Stimulus change detection in phasic auditory units in the frog midbrain: frequency and ear specific adaptation

PubMed Central

Ponnath, Abhilash; Hoke, Kim L.

2013-01-01

Neural adaptation, a reduction in the response to a maintained stimulus, is an important mechanism for detecting stimulus change. Contributing to change detection is the fact that adaptation is often stimulus specific: adaptation to a particular stimulus reduces excitability to a specific subset of stimuli, while the ability to respond to other stimuli is unaffected. Phasic cells (e.g., cells responding to stimulus onset) are good candidates for detecting the most rapid changes in natural auditory scenes, as they exhibit fast and complete adaptation to an initial stimulus presentation. We made recordings of single phasic auditory units in the frog midbrain to determine if adaptation was specific to stimulus frequency and ear of input. In response to an instantaneous frequency step in a tone, 28 % of phasic cells exhibited frequency specific adaptation based on a relative frequency change (delta-f = ±16 %). Frequency specific adaptation was not limited to frequency steps, however, as adaptation was also overcome during continuous frequency modulated stimuli and in response to spectral transients interrupting tones. The results suggest that adaptation is separated for peripheral (e.g., frequency) channels. This was tested directly using dichotic stimuli. In 45 % of binaural phasic units, adaptation was ear specific: adaptation to stimulation of one ear did not affect responses to stimulation of the other ear. Thus, adaptation exhibited specificity for stimulus frequency and lateralization at the level of the midbrain. This mechanism could be employed to detect rapid stimulus change within and between sound sources in complex acoustic environments. PMID:23344947

Choice of Stimulus Range and Size Can Reduce Test-Retest Variability in Glaucomatous Visual Field Defects

PubMed Central

Swanson, William H.; Horner, Douglas G.; Dul, Mitchell W.; Malinovsky, Victor E.

2014-01-01

Purpose To develop guidelines for engineering perimetric stimuli to reduce test-retest variability in glaucomatous defects. Methods Perimetric testing was performed on one eye for 62 patients with glaucoma and 41 age-similar controls on size III and frequency-doubling perimetry and three custom tests with Gaussian blob and Gabor sinusoid stimuli. Stimulus range was controlled by values for ceiling (maximum sensitivity) and floor (minimum sensitivity). Bland-Altman analysis was used to derive 95% limits of agreement on test and retest, and bootstrap analysis was used to test the hypotheses about peak variability. Results Limits of agreement for the three custom stimuli were similar in width (0.72 to 0.79 log units) and peak variability (0.22 to 0.29 log units) for a stimulus range of 1.7 log units. The width of the limits of agreement for size III decreased from 1.78 to 1.37 to 0.99 log units for stimulus ranges of 3.9, 2.7, and 1.7 log units, respectively (F = 3.23, P < 0.001); peak variability was 0.99, 0.54, and 0.34 log units, respectively (P < 0.01). For a stimulus range of 1.3 log units, limits of agreement were narrowest with Gabor and widest with size III stimuli, and peak variability was lower (P < 0.01) with Gabor (0.18 log units) and frequency-doubling perimetry (0.24 log units) than with size III stimuli (0.38 log units). Conclusions Test-retest variability in glaucomatous visual field defects was substantially reduced by engineering the stimuli. Translational Relevance The guidelines should allow developers to choose from a wide range of stimuli. PMID:25371855

Choice of Stimulus Range and Size Can Reduce Test-Retest Variability in Glaucomatous Visual Field Defects.

PubMed

Swanson, William H; Horner, Douglas G; Dul, Mitchell W; Malinovsky, Victor E

2014-09-01

To develop guidelines for engineering perimetric stimuli to reduce test-retest variability in glaucomatous defects. Perimetric testing was performed on one eye for 62 patients with glaucoma and 41 age-similar controls on size III and frequency-doubling perimetry and three custom tests with Gaussian blob and Gabor sinusoid stimuli. Stimulus range was controlled by values for ceiling (maximum sensitivity) and floor (minimum sensitivity). Bland-Altman analysis was used to derive 95% limits of agreement on test and retest, and bootstrap analysis was used to test the hypotheses about peak variability. Limits of agreement for the three custom stimuli were similar in width (0.72 to 0.79 log units) and peak variability (0.22 to 0.29 log units) for a stimulus range of 1.7 log units. The width of the limits of agreement for size III decreased from 1.78 to 1.37 to 0.99 log units for stimulus ranges of 3.9, 2.7, and 1.7 log units, respectively ( F = 3.23, P < 0.001); peak variability was 0.99, 0.54, and 0.34 log units, respectively ( P < 0.01). For a stimulus range of 1.3 log units, limits of agreement were narrowest with Gabor and widest with size III stimuli, and peak variability was lower ( P < 0.01) with Gabor (0.18 log units) and frequency-doubling perimetry (0.24 log units) than with size III stimuli (0.38 log units). Test-retest variability in glaucomatous visual field defects was substantially reduced by engineering the stimuli. The guidelines should allow developers to choose from a wide range of stimuli.

75 FR 5041 - Extension of the Patent Application Backlog Reduction Stimulus Plan

Federal Register 2010, 2011, 2012, 2013, 2014

2010-02-01

... DEPARTMENT OF COMMERCE Patent and Trademark Office [Docket No.: PTO-P-2010-0003] Extension of the Patent Application Backlog Reduction Stimulus Plan AGENCY: United States Patent and Trademark Office, Commerce. ACTION: Notice. SUMMARY: The United States Patent and Trademark Office (USPTO) published a notice...

Differences in reward processing between putative cell types in primate prefrontal cortex

PubMed Central

Fan, Hongwei; Wang, Rubin; Sakagami, Masamichi

2017-01-01

Single-unit studies in monkeys have demonstrated that neurons in the prefrontal cortex predict the reward type, reward amount or reward availability associated with a stimulus. To examine contributions of pyramidal cells and interneurons in reward processing, single-unit activity was extracellularly recorded in prefrontal cortices of four monkeys performing a reward prediction task. Based on their shapes of spike waveforms, prefrontal neurons were classified into broad-spike and narrow-spike units that represented putative pyramidal cells and interneurons, respectively. We mainly observed that narrow-spike neurons showed higher firing rates but less bursty discharges than did broad-spike neurons. Both narrow-spike and broad-spike cells selectively responded to the stimulus, reward and their interaction, and the proportions of each type of selective neurons were similar between the two cell classes. Moreover, the two types of cells displayed equal reliability of reward or stimulus discrimination. Furthermore, we found that broad-spike and narrow-spike cells showed distinct mechanisms for encoding reward or stimulus information. Broad-spike neurons raised their firing rate relative to the baseline rate to represent the preferred reward or stimulus information, whereas narrow-spike neurons inhibited their firing rate lower than the baseline rate to encode the non-preferred reward or stimulus information. Our results suggest that narrow-spike and broad-spike cells were equally involved in reward and stimulus processing in the prefrontal cortex. They utilized a binary strategy to complementarily represent reward or stimulus information, which was consistent with the task structure in which the monkeys were required to remember two reward conditions and two visual stimuli. PMID:29261734

Differences in reward processing between putative cell types in primate prefrontal cortex.

PubMed

Fan, Hongwei; Pan, Xiaochuan; Wang, Rubin; Sakagami, Masamichi

2017-01-01

Single-unit studies in monkeys have demonstrated that neurons in the prefrontal cortex predict the reward type, reward amount or reward availability associated with a stimulus. To examine contributions of pyramidal cells and interneurons in reward processing, single-unit activity was extracellularly recorded in prefrontal cortices of four monkeys performing a reward prediction task. Based on their shapes of spike waveforms, prefrontal neurons were classified into broad-spike and narrow-spike units that represented putative pyramidal cells and interneurons, respectively. We mainly observed that narrow-spike neurons showed higher firing rates but less bursty discharges than did broad-spike neurons. Both narrow-spike and broad-spike cells selectively responded to the stimulus, reward and their interaction, and the proportions of each type of selective neurons were similar between the two cell classes. Moreover, the two types of cells displayed equal reliability of reward or stimulus discrimination. Furthermore, we found that broad-spike and narrow-spike cells showed distinct mechanisms for encoding reward or stimulus information. Broad-spike neurons raised their firing rate relative to the baseline rate to represent the preferred reward or stimulus information, whereas narrow-spike neurons inhibited their firing rate lower than the baseline rate to encode the non-preferred reward or stimulus information. Our results suggest that narrow-spike and broad-spike cells were equally involved in reward and stimulus processing in the prefrontal cortex. They utilized a binary strategy to complementarily represent reward or stimulus information, which was consistent with the task structure in which the monkeys were required to remember two reward conditions and two visual stimuli.

Activation of superficial dorsal horn neurons in the mouse by a PAR-2 agonist and 5-HT: potential role in itch.

PubMed

Akiyama, Tasuku; Merrill, Austin W; Carstens, Mirela Iodi; Carstens, E

2009-05-20

Itch, an unpleasant sensation associated with the desire to scratch, is symptomatic of dermatologic and systemic disorders that often resist antihistamine treatment. Histamine-independent itch mediators include serotonin (5-HT) and agonists of the protease-activated receptor-2 (PAR-2). We used behavior, Fos immunohistochemistry, and electrophysiology to investigate if these mediators activate spinal dorsal horn neurons in a manner consistent with itch. Intradermal (i.d.) injection of the PAR-2 agonist SLIGRL-NH(2) in the rostral back evoked bouts of directed hindlimb scratches over 20-30 min. Hindpaw injection of SLIGRL-NH(2) produced Fos staining in superficial dorsal horn which was then targeted for single-unit recording. Small id microinjections of SLIGRL-NH(2) or 5-HT identified responsive single units in the superficial dorsal horn of mice anesthetized with pentobarbital. Thirty-eight units characterized as wide dynamic range, nociceptive specific, or mechanically insensitive exhibited significantly increased firing after i.d. SLIGRL-NH(2) for 9 min, to partial (25%) tachyphylaxis with repeated injection. A majority additionally responded to 5-HT (70%), mustard oil (79%), and capsaicin (71%). Seven units isolated with the 5-HT search stimulus exhibited significant and prolonged responses to 5-HT with tachyphylaxis to repeated injections. The majority also responded to SLIGRL-NH(2), mustard oil, and capsaicin. The prolonged responses of superficial dorsal horn neurons to SLIGRL-NH(2) and 5-HT suggest a role in signaling itch. However, their responsiveness to algogens is inconsistent with itch specificity. Alternatively, such neurons may signal itch, whereas noxious stimulus levels recruit these and a larger population of pruritogen-insensitive cells to signal pain which masks or occludes the itch signal.

Extinction of Chained Instrumental Behaviors: Effects of Procurement Extinction on Consumption Responding

PubMed Central

Thrailkill, Eric A.; Bouton, Mark E.

2015-01-01

Instrumental behavior often consists of sequences or chains of responses that minimally include procurement behaviors that enable subsequent consumption behaviors. In such chains, behavioral units are linked by access to one another and eventually to a primary reinforcer, such as food or a drug. The present experiments examined the effects of extinguishing procurement responding on consumption responding after training of a discriminated heterogeneous instrumental chain. Rats learned to make a procurement response (e.g., pressing a lever) in the presence of a distinctive discriminative stimulus; making that response led to the presentation of a second discriminative stimulus that set the occasion for a consumption response (e.g., pulling a chain), which then produced a food-pellet reinforcer. Experiment 1 showed that extinction of either the full procurement-consumption chain or procurement alone weakened the consumption response tested in isolation. Experiment 2 replicated the procurement extinction effect and further demonstrated that the opportunity to make the procurement response, as opposed to simple exposure to the procurement stimulus alone, was required. In Experiment 3, rats learned 2 distinct discriminated heterogeneous chains; extinction of 1 procurement response specifically weakened the consumption response that had been associated with it. The results suggest that learning to inhibit the procurement response may produce extinction of consumption responding through mediated extinction. The experiments suggest the importance of an associative analysis of instrumental behavior chains. PMID:25915751

RULES OF COMPETITIVE STIMULUS SELECTION IN A CHOLINERGIC ISTHMIC NUCLEUS OF THE OWL MIDBRAIN

PubMed Central

Asadollahi, Ali; Mysore, Shreesh P.; Knudsen, Eric I.

2011-01-01

In a natural scene, multiple stimuli compete for the control of gaze direction and attention. The nucleus isthmi pars parvocellularis (Ipc) is a cholinergic, midbrain nucleus that is reciprocally interconnected to the optic tectum, a structure known to be involved in the control of gaze and attention. Previous research has shown that the responses of many Ipc units to a visual stimulus presented inside the classical receptive field (RF) can be powerfully inhibited when the strength of a distant, competing stimulus becomes the stronger stimulus. This study investigated further the nature of competitive interactions in the Ipc of owls by employing two complementary protocols: in the first protocol, we measured the effects of a distant stimulus on responses to an RF stimulus located at different positions inside the RF; in the second protocol, we measured the effects of a distant stimulus on responses to RF stimuli of different strengths. The first protocol demonstrated that the effect of a competing stimulus is purely divisive: the competitor caused a proportional reduction in responses to the RF stimulus that did not alter either the location or sharpness of spatial tuning. The second protocol demonstrated that, for most units, the strength of this divisive inhibition is regulated powerfully by the relative strengths of the competing stimuli: inhibition was strong when the competitor was the stronger stimulus and weak when the competitor was the weaker stimulus. The data indicate that competitive interactions in the Ipc depend on feedback and a globally divisive inhibitory network. PMID:21508234

Input, Triggering and Poverty of the Stimulus in the Second Language Acquisition of Japanese Passives

ERIC Educational Resources Information Center

Hara, Masahiro

2007-01-01

This article adopts an input perspective in examining a poverty-of-the stimulus (POS) learning situation in second language acquisition (SLA). Analysis of grammaticality judgement data from 81 English-speaking and 85 Chinese-speaking learners of Japanese isolates triggering input that informed English learners of subtle semantic properties of the…

Anesthetic effects on fictive locomotion in the rat isolated spinal cord

PubMed Central

Jinks, Steven L.; Andrada, Jason; Satter, Omar

2011-01-01

General anesthetic mechanisms are poorly understood. Anesthetic immobilizing effects occur in the spinal ventral horn. However, a detailed analysis of anesthetic effects on ventral motor networks is lacking. We delivered isoflurane, desflurane, or propofol during NMDA/5-HT-induced, or noxious tail stimulus-evoked, fictive locomotion in neonatal rat isolated spinal cords. Anesthetics changed the frequency, amplitude, and regularity of fictive locomotion with little effect on phase-lag. Isoflurane abolished pharmacologically-induced vs noxious stimulus-induced motor output at similar concentrations. Propofol abolished pharmacologically-induced fictive locomotion via a GABAA-receptor mechanism. Anesthetic effects on pharmacologically-elicted fictive locomotion appear clinically-relevant, and support a ventral horn immobilizing effect on locomotor rhythm generation. PMID:21817927

Data management system DIU test system

NASA Technical Reports Server (NTRS)

1976-01-01

An operational and functional description is given of the data management system. Descriptions are included for the test control unit, analog stimulus panel, discrete stimulus panel, and the precision source. The mechanical configuration is defined and illustrated to provide card and component location for modification or repair. The unit level interfaces are mirror images of the DIU interfaces and are described in the Final Technical Report for NASA-MSFC contract NAS8-29155.

Decoding the auditory brain with canonical component analysis.

PubMed

de Cheveigné, Alain; Wong, Daniel D E; Di Liberto, Giovanni M; Hjortkjær, Jens; Slaney, Malcolm; Lalor, Edmund

2018-05-15

The relation between a stimulus and the evoked brain response can shed light on perceptual processes within the brain. Signals derived from this relation can also be harnessed to control external devices for Brain Computer Interface (BCI) applications. While the classic event-related potential (ERP) is appropriate for isolated stimuli, more sophisticated "decoding" strategies are needed to address continuous stimuli such as speech, music or environmental sounds. Here we describe an approach based on Canonical Correlation Analysis (CCA) that finds the optimal transform to apply to both the stimulus and the response to reveal correlations between the two. Compared to prior methods based on forward or backward models for stimulus-response mapping, CCA finds significantly higher correlation scores, thus providing increased sensitivity to relatively small effects, and supports classifier schemes that yield higher classification scores. CCA strips the brain response of variance unrelated to the stimulus, and the stimulus representation of variance that does not affect the response, and thus improves observations of the relation between stimulus and response. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

Highly Reconfigurable Beamformer Stimulus Generator

NASA Astrophysics Data System (ADS)

Vaviļina, E.; Gaigals, G.

2018-02-01

The present paper proposes a highly reconfigurable beamformer stimulus generator of radar antenna array, which includes three main blocks: settings of antenna array, settings of objects (signal sources) and a beamforming simulator. Following from the configuration of antenna array and object settings, different stimulus can be generated as the input signal for a beamformer. This stimulus generator is developed under a greater concept with two utterly independent paths where one is the stimulus generator and the other is the hardware beamformer. Both paths can be complemented in final and in intermediate steps as well to check and improve system performance. This way the technology development process is promoted by making each of the future hardware steps more substantive. Stimulus generator configuration capabilities and test results are presented proving the application of the stimulus generator for FPGA based beamforming unit development and tuning as an alternative to an actual antenna system.

Task set persistence modulates word reading following resolution of picture-word interference.

PubMed

Masson, Michael E J; Bub, Daniel N; Ishigami, Yoko

2007-12-01

We extend the finding that word reading slows following successful responses to a color-word Stroop interference task (Masson, Bub, Woodward, & Chan, 2003). Word reading was assessed in a picture-word interference task in which subjects alternated between naming a picture (with either a word or a row of Xs superimposed on it) and reading a word. For the word-reading task, words were presented either in isolation or superimposed on a picture. Word reading was slower after subjects responded to a bivalent stimulus that required resolution of conflict (naming a picture with a word superimposed on it) than after they responded to a stimulus that involved no conflict (naming a picture with Xs superimposed on it), indicating modulation of dominant task performance. This effect was found when word-reading targets were superimposed on pictures but not when those targets were presented in isolation. Modulation of word reading, therefore, appears to be the result of interference from a persistent picture-naming task set, cued by a stimulus configuration that invites execution of both competing tasks.

Hemispheric asymmetry in holistic processing of words.

