brain. Although the initial discoveries that led to fMRI are only about 20 years old, this new field has revolutionized the study of brain function. The ability to detect changes in brain activity has a biophysical basis in the magnetic properties of deoxyhemoglobin, and a physiological basis in the way blood flow increases more than oxygen metabolism when local neural activity increases. These effects translate to a subtle increase in the local magnetic resonance signal, the blood oxygenation level dependent (BOLD) effect, when neural activity increases. With current techniques, this pattern of activation can be measured with resolution approaching 1 mm(3) spatially and 1 s temporally. This review focuses on the physical basis of the BOLD effect, the imaging methods used to measure it, the possible origins of the physiological effects that produce a mismatch of blood flow and oxygen metabolism during neural activation, and the mathematical models that have been developed to understand the measured signals. An overarching theme is the growing field of quantitative fMRI, in which other MRI methods are combined with BOLD methods and analyzed within a theoretical modeling framework to derive quantitative estimates of oxygen metabolism and other physiological variables. That goal is the current challenge for fMRI: to move fMRI from a mapping tool to a quantitative probe of brain physiology.

Sustained negative BOLD response in human fMRI finger tapping task.

PubMed

Liu, Yadong; Shen, Hui; Zhou, Zongtan; Hu, Dewen

2011-01-01

In this work, we investigated the sustained negative blood oxygen level-dependent (BOLD) response (sNBR) using functional magnetic resonance imaging during a finger tapping task. We observed that the sNBR for this task was more extensive than has previously been reported. The cortical regions involved in sNBR are divided into the following three groups: frontal, somatosensory and occipital. By investigating the spatial structure, area, amplitude, and dynamics of the sNBR in comparison with those of its positive BOLD response (PBR) counterpart, we made the following observations. First, among the three groups, the somatosensory group contained the greatest number of activated voxels and the fewest deactivated voxels. In addition, the amplitude of the sNBR in this group was the smallest among the three groups. Second, the onset and peak time of the sNBR are both larger than those of the PBR, whereas the falling edge time of the sNBR is less than that of the PBR. Third, the long distance between most sNBR foci and their corresponding PBR foci makes it unlikely that they share the same blood supply artery. Fourth, the couplings between the sNBR and its PBR counterpart are distinct among different regions and thus should be investigated separately. These findings imply that the origin of most sNBR foci in the finger-tapping task is much more likely to be neuronal activity suppression rather than "blood steal."

Different roles of the posterior inferior frontal gyrus in Chinese character form judgment differences between literate and illiterate individuals.

PubMed

Wu, Jinglong; Wang, Bin; Yan, Tianyi; Li, Xiujun; Bao, Xuexiang; Guo, Qiyong

2012-01-11

In the present study, we used event-related functional magnetic resonance imaging (fMRI) to explore the different roles of the posterior inferior frontal gyrus (pIFG) in Chinese character form judgment between literate and illiterate subjects. Using event-related fMRI, 24 healthy right-handed Chinese subjects (12 literates and 12 illiterates) were asked to perform Chinese character and figure form judgment tasks. The blood oxygen level-dependent (BOLD) differences in pIFG were examined with general linear modeling (GLM). We found differences in reaction times and accuracy between subjects as they performed these tasks. These behavioral differences reflect the different cognitive demands of character form judgment for literate and illiterate individuals. The results showed differences in the BOLD response patterns in the pIFG between the two discrimination tasks and the two subject groups. A comparison of the character and figure tasks showed that literate and illiterate subjects had similar BOLD responses in the inferior frontal gyrus. However, differences in behavioral performance suggest that the pIFG plays a different role in Chinese character form judgment for each subject group. In literate subjects, the left pIFG mediated access to phonology in achieving Chinese character form judgment, whereas the right pIFG participated in the processing of the orthography of Chinese characters. In illiterate subjects, the bilateral frontal gyrus participated in the visual-spatial processing of Chinese characters to achieve form judgment. Copyright © 2011 Elsevier B.V. All rights reserved.

Identifying differences in brain activities and an accurate detection of autism spectrum disorder using resting state functional-magnetic resonance imaging : A spatial filtering approach.

PubMed

Subbaraju, Vigneshwaran; Suresh, Mahanand Belathur; Sundaram, Suresh; Narasimhan, Sundararajan

2017-01-01

This paper presents a new approach for detecting major differences in brain activities between Autism Spectrum Disorder (ASD) patients and neurotypical subjects using the resting state fMRI. Further the method also extracts discriminative features for an accurate diagnosis of ASD. The proposed approach determines a spatial filter that projects the covariance matrices of the Blood Oxygen Level Dependent (BOLD) time-series signals from both the ASD patients and neurotypical subjects in orthogonal directions such that they are highly separable. The inverse of this filter also provides a spatial pattern map within the brain that highlights those regions responsible for the distinguishable activities between the ASD patients and neurotypical subjects. For a better classification, highly discriminative log-variance features providing the maximum separation between the two classes are extracted from the projected BOLD time-series data. A detailed study has been carried out using the publicly available data from the Autism Brain Imaging Data Exchange (ABIDE) consortium for the different gender and age-groups. The study results indicate that for all the above categories, the regional differences in resting state activities are more commonly found in the right hemisphere compared to the left hemisphere of the brain. Among males, a clear shift in activities to the prefrontal cortex is observed for ASD patients while other parts of the brain show diminished activities compared to neurotypical subjects. Among females, such a clear shift is not evident; however, several regions, especially in the posterior and medial portions of the brain show diminished activities due to ASD. Finally, the classification performance obtained using the log-variance features is found to be better when compared to earlier studies in the literature. Copyright © 2016 Elsevier B.V. All rights reserved.

21 CFR 341.76 - Labeling of bronchodilator drug products.

Code of Federal Regulations, 2014 CFR

2014-04-01

... doctor or pharmacist before taking this product.” (2) The following information shall appear after the... subheading “Ask a doctor or pharmacist before use if you are” [in bold type]: (i) “[Bullet] taking...

21 CFR 341.76 - Labeling of bronchodilator drug products.

Code of Federal Regulations, 2012 CFR

2012-04-01

... doctor or pharmacist before taking this product.” (2) The following information shall appear after the... subheading “Ask a doctor or pharmacist before use if you are” [in bold type]: (i) “[Bullet] taking...

21 CFR 341.76 - Labeling of bronchodilator drug products.

Code of Federal Regulations, 2013 CFR

2013-04-01

... doctor or pharmacist before taking this product.” (2) The following information shall appear after the... subheading “Ask a doctor or pharmacist before use if you are” [in bold type]: (i) “[Bullet] taking...

Early anti-correlated BOLD signal changes of physiologic origin.

PubMed

Bright, Molly G; Bianciardi, Marta; de Zwart, Jacco A; Murphy, Kevin; Duyn, Jeff H

2014-02-15

Negative BOLD signals that are synchronous with resting state fluctuations have been observed in large vessels in the cortical sulci and surrounding the ventricles. In this study, we investigated the origin of these negative BOLD signals by applying a Cued Deep Breathing (CDB) task to create transient hypocapnia and a resultant global fMRI signal decrease. We hypothesized that a global stimulus would amplify the effect in large vessels and that using a global negative (vasoconstrictive) stimulus would test whether these voxels exhibit either inherently negative or simply anti-correlated BOLD responses. Significantly anti-correlated, but positive, BOLD signal changes during respiratory challenges were identified in voxels primarily located near edges of brain spaces containing CSF. These positive BOLD responses occurred earlier than the negative CDB response across most of gray matter voxels. These findings confirm earlier suggestions that in some brain regions, local, fractional changes in CSF volume may overwhelm BOLD-related signal changes, leading to signal anti-correlation. We show that regions with CDB anti-correlated signals coincide with most, but not all, of the regions with negative BOLD signal changes observed during a visual and motor stimulus task. Thus, the addition of a physiological challenge to fMRI experiments can help identify which negative BOLD signals are passive physiological anti-correlations and which may have a putative neuronal origin. Published by Elsevier Inc.

Early anti-correlated BOLD signal changes of physiologic origin

PubMed Central

Bright, Molly G.; Bianciardi, Marta; de Zwart, Jacco A.; Murphy, Kevin; Duyn, Jeff H.

2014-01-01

Negative BOLD signals that are synchronous with resting state fluctuations have been observed in large vessels in the cortical sulci and surrounding the ventricles. In this study, we investigated the origin of these negative BOLD signals by applying a Cued Deep Breathing (CDB) task to create transient hypocapnia and a resultant global fMRI signal decrease. We hypothesized that a global stimulus would amplify the effect in large vessels and that using a global negative (vasoconstrictive) stimulus would test whether these voxels exhibit either inherently negative or simply anti-correlated BOLD responses. Significantly anti-correlated, but positive, BOLD signal changes during respiratory challenges were identified in voxels primarily located near edges of brain spaces containing CSF. These positive BOLD responses occurred earlier than the negative CDB response across most of gray matter voxels. These findings confirm earlier suggestions that in some brain regions, local, fractional changes in CSF volume may overwhelm BOLD-related signal changes, leading to signal anti-correlation. We show that regions with CDB anti-correlated signals coincide with most, but not all, of the regions with negative BOLD signal changes observed during a visual and motor stimulus task. Thus, the addition of a physiological challenge to fMRI experiments can help identify which negative BOLD signals are passive physiological anti-correlations and which may have a putative neuronal origin. PMID:24211818

Fitness Consequences of Boldness in Juvenile and Adult Largemouth Bass.

PubMed

Ballew, Nicholas G; Mittelbach, Gary G; Scribner, Kim T

2017-04-01

To date, most studies investigating the relationship between personality traits and fitness have focused on a single measure of fitness (such as survival) at a specific life stage. However, many personality traits likely have multiple effects on fitness, potentially operating across different functional contexts and stages of development. Here, we address the fitness consequences of boldness, under seminatural conditions, across life stages and functional contexts in largemouth bass (Micropterus salmoides). Specifically, we report the effect of boldness on (1) juvenile survivorship in an outdoor pond containing natural prey and predators and (2) adult reproductive success in three outdoor ponds across three reproductive seasons (years). Juvenile survival was negatively affected by boldness, with bolder juveniles having a lower probability of survival than shyer juveniles. In contrast, bolder adult male bass had greater reproductive success than their shyer male counterparts. Female reproductive success was not affected by boldness. These findings demonstrate that boldness can affect fitness differently across life stages. Further, boldness was highly consistent across years and significantly heritable, which suggests that boldness has a genetic component. Thus, our results support theory suggesting that fitness trade-offs across life stages may contribute to the maintenance of personality variation within populations.

The BOLD signal and neurovascular coupling in autism.

PubMed

Reynell, Clare; Harris, Julia J

2013-10-01

BOLD (blood oxygen level dependent) fMRI (functional magnetic resonance imaging) is commonly used to study differences in neuronal activity between human populations. As the BOLD response is an indirect measure of neuronal activity, meaningful interpretation of differences in BOLD responses between groups relies upon a stable relationship existing between neuronal activity and the BOLD response across these groups. However, this relationship can be altered by changes in neurovascular coupling or energy consumption, which would lead to problems in identifying differences in neuronal activity. In this review, we focus on fMRI studies of people with autism, and comparisons that are made of their BOLD responses with those of control groups. We examine neurophysiological differences in autism that may alter neurovascular coupling or energy use, discuss recent studies that have used fMRI to identify differences between participants with autism and control participants, and explore experimental approaches that could help attribute between-group differences in BOLD signals to either neuronal or neurovascular factors. Copyright © 2013 Elsevier Ltd. All rights reserved.

The BOLD signal and neurovascular coupling in autism

PubMed Central

Reynell, Clare; Harris, Julia J.

2013-01-01

BOLD (blood oxygen level dependent) fMRI (functional magnetic resonance imaging) is commonly used to study differences in neuronal activity between human populations. As the BOLD response is an indirect measure of neuronal activity, meaningful interpretation of differences in BOLD responses between groups relies upon a stable relationship existing between neuronal activity and the BOLD response across these groups. However, this relationship can be altered by changes in neurovascular coupling or energy consumption, which would lead to problems in identifying differences in neuronal activity. In this review, we focus on fMRI studies of people with autism, and comparisons that are made of their BOLD responses with those of control groups. We examine neurophysiological differences in autism that may alter neurovascular coupling or energy use, discuss recent studies that have used fMRI to identify differences between participants with autism and control participants, and explore experimental approaches that could help attribute between-group differences in BOLD signals to either neuronal or neurovascular factors. PMID:23917518

Negative BOLD with Large Increases in Neuronal Activity

PubMed Central

Khubchandani, Manjula; Motelow, Joshua E.; Sanganahalli, Basavaraju G.; Hyder, Fahmeed

2008-01-01

Blood oxygen level–dependent (BOLD) functional magnetic resonance imaging (fMRI) is widely used in neuroscience to study brain activity. However, BOLD fMRI does not measure neuronal activity directly but depends on cerebral blood flow (CBF), cerebral blood volume (CBV), and cerebral metabolic rate of oxygen (CMRO2) consumption. Using fMRI, CBV, CBF, neuronal recordings, and CMRO2 modeling, we investigated how the signals are related during seizures in rats. We found that increases in hemodynamic, neuronal, and metabolic activity were associated with positive BOLD signals in the cortex, but with negative BOLD signals in hippocampus. Our data show that negative BOLD signals do not necessarily imply decreased neuronal activity or CBF, but can result from increased neuronal activity, depending on the interplay between hemodynamics and metabolism. Caution should be used in interpreting fMRI signals because the relationship between neuronal activity and BOLD signals may depend on brain region and state and can be different during normal and pathological conditions. PMID:18063563

Effective Connectivity of Cortical Sensorimotor Networks During Finger Movement Tasks: A Simultaneous fNIRS, fMRI, EEG Study.

PubMed

Anwar, A R; Muthalib, M; Perrey, S; Galka, A; Granert, O; Wolff, S; Heute, U; Deuschl, G; Raethjen, J; Muthuraman, Muthuraman

2016-09-01

Recently, interest has been growing to understand the underlying dynamic directional relationship between simultaneously activated regions of the brain during motor task performance. Such directionality analysis (or effective connectivity analysis), based on non-invasive electrophysiological (electroencephalography-EEG) and hemodynamic (functional near infrared spectroscopy-fNIRS; and functional magnetic resonance imaging-fMRI) neuroimaging modalities can provide an estimate of the motor task-related information flow from one brain region to another. Since EEG, fNIRS and fMRI modalities achieve different spatial and temporal resolutions of motor-task related activation in the brain, the aim of this study was to determine the effective connectivity of cortico-cortical sensorimotor networks during finger movement tasks measured by each neuroimaging modality. Nine healthy subjects performed right hand finger movement tasks of different complexity (simple finger tapping-FT, simple finger sequence-SFS, and complex finger sequence-CFS). We focused our observations on three cortical regions of interest (ROIs), namely the contralateral sensorimotor cortex (SMC), the contralateral premotor cortex (PMC) and the contralateral dorsolateral prefrontal cortex (DLPFC). We estimated the effective connectivity between these ROIs using conditional Granger causality (GC) analysis determined from the time series signals measured by fMRI (blood oxygenation level-dependent-BOLD), fNIRS (oxygenated-O2Hb and deoxygenated-HHb hemoglobin), and EEG (scalp and source level analysis) neuroimaging modalities. The effective connectivity analysis showed significant bi-directional information flow between the SMC, PMC, and DLPFC as determined by the EEG (scalp and source), fMRI (BOLD) and fNIRS (O2Hb and HHb) modalities for all three motor tasks. However the source level EEG GC values were significantly greater than the other modalities. In addition, only the source level EEG showed a significantly greater forward than backward information flow between the ROIs. This simultaneous fMRI, fNIRS and EEG study has shown through independent GC analysis of the respective time series that a bi-directional effective connectivity occurs within a cortico-cortical sensorimotor network (SMC, PMC and DLPFC) during finger movement tasks.

BOLD Imaging in Awake Wild-Type and Mu-Opioid Receptor Knock-Out Mice Reveals On-Target Activation Maps in Response to Oxycodone

PubMed Central

Moore, Kelsey; Madularu, Dan; Iriah, Sade; Yee, Jason R.; Kulkarni, Praveen; Darcq, Emmanuel; Kieffer, Brigitte L.; Ferris, Craig F.

2016-01-01

Blood oxygen level dependent (BOLD) imaging in awake mice was used to identify differences in brain activity between wild-type, and Mu (μ) opioid receptor knock-outs (MuKO) in response to oxycodone (OXY). Using a segmented, annotated MRI mouse atlas and computational analysis, patterns of integrated positive and negative BOLD activity were identified across 122 brain areas. The pattern of positive BOLD showed enhanced activation across the brain in WT mice within 15 min of intraperitoneal administration of 2.5 mg of OXY. BOLD activation was detected in 72 regions out of 122, and was most prominent in areas of high μ opioid receptor density (thalamus, ventral tegmental area, substantia nigra, caudate putamen, basal amygdala, and hypothalamus), and focus on pain circuits indicated strong activation in major pain processing centers (central amygdala, solitary tract, parabrachial area, insular cortex, gigantocellularis area, ventral thalamus primary sensory cortex, and prelimbic cortex). Importantly, the OXY-induced positive BOLD was eliminated in MuKO mice in most regions, with few exceptions (some cerebellar nuclei, CA3 of the hippocampus, medial amygdala, and preoptic areas). This result indicates that most effects of OXY on positive BOLD are mediated by the μ opioid receptor (on-target effects). OXY also caused an increase in negative BOLD in WT mice in few regions (16 out of 122) and, unlike the positive BOLD response the negative BOLD was only partially eliminated in the MuKO mice (cerebellum), and in some case intensified (hippocampus). Negative BOLD analysis therefore shows activation and deactivation events in the absence of the μ receptor for some areas where receptor expression is normally extremely low or absent (off-target effects). Together, our approach permits establishing opioid-induced BOLD activation maps in awake mice. In addition, comparison of WT and MuKO mutant mice reveals both on-target and off-target activation events, and set an OXY brain signature that should, in the future, be compared to other μ opioid agonists. PMID:27857679

Effect of surrounding vasculature on intravoxel BOLD signal.

PubMed

Chen, Zikuan; Caprihan, Arvind; Calhoun, Vince

2010-04-01

The nonlocal influence from distant magnetization will affect the magnetic field at a voxel in question. Existing reports on BOLD simulation only consider vasculature inside a single voxel, thus omitting the contribution from the surrounding regions. In this article, the authors study the effect of the surrounding vasculature on the magnetic field and the BOLD signal at a cortical voxel by numerical simulation. A cortical voxel is generated as a cubic bin filled with randomly networked capillary vessels. First, the authors generate a cortical voxel with a random vessel network and embed it in a greater voxel by filling its surrounding region with vasculatures by different strategies. Next, they calculate the blood-susceptibility-induced magnetic field (BOLD field) at the voxel of interest (VOI) by a Fourier transform technique for different surrounding scenarios and varying surrounding extent. The BOLD field inhomogeneity is described by a radial distribution with a collection of cubic shell masks. The surrounding extent is defined by a collection of concentric cubes, which encase the VOI. Given a BOLD field in the presence of surrounding vasculature, they calculate BOLD signals by intravoxel dephasing. The influence from the surroundings on the BOLD field at a voxel in question mainly happens at the boundary. The most influence to the BOLD signal is from the inner surroundings. For a 160 x 160 x 160 microm3 voxel embedded in a 480 x 480 x 480 microm3 greater region, the surroundings could disturb the magnetic field by an amount in the range of [-0.002, 0.010] ppmT and could change the BOLD signal ratio in the range of [2.5%, 10%]. (These results were generated from the setting of delta(chi b)B0 = 3 ppmT, capillary = {2.5,6,9} microm, and relaxation time = 60 ms). The surrounding vasculature will impose a magnetic field disturbance at the voxel in question due to the nonlocal influence of magnetization. Simulation results show that the surrounding vasculature significantly alters the magnetic field (up to 0.01 ppmT) and BOLD signal (typically no more than 10%) at the central voxel and thus should be considered in accurate BOLD modeling.

Crossing the implementation chasm: a proposal for bold action.

PubMed

Lorenzi, Nancy M; Novak, Laurie L; Weiss, Jacob B; Gadd, Cynthia S; Unertl, Kim M

2008-01-01

As health care organizations dramatically increase investment in information technology (IT) and the scope of their IT projects, implementation failures become critical events. Implementation failures cause stress on clinical units, increase risk to patients, and result in massive costs that are often not recoverable. At an estimated 28% success rate, the current level of investment defies management logic. This paper asserts that there are "chasms" in IT implementations that represent risky stages in the process. Contributors to the chasms are classified into four categories: design, management, organization, and assessment. The American College of Medical Informatics symposium participants recommend bold action to better understand problems and challenges in implementation and to improve the ability of organizations to bridge these implementation chasms. The bold action includes the creation of a Team Science for Implementation strategy that allows for participation from multiple institutions to address the long standing and costly implementation issues. The outcomes of this endeavor will include a new focus on interdisciplinary research and an inter-organizational knowledge base of strategies and methods to optimize implementations and subsequent achievement of organizational objectives.

Brain functional BOLD perturbation modelling for forward fMRI and inverse mapping

PubMed Central

Robinson, Jennifer; Calhoun, Vince

2018-01-01

Purpose To computationally separate dynamic brain functional BOLD responses from static background in a brain functional activity for forward fMRI signal analysis and inverse mapping. Methods A brain functional activity is represented in terms of magnetic source by a perturbation model: χ = χ0 +δχ, with δχ for BOLD magnetic perturbations and χ0 for background. A brain fMRI experiment produces a timeseries of complex-valued images (T2* images), whereby we extract the BOLD phase signals (denoted by δP) by a complex division. By solving an inverse problem, we reconstruct the BOLD δχ dataset from the δP dataset, and the brain χ distribution from a (unwrapped) T2* phase image. Given a 4D dataset of task BOLD fMRI, we implement brain functional mapping by temporal correlation analysis. Results Through a high-field (7T) and high-resolution (0.5mm in plane) task fMRI experiment, we demonstrated in detail the BOLD perturbation model for fMRI phase signal separation (P + δP) and reconstructing intrinsic brain magnetic source (χ and δχ). We also provided to a low-field (3T) and low-resolution (2mm) task fMRI experiment in support of single-subject fMRI study. Our experiments show that the δχ-depicted functional map reveals bidirectional BOLD χ perturbations during the task performance. Conclusions The BOLD perturbation model allows us to separate fMRI phase signal (by complex division) and to perform inverse mapping for pure BOLD δχ reconstruction for intrinsic functional χ mapping. The full brain χ reconstruction (from unwrapped fMRI phase) provides a new brain tissue image that allows to scrutinize the brain tissue idiosyncrasy for the pure BOLD δχ response through an automatic function/structure co-localization. PMID:29351339

Negative BOLD in default-mode structures measured with EEG-MREG is larger in temporal than extra-temporal epileptic spikes

PubMed Central

Jacobs, Julia; Menzel, Antonia; Ramantani, Georgia; Körbl, Katharina; Assländer, Jakob; Schulze-Bonhage, Andreas; Hennig, Jürgen; LeVan, Pierre

2014-01-01

Introduction: EEG-fMRI detects BOLD changes associated with epileptic interictal discharges (IED) and can identify epileptogenic networks in epilepsy patients. Besides positive BOLD changes, negative BOLD changes have sometimes been observed in the default-mode network, particularly using group analysis. A new fast fMRI sequence called MREG (Magnetic Resonance Encephalography) shows increased sensitivity to detect IED-related BOLD changes compared to the conventional EPI sequence, including frequent occurrence of negative BOLD responses in the DMN. The present study quantifies the concordance between the DMN and negative BOLD related to IEDs of temporal and extra-temporal origin. Methods: Focal epilepsy patients underwent simultaneous EEG-MREG. Areas of overlap were calculated between DMN regions, defined as precuneus, posterior cingulate, bilateral inferior parietal and mesial prefrontal cortices according to a standardized atlas, and significant negative BOLD changes revealed by an event-related analysis based on the timings of IED seen on EEG. Correlation between IED number/lobe of origin and the overlap were calculated. Results: 15 patients were analyzed, some showing IED over more than one location resulting in 30 different IED types. The average overlap between negative BOLD and DMN was significantly larger in temporal (23.7 ± 19.6 cm3) than extra-temporal IEDs (7.4 ± 5.1 cm3, p = 0.008). There was no significant correlation between the number of IEDs and the overlap between DMN structures and negative BOLD areas. Discussion: MREG results in an increased sensitivity to detect negative BOLD responses related to focal IED in single patients, with responses often occurring in DMN regions. In patients with high overlap with the DMN, this suggests that epileptic IEDs may be associated with a brief decrease in attention and cognitive ability. Interestingly this observation was not dependent on the frequency of IED but more common in IED of temporal origin. PMID:25477775

Origins of intersubject variability of blood oxygenation level dependent and arterial spin labeling fMRI: implications for quantification of brain activity.

PubMed

Gaxiola-Valdez, Ismael; Goodyear, Bradley G

2012-12-01

Accurate localization of brain activity using blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) has been challenged because of the large BOLD signal within distal veins. Arterial spin labeling (ASL) techniques offer greater sensitivity to the microvasculature but possess low temporal resolution and limited brain coverage. In this study, we show that the physiological origins of BOLD and ASL depend on whether percent change or statistical significance is being considered. For BOLD and ASL fMRI data collected during a simple unilateral hand movement task, we found that in the area of the contralateral motor cortex the centre of gravity (CoG) of the intersubject coefficient of variation (CV) of BOLD fMRI was near the brain surface for percent change in signal, whereas the CoG of the intersubject CV for Z-score was in close proximity of sites of brain activity for both BOLD and ASL. These findings suggest that intersubject variability of BOLD percent change is vascular in origin, whereas the origin of inter-subject variability of Z-score is neuronal for both BOLD and ASL. For longer duration tasks (12 s or greater), however, there was a significant correlation between BOLD and ASL percent change, which was not evident for short duration tasks (6 s). These findings suggest that analyses directly comparing percent change in BOLD signal between pre-defined regions of interest using short duration stimuli, as for example in event-related designs, may be heavily weighted by large-vessel responses rather than neuronal responses. Copyright © 2012 Elsevier Inc. All rights reserved.

The role of the GABAergic and dopaminergic systems in the brain response to an intragastric load of alcohol in conscious rats.

PubMed

Tsurugizawa, T; Uematsu, A; Uneyama, H; Torii, K

2010-12-01

The brain's response to ethanol intake has been extensively investigated using electrophysiological recordings, brain lesion techniques, and c-Fos immunoreactivity. However, few studies have investigated this phenomenon using functional magnetic resonance imaging (fMRI). In the present study, we used fMRI to investigate the blood oxygenation level-dependent (BOLD) signal response to an intragastric (IG) load of ethanol in conscious, ethanol-naive rats. An intragastrically infused 10% ethanol solution induced a significant decrease in the intensity of the BOLD signal in several regions of the brain, including the bilateral amygdala (AMG), nucleus accumbens (NAc), hippocampus, ventral pallidum, insular cortex, and cingulate cortex, and an increase in the BOLD signal in the ventral tegmental area (VTA) and hypothalamic regions. Treatment with bicuculline, which is an antagonist of the gamma-aminobutyric acid A (GABA(A)) receptor, increased the BOLD signal intensity in the regions that had shown decreases in the BOLD signal after the IG infusion of 10% ethanol solution, but it did not affect the BOLD signal increase in the hypothalamus. Treatment with SCH39166, which is an antagonist of D1-like receptors, eliminated the increase in the BOLD signal intensity in the hypothalamic areas but did not affect the BOLD signal decrease following the 10% ethanol infusion. These results indicate that an IG load of ethanol caused both a GABA(A) receptor-mediated BOLD decrease in the limbic system and the cortex and a D1-like receptor-mediated BOLD increase in the hypothalamic regions in ethanol-naive rats. Copyright © 2010 IBRO. Published by Elsevier Ltd. All rights reserved.

Placental baseline conditions modulate the hyperoxic BOLD-MRI response.

PubMed

Sinding, Marianne; Peters, David A; Poulsen, Sofie S; Frøkjær, Jens B; Christiansen, Ole B; Petersen, Astrid; Uldbjerg, Niels; Sørensen, Anne

2018-01-01

Human pregnancies complicated by placental dysfunction may be characterized by a high hyperoxic Blood oxygen level-dependent (BOLD) MRI response. The pathophysiology behind this phenomenon remains to be established. The aim of this study was to evaluate whether it is associated with altered placental baseline conditions, including a lower oxygenation and altered tissue morphology, as estimated by the placental transverse relaxation time (T2*). We included 49 normal pregnancies (controls) and 13 pregnancies complicated by placental dysfunction (cases), defined by a birth weight < 10th percentile in combination with placental pathological signs of vascular malperfusion. During maternal oxygen inhalation, we measured the relative ΔBOLD response ((hyperoxic BOLD - baseline BOLD)/baseline BOLD) from a dynamic single-echo gradient-recalled echo (GRE) MRI sequence and the absolute ΔT2* (hyperoxic T2*- baseline T2*) from breath-hold multi-echo GRE sequences. In the control group, the relative ΔBOLD response increased during gestation from 5% in gestational week 20 to 20% in week 40. In the case group, the relative ΔBOLD response was significantly higher (mean Z-score 4.94; 95% CI 2.41, 7.47). The absolute ΔT2*, however, did not differ between controls and cases (p = 0.37), whereas the baseline T2* was lower among cases (mean Z-score -3.13; 95% CI -3.94, -2.32). Furthermore, we demonstrated a strong negative linear correlation between the Log 10 ΔBOLD response and the baseline T2* (r = -0.88, p < 0.0001). The high hyperoxic ΔBOLD response demonstrated in pregnancies complicated by placental dysfunction may simply reflect altered baseline conditions, as the absolute increase in placental oxygenation (ΔT2*) does not differ between groups. Copyright © 2017 Elsevier Ltd. All rights reserved.

An fMRI Study on Conceptual, Grammatical, and Morpho-Phonological Processing

ERIC Educational Resources Information Center

Longoni, F.; Grande, M.; Hendrich, V.; Kastrau, F.; Huber, W.

2005-01-01

The aim of the present study was to determine whether processing of syntactic word information (lemma) is subserved by the same neural substrate as processing of conceptual or word form information (lexeme). We measured BOLD responses in 14 native speakers of German in three different decision tasks, each focussing specifically on one level of…

An in vitro study on metabolism of 17beta-boldenone and boldione using cattle liver and kidney subcellular fractions.

PubMed

Merlanti, R; Gallina, G; Capolongo, F; Contiero, L; Biancotto, G; Dacasto, M; Montesissa, C

2007-03-14

17Beta-boldenone (17beta-BOLD) and Boldione (ADD) are steroid compounds with androgenic activity, likely to be used as growth promoters in cattle. Different studies still on-going aiming to distinguish between "natural" occurrence or illegal BOLD source had already indicated that their metabolism in cattle is of relevant significance. To identify metabolites as in vivo markers to support the thesis of exogenous administration, a further approach to the in vitro biotransformation of 17beta-BOLD and ADD was performed using different subcellular fractions obtained from both liver and kidney of untreated cattle. Polar and non-polar metabolites obtained from incubated parent compounds were formerly separated by high performance liquid chromatography (HPLC) elution and successively identified by liquid chromatography tandem mass spectrometry (LC-MS/MS) detection. The bovine liver was the target tissue of the main metabolic reaction transforming 17beta-BOLD to ADD and vice versa. The presence of 6beta-hydroxy-17beta-BOLD, produced from both compounds when NADPH was added as cofactors to liver post mitochondrial and microsomal fractions suggests that cytochrome P450-dependent enzymes could be involved in the biotransformation, as it occurs for 6beta-hydroxylation of 17beta-testosterone. The results indicated that the urinary excretion profile in vivo of 6beta-hydroxy-17beta-BOLD and 16alpha-hydroxy-17beta-BOLD could be studied together with 17alpha- and 17beta-BOLD as putative markers of BOLD treatment in cattle.

Anticipated improvement in laser beam uniformity using distributed phase plates with quasirandom patterns

DOE Office of Scientific and Technical Information (OSTI.GOV)

Epstein, R.; Skupsky, S.

1990-08-01

The uniformity of focused laser beams, that has been modified with randomly phased distributed phase plates (C. B. Burckhardt, Appl. Opt. {bold 9}, 695 (1970); Kato and Mima, Appl. Phys. B {bold 29}, 186 (1982); Kato {ital et} {ital al}., Phys. Rev. Lett. {bold 53}, 1057 (1984); LLE Rev. {bold 33}, 1 (1987)), can be improved further by constructing patterns of phase elements which minimize phase correlations over small separations. Long-wavelength nonuniformities in the intensity distribution, which are relatively difficult to overcome in the target by thermal smoothing and in the laser by, e.g., spectral dispersion (Skupsky {ital et} {italmore » al}., J. Appl. Phys. {bold 66}, 3456 (1989); LLE Rev. {bold 36}, 158 (1989); {bold 37}, 29 (1989); {bold 37}, 40 (1989)), result largely from short-range phase correlations between phase plate elements. To reduce the long-wavelength structure, we have constructed phase patterns with smaller short-range correlations than would occur randomly. Calculations show that long-wavelength nonuniformities in single-beam intensity patterns can be reduced with these masks when the intrinsic phase error of the beam falls below certain limits. We show the effect of this improvement on uniformity for spherical irradiation by a multibeam system.« less

Evolutionary Dynamics of Fearfulness and Boldness: A Stochastic Simulation Model

PubMed Central

Lu, Nan; Ji, Ting; Zhang, Jia-Hua; Sun, Yue-Hua; Tao, Yi

2012-01-01

A stochastic simulation model is investigated for the evolution of anti-predator behavior in birds. The main goal is to reveal the effects of population size, predation threats, and energy lost per escape on the evolutionary dynamics of fearfulness and boldness. Two pure strategies, fearfulness and boldness, are assumed to have different responses for the predator attacks and nonlethal disturbance. On the other hand, the co-existence mechanism of fearfulness and boldness is also considered. For the effects of total population size, predation threats, and energy lost per escape, our main results show that: (i) the fearful (bold) individuals will be favored in a small (large) population, i.e. in a small (large) population, the fearfulness (boldness) can be considered to be an ESS; (ii) in a population with moderate size, fearfulness would be favored under moderate predator attacks; and (iii) although the total population size is the most important factor for the evolutionary dynamics of both fearful and bold individuals, the small energy lost per escape enables the fearful individuals to have the ability to win the advantage even in a relatively large population. Finally, we show also that the co-existence of fearful and bold individuals is possible when the competitive interactions between individuals are introduced. PMID:22412859

Evolutionary dynamics of fearfulness and boldness: a stochastic simulation model.

PubMed

Lu, Nan; Ji, Ting; Zhang, Jia-Hua; Sun, Yue-Hua; Tao, Yi

2012-01-01

A stochastic simulation model is investigated for the evolution of anti-predator behavior in birds. The main goal is to reveal the effects of population size, predation threats, and energy lost per escape on the evolutionary dynamics of fearfulness and boldness. Two pure strategies, fearfulness and boldness, are assumed to have different responses for the predator attacks and nonlethal disturbance. On the other hand, the co-existence mechanism of fearfulness and boldness is also considered. For the effects of total population size, predation threats, and energy lost per escape, our main results show that: (i) the fearful (bold) individuals will be favored in a small (large) population, i.e. in a small (large) population, the fearfulness (boldness) can be considered to be an ESS; (ii) in a population with moderate size, fearfulness would be favored under moderate predator attacks; and (iii) although the total population size is the most important factor for the evolutionary dynamics of both fearful and bold individuals, the small energy lost per escape enables the fearful individuals to have the ability to win the advantage even in a relatively large population. Finally, we show also that the co-existence of fearful and bold individuals is possible when the competitive interactions between individuals are introduced.

Evolutionary dynamics of fearfulness and boldness.

PubMed

Ji, Ting; Zhang, Boyu; Sun, Yuehua; Tao, Yi

2009-02-21

A negative relationship between reproductive effort and survival is consistent with life-history. Evolutionary dynamics and evolutionarily stable strategy (ESS) for the trade-off between survival and reproduction are investigated using a simple model with two phenotypes, fearfulness and boldness. The dynamical stability of the pure strategy model and analysis of ESS conditions reveal that: (i) the simple coexistence of fearfulness and boldness is impossible; (ii) a small population size is favorable to fearfulness, but a large population size is favorable to boldness, i.e., neither fearfulness, nor boldness is always favored by natural selection; and (iii) the dynamics of population density is crucial for a proper understanding of the strategy dynamics.

Resting-state fMRI correlations: From link-wise unreliability to whole brain stability.

PubMed

Pannunzi, Mario; Hindriks, Rikkert; Bettinardi, Ruggero G; Wenger, Elisabeth; Lisofsky, Nina; Martensson, Johan; Butler, Oisin; Filevich, Elisa; Becker, Maxi; Lochstet, Martyna; Kühn, Simone; Deco, Gustavo

2017-08-15

The functional architecture of spontaneous BOLD fluctuations has been characterized in detail by numerous studies, demonstrating its potential relevance as a biomarker. However, the systematic investigation of its consistency is still in its infancy. Here, we analyze within- and between-subject variability and test-retest reliability of resting-state functional connectivity (FC) in a unique data set comprising multiple fMRI scans (42) from 5 subjects, and 50 single scans from 50 subjects. We adopt a statistical framework that enables us to identify different sources of variability in FC. We show that the low reliability of single links can be significantly improved by using multiple scans per subject. Moreover, in contrast to earlier studies, we show that spatial heterogeneity in FC reliability is not significant. Finally, we demonstrate that despite the low reliability of individual links, the information carried by the whole-brain FC matrix is robust and can be used as a functional fingerprint to identify individual subjects from the population. Copyright © 2017 Elsevier Inc. All rights reserved.

Age, sex and reproductive status affect boldness in dogs.

PubMed

Starling, Melissa J; Branson, Nicholas; Thomson, Peter C; McGreevy, Paul D

2013-09-01

Boldness in dogs is believed to be one end of the shy-bold axis, representing a super-trait. Several personality traits fall under the influence of this super-trait. Previous studies have found that boldness is affected by breed and breed groups, influences performance in sporting dogs, and is affected in some cases by the sex of the dogs. This study investigated the effects of dog age, sex and reproductive status on boldness in dogs by way of a dog personality survey circulated amongst Australian dog owners. Age had a significant effect on boldness (F=4.476; DF=16,758; P<0.001), with boldness decreasing with age in years. Males were bolder than females (F=19.219; DF=1,758; P<0.001) and entire dogs were bolder than neutered dogs (F=4.330; DF=1,758; P<0.038). The study indicates how behaviour may change in adult dogs as they age and adds to the literature on how sex and reproductive status may affect personality in dogs. Copyright © 2013 Elsevier Ltd. All rights reserved.

Does boldness explain vulnerability to angling in Eurasian perch Perca fluviatilis?

PubMed

Vainikka, Anssi; Tammela, Ilkka; Hyvärinen, Pekka

2016-04-01

Consistent individual differences (CIDs) in behavior are of interest to both basic and applied research, because any selection acting on them could induce evolution of animal behavior. It has been suggested that CIDs in the behavior of fish might explain individual differences in vulnerability to fishing. If so, fishing could impose selection on fish behavior. In this study, we assessed boldness-indicating behaviors of Eurasian perch Perca fluviatilis using individually conducted experiments measuring the time taken to explore a novel arena containing predator (burbot, Lota lota ) cues. We studied if individual differences in boldness would explain vulnerability of individually tagged perch to experimental angling in outdoor ponds, or if fishing would impose selection on boldness-indicating behavior. Perch expressed repeatable individual differences in boldness-indicating behavior but the individual boldness-score (the first principal component) obtained using principal component analysis combining all the measured behavioral responses did not explain vulnerability to experimental angling. Instead, large body size appeared as the only statistically significant predictor of capture probability. Our results suggest that angling is selective for large size, but not always selective for high boldness.

Does boldness explain vulnerability to angling in Eurasian perch Perca fluviatilis?

PubMed Central

Vainikka, Anssi; Tammela, Ilkka; Hyvärinen, Pekka

2016-01-01

Abstract Consistent individual differences (CIDs) in behavior are of interest to both basic and applied research, because any selection acting on them could induce evolution of animal behavior. It has been suggested that CIDs in the behavior of fish might explain individual differences in vulnerability to fishing. If so, fishing could impose selection on fish behavior. In this study, we assessed boldness-indicating behaviors of Eurasian perch Perca fluviatilis using individually conducted experiments measuring the time taken to explore a novel arena containing predator (burbot, Lota lota) cues. We studied if individual differences in boldness would explain vulnerability of individually tagged perch to experimental angling in outdoor ponds, or if fishing would impose selection on boldness-indicating behavior. Perch expressed repeatable individual differences in boldness-indicating behavior but the individual boldness-score (the first principal component) obtained using principal component analysis combining all the measured behavioral responses did not explain vulnerability to experimental angling. Instead, large body size appeared as the only statistically significant predictor of capture probability. Our results suggest that angling is selective for large size, but not always selective for high boldness. PMID:29491897

Evidence for unlimited capacity processing of simple features in visual cortex

PubMed Central

White, Alex L.; Runeson, Erik; Palmer, John; Ernst, Zachary R.; Boynton, Geoffrey M.

2017-01-01

Performance in many visual tasks is impaired when observers attempt to divide spatial attention across multiple visual field locations. Correspondingly, neuronal response magnitudes in visual cortex are often reduced during divided compared with focused spatial attention. This suggests that early visual cortex is the site of capacity limits, where finite processing resources must be divided among attended stimuli. However, behavioral research demonstrates that not all visual tasks suffer such capacity limits: The costs of divided attention are minimal when the task and stimulus are simple, such as when searching for a target defined by orientation or contrast. To date, however, every neuroimaging study of divided attention has used more complex tasks and found large reductions in response magnitude. We bridged that gap by using functional magnetic resonance imaging to measure responses in the human visual cortex during simple feature detection. The first experiment used a visual search task: Observers detected a low-contrast Gabor patch within one or four potentially relevant locations. The second experiment used a dual-task design, in which observers made independent judgments of Gabor presence in patches of dynamic noise at two locations. In both experiments, blood-oxygen level–dependent (BOLD) signals in the retinotopic cortex were significantly lower for ignored than attended stimuli. However, when observers divided attention between multiple stimuli, BOLD signals were not reliably reduced and behavioral performance was unimpaired. These results suggest that processing of simple features in early visual cortex has unlimited capacity. PMID:28654964

Amphetamine sensitization alters reward processing in the human striatum and amygdala.

PubMed

O'Daly, Owen G; Joyce, Daniel; Tracy, Derek K; Azim, Adnan; Stephan, Klaas E; Murray, Robin M; Shergill, Sukhwinder S

2014-01-01

Dysregulation of mesolimbic dopamine transmission is implicated in a number of psychiatric illnesses characterised by disruption of reward processing and goal-directed behaviour, including schizophrenia, drug addiction and impulse control disorders associated with chronic use of dopamine agonists. Amphetamine sensitization (AS) has been proposed to model the development of this aberrant dopamine signalling and the subsequent dysregulation of incentive motivational processes. However, in humans the effects of AS on the dopamine-sensitive neural circuitry associated with reward processing remains unclear. Here we describe the effects of acute amphetamine administration, following a sensitising dosage regime, on blood oxygen level dependent (BOLD) signal in dopaminoceptive brain regions during a rewarded gambling task performed by healthy volunteers. Using a randomised, double-blind, parallel-groups design, we found clear evidence for sensitization to the subjective effects of the drug, while rewarded reaction times were unchanged. Repeated amphetamine exposure was associated with reduced dorsal striatal BOLD signal during decision making, but enhanced ventromedial caudate activity during reward anticipation. The amygdala BOLD response to reward outcomes was blunted following repeated amphetamine exposure. Positive correlations between subjective sensitization and changes in anticipation- and outcome-related BOLD signal were seen for the caudate nucleus and amygdala, respectively. These data show for the first time in humans that AS changes the functional impact of acute stimulant exposure on the processing of reward-related information within dopaminoceptive regions. Our findings accord with pathophysiological models which implicate aberrant dopaminergic modulation of striatal and amygdala activity in psychosis and drug-related compulsive disorders.

Assessment of sexual orientation using the hemodynamic brain response to visual sexual stimuli.

PubMed

Ponseti, Jorge; Granert, Oliver; Jansen, Olav; Wolff, Stephan; Mehdorn, Hubertus; Bosinski, Hartmut; Siebner, Hartwig

2009-06-01

The assessment of sexual orientation is of importance to the diagnosis and treatment of sex offenders and paraphilic disorders. Phallometry is considered gold standard in objectifying sexual orientation, yet this measurement has been criticized because of its intrusiveness and limited reliability. To evaluate whether the spatial response pattern to sexual stimuli as revealed by a change in blood oxygen level-dependent (BOLD) signal can be used for individual classification of sexual orientation. We used a preexisting functional MRI (fMRI) data set that had been acquired in a nonclinical sample of 12 heterosexual men and 14 homosexual men. During fMRI, participants were briefly exposed to pictures of same-sex and opposite-sex genitals. Data analysis involved four steps: (i) differences in the BOLD response to female and male sexual stimuli were calculated for each subject; (ii) these contrast images were entered into a group analysis to calculate whole-brain difference maps between homosexual and heterosexual participants; (iii) a single expression value was computed for each subject expressing its correspondence to the group result; and (iv) based on these expression values, Fisher's linear discriminant analysis and the kappa-nearest neighbor classification method were used to predict the sexual orientation of each subject. Sensitivity and specificity of the two classification methods in predicting individual sexual orientation. Both classification methods performed well in predicting individual sexual orientation with a mean accuracy of >85% (Fisher's linear discriminant analysis: 92% sensitivity, 85% specificity; kappa-nearest neighbor classification: 88% sensitivity, 92% specificity). Despite the small sample size, the functional response patterns of the brain to sexual stimuli contained sufficient information to predict individual sexual orientation with high accuracy. These results suggest that fMRI-based classification methods hold promise for the diagnosis of paraphilic disorders (e.g., pedophilia).

Modulation of Fgfr1a signaling in zebrafish reveals a genetic basis for the aggression-boldness syndrome.

PubMed

Norton, William H J; Stumpenhorst, Katharina; Faus-Kessler, Theresa; Folchert, Anja; Rohner, Nicolas; Harris, Matthew P; Callebert, Jacques; Bally-Cuif, Laure

2011-09-28

Behavioral syndromes are suites of two or more behaviors that correlate across environmental contexts. The aggression-boldness syndrome links aggression, boldness, and exploratory activity in a novel environment. Although aggression-boldness has been described in many animals, the mechanism linking its behavioral components is not known. Here we show that mutation of the gene encoding fibroblast growth factor receptor 1a (fgfr1a) simultaneously increases aggression, boldness, and exploration in adult zebrafish. We demonstrate that altered Fgf signaling also results in reduced brain histamine levels in mutants. Pharmacological increase of histamine signaling is sufficient to rescue the behavioral phenotype of fgfr1a mutants. Together, we show that a single genetic locus can underlie the aggression-boldness behavioral syndrome. We also identify one of the neurotransmitter pathways that may mediate clustering of these behaviors.

Boldness predicts social status in zebrafish (Danio rerio).

PubMed

Dahlbom, S Josefin; Lagman, David; Lundstedt-Enkel, Katrin; Sundström, L Fredrik; Winberg, Svante

2011-01-01

This study explored if boldness could be used to predict social status. First, boldness was assessed by monitoring individual zebrafish behaviour in (1) an unfamiliar barren environment with no shelter (open field), (2) the same environment when a roof was introduced as a shelter, and (3) when the roof was removed and an unfamiliar object (Lego® brick) was introduced. Next, after a resting period of minimum one week, social status of the fish was determined in a dyadic contest and dominant/subordinate individuals were determined as the winner/loser of two consecutive contests. Multivariate data analyses showed that males were bolder than females and that the behaviours expressed by the fish during the boldness tests could be used to predict which fish would later become dominant and subordinate in the ensuing dyadic contest. We conclude that bold behaviour is positively correlated to dominance in zebrafish and that boldness is not solely a consequence of social dominance.

Boldness Predicts Social Status in Zebrafish (Danio rerio)

PubMed Central

Dahlbom, S. Josefin; Lagman, David; Lundstedt-Enkel, Katrin; Sundström, L. Fredrik; Winberg, Svante

2011-01-01

This study explored if boldness could be used to predict social status. First, boldness was assessed by monitoring individual zebrafish behaviour in (1) an unfamiliar barren environment with no shelter (open field), (2) the same environment when a roof was introduced as a shelter, and (3) when the roof was removed and an unfamiliar object (Lego® brick) was introduced. Next, after a resting period of minimum one week, social status of the fish was determined in a dyadic contest and dominant/subordinate individuals were determined as the winner/loser of two consecutive contests. Multivariate data analyses showed that males were bolder than females and that the behaviours expressed by the fish during the boldness tests could be used to predict which fish would later become dominant and subordinate in the ensuing dyadic contest. We conclude that bold behaviour is positively correlated to dominance in zebrafish and that boldness is not solely a consequence of social dominance. PMID:21858168

Plasticity of boldness in rainbow trout, Oncorhynchus mykiss: do hunger and predation influence risk-taking behaviour?

PubMed

Thomson, Jack S; Watts, Phillip C; Pottinger, Tom G; Sneddon, Lynne U

2012-05-01

Boldness, a measure of an individual's propensity for taking risks, is an important determinant of fitness but is not necessarily a fixed trait. Dependent upon an individual's state, and given certain contexts or challenges, individuals may be able to alter their inclination to be bold or shy in response. Furthermore, the degree to which individuals can modulate their behaviour has been linked with physiological responses to stress. Here we attempted to determine whether bold and shy rainbow trout, Oncorhynchus mykiss, can exhibit behavioural plasticity in response to changes in state (nutritional availability) and context (predation threat). Individual trout were initially assessed for boldness using a standard novel object paradigm; subsequently, each day for one week fish experienced either predictable, unpredictable, or no simulated predator threat in combination with a high (2% body weight) or low (0.15%) food ration, before being reassessed for boldness. Bold trout were generally more plastic, altering levels of neophobia and activity relevant to the challenge, whereas shy trout were more fixed and remained shy. Increased predation risk generally resulted in an increase in the expression of three candidate genes linked to boldness, appetite regulation and physiological stress responses - ependymin, corticotrophin releasing factor and GABA(A) - but did not produce a significant increase in plasma cortisol. The results suggest a divergence in the ability of bold and shy trout to alter their behavioural profiles in response to internal and exogenous factors, and have important implications for our understanding of the maintenance of different behavioural phenotypes in natural populations. Copyright © 2012 Elsevier Inc. All rights reserved.

Individual boldness is linked to protective shell shape in aquatic snails.

PubMed

Ahlgren, Johan; Chapman, Ben B; Nilsson, P Anders; Brönmark, Christer

2015-04-01

The existence of consistent individual differences in behaviour ('animal personality') has been well documented in recent years. However, how such individual variation in behaviour is maintained over evolutionary time is an ongoing conundrum. A well-studied axis of animal personality is individual variation along a bold-shy continuum, where individuals differ consistently in their propensity to take risks. A predation-risk cost to boldness is often assumed, but also that the reproductive benefits associated with boldness lead to equivalent fitness outcomes between bold and shy individuals over a lifetime. However, an alternative or complementary explanation may be that bold individuals phenotypically compensate for their risky lifestyle to reduce predation costs, for instance by investing in more pronounced morphological defences. Here, we investigate the 'phenotypic compensation' hypothesis, i.e. that bold individuals exhibit more pronounced anti-predator defences than shy individuals, by relating shell shape in the aquatic snail Radix balthica to an index of individual boldness. Our analyses find a strong relationship between risk-taking propensity and shell shape in this species, with bolder individuals exhibiting a more defended shell shape than shy individuals. We suggest that this supports the 'phenotypic compensation' hypothesis and sheds light on a previously poorly studied mechanism to promote the maintenance of personality variation among animals. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

Reduction of time-averaged irradiation speckle nonuniformity in laser-driven plasmas due to target ablation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Epstein, R.

1997-09-01

In inertial confinement fusion (ICF) experiments, irradiation uniformity is improved by passing laser beams through distributed phase plates (DPPs), which produce focused intensity profiles with well-controlled, reproducible envelopes modulated by fine random speckle. [C. B. Burckhardt, Appl. Opt. {bold 9}, 695 (1970); Y. Kato and K. Mima, Appl. Phys. B {bold 29}, 186 (1982); Y. Kato {ital et al.}, Phys. Rev. Lett. {bold 53}, 1057 (1984); Laboratory for Laser Energetics LLE Review 33, NTIS Document No. DOE/DP/40200-65, 1987 (unpublished), p. 1; Laboratory for Laser Energetics LLE Review 63, NTIS Document No. DOE/SF/19460-91, 1995 (unpublished), p. 1.] A uniformly ablating plasmamore » atmosphere acts to reduce the contribution of the speckle to the time-averaged irradiation nonuniformity by causing the intensity distribution to move relative to the absorption layer of the plasma. This occurs most directly as the absorption layer in the plasma moves with the ablation-driven flow, but it is shown that the effect of the accumulating ablated plasma on the phase of the laser light also makes a quantitatively significant contribution. Analytical results are obtained using the paraxial approximation applied to the beam propagation, and a simple statistical model is assumed for the properties of DPPs. The reduction in the time-averaged spatial spectrum of the speckle due to these effects is shown to be quantitatively significant within time intervals characteristic of atmospheric hydrodynamics under typical ICF irradiation intensities. {copyright} {ital 1997 American Institute of Physics.}« less

Quantification of Load Dependent Brain Activity in Parametric N-Back Working Memory Tasks using Pseudo-continuous Arterial Spin Labeling (pCASL) Perfusion Imaging.

PubMed

Zou, Qihong; Gu, Hong; Wang, Danny J J; Gao, Jia-Hong; Yang, Yihong

2011-04-01

Brain activation and deactivation induced by N-back working memory tasks and their load effects have been extensively investigated using positron emission tomography (PET) and blood-oxygenation level dependent (BOLD) functional magnetic resonance imaging (fMRI). However, the underlying mechanisms of BOLD fMRI are still not completely understood and PET imaging requires injection of radioactive tracers. In this study, a pseudo-continuous arterial spin labeling (pCASL) perfusion imaging technique was used to quantify cerebral blood flow (CBF), a well understood physiological index reflective of cerebral metabolism, in N-back working memory tasks. Using pCASL, we systematically investigated brain activation and deactivation induced by the N-back working memory tasks and further studied the load effects on brain activity based on quantitative CBF. Our data show increased CBF in the fronto-parietal cortices, thalamus, caudate, and cerebellar regions, and decreased CBF in the posterior cingulate cortex and medial prefrontal cortex, during the working memory tasks. Most of the activated/deactivated brain regions show an approximately linear relationship between CBF and task loads (0, 1, 2 and 3 back), although several regions show non-linear relationships (quadratic and cubic). The CBF-based spatial patterns of brain activation/deactivation and load effects from this study agree well with those obtained from BOLD fMRI and PET techniques. These results demonstrate the feasibility of ASL techniques to quantify human brain activity during high cognitive tasks, suggesting its potential application to assessing the mechanisms of cognitive deficits in neuropsychiatric and neurological disorders.

Contrasting neural effects of aging on proactive and reactive response inhibition.

PubMed

Bloemendaal, Mirjam; Zandbelt, Bram; Wegman, Joost; van de Rest, Ondine; Cools, Roshan; Aarts, Esther

2016-10-01

Two distinct forms of response inhibition may underlie observed deficits in response inhibition in aging. We assessed whether age-related neurocognitive impairments in response inhibition reflect deficient reactive inhibition (outright stopping) or also deficient proactive inhibition (anticipatory response slowing), which might be particularly evident with high information load. We used functional magnetic resonance imaging in young (n = 25, age range 18-32) and older adults (n = 23, 61-74) with a stop-signal task. Relative to young adults, older adults exhibited impaired reactive inhibition (i.e., longer stop-signal reaction time) and increased blood oxygen level-dependent (BOLD) signal for successful versus unsuccessful inhibition in the left frontal cortex and cerebellum. Furthermore, older adults also exhibited impaired proactive slowing, but only as a function of information load. This load-dependent behavioral deficit was accompanied by a failure to increase blood oxygen level-dependent (BOLD) signal under high information load in lateral frontal cortex, presupplementary motor area and striatum. Our findings suggest that inhibitory deficits in older adults are caused both by reduced stopping abilities and by diminished preparation capacity during information overload. Copyright © 2016 Elsevier Inc. All rights reserved.

To be so bold: boldness is repeatable and related to within individual behavioural variability in North Island robins.

PubMed

He, Ruchuan; Pagani-Núñez, Emilio; Chevallier, Clément; Barnett, Craig R A

2017-07-01

Behavioural research traditionally focusses on the mean responses of a group of individuals rather than variation in behaviour around the mean or among individuals. However, examining the variation in behaviour among and within individuals may also yield important insights into the evolution and maintenance of behaviour. Repeatability is the most commonly used measure of variability among individuals in behavioural research. However, there are other forms of variation within populations that have received less attention. One such measure is intraindividual variation in behaviour (IIV), which is a short-term fluctuation of within-individual behaviour. Such variation in behaviour might be important during interactions because it could decrease the ability of conspecific and heterospecific individuals to predict the behaviour of the subject, thus increasing the cost of the interaction. In this experiment, we made repeated measures of the latency of North Island robins to attack a prey in a novel situation (a form of boldness) and examined (i) repeatability of boldness (the propensity to take a risk), (ii) IIV of boldness, and (iii) whether there was a significant relationship between these two traits (a behavioural syndrome). We found that boldness was highly repeatable, that there were high levels of IIV in boldness, and that there was a negative relationship between boldness and IIV in boldness. This suggests that despite high levels of repeatability for this behaviour, there were also still significant differences in IIV among different individuals within the population. Moreover, bolder individuals had significantly less IIV in their boldness, which suggests that they were forming routines (which reduces behavioural variability) compared to shyer individuals. Our results definitively demonstrate that IIV itself varies across individuals and is linked with key behavioural traits, and we argue for the importance of future studies aimed at understanding its causes and consequences for behavioural interactions. Copyright © 2017 Elsevier B.V. All rights reserved.

Oxygen-induced frequency shifts in hyperoxia: a significant component of BOLD signal.

PubMed

Song, Youngkyu; Cho, Gyunggoo; Chun, Song-I; Baek, Jin Hee; Cho, HyungJoon; Kim, Young Ro; Park, Sung Bin; Kim, Jeong Kon

2014-07-01

In comparison to the well-documented significance of intravascular deoxyhemoglobin (deoxyHgb), the effects of dissolved oxygen on the blood-oxygen-level-dependent (BOLD) signal have not been widely reported. Based on the fact that the prolonged inspiration of high oxygen fraction gas can result in up to a sixfold increase of the baseline tissue oxygenation, the current study focused on the influence of dissolved oxygen on the BOLD signal during hyperoxia. As results, our in vitro study revealed that the r1 and r2 (relaxivities) of the oxygen-treated serum were 0.22 mM(-1) · s(-1) and 0.19 mM(-1) · s(-1) , respectively. In an in vivo experiment, hyperoxic respiration induced negative BOLD contrast (i.e. signal decrease) in 18-42% of measured brain regions, voxels with accompanying significant decreases in both the T(*)2 (-12.1% to -19.4%) and T1 (-5.8% to -3.3%) relaxation times. In contrast, the T(*)2 relaxation time significantly increased (11.2% to 14.0%) for the voxels displaying positive BOLD contrast (in 41-50% of the measured brain), which reflected a hyperoxygenation-induced reduction in tissue deoxyHgb concentration. These data imply that hyperoxia-driven BOLD signal changes are primarily determined by the counteracting effects of extravascular oxygen and intravascular deoxyHgb. Oxygen-induced magnetic susceptibility was further demonstrated by the study of 1 min hypoxia, which induced BOLD signal changes opposite to those under hyperoxia. Vasoconstriction was more common in voxels with negative BOLD contrast than in voxels with positive contrast (% change of blood volume, -9.8% to -12.8% versus 2.0% to 2.2%), which further suggests that negative BOLD contrast is mainly evoked by an increase in extravascular oxygen concentration. Conclusively, frequency shifts, which are induced by the accumulation of oxygen molecules and associated magnetic field inhomogeneity, are a significant source of the negative BOLD contrast during hyperoxia. Copyright © 2014 John Wiley & Sons, Ltd.

BOLD temporal dynamics of rat superior colliculus and lateral geniculate nucleus following short duration visual stimulation.

PubMed

Lau, Condon; Zhou, Iris Y; Cheung, Matthew M; Chan, Kevin C; Wu, Ed X

2011-04-29

The superior colliculus (SC) and lateral geniculate nucleus (LGN) are important subcortical structures for vision. Much of our understanding of vision was obtained using invasive and small field of view (FOV) techniques. In this study, we use non-invasive, large FOV blood oxygenation level-dependent (BOLD) fMRI to measure the SC and LGN's response temporal dynamics following short duration (1 s) visual stimulation. Experiments are performed at 7 tesla on Sprague Dawley rats stimulated in one eye with flashing light. Gradient-echo and spin-echo sequences are used to provide complementary information. An anatomical image is acquired from one rat after injection of monocrystalline iron oxide nanoparticles (MION), a blood vessel contrast agent. BOLD responses are concentrated in the contralateral SC and LGN. The SC BOLD signal measured with gradient-echo rises to 50% of maximum amplitude (PEAK) 0.2±0.2 s before the LGN signal (p<0.05). The LGN signal returns to 50% of PEAK 1.4±1.2 s before the SC signal (p<0.05). These results indicate the SC signal rises faster than the LGN signal but settles slower. Spin-echo results support these findings. The post-MION image shows the SC and LGN lie beneath large blood vessels. This subcortical vasculature is similar to that in the cortex, which also lies beneath large vessels. The LGN lies closer to the large vessels than much of the SC. The differences in response timing between SC and LGN are very similar to those between deep and shallow cortical layers following electrical stimulation, which are related to depth-dependent blood vessel dilation rates. This combined with the similarities in vasculature between subcortex and cortex suggest the SC and LGN timing differences are also related to depth-dependent dilation rates. This study shows for the first time that BOLD responses in the rat SC and LGN following short duration visual stimulation are temporally different.

High-resolution structural and functional assessments of cerebral microvasculature using 3D Gas ΔR2*-mMRA.

PubMed

Huang, Chien-Hsiang; Chen, Chiao-Chi V; Siow, Tiing-Yee; Hsu, Sheng-Hsiou S; Hsu, Yi-Hua; Jaw, Fu-Shan; Chang, Chen

2013-01-01

The ability to evaluate the cerebral microvascular structure and function is crucial for investigating pathological processes in brain disorders. Previous angiographic methods based on blood oxygen level-dependent (BOLD) contrast offer appropriate visualization of the cerebral vasculature, but these methods remain to be optimized in order to extract more comprehensive information. This study aimed to integrate the advantages of BOLD MRI in both structural and functional vascular assessments. The BOLD contrast was manipulated by a carbogen challenge, and signal changes in gradient-echo images were computed to generate ΔR2* maps. Simultaneously, a functional index representing the regional cerebral blood volume was derived by normalizing the ΔR2* values of a given region to those of vein-filled voxels of the sinus. This method is named 3D gas ΔR2*-mMRA (microscopic MRA). The advantages of using 3D gas ΔR2*-mMRA to observe the microvasculature include the ability to distinguish air-tissue interfaces, a high vessel-to-tissue contrast, and not being affected by damage to the blood-brain barrier. A stroke model was used to demonstrate the ability of 3D gas ΔR2*-mMRA to provide information about poststroke revascularization at 3 days after reperfusion. However, this technique has some limitations that cannot be overcome and hence should be considered when it is applied, such as magnifying vessel sizes and predominantly revealing venous vessels.

Portable non-invasive brain-computer interface: challenges and opportunities of optical modalities

NASA Astrophysics Data System (ADS)

Scholl, Clara A.; Hendrickson, Scott M.; Swett, Bruce A.; Fitch, Michael J.; Walter, Erich C.; McLoughlin, Michael P.; Chevillet, Mark A.; Blodgett, David W.; Hwang, Grace M.

2017-05-01

The development of portable non-invasive brain computer interface technologies with higher spatio-temporal resolution has been motivated by the tremendous success seen with implanted devices. This talk will discuss efforts to overcome several major obstacles to viability including approaches that promise to improve spatial and temporal resolution. Optical approaches in particular will be highlighted and the potential benefits of both Blood-Oxygen Level Dependent (BOLD) and Fast Optical Signal (FOS) will be discussed. Early-stage research into the correlations between neural activity and FOS will be explored.

The spatio-temporal mapping of epileptic networks: Combination of EEG–fMRI and EEG source imaging

PubMed Central

Vulliemoz, S.; Thornton, R.; Rodionov, R.; Carmichael, D.W.; Guye, M.; Lhatoo, S.; McEvoy, A.W.; Spinelli, L.; Michel, C.M.; Duncan, J.S.; Lemieux, L.

2009-01-01

Simultaneous EEG–fMRI acquisitions in patients with epilepsy often reveal distributed patterns of Blood Oxygen Level Dependant (BOLD) change correlated with epileptiform discharges. We investigated if electrical source imaging (ESI) performed on the interictal epileptiform discharges (IED) acquired during fMRI acquisition could be used to study the dynamics of the networks identified by the BOLD effect, thereby avoiding the limitations of combining results from separate recordings. Nine selected patients (13 IED types identified) with focal epilepsy underwent EEG–fMRI. Statistical analysis was performed using SPM5 to create BOLD maps. ESI was performed on the IED recorded during fMRI acquisition using a realistic head model (SMAC) and a distributed linear inverse solution (LAURA). ESI could not be performed in one case. In 10/12 remaining studies, ESI at IED onset (ESIo) was anatomically close to one BOLD cluster. Interestingly, ESIo was closest to the positive BOLD cluster with maximal statistical significance in only 4/12 cases and closest to negative BOLD responses in 4/12 cases. Very small BOLD clusters could also have clinical relevance in some cases. ESI at later time frame (ESIp) showed propagation to remote sources co-localised with other BOLD clusters in half of cases. In concordant cases, the distance between maxima of ESI and the closest EEG–fMRI cluster was less than 33 mm, in agreement with previous studies. We conclude that simultaneous ESI and EEG–fMRI analysis may be able to distinguish areas of BOLD response related to initiation of IED from propagation areas. This combination provides new opportunities for investigating epileptic networks. PMID:19408351

MRI measurement of the temporal evolution of relative CMRO(2) during rat forepaw stimulation.

PubMed

Mandeville, J B; Marota, J J; Ayata, C; Moskowitz, M A; Weisskoff, R M; Rosen, B R

1999-11-01

This study reports the first measurement of the relative cerebral metabolic rate of oxygen utilization (rCMRO(2)) during functional brain activation with sufficient temporal resolution to address the dynamics of blood oxygen level-dependent (BOLD) MRI signal. During rat forepaw stimulation, rCMRO(2) was determined in somatosensory cortex at 3-sec intervals, using a model of BOLD signal and measurements of the change in BOLD transverse relaxation rate, the resting state BOLD transverse relaxation rate, relative cerebral blood flow (rCBF), and relative cerebral blood volume (rCBV). Average percentage changes from 10 to 30 sec after onset of forepaw stimulation for rCBF, rCBV, rCMRO(2), and BOLD relaxation rate were 62 +/- 16, 17 +/- 2, 19 +/- 17, and -26 +/- 12, respectively. A poststimulus undershoot in BOLD signal was quantitatively attributed to the temporal mismatch between changes in blood flow and volume, and not to the role of oxygen metabolism. Magn Reson Med 42:944-951, 1999. Copyright 1999 Wiley-Liss, Inc.

Effect of Time on Gypsum-Impression Material Compatibility

NASA Astrophysics Data System (ADS)

Won, John Boram

The purpose of this study was to evaluate the compatibility of dental gypsum with three recently introduced irreversible hydrocolloid (alginate) alternatives. The test materials were Alginot® (Kerr™), Position Penta Quick® (3M ESPE™) and Silgimix ® (Sultan Dental™). The irreversible hydrocolloid impression material, Jeltrate Plus antimicrobial® (Dentsply Caulk™) served as the control. Materials and Methods: Testing of materials was conducted in accordance with ANSI/ADA Specification No. 18 for Alginate Impression Materials. Statistical Analysis: The 3-Way ANOVA test was used to analyze measurements between different time points at a significance level of (p < 0.05). Outcome: It was found that there was greater compatibility between gypsum and the alternative materials over time than the traditional irreversible hydrocolloid material that was tested. A statistically significant amount of surface change/incompatibility was found over time with the combination of the dental gypsum products and the control impression material (Jeltrate Plus antimicrobial®).

"Boldness" in the domestic dog differs among breeds and breed groups.

PubMed

Starling, Melissa J; Branson, Nicholas; Thomson, Peter C; McGreevy, Paul D

2013-07-01

"Boldness" in dogs is believed to be one end of the shy-bold axis, representing a super-trait. Several personality traits fall under the influence of this super-trait. Previous studies on boldness in dogs have found differences among breeds, but grouping breeds on the basis of behavioural similarities has been elusive. This study investigated differences in the expression of boldness among dog breeds, kennel club breed groups, and sub-groups of kennel club breed groups by way of a survey on dog personality circulated among Australian dog-training clubs and internet forums and lists. Breed had a significant effect on boldness (F=1.63, numDF=111, denDF=272, p<0.001), as did breed group (F=10.66, numDF=8, denDF=772, p<0.001). Herding and gundog groups were broken into sub-groups based on historic breed purpose. Retrievers were significantly bolder than flushing and pointing breeds (Reg. Coef.=2.148; S.E.=0.593; p<0.001), and tending and loose-eyed herding breeds were bolder than heading and cattle-herding breeds (Reg. Coef.=1.744; S.E.=0.866; p=0.045 and Reg. Coef.=1.842; S.E.=0.693; p=0.0084, respectively). This study supports the existence of the shy-bold continuum in dogs. Differences in boldness among groups and sub-groups suggest that behavioural tendencies may be influenced by historical purpose regardless of whether that purpose still factors in selective breeding. Copyright © 2013 Elsevier B.V. All rights reserved.

Cerebral Metabolic Rate of Oxygen (CMRO2 ) Mapping by Combining Quantitative Susceptibility Mapping (QSM) and Quantitative Blood Oxygenation Level-Dependent Imaging (qBOLD).

PubMed

Cho, Junghun; Kee, Youngwook; Spincemaille, Pascal; Nguyen, Thanh D; Zhang, Jingwei; Gupta, Ajay; Zhang, Shun; Wang, Yi

2018-03-07

To map the cerebral metabolic rate of oxygen (CMRO 2 ) by estimating the oxygen extraction fraction (OEF) from gradient echo imaging (GRE) using phase and magnitude of the GRE data. 3D multi-echo gradient echo imaging and perfusion imaging with arterial spin labeling were performed in 11 healthy subjects. CMRO 2 and OEF maps were reconstructed by joint quantitative susceptibility mapping (QSM) to process GRE phases and quantitative blood oxygen level-dependent (qBOLD) modeling to process GRE magnitudes. Comparisons with QSM and qBOLD alone were performed using ROI analysis, paired t-tests, and Bland-Altman plot. The average CMRO 2 value in cortical gray matter across subjects were 140.4 ± 14.9, 134.1 ± 12.5, and 184.6 ± 17.9 μmol/100 g/min, with corresponding OEFs of 30.9 ± 3.4%, 30.0 ± 1.8%, and 40.9 ± 2.4% for methods based on QSM, qBOLD, and QSM+qBOLD, respectively. QSM+qBOLD provided the highest CMRO 2 contrast between gray and white matter, more uniform OEF than QSM, and less noisy OEF than qBOLD. Quantitative CMRO 2 mapping that fits the entire complex GRE data is feasible by combining QSM analysis of phase and qBOLD analysis of magnitude. © 2018 International Society for Magnetic Resonance in Medicine.

Boldness and its relation to psychopathic personality: Prototypicality analyses among forensic mental health, criminal justice, and layperson raters.

PubMed

Sörman, Karolina; Edens, John F; Smith, Shannon Toney; Clark, John W; Kristiansson, Marianne; Svensson, Olof

2016-06-01

Research on psychopathic personality has been dominated by a focus on criminality and social deviance, but some theoretical models argue that certain putatively adaptive features are important components of this construct. In 3 samples (forensic mental health practitioners, probation officers and a layperson community sample), we investigated adaptive traits as conceptualized in the Triarchic model of psychopathy (Patrick et al., 2009), specifically the relevance of boldness to construals of psychopathic personality. Participants completed prototypicality ratings of psychopathic traits, including 3 items created to tap components of boldness (Socially bold, Adventurous, Emotionally stable), and they also rated a series of attitudinal statements (e.g., perceived correlates of being psychopathic, moral judgments about psychopaths). The composite Boldness scale was rated as moderately to highly prototypical among forensic mental health practitioners and probation officers and positively associated with other theoretically relevant domains of psychopathy. Across samples, higher composite Boldness ratings predicted greater endorsement of adaptive traits (e.g., social skills) as characteristic of psychopathy. For the individual items, Socially bold was rated as highly prototypical and was associated with theoretically relevant correlates. Adventurous also was seen as prototypical, though to a lesser degree. Only forensic mental health practitioners endorsed Emotionally stable as characteristic of psychopathy. Our results provide partial support for the contention that the boldness concept is viewed as an important component of psychopathy, particularly among professionals who work directly with offender populations. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Comparing cerebrovascular reactivity measured using BOLD and cerebral blood flow MRI: The effect of basal vascular tension on vasodilatory and vasoconstrictive reactivity

PubMed Central

Halani, Sheliza; Kwinta, Jonathan B.; Golestani, Ali M.; Khatamian, Yasha B.; Chen, J. Jean

2016-01-01

Cerebrovascular reactivity (CVR) is an important metric of cerebrovascular health. While the BOLD fMRI method in conjunction with carbon-dioxide (CO2) based vascular manipulation has been the most commonly used, the BOLD signal is not a direct measure of vascular changes, and the use of arterial-spin labeling (ASL) cerebral blood flow (CBF) imaging is increasingly advocated. Nonetheless, given the differing dependencies of BOLD and CBF on vascular baseline conditions and the diverse CO2 manipulation types currently used in the literature, knowledge of potential biases introduced by each technique is critical for the interpretation of CVR measurements. In this work, we use simultaneous BOLD-CBF acquisitions during both vasodilatory (hypercapnic) and vasoconstrictive (hypocapnic) stimuli to measure CVR. We further imposed different levels of baseline vascular tension by inducing hypercapnic and hypocapnic baselines, separately from normocapnia by 4 mm Hg. We saw significant and diverse dependencies on vascular stimulus and baseline condition in both BOLD and CBF CVR measurements: (i) BOLD-based CVR is more sensitive to basal vascular tension than CBF-based CVR; (ii) the use of a combination of vasodilatory and vasoconstrictive stimuli maximizes the sensitivity of CBF-based CVR to vascular tension changes; (iii) the BOLD and CBF vascular response delays are both significantly lengthened at predilated baseline. As vascular tension can often be altered by potential pathology, our findings are important considerations when interpreting CVR measurements in health and disease. PMID:25655446

Soil CO2 flux from three ecosystems in tropical peatland of Sarawak, Malaysia

NASA Astrophysics Data System (ADS)

Melling, Lulie; Hatano, Ryusuke; Goh, Kah Joo

2005-02-01

Soil CO2 flux was measured monthly over a year from tropical peatland of Sarawak, Malaysia using a closed-chamber technique. The soil CO2 flux ranged from 100 to 533 mg C m2 h1 for the forest ecosystem, 63 to 245 mg C m2 h1 for the sago and 46 to 335 mg C m2 h1 for the oil palm. Based on principal component analysis (PCA), the environmental variables over all sites could be classified into three components, namely, climate, soil moisture and soil bulk density, which accounted for 86% of the seasonal variability. A regression tree approach showed that CO2 flux in each ecosystem was related to different underlying environmental factors. They were relative humidity for forest, soil temperature at 5 cm for sago and water-filled pore space for oil palm. On an annual basis, the soil CO2 flux was highest in the forest ecosystem with an estimated production of 2.1 kg C m2 yr1 followed by oil palm at 1.5 kg C m2 yr1 and sago at 1.1 kg C m2 yr1. The different dominant controlling factors in CO2 flux among the studied ecosystems suggested that land use affected the exchange of CO2 between tropical peatland and the atmosphere.

Information Technology for the Twenty-First Century: A Bold Investment in America's Future

NASA Astrophysics Data System (ADS)

1999-06-01

With this Information Technology for the Twenty First Century (IT2) initiative, the Federal Government is making an important re-commitment to fundamental research in information technology. The IT2 initiative proposes 366 million in increased investments in computing, information, and communications research and development (R&D) to help expand the knowledge base in fundamental information science, advance the Nations capabilities in cutting edge research, and train the next generation of researchers who will sustain the Information Revolution well into the 21st Century.

Automaticity and localisation of concurrents predicts colour area activity in grapheme-colour synaesthesia.

PubMed

Gould van Praag, Cassandra D; Garfinkel, Sarah; Ward, Jamie; Bor, Daniel; Seth, Anil K

2016-07-29

In grapheme-colour synaesthesia (GCS), the presentation of letters or numbers induces an additional 'concurrent' experience of colour. Early functional MRI (fMRI) investigations of GCS reported activation in colour-selective area V4 during the concurrent experience. However, others have failed to replicate this key finding. We reasoned that individual differences in synaesthetic phenomenology might explain this inconsistency in the literature. To test this hypothesis, we examined fMRI BOLD responses in a group of grapheme-colour synaesthetes (n=20) and matched controls (n=20) while characterising the individual phenomenology of the synaesthetes along dimensions of 'automaticity' and 'localisation'. We used an independent functional localiser to identify colour-selective areas in both groups. Activations in these areas were then assessed during achromatic synaesthesia-inducing, and non-inducing conditions; we also explored whole brain activations, where we sought to replicate the existing literature regarding synaesthesia effects. Controls showed no significant activations in the contrast of inducing > non-inducing synaesthetic stimuli, in colour-selective ROIs or at the whole brain level. In the synaesthete group, we correlated activation within colour-selective ROIs with individual differences in phenomenology using the Coloured Letters and Numbers (CLaN) questionnaire which measures, amongst other attributes, the subjective automaticity/attention in synaesthetic concurrents, and their spatial localisation. Supporting our hypothesis, we found significant correlations between individual measures of synaesthetic phenomenology and BOLD responses in colour-selective areas, when contrasting inducing against non-inducing stimuli. Specifically, left-hemisphere colour area responses were stronger for synaesthetes scoring high on phenomenological localisation and automaticity/attention, while right-hemisphere colour area responses showed a relationship with localisation only. In exploratory whole brain analyses, the BOLD response within several other areas was also correlated with these phenomenological factors, including the intra-parietal sulcus, insula, precentral and supplementary motor areas. Our findings reveal a network of regions underlying synaesthetic phenomenology and they help reconcile the diversity of previous results regarding colour-selective BOLD responses during synaesthesia, by establishing a bridge between neural responses and individual synaesthetic phenomenology. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

WE-FG-BRA-08: Potential Role of the Glycolytic Oscillator in Acute Hypoxia in Tumors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Che Fru, L; Adamson, E; Campos, D

2016-06-15

Purpose: Oscillatory dynamics in acute hypoxia have been observed, but poorly understood. They have mostly been attributed to vascular perturbations, but no link has yet been made to metabolic causes. We set out to determine the fundamental frequencies and test for coherence in tumor oxygen dynamics and spatial properties. Methods: Severe combined immunodeficient (SCID) mice were inoculated onto bilateral flanks with human derived head and neck carcinoma (UW-SCC22) cell line xenografts. Oxygen dynamics were monitored in the tumor every minute for an hour using three modalities: blood oxygen level dependent - magnetic resonance imaging (BOLD-MRI), hemoglobin oxygen saturation photoacoustic, andmore » locally manufactured optical probes for spectral fitting. A statistical test was used to separate fluctuating from non-fluctuating voxels and pixels in BOLD-MRI and photoacoustic data respectively. The power spectrum density (PSD) and the autocorrelation functions were calculated for the time series of each voxel, pixel and region, of the BOLD-MRI, photoacoustic or fiber optic data respectively. Results: Using all three techniques, intermittent oxygen dynamics with both coherent and incoherent signatures was observed in the tumors. Upon averaging the PSDs of fluctuating voxels and pixels, it was found that these oscillations occurred with periods of minutes to tens of minutes from all three approaches. Observations from the BOLD-MRI and photoacoustic data showed that clusters of voxels oscillated in a synchronized manner. Conclusion: We were able to use three different modalities to show that fluctuation in tumor oxygen is both coherent and incoherent, with periods of minutes to tens of minutes. These periods are very similar to those from the well-established metabolic, non-linear biomechanical phenomenon called the glycolytic oscillator. This may provide an additional explanation to the cause of cyclic hypoxia. Such dynamics could have profound implications in hypofractionated radiotherapy regiments and could help guide treatment and make it more patient specific. The authors would like to thank the University of Wisconsin Carbone Cancer Center (UWCCC) for the funds to complete this project. This work is also supported in part by NIH/NCI P30 CA014520- UW Comprehensive Cancer Center Support”.« less

49 CFR 375.213 - What information must I provide to a prospective individual shipper?

Code of Federal Regulations, 2010 CFR

2010-10-01

... type font size is 10 points or larger and the size of the booklet is at least as large as 36 square... cover in 12-point or larger bold or full-faced type: “Your Rights and Responsibilities When You Move...

Repeatability and consistency of individual behaviour in juvenile and adult Eurasian harvest mice

NASA Astrophysics Data System (ADS)

Schuster, Andrea C.; Carl, Teresa; Foerster, Katharina

2017-04-01

Knowledge on animal personality has provided new insights into evolutionary biology and animal ecology, as behavioural types have been shown to affect fitness. Animal personality is characterized by repeatable and consistent between-individual behavioural differences throughout time and across different situations. Behavioural repeatability within life history stages and consistency between life history stages should be checked for the independence of sex and age, as recent data have shown that males and females in some species may differ in the repeatability of behavioural traits, as well as in their consistency. We measured the repeatability and consistency of three behavioural and one cognitive traits in juvenile and adult Eurasian harvest mice ( Micromys minutus). We found that exploration, activity and boldness were repeatable in juveniles and adults. Spatial recognition measured in a Y Maze was only repeatable in adult mice. Exploration, activity and boldness were consistent before and after maturation, as well as before and after first sexual contact. Data on spatial recognition provided little evidence for consistency. Further, we found some evidence for a litter effect on behaviours by comparing different linear mixed models. We concluded that harvest mice express animal personality traits as behaviours were repeatable across sexes and consistent across life history stages. The tested cognitive trait showed low repeatability and was less consistent across life history stages. Given the rising interest in individual variation in cognitive performance, and in its relationship to animal personality, we suggest that it is important to gather more data on the repeatability and consistency of cognitive traits.

Urbanisation shapes behavioural responses to a pesticide.

PubMed

Tüzün, Nedim; Debecker, Sara; Op de Beeck, Lin; Stoks, Robby

2015-06-01

The degree of urbanisation is rapidly increasing worldwide. Due to anthropogenic impact, urban populations are exposed to higher levels of contaminants and higher temperatures. Despite this, urbanisation is a largely overlooked spatial component in ecotoxicology. We tested in a common garden rearing experiment whether replicated urban and rural populations of the damselfly Coenagrion puella differ in their vulnerability to sublethal levels of a widespread pesticide, chlorpyrifos, in terms of ecologically relevant behaviours (exploration behaviour, activity, boldness and food intake), and to what extent these patterns are affected by temperature (20 and 24°C). Except boldness, all behaviours were affected by previous pesticide exposure. While the pesticide did not affect exploration behaviour at 20°C, it was associated with increased exploration at 24°C, which may reflect an increased toxicity of chlorpyrifos at higher temperatures. Importantly, rural and urban larvae showed consistently different, sometimes even opposite behavioural responses to pesticide exposure. When exposed to the pesticide, rural larvae decreased activity and food intake at both temperatures; urban larvae instead increased activity at both temperatures and only reduced food intake at the high temperature. This suggests that urban larvae were less affected by the pesticide, which would be consistent with a scenario of local adaptation to higher contaminant levels. Our results highlight that urbanisation may be an important factor to arrive at a spatially explicit ecological risk assessment, and may be an ignored reason why studies on the same species may generate widely different vulnerabilities to pesticides. Copyright © 2015 Elsevier B.V. All rights reserved.

Neural correlates of decision making with explicit information about probabilities and incentives in elderly healthy subjects.

PubMed

Labudda, Kirsten; Woermann, Friedrich G; Mertens, Markus; Pohlmann-Eden, Bernd; Markowitsch, Hans J; Brand, Matthias

2008-06-01

Recent functional neuroimaging and lesion studies demonstrate the involvement of the orbitofrontal/ventromedial prefrontal cortex as a key structure in decision making processes. This region seems to be particularly crucial when contingencies between options and consequences are unknown but have to be learned by the use of feedback following previous decisions (decision making under ambiguity). However, little is known about the neural correlates of decision making under risk conditions in which information about probabilities and potential outcomes is given. In the present study, we used functional magnetic resonance imaging to measure blood-oxygenation-level-dependent (BOLD) responses in 12 subjects during a decision making task. This task provided explicit information about probabilities and associated potential incentives. The responses were compared to BOLD signals in a control condition without information about incentives. In contrast to previous decision making studies, we completely removed the outcome phase following a decision to exclude the potential influence of feedback previously received on current decisions. The results indicate that the integration of information about probabilities and incentives leads to activations within the dorsolateral prefrontal cortex, the posterior parietal lobe, the anterior cingulate and the right lingual gyrus. We assume that this pattern of activation is due to the involvement of executive functions, conflict detection mechanisms and arithmetic operations during the deliberation phase of decisional processes that are based on explicit information.

Primary hepatocytes as an useful bioassay to characterize metabolism and bioactivity of illicit steroids in cattle.

PubMed

Giantin, Mery; Gallina, Guglielmo; Pegolo, Sara; Lopparelli, Rosa Maria; Sandron, Clara; Zancanella, Vanessa; Nebbia, Carlo; Favretto, Donata; Capolongo, Francesca; Montesissa, Clara; Dacasto, Mauro

2012-10-01

Cattle hepatocytes have already been used in veterinary in vitro toxicology, but their usefulness as a multi-parametric screening bioassay has never been investigated so far. In this study, cattle hepatocytes were incubated with illicit steroids/prohormones (boldenone, BOLD; its precursor boldione, ADD; dehydroepiandrosterone, DHEA; an association of ADD:BOLD), to characterize their transcriptional effects on drug metabolizing enzymes (DMEs) and related nuclear receptors (NRs), on cytochrome P450 3A (CYP3A) apoprotein and catalytic activity as well as to determine ADD and BOLD metabolite profiling. DHEA-exposed cells showed an up-regulation (higher than 2.5-fold changes) of three out of six NRs, CYP2B22 and CYP2C87; likewise, ADD:BOLD increased CYP4A11 mRNA levels. In contrast, a reduction of CYP1A1 and CYP2E1 mRNAs (lower than 2.5(-1)-fold changes) was noticed in ADD- and DHEA-incubated cells. No effect was noticed on CYP3A gene and protein expression, though an inhibition of 6β-, 2β- and 16β-hydroxylation of testosterone (higher than 60% of control cells) was observed in ADD- and BOLD-exposed cells. Finally, 17α-BOLD was the main metabolite extracted from hepatocyte media incubated with ADD and BOLD, but several mono-hydroxylated BOLD and ADD derivatives were detected, too. Collectively, cattle hepatocytes can represent a complementary screening bioassay, useful to characterize growth promoters metabolite profiling and their effects upon DMEs expression, regulation and function. Copyright © 2012 Elsevier Ltd. All rights reserved.

Negative blood oxygen level dependent signals during speech comprehension.

PubMed

Rodriguez Moreno, Diana; Schiff, Nicholas D; Hirsch, Joy

2015-05-01

Speech comprehension studies have generally focused on the isolation and function of regions with positive blood oxygen level dependent (BOLD) signals with respect to a resting baseline. Although regions with negative BOLD signals in comparison to a resting baseline have been reported in language-related tasks, their relationship to regions of positive signals is not fully appreciated. Based on the emerging notion that the negative signals may represent an active function in language tasks, the authors test the hypothesis that negative BOLD signals during receptive language are more associated with comprehension than content-free versions of the same stimuli. Regions associated with comprehension of speech were isolated by comparing responses to passive listening to natural speech to two incomprehensible versions of the same speech: one that was digitally time reversed and one that was muffled by removal of high frequencies. The signal polarity was determined by comparing the BOLD signal during each speech condition to the BOLD signal during a resting baseline. As expected, stimulation-induced positive signals relative to resting baseline were observed in the canonical language areas with varying signal amplitudes for each condition. Negative BOLD responses relative to resting baseline were observed primarily in frontoparietal regions and were specific to the natural speech condition. However, the BOLD signal remained indistinguishable from baseline for the unintelligible speech conditions. Variations in connectivity between brain regions with positive and negative signals were also specifically related to the comprehension of natural speech. These observations of anticorrelated signals related to speech comprehension are consistent with emerging models of cooperative roles represented by BOLD signals of opposite polarity.

Decreased resting-state brain activity complexity in schizophrenia characterized by both increased regularity and randomness.

PubMed

Yang, Albert C; Hong, Chen-Jee; Liou, Yin-Jay; Huang, Kai-Lin; Huang, Chu-Chung; Liu, Mu-En; Lo, Men-Tzung; Huang, Norden E; Peng, Chung-Kang; Lin, Ching-Po; Tsai, Shih-Jen

2015-06-01

Schizophrenia is characterized by heterogeneous pathophysiology. Using multiscale entropy (MSE) analysis, which enables capturing complex dynamics of time series, we characterized MSE patterns of blood-oxygen-level-dependent (BOLD) signals across different time scales and determined whether BOLD activity in patients with schizophrenia exhibits increased complexity (increased entropy in all time scales), decreased complexity toward regularity (decreased entropy in all time scales), or decreased complexity toward uncorrelated randomness (high entropy in short time scales followed by decayed entropy as the time scale increases). We recruited 105 patients with schizophrenia with an age of onset between 18 and 35 years and 210 age- and sex-matched healthy volunteers. Results showed that MSE of BOLD signals in patients with schizophrenia exhibited two routes of decreased BOLD complexity toward either regular or random patterns. Reduced BOLD complexity toward regular patterns was observed in the cerebellum and temporal, middle, and superior frontal regions, and reduced BOLD complexity toward randomness was observed extensively in the inferior frontal, occipital, and postcentral cortices as well as in the insula and middle cingulum. Furthermore, we determined that the two types of complexity change were associated differently with psychopathology; specifically, the regular type of BOLD complexity change was associated with positive symptoms of schizophrenia, whereas the randomness type of BOLD complexity was associated with negative symptoms of the illness. These results collectively suggested that resting-state dynamics in schizophrenia exhibit two routes of pathologic change toward regular or random patterns, which contribute to the differences in syndrome domains of psychosis in patients with schizophrenia. © 2015 Wiley Periodicals, Inc.

Negative Blood Oxygen Level Dependent Signals During Speech Comprehension

PubMed Central

Rodriguez Moreno, Diana; Schiff, Nicholas D.

2015-01-01

Abstract Speech comprehension studies have generally focused on the isolation and function of regions with positive blood oxygen level dependent (BOLD) signals with respect to a resting baseline. Although regions with negative BOLD signals in comparison to a resting baseline have been reported in language-related tasks, their relationship to regions of positive signals is not fully appreciated. Based on the emerging notion that the negative signals may represent an active function in language tasks, the authors test the hypothesis that negative BOLD signals during receptive language are more associated with comprehension than content-free versions of the same stimuli. Regions associated with comprehension of speech were isolated by comparing responses to passive listening to natural speech to two incomprehensible versions of the same speech: one that was digitally time reversed and one that was muffled by removal of high frequencies. The signal polarity was determined by comparing the BOLD signal during each speech condition to the BOLD signal during a resting baseline. As expected, stimulation-induced positive signals relative to resting baseline were observed in the canonical language areas with varying signal amplitudes for each condition. Negative BOLD responses relative to resting baseline were observed primarily in frontoparietal regions and were specific to the natural speech condition. However, the BOLD signal remained indistinguishable from baseline for the unintelligible speech conditions. Variations in connectivity between brain regions with positive and negative signals were also specifically related to the comprehension of natural speech. These observations of anticorrelated signals related to speech comprehension are consistent with emerging models of cooperative roles represented by BOLD signals of opposite polarity. PMID:25412406

"Extreme Bold" in the Faculty Ranks

ERIC Educational Resources Information Center

Kuusisto, Stephen

2013-01-01

Boldness, defense, and the necessity of talking back remain as central to life with disability in one's time as in Francis Bacon's age. "Therefore all deformed persons are extreme bold," Bacon wrote, "first, as in their own defence, as being exposed to scorn, but in process of time, by a general habit." Perhaps no word carries…

Correlating brain blood oxygenation level dependent (BOLD) fractal dimension mapping with magnetic resonance spectroscopy (MRS) in Alzheimer's disease.

PubMed

Warsi, Mohammed A; Molloy, William; Noseworthy, Michael D

2012-10-01

To correlate temporal fractal structure of resting state blood oxygen level dependent (rsBOLD) functional magnetic resonance imaging (fMRI) with in vivo proton magnetic resonance spectroscopy ((1)H-MRS), in Alzheimer's disease (AD) and healthy age-matched normal controls (NC). High temporal resolution (4 Hz) rsBOLD signal and single voxel (left putamen) magnetic resonance spectroscopy data was acquired in 33 AD patients and 13 NC. The rsBOLD data was analyzed using two types of fractal dimension (FD) analysis based on relative dispersion and frequency power spectrum. Comparisons in FD were performed between AD and NC, and FD measures were correlated with (1)H-MRS findings. Temporal fractal analysis of rsBOLD, was able to differentiate AD from NC subjects (P = 0.03). Low FD correlated with markers of AD severity including decreased concentrations of N-acetyl aspartate (R = 0.44, P = 0.015) and increased myoinositol (mI) (R = -0.45, P = 0.012). Based on these results we suggest fractal analysis of rsBOLD could provide an early marker of AD.

Mechanisms of migraine aura revealed by functional MRI in human visual cortex

PubMed Central

Hadjikhani, Nouchine; Sanchez del Rio, Margarita; Wu, Ona; Schwartz, Denis; Bakker, Dick; Fischl, Bruce; Kwong, Kenneth K.; Cutrer, F. Michael; Rosen, Bruce R.; Tootell, Roger B. H.; Sorensen, A. Gregory; Moskowitz, Michael A.

2001-01-01

Cortical spreading depression (CSD) has been suggested to underlie migraine visual aura. However, it has been challenging to test this hypothesis in human cerebral cortex. Using high-field functional MRI with near-continuous recording during visual aura in three subjects, we observed blood oxygenation level-dependent (BOLD) signal changes that demonstrated at least eight characteristics of CSD, time-locked to percept/onset of the aura. Initially, a focal increase in BOLD signal (possibly reflecting vasodilation), developed within extrastriate cortex (area V3A). This BOLD change progressed contiguously and slowly (3.5 ± 1.1 mm/min) over occipital cortex, congruent with the retinotopy of the visual percept. Following the same retinotopic progression, the BOLD signal then diminished (possibly reflecting vasoconstriction after the initial vasodilation), as did the BOLD response to visual activation. During periods with no visual stimulation, but while the subject was experiencing scintillations, BOLD signal followed the retinotopic progression of the visual percept. These data strongly suggest that an electrophysiological event such as CSD generates the aura in human visual cortex. PMID:11287655

Caffeine Increases the Linearity of the Visual BOLD Response

PubMed Central

Liu, Thomas T.; Liau, Joy

2009-01-01

Although the blood oxygenation level dependent (BOLD) signal used in most functional magnetic resonance imaging (fMRI) studies has been shown to exhibit nonlinear characteristics, most analyses assume that the BOLD signal responds in a linear fashion to stimulus. This assumption of linearity can lead to errors in the estimation of the BOLD response, especially for rapid event-related fMRI studies. In this study, we used a rapid event-related design and Volterra kernel analysis to assess the effect of a 200 mg oral dose of caffeine on the linearity of the visual BOLD response. The caffeine dose significantly (p < 0.02) increased the linearity of the BOLD response in a sample of 11 healthy volunteers studied on a 3 Tesla MRI system. In addition, the agreement between nonlinear and linear estimates of the hemodynamic response function was significantly increased (p= 0.013) with the caffeine dose. These findings indicate that differences in caffeine usage should be considered as a potential source of bias in the analysis of rapid event-related fMRI studies. PMID:19854278

Edge-Related Activity Is Not Necessary to Explain Orientation Decoding in Human Visual Cortex.