PubMed

Ventura, Paulo; Delgado, João; Ferreira, Miguel; Farinha-Fernandes, António; Guerreiro, José C; Faustino, Bruno; Leite, Isabel; Wong, Alan C-N

2018-05-13

Holistic processing has been regarded as a hallmark of face perception, indicating the automatic and obligatory tendency of the visual system to process all face parts as a perceptual unit rather than in isolation. Studies involving lateralized stimulus presentation suggest that the right hemisphere dominates holistic face processing. Holistic processing can also be shown with other categories such as words and thus it is not specific to faces or face-like expertize. Here, we used divided visual field presentation to investigate the possibly different contributions of the two hemispheres for holistic word processing. Observers performed same/different judgment on the cued parts of two sequentially presented words in the complete composite paradigm. Our data indicate a right hemisphere specialization for holistic word processing. Thus, these markers of expert object recognition are domain general.

Routine post-weaning handling of rats prevents isolation rearing-induced deficit in prepulse inhibition.

PubMed

Rosa, M L N M; Silva, R C B; Moura-de-Carvalho, F T; Brandão, M L; Guimarães, F S; Del Bel, E A

2005-11-01

Rats reared under isolation conditions from weaning present a number of behavioral changes compared to animals reared under social conditions (group housing). These changes include deficits in prepulse inhibition (PPI) of the startle reflex to a loud sound. PPI refers to the reduction of the magnitude of the startle reflex when a relatively weak stimulus (the prepulse) precedes by an appropriate time interval the intense startle-elicing stimulus (the pulse). PPI is useful for studying sensorimotor integration. The present study evaluated the effect of handling on the impairment of PPI induced by isolation-rearing. Male Wistar rats (N = 11-15/group) were housed in groups (5 per cage and handled three times a week) or isolated (housed individually) since weaning (21 days) for 10 weeks when they reach approximately 150 g. The isolated rats were divided into "minimally handled" animals (handled once a week for cleaning purposes only) or "handled" animals (handled three times a week). This handling consisted of grasping the rat by the tail and moving it to a clean cage (approximately 5 s). A statistically significant reduction (52%) in the PPI test was found only in the isolated group with minimal handling while no difference was seen between grouped animals and isolated handled animals. These results indicate that isolation rearing causes disruption in the PPI at adult age, which serves as an index of attention deficit. This change in the sensory processing of information induced by post-weaning isolation can be prevented by handling during the development of the animal.

Modeling conflict and error in the medial frontal cortex.

PubMed

Mayer, Andrew R; Teshiba, Terri M; Franco, Alexandre R; Ling, Josef; Shane, Matthew S; Stephen, Julia M; Jung, Rex E

2012-12-01

Despite intensive study, the role of the dorsal medial frontal cortex (dMFC) in error monitoring and conflict processing remains actively debated. The current experiment manipulated conflict type (stimulus conflict only or stimulus and response selection conflict) and utilized a novel modeling approach to isolate error and conflict variance during a multimodal numeric Stroop task. Specifically, hemodynamic response functions resulting from two statistical models that either included or isolated variance arising from relatively few error trials were directly contrasted. Twenty-four participants completed the task while undergoing event-related functional magnetic resonance imaging on a 1.5-Tesla scanner. Response times monotonically increased based on the presence of pure stimulus or stimulus and response selection conflict. Functional results indicated that dMFC activity was present during trials requiring response selection and inhibition of competing motor responses, but absent during trials involving pure stimulus conflict. A comparison of the different statistical models suggested that relatively few error trials contributed to a disproportionate amount of variance (i.e., activity) throughout the dMFC, but particularly within the rostral anterior cingulate gyrus (rACC). Finally, functional connectivity analyses indicated that an empirically derived seed in the dorsal ACC/pre-SMA exhibited strong connectivity (i.e., positive correlation) with prefrontal and inferior parietal cortex but was anti-correlated with the default-mode network. An empirically derived seed from the rACC exhibited the opposite pattern, suggesting that sub-regions of the dMFC exhibit different connectivity patterns with other large scale networks implicated in internal mentations such as daydreaming (default-mode) versus the execution of top-down attentional control (fronto-parietal). Copyright © 2011 Wiley Periodicals, Inc.

Expectation and Surprise Determine Neural Population Responses in the Ventral Visual Stream

PubMed Central

Egner, Tobias; Monti, Jim M.; Summerfield, Christopher

2014-01-01

Visual cortex is traditionally viewed as a hierarchy of neural feature detectors, with neural population responses being driven by bottom-up stimulus features. Conversely, “predictive coding” models propose that each stage of the visual hierarchy harbors two computationally distinct classes of processing unit: representational units that encode the conditional probability of a stimulus and provide predictions to the next lower level; and error units that encode the mismatch between predictions and bottom-up evidence, and forward prediction error to the next higher level. Predictive coding therefore suggests that neural population responses in category-selective visual regions, like the fusiform face area (FFA), reflect a summation of activity related to prediction (“face expectation”) and prediction error (“face surprise”), rather than a homogenous feature detection response. We tested the rival hypotheses of the feature detection and predictive coding models by collecting functional magnetic resonance imaging data from the FFA while independently varying both stimulus features (faces vs houses) and subjects’ perceptual expectations regarding those features (low vs medium vs high face expectation). The effects of stimulus and expectation factors interacted, whereby FFA activity elicited by face and house stimuli was indistinguishable under high face expectation and maximally differentiated under low face expectation. Using computational modeling, we show that these data can be explained by predictive coding but not by feature detection models, even when the latter are augmented with attentional mechanisms. Thus, population responses in the ventral visual stream appear to be determined by feature expectation and surprise rather than by stimulus features per se. PMID:21147999

Blood Oxygen Level-Dependent Activation of the Primary Visual Cortex Predicts Size Adaptation Illusion

PubMed Central

Pooresmaeili, Arezoo; Arrighi, Roberto; Biagi, Laura; Morrone, Maria Concetta

2016-01-01

In natural scenes, objects rarely occur in isolation but appear within a spatiotemporal context. Here, we show that the perceived size of a stimulus is significantly affected by the context of the scene: brief previous presentation of larger or smaller adapting stimuli at the same region of space changes the perceived size of a test stimulus, with larger adapting stimuli causing the test to appear smaller than veridical and vice versa. In a human fMRI study, we measured the blood oxygen level-dependent activation (BOLD) responses of the primary visual cortex (V1) to the contours of large-diameter stimuli and found that activation closely matched the perceptual rather than the retinal stimulus size: the activated area of V1 increased or decreased, depending on the size of the preceding stimulus. A model based on local inhibitory V1 mechanisms simulated the inward or outward shifts of the stimulus contours and hence the perceptual effects. Our findings suggest that area V1 is actively involved in reshaping our perception to match the short-term statistics of the visual scene. PMID:24089504

Stimulus encoding and feature extraction by multiple sensory neurons.

PubMed

Krahe, Rüdiger; Kreiman, Gabriel; Gabbiani, Fabrizio; Koch, Christof; Metzner, Walter

2002-03-15

Neighboring cells in topographical sensory maps may transmit similar information to the next higher level of processing. How information transmission by groups of nearby neurons compares with the performance of single cells is a very important question for understanding the functioning of the nervous system. To tackle this problem, we quantified stimulus-encoding and feature extraction performance by pairs of simultaneously recorded electrosensory pyramidal cells in the hindbrain of weakly electric fish. These cells constitute the output neurons of the first central nervous stage of electrosensory processing. Using random amplitude modulations (RAMs) of a mimic of the fish's own electric field within behaviorally relevant frequency bands, we found that pyramidal cells with overlapping receptive fields exhibit strong stimulus-induced correlations. To quantify the encoding of the RAM time course, we estimated the stimuli from simultaneously recorded spike trains and found significant improvements over single spike trains. The quality of stimulus reconstruction, however, was still inferior to the one measured for single primary sensory afferents. In an analysis of feature extraction, we found that spikes of pyramidal cell pairs coinciding within a time window of a few milliseconds performed significantly better at detecting upstrokes and downstrokes of the stimulus compared with isolated spikes and even spike bursts of single cells. Coincident spikes can thus be considered "distributed bursts." Our results suggest that stimulus encoding by primary sensory afferents is transformed into feature extraction at the next processing stage. There, stimulus-induced coincident activity can improve the extraction of behaviorally relevant features from the stimulus.

Missouri Journal of Research in Music Education, 1989-1994.

ERIC Educational Resources Information Center

Koch, Franklin W., Ed.; Sims, Wendy L., Ed.; Pembrook, Randall G., Ed.

1994-01-01

This journal is devoted to the needs and interests of the school and college music teachers of Missouri and the United States. Articles in Number 26 are: "The Effect of Instrument Type, Stimulus Timbre, and Stimulus Octave Placement on Tuning Accuracy" (Jane W. Cassidy); "The Relationship of Music Opportunity at the Common School…

The effect of object processing in content-dependent source memory

PubMed Central

2013-01-01

Background Previous studies have suggested that the study condition of an item influences how the item is encoded. However, it is still unclear whether subsequent source memory effects are dependent upon stimulus content when the item and context are unitized. The present fMRI study investigated the effect of encoding activity sensitive to stimulus content in source memory via unitization. In the scanner, participants were instructed to integrate a study item, an object in either a word or a picture form, with perceptual context into a single image. Results Subsequent source memory effects independent of stimulus content were identified in the left lateral frontal and parietal regions, bilateral fusiform areas, and the left perirhinal cortex extending to the anterior hippocampus. Content-dependent subsequent source memory effects were found only with words in the left medial frontal lobe, the ventral visual stream, and bilateral parahippocampal regions. Further, neural activity for source memory with words extensively overlapped with the region where pictures were preferentially processed than words, including the left mid-occipital cortex and the right parahippocampal cortex. Conclusions These results indicate that words that were accurately remembered with correct contextual information were processed more like pictures mediated by integrated imagery operation, compared to words that were recognized with incorrect context. In contrast, such processing did not discriminate subsequent source memory with pictures. Taken together, these findings suggest that unitization supports source memory for both words and pictures and that the requirement of the study task interacts with the nature of stimulus content in unitized source encoding. PMID:23848969

Neural Representations that Support Invariant Object Recognition

PubMed Central

Goris, Robbe L. T.; Op de Beeck, Hans P.

2008-01-01

Neural mechanisms underlying invariant behaviour such as object recognition are not well understood. For brain regions critical for object recognition, such as inferior temporal cortex (ITC), there is now ample evidence indicating that single cells code for many stimulus aspects, implying that only a moderate degree of invariance is present. However, recent theoretical and empirical work seems to suggest that integrating responses of multiple non-invariant units may produce invariant representations at population level. We provide an explicit test for the hypothesis that a linear read-out mechanism of a pool of units resembling ITC neurons may achieve invariant performance in an identification task. A linear classifier was trained to decode a particular value in a 2-D stimulus space using as input the response pattern across a population of units. Only one dimension was relevant for the task, and the stimulus location on the irrelevant dimension (ID) was kept constant during training. In a series of identification tests, the stimulus location on the relevant dimension (RD) and ID was manipulated, yielding estimates for both the level of sensitivity and tolerance reached by the network. We studied the effects of several single-cell characteristics as well as population characteristics typically considered in the literature, but found little support for the hypothesis. While the classifier averages out effects of idiosyncratic tuning properties and inter-unit variability, its invariance is very much determined by the (hypothetical) ‘average’ neuron. Consequently, even at population level there exists a fundamental trade-off between selectivity and tolerance, and invariant behaviour does not emerge spontaneously. PMID:19242556

Neural Population Coding of Multiple Stimuli

PubMed Central

Ma, Wei Ji

2015-01-01

In natural scenes, objects generally appear together with other objects. Yet, theoretical studies of neural population coding typically focus on the encoding of single objects in isolation. Experimental studies suggest that neural responses to multiple objects are well described by linear or nonlinear combinations of the responses to constituent objects, a phenomenon we call stimulus mixing. Here, we present a theoretical analysis of the consequences of common forms of stimulus mixing observed in cortical responses. We show that some of these mixing rules can severely compromise the brain's ability to decode the individual objects. This cost is usually greater than the cost incurred by even large reductions in the gain or large increases in neural variability, explaining why the benefits of attention can be understood primarily in terms of a stimulus selection, or demixing, mechanism rather than purely as a gain increase or noise reduction mechanism. The cost of stimulus mixing becomes even higher when the number of encoded objects increases, suggesting a novel mechanism that might contribute to set size effects observed in myriad psychophysical tasks. We further show that a specific form of neural correlation and heterogeneity in stimulus mixing among the neurons can partially alleviate the harmful effects of stimulus mixing. Finally, we derive simple conditions that must be satisfied for unharmful mixing of stimuli. PMID:25740513

Identification of Autophagosome-associated Proteins and Regulators by Quantitative Proteomic Analysis and Genetic Screens*

PubMed Central

Dengjel, Jörn; Høyer-Hansen, Maria; Nielsen, Maria O.; Eisenberg, Tobias; Harder, Lea M.; Schandorff, Søren; Farkas, Thomas; Kirkegaard, Thomas; Becker, Andrea C.; Schroeder, Sabrina; Vanselow, Katja; Lundberg, Emma; Nielsen, Mogens M.; Kristensen, Anders R.; Akimov, Vyacheslav; Bunkenborg, Jakob; Madeo, Frank; Jäättelä, Marja; Andersen, Jens S.

2012-01-01

Autophagy is one of the major intracellular catabolic pathways, but little is known about the composition of autophagosomes. To study the associated proteins, we isolated autophagosomes from human breast cancer cells using two different biochemical methods and three stimulus types: amino acid deprivation or rapamycin or concanamycin A treatment. The autophagosome-associated proteins were dependent on stimulus, but a core set of proteins was stimulus-independent. Remarkably, proteasomal proteins were abundant among the stimulus-independent common autophagosome-associated proteins, and the activation of autophagy significantly decreased the cellular proteasome level and activity supporting interplay between the two degradation pathways. A screen of yeast strains defective in the orthologs of the human genes encoding for a common set of autophagosome-associated proteins revealed several regulators of autophagy, including subunits of the retromer complex. The combined spatiotemporal proteomic and genetic data sets presented here provide a basis for further characterization of autophagosome biogenesis and cargo selection. PMID:22311637

Diversity of coding profiles of mechanoreceptors in glabrous skin of kittens.

PubMed

Gibson, J M; Beitel, R E; Welker, W

1975-03-21

We examined stimulul-response (S-R) profiles of 35 single mechanoreceptive afferent units having small receptive fields in glabrous forepaw skin of 24 anesthetized domestic kittens. Single unit activity was recorded with tungsten microelectrodes from cervical dorsal root ganglia. The study was designed to be as quantitatively descriptive as possible. We indented each unit's receptive field with a broad battery of simple, carefully controlled stimuli whose major parameters, including amplitude, velocity, acceleration, duration, and interstimulus interval were systematically varied. Stimuli were delivered by a small probe driven by a feedback-controlled axial displacement generator. Single unit discharge data were analyzed by a variety of direct and derived measures including dot patterns, peristimulus histograms, instantaneous and mean instantaneous firing rates, tuning curves, thresholds for amplitude and velocity, adaptation rates, dynamic and static sensitivities, and others. We found that with respect to any of the S-R transactions examined, the properties of our sample of units were continuously and broadly distributed. Any one unit might exhibit either a slow or rapid rate of adaptation, or might superficially appear to preferentially code a single stimulus parameter such as amplitude or velocity. But when the entire range of responsiveness of units to the entire stimulus battery was surveyed by a variety of analytic techniques, we were unable to find any justifiable basis for designation of discrete categories of S-R profiles. Intermediate response types were always found, and in general, all units were both broadly tuned and capable of responding to integrals of several stimulus parameters, our data argue against the usefulness of evaluating a unit's S-R coding capabilities by means of a limited ste of stimulation of response analysis procedures.

Statistical context shapes stimulus-specific adaptation in human auditory cortex

PubMed Central

Henry, Molly J.; Fromboluti, Elisa Kim; McAuley, J. Devin

2015-01-01

Stimulus-specific adaptation is the phenomenon whereby neural response magnitude decreases with repeated stimulation. Inconsistencies between recent nonhuman animal recordings and computational modeling suggest dynamic influences on stimulus-specific adaptation. The present human electroencephalography (EEG) study investigates the potential role of statistical context in dynamically modulating stimulus-specific adaptation by examining the auditory cortex-generated N1 and P2 components. As in previous studies of stimulus-specific adaptation, listeners were presented with oddball sequences in which the presentation of a repeated tone was infrequently interrupted by rare spectral changes taking on three different magnitudes. Critically, the statistical context varied with respect to the probability of small versus large spectral changes within oddball sequences (half of the time a small change was most probable; in the other half a large change was most probable). We observed larger N1 and P2 amplitudes (i.e., release from adaptation) for all spectral changes in the small-change compared with the large-change statistical context. The increase in response magnitude also held for responses to tones presented with high probability, indicating that statistical adaptation can overrule stimulus probability per se in its influence on neural responses. Computational modeling showed that the degree of coadaptation in auditory cortex changed depending on the statistical context, which in turn affected stimulus-specific adaptation. Thus the present data demonstrate that stimulus-specific adaptation in human auditory cortex critically depends on statistical context. Finally, the present results challenge the implicit assumption of stationarity of neural response magnitudes that governs the practice of isolating established deviant-detection responses such as the mismatch negativity. PMID:25652920

Stimulus features underlying reduced tremor suppression with temporally patterned deep brain stimulation

PubMed Central

Birdno, Merrill J.; Kuncel, Alexis M.; Dorval, Alan D.; Turner, Dennis A.; Gross, Robert E.

2012-01-01

Deep brain stimulation (DBS) provides dramatic tremor relief when delivered at high-stimulation frequencies (more than ∼100 Hz), but its mechanisms of action are not well-understood. Previous studies indicate that high-frequency stimulation is less effective when the stimulation train is temporally irregular. The purpose of this study was to determine the specific characteristics of temporally irregular stimulus trains that reduce their effectiveness: long pauses, bursts, or irregularity per se. We isolated these characteristics in stimulus trains and conducted intraoperative measurements of postural tremor in eight volunteers. Tremor varied significantly across stimulus conditions (P < 0.015), and stimulus trains with pauses were significantly less effective than stimulus trains without (P < 0.002). There were no significant differences in tremor between trains with or without bursts or between trains that were irregular or periodic. Thus the decreased effectiveness of temporally irregular DBS trains is due to long pauses in the stimulus trains, not the degree of temporal irregularity alone. We also conducted computer simulations of neuronal responses to the experimental stimulus trains using a biophysical model of the thalamic network. Trains that suppressed tremor in volunteers also suppressed fluctuations in thalamic transmembrane potential at the frequency associated with cerebellar burst-driver inputs. Clinical and computational findings indicate that DBS suppresses tremor by masking burst-driver inputs to the thalamus and that pauses in stimulation prevent such masking. Although stimulation of other anatomic targets may provide tremor suppression, we propose that the most relevant neuronal targets for effective tremor suppression are the afferent cerebellar fibers that terminate in the thalamus. PMID:21994263

Absence of a direct role of phospholipid methylation in stimulus-secretion coupling and control of adenylate cyclase in guinea-pig and rat parotid gland.

PubMed Central

Padel, U; Unger, C; Söling, H D

1982-01-01

The present study was undertaken to investigate a possible involvement of phospholipid methyltransferases in the coupling of receptor-mediated stimulation to secretion. Phospholipid methyltransferases were assayed in isolated parotid acini in the presence of carbamoylcholine or isoprenaline. Carbamoylcholine reduced the incorporation of methyl groups into phospholipids, whereas isoprenaline showed no effect. Amylase secretion stimulated either by carbamoylcholine or by isoprenaline could not be affected by inhibitors of methyltransferases (3-deaza-adenosine alone or plus homocysteine thiolactone) under conditions where phospholipid methylation was strongly inhibited. The activity of adenylate cyclase in isolated parotid microsomal membranes was not inhibited or stimulated by S-adenosyl-homocysteine or -methionine respectively. These results indicate that phospholipid methylation does not play an essential role in stimulus-secretion coupling in the parotid gland. PMID:6186246

Three conceptual units for behavior

PubMed Central

Moxley, Roy

1987-01-01

Three generic units for behavior are examined in terms of their background: an if-then unit for stimulus and response (S-R), a holistic unit for Kantor's behavior segment, and an AB-because-of-C unit for Skinner's three-term contingency. The units are distinguished in terms of their respective historical backgrounds, causal modes, advantages, and disadvantages. The ways in which these units may be compatible are discussed. PMID:22477957

Rod- versus cone-driven ERGs at different stimulus sizes in normal subjects and retinitis pigmentosa patients.

PubMed

Aher, Avinash J; McKeefry, Declan J; Parry, Neil R A; Maguire, John; Murray, I J; Tsai, Tina I; Huchzermeyer, Cord; Kremers, Jan

2018-02-01

To study how rod- and cone-driven responses depend on stimulus size in normal subjects and patients with retinitis pigmentosa (RP), and to show that comparisons between responses to full-field (FF) and smaller stimuli can be useful in diagnosing and monitoring disorders of the peripheral retina without the need for lengthy dark adaptation periods. The triple silent substitution technique was used to isolate L-cone-, M-cone- and rod-driven ERGs with 19, 18 and 33% photoreceptor contrasts, respectively, under identical mean luminance conditions. Experiments were conducted on five normal subjects and three RP patients. ERGs on control subjects were recorded at nine different temporal frequencies (between 2 and 60 Hz) for five different stimulus sizes: FF, 70°, 60°, 50° and 40° diameter circular stimuli. Experiments on RP patients involved rod- and L-cone-driven ERG measurements with FF and 40° stimuli at 8 and 48 Hz. Response amplitudes were defined as those of the first harmonic component after Fourier analysis. In normal subjects, rod-driven responses displayed a fundamentally different behavior than cone-driven responses, particularly at low temporal frequencies. At low and intermediate temporal frequencies (≤ 12 Hz), rod-driven signals increased by a factor of about four when measured with smaller stimuli. In contrast, L- and M-cone-driven responses in this frequency region did not change substantially with stimulus size. At high temporal frequencies (≥ 24 Hz), both rod- and cone-driven response amplitudes decreased with decreasing stimulus size. Signals obtained from rod-isolating stimuli under these conditions are likely artefactual. Interestingly, in RP patients, both rod-driven and L-cone-driven ERGs were similar using 40° and FF stimuli. The increased responses with smaller stimuli in normal subjects to rod-isolating stimuli indicate that a fundamentally different mechanism drives the ERGs in comparison with the cone-driven responses. We propose that the increased responses are caused by stray light stimulating the peripheral retina, thereby allowing peripheral rod-driven function to be studied using the triple silent substitution technique at photopic luminances. The method is effective in studying impaired peripheral rod- and cone- function in RP patients.

The analysis of image motion by the rabbit retina

PubMed Central

Oyster, C. W.

1968-01-01

1. Micro-electrode recordings were made from rabbit retinal ganglion cells or their axons. Of particular interest were direction-selective units; the common on—off type represented 20·6% of the total sample (762 units), and the on-type comprised 5% of the total. 2. From the large sample of direction-selective units, it was found that on—off units were maximally sensitive to only four directions of movement; these directions, in the visual field, were, roughly, anterior, superior, posterior and inferior. The on-type units were maximally sensitive to only three directions: anterior, superior and inferior. 3. The direction-selective unit's responses vary with stimulus velocity; both unit types are more sensitive to velocity change than to absolute speed. On—off units respond to movement at speeds from 6′/sec to 10°/sec; the on-type units responded as slowly as 30″/sec up to about 2°/sec. On-type units are clearly slow-movement detectors. 4. The distribution of direction-selective units depends on the retinal locality. On—off units are more common outside the `visual streak' (area centralis) than within it, while the reverse is true for the on-type units. 5. A stimulus configuration was found which would elicit responses from on-type units when the stimulus was moved in the null direction. This `paradoxical response' was shown to be associated with the silent receptive field surround. 6. The four preferred directions of the on—off units were shown to correspond to the directions of retinal image motion produced by contractions of the four rectus eye muscles. This fact, combined with data on velocity sensitivity and retinal distribution of on—off units, suggests that the on—off units are involved in control of reflex eye movements. 7. The on—off direction-selective units may provide error signals to a visual servo system which minimizes retinal image motion. This hypothesis agrees with the known characteristics of the rabbit's visual following reflexes, specifically, the slow phase of optokinetic nystagmus. PMID:5710424

Unit Price and Choice in a Token-Reinforcement Context

ERIC Educational Resources Information Center

Foster, Theresa A.; Hackenberg, Timothy D.

2004-01-01

Pigeons were exposed to multiple and concurrent second-order schedules of token reinforcement, with stimulus lights serving as token reinforcers. Tokens were produced and exchanged for food according to various fixed-ratio schedules, yielding equal and unequal unit prices (responses per unit food delivery). On one schedule (termed the "standard…

Consolidation of an extinction memory depends on the unconditioned stimulus magnitude previously experienced during training.

PubMed

Stollhoff, Nicola; Eisenhardt, Dorothea

2009-07-29

Here, we examine the role of the magnitude of the unconditioned stimulus (US) during classical conditioning in consolidation processes after memory retrieval. We varied the US durations during training and we test the impact of these variations on consolidation after memory retrieval with one or two conditioned stimulus-only trials. We found that the consolidation of an extinction memory depends on US duration during training and ruled out the possibility that this effect is attributable to differences in satiation after conditioning. We conclude that consolidation of an extinction memory is triggered only when the duration of the US reaches a critical threshold. This demonstrates that memory consolidation cannot be regarded as an isolated process depending solely on training conditions. Instead, it depends on the animal's previous experience as well.

Acquisition of linguistic procedures for printed words: neuropsychological implications for learning.

PubMed

Berninger, V W

1988-10-01

A microcomputerized experiment, administered to 45 children in the 2nd, 5th, and 8th month of first grade, manipulated three variables: (a) stimulus unit (whole word or letter-by-letter presentation), (b) nature of stimulus information (phonically regular words, phonically irregular words, nonsense words, and letter strings, which differ in whether phonemic, orthographic, semantic, and/or name codes are available), and (c) linguistic task (lexical decision, naming, and written reproduction). Letter-by-letter presentation resulted in more accurate lexical decision and naming but not more accurate written reproduction. Interactions between nature of stimulus information and linguistic task occurred. Throughout the year, accuracy was greater for lexical decision than for naming or written reproduction. The superiority of lexical decision cannot be attributed to the higher probability of correct responses on a binary choice task because only consistently correct responses on repeated trials were analyzed. The earlier development of lexical decision, a receptive task, than of naming or written reproduction, production tasks, suggests that hidden units (Hinton & Sejnowski, 1986) in tertiary cortical areas may abstract visual-linguistic associations in printed words before production units in primary cortical areas can produce printed words orally or graphically.

Rudimentary Reading Repertoires via Stimulus Equivalence and Recombination of Minimal Verbal Units

PubMed Central

Matos, Maria Amelia; Avanzi, Alessandra Lopes; McIlvane, William J

2006-01-01

We report a study with sixteen low-SES Brazilian children that sought to establish a repertoire of relations involving dictated words, printed words, and corresponding pictures. Children were taught: (1) in response to dictated words, to select corresponding pictures; (2) in response to syllables presented in both visual and auditory formats, to select words which contained a corresponding syllable in either the first or the last position; (3) in response to dictated-word samples, to “construct” corresponding printed words via arranging their constituent syllabic components; and (4) in response to printed word samples, to construct identical printed words by arranging their syllabic constituents. After training on the first two types of tasks, children were given tests for potentially emergent relations involving printed words and pictures. Almost all exhibited relations consistent with stimulus equivalence. They also displayed emergent naming performances––not only with training words but also with new words that were recombinations of their constituent syllables. The present work was inspired by Sidman's stimulus equivalence paradigm and by Skinner's functional analysis of verbal relations, particularly as applied to conceptions of minimal behavioral units and creativity (i.e., behavioral flexibility) in the analytical units applied to verbal relations. PMID:22477340

Heterogeneity in the spatial receptive field architecture of multisensory neurons of the superior colliculus and its effects on multisensory integration

PubMed Central

Ghose, Dipanwita; Wallace, Mark T.

2013-01-01

Multisensory integration has been widely studied in neurons of the mammalian superior colliculus (SC). This has led to the description of various determinants of multisensory integration, including those based on stimulus- and neuron-specific factors. The most widely characterized of these illustrate the importance of the spatial and temporal relationships of the paired stimuli as well as their relative effectiveness in eliciting a response in determining the final integrated output. Although these stimulus-specific factors have generally been considered in isolation (i.e., manipulating stimulus location while holding all other factors constant), they have an intrinsic interdependency that has yet to be fully elucidated. For example, changes in stimulus location will likely also impact both the temporal profile of response and the effectiveness of the stimulus. The importance of better describing this interdependency is further reinforced by the fact that SC neurons have large receptive fields, and that responses at different locations within these receptive fields are far from equivalent. To address these issues, the current study was designed to examine the interdependency between the stimulus factors of space and effectiveness in dictating the multisensory responses of SC neurons. The results show that neuronal responsiveness changes dramatically with changes in stimulus location – highlighting a marked heterogeneity in the spatial receptive fields of SC neurons. More importantly, this receptive field heterogeneity played a major role in the integrative product exhibited by stimulus pairings, such that pairings at weakly responsive locations of the receptive fields resulted in the largest multisensory interactions. Together these results provide greater insight into the interrelationship of the factors underlying multisensory integration in SC neurons, and may have important mechanistic implications for multisensory integration and the role it plays in shaping SC mediated behaviors. PMID:24183964

Statistical context shapes stimulus-specific adaptation in human auditory cortex.

PubMed

Herrmann, Björn; Henry, Molly J; Fromboluti, Elisa Kim; McAuley, J Devin; Obleser, Jonas

2015-04-01

Stimulus-specific adaptation is the phenomenon whereby neural response magnitude decreases with repeated stimulation. Inconsistencies between recent nonhuman animal recordings and computational modeling suggest dynamic influences on stimulus-specific adaptation. The present human electroencephalography (EEG) study investigates the potential role of statistical context in dynamically modulating stimulus-specific adaptation by examining the auditory cortex-generated N1 and P2 components. As in previous studies of stimulus-specific adaptation, listeners were presented with oddball sequences in which the presentation of a repeated tone was infrequently interrupted by rare spectral changes taking on three different magnitudes. Critically, the statistical context varied with respect to the probability of small versus large spectral changes within oddball sequences (half of the time a small change was most probable; in the other half a large change was most probable). We observed larger N1 and P2 amplitudes (i.e., release from adaptation) for all spectral changes in the small-change compared with the large-change statistical context. The increase in response magnitude also held for responses to tones presented with high probability, indicating that statistical adaptation can overrule stimulus probability per se in its influence on neural responses. Computational modeling showed that the degree of coadaptation in auditory cortex changed depending on the statistical context, which in turn affected stimulus-specific adaptation. Thus the present data demonstrate that stimulus-specific adaptation in human auditory cortex critically depends on statistical context. Finally, the present results challenge the implicit assumption of stationarity of neural response magnitudes that governs the practice of isolating established deviant-detection responses such as the mismatch negativity. Copyright © 2015 the American Physiological Society.

Abstract feature codes: The building blocks of the implicit learning system.

PubMed

Eberhardt, Katharina; Esser, Sarah; Haider, Hilde

2017-07-01

According to the Theory of Event Coding (TEC; Hommel, Müsseler, Aschersleben, & Prinz, 2001), action and perception are represented in a shared format in the cognitive system by means of feature codes. In implicit sequence learning research, it is still common to make a conceptual difference between independent motor and perceptual sequences. This supposedly independent learning takes place in encapsulated modules (Keele, Ivry, Mayr, Hazeltine, & Heuer 2003) that process information along single dimensions. These dimensions have remained underspecified so far. It is especially not clear whether stimulus and response characteristics are processed in separate modules. Here, we suggest that feature dimensions as they are described in the TEC should be viewed as the basic content of modules of implicit learning. This means that the modules process all stimulus and response information related to certain feature dimensions of the perceptual environment. In 3 experiments, we investigated by means of a serial reaction time task the nature of the basic units of implicit learning. As a test case, we used stimulus location sequence learning. The results show that a stimulus location sequence and a response location sequence cannot be learned without interference (Experiment 2) unless one of the sequences can be coded via an alternative, nonspatial dimension (Experiment 3). These results support the notion that spatial location is one module of the implicit learning system and, consequently, that there are no separate processing units for stimulus versus response locations. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Isolating spectral cues in amplitude and quasi-frequency modulation discrimination by reducing stimulus duration.

PubMed

Borucki, Ewa; Berg, Bruce G

2017-05-01

This study investigated the psychophysical effects of distortion products in a listening task traditionally used to estimate the bandwidth of phase sensitivity. For a 2000 Hz carrier, estimates of modulation depth necessary to discriminate amplitude modulated (AM) tones and quasi-frequency modulated (QFM) were measured in a two interval forced choice task as a function modulation frequency. Temporal modulation transfer functions were often non-monotonic at modulation frequencies above 300 Hz. This was likely to be due to a spectral cue arising from the interaction of auditory distortion products and the lower sideband of the stimulus complex. When the stimulus duration was decreased from 200 ms to 20 ms, thresholds for low-frequency modulators rose to near-chance levels, whereas thresholds in the region of non-monotonicities were less affected. The decrease in stimulus duration appears to hinder the listener's ability to use temporal cues in order to discriminate between AM and QFM, whereas spectral information derived from distortion product cues appears more resilient. Copyright © 2017. Published by Elsevier B.V.

Non-linearity of visual evoked potentials in cerveau isolé and midpontine pretrigeminal cats.

PubMed

Shibagaki, M; Kiyono, S; Kawashima, T; Watanabe, S

1985-01-01

Characteristics of the visual evoked responses to the flickering flash stimulation were studied in the cerveau isolé and midpontine pretrigeminal cats. The flash stimulation frequency was changed stepwise between 1 and 30 Hz in increasing and decreasing order. In all cases of both preparations, with drawing of fixed sweep speed of 200 msec in whole length, P1 and N1 latencies in the successive response slightly prolonged progressively 1 to about 20 Hz and thereafter shortened about 20-30 Hz stimulus frequencies in the course of the increasing phase, and vice versa in the course of the decreasing phase. Moreover, no difference in each latency (P1, N1, P2, N2) was found at the same stimulus frequency during increasing and decreasing phases. In the amplitude taken from the P1-N1 component, the peak was found in 5-9 Hz frequency bands. This peak was higher during the decreasing phase than during the increasing phase, which indicated a hysteresis phenomenon. A peak of power for the 1st harmonics was found at 3-6 Hz driving frequency bands, and that of the 2nd harmonics at 6-10 Hz. In the state without flash stimulus, no peaks or valleys in the power spectrum were found in specific frequencies, for example 3-10 Hz. The peak in the amplitude and that in the power spectrum at 3-10 Hz stimulus frequency bands suggested an entrainment phenomenon induced by forced oscillation. The phenomena of entrainment and hysteresis suggest the existence of a non-linear structure in the oscillation generating systems of visual evoked response.

Neural Network Analysis of Musculoskeletal Responses to Electrical AC-Stimulus

DTIC Science & Technology

2001-10-25

FAM, SOM I. INTRODUCTION Various kinds of electrical measurements have been used to investigate the human body, including the mechanical or chemical...measurements were obtained from five points; namely, the patients’ wrists, ankles and back. The electrodes of an IF Electrotherapy unit [5] were attached...musculoskeletal responses to electrical AC-stimulus M. Hannula1, E. Alasaarela2 , J. Laitinen1 1Institute of Technology , Oulu Polytechnic, Oulu, Finland

[Relationship of distortion product in cochlea with cochlear activity revealed by laser interferometry].

PubMed

Long, Xianming; Zhang, Yanping; Lu, Jie; Long, Changcai

2015-09-01

To study the relationship of distortion product in cochlea with cochlear activity and hearing. Time variances of distortion product of basilar membrane vibration in vitro guineapig cochlea were observed by laser interferometry. Within half hour after a cochlea was isolated from a guineapig, distortion product accompanied with two-tone inhibition in cochlea, can be observed. As time passed, distortion product and two-tone inhibition effect disappeared at the same time. After that, the membrane contiune vibrating in response to the sound stimulus, but the vibration amplitude decreased obviously and continued decreasing until it disappeared completely. Distortion product in cochlea is a symbol of cochlear activity which makes the membrane respond in large amplitude vibration to sound stimulus and exhibit two-tone inhibition. The former makes the hearing highly sensitive to sound stimulus, the later makes the hearing perform information abstract well.