PubMed

Wardle, Susan G; Ritchie, J Brendan; Seymour, Kiley; Carlson, Thomas A

2017-02-01

Multivariate pattern analysis is a powerful technique; however, a significant theoretical limitation in neuroscience is the ambiguity in interpreting the source of decodable information used by classifiers. This is exemplified by the continued controversy over the source of orientation decoding from fMRI responses in human V1. Recently Carlson (2014) identified a potential source of decodable information by modeling voxel responses based on the Hubel and Wiesel (1972) ice-cube model of visual cortex. The model revealed that activity associated with the edges of gratings covaries with orientation and could potentially be used to discriminate orientation. Here we empirically evaluate whether "edge-related activity" underlies orientation decoding from patterns of BOLD response in human V1. First, we systematically mapped classifier performance as a function of stimulus location using population receptive field modeling to isolate each voxel's overlap with a large annular grating stimulus. Orientation was decodable across the stimulus; however, peak decoding performance occurred for voxels with receptive fields closer to the fovea and overlapping with the inner edge. Critically, we did not observe the expected second peak in decoding performance at the outer stimulus edge as predicted by the edge account. Second, we evaluated whether voxels that contribute most to classifier performance have receptive fields that cluster in cortical regions corresponding to the retinotopic location of the stimulus edge. Instead, we find the distribution of highly weighted voxels to be approximately random, with a modest bias toward more foveal voxels. Our results demonstrate that edge-related activity is likely not necessary for orientation decoding. A significant theoretical limitation of multivariate pattern analysis in neuroscience is the ambiguity in interpreting the source of decodable information used by classifiers. For example, orientation can be decoded from BOLD activation patterns in human V1, even though orientation columns are at a finer spatial scale than 3T fMRI. Consequently, the source of decodable information remains controversial. Here we test the proposal that information related to the stimulus edges underlies orientation decoding. We map voxel population receptive fields in V1 and evaluate orientation decoding performance as a function of stimulus location in retinotopic cortex. We find orientation is decodable from voxels whose receptive fields do not overlap with the stimulus edges, suggesting edge-related activity does not substantially drive orientation decoding. Copyright © 2017 the authors 0270-6474/17/371187-10$15.00/0.

A method for independent component graph analysis of resting-state fMRI.

PubMed

Ribeiro de Paula, Demetrius; Ziegler, Erik; Abeyasinghe, Pubuditha M; Das, Tushar K; Cavaliere, Carlo; Aiello, Marco; Heine, Lizette; di Perri, Carol; Demertzi, Athena; Noirhomme, Quentin; Charland-Verville, Vanessa; Vanhaudenhuyse, Audrey; Stender, Johan; Gomez, Francisco; Tshibanda, Jean-Flory L; Laureys, Steven; Owen, Adrian M; Soddu, Andrea

2017-03-01

Independent component analysis (ICA) has been extensively used for reducing task-free BOLD fMRI recordings into spatial maps and their associated time-courses. The spatially identified independent components can be considered as intrinsic connectivity networks (ICNs) of non-contiguous regions. To date, the spatial patterns of the networks have been analyzed with techniques developed for volumetric data. Here, we detail a graph building technique that allows these ICNs to be analyzed with graph theory. First, ICA was performed at the single-subject level in 15 healthy volunteers using a 3T MRI scanner. The identification of nine networks was performed by a multiple-template matching procedure and a subsequent component classification based on the network "neuronal" properties. Second, for each of the identified networks, the nodes were defined as 1,015 anatomically parcellated regions. Third, between-node functional connectivity was established by building edge weights for each networks. Group-level graph analysis was finally performed for each network and compared to the classical network. Network graph comparison between the classically constructed network and the nine networks showed significant differences in the auditory and visual medial networks with regard to the average degree and the number of edges, while the visual lateral network showed a significant difference in the small-worldness. This novel approach permits us to take advantage of the well-recognized power of ICA in BOLD signal decomposition and, at the same time, to make use of well-established graph measures to evaluate connectivity differences. Moreover, by providing a graph for each separate network, it can offer the possibility to extract graph measures in a specific way for each network. This increased specificity could be relevant for studying pathological brain activity or altered states of consciousness as induced by anesthesia or sleep, where specific networks are known to be altered in different strength.

Contributions of dopaminergic and non-dopaminergic neurons to VTA-stimulation induced neurovascular responses in brain reward circuits.

PubMed

Brocka, Marta; Helbing, Cornelia; Vincenz, Daniel; Scherf, Thomas; Montag, Dirk; Goldschmidt, Jürgen; Angenstein, Frank; Lippert, Michael

2018-04-30

Mapping the activity of the human mesolimbic dopamine system by BOLD-fMRI is a tempting approach to non-invasively study the action of the brain reward system during different experimental conditions. However, the contribution of dopamine release to the BOLD signal is disputed. To assign the actual contribution of dopaminergic and non-dopaminergic VTA neurons to the formation of BOLD responses in target regions of the mesolimbic system, we used two optogenetic approaches in rats. We either activated VTA dopaminergic neurons selectively, or dopaminergic and mainly glutamatergic projecting neurons together. We further used electrical stimulation to non-selectively activate neurons in the VTA. All three stimulation conditions effectively activated the mesolimbic dopaminergic system and triggered dopamine releases into the NAcc as measured by in vivo fast-scan cyclic voltammetry. Furthermore, both optogenetic stimulation paradigms led to indistinguishable self-stimulation behavior. In contrast to these similarities, however, the BOLD response pattern differed greatly between groups. In general, BOLD responses were weaker and sparser with increasing stimulation specificity for dopaminergic neurons. In addition, repetitive stimulation of the VTA caused a progressive decoupling of dopamine release and BOLD signal strength, and dopamine receptor antagonists were unable to block the BOLD signal elicited by VTA stimulation. To exclude that the sedation during fMRI is the cause of minimal mesolimbic BOLD in response to specific dopaminergic stimulation, we repeated our experiments using CBF SPECT in awake animals. Again, we found activations only for less-specific stimulation. Based on these results we conclude that canonical BOLD responses in the reward system represent mainly the activity of non-dopaminergic neurons. Thus, the minor effects of projecting dopaminergic neurons are concealed by non-dopaminergic activity, a finding which highlights the importance of a careful interpretation of reward-related human fMRI data. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Size doesn't matter, sex does: a test for boldness in sister species of Brachyrhaphis fishes.

PubMed

Ingley, Spencer J; Rehm, Jeremy; Johnson, Jerald B

2014-11-01

The effect of divergent natural selection on the evolution of behavioral traits has long been a focus of behavioral ecologists. Predation, due to its ubiquity in nature and strength as a selective agent, has been considered an important environmental driver of behavior. Predation is often confounded with other environmental factors that could also play a role in behavioral evolution. For example, environments that contain predators are often more ecologically complex and "risky" (i.e., exposed and dangerous). Previous work shows that individuals from risky environments are often more bold, active, and explorative than those from low-risk environments. To date, most comparative studies of environmentally driven behavioral divergence are limited to comparisons among populations within species that occur in divergent selective environments but neglect comparisons between species following speciation. This limits our understanding of how behavior evolves post-speciation. The Central American live-bearing fish genus Brachyrhaphis provides an ideal system for examining the relationship between selective environments and behavior, within and between species. Here, we test for differences in boldness between sister species B. roseni and B. terrabensis that occur in streams with and without piscivorous predators, respectively. We found that species do differ in boldness, with species that occur with predators being bolder than those that do not. Within each species, we found that sexes differed in boldness, with males being bolder than females. We also tested for a relationship between size (a surrogate for metabolic rate) and boldness, but found no size effects. Therefore, sex, not size, affects boldness. These results are consistent with the hypothesis that complex and risky environments favor individuals with more bold behavioral traits, but they are not consistent with the hypothesis that size (and therefore metabolic rate) drives divergence in boldness. Finally, our results provide evidence that behavioral trait divergence continues even after speciation is complete.

Size doesn't matter, sex does: a test for boldness in sister species of Brachyrhaphis fishes

PubMed Central

Ingley, Spencer J; Rehm, Jeremy; Johnson, Jerald B

2014-01-01

The effect of divergent natural selection on the evolution of behavioral traits has long been a focus of behavioral ecologists. Predation, due to its ubiquity in nature and strength as a selective agent, has been considered an important environmental driver of behavior. Predation is often confounded with other environmental factors that could also play a role in behavioral evolution. For example, environments that contain predators are often more ecologically complex and “risky” (i.e., exposed and dangerous). Previous work shows that individuals from risky environments are often more bold, active, and explorative than those from low-risk environments. To date, most comparative studies of environmentally driven behavioral divergence are limited to comparisons among populations within species that occur in divergent selective environments but neglect comparisons between species following speciation. This limits our understanding of how behavior evolves post-speciation. The Central American live-bearing fish genus Brachyrhaphis provides an ideal system for examining the relationship between selective environments and behavior, within and between species. Here, we test for differences in boldness between sister species B. roseni and B. terrabensis that occur in streams with and without piscivorous predators, respectively. We found that species do differ in boldness, with species that occur with predators being bolder than those that do not. Within each species, we found that sexes differed in boldness, with males being bolder than females. We also tested for a relationship between size (a surrogate for metabolic rate) and boldness, but found no size effects. Therefore, sex, not size, affects boldness. These results are consistent with the hypothesis that complex and risky environments favor individuals with more bold behavioral traits, but they are not consistent with the hypothesis that size (and therefore metabolic rate) drives divergence in boldness. Finally, our results provide evidence that behavioral trait divergence continues even after speciation is complete. PMID:25540696

Effect of sound intensity on tonotopic fMRI maps in the unanesthetized monkey.

PubMed

Tanji, Kazuyo; Leopold, David A; Ye, Frank Q; Zhu, Charles; Malloy, Megan; Saunders, Richard C; Mishkin, Mortimer

2010-01-01

The monkey's auditory cortex includes a core region on the supratemporal plane (STP) made up of the tonotopically organized areas A1, R, and RT, together with a surrounding belt and a lateral parabelt region. The functional studies that yielded the tonotopic maps and corroborated the anatomical division into core, belt, and parabelt typically used low-amplitude pure tones that were often restricted to threshold-level intensities. Here we used functional magnetic resonance imaging in awake rhesus monkeys to determine whether, and if so how, the tonotopic maps and the pattern of activation in core, belt, and parabelt are affected by systematic changes in sound intensity. Blood oxygenation level-dependent (BOLD) responses to groups of low- and high-frequency pure tones 3-4 octaves apart were measured at multiple sound intensity levels. The results revealed tonotopic maps in the auditory core that reversed at the putative areal boundaries between A1 and R and between R and RT. Although these reversals of the tonotopic representations were present at all intensity levels, the lateral spread of activation depended on sound amplitude, with increasing recruitment of the adjacent belt areas as the intensities increased. Tonotopic organization along the STP was also evident in frequency-specific deactivation (i.e. "negative BOLD"), an effect that was intensity-specific as well. Regions of positive and negative BOLD were spatially interleaved, possibly reflecting lateral inhibition of high-frequency areas during activation of adjacent low-frequency areas, and vice versa. These results, which demonstrate the strong influence of tonal amplitude on activation levels, identify sound intensity as an important adjunct parameter for mapping the functional architecture of auditory cortex.

MDMA (Ecstasy) association with impaired fMRI BOLD thalamic coherence and functional connectivity*

PubMed Central

Salomon, Ronald M.; Karageorgiou, John; Dietrich, Mary S.; McLellan, Jessica Y.; Charboneau, Evonne J.; Blackford, Jennifer U.; Cowan, Ronald L.

2011-01-01

Background MDMA exposure is associated with chronic serotonergic dysfunction in preclinical and clinical studies. A recent functional magnetic resonance imaging (fMRI) comparison of past MDMA users to non-MDMA-using controls revealed increased spatial extent and amplitude of activation in the supplementary motor area during motor tasks (Karageorgiou et al., 2009). Blood oxygenation level dependent (BOLD) data from that study were reanalyzed for intraregional coherence and for inter-regional temporal correlations between time series, as functional connectivity. Methods Fourteen MDMA users and ten controls reporting similar non-MDMA abuse performed finger taps during fMRI. Fourteen motor pathway regions plus a pontine raphé region were examined. Coherence was expressed as percent of voxels positively correlated with an intraregional index voxel. Functional connectivity was determined using wavelet correlations. Results Intraregional thalamic coherence was significantly diminished at low frequencies in MDMA users compared to controls (p=0.009). Inter-regional functional connectivity was significantly weaker for right thalamo - left caudate (p=0.002), right thalamo - left thalamus (p=0.007), right caudate - right postcentral (p=0.007) and right supplementary motor area - right precentral gyrus (p=0.011) region pairs compared to controls. When stratified by lifetime exposure, significant negative associations were observed between cumulative MDMA use and functional connectivity in seven other region-pairs, while only one region-pair showed a positive association. Conclusions Reported prior MDMA use was associated with deficits in BOLD intraregional coherence and inter-regional functional connectivity, even among functionally robust pathways involving motor regions. This suggests that MDMA use is associated with long-lasting effects on brain neurophysiology beyond the cognitive domain. PMID:21807471

Multimodal imaging of repetition priming: Using fMRI, MEG, and intracranial EEG to reveal spatiotemporal profiles of word processing.

PubMed

McDonald, Carrie R; Thesen, Thomas; Carlson, Chad; Blumberg, Mark; Girard, Holly M; Trongnetrpunya, Amy; Sherfey, Jason S; Devinsky, Orrin; Kuzniecky, Rubin; Dolye, Werner K; Cash, Sydney S; Leonard, Matthew K; Hagler, Donald J; Dale, Anders M; Halgren, Eric

2010-11-01

Repetition priming is a core feature of memory processing whose anatomical correlates remain poorly understood. In this study, we use advanced multimodal imaging (functional magnetic resonance imaging (fMRI) and magnetoencephalography; MEG) to investigate the spatiotemporal profile of repetition priming. We use intracranial electroencephalography (iEEG) to validate our fMRI/MEG measurements. Twelve controls completed a semantic judgment task with fMRI and MEG that included words presented once (new, 'N') and words that repeated (old, 'O'). Six patients with epilepsy completed the same task during iEEG recordings. Blood-oxygen level dependent (BOLD) responses for N vs. O words were examined across the cortical surface and within regions of interest. MEG waveforms for N vs. O words were estimated using a noise-normalized minimum norm solution, and used to interpret the timecourse of fMRI. Spatial concordance was observed between fMRI and MEG repetition effects from 350 to 450 ms within bilateral occipitotemporal and medial temporal, left prefrontal, and left posterior temporal cortex. Additionally, MEG revealed widespread sources within left temporoparietal regions, whereas fMRI revealed bilateral reductions in occipitotemporal and left superior frontal, and increases in inferior parietal, precuneus, and dorsolateral prefrontal activity. BOLD suppression in left posterior temporal, left inferior prefrontal, and right occipitotemporal cortex correlated with MEG repetition-related reductions. IEEG responses from all three regions supported the timecourse of MEG and localization of fMRI. Furthermore, iEEG decreases to repeated words were associated with decreased gamma power in several regions, providing evidence that gamma oscillations are tightly coupled to cognitive phenomena and reflect regional activations seen in the BOLD signal. Copyright 2010 Elsevier Inc. All rights reserved.

Multimodal imaging of repetition priming: Using fMRI, MEG, and intracranial EEG to reveal spatiotemporal profiles of word processing

PubMed Central

McDonald, Carrie R.; Thesen, Thomas; Carlson, Chad; Blumberg, Mark; Girard, Holly M.; Trongnetrpunya, Amy; Sherfey, Jason S.; Devinsky, Orrin; Kuzniecky, Rubin; Dolye, Werner K.; Cash, Sydney S.; Leonard, Matt K.; Hagler, Donald J.; Dale, Anders M.; Halgren, Eric

2010-01-01

Repetition priming is a core feature of memory processing whose anatomical correlates remain poorly understood. In this study, we use advanced multimodal imaging (functional magnetic resonance imaging (fMRI) and magnetoencephalography; MEG) to investigate the spatiotemporal profile of repetition priming. We use intracranial electroencephalography (iEEG) to validate our fMRI/MEG measurements. Twelve controls completed a semantic judgment task with fMRI and MEG that included words presented once (new, ‘N’) and words that repeated (old, ‘O’). Six patients with epilepsy completed the same task during iEEG recordings. Blood-oxygen level dependent (BOLD) responses for N vs O words were examined across the cortical surface and within regions of interest. MEG waveforms for N vs O words were estimated using a noise-normalized minimum norm solution, and used to interpret the timecourse of fMRI. Spatial concordance was observed between fMRI and MEG repetition effects from 350–450ms within bilateral occipitotemporal and medial temporal, left prefrontal, and left posterior temporal cortex. Additionally, MEG revealed widespread sources within left temporoparietal regions, whereas fMRI revealed bilateral reductions in occipitotemporal and left superior frontal, and increases in inferior parietal, precuneus, and dorsolateral prefrontal activity. BOLD suppression in left posterior temporal, left inferior prefrontal, and right occipitotemporal cortex correlated with MEG repetition-related reductions. IEEG responses from all three regions supported the timecourse of MEG and localization of fMRI. Furthermore, iEEG decreases to repeated words were associated with decreased gamma power in several regions, providing evidence that gamma oscillations are tightly coupled to cognitive phenomena and reflect regional activations seen in the BOLD signal. PMID:20620212

Vascular risk factor burden correlates with cerebrovascular reactivity but not resting state coactivation in the default mode network.

PubMed

Tchistiakova, Ekaterina; Crane, David E; Mikulis, David J; Anderson, Nicole D; Greenwood, Carol E; Black, Sandra E; MacIntosh, Bradley J

2015-11-01

White matter hyperintensities (WMH) are prevalent among older adults and are often associated with cognitive decline and increased risk of stroke and dementia. Vascular risk factors (VRFs) are linked to WMH, yet the impact of multiple VRFs on gray matter function is still unclear. The goal of this study was to test for associations between the number of VRFs and cerebrovascular reactivity (CVR) and resting state (RS) coactivation among individuals with WMH. Twenty-nine participants with suspected WMH were grouped based on the number of VRFs (subgroups: 0, 1, or ≥2). CVR and RS coactivation were measured with blood oxygenation level-dependent (BOLD) imaging on a 3T magnetic resonance imaging (MRI) system during hypercapnia and rest, respectively. Default-mode (DMN), sensory-motor, and medial-visual networks, generated using independent component analysis of RS-BOLD, were selected as networks of interest (NOIs). CVR-BOLD was analyzed using two methods: 1) a model-based approach using CO2 traces, and 2) a dual-regression (DR) approach using NOIs as spatial inputs. Average CVR and RS coactivations within NOIs were compared between VRF subgroups. A secondary analysis investigated the correlation between CVR and RS coactivation. VRF subgroup differences were detected using DR-based CVR in the DMN (F20,2  = 5.17, P = 0.015) but not the model-based CVR nor RS coactivation. DR-based CVR was correlated with RS coactivation in the DMN (r(2)  = 0.28, P = 0.006) but not the sensory-motor nor medial-visual NOIs. In individuals with WMH, CVR in the DMN was inversely associated with the number of VRFs and correlated with RS coactivation. © 2015 Wiley Periodicals, Inc.

Mapping the MRI voxel volume in which thermal noise matches physiological noise--implications for fMRI.

PubMed

Bodurka, J; Ye, F; Petridou, N; Murphy, K; Bandettini, P A

2007-01-15

This work addresses the choice of the imaging voxel volume in blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI). Noise of physiological origin that is present in the voxel time course is a prohibitive factor in the detection of small activation-induced BOLD signal changes. If the physiological noise contribution dominates over the temporal fluctuation contribution in the imaging voxel, further increases in the voxel signal-to-noise ratio (SNR) will have diminished corresponding increases in temporal signal-to-noise (TSNR), resulting in reduced corresponding increases in the ability to detect activation induced signal changes. On the other hand, if the thermal and system noise dominate (suggesting a relatively low SNR) further decreases in SNR can prohibit detection of activation-induced signal changes. Here we have proposed and called the "suggested" voxel volume for fMRI the volume where thermal plus system-related and physiological noise variances are equal. Based on this condition we have created maps of fMRI suggested voxel volume from our experimental data at 3T, since this value will spatially vary depending on the contribution of physiologic noise in each voxel. Based on our fast EPI segmentation technique we have found that for gray matter (GM), white matter (WM), and cerebral spinal fluid (CSF) brain compartments the mean suggested cubical voxel volume is: (1.8 mm)3, (2.1 mm)3 and (1.4 mm)3, respectively. Serendipitously, (1.8 mm)3 cubical voxel volume for GM approximately matches the cortical thickness, thus optimizing BOLD contrast by minimizing partial volume averaging. The introduced suggested fMRI voxel volume can be a useful parameter for choice of imaging volume for functional studies.

Frequency-Dependent Modulation of Regional Synchrony in the Human Brain by Eyes Open and Eyes Closed Resting-States.

PubMed

Song, Xiaopeng; Zhou, Shuqin; Zhang, Yi; Liu, Yijun; Zhu, Huaiqiu; Gao, Jia-Hong

2015-01-01

The eyes-open (EO) and eyes-closed (EC) states have differential effects on BOLD-fMRI signal dynamics, affecting both the BOLD oscillation frequency of a single voxel and the regional homogeneity (ReHo) of several neighboring voxels. To explore how the two resting-states modulate the local synchrony through different frequency bands, we decomposed the time series of each voxel into several components that fell into distinct frequency bands. The ReHo in each of the bands was calculated and compared between the EO and EC conditions. The cross-voxel correlations between the mean frequency and the overall ReHo of each voxel's original BOLD series in different brain areas were also calculated and compared between the two states. Compared with the EC state, ReHo decreased with EO in a wide frequency band of 0.01-0.25 Hz in the bilateral thalamus, sensorimotor network, and superior temporal gyrus, while ReHo increased significantly in the band of 0-0.01 Hz in the primary visual cortex, and in a higher frequency band of 0.02-0.1 Hz in the higher order visual areas. The cross-voxel correlations between the frequency and overall ReHo were negative in all the brain areas but varied from region to region. These correlations were stronger with EO in the visual network and the default mode network. Our results suggested that different frequency bands of ReHo showed different sensitivity to the modulation of EO-EC states. The better spatial consistency between the frequency and overall ReHo maps indicated that the brain might adopt a stricter frequency-dependent configuration with EO than with EC.

Reduced Dynamic Coupling Between Spontaneous BOLD-CBF Fluctuations in Older Adults: A Dual-Echo pCASL Study.

PubMed

Chiacchiaretta, Piero; Cerritelli, Francesco; Bubbico, Giovanna; Perrucci, Mauro Gianni; Ferretti, Antonio

2018-01-01

Measurement of the dynamic coupling between spontaneous Blood Oxygenation Level Dependent (BOLD) and cerebral blood flow (CBF) fluctuations has been recently proposed as a method to probe resting-state brain physiology. Here we investigated how the dynamic BOLD-CBF coupling during resting-state is affected by aging. Fifteen young subjects and 17 healthy elderlies were studied using a dual-echo pCASL sequence. We found that the dynamic BOLD-CBF coupling was markedly reduced in elderlies, in particular in the left supramarginal gyrus, an area known to be involved in verbal working memory and episodic memory. Moreover, correcting for temporal shift between BOLD and CBF timecourses resulted in an increased correlation of the two signals for both groups, but with a larger increase for elderlies. However, even after temporal shift correction, a significantly decreased correlation was still observed for elderlies in the left supramarginal gyrus, indicating that the age-related dynamic BOLD-CBF uncoupling in this region is more pronounced and can be only partially explained with a simple time-shift between the two signals. Interestingly, these results were observed in a group of elderlies with normal cognitive functions, suggesting that the study of dynamic BOLD-CBF coupling during resting-state is a promising technique, potentially able to provide early biomarkers of functional changes in the aging brain.

The role of boldness in psychopathy: A study of academic and clinical perceptions.

PubMed

Berg, Joanna M; Lilienfeld, Scott O; Sellbom, Martin

2017-10-01

The relevance of boldness to psychopathy has recently become a major flashpoint of scientific controversy. Although some authors have contended that boldness is a necessary (although insufficient) component of psychopathy, others have asserted that it is largely or entirely irrelevant to psychopathy. We addressed this issue by examining clinical perceptions of the relevance of the 3 triarchic dimensions (boldness, disinhibition, and meanness) to psychopathy among a sample of mental health professionals and graduate students (N = 228) using a vignette-based, person-centered methodology. A vignette comprising boldness descriptors afforded statistically significant and moderate to large (Cohen's ds ranged from .47 to .99) increases in perceived resemblance to overall psychopathy above and beyond the other triarchic dimensions, both singly and jointly; these findings extended largely to clinical perceptions of Factor 1 (i.e., interpersonal and affective aspects of psychopathy) but not Factor 2 (i.e., impulsive and antisocial aspects of psychopathy) resemblance. Contrary to the claims of some recent authors, boldness alone was perceived as being as relevant to psychopathy as was disinhibition, although both dimensions were perceived as less relevant to psychopathy than was meanness. These findings offer strong support for the contention that boldness is regarded as a key feature of classical psychopathy and are broadly consistent with interpersonal models of psychopathy. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Shyness and boldness in pumpkinseed sunfish: individual differences are context-specific.

PubMed

Coleman; Wilson

1998-10-01

Natural selection often promotes a mix of behavioural phenotypes in a population. Adaptive variation in the propensity to take risks might explain individual differences in shyness and boldness in humans and other species. It is often implicitly assumed that shyness and boldness are general personality traits expressed across many situations. From the evolutionary standpoint, however, individual differences that are adaptive in one context (e.g. predator defence) may not be adaptive in other contexts (e.g. exploration of the physical environment or intraspecific social interactions). We measured the context specificity of shyness and boldness in a natural population of juvenile pumpkinseed sunfish, Lepomis gibbosus, by exposing the fish to a potentially threatening stimulus (a red-tipped metrestick extended towards the individual) and a nonthreatening stimulus (a novel food source). We also related these measures of shyness and boldness to behaviours observed during focal observations, both before and after the introduction of a predator (largemouth bass, Micropterus salmoides). Consistent individual differences were found within both contexts, but individual differences did not correlate across contexts. Furthermore, fish that were scored as intermediate in their response to the metrestick behaved most boldly as foragers and in response to the bass predators. These results suggest that shyness and boldness are context-specific and may not exist as a one-dimensional behavioural continuum even within a single context. Copyright 1998 The Association for the Study of Animal Behaviour.

12 CFR 192.255 - What must the form of proxy include?

Code of Federal Regulations, 2012 CFR

2012-01-01

... include? The form of proxy must include all of the following: (a) A statement in bold face type stating.... (d) The phrase “Revocable Proxy” in bold face type (at least 18 point). (e) A description of any... management will vote the proxy in accordance with the member's specifications. (j) A statement in bold face...

Real-time fMRI neurofeedback of the mediodorsal and anterior thalamus enhances correlation between thalamic BOLD activity and alpha EEG rhythm.

PubMed

Zotev, Vadim; Misaki, Masaya; Phillips, Raquel; Wong, Chung Ki; Bodurka, Jerzy

2018-02-01

Real-time fMRI neurofeedback (rtfMRI-nf) with simultaneous EEG allows volitional modulation of BOLD activity of target brain regions and investigation of related electrophysiological activity. We applied this approach to study correlations between thalamic BOLD activity and alpha EEG rhythm. Healthy volunteers in the experimental group (EG, n = 15) learned to upregulate BOLD activity of the target region consisting of the mediodorsal (MD) and anterior (AN) thalamic nuclei using rtfMRI-nf during retrieval of happy autobiographical memories. Healthy subjects in the control group (CG, n = 14) were provided with a sham feedback. The EG participants were able to significantly increase BOLD activities of the MD and AN. Functional connectivity between the MD and the inferior precuneus was significantly enhanced during the rtfMRI-nf task. Average individual changes in the occipital alpha EEG power significantly correlated with the average MD BOLD activity levels for the EG. Temporal correlations between the occipital alpha EEG power and BOLD activities of the MD and AN were significantly enhanced, during the rtfMRI-nf task, for the EG compared to the CG. Temporal correlations with the alpha power were also significantly enhanced for the posterior nodes of the default mode network, including the precuneus/posterior cingulate, and for the dorsal striatum. Our findings suggest that the temporal correlation between the MD BOLD activity and posterior alpha EEG power is modulated by the interaction between the MD and the inferior precuneus, reflected in their functional connectivity. Our results demonstrate the potential of the rtfMRI-nf with simultaneous EEG for noninvasive neuromodulation studies of human brain function. © 2017 Wiley Periodicals, Inc.

Inferring neural activity from BOLD signals through nonlinear optimization.

PubMed

Vakorin, Vasily A; Krakovska, Olga O; Borowsky, Ron; Sarty, Gordon E

2007-11-01

The blood oxygen level-dependent (BOLD) fMRI signal does not measure neuronal activity directly. This fact is a key concern for interpreting functional imaging data based on BOLD. Mathematical models describing the path from neural activity to the BOLD response allow us to numerically solve the inverse problem of estimating the timing and amplitude of the neuronal activity underlying the BOLD signal. In fact, these models can be viewed as an advanced substitute for the impulse response function. In this work, the issue of estimating the dynamics of neuronal activity from the observed BOLD signal is considered within the framework of optimization problems. The model is based on the extended "balloon" model and describes the conversion of neuronal signals into the BOLD response through the transitional dynamics of the blood flow-inducing signal, cerebral blood flow, cerebral blood volume and deoxyhemoglobin concentration. Global optimization techniques are applied to find a control input (the neuronal activity and/or the biophysical parameters in the model) that causes the system to follow an admissible solution to minimize discrepancy between model and experimental data. As an alternative to a local linearization (LL) filtering scheme, the optimization method escapes the linearization of the transition system and provides a possibility to search for the global optimum, avoiding spurious local minima. We have found that the dynamics of the neural signals and the physiological variables as well as the biophysical parameters can be robustly reconstructed from the BOLD responses. Furthermore, it is shown that spiking off/on dynamics of the neural activity is the natural mathematical solution of the model. Incorporating, in addition, the expansion of the neural input by smooth basis functions, representing a low-pass filtering, allows us to model local field potential (LFP) solutions instead of spiking solutions.

Differences in aggression, activity and boldness between native and introduced populations of an invasive crayfish

USGS Publications Warehouse

Pintor, L.M.; Sih, A.; Bauer, M.L.

2008-01-01

Aggressiveness, along with foraging voracity and boldness, are key behavioral mechanisms underlying the competitive displacement and invasion success of exotic species. However, do aggressiveness, voracity and boldness of the invader depend on the presence of an ecologically similar native competitor in the invaded community? We conducted four behavioral assays to compare aggression, foraging voracity, threat response and boldness to forage under predation risk of multiple populations of exotic signal crayfish Pacifastacus leniusculus across its native and invaded range with and without a native congener, the Shasta crayfish P. fortis. We predicted that signal crayfish from the invaded range and sympatric with a native congener (IRS) should be more aggressive to outcompete a close competitor than populations from the native range (NR) or invaded range and allopatric to a native congener (IRA). Furthermore, we predicted that IRS populations of signal crayfish should be more voracious, but less bold to forage under predation risk since native predators and prey likely possess appropriate behavioral responses to the invader. Contrary to our predictions, results indicated that IRA signal crayfish were more aggressive towards conspecifics and more voracious and active foragers, yet also bolder to forage under predation risk in comparison to NR and IRS populations, which did not differ in behavior. Higher aggression/voracity/ boldness was positively correlated with prey consumption rates, and hence potential impacts on prey. We suggest that the positive correlations between aggression/voracity/boldness are the result of an overall aggression syndrome. Results of stream surveys indicated that IRA streams have significantly lower prey biomass than in IRS streams, which may drive invading signal crayfish to be more aggressive/voracious/bold to acquire resources to establish a population. ?? 2008 The Authors.

Plasticity varies with boldness in a weakly-electric fish.

PubMed

Kareklas, Kyriacos; Arnott, Gareth; Elwood, Robert W; Holland, Richard A

2016-01-01

The expression of animal personality is indicated by patterns of consistency in individual behaviour. Often, the differences exhibited between individuals are consistent across situations. However, between some situations, this can be biased by variable levels of individual plasticity. The interaction between individual plasticity and animal personality can be illustrated by examining situation-sensitive personality traits such as boldness (i.e. risk-taking and exploration tendency). For the weakly electric fish Gnathonemus petersii, light condition is a major factor influencing behaviour. Adapted to navigate in low-light conditions, this species chooses to be more active in dark environments where risk from visual predators is lower. However, G. petersii also exhibit individual differences in their degree of behavioural change from light to dark. The present study, therefore, aims to examine if an increase of motivation to explore in the safety of the dark, not only affects mean levels of boldness, but also the variation between individuals, as a result of differences in individual plasticity. Boldness was consistent between a novel-object and a novel-environment situation in bright light. However, no consistency in boldness was noted between a bright (risky) and a dark (safe) novel environment. Furthermore, there was a negative association between boldness and the degree of change across novel environments, with shier individuals exhibiting greater behavioural plasticity. This study highlights that individual plasticity can vary with personality. In addition, the effect of light suggests that variation in boldness is situation specific. Finally, there appears to be a trade-off between personality and individual plasticity with shy but plastic individuals minimizing costs when perceiving risk and bold but stable individuals consistently maximizing rewards, which can be maladaptive.

Are Fearless Dominance Traits Superfluous in Operationalizing Psychopathy? Incremental Validity and Sex Differences

PubMed Central

Murphy, Brett; Lilienfeld, Scott; Skeem, Jennifer; Edens, John

2016-01-01

Researchers are vigorously debating whether psychopathic personality includes seemingly adaptive traits, especially social and physical boldness. In a large sample (N=1565) of adult offenders, we examined the incremental validity of two operationalizations of boldness (Fearless Dominance traits in the Psychopathy Personality Inventory, Lilienfeld & Andrews, 1996; Boldness traits in the Triarchic Model of Psychopathy, Patrick et al, 2009), above and beyond other characteristics of psychopathy, in statistically predicting scores on four psychopathy-related measures, including the Psychopathy Checklist-Revised (PCL-R). The incremental validity added by boldness traits in predicting the PCL-R’s representation of psychopathy was especially pronounced for interpersonal traits (e.g., superficial charm, deceitfulness). Our analyses, however, revealed unexpected sex differences in the relevance of these traits to psychopathy, with boldness traits exhibiting reduced importance for psychopathy in women. We discuss the implications of these findings for measurement models of psychopathy. PMID:26866795

A review of calibrated blood oxygenation level-dependent (BOLD) methods for the measurement of task-induced changes in brain oxygen metabolism

PubMed Central

Blockley, Nicholas P.; Griffeth, Valerie E. M.; Simon, Aaron B.; Buxton, Richard B.

2013-01-01

The dynamics of the blood oxygenation level-dependent (BOLD) response are dependent on changes in cerebral blood flow, cerebral blood volume and the cerebral metabolic rate of oxygen consumption. Furthermore, the amplitude of the response is dependent on the baseline physiological state, defined by the haematocrit, oxygen extraction fraction and cerebral blood volume. As a result of this complex dependence, the accurate interpretation of BOLD data and robust intersubject comparisons when the baseline physiology is varied are difficult. The calibrated BOLD technique was developed to address these issues. However, the methodology is complex and its full promise has not yet been realised. In this review, the theoretical underpinnings of calibrated BOLD, and issues regarding this theory that are still to be resolved, are discussed. Important aspects of practical implementation are reviewed and reported applications of this methodology are presented. PMID:22945365

Opposite selection on behavioural types by active and passive fishing gears in a simulated guppy Poecilia reticulata fishery.

PubMed

Diaz Pauli, B; Wiech, M; Heino, M; Utne-Palm, A C

2015-03-01

This study assessed whether fishing gear was selective on behavioural traits, such as boldness and activity, and how this was related with a productivity trait, growth. Female guppies Poecilia reticulata were screened for their behaviour on the shy-bold axis and activity, and then tested whether they were captured differently by passive and active fishing gear, here represented by a trap and a trawl. Both gears were selective on boldness; bold individuals were caught faster by the trap, but escaped the trawl more often. Boldness and gear vulnerability showed weak correlations with activity and growth. The results draw attention to the importance of the behavioural dimension of fishing: selective fishing on behavioural traits will change the trait composition of the population, and might eventually affect resilience and fishery productivity. © 2015 The Fisheries Society of the British Isles.

PubMed Central

2011-01-01

Events for which complete information is available are listed in chronological order. Those taking place in Italy are in bold script. Information, following the style of the present list, should be submitted to the Editorial Secretariat of Acta Otorhinolaryngologica Italica. In accordance with the Regulations of S.I.O. and Ch.C.-F. (Art. 8) Members of the Society organising Courses, Congresses or other scientific events should inform the Secretary of the Association (A.U.O.R.L., A.O.O.I.) within the deadlines set down in the respective Statutes and Regulations.

Amnestic mild cognitive impairment: functional MR imaging study of response in posterior cingulate cortex and adjacent precuneus during problem-solving tasks.

PubMed

Jin, Guangwei; Li, Kuncheng; Hu, Yingying; Qin, Yulin; Wang, Xiangqing; Xiang, Jie; Yang, Yanhui; Lu, Jie; Zhong, Ning

2011-11-01

To compare the blood oxygen level-dependent (BOLD) response, measured with functional magnetic resonance (MR) imaging, in the posterior cingulate cortex (PCC) and adjacent precuneus regions between healthy control subjects and patients with amnestic mild cognitive impairment (MCI) during problem-solving tasks. This study was approved by the institutional review board. Each subject provided written informed consent. Thirteen patients with amnestic MCI and 13 age- and sex-matched healthy control subjects participated in the study. The functional magnetic resonance (MR) imaging tasks were simplified 4 × 4-grid number placement puzzles that were divided into a simple task (using the row rule or the column rule to solve the puzzle) and a complex task (using both the row and column rules to solve the puzzle). Behavioral results and functional imaging results between the healthy control group and the amnestic MCI group were analyzed. The accuracy for the complex task in the healthy control group was significantly higher than that in the amnestic MCI group (P < .05). The healthy control group exhibited a deactivated BOLD signal intensity (SI) change in the bilateral PCC and adjacent precuneus regions during the complex task, whereas the amnestic MCI group showed activation. The positive linear correlations between the BOLD SI change in bilateral PCC and adjacent precuneus regions and in bilateral hippocampi in the amnestic MCI group were significant (P < .001), while in the healthy control group, they were not (P ≥ .23). These findings suggest that an altered BOLD response in amnestic MCI patients during complex tasks might be related to a decline in problem-solving ability and to memory impairment and, thus, may indicate a compensatory response to memory impairment. RSNA, 2011

Mapping and characterization of positive and negative BOLD responses to visual stimulation in multiple brain regions at 7T.

PubMed

Jorge, João; Figueiredo, Patrícia; Gruetter, Rolf; van der Zwaag, Wietske

2018-06-01

External stimuli and tasks often elicit negative BOLD responses in various brain regions, and growing experimental evidence supports that these phenomena are functionally meaningful. In this work, the high sensitivity available at 7T was explored to map and characterize both positive (PBRs) and negative BOLD responses (NBRs) to visual checkerboard stimulation, occurring in various brain regions within and beyond the visual cortex. Recently-proposed accelerated fMRI techniques were employed for data acquisition, and procedures for exclusion of large draining vein contributions, together with ICA-assisted denoising, were included in the analysis to improve response estimation. Besides the visual cortex, significant PBRs were found in the lateral geniculate nucleus and superior colliculus, as well as the pre-central sulcus; in these regions, response durations increased monotonically with stimulus duration, in tight covariation with the visual PBR duration. Significant NBRs were found in the visual cortex, auditory cortex, default-mode network (DMN) and superior parietal lobule; NBR durations also tended to increase with stimulus duration, but were significantly less sustained than the visual PBR, especially for the DMN and superior parietal lobule. Responses in visual and auditory cortex were further studied for checkerboard contrast dependence, and their amplitudes were found to increase monotonically with contrast, linearly correlated with the visual PBR amplitude. Overall, these findings suggest the presence of dynamic neuronal interactions across multiple brain regions, sensitive to stimulus intensity and duration, and demonstrate the richness of information obtainable when jointly mapping positive and negative BOLD responses at a whole-brain scale, with ultra-high field fMRI. © 2018 Wiley Periodicals, Inc.

12 CFR 563b.255 - What must the form of proxy include?

Code of Federal Regulations, 2013 CFR

2013-01-01

... proxy include? The form of proxy must include all of the following: (a) A statement in bold face type... separately. (d) The phrase “Revocable Proxy” in bold face type (at least 18 point). (e) A description of any... management will vote the proxy in accordance with the member's specifications. (j) A statement in bold face...

12 CFR 563b.255 - What must the form of proxy include?

Code of Federal Regulations, 2012 CFR

2012-01-01

... proxy include? The form of proxy must include all of the following: (a) A statement in bold face type... separately. (d) The phrase “Revocable Proxy” in bold face type (at least 18 point). (e) A description of any... management will vote the proxy in accordance with the member's specifications. (j) A statement in bold face...

Trait and state anxiety is marked by increased working memory-related parietal BOLD signal.

PubMed

Ford, Talitha C; Simpson, Tamara; McPhee, Grace; Stough, Con; Downey, Luke A

2018-05-16

Anxiety is associated with compromised cognitive control functions, such as working memory. State and trait anxiety within the non-clinical population can be utilised to investigate potential neural markers for anxiety, which may help to elucidate potential prevention and intervention methods. Thirty-two healthy adults (20 female, 12 male), aged between 30 and 65 years, performed a 2-back task whilst fMRI BOLD signal was acquired using a 3T scanner. Mean BOLD signal was obtained in cognitive control network regions of interest of: left and right dorsolateral prefrontal cortex (DLPFC) and posterior parietal lobe (PPL), and medial prefrontal cortex (MPFC). State and trait anxiety levels were recorded. Higher overall anxiety was moderately associated with more left and right PPL BOLD signal; there was a weak relationship between anxiety and left DLPFC BOLD signal. MPFC BOLD signal and trait anxiety were moderately associated with overall 2-back task performance. These findings suggest that non-clinical anxiety affects the recruitment of cortical resources during working memory, but that anxiety does not impair performance during a 2-back task. Copyright © 2018 Elsevier B.V. All rights reserved.

Ecological consequences of the bold-shy continuum: the effect of predator boldness on prey risk.

PubMed

Ioannou, C C; Payne, M; Krause, J

2008-08-01

Although the existence of different personality traits within and between animal populations has been relatively well established, the ecological implications of this variation remain neglected. In this study we tested whether differences in the boldness of pairs of three-spined sticklebacks led to differential predation risk in their prey, Chironomidae larvae. Bolder pairs, those that left a refuge and crossed the tank mid-line sooner, ate a greater proportion of prey in 10 min than less bold fish (therefore prey were at a greater per capita risk). Fish crossed the mid-line more rapidly when a larger number of prey were presented, suggesting they accepted greater risk in return for a larger foraging reward. Perception of predation risk also affected the differences between fish in boldness, as larger fish crossed the mid-line sooner after leaving the refuge (larger fish are less at risk from predation). Hence, an interesting trophic interaction occurs, where the risk experienced by the chironomid larvae is determined by the risk perceived by their predators. Through the variation generated by boldness, a form of behaviourally mediated trophic cascade can occur within (as well as between) communities.

Study protocol: The back pain outcomes using longitudinal data (BOLD) registry

PubMed Central

2012-01-01

Background Back pain is one of the most important causes of functional limitation, disability, and utilization of health care resources for adults of all ages, but especially among older adults. Despite the high prevalence of back pain in this population, important questions remain unanswered regarding the comparative effectiveness of commonly used diagnostic tests and treatments in the elderly. The overall goal of the Back pain Outcomes using Longitudinal Data (BOLD) project is to establish a rich, sustainable registry to describe the natural history and evaluate prospectively the effectiveness, safety, and cost-effectiveness of interventions for patients 65 and older with back pain. Methods/design BOLD is enrolling 5,000 patients ≥ 65 years old who present to a primary care physician with a new episode of back pain. We are recruiting study participants from three integrated health systems (Kaiser-Permanente Northern California, Henry Ford Health System in Detroit and Harvard Vanguard Medical Associates/ Harvard Pilgrim Health Care in Boston). Registry patients complete validated, standardized measures of pain, back pain-related disability, and health-related quality of life at enrollment and 3, 6 and 12 months later. We also have available for analysis the clinical and administrative data in the participating health systems’ electronic medical records. Using registry data, we will conduct an observational cohort study of early imaging compared to no early imaging among patients with new episodes of back pain. The aims are to: 1) identify predictors of early imaging and; 2) compare pain, functional outcomes, diagnostic testing and treatment utilization of patients who receive early imaging versus patients who do not receive early imaging. In terms of predictors, we will examine patient factors as well as physician factors. Discussion By establishing the BOLD registry, we are creating a resource that contains patient-reported outcome measures as well as electronic medical record data for elderly patients with back pain. The richness of our data will allow better matching for comparative effectiveness studies than is currently possible with existing datasets. BOLD will enrich the existing knowledge base regarding back pain in the elderly to help clinicians and patients make informed, evidence-based decisions regarding their care. PMID:22554166

Modulating the focus of attention for spoken words at encoding affects frontoparietal activation for incidental verbal memory.

PubMed

Christensen, Thomas A; Almryde, Kyle R; Fidler, Lesley J; Lockwood, Julie L; Antonucci, Sharon M; Plante, Elena

2012-01-01

Attention is crucial for encoding information into memory, and current dual-process models seek to explain the roles of attention in both recollection memory and incidental-perceptual memory processes. The present study combined an incidental memory paradigm with event-related functional MRI to examine the effect of attention at encoding on the subsequent neural activation associated with unintended perceptual memory for spoken words. At encoding, we systematically varied attention levels as listeners heard a list of single English nouns. We then presented these words again in the context of a recognition task and assessed the effect of modulating attention at encoding on the BOLD responses to words that were either attended strongly, weakly, or not heard previously. MRI revealed activity in right-lateralized inferior parietal and prefrontal regions, and positive BOLD signals varied with the relative level of attention present at encoding. Temporal analysis of hemodynamic responses further showed that the time course of BOLD activity was modulated differentially by unintentionally encoded words compared to novel items. Our findings largely support current models of memory consolidation and retrieval, but they also provide fresh evidence for hemispheric differences and functional subdivisions in right frontoparietal attention networks that help shape auditory episodic recall.

Modulating the Focus of Attention for Spoken Words at Encoding Affects Frontoparietal Activation for Incidental Verbal Memory

PubMed Central

Christensen, Thomas A.; Almryde, Kyle R.; Fidler, Lesley J.; Lockwood, Julie L.; Antonucci, Sharon M.; Plante, Elena

2012-01-01

Attention is crucial for encoding information into memory, and current dual-process models seek to explain the roles of attention in both recollection memory and incidental-perceptual memory processes. The present study combined an incidental memory paradigm with event-related functional MRI to examine the effect of attention at encoding on the subsequent neural activation associated with unintended perceptual memory for spoken words. At encoding, we systematically varied attention levels as listeners heard a list of single English nouns. We then presented these words again in the context of a recognition task and assessed the effect of modulating attention at encoding on the BOLD responses to words that were either attended strongly, weakly, or not heard previously. MRI revealed activity in right-lateralized inferior parietal and prefrontal regions, and positive BOLD signals varied with the relative level of attention present at encoding. Temporal analysis of hemodynamic responses further showed that the time course of BOLD activity was modulated differentially by unintentionally encoded words compared to novel items. Our findings largely support current models of memory consolidation and retrieval, but they also provide fresh evidence for hemispheric differences and functional subdivisions in right frontoparietal attention networks that help shape auditory episodic recall. PMID:22144982

Characterizing Resting-State Brain Function Using Arterial Spin Labeling

PubMed Central

Jann, Kay; Wang, Danny J.J.

2015-01-01

Abstract Arterial spin labeling (ASL) is an increasingly established magnetic resonance imaging (MRI) technique that is finding broader applications in studying the healthy and diseased brain. This review addresses the use of ASL to assess brain function in the resting state. Following a brief technical description, we discuss the use of ASL in the following main categories: (1) resting-state functional connectivity (FC) measurement: the use of ASL-based cerebral blood flow (CBF) measurements as an alternative to the blood oxygen level-dependent (BOLD) technique to assess resting-state FC; (2) the link between network CBF and FC measurements: the use of network CBF as a surrogate of the metabolic activity within corresponding networks; and (3) the study of resting-state dynamic CBF-BOLD coupling and cerebral metabolism: the use of dynamic CBF information obtained using ASL to assess dynamic CBF-BOLD coupling and oxidative metabolism in the resting state. In addition, we summarize some future challenges and interesting research directions for ASL, including slice-accelerated (multiband) imaging as well as the effects of motion and other physiological confounds on perfusion-based FC measurement. In summary, this work reviews the state-of-the-art of ASL and establishes it as an increasingly viable MRI technique with high translational value in studying resting-state brain function. PMID:26106930

Anosognosia in mild cognitive impairment: Relationship to activation of cortical midline structures involved in self-appraisal

PubMed Central

Ries, Michele L.; Jabbar, Britta M.; Schmitz, Taylor W.; Trivedi, Mehul A.; Gleason, Carey E.; Carlsson, Cynthia M.; Rowley, Howard A.; Asthana, Sanjay; Johnson, Sterling C.