Capsaicin modulates acetylcholine release at the myoneural junction.

PubMed

Thyagarajan, Baskaran; Potian, Joseph G; Baskaran, Padmamalini; McArdle, Joseph J

2014-12-05

Transient receptor potential (TRP) proteins are non-selective cation channel proteins that are expressed throughout the body. Previous studies demonstrated the expression of TRP Vanilloid 1 (TRPV1), capsaicin (CAP) receptor, in sensory neurons. Recently, we reported TRPV1 expression in mouse motor nerve terminals [MNTs; (Thyagarajan et al., 2009)], where we observed that CAP protected MNTs from botulinum neurotoxin A (BoNT/A). Phrenic nerve diaphragm nerve muscle preparations (NMP) isolated from isoflurane anesthetized adult mice were analyzed for twitch tension, spontaneous (mEPCs) and nerve stimulus evoked (EPCs) acetylcholine release. When acutely applied to isolated NMP, CAP produced a concentration-dependent decline of twitch tension and produced a significant decline in the amplitude of EPCs and quantal content without any effect on the mEPCs. The suppression of nerve stimulus evoked acetylcholine release by CAP was antagonized by capsazepine (CPZ), a TRPV1 antagonist. CAP did not suppress phrenic nerve stimulus evoked acetylcholine release in TRPV1 knockout mice. Also, CAP treatment, in vitro, interfered with the localization of adapter protein 2 in cholinergic Neuro 2a cells. Wortmannin, (WMN; non-selective phosphoinositol kinase inhibitor), mimicked the effects of CAP by inhibiting the acetylcholine exocytosis. Our data suggest that TRPV1 proteins expressed at the MNT are coupled to the exo-endocytic mechanisms to regulate neuromuscular functions. Copyright © 2014 Elsevier B.V. All rights reserved.

Different effects of isolation-rearing and neonatal MK-801 treatment on attentional modulations of prepulse inhibition of startle in rats.

PubMed

Wu, Zhe-Meng; Ding, Yu; Jia, Hong-Xiao; Li, Liang

2016-09-01

Prepulse inhibition (PPI) is suppression of the startle reflex by a weaker sensory stimulus (prepulse) preceding the startling stimulus. In people with schizophrenia, impairment of attentional modulation of PPI, but not impairment of baseline PPI, is correlated with symptom severity. In rats, both fear conditioning of prepulse and perceptually spatial separation between the conditioned prepulse and a noise masker enhance PPI (the paradigms of attentional modulation of PPI). As a neurodevelopmental model of schizophrenia, isolation rearing impairs both baseline PPI and attentional modulations of PPI in rats. This study examined in Sprague-Dawley male rats whether neonatally blocking N-methyl-D-aspartate (NMDA) receptors specifically affects attentional modulations of PPI during adulthood. Both socially reared rats with neonatal exposure to the NMDA receptor antagonist MK-801 and isolation-reared rats exhibited augmented startle responses, but only isolation rearing impaired baseline PPI. Fear conditioning of the prepulse enhanced PPI in socially reared rats, but MK-801-treated rats lost the prepulse feature specificity. Perceptually spatial separation between the conditioned prepulse and a noise masker further enhanced PPI only in normally reared rats. Clozapine administration during adulthood generally weakened startle, enhanced baseline PPI in neonatally interrupted rats, and restored the fear conditioning-induced PPI enhancement in isolation-reared rats with a loss of the prepulse feature specificity. Clozapine administration also abolished both the perceptual separation-induced PPI enhancement in normally reared rats and the fear conditioning-induced PPI enhancement in MK-801-treated rats. Isolation rearing impairs both baseline PPI and attentional modulations of PPI, but neonatally disrupting NMDA receptor-mediated transmissions specifically impair attentional modulations of PPI. Clozapine has limited alleviating effects.

Habituation of the orienting reflex and the development of Preliminary Process Theory.

PubMed

Barry, Robert J

2009-09-01

The orienting reflex (OR), elicited by an innocuous stimulus, can be regarded as a model of the organism's interaction with its environment, and has been described as the unit of attentional processing. A major determinant of the OR is the novelty of the eliciting stimulus, generally operationalized in terms of its reduction with stimulus repetition, the effects of which are commonly described in habituation terms. This paper provides an overview of a research programme, spanning more than 30 years, investigating psychophysiological aspects of the OR in humans. The major complication in this research is that the numerous physiological measures used as dependent variables in the OR context fail to jointly covary with stimulus parameters. This has led to the development of the Preliminary Process Theory (PPT) of the OR to accommodate the complexity of the observed stimulus-response patterns. PPT is largely grounded in autonomic measures, and current work is attempting to integrate electroencephalographic measures, particularly components in the event-related brain potentials reflecting aspects of stimulus processing. The emphasis in the current presentation is on the use of the defining criteria of the habituation phenomenon, and Groves and Thompson's Dual-process Theory, in the development of PPT.

Blur-resistant perimetric stimuli.

PubMed

Horner, Douglas G; Dul, Mitchell W; Swanson, William H; Liu, Tiffany; Tran, Irene

2013-05-01

To develop perimetric stimuli that are resistant to the effects of peripheral defocus. One eye each was tested on subjects free of eye disease. Experiment 1 assessed spatial frequency, testing 12 subjects at eccentricities from 2 to 7 degrees using blur levels from 0 to 3 diopters (D) for two (Gabor) stimuli (spatial SD, 0.5 degrees; spatial frequencies, 0.5 and 1.0 cycles per degree [cpd]). Experiment 2 assessed stimulus size, testing 12 subjects at eccentricities from 4 to 7 degrees using blur levels 0 to 6 D for two Gaussians with SD of 0.5 and 0.25 degrees and a 0.5-cpd Gabor with SD of 0.5 degrees. Experiment 3 tested 13 subjects at eccentricities from fixation to 27 degrees using blur levels 0 to 6 D for Gabor stimuli at 56 locations; the spatial frequency ranged from 0.14 to 0.50 cpd with location, and SD was scaled accordingly. In experiment 1, blur by 3 D caused a small decline in log contrast sensitivity for the 0.5-cpd stimulus (mean ± SE, 0.09 ± 0.08 log units) and a larger (t = 7.7, p < 0.0001) decline for the 1.0-cpd stimulus (0.37 ± 0.13 log units). In experiment 2, blur by 6 D caused minimal decline for the larger Gaussian, by 0.17 ± 0.16 log units, and larger (t > 4.5, p < 0.001) declines for the smaller Gaussian (0.33 ± 0.16 log units) and the Gabor (0.36 ± 0.18 log units). In experiment 3, blur by 6 D caused declines by 0.27 ± 0.05 log units for eccentricities from 0 to 10 degrees, by 0.20 ± 0.04 log units for eccentricities from 10 to 20 degrees, and 0.13 ± 0.03 log units for eccentricities from 20 to 27 degrees. Experiments 1 and 2 allowed us to design stimuli for experiment 3 that were resistant to effects of peripheral defocus.

Teaching generatively: Learning about disorders and disabilities.

PubMed

Alter, Margaret M; Borrero, John C

2015-01-01

Stimulus equivalence procedures have been used to teach course material in higher education in the laboratory and in the classroom. The current study was a systematic replication of Walker, Rehfeldt, and Ninness (2010), who used a stimulus equivalence procedure to train information pertaining to 12 disorders. Specifically, we conducted (a) a written posttest immediately after each training unit and (b) booster training sessions for poor performers. Results showed immediate improvement from pretest to posttest scores after training, but problems with maintenance were noted in the final examination. Implications of poor maintenance are discussed in the context of the current study and stimulus equivalence research in higher education generally. © Society for the Experimental Analysis of Behavior.

Effects of Oral Stimulus Frequency Spectra on the Development of Non-nutritive Suck in Preterm Infants with Respiratory Distress Syndrome or Chronic Lung Disease, and Preterm Infants of Diabetic Mothers

PubMed Central

Barlow, SM; Lee, Jaehoon; Wang, Jingyan; Oder, Austin; Oh, Hyuntaek; Hall, Sue; Knox, Kendi; Weatherstone, Kathleen; Thompson, Diane

2013-01-01

The precocial nature of orofacial sensorimotor control underscores the biological importance of establishing ororythmic activity in human infants. The purpose of this study was to assess the effects of comparable doses of three forms of orosensory experience, including a low-velocity spectrally reduced orocutaneous stimulus (NT1), a high-velocity broad spectrum orocutaneous stimulus (NT2), and a SHAM stimulus consisting of a blind pacifier. Each orosensory experience condition was paired with gavage feedings 3x/day for 10 days in the neonatal intensive care unit (NICU). Four groups of preterm infants (N=214), including those with respiratory distress syndrome (RDS), chronic lung disease (CLD), infants of diabetic mothers (IDM), and healthy controls (HI) were randomized to the type of orosensory condition. Mixed modeling, adjusted for gender, gestational age, postmenstrual age, and birth weight, demonstrated the most significant gains in non-nutritive suck (NNS) development among CLD infants who were treated with the NT2 stimulus, with smaller gains realized among RDS and IDM infants. The broader spectrum of the NT2 stimulus maps closely to known response properties of mechanoreceptors in lip, tongue, and oral mucosa and is more effective in promoting NNS development among preterm infants with impaired oromotor function compared to the low-velocity, spectrally reduced NT1 orosensory stimulus. PMID:25018662

Heterogeneity in the spatial receptive field architecture of multisensory neurons of the superior colliculus and its effects on multisensory integration.

PubMed

Ghose, D; Wallace, M T

2014-01-03

Multisensory integration has been widely studied in neurons of the mammalian superior colliculus (SC). This has led to the description of various determinants of multisensory integration, including those based on stimulus- and neuron-specific factors. The most widely characterized of these illustrate the importance of the spatial and temporal relationships of the paired stimuli as well as their relative effectiveness in eliciting a response in determining the final integrated output. Although these stimulus-specific factors have generally been considered in isolation (i.e., manipulating stimulus location while holding all other factors constant), they have an intrinsic interdependency that has yet to be fully elucidated. For example, changes in stimulus location will likely also impact both the temporal profile of response and the effectiveness of the stimulus. The importance of better describing this interdependency is further reinforced by the fact that SC neurons have large receptive fields, and that responses at different locations within these receptive fields are far from equivalent. To address these issues, the current study was designed to examine the interdependency between the stimulus factors of space and effectiveness in dictating the multisensory responses of SC neurons. The results show that neuronal responsiveness changes dramatically with changes in stimulus location - highlighting a marked heterogeneity in the spatial receptive fields of SC neurons. More importantly, this receptive field heterogeneity played a major role in the integrative product exhibited by stimulus pairings, such that pairings at weakly responsive locations of the receptive fields resulted in the largest multisensory interactions. Together these results provide greater insight into the interrelationship of the factors underlying multisensory integration in SC neurons, and may have important mechanistic implications for multisensory integration and the role it plays in shaping SC-mediated behaviors. Copyright © 2013 IBRO. Published by Elsevier Ltd. All rights reserved.

Variability and Correlations in Primary Visual Cortical Neurons Driven by Fixational Eye Movements

PubMed Central

McFarland, James M.; Cumming, Bruce G.

2016-01-01

The ability to distinguish between elements of a sensory neuron's activity that are stimulus independent versus driven by the stimulus is critical for addressing many questions in systems neuroscience. This is typically accomplished by measuring neural responses to repeated presentations of identical stimuli and identifying the trial-variable components of the response as noise. In awake primates, however, small “fixational” eye movements (FEMs) introduce uncontrolled trial-to-trial differences in the visual stimulus itself, potentially confounding this distinction. Here, we describe novel analytical methods that directly quantify the stimulus-driven and stimulus-independent components of visual neuron responses in the presence of FEMs. We apply this approach, combined with precise model-based eye tracking, to recordings from primary visual cortex (V1), finding that standard approaches that ignore FEMs typically miss more than half of the stimulus-driven neural response variance, creating substantial biases in measures of response reliability. We show that these effects are likely not isolated to the particular experimental conditions used here, such as the choice of visual stimulus or spike measurement time window, and thus will be a more general problem for V1 recordings in awake primates. We also demonstrate that measurements of the stimulus-driven and stimulus-independent correlations among pairs of V1 neurons can be greatly biased by FEMs. These results thus illustrate the potentially dramatic impact of FEMs on measures of signal and noise in visual neuron activity and also demonstrate a novel approach for controlling for these eye-movement-induced effects. SIGNIFICANCE STATEMENT Distinguishing between the signal and noise in a sensory neuron's activity is typically accomplished by measuring neural responses to repeated presentations of an identical stimulus. For recordings from the visual cortex of awake animals, small “fixational” eye movements (FEMs) inevitably introduce trial-to-trial variability in the visual stimulus, potentially confounding such measures. Here, we show that FEMs often have a dramatic impact on several important measures of response variability for neurons in primary visual cortex. We also present an analytical approach for quantifying signal and noise in visual neuron activity in the presence of FEMs. These results thus highlight the importance of controlling for FEMs in studies of visual neuron function, and demonstrate novel methods for doing so. PMID:27277801

Stimulus-Food Pairings Produce Stimulus-Directed Touch-Screen Responding in Cynomolgus Monkeys (MACACA Fascicularis) With or Without a Positive Response Contingency

DTIC Science & Technology

2009-07-01

REPORT NUMBER US Army Medical Research Institute of Chemical Defense ATTN: MCMR-CDT-N 3100 Ricketts Point Road Aberdeen Proving Ground, MD...Medical Research Institute of Chemical Defense Aberdeen Proving Ground, MD 21010-5400 ATTN: MCMR-CDZ-I 11. SPONSOR/MONITOR’S REPORT 3100 Ricketts...CONTINGENCY CHRISTOPHER E. BULLOCK AND TODD M. MYERS UNITED STATES ARMY MEDICAL RESEARCH INSTITUTE OF CHEMICAL DEFENSE Acquisition and maintenance of

A tandem affinity purification tag of TGA2 for isolation of interacting proteins in Arabidopsis thaliana

PubMed Central

Stotz, Henrik U; Findling, Simone; Nukarinen, Ella; Weckwerth, Wolfram; Mueller, Martin J; Berger, Susanne

2014-01-01

Tandem affinity purification (TAP) tagging provides a powerful tool for isolating interacting proteins in vivo. TAP-tag purification offers particular advantages for the identification of stimulus-induced protein interactions. Type II bZIP transcription factors (TGA2, TGA5 and TGA6) play key roles in pathways that control salicylic acid, ethylene, xenobiotic and reactive oxylipin signaling. Although proteins interacting with these transcription factors have been identified through genetic and yeast 2-hybrid screening, others are still elusive. We have therefore generated a C-terminal TAP-tag of TGA2 to isolate additional proteins that interact with this transcription factor. Three lines most highly expressing TAP-tagged TGA2 were functional in that they partially complemented reactive oxylipin-responsive gene expression in a tga2 tga5 tga6 triple mutant. TAP-tagged TGA2 in the most strongly overexpressing line was proteolytically less stable than in the other 2 lines. Only this overexpressing line could be used in a 2-step purification process, resulting in isolation of co-purifying bands of larger molecular weight than TGA2. TAP-tagged TGA2 was used to pull down NPR1, a protein known to interact with this transcription factor. Mass spectrometry was used to identify peptides that co-purified with TAP-tagged TGA2. Having generated this TGA2 TAP-tag line will therefore be an asset to researchers interested in stimulus-induced signal transduction processes. PMID:25482810

Neural timing signal for precise tactile timing judgments

PubMed Central

Watanabe, Junji; Nishida, Shin'ya

2016-01-01

The brain can precisely encode the temporal relationship between tactile inputs. While behavioural studies have demonstrated precise interfinger temporal judgments, the underlying neural mechanism remains unknown. Computationally, two kinds of neural responses can act as the information source. One is the phase-locked response to the phase of relatively slow inputs, and the other is the response to the amplitude change of relatively fast inputs. To isolate the contributions of these components, we measured performance of a synchrony judgment task for sine wave and amplitude-modulation (AM) wave stimuli. The sine wave stimulus was a low-frequency sinusoid, with the phase shifted in the asynchronous stimulus. The AM wave stimulus was a low-frequency sinusoidal AM of a 250-Hz carrier, with only the envelope shifted in the asynchronous stimulus. In the experiment, three stimulus pairs, two synchronous ones and one asynchronous one, were sequentially presented to neighboring fingers, and participants were asked to report which one was the asynchronous pair. We found that the asynchrony of AM waves could be detected as precisely as single impulse pair, with the threshold asynchrony being ∼20 ms. On the other hand, the asynchrony of sine waves could not be detected at all in the range from 5 to 30 Hz. Our results suggest that the timing signal for tactile judgments is provided not by the stimulus phase information but by the envelope of the response of the high-frequency-sensitive Pacini channel (PC), although they do not exclude a possible contribution of the envelope of non-PCs. PMID:26843600

A circuit for detection of interaural time differences in the nucleus laminaris of turtles.

PubMed

Willis, Katie L; Carr, Catherine E

2017-11-15

The physiological hearing range of turtles is approximately 50-1000 Hz, as determined by cochlear microphonics ( Wever and Vernon, 1956a). These low frequencies can constrain sound localization, particularly in red-eared slider turtles, which are freshwater turtles with small heads and isolated middle ears. To determine if these turtles were sensitive to interaural time differences (ITDs), we investigated the connections and physiology of their auditory brainstem nuclei. Tract tracing experiments showed that cranial nerve VIII bifurcated to terminate in the first-order nucleus magnocellularis (NM) and nucleus angularis (NA), and the NM projected bilaterally to the nucleus laminaris (NL). As the NL received inputs from each side, we developed an isolated head preparation to examine responses to binaural auditory stimulation. Magnocellularis and laminaris units responded to frequencies from 100 to 600 Hz, and phase-locked reliably to the auditory stimulus. Responses from the NL were binaural, and sensitive to ITD. Measures of characteristic delay revealed best ITDs around ±200 μs, and NL neurons typically had characteristic phases close to 0, consistent with binaural excitation. Thus, turtles encode ITDs within their physiological range, and their auditory brainstem nuclei have similar connections and cell types to other reptiles. © 2017. Published by The Company of Biologists Ltd.

Sound-by-sound thalamic stimulation modulates midbrain auditory excitability and relative binaural sensitivity in frogs

PubMed Central

Ponnath, Abhilash; Farris, Hamilton E.

2014-01-01

Descending circuitry can modulate auditory processing, biasing sensitivity to particular stimulus parameters and locations. Using awake in vivo single unit recordings, this study tested whether electrical stimulation of the thalamus modulates auditory excitability and relative binaural sensitivity in neurons of the amphibian midbrain. In addition, by using electrical stimuli that were either longer than the acoustic stimuli (i.e., seconds) or presented on a sound-by-sound basis (ms), experiments addressed whether the form of modulation depended on the temporal structure of the electrical stimulus. Following long duration electrical stimulation (3–10 s of 20 Hz square pulses), excitability (spikes/acoustic stimulus) to free-field noise stimuli decreased by 32%, but returned over 600 s. In contrast, sound-by-sound electrical stimulation using a single 2 ms duration electrical pulse 25 ms before each noise stimulus caused faster and varied forms of modulation: modulation lasted <2 s and, in different cells, excitability either decreased, increased or shifted in latency. Within cells, the modulatory effect of sound-by-sound electrical stimulation varied between different acoustic stimuli, including for different male calls, suggesting modulation is specific to certain stimulus attributes. For binaural units, modulation depended on the ear of input, as sound-by-sound electrical stimulation preceding dichotic acoustic stimulation caused asymmetric modulatory effects: sensitivity shifted for sounds at only one ear, or by different relative amounts for both ears. This caused a change in the relative difference in binaural sensitivity. Thus, sound-by-sound electrical stimulation revealed fast and ear-specific (i.e., lateralized) auditory modulation that is potentially suited to shifts in auditory attention during sound segregation in the auditory scene. PMID:25120437

Sound-by-sound thalamic stimulation modulates midbrain auditory excitability and relative binaural sensitivity in frogs.

PubMed

Ponnath, Abhilash; Farris, Hamilton E

2014-01-01

Descending circuitry can modulate auditory processing, biasing sensitivity to particular stimulus parameters and locations. Using awake in vivo single unit recordings, this study tested whether electrical stimulation of the thalamus modulates auditory excitability and relative binaural sensitivity in neurons of the amphibian midbrain. In addition, by using electrical stimuli that were either longer than the acoustic stimuli (i.e., seconds) or presented on a sound-by-sound basis (ms), experiments addressed whether the form of modulation depended on the temporal structure of the electrical stimulus. Following long duration electrical stimulation (3-10 s of 20 Hz square pulses), excitability (spikes/acoustic stimulus) to free-field noise stimuli decreased by 32%, but returned over 600 s. In contrast, sound-by-sound electrical stimulation using a single 2 ms duration electrical pulse 25 ms before each noise stimulus caused faster and varied forms of modulation: modulation lasted <2 s and, in different cells, excitability either decreased, increased or shifted in latency. Within cells, the modulatory effect of sound-by-sound electrical stimulation varied between different acoustic stimuli, including for different male calls, suggesting modulation is specific to certain stimulus attributes. For binaural units, modulation depended on the ear of input, as sound-by-sound electrical stimulation preceding dichotic acoustic stimulation caused asymmetric modulatory effects: sensitivity shifted for sounds at only one ear, or by different relative amounts for both ears. This caused a change in the relative difference in binaural sensitivity. Thus, sound-by-sound electrical stimulation revealed fast and ear-specific (i.e., lateralized) auditory modulation that is potentially suited to shifts in auditory attention during sound segregation in the auditory scene.

Dissociating hippocampal and striatal contributions to sequential prediction learning

PubMed Central

Bornstein, Aaron M.; Daw, Nathaniel D.

2011-01-01

Behavior may be generated on the basis of many different kinds of learned contingencies. For instance, responses could be guided by the direct association between a stimulus and response, or by sequential stimulus-stimulus relationships (as in model-based reinforcement learning or goal-directed actions). However, the neural architecture underlying sequential predictive learning is not well-understood, in part because it is difficult to isolate its effect on choice behavior. To track such learning more directly, we examined reaction times (RTs) in a probabilistic sequential picture identification task. We used computational learning models to isolate trial-by-trial effects of two distinct learning processes in behavior, and used these as signatures to analyze the separate neural substrates of each process. RTs were best explained via the combination of two delta rule learning processes with different learning rates. To examine neural manifestations of these learning processes, we used functional magnetic resonance imaging to seek correlates of timeseries related to expectancy or surprise. We observed such correlates in two regions, hippocampus and striatum. By estimating the learning rates best explaining each signal, we verified that they were uniquely associated with one of the two distinct processes identified behaviorally. These differential correlates suggest that complementary anticipatory functions drive each region's effect on behavior. Our results provide novel insights as to the quantitative computational distinctions between medial temporal and basal ganglia learning networks and enable experiments that exploit trial-by-trial measurement of the unique contributions of both hippocampus and striatum to response behavior. PMID:22487032

A comparison of methods for teaching receptive labeling to children with autism spectrum disorders.

PubMed

Grow, Laura L; Carr, James E; Kodak, Tiffany M; Jostad, Candice M; Kisamore, April N

2011-01-01

Many early intervention curricular manuals recommend teaching auditory-visual conditional discriminations (i.e., receptive labeling) using the simple-conditional method in which component simple discriminations are taught in isolation and in the presence of a distracter stimulus before the learner is required to respond conditionally. Some have argued that this procedure might be susceptible to faulty stimulus control such as stimulus overselectivity (Green, 2001). Consequently, there has been a call for the use of alternative teaching procedures such as the conditional-only method, which involves conditional discrimination training from the onset of intervention. The purpose of the present study was to compare the simple-conditional and conditional-only methods for teaching receptive labeling to 3 young children diagnosed with autism spectrum disorders. The data indicated that the conditional-only method was a more reliable and efficient teaching procedure. In addition, several error patterns emerged during training using the simple-conditional method. The implications of the results with respect to current teaching practices in early intervention programs are discussed.

Measurement of hearing aid internal noise1

PubMed Central

Lewis, James D.; Goodman, Shawn S.; Bentler, Ruth A.

2010-01-01

Hearing aid equivalent input noise (EIN) measures assume the primary source of internal noise to be located prior to amplification and to be constant regardless of input level. EIN will underestimate internal noise in the case that noise is generated following amplification. The present study investigated the internal noise levels of six hearing aids (HAs). Concurrent with HA processing of a speech-like stimulus with both adaptive features (acoustic feedback cancellation, digital noise reduction, microphone directionality) enabled and disabled, internal noise was quantified for various stimulus levels as the variance across repeated trials. Changes in noise level as a function of stimulus level demonstrated that (1) generation of internal noise is not isolated to the microphone, (2) noise may be dependent on input level, and (3) certain adaptive features may contribute to internal noise. Quantifying internal noise as the variance of the output measures allows for noise to be measured under real-world processing conditions, accounts for all sources of noise, and is predictive of internal noise audibility. PMID:20370034

Isolating Neural Components of Threat Bias in Pediatric Anxiety

ERIC Educational Resources Information Center

Britton, Jennifer C.; Bar-Haim, Yair; Carver, Frederick W.; Holroyd, Tom; Norcross, Maxine A.; Detloff, Allison; Leibenluft, Ellen; Ernst, Monique; Pine, Daniel S.

2012-01-01

Background: Attention biases toward threat are often detected in individuals with anxiety disorders. Threat biases can be measured experimentally through dot-probe paradigms, in which individuals detect a probe following a stimulus pair including a threat. On these tasks, individuals with anxiety tend to detect probes that occur in a location…

Presynaptic (Type III) cells in mouse taste buds sense sour (acid) taste.

PubMed

Huang, Yijen A; Maruyama, Yutaka; Stimac, Robert; Roper, Stephen D

2008-06-15

Taste buds contain two types of cells that directly participate in taste transduction - receptor (Type II) cells and presynaptic (Type III) cells. Receptor cells respond to sweet, bitter and umami taste stimulation but until recently the identity of cells that respond directly to sour (acid) tastants has only been inferred from recordings in situ, from behavioural studies, and from immunostaining for putative sour transduction molecules. Using calcium imaging on single isolated taste cells and with biosensor cells to identify neurotransmitter release, we show that presynaptic (Type III) cells specifically respond to acid taste stimulation and release serotonin. By recording responses in cells isolated from taste buds and in taste cells in lingual slices to acetic acid titrated to different acid levels (pH), we also show that the active stimulus for acid taste is the membrane-permeant, uncharged acetic acid moiety (CH(3)COOH), not free protons (H(+)). That observation is consistent with the proximate stimulus for acid taste being intracellular acidification, not extracellular protons per se. These findings may also have implications for other sensory receptors that respond to acids, such as nociceptors.

Neural basis for eye velocity generation in the vestibular nuclei of alert monkeys during off-vertical axis rotation

NASA Technical Reports Server (NTRS)

Reisine, H.; Raphan, T.; Cohen, B. (Principal Investigator)

1992-01-01

Activity of "vestibular only" (VO) and "vestibular plus saccade" (VPS) units was recorded in the rostral part of the medial vestibular nucleus and caudal part of the superior vestibular nucleus of alert rhesus monkeys. By estimating the "null axes" of recorded units (n = 79), the optimal plane of activation was approximately the mean plane of reciprocal semicircular canals, i.e., lateral canals, left anterior-right posterior (LARP) canals or right anterior-left posterior (RALP) canals. All units were excited by rotation in a direction that excited a corresponding ipsilateral semicircular canal. Thus, they all displayed a "type I" response. With the animal upright, there were rapid changes in firing rates of both VO and VPS units in response to steps of angular velocity about a vertical axis. The units were bidirectionally activated during vestibular nystagmus (VN), horizontal optokinetic nystagmus (OKN), optokinetic after-nystagmus (OKAN) and off-vertical axis rotation (OVAR). The rising and falling time constants of the responses to rotation indicated that they were closely linked to velocity storage. There were differences between VPS and VO neurons in that activity of VO units followed the expected time course in response to a stimulus even during periods of drowsiness, when eye velocity was reduced. Firing rates of VPS units, on the other hand, were significantly reduced in the drowsy state. Lateral canal-related units had average firing rates that were linearly related to the bias or steady state level of horizontal eye velocity during OVAR over a range of +/- 60 deg/s. These units could be further divided into two classes according to whether they were modulated during OVAR. Non-modulated units (n = 5) were VO types and all modulated units (n = 5) were VPS types. There was no significant difference between the bias level sensitivities relative to eye velocity of the units with and without modulation (P > 0.05). The modulated units had no sustained change in firing rate in response to static head tilts and their phases relative to head position varied from unit to unit. The phase did not appear to be linked to the modulation of horizontal eye velocity during OVAR. The sensitivities of unit activity to eye velocity were similar during all stimulus modalities despite the different gains of eye velocity vs stimulus velocity during VN, OKN and OVAR. Therefore, VO and VPS units are likely to carry an eye velocity signal related to velocity storage.(ABSTRACT TRUNCATED AT 400 WORDS).

Spatio-temporal brain dynamics in a combined stimulus-stimulus and stimulus-response conflict task.

PubMed

Frühholz, Sascha; Godde, Ben; Finke, Mareike; Herrmann, Manfred

2011-01-01

It is yet not well known whether different types of conflicts share common or rely on distinct brain mechanisms of conflict processing. We used a combined Flanker (stimulus-stimulus; S-S) and Simon (stimulus-response; S-R) conflict paradigm both in an fMRI and an EEG study. S-S conflicts induced stronger behavioral interference effects compared to S-R conflicts and the latter decayed with increasing response latencies. Besides some similar medial frontal activity across all conflict trials, which was, however, not statically consistent across trials, we especially found distinct activations depending on the type of conflict. S-S conflicts activated the anterior cingulate cortex and modulated the N2 and early P3 component with underlying source activity in inferior frontal cortex. S-R conflicts produced distinct activations in the posterior cingulate cortex and modulated the late P3b component with underlying source activity in superior parietal cortex. Double conflict trials containing both S-S and S-R conflicts revealed, first, distinct anterior frontal activity representing a meta-processing unit and, second, a sequential modulation of the N2 and the P3b component. The N2 modulation during double conflict trials was accompanied by increased source activity in the medial frontal gyrus (MeFG). In summary, S-S and S-R conflict processing mostly rely on distinct mechanisms of conflict processing and these conflicts differentially modulate the temporal stages of stimulus processing. Copyright © 2010 Elsevier Inc. All rights reserved.

Different mechanisms are responsible for dishabituation of electrophysiological auditory responses to a change in acoustic identity than to a change in stimulus location.

PubMed

Smulders, Tom V; Jarvis, Erich D

2013-11-01

Repeated exposure to an auditory stimulus leads to habituation of the electrophysiological and immediate-early-gene (IEG) expression response in the auditory system. A novel auditory stimulus reinstates this response in a form of dishabituation. This has been interpreted as the start of new memory formation for this novel stimulus. Changes in the location of an otherwise identical auditory stimulus can also dishabituate the IEG expression response. This has been interpreted as an integration of stimulus identity and stimulus location into a single auditory object, encoded in the firing patterns of the auditory system. In this study, we further tested this hypothesis. Using chronic multi-electrode arrays to record multi-unit activity from the auditory system of awake and behaving zebra finches, we found that habituation occurs to repeated exposure to the same song and dishabituation with a novel song, similar to that described in head-fixed, restrained animals. A large proportion of recording sites also showed dishabituation when the same auditory stimulus was moved to a novel location. However, when the song was randomly moved among 8 interleaved locations, habituation occurred independently of the continuous changes in location. In contrast, when 8 different auditory stimuli were interleaved all from the same location, a separate habituation occurred to each stimulus. This result suggests that neuronal memories of the acoustic identity and spatial location are different, and that allocentric location of a stimulus is not encoded as part of the memory for an auditory object, while its acoustic properties are. We speculate that, instead, the dishabituation that occurs with a change from a stable location of a sound is due to the unexpectedness of the location change, and might be due to different underlying mechanisms than the dishabituation and separate habituations to different acoustic stimuli. Copyright © 2013 Elsevier Inc. All rights reserved.

Tilt perception during dynamic linear acceleration.

PubMed

Seidman, S H; Telford, L; Paige, G D

1998-04-01

Head tilt is a rotation of the head relative to gravity, as exemplified by head roll or pitch from the natural upright orientation. Tilt stimulates both the otolith organs, owing to shifts in gravitational orientation, and the semicircular canals in response to head rotation, which in turn drive a variety of behavioral and perceptual responses. Studies of tilt perception typically have not adequately isolated otolith and canal inputs or their dynamic contributions. True tilt cannot readily dissociate otolith from canal influences. Alternatively, centrifugation generates centripetal accelerations that simulate tilt, but still entails a rotatory (canal) stimulus during important periods of the stimulus profiles. We reevaluated the perception of head tilt in humans, but limited the stimulus to linear forces alone, thus isolating the influence of otolith inputs. This was accomplished by employing a centrifugation technique with a variable-radius spinning sled. This allowed us to accelerate the sled to a constant angular velocity (128 degrees/s), with the subject centered, and then apply dynamic centripetal accelerations after all rotatory perceptions were extinguished. These stimuli were presented in the subjects' naso-occipital axis by translating the subjects 50 cm eccentrically either forward or backward. Centripetal accelerations were thus induced (0.25 g), which combined with gravity to yield a dynamically shifting gravitoinertial force simulating pitch-tilt, but without actually rotating the head. A magnitude-estimation task was employed to characterize the dynamic perception of pitch-tilt. Tilt perception responded sluggishly to linear acceleration, typically reaching a peak after 10-30 s. Tilt perception also displayed an adaptation phenomenon. Adaptation was manifested as a per-stimulus decline in perceived tilt during prolonged stimulation and a reversal aftereffect upon return to zero acceleration (i.e., recentering the subject). We conclude that otolith inputs can produce tilt perception in the absence of canal stimulation, and that this perception is subject to an adaptation phenomenon and low-pass filtering of its otolith input.

Topographic prominence discriminator for the detection of short-latency spikes of retinal ganglion cells

NASA Astrophysics Data System (ADS)

Choi, Myoung-Hwan; Ahn, Jungryul; Park, Dae Jin; Lee, Sang Min; Kim, Kwangsoo; Cho, Dong-il Dan; Senok, Solomon S.; Koo, Kyo-in; Goo, Yong Sook

2017-02-01

Objective. Direct stimulation of retinal ganglion cells in degenerate retinas by implanting epi-retinal prostheses is a recognized strategy for restoration of visual perception in patients with retinitis pigmentosa or age-related macular degeneration. Elucidating the best stimulus-response paradigms in the laboratory using multielectrode arrays (MEA) is complicated by the fact that the short-latency spikes (within 10 ms) elicited by direct retinal ganglion cell (RGC) stimulation are obscured by the stimulus artifact which is generated by the electrical stimulator. Approach. We developed an artifact subtraction algorithm based on topographic prominence discrimination, wherein the duration of prominences within the stimulus artifact is used as a strategy for identifying the artifact for subtraction and clarifying the obfuscated spikes which are then quantified using standard thresholding. Main results. We found that the prominence discrimination based filters perform creditably in simulation conditions by successfully isolating randomly inserted spikes in the presence of simple and even complex residual artifacts. We also show that the algorithm successfully isolated short-latency spikes in an MEA-based recording from degenerate mouse retinas, where the amplitude and frequency characteristics of the stimulus artifact vary according to the distance of the recording electrode from the stimulating electrode. By ROC analysis of false positive and false negative first spike detection rates in a dataset of one hundred and eight RGCs from four retinal patches, we found that the performance of our algorithm is comparable to that of a generally-used artifact subtraction filter algorithm which uses a strategy of local polynomial approximation (SALPA). Significance. We conclude that the application of topographic prominence discrimination is a valid and useful method for subtraction of stimulation artifacts with variable amplitudes and shapes. We propose that our algorithm may be used as stand-alone or supplementary to other artifact subtraction algorithms like SALPA.