2009-01-01

Awareness of cognitive dysfunction shown by individuals with Mild Cognitive Impairment (MCI), a condition conferring risk for Alzheimer’s disease (AD), is variable. Anosognosia, or unawareness of loss of function, is beginning to be recognized as an important clinical symptom of MCI. However, little is known about the brain substrates underlying this symptom. We hypothesized that MCI participants’ activation of cortical midline structures (CMS) during self-appraisal would covary with level of insight into cognitive difficulties (indexed by a discrepancy score between patient and informant ratings of cognitive decline in each MCI participant). To address this hypothesis, we first compared 16 MCI participants and 16 age-matched controls, examining brain regions showing conjoint or differential BOLD response during self-appraisal. Second, we used regression to investigate the relationship between awareness of deficit in MCI and BOLD activity during self-appraisal, controlling for extent of memory impairment. Between-group comparisons indicated that MCI participants show subtly attenuated CMS activity during self-appraisal. Regression analysis revealed a highly-significant relationship between BOLD response during self-appraisal and self-awareness of deficit in MCI. This finding highlights the level of anosognosia in MCI as an important predictor of response to self-appraisal in cortical midline structures, brain regions vulnerable to changes in early AD. PMID:17445294

Rearing environment influences boldness and prey acquisition behavior, and brain and lens development of bull trout

USGS Publications Warehouse

Brignon, William R.; Pike, Martin M.; Ebbesson, Lars O.E.; Schaller, Howard A.; Peterson, James T.; Schreck, Carl B.

2018-01-01

Animals reared in barren captive environments exhibit different developmental trajectories and behaviors than wild counterparts. Hence, the captive phenotypes may influence the success of reintroduction and recovery programs for threatened and endangered species. We collected wild bull trout embryos from the Metolius River Basin, Oregon and reared them in differing environments to better understand how captivity affects the bull trout Salvelinus confluentusphenotype. We compared the boldness and prey acquisition behaviors and development of the brain and eye lens of bull trout reared in conventional barren and more structurally complex captive environments with that of wild fish. Wild fish and captive reared fish from complex habitats exhibited a greater level of boldness and prey acquisition ability, than fish reared in conventional captive environments. In addition, the eye lens of conventionally reared bull trout was larger than complex reared captive fish or same age wild fish. Interestingly, we detected wild fish had a smaller relative cerebellum than either captive reared treatment. Our results suggest that rearing fish in more complex captive environments can create a more wild-like phenotype than conventional rearing practices. A better understanding of the effects of captivity on the development and behavior of bull trout can inform rearing and reintroduction programs though prediction of the performance of released individuals.

Perfusion information extracted from resting state functional magnetic resonance imaging.

PubMed

Tong, Yunjie; Lindsey, Kimberly P; Hocke, Lia M; Vitaliano, Gordana; Mintzopoulos, Dionyssios; Frederick, Blaise deB

2017-02-01

It is widely known that blood oxygenation level dependent (BOLD) contrast in functional magnetic resonance imaging (fMRI) is an indirect measure for neuronal activations through neurovascular coupling. The BOLD signal is also influenced by many non-neuronal physiological fluctuations. In previous resting state (RS) fMRI studies, we have identified a moving systemic low frequency oscillation (sLFO) in BOLD signal and were able to track its passage through the brain. We hypothesized that this seemingly intrinsic signal moves with the blood, and therefore, its dynamic patterns represent cerebral blood flow. In this study, we tested this hypothesis by performing Dynamic Susceptibility Contrast (DSC) MRI scans (i.e. bolus tracking) following the RS scans on eight healthy subjects. The dynamic patterns of sLFO derived from RS data were compared with the bolus flow visually and quantitatively. We found that the flow of sLFO derived from RS fMRI does to a large extent represent the blood flow measured with DSC. The small differences, we hypothesize, are largely due to the difference between the methods in their sensitivity to different vessel types. We conclude that the flow of sLFO in RS visualized by our time delay method represents the blood flow in the capillaries and veins in the brain.

Controlling conflict from interfering long-term memory representations.

PubMed

Jost, Kerstin; Khader, Patrick H; Düsel, Peter; Richter, Franziska R; Rohde, Kristina B; Bien, Siegfried; Rösler, Frank

2012-05-01

Remembering is more than an activation of a memory trace. As retrieval cues are often not uniquely related to one specific memory, cognitive control should come into play to guide selective memory retrieval by focusing on relevant while ignoring irrelevant information. Here, we investigated, by means of EEG and fMRI, how the memory system deals with retrieval interference arising when retrieval cues are associated with two material types (faces and spatial positions), but only one is task-relevant. The topography of slow EEG potentials and the fMRI BOLD signal in posterior storage areas indicated that in such situations not only the relevant but also the irrelevant material becomes activated. This results in retrieval interference that triggers control processes mediated by the medial and lateral PFC, which are presumably involved in biasing target representations by boosting the task-relevant material. Moreover, memory-based conflict was found to be dissociable from response conflict that arises when the relevant and irrelevant materials imply different responses. The two types of conflict show different activations in the medial frontal cortex, supporting the claim of domain-specific prefrontal control systems.

Decoding vigilance with NIRS.

PubMed

Bogler, Carsten; Mehnert, Jan; Steinbrink, Jens; Haynes, John-Dylan

2014-01-01

Sustained, long-term cognitive workload is associated with variations and decrements in performance. Such fluctuations in vigilance can be a risk factor especially during dangerous attention demanding activities. Functional MRI studies have shown that attentional performance is correlated with BOLD-signals, especially in parietal and prefrontal cortical regions. An interesting question is whether these BOLD-signals could be measured in real-world scenarios, say to warn in a dangerous workplace whenever a subjects' vigilance is low. Because fMRI lacks the mobility needed for such applications, we tested whether the monitoring of vigilance might be possible using Near-Infrared Spectroscopy (NIRS). NIRS is a highly mobile technique that measures hemodynamics in the surface of the brain. We demonstrate that non-invasive NIRS signals correlate with vigilance. These signals carry enough information to decode subjects' reaction times at a single trial level.

Quantitative phenomenological model of the BOLD contrast mechanism

NASA Astrophysics Data System (ADS)

Dickson, John D.; Ash, Tom W. J.; Williams, Guy B.; Sukstanskii, Alexander L.; Ansorge, Richard E.; Yablonskiy, Dmitriy A.

2011-09-01

Different theoretical models of the BOLD contrast mechanism are used for many applications including BOLD quantification (qBOLD) and vessel size imaging, both in health and disease. Each model simplifies the system under consideration, making approximations about the structure of the blood vessel network and diffusion of water molecules through inhomogeneities in the magnetic field created by deoxyhemoglobin-containing blood vessels. In this study, Monte-Carlo methods are used to simulate the BOLD MR signal generated by diffusing water molecules in the presence of long, cylindrical blood vessels. Using these simulations we introduce a new, phenomenological model that is far more accurate over a range of blood oxygenation levels and blood vessel radii than existing models. This model could be used to extract physiological parameters of the blood vessel network from experimental data in BOLD-based experiments. We use our model to establish ranges of validity for the existing analytical models of Yablonskiy and Haacke, Kiselev and Posse, Sukstanskii and Yablonskiy (extended to the case of arbitrary time in the spin echo sequence) and Bauer et al. (extended to the case of randomly oriented cylinders). Although these models are shown to be accurate in the limits of diffusion under which they were derived, none of them is accurate for the whole physiological range of blood vessels radii and blood oxygenation levels. We also show the extent of systematic errors that are introduced due to the approximations of these models when used for BOLD signal quantification.

17 CFR 270.8b-12 - Requirements as to paper, printing and language.

Code of Federal Regulations, 2010 CFR

2010-04-01

... and font, bold-face type, italics and red ink, by presenting all required information in a format... and other tabular data included therein shall be in roman type at least as large as 10-point modern type. However, to the extent necessary for convenient presentation, financial statements and other...

Assistance Services for the Elderly. Reference Book and Student Activity Book.

ERIC Educational Resources Information Center

Texas Tech Univ., Lubbock. Home Economics Curriculum Center.

These coordinated components focus on the career cluster of assistance services for the elderly. The reference book 1987 provide information needed by employees. Each chapter begins with competencies to develop and objectives to achieve. Within the text, bold-faced vocabulary terms are defined. Each chapter concludes with a content summary in the…

Analysis of short single rest/activation epoch fMRI by self-organizing map neural network

NASA Astrophysics Data System (ADS)

Erberich, Stephan G.; Dietrich, Thomas; Kemeny, Stefan; Krings, Timo; Willmes, Klaus; Thron, Armin; Oberschelp, Walter

2000-04-01

Functional magnet resonance imaging (fMRI) has become a standard non invasive brain imaging technique delivering high spatial resolution. Brain activation is determined by magnetic susceptibility of the blood oxygen level (BOLD effect) during an activation task, e.g. motor, auditory and visual tasks. Usually box-car paradigms have 2 - 4 rest/activation epochs with at least an overall of 50 volumes per scan in the time domain. Statistical test based analysis methods need a large amount of repetitively acquired brain volumes to gain statistical power, like Student's t-test. The introduced technique based on a self-organizing neural network (SOM) makes use of the intrinsic features of the condition change between rest and activation epoch and demonstrated to differentiate between the conditions with less time points having only one rest and one activation epoch. The method reduces scan and analysis time and the probability of possible motion artifacts from the relaxation of the patients head. Functional magnet resonance imaging (fMRI) of patients for pre-surgical evaluation and volunteers were acquired with motor (hand clenching and finger tapping), sensory (ice application), auditory (phonological and semantic word recognition task) and visual paradigms (mental rotation). For imaging we used different BOLD contrast sensitive Gradient Echo Planar Imaging (GE-EPI) single-shot pulse sequences (TR 2000 and 4000, 64 X 64 and 128 X 128, 15 - 40 slices) on a Philips Gyroscan NT 1.5 Tesla MR imager. All paradigms were RARARA (R equals rest, A equals activation) with an epoch width of 11 time points each. We used the self-organizing neural network implementation described by T. Kohonen with a 4 X 2 2D neuron map. The presented time course vectors were clustered by similar features in the 2D neuron map. Three neural networks were trained and used for labeling with the time course vectors of one, two and all three on/off epochs. The results were also compared by using a Kolmogorov-Smirnov statistical test of all 66 time points. To remove non- periodical time courses from training an auto-correlation function and bandwidth limiting Fourier filtering in combination with Gauss temporal smoothing was used. None of the trained maps, with one, two and three epochs, were significantly different which indicates that the feature space of only one on/off epoch is sufficient to differentiate between the rest and task condition. We found, that without pre-processing of the data no meaningful results can be achieved because of the huge amount of the non-activated and background voxels represents the majority of the features and is therefore learned by the SOM. Thus it is crucial to remove unnecessary capacity load of the neural network by selection of the training input, using auto-correlation function and/or Fourier spectrum analysis. However by reducing the time points to one rest and one activation epoch either strong auto- correlation or a precise periodical frequency is vanishing. Self-organizing maps can be used to separate rest and activation epochs of with only a 1/3 of the usually acquired time points. Because of the nature of the SOM technique, the pattern or feature separation, only the presence of a state change between the conditions is necessary for differentiation. Also the variance of the individual hemodynamic response function (HRF) and the variance of the spatial different regional cerebral blood flow (rCBF) is learned from the subject and not compared with a fixed model done by statistical evaluation. We found that reducing the information to only a few time points around the BOLD effect was not successful due to delays of rCBF and the insufficient extension of the BOLD feature in the time space. Especially for patient routine observation and pre-surgical planing a reduced scan time is of interest.

When BOLD is thicker than water: processing social information about kin and friends at different levels of the social network.

PubMed

Wlodarski, Rafael; Dunbar, Robin I M

2016-12-01

The aim of this study was to examine differences in the neural processing of social information about kin and friends at different levels of closeness and social network level. Twenty-five female participants engaged in a cognitive social task involving different individuals in their social network while undergoing functional magnetic resonance imaging scanning to detect BOLD (Blood Oxygen Level Dependent) signals changes. Greater levels of activation occurred in several regions of the brain previously associated with social cognition when thinking about friends than when thinking about kin, including the posterior cingulate cortex (PCC) and the ventral medial prefrontal cortex (vMPFC). Linear parametric analyses across network layers further showed that, when it came to thinking about friends, activation increased in the vMPFC, lingual gyrus, and sensorimotor cortex as individuals thought about friends at closer layers of the network. These findings suggest that maintaining friendships may be more cognitively exacting than maintaining kin relationships. © The Author (2016). Published by Oxford University Press. For Permissions, please email: journals.permissions@oup.com.

The effect of feature-based attention on flanker interference processing: An fMRI-constrained source analysis.

PubMed

Siemann, Julia; Herrmann, Manfred; Galashan, Daniela

2018-01-25

The present study examined whether feature-based cueing affects early or late stages of flanker conflict processing using EEG and fMRI. Feature cues either directed participants' attention to the upcoming colour of the target or were neutral. Validity-specific modulations during interference processing were investigated using the N200 event-related potential (ERP) component and BOLD signal differences. Additionally, both data sets were integrated using an fMRI-constrained source analysis. Finally, the results were compared with a previous study in which spatial instead of feature-based cueing was applied to an otherwise identical flanker task. Feature-based and spatial attention recruited a common fronto-parietal network during conflict processing. Irrespective of attention type (feature-based; spatial), this network responded to focussed attention (valid cueing) as well as context updating (invalid cueing), hinting at domain-general mechanisms. However, spatially and non-spatially directed attention also demonstrated domain-specific activation patterns for conflict processing that were observable in distinct EEG and fMRI data patterns as well as in the respective source analyses. Conflict-specific activity in visual brain regions was comparable between both attention types. We assume that the distinction between spatially and non-spatially directed attention types primarily applies to temporal differences (domain-specific dynamics) between signals originating in the same brain regions (domain-general localization).

Cortex-based inter-subject analysis of iEEG and fMRI data sets: application to sustained task-related BOLD and gamma responses.

PubMed

Esposito, Fabrizio; Singer, Neomi; Podlipsky, Ilana; Fried, Itzhak; Hendler, Talma; Goebel, Rainer

2013-02-01

Linking regional metabolic changes with fluctuations in the local electromagnetic fields directly on the surface of the human cerebral cortex is of tremendous importance for a better understanding of detailed brain processes. Functional magnetic resonance imaging (fMRI) and intra-cranial electro-encephalography (iEEG) measure two technically unrelated but spatially and temporally complementary sets of functional descriptions of human brain activity. In order to allow fine-grained spatio-temporal human brain mapping at the population-level, an effective comparative framework for the cortex-based inter-subject analysis of iEEG and fMRI data sets is needed. We combined fMRI and iEEG recordings of the same patients with epilepsy during alternated intervals of passive movie viewing and music listening to explore the degree of local spatial correspondence and temporal coupling between blood oxygen level dependent (BOLD) fMRI changes and iEEG spectral power modulations across the cortical surface after cortex-based inter-subject alignment. To this purpose, we applied a simple model of the iEEG activity spread around each electrode location and the cortex-based inter-subject alignment procedure to transform discrete iEEG measurements into cortically distributed group patterns by establishing a fine anatomic correspondence of many iEEG cortical sites across multiple subjects. Our results demonstrate the feasibility of a multi-modal inter-subject cortex-based distributed analysis for combining iEEG and fMRI data sets acquired from multiple subjects with the same experimental paradigm but with different iEEG electrode coverage. The proposed iEEG-fMRI framework allows for improved group statistics in a common anatomical space and preserves the dynamic link between the temporal features of the two modalities. Copyright © 2012 Elsevier Inc. All rights reserved.

Voxel-wise motion artifacts in population-level whole-brain connectivity analysis of resting-state FMRI.

PubMed

Spisák, Tamás; Jakab, András; Kis, Sándor A; Opposits, Gábor; Aranyi, Csaba; Berényi, Ervin; Emri, Miklós

2014-01-01

Functional Magnetic Resonance Imaging (fMRI) based brain connectivity analysis maps the functional networks of the brain by estimating the degree of synchronous neuronal activity between brain regions. Recent studies have demonstrated that "resting-state" fMRI-based brain connectivity conclusions may be erroneous when motion artifacts have a differential effect on fMRI BOLD signals for between group comparisons. A potential explanation could be that in-scanner displacement, due to rotational components, is not spatially constant in the whole brain. However, this localized nature of motion artifacts is poorly understood and is rarely considered in brain connectivity studies. In this study, we initially demonstrate the local correspondence between head displacement and the changes in the resting-state fMRI BOLD signal. Than, we investigate how connectivity strength is affected by the population-level variation in the spatial pattern of regional displacement. We introduce Regional Displacement Interaction (RDI), a new covariate parameter set for second-level connectivity analysis and demonstrate its effectiveness in reducing motion related confounds in comparisons of groups with different voxel-vise displacement pattern and preprocessed using various nuisance regression methods. The effect of using RDI as second-level covariate is than demonstrated in autism-related group comparisons. The relationship between the proposed method and some of the prevailing subject-level nuisance regression techniques is evaluated. Our results show that, depending on experimental design, treating in-scanner head motion as a global confound may not be appropriate. The degree of displacement is highly variable among various brain regions, both within and between subjects. These regional differences bias correlation-based measures of brain connectivity. The inclusion of the proposed second-level covariate into the analysis successfully reduces artifactual motion-related group differences and preserves real neuronal differences, as demonstrated by the autism-related comparisons.

Cortex-wide BOLD fMRI activity reflects locally-recorded slow oscillation-associated calcium waves.

PubMed

Schwalm, Miriam; Schmid, Florian; Wachsmuth, Lydia; Backhaus, Hendrik; Kronfeld, Andrea; Aedo Jury, Felipe; Prouvot, Pierre-Hugues; Fois, Consuelo; Albers, Franziska; van Alst, Timo; Faber, Cornelius; Stroh, Albrecht

2017-09-15

Spontaneous slow oscillation-associated slow wave activity represents an internally generated state which is characterized by alternations of network quiescence and stereotypical episodes of neuronal activity - slow wave events. However, it remains unclear which macroscopic signal is related to these active periods of the slow wave rhythm. We used optic fiber-based calcium recordings of local neural populations in cortex and thalamus to detect neurophysiologically defined slow calcium waves in isoflurane anesthetized rats. The individual slow wave events were used for an event-related analysis of simultaneously acquired whole-brain BOLD fMRI. We identified BOLD responses directly related to onsets of slow calcium waves, revealing a cortex-wide BOLD correlate: the entire cortex was engaged in this specific type of slow wave activity. These findings demonstrate a direct relation of defined neurophysiological events to a specific BOLD activity pattern and were confirmed for ongoing slow wave activity by independent component and seed-based analyses.

Negative BOLD response and serotonin concentration within rostral subgenual portion of the anterior cingulate cortex for long-allele carriers during perceptual processing of emotional tasks

NASA Astrophysics Data System (ADS)

Hadi, Shamil M.; Siadat, Mohamad R.; Babajani-Feremi, Abbas

2012-03-01

We investigated the effect of synaptic serotonin concentration on hemodynamic responses. The stimuli paradigm involved the presentation of fearful and threatening facial expressions to a set of 24 subjects who were either5HTTLPR long- or short-allele carriers (12 of each type in each group). The BOLD signals of the rACC from subjects of each group were averaged to increase the signal-to-noise ratio. We used a Bayesian approach to estimate the parameters of the underlying hemodynamic model. Our results, during this perceptual processing of emotional task, showed a negative BOLD signal in the rACC in the subjects with long-alleles. In contrast, the subjects with short-alleles showed positive BOLD signals in the rACC. These results suggest that high synaptic serotonin concentration in the rACC inhibits neuronal activity in a fashion similar to GABA, and a consequent negative BOLD signal ensues.

Comparison between subjects with long- and short-allele carriers in the BOLD signal within amygdala during emotional tasks

NASA Astrophysics Data System (ADS)

Hadi, Shamil; Siadat, Mohamad R.; Babajani-Feremi, Abbas

2012-03-01

Emotional tasks may result in a strong blood oxygen level-dependent (BOLD) signal in the amygdala in 5- HTTLRP short-allele. Reduced anterior cingulate cortex (ACC)-amygdala connectivity in short-allele provides a potential mechanistic account for the observed increase in amygdala activity. In our study, fearful and threatening facial expressions were presented to two groups of 12 subjects with long- and short-allele carriers. The BOLD signals of the left amygdala of each group were averaged to increase the signal-to-noise ratio. A Bayesian approach was used to estimate the model parameters to elucidate the underlying hemodynamic mechanism. Our results showed a positive BOLD signal in the left amygdala for short-allele individuals, and a negative BOLD signal in the same region for long-allele individuals. This is due to the fact that short-allele is associated with lower availability of serotonin transporter (5-HTT) and this leads to an increase of serotonin (5-HT) concentration in the cACC-amygdala synapse.

Task-evoked BOLD responses are normal in areas of diaschisis after stroke.

PubMed

Fair, Damien A; Snyder, Abraham Z; Connor, Lisa Tabor; Nardos, Binyam; Corbetta, Maurizio

2009-01-01

Cerebral infarction can cause diaschisis, a reduction of blood flow and metabolism in areas of the cortex distant from the site of the lesion. Although the functional magnetic resonance imaging (fMRI) blood oxygen level dependent (BOLD) signal is increasingly used to examine the neural correlates of recovery in stroke, its reliability in areas of diaschisis is uncertain. The effect of chronic diaschisis as measured by resting positron emission tomography on task-evoked BOLD responses during word-stem completion in a block design fMRI study was examined in 3 patients, 6 months after a single left hemisphere stroke involving the inferior frontal gyrus and operculum. The BOLD responses were minimally affected in areas of chronic diaschisis. Within the confines of this study, the mechanism underlying the BOLD signal, which includes a mismatch between neuronally driven increases in blood flow and a corresponding increase in oxygen use, appears to be intact in areas of chronic diaschisis.

To boldly go: individual differences in boldness influence migratory tendency.

PubMed

Chapman, Ben B; Hulthén, Kaj; Blomqvist, David R; Hansson, Lars-Anders; Nilsson, Jan-Åke; Brodersen, Jakob; Anders Nilsson, P; Skov, Christian; Brönmark, Christer

2011-09-01

Partial migration, whereby only a fraction of the population migrates, is thought to be the most common type of migration in the animal kingdom, and can have important ecological and evolutionary consequences. Despite this, the factors that influence which individuals migrate and which remain resident are poorly understood. Recent work has shown that consistent individual differences in personality traits in animals can be ecologically important, but field studies integrating personality traits with migratory behaviour are extremely rare. In this study, we investigate the influence of individual boldness, an important personality trait, upon the migratory propensity of roach, a freshwater fish, over two consecutive migration seasons. We assay and individually tag 460 roach and show that boldness influences migratory propensity, with bold individuals being more likely to migrate than shy fish. Our data suggest that an extremely widespread personality trait in animals can have significant ecological consequences via influencing individual-level migratory behaviour. © 2011 Blackwell Publishing Ltd/CNRS.

Interactions between aggression, boldness and shoaling within a brood of convict cichlids (Amatitlania nigrofasciatus).

PubMed

Moss, Sarah; Tittaferrante, Stephanie; Way, Gregory P; Fuller, Ashlei; Sullivan, Nicole; Ruhl, Nathan; McRobert, Scott P

2015-12-01

A behavioral syndrome is considered present when individuals consistently express correlated behaviors across two or more axes of behavior. These axes of behavior are shy-bold, exploration-avoidance, activity, aggression, and sociability. In this study we examined aggression, boldness and sociability (shoaling) within a juvenile convict cichlid brood (Amatitlania nigrofasciatus). Because young convict cichlids are social, we used methodologies commonly used by ethologists studying social fishes. We did not detect an aggression-boldness behavioral syndrome, but we did find that the aggression, boldness, and possibly the exploration behavioral axes play significant roles in shaping the observed variation in individual convict cichlid behavior. While juvenile convict cichlids did express a shoaling preference, this social preference was likely convoluted by aggressive interactions, despite the small size and young age of the fish. There is a need for the development of behavioral assays that allow for more reliable measurement of behavioral axes in juvenile neo-tropical cichlids. Copyright © 2015 Elsevier B.V. All rights reserved.

Cortex-wide BOLD fMRI activity reflects locally-recorded slow oscillation-associated calcium waves

PubMed Central

Backhaus, Hendrik; Kronfeld, Andrea; Aedo Jury, Felipe; Prouvot, Pierre-Hugues; Fois, Consuelo; Albers, Franziska; van Alst, Timo

2017-01-01

Spontaneous slow oscillation-associated slow wave activity represents an internally generated state which is characterized by alternations of network quiescence and stereotypical episodes of neuronal activity - slow wave events. However, it remains unclear which macroscopic signal is related to these active periods of the slow wave rhythm. We used optic fiber-based calcium recordings of local neural populations in cortex and thalamus to detect neurophysiologically defined slow calcium waves in isoflurane anesthetized rats. The individual slow wave events were used for an event-related analysis of simultaneously acquired whole-brain BOLD fMRI. We identified BOLD responses directly related to onsets of slow calcium waves, revealing a cortex-wide BOLD correlate: the entire cortex was engaged in this specific type of slow wave activity. These findings demonstrate a direct relation of defined neurophysiological events to a specific BOLD activity pattern and were confirmed for ongoing slow wave activity by independent component and seed-based analyses. PMID:28914607

Triarchic Model Personality Traits and Their Impact on Mock Juror Perceptions of a White-Collar Criminal Defendant.

PubMed

Rulseh, Allison; Edens, John F; Cox, Jennifer

2017-01-01

The triarchic model of psychopathy proposes that this personality disorder is composed of 3 relatively distinct constructs: meanness, disinhibition, and boldness. Although the first 2 components are widely accepted, boldness has generated considerable theoretical debate concerning its relevance-largely due to its association with various ostensibly adaptive characteristics and socially desirable behaviors (e.g., self-reported heroism). But is being bold actually perceived by others as an intrinsically adaptive, socially desirable personality trait? We investigated this question using a novel approach-a jury simulation study that manipulated the level of triarchic traits exhibited by a white-collar criminal. More specifically, 330 community members read a vignette in which the defendant's degree of boldness and disinhibition was manipulated and then provided sentence recommendations and other evaluative ratings. As hypothesized, manipulating boldness and disinhibition resulted in more negative views of the defendant, with the boldness manipulation more consistently predicting higher global psychopathy, "meanness," and "evil" ratings. Surprisingly, neither manipulation predicted sentence recommendations, although higher global psychopathy ratings did correlate with more punitive sentence recommendations. The presence of personality traits construed in some contexts as advantageous or socially desirable can be perceived as more dysfunctional and undesirable in other contexts-particularly when they cooccur with criminal behavior.

Infraslow Electroencephalographic and Dynamic Resting State Network Activity.

PubMed

Grooms, Joshua K; Thompson, Garth J; Pan, Wen-Ju; Billings, Jacob; Schumacher, Eric H; Epstein, Charles M; Keilholz, Shella D

2017-06-01

A number of studies have linked the blood oxygenation level dependent (BOLD) signal to electroencephalographic (EEG) signals in traditional frequency bands (δ, θ, α, β, and γ), but the relationship between BOLD and its direct frequency correlates in the infraslow band (<1 Hz) has been little studied. Previously, work in rodents showed that infraslow local field potentials play a role in functional connectivity, particularly in the dynamic organization of large-scale networks. To examine the relationship between infraslow activity and network dynamics in humans, direct current (DC) EEG and resting state magnetic resonance imaging data were acquired simultaneously. The DC EEG signals were correlated with the BOLD signal in patterns that resembled resting state networks. Subsequent dynamic analysis showed that the correlation between DC EEG and the BOLD signal varied substantially over time, even within individual subjects. The variation in DC EEG appears to reflect the time-varying contribution of different resting state networks. Furthermore, some of the patterns of DC EEG and BOLD correlation are consistent with previous work demonstrating quasiperiodic spatiotemporal patterns of large-scale network activity in resting state. These findings demonstrate that infraslow electrical activity is linked to BOLD fluctuations in humans and that it may provide a basis for large-scale organization comparable to that observed in animal studies.

Infraslow Electroencephalographic and Dynamic Resting State Network Activity

PubMed Central

Grooms, Joshua K.; Thompson, Garth J.; Pan, Wen-Ju; Billings, Jacob; Schumacher, Eric H.; Epstein, Charles M.

2017-01-01

Abstract A number of studies have linked the blood oxygenation level dependent (BOLD) signal to electroencephalographic (EEG) signals in traditional frequency bands (δ, θ, α, β, and γ), but the relationship between BOLD and its direct frequency correlates in the infraslow band (<1 Hz) has been little studied. Previously, work in rodents showed that infraslow local field potentials play a role in functional connectivity, particularly in the dynamic organization of large-scale networks. To examine the relationship between infraslow activity and network dynamics in humans, direct current (DC) EEG and resting state magnetic resonance imaging data were acquired simultaneously. The DC EEG signals were correlated with the BOLD signal in patterns that resembled resting state networks. Subsequent dynamic analysis showed that the correlation between DC EEG and the BOLD signal varied substantially over time, even within individual subjects. The variation in DC EEG appears to reflect the time-varying contribution of different resting state networks. Furthermore, some of the patterns of DC EEG and BOLD correlation are consistent with previous work demonstrating quasiperiodic spatiotemporal patterns of large-scale network activity in resting state. These findings demonstrate that infraslow electrical activity is linked to BOLD fluctuations in humans and that it may provide a basis for large-scale organization comparable to that observed in animal studies. PMID:28462586

Are personality differences in a small iteroparous mammal maintained by a life-history trade-off?

PubMed Central

Dammhahn, Melanie

2012-01-01

Despite increasing interest, animal personality is still a puzzling phenomenon. Several theoretical models have been proposed to explain intraindividual consistency and interindividual variation in behaviour, which have been primarily supported by qualitative data and simulations. Using an empirical approach, I tested predictions of one main life-history hypothesis, which posits that consistent individual differences in behaviour are favoured by a trade-off between current and future reproduction. Data on life-history were collected for individuals of a natural population of grey mouse lemurs (Microcebus murinus). Using open-field and novel-object tests, I quantified variation in activity, exploration and boldness for 117 individuals over 3 years. I found systematic variation in boldness between individuals of different residual reproductive value. Young males with low current but high expected future fitness were less bold than older males with high current fecundity, and males might increase in boldness with age. Females have low variation in assets and in boldness with age. Body condition was not related to boldness and only explained marginal variation in exploration. Overall, these data indicate that a trade-off between current and future reproduction might maintain personality variation in mouse lemurs, and thus provide empirical support of this life-history trade-off hypothesis. PMID:22398164

fMR-adaptation indicates selectivity to audiovisual content congruency in distributed clusters in human superior temporal cortex.

PubMed

van Atteveldt, Nienke M; Blau, Vera C; Blomert, Leo; Goebel, Rainer

2010-02-02

Efficient multisensory integration is of vital importance for adequate interaction with the environment. In addition to basic binding cues like temporal and spatial coherence, meaningful multisensory information is also bound together by content-based associations. Many functional Magnetic Resonance Imaging (fMRI) studies propose the (posterior) superior temporal cortex (STC) as the key structure for integrating meaningful multisensory information. However, a still unanswered question is how superior temporal cortex encodes content-based associations, especially in light of inconsistent results from studies comparing brain activation to semantically matching (congruent) versus nonmatching (incongruent) multisensory inputs. Here, we used fMR-adaptation (fMR-A) in order to circumvent potential problems with standard fMRI approaches, including spatial averaging and amplitude saturation confounds. We presented repetitions of audiovisual stimuli (letter-speech sound pairs) and manipulated the associative relation between the auditory and visual inputs (congruent/incongruent pairs). We predicted that if multisensory neuronal populations exist in STC and encode audiovisual content relatedness, adaptation should be affected by the manipulated audiovisual relation. The results revealed an occipital-temporal network that adapted independently of the audiovisual relation. Interestingly, several smaller clusters distributed over superior temporal cortex within that network, adapted stronger to congruent than to incongruent audiovisual repetitions, indicating sensitivity to content congruency. These results suggest that the revealed clusters contain multisensory neuronal populations that encode content relatedness by selectively responding to congruent audiovisual inputs, since unisensory neuronal populations are assumed to be insensitive to the audiovisual relation. These findings extend our previously revealed mechanism for the integration of letters and speech sounds and demonstrate that fMR-A is sensitive to multisensory congruency effects that may not be revealed in BOLD amplitude per se.

Comparison of fMRI analysis methods for heterogeneous BOLD responses in block design studies

PubMed Central

Bernal-Casas, David; Fang, Zhongnan; Lee, Jin Hyung

2017-01-01

A large number of fMRI studies have shown that the temporal dynamics of evoked BOLD responses can be highly heterogeneous. Failing to model heterogeneous responses in statistical analysis can lead to significant errors in signal detection and characterization and alter the neurobiological interpretation. However, to date it is not clear that, out of a large number of options, which methods are robust against variability in the temporal dynamics of BOLD responses in block-design studies. Here, we used rodent optogenetic fMRI data with heterogeneous BOLD responses and simulations guided by experimental data as a means to investigate different analysis methods’ performance against heterogeneous BOLD responses. Evaluations are carried out within the general linear model (GLM) framework and consist of standard basis sets as well as independent component analysis (ICA). Analyses show that, in the presence of heterogeneous BOLD responses, conventionally used GLM with a canonical basis set leads to considerable errors in the detection and characterization of BOLD responses. Our results suggest that the 3rd and 4th order gamma basis sets, the 7th to 9th order finite impulse response (FIR) basis sets, the 5th to 9th order B-spline basis sets, and the 2nd to 5th order Fourier basis sets are optimal for good balance between detection and characterization, while the 1st order Fourier basis set (coherence analysis) used in our earlier studies show good detection capability. ICA has mostly good detection and characterization capabilities, but detects a large volume of spurious activation with the control fMRI data. PMID:27993672

Paced respiration with end-expiration technique offers superior BOLD signal repeatability for breath-hold studies.

PubMed

Scouten, A; Schwarzbauer, C

2008-11-01

As a simple, non-invasive method of blood oxygenation level-dependent (BOLD) signal calibration, the breath-hold task offers considerable potential for the quantification of neuronal activity from functional magnetic resonance imaging (fMRI) measurements. With an aim to improve the precision of this calibration method, the impact of respiratory rate control on the BOLD signal achieved with the breath-hold task was investigated. In addition to self-paced breathing, three different computer-paced breathing rates were imposed during the periods between end-expiration breath-hold blocks. The resulting BOLD signal timecourses and statistical activation maps were compared in eleven healthy human subjects. Results indicate that computer-paced respiration produces a larger peak BOLD signal increase with breath-hold than self-paced breathing, in addition to lower variability between trials. This is due to the more significant post-breath-hold signal undershoot present in self-paced runs, a characteristic which confounds the definition of baseline and is difficult to accurately model. Interestingly, the specific respiratory rate imposed between breath-hold periods generally does not have a statistically significant impact on the BOLD signal change. This result can be explained by previous reports of humans adjusting their inhalation depth to compensate for changes in rate, with the end-goal of maintaining homeostatic ventilation. The advantage of using end-expiration relative to end-inspiration breath-hold is apparent in view of the high repeatability of the BOLD signal in the present study, which does not suffer from the previously reported high variability associated with uncontrolled inspiration depth when using the end-inspiration technique.

Cerebral Blood Flow and BOLD Responses to a Memory Encoding Task: A Comparison Between Healthy Young and Elderly Adults

PubMed Central

Restom, Khaled; Bangen, Katherine J.; Bondi, Mark W.; Perthen, Joanna E.; Liu, Thomas T.

2007-01-01

Functional magnetic resonance imaging (fMRI) studies of the medial temporal lobe have primarily made use of the blood oxygenation level dependent (BOLD) response to neural activity. The interpretation of the BOLD signal as a measure of medial temporal lobe function can be complicated, however, by changes in the cerebrovascular system that can occur with both normal aging and age-related diseases, such as Alzheimer's disease. Quantitative measures of the functional cerebral blood flow (CBF) response offer a useful complement to BOLD measures, and have been shown to aid in the interpretation of fMRI studies. Despite these potential advantages, the application of ASL to fMRI studies of cognitive tasks and at-risk populations has been limited. In this study, we demonstrate the application of ASL fMRI to obtain measures of the CBF and BOLD responses to the encoding of natural scenes in healthy young (mean 25 years) and elderly (mean 74 years) adults. The percent CBF increase in the medial temporal lobe was significantly higher in the older adults, whereas the CBF levels during baseline and task conditions and during a separate resting-state scan were significantly lower in the older group. The older adults also showed slightly higher values for the BOLD response amplitude and the absolute change in CBF, but the age group differences were not significant. The percent CBF and BOLD responses are consistent with an age-related increase in the cerebral metabolic rate of oxygen metabolism (CMRO2) response to memory encoding. PMID:17590353

Physiological and genetic correlates of boldness: characterising the mechanisms of behavioural variation in rainbow trout, Oncorhynchus mykiss.

PubMed

Thomson, Jack S; Watts, Phillip C; Pottinger, Tom G; Sneddon, Lynne U

2011-01-01

Bold, risk-taking animals have previously been putatively linked with a proactive stress coping style whereas it is suggested shyer, risk-averse animals exhibit a reactive coping style. The aim of this study was to investigate whether differences in the expression of bold-type behaviour were evident within and between two lines of rainbow trout, Oncorhynchus mykiss, selectively bred for a low (LR) or high (HR) endocrine response to stress, and to link boldness and stress responsiveness with the expression of related candidate genes. Boldness was determined in individual fish over two trials by measuring the latency to approach a novel object. Differences in plasma cortisol concentrations and the expression of eight novel candidate genes previously identified as being linked with divergent behaviours or stress were determined. Bold and shy individuals, approaching the object within 180 s or not approaching within 300 s respectively, were evident within each line, and this was linked with activity levels in the HR line. Post-stress plasma cortisol concentrations were significantly greater in the HR line compared with the LR line, and six of the eight tested genes were upregulated in the brains of LR fish compared with HR fish. However, no direct relationship between boldness and either stress responsiveness or gene expression was found, although clear differences in stress physiology and, for the first time, gene expression could be identified between the lines. This lack of correlation between physiological and molecular responses and behavioural variation within both lines highlights the complexity of the behavioural-physiological complex. Copyright © 2010 Elsevier Inc. All rights reserved.

Negative BOLD in sensory cortices during verbal memory: a component in generating internal representations?

PubMed

Azulay, Haim; Striem, Ella; Amedi, Amir

2009-05-01

People tend to close their eyes when trying to retrieve an event or a visual image from memory. However the brain mechanisms behind this phenomenon remain poorly understood. Recently, we showed that during visual mental imagery, auditory areas show a much more robust deactivation than during visual perception. Here we ask whether this is a special case of a more general phenomenon involving retrieval of intrinsic, internally stored information, which would result in crossmodal deactivations in other sensory cortices which are irrelevant to the task at hand. To test this hypothesis, a group of 9 sighted individuals were scanned while performing a memory retrieval task for highly abstract words (i.e., with low imaginability scores). We also scanned a group of 10 congenitally blind, which by definition do not have any visual imagery per se. In sighted subjects, both auditory and visual areas were robustly deactivated during memory retrieval, whereas in the blind the auditory cortex was deactivated while visual areas, shown previously to be relevant for this task, presented a positive BOLD signal. These results suggest that deactivation may be most prominent in task-irrelevant sensory cortices whenever there is a need for retrieval or manipulation of internally stored representations. Thus, there is a task-dependent balance of activation and deactivation that might allow maximization of resources and filtering out of non relevant information to enable allocation of attention to the required task. Furthermore, these results suggest that the balance between positive and negative BOLD might be crucial to our understanding of a large variety of intrinsic and extrinsic tasks including high-level cognitive functions, sensory processing and multisensory integration.

Causality within the Epileptic Network: An EEG-fMRI Study Validated by Intracranial EEG.

PubMed

Vaudano, Anna Elisabetta; Avanzini, Pietro; Tassi, Laura; Ruggieri, Andrea; Cantalupo, Gaetano; Benuzzi, Francesca; Nichelli, Paolo; Lemieux, Louis; Meletti, Stefano

2013-01-01

Accurate localization of the Seizure Onset Zone (SOZ) is crucial in patients with drug-resistance focal epilepsy. EEG with fMRI recording (EEG-fMRI) has been proposed as a complementary non-invasive tool, which can give useful additional information in the pre-surgical work-up. However, fMRI maps related to interictal epileptiform activities (IED) often show multiple regions of signal change, or "networks," rather than highly focal ones. Effective connectivity approaches like Dynamic Causal Modeling (DCM) applied to fMRI data potentially offers a framework to address which brain regions drives the generation of seizures and IED within an epileptic network. Here, we present a first attempt to validate DCM on EEG-fMRI data in one patient affected by frontal lobe epilepsy. Pre-surgical EEG-fMRI demonstrated two distinct clusters of blood oxygenation level dependent (BOLD) signal increases linked to IED, one located in the left frontal pole and the other in the ipsilateral dorso-lateral frontal cortex. DCM of the IED-related BOLD signal favored a model corresponding to the left dorso-lateral frontal cortex as driver of changes in the fronto-polar region. The validity of DCM was supported by: (a) the results of two different non-invasive analysis obtained on the same dataset: EEG source imaging (ESI), and "psycho-physiological interaction" analysis; (b) the failure of a first surgical intervention limited to the fronto-polar region; (c) the results of the intracranial EEG monitoring performed after the first surgical intervention confirming a SOZ located over the dorso-lateral frontal cortex. These results add evidence that EEG-fMRI together with advanced methods of BOLD signal analysis is a promising tool that can give relevant information within the epilepsy surgery diagnostic work-up.

Relating resting-state fMRI and EEG whole-brain connectomes across frequency bands.

PubMed

Deligianni, Fani; Centeno, Maria; Carmichael, David W; Clayden, Jonathan D

2014-01-01

Whole brain functional connectomes hold promise for understanding human brain activity across a range of cognitive, developmental and pathological states. So called resting-state (rs) functional MRI studies have contributed to the brain being considered at a macroscopic scale as a set of interacting regions. Interactions are defined as correlation-based signal measurements driven by blood oxygenation level dependent (BOLD) contrast. Understanding the neurophysiological basis of these measurements is important in conveying useful information about brain function. Local coupling between BOLD fMRI and neurophysiological measurements is relatively well defined, with evidence that gamma (range) frequency EEG signals are the closest correlate of BOLD fMRI changes during cognitive processing. However, it is less clear how whole-brain network interactions relate during rest where lower frequency signals have been suggested to play a key role. Simultaneous EEG-fMRI offers the opportunity to observe brain network dynamics with high spatio-temporal resolution. We utilize these measurements to compare the connectomes derived from rs-fMRI and EEG band limited power (BLP). Merging this multi-modal information requires the development of an appropriate statistical framework. We relate the covariance matrices of the Hilbert envelope of the source localized EEG signal across bands to the covariance matrices derived from rs-fMRI with the means of statistical prediction based on sparse Canonical Correlation Analysis (sCCA). Subsequently, we identify the most prominent connections that contribute to this relationship. We compare whole-brain functional connectomes based on their geodesic distance to reliably estimate the performance of the prediction. The performance of predicting fMRI from EEG connectomes is considerably better than predicting EEG from fMRI across all bands, whereas the connectomes derived in low frequency EEG bands resemble best rs-fMRI connectivity.

Relating resting-state fMRI and EEG whole-brain connectomes across frequency bands

PubMed Central

Deligianni, Fani; Centeno, Maria; Carmichael, David W.; Clayden, Jonathan D.

2014-01-01

Whole brain functional connectomes hold promise for understanding human brain activity across a range of cognitive, developmental and pathological states. So called resting-state (rs) functional MRI studies have contributed to the brain being considered at a macroscopic scale as a set of interacting regions. Interactions are defined as correlation-based signal measurements driven by blood oxygenation level dependent (BOLD) contrast. Understanding the neurophysiological basis of these measurements is important in conveying useful information about brain function. Local coupling between BOLD fMRI and neurophysiological measurements is relatively well defined, with evidence that gamma (range) frequency EEG signals are the closest correlate of BOLD fMRI changes during cognitive processing. However, it is less clear how whole-brain network interactions relate during rest where lower frequency signals have been suggested to play a key role. Simultaneous EEG-fMRI offers the opportunity to observe brain network dynamics with high spatio-temporal resolution. We utilize these measurements to compare the connectomes derived from rs-fMRI and EEG band limited power (BLP). Merging this multi-modal information requires the development of an appropriate statistical framework. We relate the covariance matrices of the Hilbert envelope of the source localized EEG signal across bands to the covariance matrices derived from rs-fMRI with the means of statistical prediction based on sparse Canonical Correlation Analysis (sCCA). Subsequently, we identify the most prominent connections that contribute to this relationship. We compare whole-brain functional connectomes based on their geodesic distance to reliably estimate the performance of the prediction. The performance of predicting fMRI from EEG connectomes is considerably better than predicting EEG from fMRI across all bands, whereas the connectomes derived in low frequency EEG bands resemble best rs-fMRI connectivity. PMID:25221467

Altered amygdalar resting-state connectivity in depression is explained by both genes and environment.

PubMed

Córdova-Palomera, Aldo; Tornador, Cristian; Falcón, Carles; Bargalló, Nuria; Nenadic, Igor; Deco, Gustavo; Fañanás, Lourdes

2015-10-01

Recent findings indicate that alterations of the amygdalar resting-state fMRI connectivity play an important role in the etiology of depression. While both depression and resting-state brain activity are shaped by genes and environment, the relative contribution of genetic and environmental factors mediating the relationship between amygdalar resting-state connectivity and depression remain largely unexplored. Likewise, novel neuroimaging research indicates that different mathematical representations of resting-state fMRI activity patterns are able to embed distinct information relevant to brain health and disease. The present study analyzed the influence of genes and environment on amygdalar resting-state fMRI connectivity, in relation to depression risk. High-resolution resting-state fMRI scans were analyzed to estimate functional connectivity patterns in a sample of 48 twins (24 monozygotic pairs) informative for depressive psychopathology (6 concordant, 8 discordant and 10 healthy control pairs). A graph-theoretical framework was employed to construct brain networks using two methods: (i) the conventional approach of filtered BOLD fMRI time-series and (ii) analytic components of this fMRI activity. Results using both methods indicate that depression risk is increased by environmental factors altering amygdalar connectivity. When analyzing the analytic components of the BOLD fMRI time-series, genetic factors altering the amygdala neural activity at rest show an important contribution to depression risk. Overall, these findings show that both genes and environment modify different patterns the amygdala resting-state connectivity to increase depression risk. The genetic relationship between amygdalar connectivity and depression may be better elicited by examining analytic components of the brain resting-state BOLD fMRI signals. © 2015 Wiley Periodicals, Inc.

Larviculture of a carnivorous freshwater catfish, Lophiosilurus alexandri, screened by personality type.

PubMed

Torres, Isabela F Araújo; Júlio, Gustavo S da C; Figueiredo, Luis Gustavo; de Lima, Natália L C; Soares, Ana Paula N; Luz, Ronald K

2017-12-01

Considering that each personality type in animals presents distinct physiological and behavioural responses, this study evaluated the efficiency of the Novel Environment test to classify larvae of Lophiosilurus alexandri into bold and shy individuals, which were then investigated for growth, cannibalism and mortality in larviculture of pure and mixed groups. Larvae with an average weight of 24.0±1.7mg and length of 14.1±0.4mm, were subjected to a Novel Environment test to classify their personality type (bold and shy larvae). After the larvae were classified according to personality type, they were subjected to larviculture for 15days. Three treatments were tested: only bold larvae, only shy larvae, and a mixed treatment (bold larvae+shy larvae) at a density for 16 larvae/L, which were fed 3 times a day with Artemia nauplii. After larviculture, there were no differences in the final lengths of larvae of the bold, shy, and mixed treatments (26.9±0.76mm, 26.7±1.00mm, and 26.8±1.24mm, respectively); however, shy larvae possessed weighed less (0.22±0.01g) than the bold and mixed treatments, which did not differ significantly (0.25±0.02g and 0.27±0.02g, respectively). The bold and mixed treatments had the highest cannibalism rate (11.2±5.1% and 23.1±12.3%, respectively). Overall survival was lowest in the mixed treatment (62.5±13.0%), while that of the bold and shy treatments were similar (82.5±9.2% and 86.2±9.2%, respectively). The separation of L. alexandri larvae by traits can ensure a decrease in cannibalism and hence, more productive larviculture. Copyright © 2017 Elsevier B.V. All rights reserved.

Prospects for Quantitative fMRI: Investigating the Effects of Caffeine on Baseline Oxygen Metabolism and the Response to a Visual Stimulus in Humans

PubMed Central

Griffeth, Valerie E.M.; Perthen, Joanna E.; Buxton, Richard B.

2011-01-01

Functional magnetic resonance imaging (fMRI) provides an indirect reflection of neural activity change in the working brain through detection of blood oxygenation level dependent (BOLD) signal changes. Although widely used to map patterns of brain activation, fMRI has not yet met its potential for clinical and pharmacological studies due to difficulties in quantitatively interpreting the BOLD signal. This difficulty is due to the BOLD response being strongly modulated by two physiological factors in addition to the level of neural activity: the amount of deoxyhemoglobin present in the baseline state and the coupling ratio, n, of evoked changes in blood flow and oxygen metabolism. In this study, we used a quantitative fMRI approach with dual measurement of blood flow and BOLD responses to overcome these limitations and show that these two sources of modulation work in opposite directions following caffeine administration in healthy human subjects. A strong 27% reduction in baseline blood flow and a 22% increase in baseline oxygen metabolism after caffeine consumption led to a decrease in baseline blood oxygenation and was expected to increase the subsequent BOLD response to the visual stimulus. Opposing this, caffeine reduced n through a strong 61% increase in the evoked oxygen metabolism response to the visual stimulus. The combined effect was that BOLD responses pre- and post-caffeine were similar despite large underlying physiological changes, indicating that the magnitude of the BOLD response alone should not be interpreted as a direct measure of underlying neurophysiological changes. Instead, a quantitative methodology based on dual-echo measurement of blood flow and BOLD responses is a promising tool for applying fMRI to disease and drug studies in which both baseline conditions and the coupling of blood flow and oxygen metabolism responses to a stimulus may be altered. PMID:21586328

Neural and vascular variability and the fMRI-BOLD response in normal aging

PubMed Central

Kannurpatti, Sridhar S.; Motes, Michael A.; Rypma, Bart; Biswal, Bharat B.

2010-01-01

Neural, vascular and structural variables contributing to the BOLD signal response variability were investigated in younger and older humans. Twelve younger healthy human subjects (6M and 6F; mean age: 24 years; range: 19–27 years) and twelve older healthy subjects (5M and 7F; mean age: 58 years; range: 55–71 years) with no history of head trauma and neurological disease were scanned. FMRI measurements using the BOLD contrast were made when participants performed a motor, cognitive or a breath hold task. Activation volume and the BOLD response amplitude were estimated for the younger and older at both group and subject levels. Mean activation volume was reduced by 45, 40 and 38% in the elderly group during the motor, cognitive and breath hold tasks respectively compared to the younger. Reduction in activation volume was substantially higher compared to the reduction in the gray matter volume of 14% in the older compared to the younger. A significantly larger variability in the inter-subject BOLD signal change occurred during the motor task, compared to the cognitive task. BH-induced BOLD signal change between subjects was significantly less-variable in the motor task-activated areas in the younger compared to older whereas such a difference between age groups was not observed during the cognitive task. Hemodynamic scaling using the BH signal substantially reduced the BOLD signal variability during the motor task compared to the cognitive task. The results indicate that the origin of the BOLD signal variability between subjects was predominantly vascular during the motor task while being principally a consequence of neural variability during the cognitive task. Thus, in addition to gray matter differences, the type of task performed can have different vascular variability weighting that can influence age-related differences in brain functional response. PMID:20117893

Neural and vascular variability and the fMRI-BOLD response in normal aging.

PubMed

Kannurpatti, Sridhar S; Motes, Michael A; Rypma, Bart; Biswal, Bharat B

2010-05-01

Neural, vascular and structural variables contributing to the blood oxygen level-dependent (BOLD) signal response variability were investigated in younger and older humans. Twelve younger healthy human subjects (six male and six female; mean age: 24 years; range: 19-27 years) and 12 older healthy subjects (five male and seven female; mean age: 58 years; range: 55-71 years) with no history of head trauma and neurological disease were scanned. Functional magnetic resonance imaging measurements using the BOLD contrast were made when participants performed a motor, cognitive or a breath hold (BH) task. Activation volume and the BOLD response amplitude were estimated for the younger and older at both group and subject levels. Mean activation volume was reduced by 45%, 40% and 38% in the elderly group during the motor, cognitive and BH tasks, respectively, compared to the younger. Reduction in activation volume was substantially higher compared to the reduction in the gray matter volume of 14% in the older compared to the younger. A significantly larger variability in the intersubject BOLD signal change occurred during the motor task, compared to the cognitive task. BH-induced BOLD signal change between subjects was significantly less-variable in the motor task-activated areas in the younger compared to older whereas such a difference between age groups was not observed during the cognitive task. Hemodynamic scaling using the BH signal substantially reduced the BOLD signal variability during the motor task compared to the cognitive task. The results indicate that the origin of the BOLD signal variability between subjects was predominantly vascular during the motor task while being principally a consequence of neural variability during the cognitive task. Thus, in addition to gray matter differences, the type of task performed can have different vascular variability weighting that can influence age-related differences in brain functional response. 2010 Elsevier Inc. All rights reserved.

CNS BOLD fMRI effects of sham-controlled transcutaneous electrical nerve stimulation in the left outer auditory canal - a pilot study.

PubMed

Kraus, Thomas; Kiess, Olga; Hösl, Katharina; Terekhin, Pavel; Kornhuber, Johannes; Forster, Clemens

2013-09-01

It has recently been shown that electrical stimulation of sensory afferents within the outer auditory canal may facilitate a transcutaneous form of central nervous system stimulation. Functional magnetic resonance imaging (fMRI) blood oxygenation level dependent (BOLD) effects in limbic and temporal structures have been detected in two independent studies. In the present study, we investigated BOLD fMRI effects in response to transcutaneous electrical stimulation of two different zones in the left outer auditory canal. It is hypothesized that different central nervous system (CNS) activation patterns might help to localize and specifically stimulate auricular cutaneous vagal afferents. 16 healthy subjects aged between 20 and 37 years were divided into two groups. 8 subjects were stimulated in the anterior wall, the other 8 persons received transcutaneous vagus nervous stimulation (tVNS) at the posterior side of their left outer auditory canal. For sham control, both groups were also stimulated in an alternating manner on their corresponding ear lobe, which is generally known to be free of cutaneous vagal innervation. Functional MR data from the cortex and brain stem level were collected and a group analysis was performed. In most cortical areas, BOLD changes were in the opposite direction when comparing anterior vs. posterior stimulation of the left auditory canal. The only exception was in the insular cortex, where both stimulation types evoked positive BOLD changes. Prominent decreases of the BOLD signals were detected in the parahippocampal gyrus, posterior cingulate cortex and right thalamus (pulvinar) following anterior stimulation. In subcortical areas at brain stem level, a stronger BOLD decrease as compared with sham stimulation was found in the locus coeruleus and the solitary tract only during stimulation of the anterior part of the auditory canal. The results of the study are in line with previous fMRI studies showing robust BOLD signal decreases in limbic structures and the brain stem during electrical stimulation of the left anterior auditory canal. BOLD signal decreases in the area of the nuclei of the vagus nerve may indicate an effective stimulation of vagal afferences. In contrast, stimulation at the posterior wall seems to lead to unspecific changes of the BOLD signal within the solitary tract, which is a key relay station of vagal neurotransmission. The results of the study show promise for a specific novel method of cranial nerve stimulation and provide a basis for further developments and applications of non-invasive transcutaneous vagus stimulation in psychiatric patients. Copyright © 2013 Elsevier Inc. All rights reserved.

Implications of oxidative stress in the brain plasticity originated by fasting: a BOLD-fMRI study.

PubMed

Belaïch, Rachida; Boujraf, Saïd; Benzagmout, Mohammed; Magoul, Rabia; Maaroufi, Mustapha; Tizniti, Siham

2017-11-01

The goal of this study was assessing the intermittent fasting effect on brain plasticity and oxidative stress (OS) using blood-oxygenation-level dependent (BOLD)-functional magnetic resonance image (fMRI) approach. Evidences of physiological and molecular phenomena involved in this process are discussed and compared to reported literature. Six fully healthy male non-smokers volunteered in this study. All volunteers were right handed, and have an equilibrated, consistent and healthy daily nutritional habit, and a healthy lifestyle. Participants were allowed consuming food during evening and night time while fasting with self-prohibiting food and liquids during 14 hours/day from sunrise to sunset. All participants underwent identical brain BOLD-fMRI protocol. The images were acquired in the Department of Radiology and Clinical Imaging of the University Hospital of Fez, Fez, Morocco. The anatomical brain and BOLD-fMRIs were acquired using a 1.5-Tesla scanner (Signa, General Electric, Milwaukee, United States). BOLD-fMRI image acquisition was done using single-shot gradient echo echo-planer imaging sequence. BOLD-fMRI paradigm consisted of the motor task where volunteers were asked to perform finger taping of the right hand. Two BOLD-fMRI scan sessions were performed, the first one between the 5th and 10th days preceding the start of fasting and the second between days 25th and 28th of the fasting month. All sessions were performed between 3:30 PM and 5:30 PM. Although individual maps were originated from different individual participants, they cover the same anatomic area in each case. Image processing and statistical analysis were conducted with Statistical Parameter Mapping version 8 (2008, Welcome Department of Cognitive Neurology, London UK). The maximal BOLD signal changes were calculated for each subject in the motor area M1; Activation maps were calculated and overlaid on the anatomical images. Group analysis of the data was performed, and the average volume and the maximum intensity of BOLD signal in the activated area M1 was determined for all studied volunteers. The current study allowed measuring regional brain volumes and neural network activity before and during an extended period of fasting using BOLD-fMRI. This demonstrated and confirmed the impact of fasting on human brain structure and function. Further studies are required to elucidate mechanisms and enable direct inference of a diet-induced OS effect on the brain.

Music Listening modulates Functional Connectivity and Information Flow in the Human Brain.

PubMed

Karmonik, Christof; Brandt, Anthony; Anderson, Jeff; Brooks, Forrest; Lytle, Julie; Silverman, Elliott; Frazier, Jeff T

2016-07-27

Listening to familiar music has recently been reported to be beneficial during recovery from stroke. A better understanding of changes in functional connectivity and information flow is warranted in order to further optimize and target this approach through music therapy. Twelve healthy volunteers listened to seven different auditory samples during an fMRI scanning session: a musical piece chosen by the volunteer that evokes a strong emotional response (referred to as: "self-selected emotional"), two unfamiliar music pieces (Invention #1 by J. S. Bach* and Gagaku - Japanese classical opera, referred to as "unfamiliar"), the Bach piece repeated with visual guidance (DML: Directed Music Listening) and three spoken language pieces (unfamiliar African click language, an excerpt of emotionally charged language, and an unemotional reading of a news bulletin). Functional connectivity and betweenness (BTW) maps, a measure for information flow, were created with a graph-theoretical approach. Distinct variation in functional connectivity was found for different music pieces consistently for all subjects. Largest brain areas were recruited for processing self-selected music with emotional attachment or culturally unfamiliar music. Maps of information flow correlated significantly with fMRI BOLD activation maps (p<0.05). Observed differences in BOLD activation and functional connectivity may help explain previously observed beneficial effects in stroke recovery, as increased blood flow to damaged brain areas stimulated by active engagement through music listening may have supported a state more conducive to therapy.

Visual perception of axes of head rotation

PubMed Central

Arnoldussen, D. M.; Goossens, J.; van den Berg, A. V.

2013-01-01

Registration of ego-motion is important to accurately navigate through space. Movements of the head and eye relative to space are registered through the vestibular system and optical flow, respectively. Here, we address three questions concerning the visual registration of self-rotation. (1) Eye-in-head movements provide a link between the motion signals received by sensors in the moving eye and sensors in the moving head. How are these signals combined into an ego-rotation percept? We combined optic flow of simulated forward and rotational motion of the eye with different levels of eye-in-head rotation for a stationary head. We dissociated simulated gaze rotation and head rotation by different levels of eye-in-head pursuit. We found that perceived rotation matches simulated head- not gaze-rotation. This rejects a model for perceived self-rotation that relies on the rotation of the gaze line. Rather, eye-in-head signals serve to transform the optic flow's rotation information, that specifies rotation of the scene relative to the eye, into a rotation relative to the head. This suggests that transformed visual self-rotation signals may combine with vestibular signals. (2) Do transformed visual self-rotation signals reflect the arrangement of the semi-circular canals (SCC)? Previously, we found sub-regions within MST and V6+ that respond to the speed of the simulated head rotation. Here, we re-analyzed those Blood oxygenated level-dependent (BOLD) signals for the presence of a spatial dissociation related to the axes of visually simulated head rotation, such as have been found in sub-cortical regions of various animals. Contrary, we found a rather uniform BOLD response to simulated rotation along the three SCC axes. (3) We investigated if subject's sensitivity to the direction of the head rotation axis shows SCC axes specifcity. We found that sensitivity to head rotation is rather uniformly distributed, suggesting that in human cortex, visuo-vestibular integration is not arranged into the SCC frame. PMID:23919087

Functional Brain Activity Changes after 4 Weeks Supplementation with a Multi-Vitamin/Mineral Combination: A Randomized, Double-Blind, Placebo-Controlled Trial Exploring Functional Magnetic Resonance Imaging and Steady-State Visual Evoked Potentials during Working Memory.

PubMed

White, David J; Cox, Katherine H M; Hughes, Matthew E; Pipingas, Andrew; Peters, Riccarda; Scholey, Andrew B

2016-01-01

This study explored the neurocognitive effects of 4 weeks daily supplementation with a multi-vitamin and -mineral combination (MVM) in healthy adults (aged 18-40 years). Using a randomized, double-blind, placebo-controlled design, participants underwent assessments of brain activity using functional Magnetic Resonance Imaging (fMRI; n = 32, 16 females) and Steady-State Visual Evoked Potential recordings (SSVEP; n = 39, 20 females) during working memory and continuous performance tasks at baseline and following 4 weeks of active MVM treatment or placebo. There were several treatment-related effects suggestive of changes in functional brain activity associated with MVM administration. SSVEP data showed latency reductions across centro-parietal regions during the encoding period of a spatial working memory task following 4 weeks of active MVM treatment. Complementary results were observed with the fMRI data, in which a subset of those completing fMRI assessment after SSVEP assessment ( n = 16) demonstrated increased BOLD response during completion of the Rapid Visual Information Processing task (RVIP) within regions of interest including bilateral parietal lobes. No treatment-related changes in fMRI data were observed in those who had not first undergone SSVEP assessment, suggesting these results may be most evident under conditions of fatigue. Performance on the working memory and continuous performance tasks did not significantly differ between treatment groups at follow-up. In addition, within the fatigued fMRI sample, increased RVIP BOLD response was correlated with the change in number of target detections as part of the RVIP task. This study provides preliminary evidence of changes in functional brain activity during working memory associated with 4 weeks of daily treatment with a multi-vitamin and -mineral combination in healthy adults, using two distinct but complementary measures of functional brain activity.

Functional Brain Activity Changes after 4 Weeks Supplementation with a Multi-Vitamin/Mineral Combination: A Randomized, Double-Blind, Placebo-Controlled Trial Exploring Functional Magnetic Resonance Imaging and Steady-State Visual Evoked Potentials during Working Memory

PubMed Central

White, David J.; Cox, Katherine H. M.; Hughes, Matthew E.; Pipingas, Andrew; Peters, Riccarda; Scholey, Andrew B.

2016-01-01

This study explored the neurocognitive effects of 4 weeks daily supplementation with a multi-vitamin and -mineral combination (MVM) in healthy adults (aged 18–40 years). Using a randomized, double-blind, placebo-controlled design, participants underwent assessments of brain activity using functional Magnetic Resonance Imaging (fMRI; n = 32, 16 females) and Steady-State Visual Evoked Potential recordings (SSVEP; n = 39, 20 females) during working memory and continuous performance tasks at baseline and following 4 weeks of active MVM treatment or placebo. There were several treatment-related effects suggestive of changes in functional brain activity associated with MVM administration. SSVEP data showed latency reductions across centro-parietal regions during the encoding period of a spatial working memory task following 4 weeks of active MVM treatment. Complementary results were observed with the fMRI data, in which a subset of those completing fMRI assessment after SSVEP assessment (n = 16) demonstrated increased BOLD response during completion of the Rapid Visual Information Processing task (RVIP) within regions of interest including bilateral parietal lobes. No treatment-related changes in fMRI data were observed in those who had not first undergone SSVEP assessment, suggesting these results may be most evident under conditions of fatigue. Performance on the working memory and continuous performance tasks did not significantly differ between treatment groups at follow-up. In addition, within the fatigued fMRI sample, increased RVIP BOLD response was correlated with the change in number of target detections as part of the RVIP task. This study provides preliminary evidence of changes in functional brain activity during working memory associated with 4 weeks of daily treatment with a multi-vitamin and -mineral combination in healthy adults, using two distinct but complementary measures of functional brain activity. PMID:27994548

Decoding the Semantic Content of Natural Movies from Human Brain Activity

PubMed Central

Huth, Alexander G.; Lee, Tyler; Nishimoto, Shinji; Bilenko, Natalia Y.; Vu, An T.; Gallant, Jack L.

2016-01-01

One crucial test for any quantitative model of the brain is to show that the model can be used to accurately decode information from evoked brain activity. Several recent neuroimaging studies have decoded the structure or semantic content of static visual images from human brain activity. Here we present a decoding algorithm that makes it possible to decode detailed information about the object and action categories present in natural movies from human brain activity signals measured by functional MRI. Decoding is accomplished using a hierarchical logistic regression (HLR) model that is based on labels that were manually assigned from the WordNet semantic taxonomy. This model makes it possible to simultaneously decode information about both specific and general categories, while respecting the relationships between them. Our results show that we can decode the presence of many object and action categories from averaged blood-oxygen level-dependent (BOLD) responses with a high degree of accuracy (area under the ROC curve > 0.9). Furthermore, we used this framework to test whether semantic relationships defined in the WordNet taxonomy are represented the same way in the human brain. This analysis showed that hierarchical relationships between general categories and atypical examples, such as organism and plant, did not seem to be reflected in representations measured by BOLD fMRI. PMID:27781035

The activity in the anterior insulae is modulated by perceptual decision-making difficulty.

PubMed

Lamichhane, Bidhan; Adhikari, Bhim M; Dhamala, Mukesh

2016-07-07

Previous neuroimaging studies provide evidence for the involvement of the anterior insulae (INSs) in perceptual decision-making processes. However, how the insular cortex is involved in integration of degraded sensory information to create a conscious percept of environment and to drive our behaviors still remains a mystery. In this study, using functional magnetic resonance imaging (fMRI) and four different perceptual categorization tasks in visual and audio-visual domains, we measured blood oxygen level dependent (BOLD) signals and examined the roles of INSs in easy and difficult perceptual decision-making. We created a varying degree of degraded stimuli by manipulating the task-specific stimuli in these four experiments to examine the effects of task difficulty on insular cortex response. We hypothesized that significantly higher BOLD response would be associated with the ambiguity of the sensory information and decision-making difficulty. In all of our experimental tasks, we found the INS activity consistently increased with task difficulty and participants' behavioral performance changed with the ambiguity of the presented sensory information. These findings support the hypothesis that the anterior insulae are involved in sensory-guided, goal-directed behaviors and their activities can predict perceptual load and task difficulty. Copyright © 2016 IBRO. Published by Elsevier Ltd. All rights reserved.

Using Data to Guide State Education Policy and Practice. Issue Brief

ERIC Educational Resources Information Center

NGA Center for Best Practices, 2012

2012-01-01

In fewer than 10 years, states and districts have taken bold steps to build and improve systems that collect data about students, staffing and expenditures, but the data do not often provide adequate information to guide policy and practice. Increasing amounts of data are now available to parents, educators, researchers and policymakers. However,…

17 CFR 230.420 - Legibility of prospectus.

Code of Federal Regulations, 2010 CFR

2010-04-01

... size, type size and font, bold-face type, italics and red ink, by presenting all required information... data included therein shall be in roman type at least as large and as legible as 10-point modern type... rule 482 (17 CFR 230.482) may be in roman type at least as large and as legible as 8-point modern type...

Alabama Education Report Card, 2012-2013: A Year in Review

ERIC Educational Resources Information Center

Alabama State Department of Education, 2014

2014-01-01

Beginning in January of 2012, the Alabama State Board of Education embarked on a bold and transformation plan for K-12 public education known as PLAN 2020. Foundational to this plan was a new definition of a successful and prepared high school graduate informed by community colleges, institutions of higher education, and business and industry,…

bold: The Barcode of Life Data System (http://www.barcodinglife.org)

PubMed Central

RATNASINGHAM, SUJEEVAN; HEBERT, PAUL D N

2007-01-01

The Barcode of Life Data System (bold) is an informatics workbench aiding the acquisition, storage, analysis and publication of DNA barcode records. By assembling molecular, morphological and distributional data, it bridges a traditional bioinformatics chasm. bold is freely available to any researcher with interests in DNA barcoding. By providing specialized services, it aids the assembly of records that meet the standards needed to gain BARCODE designation in the global sequence databases. Because of its web-based delivery and flexible data security model, it is also well positioned to support projects that involve broad research alliances. This paper provides a brief introduction to the key elements of bold, discusses their functional capabilities, and concludes by examining computational resources and future prospects. PMID:18784790

Temporal fractal analysis of the rs-BOLD signal identifies brain abnormalities in autism spectrum disorder.

PubMed

Dona, Olga; Hall, Geoffrey B; Noseworthy, Michael D

2017-01-01

Brain connectivity in autism spectrum disorders (ASD) has proven difficult to characterize due to the heterogeneous nature of the spectrum. Connectivity in the brain occurs in a complex, multilevel and multi-temporal manner, driving the fluctuations observed in local oxygen demand. These fluctuations can be characterized as fractals, as they auto-correlate at different time scales. In this study, we propose a model-free complexity analysis based on the fractal dimension of the rs-BOLD signal, acquired with magnetic resonance imaging. The fractal dimension can be interpreted as measure of signal complexity and connectivity. Previous studies have suggested that reduction in signal complexity can be associated with disease. Therefore, we hypothesized that a detectable difference in rs-BOLD signal complexity could be observed between ASD patients and Controls. Anatomical and functional data from fifty-five subjects with ASD (12.7 ± 2.4 y/o) and 55 age-matched (14.1 ± 3.1 y/o) healthy controls were accessed through the NITRC database and the ABIDE project. Subjects were scanned using a 3T GE Signa MRI and a 32-channel RF-coil. Axial FSPGR-3D images were used to prescribe rs-BOLD (TE/TR = 30/2000ms) where 300 time points were acquired. Motion correction was performed on the functional data and anatomical and functional images were aligned and spatially warped to the N27 standard brain atlas. Fractal analysis, performed on a grey matter mask, was done by estimating the Hurst exponent in the frequency domain using a power spectral density approach and refining the estimation in the time domain with de-trended fluctuation analysis and signal summation conversion methods. Voxel-wise fractal dimension (FD) was calculated for every subject in the control group and in the ASD group to create ROI-based Z-scores for the ASD patients. Voxel-wise validation of FD normality across controls was confirmed, and non-Gaussian voxels were eliminated from subsequent analysis. To maintain a 95% confidence level, only regions where Z-score values were at least 2 standard deviations away from the mean (i.e. where |Z| > 2.0) were included in the analysis. We found that the main regions, where signal complexity significantly decreased among ASD patients, were the amygdala (p = 0.001), the vermis (p = 0.02), the basal ganglia (p = 0.01) and the hippocampus (p = 0.02). No regions reported significant increase in signal complexity in this study. Our findings were correlated with ADIR and ADOS assessment tools, reporting the highest correlation with the ADOS metrics. Brain connectivity is best modeled as a complex system. Therefore, a measure of complexity as the fractal dimension of fluctuations in brain oxygen demand and utilization could provide important information about connectivity issues in ASD. Moreover, this technique can be used in the characterization of a single subject, with respect to controls, without the need for group analysis. Our novel approach provides an ideal avenue for personalized diagnostics, thus providing unique patient specific assessment that could help in individualizing treatments.

X-ray resonant magnetic scattering ellipsometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Z.; Randall, K.J.; Gluskin, E.

1996-09-01

It is very difficult to characterize the polarization of a synchrotron radiation source in the soft and/or intermediate x-ray energy region particularly from 1 to 2 keV. Conventional multilayer mirror or single-crystal polarimeters do not work over this energy region because their throughput (the reflectivities combined with the phase shift) becomes insignificant. In this paper, we present a new ellipsometer scheme that is able to fully characterize the polarization of synchrotron radiation sources in this energy region. It is based on the dichroic x-ray resonant ferromagnetic scattering that yields information on both the polarization of the x-ray and the materialmore » (element specific) dielectric-constant tensor [C.-C. Kao {ital et} {ital al}., Phys. Rev. B {bold 50}, 9599 (1994)] due to the interband ferromagnetic Kerr effect [B.R. Cooper, Phys. Rev. A {bold 139}, 1504 (1965)]. {copyright} {ital 1996 American Institute of Physics.}« less

Spatio-temporal cerebral blood flow perfusion patterns in cortical spreading depression

NASA Astrophysics Data System (ADS)

Verisokin, Andrey Yu.; Verveyko, Darya V.; Postnov, Dmitry E.

2017-04-01

Cortical spreading depression (CSD) is an example of one of the most common abnormalities in biophysical brain functioning. Despite the fact that there are many mathematical models describing the cortical spreading depression (CSD), most of them do not take into consideration the role of redistribution of cerebral blood flow (CBF), that results in the formation of spatio-temporal patterns. The paper presents a mathematical model, which successfully explains the CBD role in the CSD process. Numerical study of this model has revealed the formation of stationary dissipative structures, visually analogous to Turing structures. However, the mechanism of their formation is not diffusion. We show these structures occur due to another type of spatial coupling, that is related to tissue perfusion rate. The proposed model predicts that at similar state of neurons the distribution of blood flow and oxygenation may by different. Currently, this effect is not taken into account when the Blood oxygen-level dependent (BOLD) contrast imaging used in functional magnetic resonance imaging (fMRI). Thus, the diagnosis on the BOLD signal can be ambiguous. We believe that our results can be used in the future for a more correct interpretation of the data obtained with fMRI, NIRS and other similar methods for research of the brain activity.

Computer-controlled stimulation for functional magnetic resonance imaging studies of the neonatal olfactory system

PubMed Central

Arichi, T; Gordon-Williams, R; Allievi, A; Groves, AM; Burdet, E; Edwards, AD

2013-01-01

Aim Olfactory sensation is highly functional early in human neonatal life, with studies suggesting that odours can influence behaviour and infant–mother bonding. Due to its good spatial properties, blood oxygen level–dependent (BOLD) contrast functional magnetic resonance imaging (fMRI) has the potential to rapidly advance our understanding of the neural activity which underlies the development of olfactory perception in this key period. We aimed to design an ‘olfactometer’ specifically for use with neonatal subjects for fMRI studies of odour perception. Methods We describe a fully automated and programmable, fMRI compatible system capable of presenting odorant liquids. To prevent contamination of the system and minimize between-subject infective risk, the majority of the olfactometer is constructed from single-use, readily available clinical equipment. The system was used to present the odour of infant formula milk in a validation group of seven neonatal subjects at term equivalent postmenstrual age (median age 40 weeks). Results A safe, reliable and reproducible pattern of stimulation was delivered leading to well-localized positive BOLD functional responses in the piriform cortex, amygdala, thalamus, insular cortex and cerebellum. Conclusions The described system is therefore suitable for detailed studies of the ontology of olfactory sensation and perception during early human brain development. PMID:23789919

Comparison of fMRI analysis methods for heterogeneous BOLD responses in block design studies.

PubMed

Liu, Jia; Duffy, Ben A; Bernal-Casas, David; Fang, Zhongnan; Lee, Jin Hyung

2017-02-15

A large number of fMRI studies have shown that the temporal dynamics of evoked BOLD responses can be highly heterogeneous. Failing to model heterogeneous responses in statistical analysis can lead to significant errors in signal detection and characterization and alter the neurobiological interpretation. However, to date it is not clear that, out of a large number of options, which methods are robust against variability in the temporal dynamics of BOLD responses in block-design studies. Here, we used rodent optogenetic fMRI data with heterogeneous BOLD responses and simulations guided by experimental data as a means to investigate different analysis methods' performance against heterogeneous BOLD responses. Evaluations are carried out within the general linear model (GLM) framework and consist of standard basis sets as well as independent component analysis (ICA). Analyses show that, in the presence of heterogeneous BOLD responses, conventionally used GLM with a canonical basis set leads to considerable errors in the detection and characterization of BOLD responses. Our results suggest that the 3rd and 4th order gamma basis sets, the 7th to 9th order finite impulse response (FIR) basis sets, the 5th to 9th order B-spline basis sets, and the 2nd to 5th order Fourier basis sets are optimal for good balance between detection and characterization, while the 1st order Fourier basis set (coherence analysis) used in our earlier studies show good detection capability. ICA has mostly good detection and characterization capabilities, but detects a large volume of spurious activation with the control fMRI data. Copyright © 2016 Elsevier Inc. All rights reserved.

Right anterior cerebellum BOLD responses reflect age related changes in Simon task sequential effects.

PubMed

Aisenberg, D; Sapir, A; Close, A; Henik, A; d'Avossa, G

2018-01-31

Participants are slower to report a feature, such as color, when the target appears on the side opposite the instructed response, than when the target appears on the same side. This finding suggests that target location, even when task-irrelevant, interferes with response selection. This effect is magnified in older adults. Lengthening the inter-trial interval, however, suffices to normalize the congruency effect in older adults, by re-establishing young-like sequential effects (Aisenberg et al., 2014). We examined the neurological correlates of age related changes by comparing BOLD signals in young and old participants performing a visual version of the Simon task. Participants reported the color of a peripheral target, by a left or right-hand keypress. Generally, BOLD responses were greater following incongruent than congruent targets. Also, they were delayed and of smaller amplitude in old than young participants. BOLD responses in visual and motor regions were also affected by the congruency of the previous target, suggesting that sequential effects may reflect remapping of stimulus location onto the hand used to make a response. Crucially, young participants showed larger BOLD responses in right anterior cerebellum to incongruent targets, when the previous target was congruent, but smaller BOLD responses to incongruent targets when the previous target was incongruent. Old participants, however, showed larger BOLD responses to congruent than incongruent targets, irrespective of the previous target congruency. We conclude that aging may interfere with the trial by trial updating of the mapping between the task-irrelevant target location and response, which takes place during the inter-trial interval in the cerebellum and underlays sequential effects in a Simon task. Copyright © 2017 Elsevier Ltd. All rights reserved.

Generate the scale-free brain music from BOLD signals

PubMed Central

Lu, Jing; Guo, Sijia; Chen, Mingming; Wang, Weixia; Yang, Hua; Guo, Daqing; Yao, Dezhong

2018-01-01

Abstract Many methods have been developed to translate a human electroencephalogram (EEG) into music. In addition to EEG, functional magnetic resonance imaging (fMRI) is another method used to study the brain and can reflect physiological processes. In 2012, we established a method to use simultaneously recorded fMRI and EEG signals to produce EEG-fMRI music, which represents a step toward scale-free brain music. In this study, we used a neural mass model, the Jansen–Rit model, to simulate activity in several cortical brain regions. The interactions between different brain regions were represented by the average normalized diffusion tensor imaging (DTI) structural connectivity with a coupling coefficient that modulated the coupling strength. Seventy-eight brain regions were adopted from the Automated Anatomical Labeling (AAL) template. Furthermore, we used the Balloon–Windkessel hemodynamic model to transform neural activity into a blood-oxygen-level dependent (BOLD) signal. Because the fMRI BOLD signal changes slowly, we used a sampling rate of 250 Hz to produce the temporal series for music generation. Then, the BOLD music was generated for each region using these simulated BOLD signals. Because the BOLD signal is scale free, these music pieces were also scale free, which is similar to classic music. Here, to simulate the case of an epileptic patient, we changed the parameter that determined the amplitude of the excitatory postsynaptic potential (EPSP) in the neural mass model. Finally, we obtained BOLD music for healthy and epileptic patients. The differences in levels of arousal between the 2 pieces of music may provide a potential tool for discriminating the different populations if the differences can be confirmed by more real data. PMID:29480872

Generate the scale-free brain music from BOLD signals.

PubMed

Lu, Jing; Guo, Sijia; Chen, Mingming; Wang, Weixia; Yang, Hua; Guo, Daqing; Yao, Dezhong

2018-01-01

Many methods have been developed to translate a human electroencephalogram (EEG) into music. In addition to EEG, functional magnetic resonance imaging (fMRI) is another method used to study the brain and can reflect physiological processes. In 2012, we established a method to use simultaneously recorded fMRI and EEG signals to produce EEG-fMRI music, which represents a step toward scale-free brain music. In this study, we used a neural mass model, the Jansen-Rit model, to simulate activity in several cortical brain regions. The interactions between different brain regions were represented by the average normalized diffusion tensor imaging (DTI) structural connectivity with a coupling coefficient that modulated the coupling strength. Seventy-eight brain regions were adopted from the Automated Anatomical Labeling (AAL) template. Furthermore, we used the Balloon-Windkessel hemodynamic model to transform neural activity into a blood-oxygen-level dependent (BOLD) signal. Because the fMRI BOLD signal changes slowly, we used a sampling rate of 250 Hz to produce the temporal series for music generation. Then, the BOLD music was generated for each region using these simulated BOLD signals. Because the BOLD signal is scale free, these music pieces were also scale free, which is similar to classic music. Here, to simulate the case of an epileptic patient, we changed the parameter that determined the amplitude of the excitatory postsynaptic potential (EPSP) in the neural mass model. Finally, we obtained BOLD music for healthy and epileptic patients. The differences in levels of arousal between the 2 pieces of music may provide a potential tool for discriminating the different populations if the differences can be confirmed by more real data. Copyright © 2017 The Authors. Published by Wolters Kluwer Health, Inc. All rights reserved.

Toward a mechanistic understanding of vulnerability to hook-and-line fishing: Boldness as the basic target of angling-induced selection.

PubMed

Klefoth, Thomas; Skov, Christian; Kuparinen, Anna; Arlinghaus, Robert

2017-12-01

In passively operated fishing gear, boldness-related behaviors should fundamentally affect the vulnerability of individual fish and thus be under fisheries selection. To test this hypothesis, we used juvenile common-garden reared carp ( Cyprinus carpio ) within a narrow size range to investigate the mechanistic basis of behavioral selection caused by angling. We focused on one key personality trait (i.e., boldness), measured in groups within ponds, two morphological traits (body shape and head shape), and one life-history trait (juvenile growth capacity) and studied mean standardized selection gradients caused by angling. Carp behavior was highly repeatable within ponds. In the short term, over seven days of fishing, total length, not boldness, was the main predictor of angling vulnerability. However, after 20 days of fishing, boldness turned out to be the main trait under selection, followed by juvenile growth rate, while morphological traits were only weakly related to angling vulnerability. In addition, we found juvenile growth rate to be moderately correlated with boldness. Hence, direct selection on boldness will also induce indirect selection on juvenile growth and vice versa, but given that the two traits are not perfectly correlated, independent evolution of both traits is also possible. Our study is among the first to mechanistically reveal that energy-acquisition-related behaviors, and not growth rate per se, are key factors determining the probability of capture, and hence, behavioral traits appear to be the prime targets of angling selection. We predict an evolutionary response toward increased shyness in intensively angling-exploited fish stocks, possibly causing the emergence of a timidity syndrome.

Measuring vascular reactivity with breath-holds after stroke: a method to aid interpretation of group-level BOLD signal changes in longitudinal fMRI studies.

PubMed

Geranmayeh, Fatemeh; Wise, Richard J S; Leech, Robert; Murphy, Kevin

2015-05-01

Blood oxygenation level-dependent (BOLD) contrast functional magnetic resonance imaging (fMRI) is a widely used technique to map brain function, and to monitor its recovery after stroke. Since stroke has a vascular etiology, the neurovascular coupling between cerebral blood flow and neural activity may be altered, resulting in uncertainties when interpreting longitudinal BOLD signal changes. The purpose of this study was to demonstrate the feasibility of using a recently validated breath-hold task in patients with stroke, both to assess group level changes in cerebrovascular reactivity (CVR) and to determine if alterations in regional CVR over time will adversely affect interpretation of task-related BOLD signal changes. Three methods of analyzing the breath-hold data were evaluated. The CVR measures were compared over healthy tissue, infarcted tissue and the peri-infarct tissue, both sub-acutely (∼2 weeks) and chronically (∼4 months). In this cohort, a lack of CVR differences in healthy tissue between the patients and controls indicates that any group level BOLD signal change observed in these regions over time is unlikely to be related to vascular alterations. CVR was reduced in the peri-infarct tissue but remained unchanged over time. Therefore, although a lack of activation in this region compared with the controls may be confounded by a reduced CVR, longitudinal group-level BOLD changes may be more confidently attributed to neural activity changes in this cohort. By including this breath-hold-based CVR assessment protocol in future studies of stroke recovery, researchers can be more assured that longitudinal changes in BOLD signal reflect true alterations in neural activity. © 2015 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.

Continuous EEG source imaging enhances analysis of EEG-fMRI in focal epilepsy.

PubMed

Vulliemoz, S; Rodionov, R; Carmichael, D W; Thornton, R; Guye, M; Lhatoo, S D; Michel, C M; Duncan, J S; Lemieux, L

2010-02-15

EEG-correlated fMRI (EEG-fMRI) studies can reveal haemodynamic changes associated with Interictal Epileptic Discharges (IED). Methodological improvements are needed to increase sensitivity and specificity for localising the epileptogenic zone. We investigated whether the estimated EEG source activity improved models of the BOLD changes in EEG-fMRI data, compared to conventional < event-related > designs based solely on the visual identification of IED. Ten patients with pharmaco-resistant focal epilepsy underwent EEG-fMRI. EEG Source Imaging (ESI) was performed on intra-fMRI averaged IED to identify the irritative zone. The continuous activity of this estimated IED source (cESI) over the entire recording was used for fMRI analysis (cESI model). The maps of BOLD signal changes explained by cESI were compared to results of the conventional IED-related model. ESI was concordant with non-invasive data in 13/15 different types of IED. The cESI model explained significant additional BOLD variance in regions concordant with video-EEG, structural MRI or, when available, intracranial EEG in 10/15 IED. The cESI model allowed better detection of the BOLD cluster, concordant with intracranial EEG in 4/7 IED, compared to the IED model. In 4 IED types, cESI-related BOLD signal changes were diffuse with a pattern suggestive of contamination of the source signal by artefacts, notably incompletely corrected motion and pulse artefact. In one IED type, there was no significant BOLD change with either model. Continuous EEG source imaging can improve the modelling of BOLD changes related to interictal epileptic activity and this may enhance the localisation of the irritative zone. Copyright 2009 Elsevier Inc. All rights reserved.

Longitudinal decrease in blood oxygenation level dependent response in cerebral amyloid angiopathy.

PubMed

Switzer, Aaron R; McCreary, Cheryl; Batool, Saima; Stafford, Randall B; Frayne, Richard; Goodyear, Bradley G; Smith, Eric E

2016-01-01

Lower blood oxygenation level dependent (BOLD) signal changes in response to a visual stimulus in functional magnetic resonance imaging (fMRI) have been observed in cross-sectional studies of cerebral amyloid angiopathy (CAA), and are presumed to reflect impaired vascular reactivity. We used fMRI to detect a longitudinal change in BOLD responses to a visual stimulus in CAA, and to determine any correlations between these changes and other established biomarkers of CAA progression. Data were acquired from 22 patients diagnosed with probable CAA (using the Boston Criteria) and 16 healthy controls at baseline and one year. BOLD data were generated from the 200 most active voxels of the primary visual cortex during the fMRI visual stimulus (passively viewing an alternating checkerboard pattern). In general, BOLD amplitudes were lower at one year compared to baseline in patients with CAA (p = 0.01) but were unchanged in controls (p = 0.18). The longitudinal difference in BOLD amplitudes was significantly lower in CAA compared to controls (p < 0.001). White matter hyperintensity (WMH) volumes and number of cerebral microbleeds, both presumed to reflect CAA-mediated vascular injury, increased over time in CAA (p = 0.007 and p = 0.001, respectively). Longitudinal increases in WMH (rs = 0.04, p = 0.86) or cerebral microbleeds (rs = -0.18, p = 0.45) were not associated with the longitudinal decrease in BOLD amplitudes.

Impact of physiological noise correction on detecting blood oxygenation level-dependent contrast in the breast

NASA Astrophysics Data System (ADS)

Wallace, Tess E.; Manavaki, Roido; Graves, Martin J.; Patterson, Andrew J.; Gilbert, Fiona J.

2017-01-01

Physiological fluctuations are expected to be a dominant source of noise in blood oxygenation level-dependent (BOLD) magnetic resonance imaging (MRI) experiments to assess tumour oxygenation and angiogenesis. This work investigates the impact of various physiological noise regressors: retrospective image correction (RETROICOR), heart rate (HR) and respiratory volume per unit time (RVT), on signal variance and the detection of BOLD contrast in the breast in response to a modulated respiratory stimulus. BOLD MRI was performed at 3 T in ten volunteers at rest and during cycles of oxygen and carbogen gas breathing. RETROICOR was optimized using F-tests to determine which cardiac and respiratory phase terms accounted for a significant amount of signal variance. A nested regression analysis was performed to assess the effect of RETROICOR, HR and RVT on the model fit residuals, temporal signal-to-noise ratio, and BOLD activation parameters. The optimized RETROICOR model accounted for the largest amount of signal variance ( Δ R\\text{adj}2   =  3.3  ±  2.1%) and improved the detection of BOLD activation (P  =  0.002). Inclusion of HR and RVT regressors explained additional signal variance, but had a negative impact on activation parameter estimation (P  <  0.001). Fluctuations in HR and RVT appeared to be correlated with the stimulus and may contribute to apparent BOLD signal reactivity.

Reduced BOLD response to periodic visual stimulation.

PubMed

Parkes, Laura M; Fries, Pascal; Kerskens, Christian M; Norris, David G

2004-01-01

The blood oxygenation level-dependent (BOLD) response to entrained neuronal firing in the human visual cortex and lateral geniculate nuclei was investigated. Periodic checkerboard flashes at a range of frequencies (4-20 Hz) were used to drive the visual cortex neurons into entrained oscillatory firing. This is compared to a checkerboard flashing aperiodically, with the same average number of flashes per unit time. A magnetoencephalography (MEG) measurement was made to confirm that the periodic paradigm elicited entrainment. We found that for frequencies of 10 and 15 Hz, the periodic stimulus gave a smaller BOLD response than for the aperiodic stimulus. Detailed investigation at 15 Hz showed that the aperiodic stimulus gave a similar BOLD increase regardless of the magnitude of jitter (+/-17 ms compared to +/-33 ms), indicating that flashes need to be precise to at least 17 ms to maintain entrainment. This is also evidence that for aperiodic stimuli, the amplitude of the BOLD response ordinarily reflects the total number of flashes per unit time, irrespective of the precise spacing between them, suggesting that entrainment is the main cause of the BOLD reduction in the periodic condition. The results indicate that, during entrainment, there is a reduction in the neuronal metabolic demand. We suggest that because of the selective frequency band of this effect, it could be connected to synchronised reverberations around an internal feedback loop.

Is boldness relevant to psychopathic personality? Meta-analytic relations with non-Psychopathy Checklist-based measures of psychopathy.

PubMed

Lilienfeld, Scott O; Smith, Sarah Francis; Sauvigné, Katheryn C; Patrick, Christopher J; Drislane, Laura E; Latzman, Robert D; Krueger, Robert F

2016-10-01

Two recent meta-analyses have suggested that boldness, as assessed by the Psychopathic Personality Inventory (PPI) Fearless Dominance dimension, is largely unrelated to total or factor scores on the Psychopathy Checklist-Revised (PCL-R), raising questions concerning the relevance of largely adaptive features to psychopathy. Nevertheless, given that the PCL was developed and validated among prisoners, it may place less emphasis than do other psychopathy measures on adaptive traits, such as fearlessness, social poise, and emotional resilience. We conducted a meta-analysis (N = 10,693) of the relations between (a) boldness, as assessed by the PPI and its derivatives or measures of the triarchic model of psychopathy, and (b) non-PCL-based psychopathy measures across 32 samples. The average weighted correlation between boldness and psychopathy was medium to large (r = .39) and considerably higher than reported in prior meta-analyses; when analyses were restricted to well-validated psychopathy measures, the correlation rose to r = .44. We did not find support for the position that boldness is significantly less related to psychopathy than are the other 2 dimensions of the triarchic model. Our findings strongly suggest that boldness is relevant to at least some well-validated measures of psychopathy, and raise further questions regarding the boundaries of this condition. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Neural substrate of the late positive potential in emotional processing

PubMed Central

Liu, Yuelu; Huang, Haiqing; McGinnis, Menton; Keil, Andreas; Ding, Mingzhou

2012-01-01

The late positive potential (LPP) is a reliable electrophysiological index of emotional perception in humans. Despite years of research the brain structures that contribute to the generation and modulation of LPP are not well understood. Recording EEG and fMRI simultaneously, and applying a recently proposed single-trial ERP analysis method, we addressed the problem by correlating the single-trial LPP amplitude evoked by affective pictures with the blood-oxygen-level-dependent (BOLD) activity. Three results were found. First, relative to neutral pictures, pleasant and unpleasant pictures elicited enhanced LPP, as well as heightened BOLD activity in both visual cortices and emotion-processing structures such as amygdala and prefrontal cortex, consistent with previous findings. Second, the LPP amplitude across three picture categories was significantly correlated with BOLD activity in visual cortices, temporal cortices, amygdala, orbitofrontal cortex, and insula. Third, within each picture category, LPP-BOLD coupling revealed category-specific differences. For pleasant pictures, the LPP amplitude was coupled with BOLD in occipitotemporal junction, medial prefrontal cortex, amygdala, and precuneus, whereas for unpleasant pictures, significant LPP-BOLD correlation was observed in ventrolateral prefrontal cortex, insula, and posterior cingulate cortex. These results suggest that LPP is generated and modulated by an extensive brain network comprised of both cortical and subcortical structures associated with visual and emotional processing and the degree of contribution by each of these structures to the LPP modulation is valence-specific. PMID:23077042

Association between glutamate/glutamine and blood oxygen level dependent signal in the left dorsolateral prefrontal region during verbal working memory.

PubMed

Vijayakumari, Anupa A; Thomas, Bejoy; Menon, Ramshekhar N; Kesavadas, Chandrasekharan

2018-04-11

Functional MRI (fMRI) has provided much insight into the changes in the neuronal activity on the basis of blood oxygen level dependent (BOLD) phenomenon. The dynamic changes in the metabolites can be detected using functional proton magnetic resonance spectroscopy (H-fMRS). The strategy of combining fMRI and H-fMRS would facilitate the understanding of the neurochemical interpretation of the BOLD signal. The dorsolateral prefrontal region is critically involved in the processing of working memory (WM), as demonstrated by the studies involving the neuroimaging, neuropsychological, and electrophysiological experiments. In this study, we tested the association between BOLD signal and changes in brain metabolites in the left dorsolateral prefrontal region using N-back verbal WM task. We used single-voxel task-based H-MRS acquired in the left dorsolateral prefrontal region and fMRI during the performance of N-back verbal WM task to investigate the association between changes in metabolites and BOLD response in 10 healthy participants. The correlation between changes in metabolites and percent signal change was examined by the Pearson correlation. The Pearson correlation analysis revealed a significant positive correlation between the BOLD signal and glutamate/glutamine in the left dorsolateral prefrontal region during the verbal WM. Our finding suggests that glutamate/glutamine cycle plays a critical role in the neuronal activation as reflected by the changes in the BOLD response.

Task effects on BOLD signal correlates of implicit syntactic processing

PubMed Central

Caplan, David

2010-01-01

BOLD signal was measured in sixteen participants who made timed font change detection judgments in visually presented sentences that varied in syntactic structure and the order of animate and inanimate nouns. Behavioral data indicated that sentences were processed to the level of syntactic structure. BOLD signal increased in visual association areas bilaterally and left supramarginal gyrus in the contrast of sentences with object- and subject-extracted relative clauses without font changes in which the animacy order of the nouns biased against the syntactically determined meaning of the sentence. This result differs from the findings in a non-word detection task (Caplan et al, 2008a), in which the same contrast led to increased BOLD signal in the left inferior frontal gyrus. The difference in areas of activation indicates that the sentences were processed differently in the two tasks. These differences were further explored in an eye tracking study using the materials in the two tasks. Issues pertaining to how parsing and interpretive operations are affected by a task that is being performed, and how this might affect BOLD signal correlates of syntactic contrasts, are discussed. PMID:20671983

Task effects on BOLD signal correlates of implicit syntactic processing.

PubMed

Caplan, David

2010-07-01

BOLD signal was measured in sixteen participants who made timed font change detection judgments in visually presented sentences that varied in syntactic structure and the order of animate and inanimate nouns. Behavioral data indicated that sentences were processed to the level of syntactic structure. BOLD signal increased in visual association areas bilaterally and left supramarginal gyrus in the contrast of sentences with object- and subject-extracted relative clauses without font changes in which the animacy order of the nouns biased against the syntactically determined meaning of the sentence. This result differs from the findings in a non-word detection task (Caplan et al, 2008a), in which the same contrast led to increased BOLD signal in the left inferior frontal gyrus. The difference in areas of activation indicates that the sentences were processed differently in the two tasks. These differences were further explored in an eye tracking study using the materials in the two tasks. Issues pertaining to how parsing and interpretive operations are affected by a task that is being performed, and how this might affect BOLD signal correlates of syntactic contrasts, are discussed.

Heritability of boldness and aggressiveness in the zebrafish.