The Role of Inhibition in a Computational Model of an Auditory Cortical Neuron during the Encoding of Temporal Information

PubMed Central

Bendor, Daniel

2015-01-01

In auditory cortex, temporal information within a sound is represented by two complementary neural codes: a temporal representation based on stimulus-locked firing and a rate representation, where discharge rate co-varies with the timing between acoustic events but lacks a stimulus-synchronized response. Using a computational neuronal model, we find that stimulus-locked responses are generated when sound-evoked excitation is combined with strong, delayed inhibition. In contrast to this, a non-synchronized rate representation is generated when the net excitation evoked by the sound is weak, which occurs when excitation is coincident and balanced with inhibition. Using single-unit recordings from awake marmosets (Callithrix jacchus), we validate several model predictions, including differences in the temporal fidelity, discharge rates and temporal dynamics of stimulus-evoked responses between neurons with rate and temporal representations. Together these data suggest that feedforward inhibition provides a parsimonious explanation of the neural coding dichotomy observed in auditory cortex. PMID:25879843

Extinction and anti-extinction: the "attentional waiting" hypothesis.

PubMed

Watling, Rosamond; Danckert, James; Linnell, Karina J; Cocchini, Gianna

2013-03-01

Patients with visual extinction have difficulty detecting a single contralesional stimulus when a second stimulus is simultaneously presented on the ipsilesional side. The rarely reported phenomenon of visual anti-extinction describes the opposite behavior, in which patients show greater difficulty in reporting a stimulus presented in isolation than they do in reporting 2 simultaneously presented stimuli. S. J. Goodrich and R. Ward (1997, Anti-extinction following unilateral parietal damage, Cognitive Neuropsychology, Vol. 14, pp. 595-612) suggested that visual anti-extinction is the result of a task-specific mechanism in which processing of the ipsilesional stimulus facilitates responses to the contralesional stimulus; in contrast, G. W. Humphreys, M. J. Riddoch, G. Nys, and D. Heinke (2002, Transient binding by time: Neuropsychological evidence from anti-extinction, Cognitive Neuropsychology, Vol. 19, pp. 361-380) suggested that temporal binding groups contralesional and ipsilesional stimuli together at brief exposure durations. We investigated extinction and anti-extinction phenomena in 3 brain-damaged patients using an extinction paradigm in which the stimulus exposure duration was systematically manipulated. Two patients showed both extinction and anti-extinction depending on the exposure duration of stimuli. Data confirmed the crucial role of duration in modulating the effect of extinction and anti-extinction. However, contrary to Humphreys and colleagues' (2002) single case, our patients showed extinction for short and anti-extinction for long exposure durations, suggesting that different mechanisms might underlie our patients' pattern of data. We discuss a novel "attentional waiting" hypothesis, which proposes that anti-extinction may be observed in patients showing extinction if the exposure duration of stimuli is increased. PsycINFO Database Record (c) 2013 APA, all rights reserved.

Blur-resistant Perimetric Stimuli

PubMed Central

Horner, Douglas G.; Dul, Mitchell W.; Swanson, William H.; Liu, Tiffany; Tran, Irene

2013-01-01

Purpose To develop perimetric stimuli which are resistant to the effects of peripheral defocus. Methods One eye each was tested on subjects free of eye disease. Experiment 1 assessed spatial frequency, testing 12 subjects at eccentricities from 2° to 7°, using blur levels from 0 D to 3 D for two (Gabor) stimuli (spatial standard deviation (SD) = 0.5°, spatial frequencies of 0.5 and 1.0 cpd). Experiment 2 assessed stimulus size, testing 12 subjects at eccentricities from 4° to 7°, using blur levels 0 D to 6 D, for two Gaussians with SDs of 0.5° and 0.25° and a 0.5 cpd Gabor with SD of 0.5°. Experiment 3 tested 13 subjects at eccentricities from fixation to 27°, using blur levels 0 D to 6 D, for Gabor stimuli at 56 locations; the spatial frequency ranged from 0.14 to 0.50 cpd with location, and SD was scaled accordingly. Results In experiment 1, blur by 3 D caused a small decline in log contrast sensitivity (CS) for the 0.5 cpd stimulus (mean ± SE = −0.09 ± 0.08 log unit) and a larger (t = 7.7, p <0.0001) decline for the 1.0 cpd stimulus (0.37 ± 0.13 log unit). In experiment 2, blur by 6 D caused minimal decline for the larger Gaussian, by −0.17 ± 0.16 log unit, and larger (t >4.5, p < 0.001) declines for the smaller Gaussian (−0.33 ± 0.16 log unit) and the Gabor (−0.36 ± 0.18 log unit). In experiment 3, blur by 6 D caused declines by 0.27 ± 0.05 log unit for eccentricities from 0° to 10°, by 0.20 ± 0.04 log unit for eccentricities from 10° to 20° and 0.13 ± 0.03 log unit for eccentricities from 20°–27°. Conclusions Experiments 1 & 2 allowed us to design stimuli for Experiment 3 that were resistant to effects of peripheral defocus. PMID:23584488

The interaction between specific and general information in category learning and representation: unitization and parallel interactive processing.

PubMed

Nahinsky, Irwin D; Harbison, J Isaiah

2011-01-01

We investigated the effects of specific stimulus information on the use of rule information in a category learning task in 2 experiments, one presented here and an intercategory transfer task reported in an earlier article. In the present experiment photograph--name combinations, called identifiers, were associated with 4 demographic attributes. The same attribute information was shown to all participants. However, for one group of participants, half of the identifiers were paired with attribute values repeated over presentation blocks. For the other group the identifier information was new for each presentation block. The first group performed less well than the second group on stimuli with nonrepeated identifiers, indicating a negative effect of specific stimulus information on processing rule information. Application of a network model to the 2 experiments, which provided for the growth of connections between attribute values in learning, indicated that repetition of identifiers produced a unitizing effect on stimuli. Results suggested that unitization produced interference through connections between irrelevant attribute values.

Human single-neuron responses at the threshold of conscious recognition

PubMed Central

Quiroga, R. Quian; Mukamel, R.; Isham, E. A.; Malach, R.; Fried, I.

2008-01-01

We studied the responses of single neurons in the human medial temporal lobe while subjects viewed familiar faces, animals, and landmarks. By progressively shortening the duration of stimulus presentation, coupled with backward masking, we show two striking properties of these neurons. (i) Their responses are not statistically different for the 33-ms, 66-ms, and 132-ms stimulus durations, and only for the 264-ms presentations there is a significantly higher firing. (ii) These responses follow conscious perception, as indicated by the subjects' recognition report. Remarkably, when recognized, a single snapshot as brief as 33 ms was sufficient to trigger strong single-unit responses far outlasting stimulus presentation. These results suggest that neurons in the medial temporal lobe can reflect conscious recognition by “all-or-none” responses. PMID:18299568

Attention Influences Single Unit and Local Field Potential Response Latencies in Visual Cortical Area V4

PubMed Central

Sundberg, Kristy A.; Mitchell, Jude F.; Gawne, Timothy J.

2012-01-01

Many previous studies have demonstrated that changes in selective attention can alter the response magnitude of visual cortical neurons, but there has been little evidence for attention affecting response latency. Small latency differences, though hard to detect, can potentially be of functional importance, and may also give insight into the mechanisms of neuronal computation. We therefore reexamined the effect of attention on the response latency of both single units and the local field potential (LFP) in primate visual cortical area V4. We find that attention does produce small (1–2 ms) but significant reductions in the latency of both the spiking and LFP responses. Though attention, like contrast elevation, reduces response latencies, we find that the two have different effects on the magnitude of the LFP. Contrast elevations increase and attention decreases the magnitude of the initial deflection of the stimulus-evoked LFP. Both contrast elevation and attention increase the magnitude of the spiking response. We speculate that latencies may be reduced at higher contrast because stronger stimulus inputs drive neurons more rapidly to spiking threshold, while attention may reduce latencies by placing neurons in a more depolarized state closer to threshold before stimulus onset. PMID:23136440

Feasibility and performance evaluation of generating and recording visual evoked potentials using ambulatory Bluetooth based system.

PubMed

Ellingson, Roger M; Oken, Barry

2010-01-01

Report contains the design overview and key performance measurements demonstrating the feasibility of generating and recording ambulatory visual stimulus evoked potentials using the previously reported custom Complementary and Alternative Medicine physiologic data collection and monitoring system, CAMAS. The methods used to generate visual stimuli on a PDA device and the design of an optical coupling device to convert the display to an electrical waveform which is recorded by the CAMAS base unit are presented. The optical sensor signal, synchronized to the visual stimulus emulates the brain's synchronized EEG signal input to CAMAS normally reviewed for the evoked potential response. Most importantly, the PDA also sends a marker message over the wireless Bluetooth connection to the CAMAS base unit synchronized to the visual stimulus which is the critical averaging reference component to obtain VEP results. Results show the variance in the latency of the wireless marker messaging link is consistent enough to support the generation and recording of visual evoked potentials. The averaged sensor waveforms at multiple CPU speeds are presented and demonstrate suitability of the Bluetooth interface for portable ambulatory visual evoked potential implementation on our CAMAS platform.

Visual feature extraction from voxel-weighted averaging of stimulus images in 2 fMRI studies.

PubMed

Hart, Corey B; Rose, William J

2013-11-01

Multiple studies have provided evidence for distributed object representation in the brain, with several recent experiments leveraging basis function estimates for partial image reconstruction from fMRI data. Using a novel combination of statistical decomposition, generalized linear models, and stimulus averaging on previously examined image sets and Bayesian regression of recorded fMRI activity during presentation of these data sets, we identify a subset of relevant voxels that appear to code for covarying object features. Using a technique we term "voxel-weighted averaging," we isolate image filters that these voxels appear to implement. The results, though very cursory, appear to have significant implications for hierarchical and deep-learning-type approaches toward the understanding of neural coding and representation.

A Weight-Loss Program Using Self-Control Techniques in a Correctional Facility: An Experimental Case Study

ERIC Educational Resources Information Center

Goldenberg, Edward E.; DeNinno, John

1977-01-01

Self-control techniques were taught to an obese 27-year-old black male to help modify overeating behavior. Self-reinforcement was utilized in addition to systematic isolation of chained eating behavior from associated stimulus situations. A physical exercise program was employed in conjunction with the self-control techniques. (Author)

Psychophysical Isolation of the Modality Responsible for Detecting Multimodal Stimuli: A Chemosensory Example

ERIC Educational Resources Information Center

Nagata, Hisanori; Dalton, Pamela; Doolittle, Nadine; Breslin, Paul A. S.

2005-01-01

Multiple sense modalities can be stimulated conjointly by a physically complex item, such as a predator, and also by a physically solitary stimulus that acts on multiple receptor classes. As a prime example of this latter group, l-menthol from mint stimulates taste, smell, and several somatosensory submodalities. In 6 experiments that used a…

The Fire-Alarm Game: Exit Training Using Negative and Positive Reinforcement under Varied Stimulus Conditions. Short Reports.

ERIC Educational Resources Information Center

Holburn, C. Steven; Dougher, Michael J.

1985-01-01

Techniques for training a severely retarded blind client to exit his living unit during a fire drill used a combination of negative and positive reinforcement. Following a shaping procedure, the client learned to leave his living unit from any internal point through generalization training and subsequent test probes. (Author/CL)

Contributions to muscle force and EMG by combined neural excitation and electrical stimulation

NASA Astrophysics Data System (ADS)

Crago, Patrick E.; Makowski, Nathaniel S.; Cole, Natalie M.

2014-10-01

Objective. Stimulation of muscle for research or clinical interventions is often superimposed on ongoing physiological activity without a quantitative understanding of the impact of the stimulation on the net muscle activity and the physiological response. Experimental studies show that total force during stimulation is less than the sum of the isolated voluntary and stimulated forces, but the occlusion mechanism is not understood. Approach. We develop a model of efferent motor activity elicited by superimposing stimulation during a physiologically activated contraction. The model combines action potential interactions due to collision block, source resetting, and refractory periods with previously published models of physiological motor unit recruitment, rate modulation, force production, and EMG generation in human first dorsal interosseous muscle to investigate the mechanisms and effectiveness of stimulation on the net muscle force and EMG. Main results. Stimulation during a physiological contraction demonstrates partial occlusion of force and the neural component of the EMG, due to action potential interactions in motor units activated by both sources. Depending on neural and stimulation firing rates as well as on force-frequency properties, individual motor unit forces can be greater, smaller, or unchanged by the stimulation. In contrast, voluntary motor unit EMG potentials in simultaneously stimulated motor units show progressive occlusion with increasing stimulus rate. The simulations predict that occlusion would be decreased by a reverse stimulation recruitment order. Significance. The results are consistent with and provide a mechanistic interpretation of previously published experimental evidence of force occlusion. The models also predict two effects that have not been reported previously—voluntary EMG occlusion and the advantages of a proximal stimulation site. This study provides a basis for the rational design of both future experiments and clinical neuroprosthetic interventions involving either motor or sensory stimulation.

Contributions to muscle force and EMG by combined neural excitation and electrical stimulation

PubMed Central

Crago, Patrick E; Makowski, Nathaniel S; Cole, Natalie M

2014-01-01

Objective Stimulation of muscle for research or clinical interventions is often superimposed on ongoing physiological activity, without a quantitative understanding of the impact of the stimulation on the net muscle activity and the physiological response. Experimental studies show that total force during stimulation is less than the sum of the isolated voluntary and stimulated forces, but the occlusion mechanism is not understood. Approach We develop a model of efferent motor activity elicited by superimposing stimulation during a physiologically activated contraction. The model combines action potential interactions due to collision block, source resetting, and refractory periods with previously published models of physiological motor unit recruitment, rate modulation, force production, and EMG generation in human first dorsal interosseous muscle to investigate the mechanisms and effectiveness of stimulation on the net muscle force and EMG. Main Results Stimulation during a physiological contraction demonstrates partial occlusion of force and the neural component of the EMG, due to action potential interactions in motor units activated by both sources. Depending on neural and stimulation firing rates as well as on force-frequency properties, individual motor unit forces can be greater, smaller, or unchanged by the stimulation. In contrast, voluntary motor unit EMG potentials in simultaneously stimulated motor units show progressive occlusion with increasing stimulus rate. The simulations predict that occlusion would be decreased by a reverse stimulation recruitment order. Significance The results are consistent with and provide a mechanistic interpretation of previously published experimental evidence of force occlusion. The models also predict two effects that have not been reported previously - voluntary EMG occlusion and the advantages of a proximal stimulation site. This study provides a basis for the rational design of both future experiments and clinical neuroprosthetic interventions involving either motor or sensory stimulation. PMID:25242203

Fidelity of the ensemble code for visual motion in primate retina.

PubMed

Frechette, E S; Sher, A; Grivich, M I; Petrusca, D; Litke, A M; Chichilnisky, E J

2005-07-01

Sensory experience typically depends on the ensemble activity of hundreds or thousands of neurons, but little is known about how populations of neurons faithfully encode behaviorally important sensory information. We examined how precisely speed of movement is encoded in the population activity of magnocellular-projecting parasol retinal ganglion cells (RGCs) in macaque monkey retina. Multi-electrode recordings were used to measure the activity of approximately 100 parasol RGCs simultaneously in isolated retinas stimulated with moving bars. To examine how faithfully the retina signals motion, stimulus speed was estimated directly from recorded RGC responses using an optimized algorithm that resembles models of motion sensing in the brain. RGC population activity encoded speed with a precision of approximately 1%. The elementary motion signal was conveyed in approximately 10 ms, comparable to the interspike interval. Temporal structure in spike trains provided more precise speed estimates than time-varying firing rates. Correlated activity between RGCs had little effect on speed estimates. The spatial dispersion of RGC receptive fields along the axis of motion influenced speed estimates more strongly than along the orthogonal direction, as predicted by a simple model based on RGC response time variability and optimal pooling. on and off cells encoded speed with similar and statistically independent variability. Simulation of downstream speed estimation using populations of speed-tuned units showed that peak (winner take all) readout provided more precise speed estimates than centroid (vector average) readout. These findings reveal how faithfully the retinal population code conveys information about stimulus speed and the consequences for motion sensing in the brain.

Interaction of corneal nociceptive stimulation and lacrimal secretion.

PubMed

Situ, Ping; Simpson, Trefford L

2010-11-01

To investigate the interaction between corneal stimuli at different positions and tear secretion and to establish relationships between nociceptive stimuli detection thresholds and stimulated tearing. Using a computerized Belmonte-esthesiometer, mechanical and chemical stimuli, from 0% to 200% of the threshold in 50% steps, were delivered (in random order) to the central and peripheral (approximately 2-mm inside the limbus) cornea during four separate sessions to 15 subjects. Immediately after each stimulus, tear meniscus height (TMH) was measured using optical coherence tomography to quantify the amount of lacrimal secretion, and subjects reported whether they felt tears starting to accumulate in their eyes. Thresholds (50% detection) for detection of tearing were estimated. TMH increased with increasing stimulus intensity (P < 0.05), and the overall increase was higher with central stimulation than with peripheral stimulation (P < 0.05). The changes in TMH with threshold-scaled stimulus intensity depended on test location (P < 0.05) and stimulus modality (P < 0.05). The maximum intensity of mechanical stimulation of the central cornea induced the greatest TMH (all P < 0.05). For chemical stimulation, the stimulus intensity required to induce detectable tearing was higher than that required to detect a stimulus and higher in the periphery than at the center (all P < 0.05). Noxious mechanical and chemical stimuli evoked measurable tear secretion, with central corneal mechanical stimulation evoking the strongest lacrimation reflex. Central mechanical corneal stimulation is the most effective stimulus-position pairing and appears to be the major sensory driving force for reflex tear secretion by the lacrimal functional unit.

A COMPARISON OF METHODS FOR TEACHING RECEPTIVE LABELING TO CHILDREN WITH AUTISM SPECTRUM DISORDERS

PubMed Central

Grow, Laura L; Carr, James E; Kodak, Tiffany M; Jostad, Candice M; Kisamore, April N

2011-01-01

Many early intervention curricular manuals recommend teaching auditory-visual conditional discriminations (i.e., receptive labeling) using the simple-conditional method in which component simple discriminations are taught in isolation and in the presence of a distracter stimulus before the learner is required to respond conditionally. Some have argued that this procedure might be susceptible to faulty stimulus control such as stimulus overselectivity (Green, 2001). Consequently, there has been a call for the use of alternative teaching procedures such as the conditional-only method, which involves conditional discrimination training from the onset of intervention. The purpose of the present study was to compare the simple-conditional and conditional-only methods for teaching receptive labeling to 3 young children diagnosed with autism spectrum disorders. The data indicated that the conditional-only method was a more reliable and efficient teaching procedure. In addition, several error patterns emerged during training using the simple-conditional method. The implications of the results with respect to current teaching practices in early intervention programs are discussed. PMID:21941380

Selective attention to visual compound stimuli in squirrel monkeys (Saimiri sciureus).