PubMed

Ariyomo, Tolulope O; Carter, Mauricio; Watt, Penelope J

2013-03-01

Behavioural traits that are consistent over time and in different contexts are often referred to as personality traits. These traits influence fitness because they play a major role in foraging, reproduction and survival, and so it is assumed that they have little or no additive genetic variance and, consequently, low heritability because, theoretically, they are under strong selection. Boldness and aggressiveness are two personality traits that have been shown to affect fitness. By crossing single males to multiple females, we estimated the heritability of boldness and aggressiveness in the zebrafish, Danio rerio. The additive genetic variance was statistically significant for both traits and the heritability estimates (95 % confidence intervals) for boldness and aggressiveness were 0.76 (0.49, 0.90) and 0.36 (0.10, 0.72) respectively. Furthermore, there were significant maternal effects accounting for 18 and 9 % of the proportion of phenotypic variance in boldness and aggressiveness respectively. This study shows that there is a significant level of genetic variation in this population that would allow these traits to evolve in response to selection.

Individual personality differences in Port Jackson sharks Heterodontus portusjacksoni.

PubMed

Byrnes, E E; Brown, C

2016-08-01

This study examined interindividual personality differences between Port Jackson sharks Heterodontus portusjacksoni utilizing a standard boldness assay. Additionally, the correlation between differences in individual boldness and stress reactivity was examined, exploring indications of individual coping styles. Heterodontus portusjacksoni demonstrated highly repeatable individual differences in boldness and stress reactivity. Individual boldness scores were highly repeatable across four trials such that individuals that were the fastest to emerge in the first trial were also the fastest to emerge in subsequent trials. Additionally, individuals that were the most reactive to a handling stressor in the first trial were also the most reactive in a second trial. The strong link between boldness and stress response commonly found in teleosts was also evident in this study, providing evidence of proactive-reactive coping styles in H. portusjacksoni. These results demonstrate the presence of individual personality differences in sharks for the first time. Understanding how personality influences variation in elasmobranch behaviour such as prey choice, habitat use and activity levels is critical to better managing these top predators which play important ecological roles in marine ecosystems. © 2016 The Fisheries Society of the British Isles.

Complexity of low-frequency blood oxygen level-dependent fluctuations covaries with local connectivity.

PubMed

Anderson, Jeffrey S; Zielinski, Brandon A; Nielsen, Jared A; Ferguson, Michael A

2014-04-01

Very low-frequency blood oxygen level-dependent (BOLD) fluctuations have emerged as a valuable tool for describing brain anatomy, neuropathology, and development. Such fluctuations exhibit power law frequency dynamics, with largest amplitude at lowest frequencies. The biophysical mechanisms generating such fluctuations are poorly understood. Using publicly available data from 1,019 subjects of age 7-30, we show that BOLD fluctuations exhibit temporal complexity that is linearly related to local connectivity (regional homogeneity), consistently and significantly covarying across subjects and across gray matter regions. This relationship persisted independently of covariance with gray matter density or standard deviation of BOLD signal. During late neurodevelopment, BOLD fluctuations were unchanged with age in association cortex while becoming more random throughout the rest of the brain. These data suggest that local interconnectivity may play a key role in establishing the complexity of low-frequency BOLD fluctuations underlying functional magnetic resonance imaging connectivity. Stable low-frequency power dynamics may emerge through segmentation and integration of connectivity during development of distributed large-scale brain networks. Copyright © 2013 Wiley Periodicals, Inc.

--No Title--

Science.gov Websites

@font-face { font-family: 'DroidSansRegular'; src: url('../fonts/droidsans-webfont.eot'); src: url -family: 'DroidSansBold'; src: url('../fonts/droidsans-bold-webfont.eot'); src: url('../fonts/droidsans

Extraction of dynamic functional connectivity from brain grey matter and white matter for MCI classification.

PubMed

Chen, Xiaobo; Zhang, Han; Zhang, Lichi; Shen, Celina; Lee, Seong-Whan; Shen, Dinggang

2017-10-01

Brain functional connectivity (FC) extracted from resting-state fMRI (RS-fMRI) has become a popular approach for diagnosing various neurodegenerative diseases, including Alzheimer's disease (AD) and its prodromal stage, mild cognitive impairment (MCI). Current studies mainly construct the FC networks between grey matter (GM) regions of the brain based on temporal co-variations of the blood oxygenation level-dependent (BOLD) signals, which reflects the synchronized neural activities. However, it was rarely investigated whether the FC detected within the white matter (WM) could provide useful information for diagnosis. Motivated by the recently proposed functional correlation tensors (FCT) computed from RS-fMRI and used to characterize the structured pattern of local FC in the WM, we propose in this article a novel MCI classification method based on the information conveyed by both the FC between the GM regions and that within the WM regions. Specifically, in the WM, the tensor-based metrics (e.g., fractional anisotropy [FA], similar to the metric calculated based on diffusion tensor imaging [DTI]) are first calculated based on the FCT and then summarized along each of the major WM fiber tracts connecting each pair of the brain GM regions. This could capture the functional information in the WM, in a similar network structure as the FC network constructed for the GM, based only on the same RS-fMRI data. Moreover, a sliding window approach is further used to partition the voxel-wise BOLD signal into multiple short overlapping segments. Then, both the FC and FCT between each pair of the brain regions can be calculated based on the BOLD signal segments in the GM and WM, respectively. In such a way, our method can generate dynamic FC and dynamic FCT to better capture functional information in both GM and WM and further integrate them together by using our developed feature extraction, selection, and ensemble learning algorithms. The experimental results verify that the dynamic FCT can provide valuable functional information in the WM; by combining it with the dynamic FC in the GM, the diagnosis accuracy for MCI subjects can be significantly improved even using RS-fMRI data alone. Hum Brain Mapp 38:5019-5034, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Forward Air Controllers in the Vietnam War: Exemplars of Audacity, Innovation, and Irreverence

DTIC Science & Technology

2016-06-10

Controllers (FACs). They were bold men who linked air power to ground forces, supersonic jets to propellers, and bombs to targets. They faced their...were bold men who linked air power to ground forces, supersonic jets to propellers, and bombs to targets. They faced their enemy at low altitudes, in...They were bold men who linked air power to ground forces, supersonic jets to propellers, and bombs to targets. FACs were the cutting edge of the

Effect of hunger level and time of day on boldness and aggression in the zebrafish Danio rerio.

PubMed

Ariyomo, T O; Watt, P J

2015-06-01

The effect of two environmental variables, hunger level (fed or not fed before behavioural assays) and time of day (morning or afternoon), on the boldness and aggressiveness of male and female zebrafish Danio rerio, was tested. The results showed that neither hunger level nor time of testing influenced boldness in males and females, but hunger level significantly affected aggression in females when compared with males. © 2015 The Fisheries Society of the British Isles.

Development of visual cortical function in infant macaques: A BOLD fMRI study

PubMed Central

Meeson, Alan; Munk, Matthias H. J.; Kourtzi, Zoe; Movshon, J. Anthony; Logothetis, Nikos K.; Kiorpes, Lynne

2017-01-01

Functional brain development is not well understood. In the visual system, neurophysiological studies in nonhuman primates show quite mature neuronal properties near birth although visual function is itself quite immature and continues to develop over many months or years after birth. Our goal was to assess the relative development of two main visual processing streams, dorsal and ventral, using BOLD fMRI in an attempt to understand the global mechanisms that support the maturation of visual behavior. Seven infant macaque monkeys (Macaca mulatta) were repeatedly scanned, while anesthetized, over an age range of 102 to 1431 days. Large rotating checkerboard stimuli induced BOLD activation in visual cortices at early ages. Additionally we used static and dynamic Glass pattern stimuli to probe BOLD responses in primary visual cortex and two extrastriate areas: V4 and MT-V5. The resulting activations were analyzed with standard GLM and multivoxel pattern analysis (MVPA) approaches. We analyzed three contrasts: Glass pattern present/absent, static/dynamic Glass pattern presentation, and structured/random Glass pattern form. For both GLM and MVPA approaches, robust coherent BOLD activation appeared relatively late in comparison to the maturation of known neuronal properties and the development of behavioral sensitivity to Glass patterns. Robust differential activity to Glass pattern present/absent and dynamic/static stimulus presentation appeared first in V1, followed by V4 and MT-V5 at older ages; there was no reliable distinction between the two extrastriate areas. A similar pattern of results was obtained with the two analysis methods, although MVPA analysis showed reliable differential responses emerging at later ages than GLM. Although BOLD responses to large visual stimuli are detectable, our results with more refined stimuli indicate that global BOLD activity changes as behavioral performance matures. This reflects an hierarchical development of the visual pathways. Since fMRI BOLD reflects neural activity on a population level, our results indicate that, although individual neurons might be adult-like, a longer maturation process takes place on a population level. PMID:29145469

Corticostriatal and Dopaminergic Response to Beer Flavor with Both fMRI and [(11) C]raclopride Positron Emission Tomography.

PubMed

Oberlin, Brandon G; Dzemidzic, Mario; Harezlak, Jaroslaw; Kudela, Maria A; Tran, Stella M; Soeurt, Christina M; Yoder, Karmen K; Kareken, David A

2016-09-01

Cue-evoked drug-seeking behavior likely depends on interactions between frontal activity and ventral striatal (VST) dopamine (DA) transmission. Using [(11) C]raclopride (RAC) positron emission tomography (PET), we previously demonstrated that beer flavor (absent intoxication) elicited VST DA release in beer drinkers, inferred by RAC displacement. Here, a subset of subjects from this previous RAC-PET study underwent a similar paradigm during functional magnetic resonance imaging (fMRI) to test how orbitofrontal cortex (OFC) and VST blood oxygenation level-dependent (BOLD) responses to beer flavor are related to VST DA release and motivation to drink. Male beer drinkers (n = 28, age = 24 ± 2, drinks/wk = 16 ± 10) from our previous PET study participated in a similar fMRI paradigm wherein subjects tasted their most frequently consumed brand of beer and Gatorade(®) (appetitive control). We tested for correlations between BOLD activation in fMRI and VST DA responses in PET, and drinking-related variables. Compared to Gatorade, beer flavor increased wanting and desire to drink, and induced BOLD responses in bilateral OFC and right VST. Wanting and desire to drink correlated with both right VST and medial OFC BOLD activation to beer flavor. Like the BOLD findings, beer flavor (relative to Gatorade) again induced right VST DA release in this fMRI subject subset, but there was no correlation between DA release and the magnitude of BOLD responses in frontal regions of interest. Both imaging modalities showed a right-lateralized VST response (BOLD and DA release) to a drug-paired conditioned stimulus, whereas fMRI BOLD responses in the VST and medial OFC also reflected wanting and desire to drink. The data suggest the possibility that responses to drug-paired cues may be rightward biased in the VST (at least in right-handed males) and that VST and OFC responses in this gustatory paradigm reflect stimulus wanting. Copyright © 2016 by the Research Society on Alcoholism.

Digital Encounters: Using Information Technology in an Overseas Branch Campus

ERIC Educational Resources Information Center

Reilly, Benjamin

2008-01-01

In fall of 2004, Carnegie Mellon University embarked on a bold educational experiment, the establishment of an overseas branch campus at Education City in the Persian Gulf state of Qatar. Carnegie Mellon's decision to open up shop in the Middle East was by no means unique; indeed, Carnegie Mellon is just one of a growing number of institutions to…

Biography Today. Profiles of People of Interest to Young Readers. Artists Series. Vol. 1, 1996.

ERIC Educational Resources Information Center

Harris, Laurie Lanzen, Ed.; Abbey, Cherie D., Ed.

This issue of "Biography Today" features 18 short biographies about artists in a format young readers can enjoy and understand. Each entry provides at least one picture of the individual profiled, and bold-faced rubrics lead the reader to information on birth, youth, early memories, education, first jobs, marriage and family, career highlights,…

Biography Today: Sports Series. Profiles of People of Interest to Young Readers, Volume 4.

ERIC Educational Resources Information Center

Harris, Laurie Lanzen, Ed.; Abbey, Cherie D., Ed.

This book is the fourth in a series of biographies on today's sports figures designed for students age 9 years and older. It contains alphabetically arranged sketches of the sports figures. Each entry provides at least one picture of the individual profiled. Bold faced rubrics lead the reader to information on birth, youth, early memories,…

Biography Today: Profiles of People of Interest to Young Readers. Sports Series, Volume 9.

ERIC Educational Resources Information Center

Abbey, Cherie D., Ed.

This ninth volume of the "Biography Today Sports" series is intended to appeal to young readers in a format they can enjoy reading and readily understand. Each alphabetically-arranged sketch provides at least one picture of the individual profiled, and bold-faced rubrics lead the reader to information on birth, youth, early memories,…

Cortical lamina-dependent blood volume changes in human brain at 7 T.

PubMed

Huber, Laurentius; Goense, Jozien; Kennerley, Aneurin J; Trampel, Robert; Guidi, Maria; Reimer, Enrico; Ivanov, Dimo; Neef, Nicole; Gauthier, Claudine J; Turner, Robert; Möller, Harald E

2015-02-15

Cortical layer-dependent high (sub-millimeter) resolution functional magnetic resonance imaging (fMRI) in human or animal brain can be used to address questions regarding the functioning of cortical circuits, such as the effect of different afferent and efferent connectivities on activity in specific cortical layers. The sensitivity of gradient echo (GE) blood oxygenation level-dependent (BOLD) responses to large draining veins reduces its local specificity and can render the interpretation of the underlying laminar neural activity impossible. The application of the more spatially specific cerebral blood volume (CBV)-based fMRI in humans has been hindered by the low sensitivity of the noninvasive modalities available. Here, a vascular space occupancy (VASO) variant, adapted for use at high field, is further optimized to capture layer-dependent activity changes in human motor cortex at sub-millimeter resolution. Acquired activation maps and cortical profiles show that the VASO signal peaks in gray matter at 0.8-1.6mm depth, and deeper compared to the superficial and vein-dominated GE-BOLD responses. Validation of the VASO signal change versus well-established iron-oxide contrast agent based fMRI methods in animals showed the same cortical profiles of CBV change, after normalization for lamina-dependent baseline CBV. In order to evaluate its potential of revealing small lamina-dependent signal differences due to modulations of the input-output characteristics, layer-dependent VASO responses were investigated in the ipsilateral hemisphere during unilateral finger tapping. Positive activation in ipsilateral primary motor cortex and negative activation in ipsilateral primary sensory cortex were observed. This feature is only visible in high-resolution fMRI where opposing sides of a sulcus can be investigated independently because of a lack of partial volume effects. Based on the results presented here, we conclude that VASO offers good reproducibility, high sensitivity and lower sensitivity than GE-BOLD to changes in larger vessels, making it a valuable tool for layer-dependent fMRI studies in humans. Copyright © 2014 Elsevier Inc. All rights reserved.

Integrating EEG and fMRI in epilepsy.

PubMed

Formaggio, Emanuela; Storti, Silvia Francesca; Bertoldo, Alessandra; Manganotti, Paolo; Fiaschi, Antonio; Toffolo, Gianna Maria

2011-02-14

Integrating electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) studies enables to non-invasively investigate human brain function and to find the direct correlation of these two important measures of brain activity. Presurgical evaluation of patients with epilepsy is one of the areas where EEG and fMRI integration has considerable clinical relevance for localizing the brain regions generating interictal epileptiform activity. The conventional analysis of EEG-fMRI data is based on the visual identification of the interictal epileptiform discharges (IEDs) on scalp EEG. The convolution of these EEG events, represented as stick functions, with a model of the fMRI response, i.e. the hemodynamic response function, provides the regressor for general linear model (GLM) analysis of fMRI data. However, the conventional analysis is not automatic and suffers of some subjectivity in IEDs classification. Here, we present an easy-to-use and automatic approach for combined EEG-fMRI analysis able to improve IEDs identification based on Independent Component Analysis and wavelet analysis. EEG signal due to IED is reconstructed and its wavelet power is used as a regressor in GLM. The method was validated on simulated data and then applied on real data set consisting of 2 normal subjects and 5 patients with partial epilepsy. In all continuous EEG-fMRI recording sessions a good quality EEG was obtained allowing the detection of spontaneous IEDs and the analysis of the related BOLD activation. The main clinical finding in EEG-fMRI studies of patients with partial epilepsy is that focal interictal slow-wave activity was invariably associated with increased focal BOLD responses in a spatially related brain area. Our study extends current knowledge on epileptic foci localization and confirms previous reports suggesting that BOLD activation associated with slow activity might have a role in localizing the epileptogenic region even in the absence of clear interictal spikes. Copyright © 2010 Elsevier Inc. All rights reserved.

A comparison of smartphone and paper data-collection tools in the Burden of Obstructive Lung Disease (BOLD) study in Gezira state, Sudan

PubMed Central

Ahmed, Rana; Robinson, Ryan; Elsony, Asma; Thomson, Rachael; Squire, S. Bertel; Malmborg, Rasmus; Burney, Peter

2018-01-01

Introduction Data collection using paper-based questionnaires can be time consuming and return errors affect data accuracy, completeness, and information quality in health surveys. We compared smartphone and paper-based data collection systems in the Burden of Obstructive Lung Disease (BOLD) study in rural Sudan. Methods This exploratory pilot study was designed to run in parallel with the cross-sectional household survey. The Open Data Kit was used to programme questionnaires in Arabic into smartphones. We included 100 study participants (83% women; median age = 41.5 ± 16.4 years) from the BOLD study from 3 rural villages in East-Gezira and Kamleen localities of Gezira state, Sudan. Questionnaire data were collected using smartphone and paper-based technologies simultaneously. We used Kappa statistics and inter-rater class coefficient to test agreement between the two methods. Results Symptoms reported included cough (24%), phlegm (15%), wheezing (17%), and shortness of breath (18%). One in five were or had been cigarette smokers. The two data collection methods varied between perfect to slight agreement across the 204 variables evaluated (Kappa varied between 1.00 and 0.02 and inter-rater coefficient between 1.00 and -0.12). Errors were most commonly seen with paper questionnaires (83% of errors seen) vs smartphones (17% of errors seen) administered questionnaires with questions with complex skip-patterns being a major source of errors in paper questionnaires. Automated checks and validations in smartphone-administered questionnaires avoided skip-pattern related errors. Incomplete and inconsistent records were more likely seen on paper questionnaires. Conclusion Compared to paper-based data collection, smartphone technology worked well for data collection in the study, which was conducted in a challenging rural environment in Sudan. This approach provided timely, quality data with fewer errors and inconsistencies compared to paper-based data collection. We recommend this method for future BOLD studies and other population-based studies in similar settings. PMID:29518132

Self-Regulation of Amygdala Activation Using Real-Time fMRI Neurofeedback

PubMed Central

Phillips, Raquel; Alvarez, Ruben P.; Simmons, W. Kyle; Bellgowan, Patrick; Drevets, Wayne C.; Bodurka, Jerzy

2011-01-01

Real-time functional magnetic resonance imaging (rtfMRI) with neurofeedback allows investigation of human brain neuroplastic changes that arise as subjects learn to modulate neurophysiological function using real-time feedback regarding their own hemodynamic responses to stimuli. We investigated the feasibility of training healthy humans to self-regulate the hemodynamic activity of the amygdala, which plays major roles in emotional processing. Participants in the experimental group were provided with ongoing information about the blood oxygen level dependent (BOLD) activity in the left amygdala (LA) and were instructed to raise the BOLD rtfMRI signal by contemplating positive autobiographical memories. A control group was assigned the same task but was instead provided with sham feedback from the left horizontal segment of the intraparietal sulcus (HIPS) region. In the LA, we found a significant BOLD signal increase due to rtfMRI neurofeedback training in the experimental group versus the control group. This effect persisted during the Transfer run without neurofeedback. For the individual subjects in the experimental group the training effect on the LA BOLD activity correlated inversely with scores on the Difficulty Identifying Feelings subscale of the Toronto Alexithymia Scale. The whole brain data analysis revealed significant differences for Happy Memories versus Rest condition between the experimental and control groups. Functional connectivity analysis of the amygdala network revealed significant widespread correlations in a fronto-temporo-limbic network. Additionally, we identified six regions — right medial frontal polar cortex, bilateral dorsomedial prefrontal cortex, left anterior cingulate cortex, and bilateral superior frontal gyrus — where the functional connectivity with the LA increased significantly across the rtfMRI neurofeedback runs and the Transfer run. The findings demonstrate that healthy subjects can learn to regulate their amygdala activation using rtfMRI neurofeedback, suggesting possible applications of rtfMRI neurofeedback training in the treatment of patients with neuropsychiatric disorders. PMID:21931738

Common neural correlates of intertemporal choices and intelligence in adolescents.

PubMed

Ripke, Stephan; Hübner, Thomas; Mennigen, Eva; Müller, Kathrin U; Li, Shu-Chen; Smolka, Michael N

2015-02-01

Converging behavioral evidence indicates that temporal discounting, measured by intertemporal choice tasks, is inversely related to intelligence. At the neural level, the parieto-frontal network is pivotal for complex, higher-order cognitive processes. Relatedly, underrecruitment of the pFC during a working memory task has been found to be associated with steeper temporal discounting. Furthermore, this network has also been shown to be related to the consistency of intertemporal choices. Here we report an fMRI study that directly investigated the association of neural correlates of intertemporal choice behavior with intelligence in an adolescent sample (n = 206; age 13.7-15.5 years). After identifying brain regions where the BOLD response during intertemporal choice was correlated with individual differences in intelligence, we further tested whether BOLD responses in these areas would mediate the associations between intelligence, the discounting rate, and choice consistency. We found positive correlations between BOLD response in a value-independent decision network (i.e., dorsolateral pFC, precuneus, and occipital areas) and intelligence. Furthermore, BOLD response in a value-dependent decision network (i.e., perigenual ACC, inferior frontal gyrus, ventromedial pFC, ventral striatum) was positively correlated with intelligence. The mediation analysis revealed that BOLD responses in the value-independent network mediated the association between intelligence and choice consistency, whereas BOLD responses in the value-dependent network mediated the association between intelligence and the discounting rate. In summary, our findings provide evidence for common neural correlates of intertemporal choice and intelligence, possibly linked by valuation as well as executive functions.

Neurochemical and BOLD responses during neuronal activation measured in the human visual cortex at 7 Tesla.

PubMed

Bednařík, Petr; Tkáč, Ivan; Giove, Federico; DiNuzzo, Mauro; Deelchand, Dinesh K; Emir, Uzay E; Eberly, Lynn E; Mangia, Silvia

2015-03-31

Several laboratories have consistently reported small concentration changes in lactate, glutamate, aspartate, and glucose in the human cortex during prolonged stimuli. However, whether such changes correlate with blood oxygenation level-dependent functional magnetic resonance imaging (BOLD-fMRI) signals have not been determined. The present study aimed at characterizing the relationship between metabolite concentrations and BOLD-fMRI signals during a block-designed paradigm of visual stimulation. Functional magnetic resonance spectroscopy (fMRS) and fMRI data were acquired from 12 volunteers. A short echo-time semi-LASER localization sequence optimized for 7 Tesla was used to achieve full signal-intensity MRS data. The group analysis confirmed that during stimulation lactate and glutamate increased by 0.26 ± 0.06 μmol/g (~30%) and 0.28 ± 0.03 μmol/g (~3%), respectively, while aspartate and glucose decreased by 0.20 ± 0.04 μmol/g (~5%) and 0.19 ± 0.03 μmol/g (~16%), respectively. The single-subject analysis revealed that BOLD-fMRI signals were positively correlated with glutamate and lactate concentration changes. The results show a linear relationship between metabolic and BOLD responses in the presence of strong excitatory sensory inputs, and support the notion that increased functional energy demands are sustained by oxidative metabolism. In addition, BOLD signals were inversely correlated with baseline γ-aminobutyric acid concentration. Finally, we discussed the critical importance of taking into account linewidth effects on metabolite quantification in fMRS paradigms.

Neurobiological evidence for attention bias to food, emotional dysregulation, disinhibition and deficient somatosensory awareness in obesity with binge eating disorder.

PubMed

Aviram-Friedman, Roni; Astbury, Nerys; Ochner, Christopher N; Contento, Isobel; Geliebter, Allan

2018-02-01

To refine the biobehavioral markers of binge eating disorder (BED). We conducted fMRI brain scans using images of high energy processed food (HEPF), low energy unprocessed food (LEUF), or non-foods (NF) in 42 adults (obese with BED [obese -BED; n=13] and obese with no BED [obese non-BED; n=29]) selected via ads. Two blood oxygenated level dependent (BOLD) signal contrast maps were examined: food versus nonfood, and HEPF versus LEUF. In addition, score differences on the disinhibition scale were correlated with BOLD signals. food versus nonfood showed greater BOLD activity for BED in emotional, motivational and somatosensory brain areas: insula, anterior cingulate cortex (ACC), Brodmann areas (BA) 19 & 32, inferior parietal lobule (IPL), posterior cingulate cortex (PCC), and lingual, postcentral, middle temporal and cuneate gyri (p≤0.005; k≥88). HEPF versus LEUF showed greater BOLD activity for BED in inhibitory brain regions: BA 6, middle and superior frontal gyri (p<0.01; k≥119). The groups also differed in the relationships between disinhibition and BOLD activity in the postcentral gyrus (PCG; p=0.04) and ACC-BA 32 (p=0.02). For all participants jointly, PCG BOLD amplitude predicted greater disinhibition (p=0.04). Food images elicited neural activity indicating attention bias (cuneate & PCG), emotion dysregulation (BA 19 & 32), and disinhibition (MFG, BA6 & SFG) in obese with BED. These may help tailor a treatment for the obesity with BED phenotype. Copyright © 2017. Published by Elsevier Inc.

Accounting for the role of hematocrit in between-subject variations of MRI-derived baseline cerebral hemodynamic parameters and functional BOLD responses.

PubMed

Xu, Feng; Li, Wenbo; Liu, Peiying; Hua, Jun; Strouse, John J; Pekar, James J; Lu, Hanzhang; van Zijl, Peter C M; Qin, Qin

2018-01-01

Baseline hematocrit fraction (Hct) is a determinant for baseline cerebral blood flow (CBF) and between-subject variation of Hct thus causes variation in task-based BOLD fMRI signal changes. We first verified in healthy volunteers (n = 12) that Hct values can be derived reliably from venous blood T 1 values by comparison with the conventional lab test. Together with CBF measured using phase-contrast MRI, this noninvasive estimation of Hct, instead of using a population-averaged Hct value, enabled more individual determination of oxygen delivery (DO 2 ), oxygen extraction fraction (OEF), and cerebral metabolic rate of oxygen (CMRO 2 ). The inverse correlation of CBF and Hct explained about 80% of between-subject variation of CBF in this relatively uniform cohort of subjects, as expected based on the regulation of DO 2 to maintain constant CMRO 2 . Furthermore, we compared the relationships of visual task-evoked BOLD response with Hct and CBF. We showed that Hct and CBF contributed 22%-33% of variance in BOLD signal and removing the positive correlation with Hct and negative correlation with CBF allowed normalization of BOLD signal with 16%-22% lower variability. The results of this study suggest that adjustment for Hct effects is useful for studies of MRI perfusion and BOLD fMRI. Hum Brain Mapp 39:344-353, 2018. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

What is feasible with imaging human brain function and connectivity using functional magnetic resonance imaging

PubMed Central

2016-01-01

When we consider all of the methods we employ to detect brain function, from electrophysiology to optical techniques to functional magnetic resonance imaging (fMRI), we do not really have a ‘golden technique’ that meets all of the needs for studying the brain. We have methods, each of which has significant limitations but provide often complimentary information. Clearly, there are many questions that need to be answered about fMRI, which unlike other methods, allows us to study the human brain. However, there are also extraordinary accomplishments or demonstration of the feasibility of reaching new and previously unexpected scales of function in the human brain. This article reviews some of the work we have pursued, often with extensive collaborations with other co-workers, towards understanding the underlying mechanisms of the methodology, defining its limitations, and developing solutions to advance it. No doubt, our knowledge of human brain function has vastly expanded since the introduction of fMRI. However, methods and instrumentation in this dynamic field have evolved to a state that discoveries about the human brain based on fMRI principles, together with information garnered at a much finer spatial and temporal scale through other methods, are poised to significantly accelerate in the next decade. This article is part of the themed issue ‘Interpreting BOLD: a dialogue between cognitive and cellular neuroscience’. PMID:27574313

What is feasible with imaging human brain function and connectivity using functional magnetic resonance imaging.

PubMed

Ugurbil, Kamil

2016-10-05

When we consider all of the methods we employ to detect brain function, from electrophysiology to optical techniques to functional magnetic resonance imaging (fMRI), we do not really have a 'golden technique' that meets all of the needs for studying the brain. We have methods, each of which has significant limitations but provide often complimentary information. Clearly, there are many questions that need to be answered about fMRI, which unlike other methods, allows us to study the human brain. However, there are also extraordinary accomplishments or demonstration of the feasibility of reaching new and previously unexpected scales of function in the human brain. This article reviews some of the work we have pursued, often with extensive collaborations with other co-workers, towards understanding the underlying mechanisms of the methodology, defining its limitations, and developing solutions to advance it. No doubt, our knowledge of human brain function has vastly expanded since the introduction of fMRI. However, methods and instrumentation in this dynamic field have evolved to a state that discoveries about the human brain based on fMRI principles, together with information garnered at a much finer spatial and temporal scale through other methods, are poised to significantly accelerate in the next decade.This article is part of the themed issue 'Interpreting BOLD: a dialogue between cognitive and cellular neuroscience'. © 2016 The Author(s).

Differences in boldness are repeatable and heritable in a long-lived marine predator

PubMed Central

Patrick, Samantha C; Charmantier, Anne; Weimerskirch, Henri

2013-01-01

Animal personalities, composed of axes of consistent individual behaviors, are widely reported and can have important fitness consequences. However, despite theoretical predictions that life-history trade-offs may cause and maintain personality differences, our understanding of the evolutionary ecology of personality remains poor, especially in long-lived species where trade-offs and senescence have been shown to be stronger. Furthermore, although much theoretical and empirical work assumes selection shapes variation in personalities, studies exploring the genetic underpinnings of personality traits are rare. Here we study one standard axis of personality, the shy–bold continuum, in a long-lived marine species, the wandering albatross from Possession Island, Crozet, by measuring the behavioral response to a human approach. Using generalized linear mixed models in a Bayesian framework, we show that boldness is highly repeatable and heritable. We also find strong differences in boldness between breeding colonies, which vary in size and density, suggesting birds are shyer in more dense colonies. These results demonstrate that in this seabird population, boldness is both heritable and repeatable and highlights the potential for ecological and evolutionary processes to shape personality traits in species with varying life-history strategies. PMID:24340172

Differences in boldness are repeatable and heritable in a long-lived marine predator.

PubMed

Patrick, Samantha C; Charmantier, Anne; Weimerskirch, Henri

2013-11-01

Animal personalities, composed of axes of consistent individual behaviors, are widely reported and can have important fitness consequences. However, despite theoretical predictions that life-history trade-offs may cause and maintain personality differences, our understanding of the evolutionary ecology of personality remains poor, especially in long-lived species where trade-offs and senescence have been shown to be stronger. Furthermore, although much theoretical and empirical work assumes selection shapes variation in personalities, studies exploring the genetic underpinnings of personality traits are rare. Here we study one standard axis of personality, the shy-bold continuum, in a long-lived marine species, the wandering albatross from Possession Island, Crozet, by measuring the behavioral response to a human approach. Using generalized linear mixed models in a Bayesian framework, we show that boldness is highly repeatable and heritable. We also find strong differences in boldness between breeding colonies, which vary in size and density, suggesting birds are shyer in more dense colonies. These results demonstrate that in this seabird population, boldness is both heritable and repeatable and highlights the potential for ecological and evolutionary processes to shape personality traits in species with varying life-history strategies.

Hemodynamic and electrophysiological relationship involved in human face processing: evidence from a combined fMRI-ERP study.

PubMed

Iidaka, Tetsuya; Matsumoto, Atsushi; Haneda, Kaoruko; Okada, Tomohisa; Sadato, Norihiro

2006-03-01

Functional magnetic resonance imaging (fMRI) and event-related potential (ERP) experiments were conducted in the same group of subjects and with an identical task paradigm to investigate a possible relationship between hemodynamic and electrophysiological responses within the brain. The subjects were instructed to judge whether visually presented stimuli were faces or houses and then press the corresponding button. Functional MRI identified face- and house-related regions in the lateral and medial part of the fusiform gyrus, respectively, while ERP showed significantly greater N170 negativity for face than for house stimuli in the temporo-occipital electrodes. Correlation analysis between the BOLD signal in the fusiform gyrus and ERP parameters demonstrated a close relationship between the signal and both latency and amplitude of N170 across the subjects. These correlations may indicate that the variation in cognitive demand and hemodynamic responses during the face/house discrimination task is coupled with the variation of N170 peak latency/amplitude across the subjects. Thus, integrative analysis of spatial and temporal information obtained from the two experimental modalities may help in studying neural correlates involved in a particular cognitive task.

Measurement of renal tissue oxygenation with blood oxygen level-dependent MRI and oxygen transit modeling

PubMed Central

Morrell, Glen; Rusinek, Henry; Warner, Lizette; Vivier, Pierre-Hugues; Cheung, Alfred K.; Lerman, Lilach O.; Lee, Vivian S.

2014-01-01

Blood oxygen level-dependent (BOLD) MRI data of kidney, while indicative of tissue oxygenation level (Po2), is in fact influenced by multiple confounding factors, such as R2, perfusion, oxygen permeability, and hematocrit. We aim to explore the feasibility of extracting tissue Po2 from renal BOLD data. A method of two steps was proposed: first, a Monte Carlo simulation to estimate blood oxygen saturation (SHb) from BOLD signals, and second, an oxygen transit model to convert SHb to tissue Po2. The proposed method was calibrated and validated with 20 pigs (12 before and after furosemide injection) in which BOLD-derived tissue Po2 was compared with microprobe-measured values. The method was then applied to nine healthy human subjects (age: 25.7 ± 3.0 yr) in whom BOLD was performed before and after furosemide. For the 12 pigs before furosemide injection, the proposed model estimated renal tissue Po2 with errors of 2.3 ± 5.2 mmHg (5.8 ± 13.4%) in cortex and −0.1 ± 4.5 mmHg (1.7 ± 18.1%) in medulla, compared with microprobe measurements. After injection of furosemide, the estimation errors were 6.9 ± 3.9 mmHg (14.2 ± 8.4%) for cortex and 2.6 ± 4.0 mmHg (7.7 ± 11.5%) for medulla. In the human subjects, BOLD-derived medullary Po2 increased from 16.0 ± 4.9 mmHg (SHb: 31 ± 11%) at baseline to 26.2 ± 3.1 mmHg (SHb: 53 ± 6%) at 5 min after furosemide injection, while cortical Po2 did not change significantly at ∼58 mmHg (SHb: 92 ± 1%). Our proposed method, validated with a porcine model, appears promising for estimating tissue Po2 from renal BOLD MRI data in human subjects. PMID:24452640

How does spatial extent of fMRI datasets affect independent component analysis decomposition?

PubMed

Aragri, Adriana; Scarabino, Tommaso; Seifritz, Erich; Comani, Silvia; Cirillo, Sossio; Tedeschi, Gioacchino; Esposito, Fabrizio; Di Salle, Francesco

2006-09-01

Spatial independent component analysis (sICA) of functional magnetic resonance imaging (fMRI) time series can generate meaningful activation maps and associated descriptive signals, which are useful to evaluate datasets of the entire brain or selected portions of it. Besides computational implications, variations in the input dataset combined with the multivariate nature of ICA may lead to different spatial or temporal readouts of brain activation phenomena. By reducing and increasing a volume of interest (VOI), we applied sICA to different datasets from real activation experiments with multislice acquisition and single or multiple sensory-motor task-induced blood oxygenation level-dependent (BOLD) signal sources with different spatial and temporal structure. Using receiver operating characteristics (ROC) methodology for accuracy evaluation and multiple regression analysis as benchmark, we compared sICA decompositions of reduced and increased VOI fMRI time-series containing auditory, motor and hemifield visual activation occurring separately or simultaneously in time. Both approaches yielded valid results; however, the results of the increased VOI approach were spatially more accurate compared to the results of the decreased VOI approach. This is consistent with the capability of sICA to take advantage of extended samples of statistical observations and suggests that sICA is more powerful with extended rather than reduced VOI datasets to delineate brain activity. (c) 2006 Wiley-Liss, Inc.

21 CFR 166.40 - Labeling of margarine.

Code of Federal Regulations, 2014 CFR

2014-04-01

... each letter as measured by a closely fitting rectangle drawn around it, and the boldness of letters or... letters in the word “oleomargarine” or “margarine” should be equal to or exceed in prominence and boldness...

21 CFR 166.40 - Labeling of margarine.

Code of Federal Regulations, 2013 CFR

2013-04-01

... each letter as measured by a closely fitting rectangle drawn around it, and the boldness of letters or... letters in the word “oleomargarine” or “margarine” should be equal to or exceed in prominence and boldness...

21 CFR 166.40 - Labeling of margarine.

Code of Federal Regulations, 2012 CFR

2012-04-01

... each letter as measured by a closely fitting rectangle drawn around it, and the boldness of letters or... letters in the word “oleomargarine” or “margarine” should be equal to or exceed in prominence and boldness...

Express yourself: bold individuals induce enhanced morphological defences

PubMed Central

Hulthén, Kaj; Chapman, Ben B.; Nilsson, P. Anders; Hollander, Johan; Brönmark, Christer

2014-01-01

Organisms display an impressive array of defence strategies in nature. Inducible defences (changes in morphology and/or behaviour within a prey's lifetime) allow prey to decrease vulnerability to predators and avoid unnecessary costs of expression. Many studies report considerable interindividual variation in the degree to which inducible defences are expressed, yet what underlies this variation is poorly understood. Here, we show that individuals differing in a key personality trait also differ in the magnitude of morphological defence expression. Crucian carp showing risky behaviours (bold individuals) expressed a significantly greater morphological defence response when exposed to a natural enemy when compared with shy individuals. Furthermore, we show that fish of different personality types differ in their behavioural plasticity, with shy fish exhibiting greater absolute plasticity than bold fish. Our data suggest that individuals with bold personalities may be able to compensate for their risk-prone behavioural type by expressing enhanced morphological defences. PMID:24335987

A Big Five facet analysis of sub-clinical narcissism: understanding boldness in terms of well-known personality traits.

PubMed

Furnham, Adrian; Crump, John

2014-08-01

This study aimed to examine a Big Five 'bright-side' analysis of a sub-clinical personality disorder, i.e. narcissism. A total of 6957 British adults completed the NEO-PI-R, which measures the Big Five Personality factors at the domain and the facet level, as well as the Hogan Development Survey (HDS), which has a measure of Narcissism called Bold as one of its dysfunctional interpersonal tendencies. Correlation and regression results confirmed many of the associations between the Big Five domains and facets (NEO-PI-R) and sub-clinical narcissism. The Bold (Narcissism) scale from the HDS was the criterion variable in all analyses. Bold individuals are disagreeable extraverts with very low scores on facet Modesty but moderately high scores on Assertiveness, Competence and Achievement Striving. The study confirmed work using different population groups and different measures. Copyright © 2014 John Wiley & Sons, Ltd.

Flying Too Close to the Sun: Lessons Learned from the Judicial Expansion of the Objective Patient Standard for Informed Consent in Wisconsin.

PubMed

Derse, Arthur R

2017-03-01

The Wisconsin Supreme Court, after adopting the doctrine of the objective (reasonable) patient standard, expanded it in bold and innovative ways over nearly four decades, until the Wisconsin legislative and executive branches drastically reversed this course. The saga has implications for other jurisdictions considering adoption or expansion of the objective patient standard doctrine.

Biography Today: Scientists & Inventors Series. Profiles of People of Interest to Young Readers. Vol. 1, 1996.

ERIC Educational Resources Information Center

Harris, Laurie Lanzen, Ed.; Abbey, Cherie D., Ed.

This issue of "Biography Today" looks at scientists and inventors and is created to appeal to young readers in a format they can and enjoy and easily understand. Each entry provides at least one picture of the individual profiled, and bold-faced rubrics lead the reader to information on birth, youth, early memories, education, first jobs, marriage…

The Republic of Singapore: Informed Questions

DTIC Science & Technology

2003-01-01

Singaporean society has, until recently, exhibited a high degree of tolerance and social cohesion .7 Yet Singapore exists as a conspicuously wealthy...immigrants threatens to alter Singapore’s ethnic composition and thus undermine the social cohesion upon which the country’s stability and...bold measures in response to perceived threats to the nation’s prized social cohesion . In March 2001, the government initiated high-level dialog

Structure-specific magnetic field inhomogeneities and its effect on the correlation time.

PubMed

Ziener, Christian H; Bauer, Wolfgang R; Melkus, Gerd; Weber, Thomas; Herold, Volker; Jakob, Peter M

2006-12-01

We describe the relationship between the correlation time and microscopic spatial inhomogeneities in the static magnetic field. The theory takes into account diffusion of nuclear spins in the inhomogeneous field created by magnetized objects. A simple general expression for the correlation time is obtained. It is shown that the correlation time is dependent on a characteristic length, the diffusion coefficient of surrounding medium, the permeability of the surface and the volume fraction of the magnetized objects. For specific geometries (spheres and cylinders), exact analytical expressions for the correlation time are given. The theory can be applied to contrast agents (magnetically labeled cells), capillary network, BOLD effect and so forth.

Quarks and the cosmos.

PubMed

Turner, Michael S

2007-01-05

Cosmology is in the midst of a period of revolutionary discovery, propelled by bold ideas from particle physics and by technological advances from gigapixel charge-coupled device cameras to peta-scale computing. The basic features of the universe have now been determined: It is 13.7 billion years old, spatially flat, and expanding at an accelerating rate; it is composed of atoms (4%), exotic dark matter (20%), and dark energy (76%); and there is evidence that galaxies and other structures were seeded by quantum fluctuations. Although we know much about the universe, we understand far less. Poised to dramatically advance our understanding of both the universe and the laws that govern it, cosmology is on the verge of a golden age.

Assessment of three plastid DNA barcode markers for identification of Clinacanthus nutans (Acanthaceae).

PubMed

Ismail, Noor Zafirah; Arsad, Hasni; Samian, Mohammed Razip; Hamdan, Mohammad Razak; Othman, Ahmad Sofiman

2018-01-01

This study was conducted to determine the feasibility of using three plastid DNA regions ( matK , trnH - psbA , and rbcL ) as DNA barcodes to identify the medicinal plant Clinacanthus nutans . In this study, C. nutans was collected at several different locations. Total genomic DNA was extracted, amplified by polymerase chain reaction (PCR), and sequenced using matK , trnH - psbA , and rbcL , primers. DNA sequences generated from PCR were submitted to the National Center for Biotechnology Information's (NCBI) GenBank. Identification of C. nutans was carried out using NCBI's Basic Local Alignment Search Tool (BLAST). The rbcL and trnH - psbA regions successfully identified C. nutans with sequencing rates of 100% through BLAST identification. Molecular Evolutionary Genetics Analysis (MEGA) 6.0 was used to analyze interspecific and intraspecific divergence of plastid DNA sequences. rbcL and matK exhibited the lowest average interspecific distance (0.0487 and 0.0963, respectively), whereas trnH - psbA exhibited the highest average interspecific distance (0.2029). The R package Spider revealed that trnH - psbA correctly identified Barcode of Life Data System (BOLD) 96%, best close match 79%, and near neighbor 100% of the species, compared to matK (BOLD 72%; best close match 64%; near neighbor 78%) and rbcL (BOLD 77%; best close match 62%; near neighbor 88%). These results indicate that trnH - psbA is very effective at identifying C. nutans , as it performed well in discriminating species in Acanthaceae.

Electrodermal Recording and fMRI to Inform Sensorimotor Recovery in Stroke Patients

PubMed Central

MacIntosh, Bradley J.; McIlroy, William E.; Mraz, Richard; Staines, W. Richard; Black, Sandra E.; Graham, Simon J.

2016-01-01

Background Functional magnetic resonance imaging (fMRI) appears to be useful for investigating motor recovery after stroke. Some of the potential confounders of brain activation studies, however, could be mitigated through complementary physiological monitoring. Objective To investigate a sensorimotor fMRI battery that included simultaneous measurement of electrodermal activity in subjects with hemiparetic stroke to provide a measure related to the sense of effort during motor performance. Methods Bilateral hand and ankle tasks were performed by 6 patients with stroke (2 subacute, 4 chronic) during imaging with blood oxygen level-dependent (BOLD) fMRI using an event-related design. BOLD percent changes, peak activation, and laterality index values were calculated in the sensorimotor cortex. Electrodermal recordings were made concurrently and used as a regressor. Results Sensorimotor BOLD time series and percent change values provided evidence of an intact motor network in each of these well-recovered patients. During tasks involving the hemiparetic limb, electrodermal activity changes were variable in amplitude, and electrodermal activity time-series data showed significant correlations with fMRI in 3 of 6 patients. No such correlations were observed for control tasks involving the unaffected lower limb. Conclusions Electrodermal activity activation maps implicated the contralesional over the ipsilesional hemisphere, supporting the notion that stroke patients may require higher order motor processing to perform simple tasks. Electrodermal activity recordings may be useful as a physiological marker of differences in effort required during movements of a subject’s hemiparetic compared with the unaffected limb during fMRI studies. PMID:18784267

Oxygenation in cervical cancer and normal uterine cervix assessed using blood oxygenation level-dependent (BOLD) MRI at 3T.

PubMed

Hallac, Rami R; Ding, Yao; Yuan, Qing; McColl, Roderick W; Lea, Jayanthi; Sims, Robert D; Weatherall, Paul T; Mason, Ralph P

2012-12-01

Hypoxia is reported to be a biomarker for poor prognosis in cervical cancer. However, a practical noninvasive method is needed for the routine clinical evaluation of tumor hypoxia. This study examined the potential use of blood oxygenation level-dependent (BOLD) contrast MRI as a noninvasive technique to assess tumor vascular oxygenation at 3T. Following Institutional Review Board-approved informed consent and in compliance with the Health Insurance Portability and Accountability Act, successful results were achieved in nine patients with locally advanced cervical cancer [International Federation of Gynecology and Obstetrics (FIGO) stage IIA to IVA] and three normal volunteers. In the first four patients, dynamic T₂*-weighted MRI was performed in the transaxial plane using a multi-shot echo planar imaging sequence whilst patients breathed room air followed by oxygen (15 dm³/min). Later, a multi-echo gradient echo examination was added to provide quantitative R₂* measurements. The baseline T₂*-weighted signal intensity was quite stable, but increased to various extents in tumors on initiation of oxygen breathing. The signal in normal uterus increased significantly, whereas that in the iliacus muscle did not change. R₂* responded significantly in healthy uterus, cervix and eight cervical tumors. This preliminary study demonstrates that BOLD MRI of cervical cancer at 3T is feasible. However, more patients must be evaluated and followed clinically before any prognostic value can be determined. Copyright © 2012 John Wiley & Sons, Ltd.

Evidence accumulation detected in BOLD signal using slow perceptual decision making.

PubMed

Krueger, Paul M; van Vugt, Marieke K; Simen, Patrick; Nystrom, Leigh; Holmes, Philip; Cohen, Jonathan D

2017-04-01

We assessed whether evidence accumulation could be observed in the BOLD signal during perceptual decision making. This presents a challenge since the hemodynamic response is slow, while perceptual decisions are typically fast. Guided by theoretical predictions of the drift diffusion model, we slowed down decisions by penalizing participants for incorrect responses. Second, we distinguished BOLD activity related to stimulus detection (modeled using a boxcar) from activity related to integration (modeled using a ramp) by minimizing the collinearity of GLM regressors. This was achieved by dissecting a boxcar into its two most orthogonal components: an "up-ramp" and a "down-ramp." Third, we used a control condition in which stimuli and responses were similar to the experimental condition, but that did not engage evidence accumulation of the stimuli. The results revealed an absence of areas in parietal cortex that have been proposed to drive perceptual decision making but have recently come into question; and newly identified regions that are candidates for involvement in evidence accumulation. Previous fMRI studies have either used fast perceptual decision making, which precludes the measurement of evidence accumulation, or slowed down responses by gradually revealing stimuli. The latter approach confounds perceptual detection with evidence accumulation because accumulation is constrained by perceptual input. We slowed down the decision making process itself while leaving perceptual information intact. This provided a more sensitive and selective observation of brain regions associated with the evidence accumulation processes underlying perceptual decision making than previous methods. Copyright © 2017 Elsevier B.V. All rights reserved.

The effect of dissolved oxygen on the relaxation rates of blood plasma: Implications for hyperoxia calibrated BOLD.