PubMed

Ploog, Bertram O

2011-05-01

Five squirrel monkeys served under a simultaneous discrimination paradigm with visual compound stimuli that allowed measurement of excitatory and inhibitory control exerted by individual stimulus components (form and luminance/"color"), which could not be presented in isolation (i.e., form could not be presented without color). After performance exceeded a criterion of 75% correct during training, unreinforced test trials with stimuli comprising recombined training stimulus components were interspersed while the overall reinforcement rate remained constant for training and testing. The training-testing series was then repeated with reversed reinforcement contingencies. The findings were that color acquired greater excitatory control than form under the original condition, that no such difference was found for the reversal condition or for inhibitory control under either condition, and that overall inhibitory control was less pronounced than excitatory control. The remarkably accurate performance throughout suggested that a forced 4-s delay between the stimulus presentation and the opportunity to respond was effective in reducing "impulsive" responding, which has implications for suppressing impulsive responding in children with autism and with attention deficit disorder. Copyright © 2011 Elsevier B.V. All rights reserved.

Visual statistical learning is not reliably modulated by selective attention to isolated events

PubMed Central

Musz, Elizabeth; Weber, Matthew J.; Thompson-Schill, Sharon L.

2014-01-01

Recent studies of visual statistical learning (VSL) indicate that the visual system can automatically extract temporal and spatial relationships between objects. We report several attempts to replicate and extend earlier work (Turk-Browne et al., 2005) in which observers performed a cover task on one of two interleaved stimulus sets, resulting in learning of temporal relationships that occur in the attended stream, but not those present in the unattended stream. Across four experiments, we exposed observers to a similar or identical familiarization protocol, directing attention to one of two interleaved stimulus sets; afterward, we assessed VSL efficacy for both sets using either implicit response-time measures or explicit familiarity judgments. In line with prior work, we observe learning for the attended stimulus set. However, unlike previous reports, we also observe learning for the unattended stimulus set. When instructed to selectively attend to only one of the stimulus sets and ignore the other set, observers could extract temporal regularities for both sets. Our efforts to experimentally decrease this effect by changing the cover task (Experiment 1) or the complexity of the statistical regularities (Experiment 3) were unsuccessful. A fourth experiment using a different assessment of learning likewise failed to show an attentional effect. Simulations drawing random samples our first three experiments (n=64) confirm that the distribution of attentional effects in our sample closely approximates the null. We offer several potential explanations for our failure to replicate earlier findings, and discuss how our results suggest limiting conditions on the relevance of attention to VSL. PMID:25172196

Do former preterm infants remember and respond to neonatal intensive care unit noise?

PubMed

Barreto, Edwin D; Morris, Brenda H; Philbin, M Kathleen; Gray, Lincoln C; Lasky, Robert E

2006-11-01

Previous studies have shown that 4-month-old infants have a decrease in heart rate, a component of the orienting reflex, in response to interesting auditory stimuli and an increase in heart rate to aversive auditory stimuli. To compare the heart rate responses of former preterm and term infants at 4-5 months corrected age to a recording of NICU noises. 13 former preterm infants and 17 full-term infants were presented NICU noise and another noise of similar level and frequency content in random order. Heart rate 10s prior to the stimulus and for 20s during the stimulus was analyzed. Group differences in second by second heart rate changes in response to the two noise stimuli were compared by analysis of covariance. Both the preterm and term newborns responded similarly to the NICU noise and the control noise. The preterm infants did not alter their heart rate in response to either stimulus. In contrast, the term infants displayed an orienting response to the second stimulus presented regardless of whether it was the NICU or control noise. Former preterm infants at 4-5 months corrected age have reduced responsiveness to auditory stimulation in comparison to 4- to 5-month-old term infants. Furthermore, they did not respond to the NICU noise as an aversive stimulus.

Dynamic Alignment Models for Neural Coding

PubMed Central

Kollmorgen, Sepp; Hahnloser, Richard H. R.

2014-01-01

Recently, there have been remarkable advances in modeling the relationships between the sensory environment, neuronal responses, and behavior. However, most models cannot encompass variable stimulus-response relationships such as varying response latencies and state or context dependence of the neural code. Here, we consider response modeling as a dynamic alignment problem and model stimulus and response jointly by a mixed pair hidden Markov model (MPH). In MPHs, multiple stimulus-response relationships (e.g., receptive fields) are represented by different states or groups of states in a Markov chain. Each stimulus-response relationship features temporal flexibility, allowing modeling of variable response latencies, including noisy ones. We derive algorithms for learning of MPH parameters and for inference of spike response probabilities. We show that some linear-nonlinear Poisson cascade (LNP) models are a special case of MPHs. We demonstrate the efficiency and usefulness of MPHs in simulations of both jittered and switching spike responses to white noise and natural stimuli. Furthermore, we apply MPHs to extracellular single and multi-unit data recorded in cortical brain areas of singing birds to showcase a novel method for estimating response lag distributions. MPHs allow simultaneous estimation of receptive fields, latency statistics, and hidden state dynamics and so can help to uncover complex stimulus response relationships that are subject to variable timing and involve diverse neural codes. PMID:24625448

A method for real-time visual stimulus selection in the study of cortical object perception.

PubMed

Leeds, Daniel D; Tarr, Michael J

2016-06-01

The properties utilized by visual object perception in the mid- and high-level ventral visual pathway are poorly understood. To better establish and explore possible models of these properties, we adopt a data-driven approach in which we repeatedly interrogate neural units using functional Magnetic Resonance Imaging (fMRI) to establish each unit's image selectivity. This approach to imaging necessitates a search through a broad space of stimulus properties using a limited number of samples. To more quickly identify the complex visual features underlying human cortical object perception, we implemented a new functional magnetic resonance imaging protocol in which visual stimuli are selected in real-time based on BOLD responses to recently shown images. Two variations of this protocol were developed, one relying on natural object stimuli and a second based on synthetic object stimuli, both embedded in feature spaces based on the complex visual properties of the objects. During fMRI scanning, we continuously controlled stimulus selection in the context of a real-time search through these image spaces in order to maximize neural responses across pre-determined 1cm(3) rain regions. Elsewhere we have reported the patterns of cortical selectivity revealed by this approach (Leeds et al., 2014). In contrast, here our objective is to present more detailed methods and explore the technical and biological factors influencing the behavior of our real-time stimulus search. We observe that: 1) Searches converged more reliably when exploring a more precisely parameterized space of synthetic objects; 2) real-time estimation of cortical responses to stimuli is reasonably consistent; 3) search behavior was acceptably robust to delays in stimulus displays and subject motion effects. Overall, our results indicate that real-time fMRI methods may provide a valuable platform for continuing study of localized neural selectivity, both for visual object representation and beyond. Copyright © 2016 Elsevier Inc. All rights reserved.

The Use of Voice Cues for Speaker Gender Recognition in Cochlear Implant Recipients

ERIC Educational Resources Information Center

Meister, Hartmut; Fürsen, Katrin; Streicher, Barbara; Lang-Roth, Ruth; Walger, Martin

2016-01-01

Purpose: The focus of this study was to examine the influence of fundamental frequency (F0) and vocal tract length (VTL) modifications on speaker gender recognition in cochlear implant (CI) recipients for different stimulus types. Method: Single words and sentences were manipulated using isolated or combined F0 and VTL cues. Using an 11-point…

The Cost of Accumulating Evidence in Perceptual Decision Making

PubMed Central

Drugowitsch, Jan; Moreno-Bote, Rubén; Churchland, Anne K.; Shadlen, Michael N.; Pouget, Alexandre

2012-01-01

Decision making often involves the accumulation of information over time, but acquiring information typically comes at a cost. Little is known about the cost incurred by animals and humans for acquiring additional information from sensory variables, due, for instance, to attentional efforts. Through a novel integration of diffusion models and dynamic programming, we were able to estimate the cost of making additional observations per unit of time from two monkeys and six humans in a reaction time random dot motion discrimination task. Surprisingly, we find that, the cost is neither zero nor constant over time, but for the animals and humans features a brief period in which it is constant but increases thereafter. In addition, we show that our theory accurately matches the observed reaction time distributions for each stimulus condition, the time-dependent choice accuracy both conditional on stimulus strength and independent of it, and choice accuracy and mean reaction times as a function of stimulus strength. The theory also correctly predicts that urgency signals in the brain should be independent of the difficulty, or stimulus strength, at each trial. PMID:22423085

Rapid onset of hypoxic vasoconstriction in isolated lungs.

PubMed

Jensen, K S; Micco, A J; Czartolomna, J; Latham, L; Voelkel, N F

1992-05-01

A fast-response O2 analyzer that samples air at low flow rates allows the quasi-instantaneous measurement of O2 concentration change in the airways of isolated blood-perfused rat lungs. This instrument and an oximeter were used to measure the stimulus-response delay time of hypoxic pulmonary vasoconstriction when the lungs were challenged with 10, 5, or 3% O2. The estimate for the shortest delay time between accomplished fall in airway O2 concentration and the onset of hypoxia-induced vasoconstriction was approximately 7 s. We found that the slope of pressure rise, but not the stimulus-response delay time, correlated with the magnitude of hypoxic vasoconstriction. Oscillations in pulmonary arterial pressure were observed when the lungs were challenged with 10% O2 but not when the challenge was 12, 5, or 3%, indicating perhaps that these oscillations were a threshold phenomenon. Established hypoxic vasoconstriction was sensitive to brief changes in airway O2 concentration. Vasodilation occurred when the gas mixture was switched from 3 to 21% O2 for two to five breaths, and vasoconstriction occurred when the gas was changed during a single breath from 5 to 3% O2.

Mobbing vocalizations as a coping response in the common marmoset.

PubMed

Cross, N; Rogers, L J

2006-02-01

Using a non-invasive method of sampling saliva followed by assay for cortisol levels, we found that common marmosets (Callithrix jacchus) show a decrease in cortisol levels after seeing a snake-model stimulus that reliably elicits mobbing (tsik) calls. In fact, there was a significant positive correlation between the number of tsik vocalizations made and the magnitude of the decrease in the cortisol concentrations. Furthermore, marmosets with higher levels of cortisol prior to being exposed to the stimulus produce more tsik calls than those with lower levels of cortisol. Subsequent experiments showed that, in response to 15 min of isolation with no visual or auditory contact with conspecifics (a traditional stressor), cortisol levels increased significantly. However, playback of the mobbing calls of a familiar conspecific to individual isolated marmosets not only prevented the rise in cortisol, but also actually caused a decrease in the levels of this hormone. This suggests that the mobbing calls serve to calm the marmoset after experiencing a stressful situation. This finding results in a greater understanding as to the role of physiological responses during communication in this species and could have implications for the welfare of marmosets in captivity.

Lethal effect of electric fields on isolated ventricular myocytes.

PubMed

de Oliveira, Pedro Xavier; Bassani, Rosana Almada; Bassani, José Wilson Magalhães

2008-11-01

Defibrillator-type shocks may cause electric and contractile dysfunction. In this study, we determined the relationship between probability of lethal injury and electric field intensity (E in isolated rat ventricular myocytes, with emphasis on field orientation and stimulus waveform. This relationship was sigmoidal with irreversible injury for E > 50 V/cm . During both threshold and lethal stimulation, cells were twofold more sensitive to the field when it was applied longitudinally (versus transversally) to the cell major axis. For a given E, the estimated maximum variation of transmembrane potential (Delta V(max)) was greater for longitudinal stimuli, which might account for the greater sensitivity to the field. Cell death, however, occurred at lower maximum Delta V(max) values for transversal shocks. This might be explained by a less steep spatial decay of transmembrane potential predicted for transversal stimulation, which would possibly result in occurrence of electroporation in a larger membrane area. For the same stimulus duration, cells were less sensitive to field-induced injury when shocks were biphasic (versus monophasic). Ours results indicate that, although significant myocyte death may occur in the E range expected during clinical defibrillation, biphasic shocks are less likely to produce irreversible cell injury.

Visual attention mitigates information loss in small- and large-scale neural codes

PubMed Central

Sprague, Thomas C; Saproo, Sameer; Serences, John T

2015-01-01

Summary The visual system transforms complex inputs into robust and parsimonious neural codes that efficiently guide behavior. Because neural communication is stochastic, the amount of encoded visual information necessarily decreases with each synapse. This constraint requires processing sensory signals in a manner that protects information about relevant stimuli from degradation. Such selective processing – or selective attention – is implemented via several mechanisms, including neural gain and changes in tuning properties. However, examining each of these effects in isolation obscures their joint impact on the fidelity of stimulus feature representations by large-scale population codes. Instead, large-scale activity patterns can be used to reconstruct representations of relevant and irrelevant stimuli, providing a holistic understanding about how neuron-level modulations collectively impact stimulus encoding. PMID:25769502

Mycobacterium chimaera in Heater-Cooler Units in Denmark Related to Isolates from the United States and United Kingdom.

PubMed

Svensson, Erik; Jensen, Elsebeth Tvenstrup; Rasmussen, Erik Michael; Folkvardsen, Dorte Bek; Norman, Anders; Lillebaek, Troels

2017-03-01

Mycobacterium chimaera was present at high rates (>80%) in heater-cooler units (HCUs) from all 5 thoracic surgery departments in Denmark. Isolates were clonal to HCU-associated isolates from the United States (including some from patients) and United Kingdom. However, M. chimaera from 2 brands of HCU were genetically distinct.

Stimulus information stored in lasting active and hidden network states is destroyed by network bursts

PubMed Central

Dranias, Mark R.; Westover, M. Brandon; Cash, Sidney; VanDongen, Antonius M. J.

2015-01-01

In both humans and animals brief synchronizing bursts of epileptiform activity known as interictal epileptiform discharges (IEDs) can, even in the absence of overt seizures, cause transient cognitive impairments (TCI) that include problems with perception or short-term memory. While no evidence from single units is available, it has been assumed that IEDs destroy information represented in neuronal networks. Cultured neuronal networks are a model for generic cortical microcircuits, and their spontaneous activity is characterized by the presence of synchronized network bursts (SNBs), which share a number of properties with IEDs, including the high degree of synchronization and their spontaneous occurrence in the absence of an external stimulus. As a model approach to understanding the processes underlying IEDs, optogenetic stimulation and multielectrode array (MEA) recordings of cultured neuronal networks were used to study whether stimulus information represented in these networks survives SNBs. When such networks are optically stimulated they encode and maintain stimulus information for as long as one second. Experiments involved recording the network response to a single stimulus and trials where two different stimuli were presented sequentially, akin to a paired pulse trial. We broke the sequential stimulus trials into encoding, delay and readout phases and found that regardless of which phase the SNB occurs, stimulus-specific information was impaired. SNBs were observed to increase the mean network firing rate, but this did not translate monotonically into increases in network entropy. It was found that the more excitable a network, the more stereotyped its response was during a network burst. These measurements speak to whether SNBs are capable of transmitting information in addition to blocking it. These results are consistent with previous reports and provide baseline predictions concerning the neural mechanisms by which IEDs might cause TCI. PMID:25755638

[Clinical and magnetic resonance imaging characteristics of isolated congenital anosmia].

PubMed

Liu, Jian-feng; Wang, Jian; You, Hui; Ni, Dao-feng; Yang, Da-zhang

2010-05-25

To report a series of patients with isolated congenital anosmia and summarize their clinical and magnetic resonance imaging (MRI) characteristics. Twenty patients with isolated congenital anosmia were reviewed retrospectively. A thorough medical and chemosensory history, physical examination, nasal endoscopy, T&T olfactory testing, olfactory event-related potentials, sinonasal computed tomography scan and magnetic resonance image of olfactory pathway were performed in all patients. Neither ENT physical examination nor nasal endoscopy was remarkable. Subjective olfactory testing indicated all of them were of anosmia. No olfactory event-related potentials to maximal stimulus were obtained. Computed tomography scan was normal. MRI revealed the absence of olfactory bulbs and tracts in all cases. And hypoplasia or aplasia of olfactory sulcus was found in all cases. All the patients had normal sex hormone level. The diagnosis of isolated congenital anosmia is established on chief complaints, physical examination, olfactory testing and olfactory imaging. MRI of olfactory pathway is indispensable.

Auditory temporal-order processing of vowel sequences by young and elderly listeners1

PubMed Central

Fogerty, Daniel; Humes, Larry E.; Kewley-Port, Diane

2010-01-01

This project focused on the individual differences underlying observed variability in temporal processing among older listeners. Four measures of vowel temporal-order identification were completed by young (N=35; 18–31 years) and older (N=151; 60–88 years) listeners. Experiments used forced-choice, constant-stimuli methods to determine the smallest stimulus onset asynchrony (SOA) between brief (40 or 70 ms) vowels that enabled identification of a stimulus sequence. Four words (pit, pet, pot, and put) spoken by a male talker were processed to serve as vowel stimuli. All listeners identified the vowels in isolation with better than 90% accuracy. Vowel temporal-order tasks included the following: (1) monaural two-item identification, (2) monaural four-item identification, (3) dichotic two-item vowel identification, and (4) dichotic two-item ear identification. Results indicated that older listeners had more variability and performed poorer than young listeners on vowel-identification tasks, although a large overlap in distributions was observed. Both age groups performed similarly on the dichotic ear-identification task. For both groups, the monaural four-item and dichotic two-item tasks were significantly harder than the monaural two-item task. Older listeners’ SOA thresholds improved with additional stimulus exposure and shorter dichotic stimulus durations. Individual differences of temporal-order performance among the older listeners demonstrated the influence of cognitive measures, but not audibility or age. PMID:20370033

Auditory temporal-order processing of vowel sequences by young and elderly listeners.