PubMed

Ma, Yuhan; Berman, Avery J L; Pike, G Bruce

2016-12-01

To determine the contribution of paramagnetic dissolved oxygen in blood plasma to blood-oxygenation-level-dependent (BOLD) signal changes in hyperoxic calibrated BOLD studies. Bovine blood plasma samples were prepared with partial pressures of oxygen (pO 2 ) ranging from 110 to 600 mmHg. R 1 , R 2 , and R 2 * of the plasma with dissolved oxygen were measured using quantitative MRI sequences at 3 Tesla. Simulations were performed to predict the relative effects of dissolved oxygen and deoxyhemoglobin changes in hyperoxia calibrated BOLD. The relaxivities of dissolved oxygen in plasma were found to be r 1, O2 =1.97 ± 0.09 ×10 -4 s -1 mmHg -1 , r 2, O2 =2.3 ± 0.7 ×10 -4 s -1 mmHg -1 , and r 2, O2 * = 2.3 ± 0.7 ×10 -4 s -1 mmHg -1 . Simulations predict that neither the transverse nor longitudinal relaxation rates of dissolved oxygen contribute significantly to the BOLD signal during hyperoxia. During hyperoxia, the increases in R 2 and R 2 * of blood from dissolved oxygen in plasma are considerably less than the decreases in R 2 and R 2 * from venous deoxyhemoglobin. R 1 effects due to dissolved oxygen are also predicted to be negligible. As a result, dissolved oxygen in arteries should not contribute significantly to the hyperoxic calibrated BOLD signal. Magn Reson Med 76:1905-1911, 2016. © 2015 International Society for Magnetic Resonance in Medicine. © 2015 International Society for Magnetic Resonance in Medicine.

Mapping Transient Hyperventilation Induced Alterations with Estimates of the Multi-Scale Dynamics of BOLD Signal.

PubMed

Kiviniemi, Vesa; Remes, Jukka; Starck, Tuomo; Nikkinen, Juha; Haapea, Marianne; Silven, Olli; Tervonen, Osmo

2009-01-01

Temporal blood oxygen level dependent (BOLD) contrast signals in functional MRI during rest may be characterized by power spectral distribution (PSD) trends of the form 1/f(alpha). Trends with 1/f characteristics comprise fractal properties with repeating oscillation patterns in multiple time scales. Estimates of the fractal properties enable the quantification of phenomena that may otherwise be difficult to measure, such as transient, non-linear changes. In this study it was hypothesized that the fractal metrics of 1/f BOLD signal trends can map changes related to dynamic, multi-scale alterations in cerebral blood flow (CBF) after a transient hyperventilation challenge. Twenty-three normal adults were imaged in a resting-state before and after hyperventilation. Different variables (1/f trend constant alpha, fractal dimension D(f), and, Hurst exponent H) characterizing the trends were measured from BOLD signals. The results show that fractal metrics of the BOLD signal follow the fractional Gaussian noise model, even during the dynamic CBF change that follows hyperventilation. The most dominant effect on the fractal metrics was detected in grey matter, in line with previous hyperventilation vaso-reactivity studies. The alpha was able to differentiate also blood vessels from grey matter changes. D(f) was most sensitive to grey matter. H correlated with default mode network areas before hyperventilation but this pattern vanished after hyperventilation due to a global increase in H. In the future, resting-state fMRI combined with fractal metrics of the BOLD signal may be used for analyzing multi-scale alterations of cerebral blood flow.

BOLD response to semantic and syntactic processing during hypoglycemia is load-dependent.

PubMed

Schafer, Robin J; Page, Kathleen A; Arora, Jagriti; Sherwin, Robert; Constable, R Todd

2012-01-01

This study investigates how syntactic and semantic load factors impact sentence comprehension and BOLD signal under moderate hypoglycemia. A dual session, whole brain fMRI study was conducted on 16 healthy participants using the glucose clamp technique. In one session, they experienced insulin-induced hypoglycemia (plasma glucose at ∼50mg/dL); in the other, plasma glucose was maintained at euglycemic levels (∼100mg/dL). During scans subjects were presented with sentences of contrasting syntactic (embedding vs. conjunction) and semantic (reversibility vs. irreversibility) load. Semantic factors dominated the overall load effects on both performance (p<0.001) and BOLD response (p<0.01, corrected). Differential BOLD signal was observed in frontal, temporal, temporo-parietal and medio-temporal regions. Hypoglycemia and syntactic factors significantly impacted performance (p=0.002) and BOLD response (p<0.01, corrected) in the reversible clause conditions, more extensively in reversible-embedded than in reversible-conjoined clauses. Hypoglycemia resulted in a robust decrease in performance on reversible clauses and exerted attenuating effects on BOLD unselectively across cortical circuits. The dominance of reversibility in all measures underscores the distinction between the syntactic and semantic contrasts. The syntactic is based in a quantitative difference in algorithms interpreting embedded and conjoined structures. We suggest that the semantic is based in a qualitative difference between algorithmic mapping of arguments in reversible clauses and heuristic linking in irreversible clauses. Because heuristics drastically reduce resource demand, the operations they support would resist the load-dependent cognitive consequences of hypoglycemia. © 2011 Elsevier Inc. All rights reserved.

Neurochemical and BOLD responses during neuronal activation measured in the human visual cortex at 7 Tesla

PubMed Central

Bednařík, Petr; Tkáč, Ivan; Giove, Federico; DiNuzzo, Mauro; Deelchand, Dinesh K; Emir, Uzay E; Eberly, Lynn E; Mangia, Silvia

2015-01-01

Several laboratories have consistently reported small concentration changes in lactate, glutamate, aspartate, and glucose in the human cortex during prolonged stimuli. However, whether such changes correlate with blood oxygenation level–dependent functional magnetic resonance imaging (BOLD-fMRI) signals have not been determined. The present study aimed at characterizing the relationship between metabolite concentrations and BOLD-fMRI signals during a block-designed paradigm of visual stimulation. Functional magnetic resonance spectroscopy (fMRS) and fMRI data were acquired from 12 volunteers. A short echo-time semi-LASER localization sequence optimized for 7 Tesla was used to achieve full signal-intensity MRS data. The group analysis confirmed that during stimulation lactate and glutamate increased by 0.26±0.06 μmol/g (~30%) and 0.28±0.03 μmol/g (~3%), respectively, while aspartate and glucose decreased by 0.20±0.04 μmol/g (~5%) and 0.19±0.03 μmol/g (~16%), respectively. The single-subject analysis revealed that BOLD-fMRI signals were positively correlated with glutamate and lactate concentration changes. The results show a linear relationship between metabolic and BOLD responses in the presence of strong excitatory sensory inputs, and support the notion that increased functional energy demands are sustained by oxidative metabolism. In addition, BOLD signals were inversely correlated with baseline γ-aminobutyric acid concentration. Finally, we discussed the critical importance of taking into account linewidth effects on metabolite quantification in fMRS paradigms. PMID:25564236

Does social context affect boldness in juveniles?

PubMed

Loftus, Siobhan; Borcherding, Jost

2017-12-01

Differences in boldness are common between populations or between related species and are discussed as part of individual coping style, personality, or behavioral syndrome. Boldness has been found to be dependent on experience, social, and environmental contexts. The major aim of the present study was to establish an experimental environment that would allow analyzing the risk-taking behavior of 2 competing invasive goby species. Neogobius melanostomus was more active in the absence of a predator Sander lucioperca than N. fluviatilis and clearly spent more time "swimming" and "feeding" than N. fluviatilis . In addition, N. melanostomus was always faster than N. fluviatilis both when leaving the shelter and reaching offered food. Based on the different behaviors recorded, species-specific boldness scores were established using a principal component analysis. Although there was no overall difference in boldness scores between the 2 species, both competitive conditions and the effect of the predator played significant roles as factors influencing boldness. Neogobius melanostomus was more affected by the presence/absence of the predator than the social circumstances. Neogobius fluviatilis , on the other hand, was more active and bolder in competitive situations. However, when alone, N. fluviatilis was rather inactive and displayed altogether shy behavior, independent of the presence/absence of the predator. Thus, the study confirms the prediction that there are differences in behavior and behavioral plasticity, and therein predator-avoidance strategies, between ecologically similar species of goby living in sympatry. We argue that these differences may be related to differential habitat use of both invasive species that presently dominate the fish community in the Lower Rhine.

Does social context affect boldness in juveniles?

PubMed Central

Borcherding, Jost

2017-01-01

Abstract Differences in boldness are common between populations or between related species and are discussed as part of individual coping style, personality, or behavioral syndrome. Boldness has been found to be dependent on experience, social, and environmental contexts. The major aim of the present study was to establish an experimental environment that would allow analyzing the risk-taking behavior of 2 competing invasive goby species. Neogobius melanostomus was more active in the absence of a predator Sander lucioperca than N. fluviatilis and clearly spent more time “swimming” and “feeding” than N. fluviatilis. In addition, N. melanostomus was always faster than N. fluviatilis both when leaving the shelter and reaching offered food. Based on the different behaviors recorded, species-specific boldness scores were established using a principal component analysis. Although there was no overall difference in boldness scores between the 2 species, both competitive conditions and the effect of the predator played significant roles as factors influencing boldness. Neogobius melanostomus was more affected by the presence/absence of the predator than the social circumstances. Neogobius fluviatilis, on the other hand, was more active and bolder in competitive situations. However, when alone, N. fluviatilis was rather inactive and displayed altogether shy behavior, independent of the presence/absence of the predator. Thus, the study confirms the prediction that there are differences in behavior and behavioral plasticity, and therein predator-avoidance strategies, between ecologically similar species of goby living in sympatry. We argue that these differences may be related to differential habitat use of both invasive species that presently dominate the fish community in the Lower Rhine. PMID:29492025

Evaluation of Visceral Adipose Tissue Oxygenation by Blood Oxygen Level-Dependent MRI in Zucker Diabetic Fatty Rats.

PubMed

Shi, Hong-Jian; Li, Yan-Feng; Ji, Wen-Jie; Lin, Zhi-Chun; Cai, Wei; Chen, Tao; Yuan, Bin; Niu, Xiu-Long; Li, Han-Ying; Shu, Wen; Li, Yu-Ming; Yuan, Fei; Zhou, Xin; Zhang, Zhuoli

2018-06-01

This study aimed to investigate the feasibility of blood oxygen level-dependent magnetic resonance imaging (BOLD-MRI) to evaluate visceral adipose tissue (VAT) oxygenation in Zucker diabetic fatty (ZDF) rats and its associations with systemic metaflammation. Five-week-old ZDF rats and Zucker lean (ZL) rats were fed a high-fat diet (HFD) for 18 weeks. A baseline BOLD-MRI scan of perirenal adipose tissue was performed after 8 weeks of HFD feeding, and then the rats were randomized to receive pioglitazone or a vehicle for the following 10 weeks. At sacrifice, BOLD-MRI scan, Hypoxyprobe-1 injection, and circulating T helper 17 (Th17), regulatory T (Treg) cells, and monocyte subtype flow cytometry analysis were performed. HFD feeding led to a significant increase in VAT BOLD-MRI R2* signals (20.14 ± 0.23 per second vs. 21.53 ± 0.20 per second; P = 0.012), an indicator for decreased oxygenation. R2* signal was significantly correlated with VAT pimonidazole adduct-positive area, insulin resistance, Th17 and Treg cells, CD43 + and CD43+ + monocyte subtypes, and VAT macrophage infiltration. Pioglitazone treatment improved the insulin resistance and was associated with a delayed progression of VAT oxygenation. This work demonstrated the feasibility of BOLD-MRI for detecting the VAT oxygenation status in ZDF rats, and the BOLD-MRI signals were associated with insulin resistance and systemic metaflammation in ZDF rats during the development of obesity. © 2018 The Obesity Society.

Calibrated FMRI.

PubMed

Hoge, Richard D

2012-08-15

Functional magnetic resonance imaging with blood oxygenation level-dependent (BOLD) contrast has had a tremendous influence on human neuroscience in the last twenty years, providing a non-invasive means of mapping human brain function with often exquisite sensitivity and detail. However the BOLD method remains a largely qualitative approach. While the same can be said of anatomic MRI techniques, whose clinical and research impact has not been diminished in the slightest by the lack of a quantitative interpretation of their image intensity, the quantitative expression of BOLD responses as a percent of the baseline T2*- weighted signal has been viewed as necessary since the earliest days of fMRI. Calibrated MRI attempts to dissociate changes in oxygen metabolism from changes in blood flow and volume, the latter three quantities contributing jointly to determine the physiologically ambiguous percent BOLD change. This dissociation is typically performed using a "calibration" procedure in which subjects inhale a gas mixture containing small amounts of carbon dioxide or enriched oxygen to produce changes in blood flow and BOLD signal which can be measured under well-defined hemodynamic conditions. The outcome is a calibration parameter M which can then be substituted into an expression providing the fractional change in oxygen metabolism given changes in blood flow and BOLD signal during a task. The latest generation of calibrated MRI methods goes beyond fractional changes to provide absolute quantification of resting-state oxygen consumption in micromolar units, in addition to absolute measures of evoked metabolic response. This review discusses the history, challenges, and advances in calibrated MRI, from the personal perspective of the author. Copyright © 2012 Elsevier Inc. All rights reserved.

Simultaneous GCaMP6-based fiber photometry and fMRI in rats.

PubMed

Liang, Zhifeng; Ma, Yuncong; Watson, Glenn D R; Zhang, Nanyin

2017-09-01

Understanding the relationship between neural and vascular signals is essential for interpretation of functional MRI (fMRI) results with respect to underlying neuronal activity. Simultaneously measuring neural activity using electrophysiology with fMRI has been highly valuable in elucidating the neural basis of the blood oxygenation-level dependent (BOLD) signal. However, this approach is also technically challenging due to the electromagnetic interference that is observed in electrophysiological recordings during MRI scanning. Recording optical correlates of neural activity, such as calcium signals, avoids this issue, and has opened a new avenue to simultaneously acquire neural and BOLD signals. The present study is the first to demonstrate the feasibility of simultaneously and repeatedly acquiring calcium and BOLD signals in animals using a genetically encoded calcium indicator, GCaMP6. This approach was validated with a visual stimulation experiment, during which robust increases of both calcium and BOLD signals in the superior colliculus were observed. In addition, repeated measurement in the same animal demonstrated reproducible calcium and BOLD responses to the same stimuli. Taken together, simultaneous GCaMP6-based fiber photometry and fMRI recording presents a novel, artifact-free approach to simultaneously measuring neural and fMRI signals. Furthermore, given the cell-type specificity of GCaMP6, this approach has the potential to mechanistically dissect the contributions of individual neuron populations to BOLD signal, and ultimately reveal its underlying neural mechanisms. The current study established the method for simultaneous GCaMP6-based fiber photometry and fMRI in rats. Copyright © 2017 Elsevier B.V. All rights reserved.

Non-linear Relationship between BOLD Activation and Amplitude of Beta Oscillations in the Supplementary Motor Area during Rhythmic Finger Tapping and Internal Timing.

PubMed

Gompf, Florian; Pflug, Anja; Laufs, Helmut; Kell, Christian A

2017-01-01

Functional imaging studies using BOLD contrasts have consistently reported activation of the supplementary motor area (SMA) both during motor and internal timing tasks. Opposing findings, however, have been shown for the modulation of beta oscillations in the SMA. While movement suppresses beta oscillations in the SMA, motor and non-motor tasks that rely on internal timing increase the amplitude of beta oscillations in the SMA. These independent observations suggest that the relationship between beta oscillations and BOLD activation is more complex than previously thought. Here we set out to investigate this rapport by examining beta oscillations in the SMA during movement with varying degrees of internal timing demands. In a simultaneous EEG-fMRI experiment, 20 healthy right-handed subjects performed an auditory-paced finger-tapping task. Internal timing was operationalized by including conditions with taps on every fourth auditory beat, which necessitates generation of a slow internal rhythm, while tapping to every auditory beat reflected simple auditory-motor synchronization. In the SMA, BOLD activity increased and power in both the low and the high beta band decreased expectedly during each condition compared to baseline. Internal timing was associated with a reduced desynchronization of low beta oscillations compared to conditions without internal timing demands. In parallel with this relative beta power increase, internal timing activated the SMA more strongly in terms of BOLD. This documents a task-dependent non-linear relationship between BOLD and beta-oscillations in the SMA. We discuss different roles of beta synchronization and desynchronization in active processing within the same cortical region.

Navigator-gated 3D blood oxygen level-dependent CMR at 3.0-T for detection of stress-induced myocardial ischemic reactions.

PubMed

Jahnke, Cosima; Gebker, Rolf; Manka, Robert; Schnackenburg, Bernhard; Fleck, Eckart; Paetsch, Ingo

2010-04-01

This study determined the value of navigator-gated 3-dimensional blood oxygen level-dependent (BOLD) cardiac magnetic resonance (CMR) at 3.0-T for the detection of stress-induced myocardial ischemic reactions. Although BOLD CMR has been introduced for characterization of myocardial oxygenation status, previously reported CMR approaches suffered from a low signal-to-noise ratio and motion-related artifacts with impaired image quality and a limited diagnostic value in initial patient studies. Fifty patients with suspected or known coronary artery disease underwent CMR at 3.0-T followed by invasive X-ray angiography within 48 h. Three-dimensional BOLD images were acquired during free breathing with full coverage of the left ventricle in a short-axis orientation. The BOLD imaging was performed at rest and under adenosine stress, followed by stress and rest first-pass perfusion and delayed enhancement imaging. Quantitative coronary X-ray angiography (QCA) was used for coronary stenosis definition (diameter reduction > or =50%). The BOLD and first-pass perfusion images were semiquantitatively evaluated (for BOLD imaging, signal intensity differences between stress and rest [DeltaSI]; for perfusion imaging, myocardial perfusion reserve index [MPRI]). The image quality of BOLD CMR at rest and during adenosine stress was considered good to excellent in 90% and 84% of the patients, respectively. The DeltaSI measurements differed significantly between normal myocardium, myocardium supplied by a stenotic coronary artery, and infarcted myocardium (p < 0.001). The receiver-operator characteristic analysis identified a cutoff value of DeltaSI = 2.7% for the detection of coronary stenosis, resulting in a sensitivity and specificity of 85.0% and 80.5%, respectively. An MPRI cutoff value of 1.35 yielded a sensitivity and specificity of 89.5% and 85.8%, respectively. The DeltaSI significantly correlated with the degree of coronary stenosis (r = -0.65, p < 0.001). Additionally, DeltaSI and MPRI showed substantial agreement (kappa value 0.66). Navigator-gated 3-dimensional BOLD imaging at 3.0-T reliably detected stress-induced myocardial ischemic reactions and may be considered a valid alternative to first-pass exogenous contrast-enhancement studies. Copyright 2010 American College of Cardiology Foundation. Published by Elsevier Inc. All rights reserved.

Functional connectivity: integrating behavioral, diffusion tensor imaging, and functional magnetic resonance imaging data sets.

PubMed

Baird, Abigail A; Colvin, Mary K; Vanhorn, John D; Inati, Souheil; Gazzaniga, Michael S

2005-04-01

In the present study, we combined 2 types of magnetic resonance technology to explore individual differences on a task that required the recognition of objects presented from unusual viewpoints. This task was chosen based on previous work that has established the necessity of information transfer from the right parietal cortex to the left inferior cortex for its successful completion. We used reaction times (RTs) to localize regions of cortical activity in the superior parietal and inferior frontal regions (blood oxygen level-dependent [BOLD] response) that were more active with longer response times. These regions were then sampled, and their signal change used to predict individual differences in structural integrity of white matter in the corpus callosum (using diffusion tensor imaging). Results show that shorter RTs (and associated increases in BOLD response) are associated with increased organization in the splenium of the corpus callosum, whereas longer RTs are associated with increased organization in the genu.

Interaction of an electromagnetic wave with a rapidly created spatially periodic plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuo, S.P.; Faith, J.

1997-08-01

The interaction of electromagnetic waves with rapidly created time-varying spatially periodic plasmas is studied. The numerical results of the collisionless case show that both frequency upshifted and frequency downshifted waves are generated. Moreover, the frequency downshifted waves are trapped by the plasma when the plasma frequency is larger than the wave frequency. The trapping has the effect of dramatically enhancing the efficiency of the frequency downshift conversion process, by accumulating incident wave energy during the plasma transition period. A theory based on the wave impedance of each Floquet mode of the periodic structure is formulated, incorporating with the collisional dampingmore » of the plasma. Such a theory explains the recent experimental observations [Faith, Kuo, and Huang, Phys. Rev. E {bold 55}, 1843 (1997)] where the frequency downshifted signals were detected repetitively with considerably enhanced spectral intensities while the frequency upshifted signals were missing. {copyright} {ital 1997} {ital The American Physical Society}« less

Aging effects on functional auditory and visual processing using fMRI with variable sensory loading.

PubMed

Cliff, Michael; Joyce, Dan W; Lamar, Melissa; Dannhauser, Thomas; Tracy, Derek K; Shergill, Sukhwinder S

2013-05-01

Traditionally, studies investigating the functional implications of age-related structural brain alterations have focused on higher cognitive processes; by increasing stimulus load, these studies assess behavioral and neurophysiological performance. In order to understand age-related changes in these higher cognitive processes, it is crucial to examine changes in visual and auditory processes that are the gateways to higher cognitive functions. This study provides evidence for age-related functional decline in visual and auditory processing, and regional alterations in functional brain processing, using non-invasive neuroimaging. Using functional magnetic resonance imaging (fMRI), younger (n=11; mean age=31) and older (n=10; mean age=68) adults were imaged while observing flashing checkerboard images (passive visual stimuli) and hearing word lists (passive auditory stimuli) across varying stimuli presentation rates. Younger adults showed greater overall levels of temporal and occipital cortical activation than older adults for both auditory and visual stimuli. The relative change in activity as a function of stimulus presentation rate showed differences between young and older participants. In visual cortex, the older group showed a decrease in fMRI blood oxygen level dependent (BOLD) signal magnitude as stimulus frequency increased, whereas the younger group showed a linear increase. In auditory cortex, the younger group showed a relative increase as a function of word presentation rate, while older participants showed a relatively stable magnitude of fMRI BOLD response across all rates. When analyzing participants across all ages, only the auditory cortical activation showed a continuous, monotonically decreasing BOLD signal magnitude as a function of age. Our preliminary findings show an age-related decline in demand-related, passive early sensory processing. As stimulus demand increases, visual and auditory cortex do not show increases in activity in older compared to younger people. This may negatively impact on the fidelity of information available to higher cognitive processing. Such evidence may inform future studies focused on cognitive decline in aging. Copyright © 2012 Elsevier Ltd. All rights reserved.

Shy birds play it safe: personality in captivity predicts risk responsiveness during reproduction in the wild

PubMed Central

Cole, Ella F.; Quinn, John L.

2014-01-01

Despite a growing body of evidence linking personality to life-history variation and fitness, the behavioural mechanisms underlying these relationships remain poorly understood. One mechanism thought to play a key role is how individuals respond to risk. Relatively reactive and proactive (or shy and bold) personality types are expected to differ in how they manage the inherent trade-off between productivity and survival, with bold individuals being more risk-prone with lower survival probability, and shy individuals adopting a more risk-averse strategy. In the great tit (Parus major), the shy–bold personality axis has been well characterized in captivity and linked to fitness. Here, we tested whether ‘exploration behaviour’, a captive assay of the shy–bold axis, can predict risk responsiveness during reproduction in wild great tits. Relatively slow-exploring (shy) females took longer than fast-exploring (bold) birds to resume incubation after a novel object, representing an unknown threat, was attached to their nest-box, with some shy individuals not returning within the 40 min trial period. Risk responsiveness was consistent within individuals over days. These findings provide rare, field-based experimental evidence that shy individuals prioritize survival over reproductive investment, supporting the hypothesis that personality reflects life-history variation through links with risk responsiveness. PMID:24829251

Novel fMRI working memory paradigm accurately detects cognitive impairment in Multiple Sclerosis

PubMed Central

Nelson, Flavia; Akhtar, Mohammad A.; Zúñiga, Edward; Perez, Carlos A.; Hasan, Khader M.; Wilken, Jeffrey; Wolinsky, Jerry S.; Narayana, Ponnada A.; Steinberg, Joel L.

2016-01-01

Background Cognitive impairment (CI) cannot be diagnosed by MRI. Functional MRI (fMRI) paradigms such as the immediate/delayed memory task (I/DMT), detect varying degrees of working memory. Preliminary findings using I/DMT, showed differences in Blood Oxygenation Level Dependent (BOLD) activation between impaired (MSCI, n=12) and non-impaired (MSNI, n=9) MS patients. Objectives To confirm CI detection based on I/DMT’ BOLD activation in a larger cohort of MS patients. The role of T2 lesion volume (LV) and EDSS in magnitude of BOLD signal were also sought. Methods Fifty patients [EDSS mean (m) = 3.2, DD m =12 yr., age m =40yr.] underwent the Minimal Assessment of Cognitive Function in MS (MACFIMS) and the I/DMT. Working-memory activation (WMa) represents BOLD signal during DMT minus signal during IMT. CI was based on MACFIMS. Results 10 MSNI, 30 MSCI and 4 borderline patients were included in analyses. ANOVA showed MSNI had significantly greater WMa than MSCI, in the left (L) prefrontal cortex and L supplementary motor area (p = 0.032). Regression analysis showed significant inverse correlations between WMa and T2 LV/EDSS in similar areas (p = 0.005, 0.004 respectively). Conclusion I/DMT-based BOLD activation detects CI in MS, larger studies are needed to confirm these findings. PMID:27613119

Long-Latency Reductions in Gamma Power Predict Hemodynamic Changes That Underlie the Negative BOLD Signal

PubMed Central

Harris, Samuel; Bruyns-Haylett, Michael; Kennerley, Aneurin; Zheng, Ying; Martin, Chris; Jones, Myles; Redgrave, Peter; Berwick, Jason

2015-01-01

Studies that use prolonged periods of sensory stimulation report associations between regional reductions in neural activity and negative blood oxygenation level-dependent (BOLD) signaling. However, the neural generators of the negative BOLD response remain to be characterized. Here, we use single-impulse electrical stimulation of the whisker pad in the anesthetized rat to identify components of the neural response that are related to “negative” hemodynamic changes in the brain. Laminar multiunit activity and local field potential recordings of neural activity were performed concurrently with two-dimensional optical imaging spectroscopy measuring hemodynamic changes. Repeated measurements over multiple stimulation trials revealed significant variations in neural responses across session and animal datasets. Within this variation, we found robust long-latency decreases (300 and 2000 ms after stimulus presentation) in gamma-band power (30–80 Hz) in the middle-superficial cortical layers in regions surrounding the activated whisker barrel cortex. This reduction in gamma frequency activity was associated with corresponding decreases in the hemodynamic responses that drive the negative BOLD signal. These findings suggest a close relationship between BOLD responses and neural events that operate over time scales that outlast the initiating sensory stimulus, and provide important insights into the neurophysiological basis of negative neuroimaging signals. PMID:25788681

Individually assessed boldness predicts Perca fluviatilis behaviour in shoals, but is not associated with the capture order or angling method.

PubMed

Kekäläinen, J; Podgorniak, T; Puolakka, T; Hyvärinen, P; Vainikka, A

2014-11-01

Selectivity of recreational angling on fish behaviour was studied by examining whether capture order or lure type (natural v. artificial bait) in ice-fishing could explain behavioural variation among perch Perca fluviatilis individuals. It was also tested if individually assessed personality predicts fish behaviour in groups, in the presence of natural predators. Perca fluviatilis showed individually repeatable behaviour both in individual and in group tests. Capture order, capture method, condition factor or past growth rate did not explain variation in individual behaviour. Individually determined boldness as well as fish size, however, were positively associated with first entrance to the predator zone (i.e. initial risk taking) in group behaviour tests. Individually determined boldness also explained long-term activity and total time spent in the vicinity of predators in the group. These findings suggest that individual and laboratory-based boldness tests predict boldness of P. fluviatilis in also ecologically relevant conditions, i.e. in shoals and in the presence of natural predators. The present results, however, also indicate that the above-mentioned two angling methods may not be selective for certain behavioural types in comparison to each other. © 2014 The Fisheries Society of the British Isles.

Cortical functional anatomy of voluntary saccades in Parkinson disease.

PubMed

Rieger, Jochem W; Kim, Aleander; Argyelan, Miklos; Farber, Mark; Glazman, Sofya; Liebeskind, Marc; Meyer, Thomas; Bodis-Wollner, Ivan

2008-10-01

In Parkinson Disease (PD) several aspects of saccades are affected. The saccade-generating brainstem neurons are spared, however, the signals they receive may be flawed. In particular voluntary saccades suffer, but the functional anatomy of the impairment of saccade-related cortical control is unknown. We measured blood-oxygenation-level-dependent (BOLD) activation with functional Magnetic Resonance Imaging (fMRI) while healthy participants and patients with PD performed horizontal voluntary saccades between peripheral visual targets or fixated centrally. We compared saccade-related BOLD-activity vs. fixation in patients with PD and in healthy controls and correlated perisaccadic BOLD-activity in PD patients with saccade kinetics (multistep saccades). Saccade related BOLD-activation was found in both PD and healthy participants in the superior parietal cortex (PEF) and the occipital cortex. Our results suggest remarkable hypoactivity of the frontal and supplementary eye fields (FEF and SEF) in PD patients. On the other hand, PD patients showed a statistically more reliable BOLD modulation than healthy participants in the posterior cingulate gyrus, the parahippocampal gyrus, inferior parietal lobule, precuneus and in the middle temporal gyrus. Given abnormal frontal and normal PEF responses, our results suggest that in PD a frontal cortical circuitry, known to be associated with saccade planning, selection, and predicting a metric error of the saccade, is deficient.

Long-latency reductions in gamma power predict hemodynamic changes that underlie the negative BOLD signal.

PubMed

Boorman, Luke; Harris, Samuel; Bruyns-Haylett, Michael; Kennerley, Aneurin; Zheng, Ying; Martin, Chris; Jones, Myles; Redgrave, Peter; Berwick, Jason

2015-03-18

Studies that use prolonged periods of sensory stimulation report associations between regional reductions in neural activity and negative blood oxygenation level-dependent (BOLD) signaling. However, the neural generators of the negative BOLD response remain to be characterized. Here, we use single-impulse electrical stimulation of the whisker pad in the anesthetized rat to identify components of the neural response that are related to "negative" hemodynamic changes in the brain. Laminar multiunit activity and local field potential recordings of neural activity were performed concurrently with two-dimensional optical imaging spectroscopy measuring hemodynamic changes. Repeated measurements over multiple stimulation trials revealed significant variations in neural responses across session and animal datasets. Within this variation, we found robust long-latency decreases (300 and 2000 ms after stimulus presentation) in gamma-band power (30-80 Hz) in the middle-superficial cortical layers in regions surrounding the activated whisker barrel cortex. This reduction in gamma frequency activity was associated with corresponding decreases in the hemodynamic responses that drive the negative BOLD signal. These findings suggest a close relationship between BOLD responses and neural events that operate over time scales that outlast the initiating sensory stimulus, and provide important insights into the neurophysiological basis of negative neuroimaging signals. Copyright © 2015 Boorman et al.

Stimulus-induced dissociation of neuronal firing rates and local field potential gamma power and its relationship to the blood oxygen level-dependent signal in macaque primary visual cortex

PubMed Central

Bartolo, M J; Gieselmann, M A; Vuksanovic, V; Hunter, D; Sun, L; Chen, X; Delicato, L S; Thiele, A

2011-01-01

The functional magnetic resonance imaging (fMRI) blood oxygenation level-dependent (BOLD) signal is regularly used to assign neuronal activity to cognitive function. Recent analyses have shown that the local field potential (LFP) gamma power is a better predictor of the fMRI BOLD signal than spiking activity. However, LFP gamma power and spiking activity are usually correlated, clouding the analysis of the neural basis of the BOLD signal. We show that changes in LFP gamma power and spiking activity in the primary visual cortex (V1) of the awake primate can be dissociated by using grating and plaid pattern stimuli, which differentially engage surround suppression and cross-orientation inhibition/facilitation within and between cortical columns. Grating presentation yielded substantial V1 LFP gamma frequency oscillations and significant multi-unit activity. Plaid pattern presentation significantly reduced the LFP gamma power while increasing population multi-unit activity. The fMRI BOLD activity followed the LFP gamma power changes, not the multi-unit activity. Inference of neuronal activity from the fMRI BOLD signal thus requires detailed a priori knowledge of how different stimuli or tasks activate the cortical network. PMID:22081989

Rapid whole-brain resting-state fMRI at 3 T: Efficiency-optimized three-dimensional EPI versus repetition time-matched simultaneous-multi-slice EPI.

PubMed

Stirnberg, Rüdiger; Huijbers, Willem; Brenner, Daniel; Poser, Benedikt A; Breteler, Monique; Stöcker, Tony

2017-12-01

State-of-the-art simultaneous-multi-slice (SMS-)EPI and 3D-EPI share several properties that benefit functional MRI acquisition. Both sequences employ equivalent parallel imaging undersampling with controlled aliasing to achieve high temporal sampling rates. As a volumetric imaging sequence, 3D-EPI offers additional means of acceleration complementary to 2D-CAIPIRINHA sampling, such as fast water excitation and elliptical sampling. We performed an application-oriented comparison between a tailored, six-fold CAIPIRINHA-accelerated 3D-EPI protocol at 530 ms temporal and 2.4 mm isotropic spatial resolution and an SMS-EPI protocol with identical spatial and temporal resolution for whole-brain resting-state fMRI at 3 T. The latter required eight-fold slice acceleration to compensate for the lack of elliptical sampling and fast water excitation. Both sequences used vendor-supplied on-line image reconstruction. We acquired test/retest resting-state fMRI scans in ten volunteers, with simultaneous acquisition of cardiac and respiration data, subsequently used for optional physiological noise removal (nuisance regression). We found that the 3D-EPI protocol has significantly increased temporal signal-to-noise ratio throughout the brain as compared to the SMS-EPI protocol, especially when employing motion and nuisance regression. Both sequence types reliably identified known functional networks with stronger functional connectivity values for the 3D-EPI protocol. We conclude that the more time-efficient 3D-EPI primarily benefits from reduced parallel imaging noise due to a higher, actual k-space sampling density compared to SMS-EPI. The resultant BOLD sensitivity increase makes 3D-EPI a valuable alternative to SMS-EPI for whole-brain fMRI at 3 T, with voxel sizes well below 3 mm isotropic and sampling rates high enough to separate dominant cardiac signals from BOLD signals in the frequency domain. Copyright © 2017 Elsevier Inc. All rights reserved.

Rapid Training of Information Extraction with Local and Global Data Views

DTIC Science & Technology

2012-05-01

56 xiii 4.1 An example of words and their bit string representations. Bold ones are transliterated Arabic words...Natural Language Processing ( NLP ) community faces new tasks and new domains all the time. Without enough labeled data of a new task or a new domain to...conduct supervised learning, semi-supervised learning is particularly attractive to NLP researchers since it only requires a handful of labeled examples

ACHP | The United Nations Declaration on the Rights of Indigenous Peoples

Science.gov Websites

March 1, 2013, the ACHP took a bold step to adopt a plan to support the U.N. Declaration. One of the commitments in the plan is to inform the historic preservation community about the Declaration. Therefore, we announcing ACHP plan to support the Declaration ACHP Plan to Support the U.N. Declaration on the Rights of

Plans and progress for building a Great Lakes fauna DNA ...

EPA Pesticide Factsheets

DNA reference libraries provide researchers with an important tool for assessing regional biodiversity by allowing unknown genetic sequences to be assigned identities, while also providing a means for taxonomists to validate identifications. Expanding the representation of Great Lakes species in such reference libraries is an explicit component of research at EPA’s Mid-Continent Ecology Division. Our DNA reference library building efforts began in 2012 with the goal of providing barcodes for at least 5 specimens of each native and nonindigenous fish and aquatic invertebrate species currently present in the Great Lakes. The approach is to pull taxonomically validated specimen for sequencing from EPA led sampling efforts of adult/juvenile fish, larval fish, benthic macroinvertebrates, and zooplankton; while also soliciting aid from state and federal agencies for tissue from “shopping list” organisms. The barcodes we generate are made available through the publicly accessible BOLD (Barcode of Life) database, and help inform a planned Great Lakes biodiversity inventory. To date, our submissions to BOLD are limited to fishes; of the 88 fish species listed as being present within Lake Superior, roughly half were successfully barcoded, while only 22 species met the desired quota of 5 barcoded specimens per species. As we continue to generate genomic information from our collections and the taxonomic representations become more complete, we will continue to

SNR and functional sensitivity of BOLD and perfusion-based fMRI using arterial spin labeling with spiral SENSE at 3 T.

PubMed

Perthen, Joanna E; Bydder, Mark; Restom, Khaled; Liu, Thomas T

2008-05-01

Blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) studies using parallel imaging to reduce the readout window have reported a loss in temporal signal-to-noise ratio (SNR) that is less than would be expected given a purely thermal noise model. In this study, the impact of parallel imaging on the noise components and functional sensitivity of both BOLD and perfusion-based fMRI data was investigated. Dual-echo arterial spin labeling data were acquired on five subjects using sensitivity encoding (SENSE), at reduction factors (R) of 1, 2 and 3. Direct recording of cardiac and respiratory activity during data acquisition enabled the retrospective removal of physiological noise. The temporal SNR of the perfusion time series closely followed the thermal noise prediction of a radicalR loss in SNR as the readout window was shortened, with temporal SNR values (relative to the R=1 data) of 0.72 and 0.56 for the R=2 and R=3 data, respectively, after accounting for physiological noise. However, the BOLD temporal SNR decreased more slowly than predicted even after accounting for physiological noise, with relative temporal SNR values of 0.80 and 0.63 for the R=2 and R=3 data, respectively. Spectral analysis revealed that the BOLD trends were dominated by low-frequency fluctuations, which were not dominant in the perfusion data due to signal processing differences. The functional sensitivity, assessed using mean F values over activated regions of interest (ROIs), followed the temporal SNR trends for the BOLD data. However, results for the perfusion data were more dependent on the threshold used for ROI selection, most likely due to the inherently low SNR of functional perfusion data.

Mapping glucose-mediated gut-to-brain signalling pathways in humans.

PubMed

Little, Tanya J; McKie, Shane; Jones, Richard B; D'Amato, Massimo; Smith, Craig; Kiss, Orsolya; Thompson, David G; McLaughlin, John T

2014-08-01

Previous fMRI studies have demonstrated that glucose decreases the hypothalamic BOLD response in humans. However, the mechanisms underlying the CNS response to glucose have not been defined. We recently demonstrated that the slowing of gastric emptying by glucose is dependent on activation of the gut peptide cholecystokinin (CCK1) receptor. Using physiological functional magnetic resonance imaging this study aimed to determine the whole brain response to glucose, and whether CCK plays a central role. Changes in blood oxygenation level-dependent (BOLD) signal were monitored using fMRI in 12 healthy subjects following intragastric infusion (250ml) of: 1M glucose+predosing with dexloxiglumide (CCK1 receptor antagonist), 1M glucose+placebo, or 0.9% saline (control)+placebo, in a single-blind, randomised fashion. Gallbladder volume, blood glucose, insulin, and GLP-1 and CCK concentrations were determined. Hunger, fullness and nausea scores were also recorded. Intragastric glucose elevated plasma glucose, insulin, and GLP-1, and reduced gall bladder volume (an in vivo assay for CCK secretion). Glucose decreased BOLD signal, relative to saline, in the brainstem and hypothalamus as well as the cerebellum, right occipital cortex, putamen and thalamus. The timing of the BOLD signal decrease was negatively correlated with the rise in blood glucose and insulin levels. The glucose+dex arm highlighted a CCK1-receptor dependent increase in BOLD signal only in the motor cortex. Glucose induces site-specific differences in BOLD response in the human brain; the brainstem and hypothalamus show a CCK1 receptor-independent reduction which is likely to be mediated by a circulatory effect of glucose and insulin, whereas the motor cortex shows an early dexloxiglumide-reversible increase in signal, suggesting a CCK1 receptor-dependent neural pathway. Copyright © 2014. Published by Elsevier Inc.

Neural correlate of resting-state functional connectivity under α2 adrenergic receptor agonist, medetomidine.

PubMed

Nasrallah, Fatima A; Lew, Si Kang; Low, Amanda Si-Min; Chuang, Kai-Hsiang

2014-01-01

Correlative fluctuations in functional MRI (fMRI) signals across the brain at rest have been taken as a measure of functional connectivity, but the neural basis of this resting-state MRI (rsMRI) signal is not clear. Previously, we found that the α2 adrenergic agonist, medetomidine, suppressed the rsMRI correlation dose-dependently but not the stimulus evoked activation. To understand the underlying electrophysiology and neurovascular coupling, which might be altered due to the vasoconstrictive nature of medetomidine, somatosensory evoked potential (SEP) and resting electroencephalography (EEG) were measured and correlated with corresponding BOLD signals in rat brains under three dosages of medetomidine. The SEP elicited by electrical stimulation to both forepaws was unchanged regardless of medetomidine dosage, which was consistent with the BOLD activation. Identical relationship between the SEP and BOLD signal under different medetomidine dosages indicates that the neurovascular coupling was not affected. Under resting state, EEG power was the same but a depression of inter-hemispheric EEG coherence in the gamma band was observed at higher medetomidine dosage. Different from medetomidine, both resting EEG power and BOLD power and coherence were significantly suppressed with increased isoflurane level. Such reduction was likely due to suppressed neural activity as shown by diminished SEP and BOLD activation under isoflurane, suggesting different mechanisms of losing synchrony at resting-state. Even though, similarity between electrophysiology and BOLD under stimulation and resting-state implicates a tight neurovascular coupling in both medetomidine and isoflurane. Our results confirm that medetomidine does not suppress neural activity but dissociates connectivity in the somatosensory cortex. The differential effect of medetomidine and its receptor specific action supports the neuronal origin of functional connectivity and implicates the mechanism of its sedative effect. © 2013. Published by Elsevier Inc. All rights reserved.

Glutamate and GABA contributions to medial prefrontal cortical activity to emotion: implications for mood disorders.

PubMed

Stan, Ana D; Schirda, Claudiu V; Bertocci, Michele A; Bebko, Genna M; Kronhaus, Dina M; Aslam, Haris A; LaBarbara, Eduard J; Tanase, Costin; Lockovich, Jeanette C; Pollock, Myrna H; Stiffler, Richelle S; Phillips, Mary L

2014-09-30

The dorsomedial prefrontal cortex (MdPFC) and anterior cingulate cortices (ACC) play a critical role in implicit emotion regulation; however the understanding of the specific neurotransmitters that mediate such role is lacking. In this study, we examined relationships between MdPFC concentrations of two neurotransmitters, glutamate and γ-amino butyric acid (GABA), and BOLD activity in ACC during performance of an implicit facial emotion-processing task. Twenty healthy volunteers, aged 20-35 years, were scanned while performing an implicit facial emotion-processing task, whereby presented facial expressions changed from neutral to one of the four emotions: happy, anger, fear, or sad. Glutamate concentrations were measured before and after the emotion-processing task in right MdPFC using magnetic resonance spectroscopy (MRS). GABA concentrations were measured in bilateral MdPFC after the emotion-processing task. Multiple regression models were run to determine the relative contribution of glutamate and GABA concentration, age, and gender to BOLD signal in ACC to each of the four emotions. Multiple regression analyses revealed a significant negative correlation between MdPFC GABA concentration and BOLD signal in subgenual ACC (p<0.05, corrected) to sad versus shape contrast. For the anger versus shape contrast, there was a significant negative correlation between age and BOLD signal in pregenual ACC (p<0.05, corrected) and a positive correlation between MdPFC glutamate concentration (pre-task) and BOLD signal in pregenual ACC (p<0.05, corrected). Our findings are the first to provide insight into relationships between MdPFC neurotransmitter concentrations and ACC BOLD signal, and could further understanding of molecular mechanisms underlying emotion processing in healthy and mood-disordered individuals. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

The role of beta-arrestin2 in shaping fMRI BOLD responses to dopaminergic stimulation.

PubMed

Sahlholm, Kristoffer; Ielacqua, Giovanna D; Xu, Jinbin; Jones, Lynne A; Schlegel, Felix; Mach, Robert H; Rudin, Markus; Schroeter, Aileen

2017-07-01

The dopamine D 2 receptor (D 2 R) couples to inhibitory G i/o proteins and is targeted by antipsychotic and antiparkinsonian drugs. Beta-arrestin2 binds to the intracellular regions of the agonist-occupied D 2 R to terminate G protein activation and promote internalization, but also to initiate downstream signaling cascades which have been implicated in psychosis. Functional magnetic resonance imaging (fMRI) has proven valuable for measuring dopamine receptor-mediated changes in neuronal activity, and might enable beta-arrestin2 function to be studied in vivo. The present study examined fMRI blood oxygenation level dependent (BOLD) signal changes elicited by a dopamine agonist in wild-type (WT) and beta-arrestin2 knockout (KO) mice, to investigate whether genetic deletion of beta-arrestin2 prolongs or otherwise modifies D 2 R-dependent responses. fMRI BOLD data were acquired on a 9.4 T system. During scans, animals received 0.2 mg/kg apomorphine, i.v. In a subset of experiments, animals were pretreated with 2 mg/kg of the D 2 R antagonist, eticlopride. Following apomorphine administration, BOLD signal decreases were observed in caudate/putamen of WT and KO animals. The time course of response decay in caudate/putamen was significantly slower in KO vs. WT animals. In cingulate cortex, an initial BOLD signal decrease was followed by a positive response component in WT but not in KO animals. Eticlopride pretreatment significantly reduced apomorphine-induced BOLD signal changes. The prolonged striatal response decay rates in KO animals might reflect impaired D 2 R desensitization, consistent with the known function of beta-arrestin2. Furthermore, the apomorphine-induced positive response component in cingulate cortex may depend on beta-arrestin2 signaling downstream of D 2 R.

Amphetamine modulates brain signal variability and working memory in younger and older adults.

PubMed

Garrett, Douglas D; Nagel, Irene E; Preuschhof, Claudia; Burzynska, Agnieszka Z; Marchner, Janina; Wiegert, Steffen; Jungehülsing, Gerhard J; Nyberg, Lars; Villringer, Arno; Li, Shu-Chen; Heekeren, Hauke R; Bäckman, Lars; Lindenberger, Ulman

2015-06-16

Better-performing younger adults typically express greater brain signal variability relative to older, poorer performers. Mechanisms for age and performance-graded differences in brain dynamics have, however, not yet been uncovered. Given the age-related decline of the dopamine (DA) system in normal cognitive aging, DA neuromodulation is one plausible mechanism. Hence, agents that boost systemic DA [such as d-amphetamine (AMPH)] may help to restore deficient signal variability levels. Furthermore, despite the standard practice of counterbalancing drug session order (AMPH first vs. placebo first), it remains understudied how AMPH may interact with practice effects, possibly influencing whether DA up-regulation is functional. We examined the effects of AMPH on functional-MRI-based blood oxygen level-dependent (BOLD) signal variability (SD(BOLD)) in younger and older adults during a working memory task (letter n-back). Older adults expressed lower brain signal variability at placebo, but met or exceeded young adult SD(BOLD) levels in the presence of AMPH. Drug session order greatly moderated change-change relations between AMPH-driven SD(BOLD) and reaction time means (RT(mean)) and SDs (RT(SD)). Older adults who received AMPH in the first session tended to improve in RT(mean) and RT(SD) when SD(BOLD) was boosted on AMPH, whereas younger and older adults who received AMPH in the second session showed either a performance improvement when SD(BOLD) decreased (for RT(mean)) or no effect at all (for RT(SD)). The present findings support the hypothesis that age differences in brain signal variability reflect aging-induced changes in dopaminergic neuromodulation. The observed interactions among AMPH, age, and session order highlight the state- and practice-dependent neurochemical basis of human brain dynamics.

A Comparison of Measures of Boldness and Their Relationships to Survival in Young Fish

PubMed Central

White, James R.; Meekan, Mark G.; McCormick, Mark I.; Ferrari, Maud C. O.

2013-01-01

Boldness is the propensity of an animal to engage in risky behavior. Many variations of novel-object or novel-environment tests have been used to quantify the boldness of animals, although the relationship between test outcomes has rarely been investigated. Furthermore, the relationship of outcomes to any ecological aspect of fitness is generally assumed, rather than measured directly. Our study is the first to compare how the outcomes of the same test of boldness differ among observers and how different tests of boldness relate to the survival of individuals in the field. Newly-metamorphosed lemon damselfish, Pomacentrus moluccensis, were placed onto replicate patches of natural habitat. Individual behavior was quantified using four tests (composed of a total of 12 different measures of behavior): latency to enter a novel environment, activity in a novel environment, and reactions to threatening and benign novel objects. After behavior was quantified, survival was monitored for two days during which time fish were exposed to natural predators. Variation among observers was low for most of the 12 measures, except distance moved and the threat test (reaction to probe thrust), which displayed unacceptable amounts of inter-observer variation. Overall, the results of the behavioral tests suggested that novel environment and novel object tests quantified similar behaviors, yet these behavioral measures were not interchangeable. Multiple measures of behavior within the context of novel environment or object tests were the most robust way to assess boldness and these measures have a complex relationship with survivorship of young fish in the field. Body size and distance ventured from shelter were the only variables that had a direct and positive relationship with survival. PMID:23874804

Boldness by habituation and social interactions: a model.

PubMed

Oosten, Johanneke E; Magnhagen, Carin; Hemelrijk, Charlotte K

2010-04-01

Most studies of animal personality attribute personality to genetic traits. But a recent study by Magnhagen and Staffan (Behav Ecol Sociobiol 57:295-303, 2005) on young perch in small groups showed that boldness, a central personality trait, is also shaped by social interactions and by previous experience. The authors measured boldness by recording the duration that an individual spent near a predator and the speed with which it fed there. They found that duration near the predator increased over time and was higher the higher the average boldness of other group members. In addition, the feeding rate of shy individuals was reduced if other members of the same group were bold. The authors supposed that these behavioral dynamics were caused by genetic differences, social interactions, and habituation to the predator. However, they did not quantify exactly how this could happen. In the present study, we therefore use an agent-based model to investigate whether these three factors may explain the empirical findings. We choose an agent-based model because this type of model is especially suited to study the relation between behavior at an individual level and behavioral dynamics at a group level. In our model, individuals were either hiding in vegetation or feeding near a predator, whereby their behavior was affected by habituation and by two social mechanisms: social facilitation to approach the predator and competition over food. We show that even if we start the model with identical individuals, these three mechanisms were sufficient to reproduce the behavioral dynamics of the empirical study, including the consistent differences among individuals. Moreover, if we start the model with individuals that already differ in boldness, the behavioral dynamics produced remained the same. Our results indicate the importance of previous experience and social interactions when studying animal personality empirically.

A comparison of measures of boldness and their relationships to survival in young fish.

PubMed

White, James R; Meekan, Mark G; McCormick, Mark I; Ferrari, Maud C O

2013-01-01

Boldness is the propensity of an animal to engage in risky behavior. Many variations of novel-object or novel-environment tests have been used to quantify the boldness of animals, although the relationship between test outcomes has rarely been investigated. Furthermore, the relationship of outcomes to any ecological aspect of fitness is generally assumed, rather than measured directly. Our study is the first to compare how the outcomes of the same test of boldness differ among observers and how different tests of boldness relate to the survival of individuals in the field. Newly-metamorphosed lemon damselfish, Pomacentrus moluccensis, were placed onto replicate patches of natural habitat. Individual behavior was quantified using four tests (composed of a total of 12 different measures of behavior): latency to enter a novel environment, activity in a novel environment, and reactions to threatening and benign novel objects. After behavior was quantified, survival was monitored for two days during which time fish were exposed to natural predators. Variation among observers was low for most of the 12 measures, except distance moved and the threat test (reaction to probe thrust), which displayed unacceptable amounts of inter-observer variation. Overall, the results of the behavioral tests suggested that novel environment and novel object tests quantified similar behaviors, yet these behavioral measures were not interchangeable. Multiple measures of behavior within the context of novel environment or object tests were the most robust way to assess boldness and these measures have a complex relationship with survivorship of young fish in the field. Body size and distance ventured from shelter were the only variables that had a direct and positive relationship with survival.

Risky business: Changes in boldness behavior in male Siamese fighting fish, Betta splendens, following exposure to an antiandrogen.

PubMed

Dzieweczynski, Teresa L; Portrais, Kelley B; Stevens, Megan A; Kane, Jessica L; Lawrence, Jaslynn M

2018-04-01

Components of boldness, such as activity level and locomotion, influence an individual's ability to avoid predators and acquire resources, generating fitness consequences. The presence of endocrine disrupting chemicals (EDCs) in the aquatic environment may affect fitness by changing morphology or altering behaviors like courtship and exploration. Most research on EDC-generated behavioral effects has focused on estrogen mimics and reproductive endpoints. Far fewer studies have examined the effects of other types of EDCs or measured non-reproductive behaviors. EDCs with antiandrogenic properties are present in waterways yet we know little about their effects on exposed individuals although they may produce effects similar to those caused by estrogen mimics because they act on the same hormonal pathway. To examine the effects of antiandrogens on boldness, this study exposed male Siamese fighting fish, Betta splendens, to a high or low dose of one of two antiandrogens, vinclozolin or flutamide, and observed behavior in three boldness assays, both before and after exposure. Overall, antiandrogen exposure increased boldness behavior, especially following exposure to the higher dose. Whether or not antiandrogen exposure influenced boldness, as well as the nature and intensity of the effect, was assay-dependent. This demonstrates the importance of studying EDC effects in a range of contexts and, at least within this species, suggests that antiandrogenic compounds may generate distinct physiological effects in different situations. How and why the behavioral effects differ from those caused by exposure to an estrogen mimic, as well as the potential consequences of increased activity levels, are discussed. Exposure to an antiandrogen, regardless of dose, produced elevated activity levels and altered shoaling and exploration in male Siamese fighting fish. These modifications may have fitness consequences. Copyright © 2018 Elsevier Ltd. All rights reserved.

Non-linear Relationship between BOLD Activation and Amplitude of Beta Oscillations in the Supplementary Motor Area during Rhythmic Finger Tapping and Internal Timing

PubMed Central

Gompf, Florian; Pflug, Anja; Laufs, Helmut; Kell, Christian A.

2017-01-01

Functional imaging studies using BOLD contrasts have consistently reported activation of the supplementary motor area (SMA) both during motor and internal timing tasks. Opposing findings, however, have been shown for the modulation of beta oscillations in the SMA. While movement suppresses beta oscillations in the SMA, motor and non-motor tasks that rely on internal timing increase the amplitude of beta oscillations in the SMA. These independent observations suggest that the relationship between beta oscillations and BOLD activation is more complex than previously thought. Here we set out to investigate this rapport by examining beta oscillations in the SMA during movement with varying degrees of internal timing demands. In a simultaneous EEG-fMRI experiment, 20 healthy right-handed subjects performed an auditory-paced finger-tapping task. Internal timing was operationalized by including conditions with taps on every fourth auditory beat, which necessitates generation of a slow internal rhythm, while tapping to every auditory beat reflected simple auditory-motor synchronization. In the SMA, BOLD activity increased and power in both the low and the high beta band decreased expectedly during each condition compared to baseline. Internal timing was associated with a reduced desynchronization of low beta oscillations compared to conditions without internal timing demands. In parallel with this relative beta power increase, internal timing activated the SMA more strongly in terms of BOLD. This documents a task-dependent non-linear relationship between BOLD and beta-oscillations in the SMA. We discuss different roles of beta synchronization and desynchronization in active processing within the same cortical region. PMID:29249950

Parietal blood oxygenation level-dependent response evoked by covert visual search reflects set-size effect in monkeys.

PubMed

Atabaki, A; Marciniak, K; Dicke, P W; Karnath, H-O; Thier, P

2014-03-01

Distinguishing a target from distractors during visual search is crucial for goal-directed behaviour. The more distractors that are presented with the target, the larger is the subject's error rate. This observation defines the set-size effect in visual search. Neurons in areas related to attention and eye movements, like the lateral intraparietal area (LIP) and frontal eye field (FEF), diminish their firing rates when the number of distractors increases, in line with the behavioural set-size effect. Furthermore, human imaging studies that have tried to delineate cortical areas modulating their blood oxygenation level-dependent (BOLD) response with set size have yielded contradictory results. In order to test whether BOLD imaging of the rhesus monkey cortex yields results consistent with the electrophysiological findings and, moreover, to clarify if additional other cortical regions beyond the two hitherto implicated are involved in this process, we studied monkeys while performing a covert visual search task. When varying the number of distractors in the search task, we observed a monotonic increase in error rates when search time was kept constant as was expected if monkeys resorted to a serial search strategy. Visual search consistently evoked robust BOLD activity in the monkey FEF and a region in the intraparietal sulcus in its lateral and middle part, probably involving area LIP. Whereas the BOLD response in the FEF did not depend on set size, the LIP signal increased in parallel with set size. These results demonstrate the virtue of BOLD imaging in monkeys when trying to delineate cortical areas underlying a cognitive process like visual search. However, they also demonstrate the caution needed when inferring neural activity from BOLD activity. © 2013 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

Investigating the neural bases for intra-subject cognitive efficiency changes using functional magnetic resonance imaging

PubMed Central

Rao, Neena K.; Motes, Michael A.; Rypma, Bart

2014-01-01

Several fMRI studies have examined brain regions mediating inter-subject variability in cognitive efficiency, but none have examined regions mediating intra-subject variability in efficiency. Thus, the present study was designed to identify brain regions involved in intra-subject variability in cognitive efficiency via participant-level correlations between trial-level reaction time (RT) and trial-level fMRI BOLD percent signal change on a processing speed task. On each trial, participants indicated whether a digit-symbol probe-pair was present or absent in an array of nine digit-symbol probe-pairs while fMRI data were collected. Deconvolution analyses, using RT time-series models (derived from the proportional scaling of an event-related hemodynamic response function model by trial-level RT), were used to evaluate relationships between trial-level RTs and BOLD percent signal change. Although task-related patterns of activation and deactivation were observed in regions including bilateral occipital, bilateral parietal, portions of the medial wall such as the precuneus, default mode network regions including anterior cingulate, posterior cingulate, bilateral temporal, right cerebellum, and right cuneus, RT-BOLD correlations were observed in a more circumscribed set of regions. Positive RT-BOLD correlations, where fast RTs were associated with lower BOLD percent signal change, were observed in regions including bilateral occipital, bilateral parietal, and the precuneus. RT-BOLD correlations were not observed in the default mode network indicating a smaller set of regions associated with intra-subject variability in cognitive efficiency. The results are discussed in terms of a distributed area of regions that mediate variability in the cognitive efficiency that might underlie processing speed differences between individuals. PMID:25374527

Investigating the neural bases for intra-subject cognitive efficiency changes using functional magnetic resonance imaging.

PubMed

Rao, Neena K; Motes, Michael A; Rypma, Bart

2014-01-01

Several fMRI studies have examined brain regions mediating inter-subject variability in cognitive efficiency, but none have examined regions mediating intra-subject variability in efficiency. Thus, the present study was designed to identify brain regions involved in intra-subject variability in cognitive efficiency via participant-level correlations between trial-level reaction time (RT) and trial-level fMRI BOLD percent signal change on a processing speed task. On each trial, participants indicated whether a digit-symbol probe-pair was present or absent in an array of nine digit-symbol probe-pairs while fMRI data were collected. Deconvolution analyses, using RT time-series models (derived from the proportional scaling of an event-related hemodynamic response function model by trial-level RT), were used to evaluate relationships between trial-level RTs and BOLD percent signal change. Although task-related patterns of activation and deactivation were observed in regions including bilateral occipital, bilateral parietal, portions of the medial wall such as the precuneus, default mode network regions including anterior cingulate, posterior cingulate, bilateral temporal, right cerebellum, and right cuneus, RT-BOLD correlations were observed in a more circumscribed set of regions. Positive RT-BOLD correlations, where fast RTs were associated with lower BOLD percent signal change, were observed in regions including bilateral occipital, bilateral parietal, and the precuneus. RT-BOLD correlations were not observed in the default mode network indicating a smaller set of regions associated with intra-subject variability in cognitive efficiency. The results are discussed in terms of a distributed area of regions that mediate variability in the cognitive efficiency that might underlie processing speed differences between individuals.

Consolidation of Complex Events via Reinstatement in Posterior Cingulate Cortex.

PubMed

Bird, Chris M; Keidel, James L; Ing, Leslie P; Horner, Aidan J; Burgess, Neil

2015-10-28

It is well-established that active rehearsal increases the efficacy of memory consolidation. It is also known that complex events are interpreted with reference to prior knowledge. However, comparatively little attention has been given to the neural underpinnings of these effects. In healthy adults humans, we investigated the impact of effortful, active rehearsal on memory for events by showing people several short video clips and then asking them to recall these clips, either aloud (Experiment 1) or silently while in an MRI scanner (Experiment 2). In both experiments, actively rehearsed clips were remembered in far greater detail than unrehearsed clips when tested a week later. In Experiment 1, highly similar descriptions of events were produced across retrieval trials, suggesting a degree of semanticization of the memories had taken place. In Experiment 2, spatial patterns of BOLD signal in medial temporal and posterior midline regions were correlated when encoding and rehearsing the same video. Moreover, the strength of this correlation in the posterior cingulate predicted the amount of information subsequently recalled. This is likely to reflect a strengthening of the representation of the video's content. We argue that these representations combine both new episodic information and stored semantic knowledge (or "schemas"). We therefore suggest that posterior midline structures aid consolidation by reinstating and strengthening the associations between episodic details and more generic schematic information. This leads to the creation of coherent memory representations of lifelike, complex events that are resistant to forgetting, but somewhat inflexible and semantic-like in nature. Copyright © 2015 Bird, Keidel et al.

Clinical utility of BOLD fMRI in preoperative work-up of epilepsy

PubMed Central

Ganesan, Karthik; Ursekar, Meher

2014-01-01

Surgical techniques have emerged as a viable therapeutic option in patients with drug refractory epilepsy. Pre-surgical evaluation of epilepsy requires a comprehensive, multiparametric, and multimodal approach for precise localization of the epileptogenic focus. Various non-invasive techniques are available at the disposal of the treating physician to detect the epileptogenic focus, which include electroencephalography (EEG), video-EEG, magnetic resonance imaging (MRI), functional MRI including blood oxygen level dependent (BOLD) techniques, single photon emission tomography (SPECT), and 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET). Currently, non-invasive high-resolution MR imaging techniques play pivotal roles in the preoperative detection of the seizure focus, and represent the foundation for successful epilepsy surgery. BOLD functional magnetic resonance imaging (fMRI) maps allow for precise localization of the eloquent cortex in relation to the seizure focus. This review article focuses on the clinical utility of BOLD (fMRI) in the pre-surgical work-up of epilepsy patients. PMID:24851002

Asymptotic properties of a bold random walk

NASA Astrophysics Data System (ADS)

Serva, Maurizio

2014-08-01

In a recent paper we proposed a non-Markovian random walk model with memory of the maximum distance ever reached from the starting point (home). The behavior of the walker is different from the simple symmetric random walk only when she is at this maximum distance, where, having the choice to move either farther or closer, she decides with different probabilities. If the probability of a forward step is higher than the probability of a backward step, the walker is bold and her behavior turns out to be superdiffusive; otherwise she is timorous and her behavior turns out to be subdiffusive. The scaling behavior varies continuously from subdiffusive (timorous) to superdiffusive (bold) according to a single parameter γ ∈R. We investigate here the asymptotic properties of the bold case in the nonballistic region γ ∈[0,1/2], a problem which was left partially unsolved previously. The exact results proved in this paper require new probabilistic tools which rely on the construction of appropriate martingales of the random walk and its hitting times.

Deficient aversive-potentiated startle and the triarchic model of psychopathy: The role of boldness.

PubMed

Esteller, Àngels; Poy, Rosario; Moltó, Javier

2016-05-01

This study examined the contribution of the phenotypic domains of boldness, meanness, and disinhibition of the triarchic conceptualization of psychopathy (Patrick, Fowles, & Krueger, 2009) to deficient aversive-potentiated startle in a mixed-gender sample of 180 undergraduates. Eyeblink responses to noise probes were recorded during a passive picture-viewing task (erotica, neutral, threat, and mutilation). Deficient threat vs. neutral potentiation was uniquely related to increased boldness scores, thus suggesting that the diminished defensive reaction to aversive stimulation is specifically linked to the charm, social potency and venturesomeness features of psychopathy (boldness), but not to features such as callousness, coldheartedness and cruelty traits (meanness), even though both phenotypes theoretically share the same underlying low-fear disposition. Our findings provide further evidence of the differential association between distinct psychopathy components and deficits in defensive reactivity and strongly support the validity of the triarchic model of psychopathy in disentangling the etiology of this personality disorder. Copyright © 2016 Elsevier B.V. All rights reserved.

Identifying Childhood Characteristics that Underlie Pre-Morbid Risk for Substance Use Disorders: Socialization and Boldness

PubMed Central

Hicks, Brian M.; Iacono, William G.; McGue, Matt

2013-01-01

Utilizing a longitudinal twin study (N = 2510), we identified the child characteristics present prior to initiation of substance use that best predicted later substance use disorders. Two independent traits accounted for the majority of pre-morbid risk: socialization (conformity to rules and conventional values) and boldness (sociability and social assurance, stress resilience, and thrill seeking). Low socialization was associated with disruptive behavior disorders, parental externalizing disorders, and environmental adversity, and exhibited moderate genetic (.45) and shared environmental influences (.30). Boldness was highly heritable (.71) and associated with less internalizing distress and environmental adversity. Together, these traits exhibited robust associations with adolescent and young adult substance use disorders (R = .48 and .50, respectively), and incremental prediction over disruptive behavior disorders, parental externalizing disorders, and environmental adversity. Results were replicated in an independent sample. Socialization and boldness offer a novel conceptualization of underlying risk for substance use disorders that has the potential to improve prediction and theory with implications for basic research, prevention, and intervention. PMID:24280373

Fluoxetine exposure impacts boldness in female Siamese fighting fish, Betta splendens.

PubMed

Dzieweczynski, Teresa L; Kane, Jessica L; Campbell, Brennah A; Lavin, Lindsey E

2016-01-01

The present study examined the effects of the selective serotonin reuptake inhibitor, fluoxetine, on the behavior of female Siamese fighting fish, Betta splendens, in three different boldness assays (Empty Tank, Novel Environment, Social Tendency). When females were unexposed to fluoxetine, boldness was consistent within a context and correlated across assays. Fluoxetine exposure affected behavior within and among individuals on multiple levels. Exposure reduced overall boldness levels, made females behave in a less consistent manner, and significantly reduced correlations over time and across contexts. Fluoxetine exerted its effects on female Betta splendens behavior in a dose-dependent fashion and these effects persisted even after females were housed in clean water. If fluoxetine exposure impacts behaviors such as exploration that are necessary to an individual’s success, this may yield evolutionary consequences. In conclusion, the results show that fluoxetine exposure alters behavior beyond the level of overall response and highlights the importance of studying the behavioral effects of inadvertent pharmaceutical exposure in multiple contexts and with different dosing regimes.

Identifying childhood characteristics that underlie premorbid risk for substance use disorders: socialization and boldness.

PubMed

Hicks, Brian M; Iacono, William G; McGue, Matt

2014-02-01

We utilized a longitudinal twin study (N = 2,510) to identify the child characteristics present prior to initiation of substance use that best predicted later substance use disorders. Two independent traits accounted for the majority of premorbid risk: socialization (conformity to rules and conventional values) and boldness (sociability and social assurance, stress resilience, and thrill seeking). Low socialization was associated with disruptive behavior disorders, parental externalizing disorders, and environmental adversity and exhibited moderate genetic (0.45) and shared environmental influences (0.30). Boldness was highly heritable (0.71) and associated with less internalizing distress and environmental adversity. In combination, these traits exhibited robust associations with adolescent and young adult substance use disorders (R = .48 and .50, respectively) and incremental prediction over disruptive behavior disorders, parental externalizing disorders, and environmental adversity. The results were replicated in an independent sample. Socialization and boldness offer a novel conceptualization of underlying risk for substance use disorders that has the potential to improve prediction and theory with implications for basic research, prevention, and intervention.

SU-E-J-223: A BOLD Contrast Imaging Sequence to Evaluate Oxygenation Changes Due to Breath Holding for Breast Radiotherapy: A Pilot Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adamson, J; Chang, Z; Cai, J

Purpose: To develop a robust MRI sequence to measure BOLD breath hold induced contrast in context of breast radiotherapy. Methods: Two sequences were selected from prior studies as candidates to measure BOLD contrast attributable to breath holding within the breast: (1) T2* based Gradient Echo EPI (TR/TE = 500/41ms, flip angle = 60°), and (2) T2 based Single Shot Fast Spin Echo (SSFSE) (TR/TE = 3000/60ms). We enrolled ten women post-lumpectomy for breast cancer who were undergoing treatment planning for whole breast radiotherapy. Each session utilized a 1.5T GE MRI and 4 channel breast coil with the subject immobilized pronemore » on a custom board. For each sequence, 1–3 planes of the lumpectomy breast were imaged continuously during a background measurement (1min) and intermittent breath holds (20–40s per breath hold, 3–5 holds per sequence). BOLD contrast was quantified as correlation of changes in per-pixel intensity with the breath hold schedule convolved with a hemodynamic response function. Subtle motion was corrected using a deformable registration algorithm. Correlation with breath-holding was considered significant if p<0.001. Results: The percentage of the breast ROI with positive BOLD contrast measured by the two sequences were in agreement with a correlation coefficient of R=0.72 (p=0.02). While both sequences demonstrated areas with strong BOLD response, the response was more systematic throughout the breast for the SSFSE (T2) sequence (% breast with response in the same direction: 51.2%±0.7% for T2* vs. 68.1%±16% for T2). In addition, the T2 sequence was less prone to magnetic susceptibility artifacts, especially in presence of seroma, and provided a more robust image with little distortion or artifacts. Conclusion: A T2 SSFSE sequence shows promise for measuring BOLD contrast in the context of breast radiotherapy utilizing a breath hold technique. Further study in a larger patient cohort is warranted to better refine this novel technique.« less

Magnetic Resonance Imaging-Derived Renal Oxygenation and Perfusion During Continuous, Steady-State Angiotensin-II Infusion in Healthy Humans.

PubMed

van der Bel, René; Coolen, Bram F; Nederveen, Aart J; Potters, Wouter V; Verberne, Hein J; Vogt, Liffert; Stroes, Erik S G; Krediet, C T Paul

2016-03-28

The role of kidney hypoxia is considered pivotal in the progression of chronic kidney disease. A widely used method to assess kidney oxygenation is blood oxygen level dependent (BOLD)-magnetic resonance imaging (MRI), but its interpretation remains problematic. The BOLD-MRI signal is the result of kidney oxygen consumption (a proxy of glomerular filtration) and supply (ie, glomerular perfusion). Therefore, we hypothesized that with pharmacological modulation of kidney blood flow, renal oxygenation, as assessed by BOLD-MRI, correlates to filtration fraction (ie, glomerular filtration rate/effective renal plasma flow) in healthy humans. Eight healthy volunteers were subjected to continuous angiotensin-II infusion at 0.3, 0.9, and 3.0 ng/kg per minute. At each dose, renal oxygenation and blood flow were assessed using BOLD and phase-contrast MRI. Subsequently, "gold standard" glomerular filtration rate/effective renal plasma flow measurements were performed under the same conditions. Renal plasma flow decreased dose dependently from 660±146 to 467±103 mL/min per 1.73 m(2) (F[3, 21]=33.3, P<0.001). Glomerular filtration rate decreased from 121±23 to 110±18 mL/min per 1.73 m(2) (F[1.8, 2.4]=6.4, P=0.013). Cortical transverse relaxation rate (R2*; increases in R2* represent decreases in oxygenation) increased by 7.2±3.8% (F[3, 21]=7.37, P=0.001); medullar R2* did not change. Cortical R2* related to filtration fraction (R(2) 0.46, P<0.001). By direct comparison between "gold standard" kidney function measurements and BOLD MRI, we showed that cortical oxygenation measured by BOLD MRI relates poorly to glomerular filtration rate but is associated with filtration fraction. For future studies, there may be a need to include renal plasma flow measurements when employing renal BOLD-MRI. © 2016 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.

Bold Diagrammatic Monte Carlo for Fermionic and Fermionized Systems

NASA Astrophysics Data System (ADS)

Svistunov, Boris

2013-03-01

In three different fermionic cases--repulsive Hubbard model, resonant fermions, and fermionized spins-1/2 (on triangular lattice)--we observe the phenomenon of sign blessing: Feynman diagrammatic series features finite convergence radius despite factorial growth of the number of diagrams with diagram order. Bold diagrammatic Monte Carlo technique allows us to sample millions of skeleton Feynman diagrams. With the universal fermionization trick we can fermionize essentially any (bosonic, spin, mixed, etc.) lattice system. The combination of fermionization and Bold diagrammatic Monte Carlo yields a universal first-principle approach to strongly correlated lattice systems, provided the sign blessing is a generic fermionic phenomenon. Supported by NSF and DARPA

21 CFR Appendix A to Part 201 - Examples of Graphic Enhancements Used by FDA

Code of Federal Regulations, 2010 CFR

2010-04-01

... (e.g., “Ask a doctor or pharmacist before use if you are”) are set in 6 point Helvetica Bold, left... doctor or pharmacist before use if you are”) are set in 6 point Helvetica Bold, left justified. 4. The...

21 CFR Appendix A to Part 201 - Examples of Graphic Enhancements Used by FDA

Code of Federal Regulations, 2013 CFR

2013-04-01

... (e.g., “Ask a doctor or pharmacist before use if you are”) are set in 6 point Helvetica Bold, left... doctor or pharmacist before use if you are”) are set in 6 point Helvetica Bold, left justified. 4. The...

21 CFR Appendix A to Part 201 - Examples of Graphic Enhancements Used by FDA

Code of Federal Regulations, 2011 CFR

2011-04-01

... (e.g., “Ask a doctor or pharmacist before use if you are”) are set in 6 point Helvetica Bold, left... doctor or pharmacist before use if you are”) are set in 6 point Helvetica Bold, left justified. 4. The...

21 CFR Appendix A to Part 201 - Examples of Graphic Enhancements Used by FDA

Code of Federal Regulations, 2012 CFR

2012-04-01

... (e.g., “Ask a doctor or pharmacist before use if you are”) are set in 6 point Helvetica Bold, left... doctor or pharmacist before use if you are”) are set in 6 point Helvetica Bold, left justified. 4. The...

21 CFR Appendix A to Part 201 - Examples of Graphic Enhancements Used by FDA

Code of Federal Regulations, 2014 CFR

2014-04-01

... (e.g., “Ask a doctor or pharmacist before use if you are”) are set in 6 point Helvetica Bold, left... doctor or pharmacist before use if you are”) are set in 6 point Helvetica Bold, left justified. 4. The...

Left fusiform BOLD responses are inversely related to word-likeness in a one-back task.

PubMed

Wang, Xiaojuan; Yang, Jianfeng; Shu, Hua; Zevin, Jason D

2011-04-01

Although its precise functional contribution to reading remains unclear, there is broad consensus that an activity in the left mid-fusiform gyrus is highly sensitive to written words and word-like stimuli. In the current study, we take advantage of a particularity of the Chinese writing system in order to manipulate word-likeness parametrically, from real characters, to pseudo-characters that vary in whether they contain phonological and semantic cues, to artificial stimuli with varying surface similarity to real characters. In a one-back task, BOLD activity in the left mid-fusiform was inversely related to word-likeness, such that the least activity was observed in response to real characters, and the greatest to artificial stimuli that violate the orthotactic constraints of the writing system. One possible explanation for this surprising result is that the short-term memory demands of the one-back task put more pressure on the visual system when other sources of information cannot be used to aid in detecting repeated stimuli. For real characters and, to a lesser extent for pseudo-characters, information about meaning and pronunciation can contribute to performance, whereas artificial stimuli are entirely dependent on visual information. Consistent with this view, functional connectivity analyses revealed a strong positive relationship between left mid-fusiform and other visual areas, whereas areas typically involved in phonological and semantic processing for text were negatively correlated with this region. Copyright © 2011 Elsevier Inc. All rights reserved.

Influence of DARPP-32 genetic variation on BOLD activation to happy faces.

PubMed

Persson, Ninni; Lavebratt, Catarina; Ebner, Natalie C; Fischer, Håkan

2017-10-01

Dopaminergic pathways play a crucial role in reward processing, and advanced age can modulate its efficiency. DARPP-32 controls dopaminergic function and is a chemical nexus of reward processing. In 61 younger (20-30 years) and older adults (54% ♀) (65-74 years), we examined how blood-oxygen-level dependent (BOLD) activation to emotional faces, vary over genotypes at three single nucleotide polymorphism (SNPs), coding for DARPP-32 (rs879606; rs907094; 3764352). We also assessed age-magnification of DARPP-32 effects on BOLD activation. We found that major homozygote G, T or A genotypes, with higher cortical expression of DARPP-32, higher dopamine receptor efficacy, and greater bias toward positive cues, had increased functional connectivity in cortical-subcortical circuits in response to happy faces, engaging the dorsal prefrontal cortex (DLPFC), fusiform gyrus (FG) and the midbrain (MB). Local BOLD response to happy faces in FG, and MB was age-dependent, so that older carriers of the major G, T or A alleles showed lesser activation than minor genotypes. These genetic variants of DARPP-32 did not modulate BOLD response to angry faces, or engagement of the inferior occipital gyrus, to happy or angry faces. Taken together our results lend support for a potential role of DARPP-32 genetic variants in neural response to potential reward triggering cues. © The Author (2017). Published by Oxford University Press.

Changing body temperature affects the T2* signal in the rat brain and reveals hypothalamic activity.

PubMed

Vanhoutte, G; Verhoye, M; Van der Linden, A

2006-05-01

This study was designed to determine brain activity in the hypothalamus-in particular the thermoregulatory function of the hypothalamic preoptic area (PO). We experimentally changed the body temperature in rats within the physiological range (37-39 degrees C) and monitored changes in blood oxygenation level-dependent (BOLD) MR signal. To explore PO activity we had to deal with general signal changes caused by temperature-dependent alterations in the affinity of oxygen for hemoglobin, which contributes to BOLD contrast because it is partly sensitive to the amount of paramagnetic deoxyhemoglobin in the voxel. To reduce these overall temperature-induced effects, we corrected the BOLD data using brain-specific correction algorithms. The results showed activity of the PO during body warming from 38 degrees C to 39 degrees C, supported by an increased BOLD signal after correction. This is the first fMRI study on the autonomous nervous system in which hypothalamic activity elicited by changes in the internal environment (body temperature) was monitored. In this study we also demonstrate 1) that any fMRI study of anesthetized small animals should guard against background BOLD signal drift, since animals are vulnerable to body temperature fluctuations; and 2) the existence of a link between PO activity and the sympathetically-mediated opening of the arteriovenous anastomoses in a parallel study on the rat tail, a peripheral thermoregulatory organ.

Associations of resting-state fMRI functional connectivity with flow-BOLD coupling and regional vasculature.

PubMed

Tak, Sungho; Polimeni, Jonathan R; Wang, Danny J J; Yan, Lirong; Chen, J Jean

2015-04-01

There has been tremendous interest in applying functional magnetic resonance imaging-based resting-state functional connectivity (rs-fcMRI) measurements to the study of brain function. However, a lack of understanding of the physiological mechanisms of rs-fcMRI limits their ability to interpret rs-fcMRI findings. In this work, the authors examine the regional associations between rs-fcMRI estimates and dynamic coupling between the blood oxygenation level-dependent (BOLD) and cerebral blood flow (CBF), as well as resting macrovascular volume. Resting-state BOLD and CBF data were simultaneously acquired using a dual-echo pseudocontinuous arterial spin labeling (pCASL) technique, whereas macrovascular volume fraction was estimated using time-of-flight MR angiography. Functional connectivity within well-known functional networks—including the default mode, frontoparietal, and primary sensory-motor networks—was calculated using a conventional seed-based correlation approach. They found the functional connectivity strength to be significantly correlated with the regional increase in CBF-BOLD coupling strength and inversely proportional to macrovascular volume fraction. These relationships were consistently observed within all functional networks considered. Their findings suggest that highly connected networks observed using rs-fcMRI are not likely to be mediated by common vascular drainage linking distal cortical areas. Instead, high BOLD functional connectivity is more likely to reflect tighter neurovascular connections, attributable to neuronal pathways.

Brain-state dependent astrocytic Ca2+ signals are coupled to both positive and negative BOLD-fMRI signals.

PubMed

Wang, Maosen; He, Yi; Sejnowski, Terrence J; Yu, Xin

2018-02-13

Astrocytic Ca 2+ -mediated gliovascular interactions regulate the neurovascular network in situ and in vivo. However, it is difficult to measure directly both the astrocytic activity and fMRI to relate the various forms of blood-oxygen-level-dependent (BOLD) signaling to brain states under normal and pathological conditions. In this study, fMRI and GCaMP-mediated Ca 2+ optical fiber recordings revealed distinct evoked astrocytic Ca 2+ signals that were coupled with positive BOLD signals and intrinsic astrocytic Ca 2+ signals that were coupled with negative BOLD signals. Both evoked and intrinsic astrocytic calcium signal could occur concurrently or respectively during stimulation. The intrinsic astrocytic calcium signal can be detected globally in multiple cortical sites in contrast to the evoked astrocytic calcium signal only detected at the activated cortical region. Unlike propagating Ca 2+ waves in spreading depolarization/depression, the intrinsic Ca 2+ spikes occurred simultaneously in both hemispheres and were initiated upon the activation of the central thalamus and midbrain reticular formation. The occurrence of the intrinsic astrocytic calcium signal is strongly coincident with an increased EEG power level of the brain resting-state fluctuation. These results demonstrate highly correlated astrocytic Ca 2+ spikes with bidirectional fMRI signals based on the thalamic regulation of cortical states, depicting a brain-state dependency of both astrocytic Ca 2+ and BOLD fMRI signals.

Differential responses in dorsal visual cortex to motion and disparity depth cues

PubMed Central

Arnoldussen, David M.; Goossens, Jeroen; van den Berg, Albert V.

2013-01-01

We investigated how interactions between monocular motion parallax and binocular cues to depth vary in human motion areas for wide-field visual motion stimuli (110 × 100°). We used fMRI with an extensive 2 × 3 × 2 factorial blocked design in which we combined two types of self-motion (translational motion and translational + rotational motion), with three categories of motion inflicted by the degree of noise (self-motion, distorted self-motion, and multiple object-motion), and two different view modes of the flow patterns (stereo and synoptic viewing). Interactions between disparity and motion category revealed distinct contributions to self- and object-motion processing in 3D. For cortical areas V6 and CSv, but not the anterior part of MT+ with bilateral visual responsiveness (MT+/b), we found a disparity-dependent effect of rotational flow and noise: When self-motion perception was degraded by adding rotational flow and moderate levels of noise, the BOLD responses were reduced compared with translational self-motion alone, but this reduction was cancelled by adding stereo information which also rescued the subject's self-motion percept. At high noise levels, when the self-motion percept gave way to a swarm of moving objects, the BOLD signal strongly increased compared to self-motion in areas MT+/b and V6, but only for stereo in the latter. BOLD response did not increase for either view mode in CSv. These different response patterns indicate different contributions of areas V6, MT+/b, and CSv to the processing of self-motion perception and the processing of multiple independent motions. PMID:24339808

Error processing in current and former cocaine users

PubMed Central

Castelluccio, Brian C.; Meda, Shashwath A.; Muska, Christine E.; Stevens, Michael C.; Pearlson, Godfrey D.

2013-01-01

Deficits in response inhibition and error processing can result in maladaptive behavior, including failure to use past mistakes to inform present decisions. A specific deficit in inhibiting a prepotent response represents one aspect of impulsivity and is a prominent feature of addictive behaviors in general, including cocaine abuse/dependence. Brain regions implicated in cognitive control exhibit reduced activation in cocaine abusers. The purposes of the present investigation were (1) to identify neural differences associated with error processing in current and former cocaine-dependent individuals compared to healthy controls and (2) to determine whether former, long-term abstinent cocaine users showed similar differences compared with current users. The present study used an fMRI Go/No-Go task to investigate differences in BOLD response to correct rejections and false alarms between current cocaine users (n=30), former cocaine users (n=29), and healthy controls (n=35). Impulsivity trait measures were also assessed and compared with BOLD activity. Nineteen regions of interest previously implicated in errors of disinhibition were queried. There were no group differences in the correct rejections condition, but both current and former users exhibited increased BOLD response relative to controls for false alarms. In current users, the pregenual cingulate gyrus and left angular/supramarginal gyri overactivated. In former users, the right middle frontal/precentral gyri, right inferior parietal lobule, and left angular/supramarginal gyri overactivated. Overall, our results support a hypothesis that neural activity in former users differs more from healthy controls than that of current users due to cognitive compensation that facilitates abstinence. PMID:23949893

Triarchic dimensions of psychopathy in young adulthood: Associations with clinical and physiological measures after accounting for adolescent psychopathic traits.

PubMed

Kyranides, Melina Nicole; Fanti, Kostas A; Sikki, Maria; Patrick, Christopher J

2017-04-01

This study examined associations of psychopathy facets of boldness, meanness, and disinhibition with clinically relevant variables and physiological reactivity to affective stimuli. These associations were examined after accounting for developmental associations with adolescent psychopathic traits, namely callous-unemotional traits, narcissism, and impulsivity. Psychopathic traits were assessed during adolescence using the Antisocial Process Screening Device and the Inventory of Callous Unemotional traits and during young adulthood via the Triarchic Psychopathy Measure. Clinical variables (N = 99, Mage = 15.91, 53% female), as well as affective and physiological responses (heart rate, skin conductance, startle modulation) to violent and erotic videos (N = 88, Mage = 19.92, 50% female) were also assessed during adulthood. After accounting for adolescent psychopathic traits, boldness was associated with high cognitive reappraisal and low anxiety, fear, and hostility, and meanness was related to callous-unemotional traits, hostility, less sympathy to victims, and less use of cognitive reappraisal. Disinhibition, by contrast, was associated with impulsivity, increased anxiety, and hostile and aggressive tendencies, as well as conduct disorder, antisocial personality disorder symptoms, and cognitive suppression. In addition, evidence was found for different physiological measures operating as biological indicators of these distinctive dimensions, with reduced resting heart rate and cardiac reactivity to violent stimuli indicative of boldness, above and beyond adolescent psychopathic traits, and low startle potentiation for violent stimuli indicative of callous-unemotional traits and meanness. These findings provide evidence for the value of a multidomain approach for clarifying neurobiological mechanisms of psychopathic tendencies that can inform prevention and treatment efforts. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Simultaneous EEG/fMRI analysis of the resonance phenomena in steady-state visual evoked responses.

PubMed

Bayram, Ali; Bayraktaroglu, Zubeyir; Karahan, Esin; Erdogan, Basri; Bilgic, Basar; Ozker, Muge; Kasikci, Itir; Duru, Adil D; Ademoglu, Ahmet; Oztürk, Cengizhan; Arikan, Kemal; Tarhan, Nevzat; Demiralp, Tamer

2011-04-01

The stability of the steady-state visual evoked potentials (SSVEPs) across trials and subjects makes them a suitable tool for the investigation of the visual system. The reproducible pattern of the frequency characteristics of SSVEPs shows a global amplitude maximum around 10 Hz and additional local maxima around 20 and 40 Hz, which have been argued to represent resonant behavior of damped neuronal oscillators. Simultaneous electroencephalogram/functional magnetic resonance imaging (EEG/fMRI) measurement allows testing of the resonance hypothesis about the frequency-selective increases in SSVEP amplitudes in human subjects, because the total synaptic activity that is represented in the fMRI-Blood Oxygen Level Dependent (fMRI-BOLD) response would not increase but get synchronized at the resonance frequency. For this purpose, 40 healthy volunteers were visually stimulated with flickering light at systematically varying frequencies between 6 and 46 Hz, and the correlations between SSVEP amplitudes and the BOLD responses were computed. The SSVEP frequency characteristics of all subjects showed 3 frequency ranges with an amplitude maximum in each of them, which roughly correspond to alpha, beta and gamma bands of the EEG. The correlation maps between BOLD responses and SSVEP amplitude changes across the different stimulation frequencies within each frequency band showed no significant correlation in the alpha range, while significant correlations were obtained in the primary visual area for the beta and gamma bands. This non-linear relationship between the surface recorded SSVEP amplitudes and the BOLD responses of the visual cortex at stimulation frequencies around the alpha band supports the view that a resonance at the tuning frequency of the thalamo-cortical alpha oscillator in the visual system is responsible for the global amplitude maximum of the SSVEP around 10 Hz. Information gained from the SSVEP/fMRI analyses in the present study might be extrapolated to the EEG/fMRI analysis of the transient event-related potentials (ERPs) in terms of expecting more reliable and consistent correlations between EEG and fMRI responses, when the analyses are carried out on evoked or induced oscillations (spectral perturbations) in separate frequency bands instead of the time-domain ERP peaks.

Effects of Career Duration, Concussion History, and Playing Position on White Matter Microstructure and Functional Neural Recruitment in Former College and Professional Football Athletes.

PubMed

Clark, Michael D; Varangis, Eleanna M L; Champagne, Allen A; Giovanello, Kelly S; Shi, Feng; Kerr, Zachary Y; Smith, J Keith; Guskiewicz, Kevin M

2018-03-01

Purpose To better understand the relationship between exposure to concussive and subconcussive head impacts, white matter integrity, and functional task-related neural activity in former U.S. football athletes. Materials and Methods Between 2011 and 2013, 61 cognitively unimpaired former collegiate and professional football players (age range, 52-65 years) provided informed consent to participate in this cross-sectional study. Participants were stratified across three crossed factors: career duration, concussion history, and primary playing position. Fractional anisotropy (FA) and blood oxygen level-dependent (BOLD) percent signal change (PSC) were measured with diffusion-weighted and task-related functional magnetic resonance imaging, respectively. Analyses of variance of FA and BOLD PSC were used to determine main or interaction effects of the three factors. Results A significant interaction between career duration and concussion history was observed; former college players with more than three concussions had lower FA in a broadly distributed area of white matter compared with those with zero to one concussion (t29 = 2.774; adjusted P = .037), and the opposite was observed for former professional players (t29 = 3.883; adjusted P = .001). A separate interaction between concussion history and position was observed: Nonspeed players with more than three concussions had lower FA in frontal white matter compared with those with zero to one concussion (t25 = 3.861; adjusted P = .002). Analysis of working memory-task BOLD PSC revealed a similar interaction between concussion history and position (all adjusted P < .004). Overall, former players with lower FA tended to have lower BOLD PSC across three levels of a working memory task. Conclusion Career duration and primary playing position seem to modify the effects of concussion history on white matter structure and neural recruitment. The differences in brain structure and function were observed in the absence of clinical impairment, which suggested that multimodal imaging may provide early markers of onset of traumatic neurodegenerative disease. © RSNA, 2017 Online supplemental material is available for this article.

Measuring functional connectivity using MEG: Methodology and comparison with fcMRI

PubMed Central

Brookes, Matthew J.; Hale, Joanne R.; Zumer, Johanna M.; Stevenson, Claire M.; Francis, Susan T.; Barnes, Gareth R.; Owen, Julia P.; Morris, Peter G.; Nagarajan, Srikantan S.

2011-01-01

Functional connectivity (FC) between brain regions is thought to be central to the way in which the brain processes information. Abnormal connectivity is thought to be implicated in a number of diseases. The ability to study FC is therefore a key goal for neuroimaging. Functional connectivity (fc) MRI has become a popular tool to make connectivity measurements but the technique is limited by its indirect nature. A multimodal approach is therefore an attractive means to investigate the electrodynamic mechanisms underlying hemodynamic connectivity. In this paper, we investigate resting state FC using fcMRI and magnetoencephalography (MEG). In fcMRI, we exploit the advantages afforded by ultra high magnetic field. In MEG we apply envelope correlation and coherence techniques to source space projected MEG signals. We show that beamforming provides an excellent means to measure FC in source space using MEG data. However, care must be taken when interpreting these measurements since cross talk between voxels in source space can potentially lead to spurious connectivity and this must be taken into account in all studies of this type. We show good spatial agreement between FC measured independently using MEG and fcMRI; FC between sensorimotor cortices was observed using both modalities, with the best spatial agreement when MEG data are filtered into the β band. This finding helps to reduce the potential confounds associated with each modality alone: while it helps reduce the uncertainties in spatial patterns generated by MEG (brought about by the ill posed inverse problem), addition of electrodynamic metric confirms the neural basis of fcMRI measurements. Finally, we show that multiple MEG based FC metrics allow the potential to move beyond what is possible using fcMRI, and investigate the nature of electrodynamic connectivity. Our results extend those from previous studies and add weight to the argument that neural oscillations are intimately related to functional connectivity and the BOLD response. PMID:21352925

The “unreasonable effectiveness” of stratigraphic and geomorphic experiments

NASA Astrophysics Data System (ADS)

Paola, Chris; Straub, Kyle; Mohrig, David; Reinhardt, Liam

2009-12-01

The growth of quantitative analysis and prediction in Earth-surface science has been accompanied by growth in experimental stratigraphy and geomorphology. Experimenters have grown increasingly bold in targeting landscape elements from channel reaches up to the entire erosional networks and depositional basins, often using very small facilities. The experiments produce spatial structure and kinematics that, although imperfect, compare well with natural systems despite differences of spatial scale, time scale, material properties, and number of active processes. Experiments have been particularly useful in studying a wide range of forms of self-organized (autogenic) complexity that occur in morphodynamic systems. Autogenic dynamics creates much of the spatial structure we see in the landscape and in preserved strata, and is strongly associated with sediment storage and release. The observed consistency between experimental and field systems despite large differences in governing dimensionless numbers is what we mean by "unreasonable effectiveness". We suggest that unreasonable experimental effectiveness arises from natural scale independence. We generalize existing ideas to relate internal similarity, in which a small part of a system is similar to the larger system, to external similarity, in which a small copy of a system is similar to the larger system. We propose that internal similarity implies external similarity, though not the converse. The external similarity of landscape experiments to natural landscapes suggests that natural scale independence may be even more characteristic of morphodynamics than it is of better studied cases such as turbulence. We urge a shift in emphasis in experimental stratigraphy and geomorphology away from classical dynamical scaling and towards a quantitative understanding of the origins and limits of scale independence. Other research areas with strong growth potential in experimental surface dynamics include physical-biotic interactions, cohesive effects, stochastic processes, the interplay of structural and geomorphic self-organization, extraction of quantitative process information from landscape and stratigraphic records, and closer interaction between experimentation and theory.

Planar spatial correlations, anisotropy, and specific surface area of stationary random porous media

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berryman, J.G.

1998-02-01

An earlier result of the author showed that an anisotropic spatial correlation function of a random porous medium could be used to compute the specific surface area when it is stationary as well as anisotropic by first performing a three-dimensional radial average and then taking the first derivative with respect to lag at the origin. This result generalized the earlier result for isotropic porous media of Debye {ital et al.} [J. Appl. Phys. {bold 28}, 679 (1957)]. The present article provides more detailed information about the use of spatial correlation functions for anisotropic porous media and in particular shows that,more » for stationary anisotropic media, the specific surface area can be related to the derivative of the two-dimensional radial average of the correlation function measured from cross sections taken through the anisotropic medium. The main concept is first illustrated using a simple pedagogical example for an anisotropic distribution of spherical voids. Then, a general derivation of formulas relating the derivative of the planar correlation functions to surface integrals is presented. When the surface normal is uniformly distributed (as is the case for any distribution of spherical voids), our formulas can be used to relate a specific surface area to easily measurable quantities from any single cross section. When the surface normal is not distributed uniformly (as would be the case for an oriented distribution of ellipsoidal voids), our results show how to obtain valid estimates of specific surface area by averaging measurements on three orthogonal cross sections. One important general observation for porous media is that the surface area from nearly flat cracks may be underestimated from measurements on orthogonal cross sections if any of the cross sections happen to lie in the plane of the cracks. This result is illustrated by taking the very small aspect ratio (penny-shaped crack) limit of an oblate spheroid, but holds for other types of flat surfaces as well.« less

A toolbox for the fast information analysis of multiple-site LFP, EEG and spike train recordings

PubMed Central

Magri, Cesare; Whittingstall, Kevin; Singh, Vanessa; Logothetis, Nikos K; Panzeri, Stefano

2009-01-01

Background Information theory is an increasingly popular framework for studying how the brain encodes sensory information. Despite its widespread use for the analysis of spike trains of single neurons and of small neural populations, its application to the analysis of other types of neurophysiological signals (EEGs, LFPs, BOLD) has remained relatively limited so far. This is due to the limited-sampling bias which affects calculation of information, to the complexity of the techniques to eliminate the bias, and to the lack of publicly available fast routines for the information analysis of multi-dimensional responses. Results Here we introduce a new C- and Matlab-based information theoretic toolbox, specifically developed for neuroscience data. This toolbox implements a novel computationally-optimized algorithm for estimating many of the main information theoretic quantities and bias correction techniques used in neuroscience applications. We illustrate and test the toolbox in several ways. First, we verify that these algorithms provide accurate and unbiased estimates of the information carried by analog brain signals (i.e. LFPs, EEGs, or BOLD) even when using limited amounts of experimental data. This test is important since existing algorithms were so far tested primarily on spike trains. Second, we apply the toolbox to the analysis of EEGs recorded from a subject watching natural movies, and we characterize the electrodes locations, frequencies and signal features carrying the most visual information. Third, we explain how the toolbox can be used to break down the information carried by different features of the neural signal into distinct components reflecting different ways in which correlations between parts of the neural signal contribute to coding. We illustrate this breakdown by analyzing LFPs recorded from primary visual cortex during presentation of naturalistic movies. Conclusion The new toolbox presented here implements fast and data-robust computations of the most relevant quantities used in information theoretic analysis of neural data. The toolbox can be easily used within Matlab, the environment used by most neuroscience laboratories for the acquisition, preprocessing and plotting of neural data. It can therefore significantly enlarge the domain of application of information theory to neuroscience, and lead to new discoveries about the neural code. PMID:19607698