PubMed

Fogerty, Daniel; Humes, Larry E; Kewley-Port, Diane

2010-04-01

This project focused on the individual differences underlying observed variability in temporal processing among older listeners. Four measures of vowel temporal-order identification were completed by young (N=35; 18-31 years) and older (N=151; 60-88 years) listeners. Experiments used forced-choice, constant-stimuli methods to determine the smallest stimulus onset asynchrony (SOA) between brief (40 or 70 ms) vowels that enabled identification of a stimulus sequence. Four words (pit, pet, pot, and put) spoken by a male talker were processed to serve as vowel stimuli. All listeners identified the vowels in isolation with better than 90% accuracy. Vowel temporal-order tasks included the following: (1) monaural two-item identification, (2) monaural four-item identification, (3) dichotic two-item vowel identification, and (4) dichotic two-item ear identification. Results indicated that older listeners had more variability and performed poorer than young listeners on vowel-identification tasks, although a large overlap in distributions was observed. Both age groups performed similarly on the dichotic ear-identification task. For both groups, the monaural four-item and dichotic two-item tasks were significantly harder than the monaural two-item task. Older listeners' SOA thresholds improved with additional stimulus exposure and shorter dichotic stimulus durations. Individual differences of temporal-order performance among the older listeners demonstrated the influence of cognitive measures, but not audibility or age.

Quantitative Simulations of MST Visual Receptive Field Properties Using a Template Model of Heading Estimation

NASA Technical Reports Server (NTRS)

Stone, Leland S.; Perrone, J. A.

1997-01-01

We previously developed a template model of primate visual self-motion processing that proposes a specific set of projections from MT-like local motion sensors onto output units to estimate heading and relative depth from optic flow. At the time, we showed that that the model output units have emergent properties similar to those of MSTd neurons, although there was little physiological evidence to test the model more directly. We have now systematically examined the properties of the model using stimulus paradigms used by others in recent single-unit studies of MST: 1) 2-D bell-shaped heading tuning. Most MSTd neurons and model output units show bell-shaped heading tuning. Furthermore, we found that most model output units and the finely-sampled example neuron in the Duffy-Wurtz study are well fit by a 2D gaussian (sigma approx. 35deg, r approx. 0.9). The bandwidth of model and real units can explain why Lappe et al. found apparent sigmoidal tuning using a restricted range of stimuli (+/-40deg). 2) Spiral Tuning and Invariance. Graziano et al. found that many MST neurons appear tuned to a specific combination of rotation and expansion (spiral flow) and that this tuning changes little for approx. 10deg shifts in stimulus placement. Simulations of model output units under the same conditions quantitatively replicate this result. We conclude that a template architecture may underlie MT inputs to MST.

Temporal integration in nasal lateralization of homologous propionates.

PubMed

Wise, Paul M; Toczydlowski, Sean E; Zhao, Kai; Wysocki, Charles J

2009-08-01

For nasal irritation from volatile chemicals, a version of Haber's rule (k = C(n)T) can model the trade-off between concentration (C) and duration of exposure (T) to achieve a fixed sensory impact, e.g. threshold-level irritation or a fixed suprathreshold intensity. The term k is a constant. The exponent, n, represents how well the system integrates over time. An exponent of 1 indicates complete temporal integration: an x-fold increase in stimulus duration exactly compensates for cutting the concentration 1/x. An exponent greater than 1 indicates incomplete temporal integration: more than an x-fold increase in duration is needed. In a previous study of homologous alcohols, n varied systematically with number of methylene units: integration became more complete as the length of the carbon chain increased. To explore the generality of this finding, we tested homologous esters that differ in the number of methylene units: n-ethyl propionate, n-propyl propionate, and n-butyl propionate. Nasal lateralization was used to measure irritation thresholds. Human subjects received a fixed concentration of a single compound within each experimental session. Stimulus duration was varied to find the briefest stimulus that caused lateralizable irritation. Concentration and compound varied across sessions. Consistent with results with n-alcohols, integration became more complete as the number of methylene units increased. Lipid solubility varies with chain length; hence, solubility in the nasal mucosa may play a role in the dynamics of irritation. Further, preliminary analyses suggest that, for data pooled across both chemical series, n varies systematically with molecular parameters related to solubility and diffusion.

Effects of an ethanol-paired CS on responding for ethanol and food: Comparisons with a stimulus in a Truly-Random-Control group and to a food-paired CS on responding for food.

PubMed

Lamb, R J; Ginsburg, Brett C; Schindler, Charles W

2016-12-01

Motivational increases due to exposure to alcohol-paired Conditioned Stimuli (CS) are central to some accounts of alcoholism. However, few studies isolate a stimulus's function as a CS from its other potential functions. Pavlovian-Instrumental-Transfer (PIT) procedures isolate a stimulus's function as a CS from its other functions. Though there are several relevant studies using PIT, knowledge gaps exist. Particularly, it is not clear that an alcohol-paired CS will increase alcohol seeking compared to the same stimulus in a Truly-Random-Control group, nor whether such increases are specific to alcohol seeking. To address these knowledge gaps in Experiment 1, rats responded for ethanol (0.1 ml 8% w/v) under an RI 30-sec schedule, then the lever was removed and half the rats had ethanol delivered during occasional 120-sec light presentations, while the remainder had ethanol and the light presented under independent RT schedules. Later the lever was returned and the light was presented during responding in extinction (PIT test). Following this test, levers were again removed and the light was presented without ethanol (light extinction), following again by a PIT test. Responding in the two groups during light presentations did not differ in either PIT test. Experiment 2 repeated Experiment 1 using food instead of ethanol. In Experiment 2, responding during light presentations increased in the paired group. In Experiment 3, rats were trained on a concurrent FR schedule of food and ethanol delivery. Ethanol was delivered following 5 responses and the response requirement for food adjusted so that similar numbers of food and ethanol deliveries were obtained. Subsequently, rats underwent conditioning, control and testing procedures identical to those in Experiment 1. In Experiment 3, the ethanol-paired CS increased ethanol-responding, but not food-responding. These results are most easily interpreted as changes in responding resulting from CS-elicited behavior rather than motivational changes. This interpretation is more compatible with some descriptions of the role of an alcohol-paired CS in alcoholism than others. Copyright © 2016 Elsevier Inc. All rights reserved.

Generalization of value in reinforcement learning by humans

PubMed Central

Wimmer, G. Elliott; Daw, Nathaniel D.; Shohamy, Daphna

2012-01-01

Research in decision making has focused on the role of dopamine and its striatal targets in guiding choices via learned stimulus-reward or stimulus-response associations, behavior that is well-described by reinforcement learning (RL) theories. However, basic RL is relatively limited in scope and does not explain how learning about stimulus regularities or relations may guide decision making. A candidate mechanism for this type of learning comes from the domain of memory, which has highlighted a role for the hippocampus in learning of stimulus-stimulus relations, typically dissociated from the role of the striatum in stimulus-response learning. Here, we used fMRI and computational model-based analyses to examine the joint contributions of these mechanisms to RL. Humans performed an RL task with added relational structure, modeled after tasks used to isolate hippocampal contributions to memory. On each trial participants chose one of four options, but the reward probabilities for pairs of options were correlated across trials. This (uninstructed) relationship between pairs of options potentially enabled an observer to learn about options’ values based on experience with the other options and to generalize across them. We observed BOLD activity related to learning in the striatum and also in the hippocampus. By comparing a basic RL model to one augmented to allow feedback to generalize between correlated options, we tested whether choice behavior and BOLD activity were influenced by the opportunity to generalize across correlated options. Although such generalization goes beyond standard computational accounts of RL and striatal BOLD, both choices and striatal BOLD were better explained by the augmented model. Consistent with the hypothesized role for the hippocampus in this generalization, functional connectivity between the ventral striatum and hippocampus was modulated, across participants, by the ability of the augmented model to capture participants’ choice. Our results thus point toward an interactive model in which striatal RL systems may employ relational representations typically associated with the hippocampus. PMID:22487039

Effects of locus coeruleus stimulation on the responses of SI neurons of the rat to controlled natural and electrical stimulation of the skin.

PubMed

Snow, P J; Andre, P; Pompeiano, O

1999-02-01

1. The effects of microstimulation of the locus coeruleus (LC) region on the spontaneous discharge and the response of SI neurons to natural and electrical stimulation of the skin have been investigated in 26 urethane anesthetized Sprague-Dawley rats. In particular, one or two air puffs, 5-10 msec in duration, 1-2 psi, usually separated by an interval of 40 msec, were applied on the hairy skin of the wrist or the forepaw at the presentation rate of 1/sec. For units unresponsive to air puffs, similar presentation of low intensity electrical stimuli (0.2-5.0 V, 0.2-0.4 msec pulses) were applied through two needles inserted on the most effective area of the skin. Both natural and electrical stimulations of the skin were applied under control conditions, as well as 50 msec after a 250 msec train of 0.3 msec pulses at 40 Hz. 20-30 microA applied stereotaxically to the LC complex through a tungsten microelectrode. 2. Not all cortical units exhibited spontaneous discharge. Most of the units, however, which were spontaneously active, were inhibited by electrical stimulation of the LC complex, while the remaining ones were excited. The sites of stimulation, which included either the LC proper or the locus subcoeruleus, were identified following both anatomical and physiological criteria. 3. SI neurons recorded at sites between 400 and 950 microns below the surface of the cortex, thus being most likely granule cells of layers III and IV, responded to cutaneous stimuli with spikes which occurred with a latency of 20-30 msec in response to single air puffs and a latency of 15-20 msec in response to single electrical pulses to the skin. In both instances the response to the second stimulus applied at the interstimulus interval of 40 msec was markedly reduced or abolished due to postexcitatory inhibition following the response to the first stimulus (in-field inhibition). In contrast, units particularly located at or below 1000 microns from the cortical surface, which were of very large size probably corresponding to large layer V pyramidal cells, were often difficult to activate with air puffs applied at the centre of the receptive field (RF) and were submitted to electrical stimulation of the skin. 4. Among the 59 isolated SI units tested either to air puffs (45 neurons) or to electrical skin stimulation (14 neurons), 15 units (i.e., 25.4%) were facilitated, while 12 units (i.e., 20.3%) were inhibited following stimulation of the LC complex. 5. A marked feature of the facilitatory effects which usually involved the predominant response to the first air puff, but also the smaller response to the second puff, was that the increase in the number of spikes per stimulus was accompanied by a temporal focusing of the responses characterized by a clear tightening of the latency and narrowing of the peak of activity, which was often accompanied by some level of tonic inhibition of the background discharge. Thus, LC stimulation increased the signal-to-noise ratio of SI neuronal responses to skin stimulation. When inhibitory effects were induced by LC stimulation, they clearly affected the unit response to the first air puff, which was severely depressed. However, the response to the second puff could be facilitated, suggesting that LC stimulation might have produced inhibition of those inhibitory interneurons responsible for the postexcitatory inhibition of the units under examination. Evidence for spatial focusing of the response was not easily documented. In some units, however, LC stimulation produced either facilitation of the responses to puffs at the receptive field center and inhibition of the responses to puffs at the edge at the receptive field or vice versa. 6. Since the LC complex contains in the rat a predominant population of noradrenergic neurons, it is likely that the effects described above were mainly due to activation of these noradrenergic neurons. 7. (ABSTRACT TRUNCATED)

Higher motivation - greater control? The effect of arousal on judgement.

PubMed

Riemer, Hila; Viswanathan, Madhu

2013-01-01

This research examines control over the effect of arousal, a dimension of affect, on judgement. Past research shows that high processing motivation enhances control over the effects of affect on judgement. Isolating and studying arousal as opposed to valence, the other dimension of affect, and its effect on judgement, we identify boundary conditions for past findings. Drawing from the literature on processes by which arousal influences judgement, we demonstrate that the role of motivation is contingent upon the type of judgement task (i.e., memory- versus stimulus-based judgement). In stimulus-based judgement, individuals exert greater control over the effect of arousal on judgement under low compared to high motivation. In contrast, in memory-based judgement individuals exert greater control over the effect of arousal under high compared to low motivation. Theoretical implications and avenues for future research are discussed.

Stimulus-evoked outer segment changes in rod photoreceptors

NASA Astrophysics Data System (ADS)

Zhao, Xiaohui; Thapa, Damber; Wang, Benquan; Lu, Yiming; Gai, Shaoyan; Yao, Xincheng

2016-06-01

Rod-dominated transient retinal phototropism (TRP) has been recently observed in freshly isolated mouse and frog retinas. Comparative confocal microscopy and optical coherence tomography revealed that the TRP was predominantly elicited from the rod outer segment (OS). However, the biophysical mechanism of rod OS dynamics is still unknown. Mouse and frog retinal slices, which displayed a cross-section of retinal photoreceptors and other functional layers, were used to test the effect of light stimulation on rod OSs. Time-lapse microscopy revealed stimulus-evoked conformational changes of rod OSs. In the center of the stimulated region, the length of the rod OS shrunk, while in the peripheral region, the rod OS swung toward the center region. Our experimental observation and theoretical analysis suggest that the TRP may reflect unbalanced rod disc-shape changes due to localized visible light stimulation.

Sensory mediation of stimulus-driven attentional capture in multiple-cue displays.

PubMed

Wright, Richard D; Richard, Christian M

2003-08-01

Three location-cuing experiments were conducted in order to examine the stimulus-driven control of attentional capture in multiple-cue displays. These displays consisted of one to four simultaneously presented direct location cues. The results indicated that direct location cuing can produce cue effects that are mediated, in part, by nonattentional processing that occurs simultaneously at multiple locations. When single cues were presented in isolation, however, the resulting cue effect appeared to be due to a combination of sensory processing and attentional capture by the cue. This suggests that the faster responses produced by direct cues may be associated with two different components: an attention-related component that can be modulated by goal-driven factors and a nonattentional component that occurs in parallel at multiple direct-cue locations and is minimally affected by goal-driven factors.

Stimulus-evoked outer segment changes in rod photoreceptors

PubMed Central

Zhao, Xiaohui; Thapa, Damber; Wang, Benquan; Lu, Yiming; Gai, Shaoyan; Yao, Xincheng

2016-01-01

Abstract. Rod-dominated transient retinal phototropism (TRP) has been recently observed in freshly isolated mouse and frog retinas. Comparative confocal microscopy and optical coherence tomography revealed that the TRP was predominantly elicited from the rod outer segment (OS). However, the biophysical mechanism of rod OS dynamics is still unknown. Mouse and frog retinal slices, which displayed a cross-section of retinal photoreceptors and other functional layers, were used to test the effect of light stimulation on rod OSs. Time-lapse microscopy revealed stimulus-evoked conformational changes of rod OSs. In the center of the stimulated region, the length of the rod OS shrunk, while in the peripheral region, the rod OS swung toward the center region. Our experimental observation and theoretical analysis suggest that the TRP may reflect unbalanced rod disc-shape changes due to localized visible light stimulation. PMID:27334933

Visual attention mitigates information loss in small- and large-scale neural codes.

PubMed

Sprague, Thomas C; Saproo, Sameer; Serences, John T

2015-04-01

The visual system transforms complex inputs into robust and parsimonious neural codes that efficiently guide behavior. Because neural communication is stochastic, the amount of encoded visual information necessarily decreases with each synapse. This constraint requires that sensory signals are processed in a manner that protects information about relevant stimuli from degradation. Such selective processing--or selective attention--is implemented via several mechanisms, including neural gain and changes in tuning properties. However, examining each of these effects in isolation obscures their joint impact on the fidelity of stimulus feature representations by large-scale population codes. Instead, large-scale activity patterns can be used to reconstruct representations of relevant and irrelevant stimuli, thereby providing a holistic understanding about how neuron-level modulations collectively impact stimulus encoding. Copyright © 2015 Elsevier Ltd. All rights reserved.

Temporal cognition: Connecting subjective time to perception, attention, and memory.

PubMed

Matthews, William J; Meck, Warren H

2016-08-01

Time is a universal psychological dimension, but time perception has often been studied and discussed in relative isolation. Increasingly, researchers are searching for unifying principles and integrated models that link time perception to other domains. In this review, we survey the links between temporal cognition and other psychological processes. Specifically, we describe how subjective duration is affected by nontemporal stimulus properties (perception), the allocation of processing resources (attention), and past experience with the stimulus (memory). We show that many of these connections instantiate a "processing principle," according to which perceived time is positively related to perceptual vividity and the ease of extracting information from the stimulus. This empirical generalization generates testable predictions and provides a starting-point for integrated theoretical frameworks. By outlining some of the links between temporal cognition and other domains, and by providing a unifying principle for understanding these effects, we hope to encourage time-perception researchers to situate their work within broader theoretical frameworks, and that researchers from other fields will be inspired to apply their insights, techniques, and theorizing to improve our understanding of the representation and judgment of time. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Emphasis of spatial cues in the temporal fine structure during the rising segments of amplitude-modulated sounds

PubMed Central

Dietz, Mathias; Marquardt, Torsten; Salminen, Nelli H.; McAlpine, David

2013-01-01

The ability to locate the direction of a target sound in a background of competing sources is critical to the survival of many species and important for human communication. Nevertheless, brain mechanisms that provide for such accurate localization abilities remain poorly understood. In particular, it remains unclear how the auditory brain is able to extract reliable spatial information directly from the source when competing sounds and reflections dominate all but the earliest moments of the sound wave reaching each ear. We developed a stimulus mimicking the mutual relationship of sound amplitude and binaural cues, characteristic to reverberant speech. This stimulus, named amplitude modulated binaural beat, allows for a parametric and isolated change of modulation frequency and phase relations. Employing magnetoencephalography and psychoacoustics it is demonstrated that the auditory brain uses binaural information in the stimulus fine structure only during the rising portion of each modulation cycle, rendering spatial information recoverable in an otherwise unlocalizable sound. The data suggest that amplitude modulation provides a means of “glimpsing” low-frequency spatial cues in a manner that benefits listening in noisy or reverberant environments. PMID:23980161

Effects of five oleanolic acid triterpenoid saponins from the rhizome of Anemone raddeana on stimulus-induced superoxide generation, phosphorylation of proteins and translocation of cytosolic compounds to cell membrane in human neutrophils.

PubMed

Wei, Shihu; He, Wenfei; Lu, Jincai; Wang, Zhonghuan; Yamashita, Koichi; Yokoyama, Masanori; Kodama, Hiroyuki

2012-03-01

Five oleanolic acid triterpenoid saponins (OTS-1, 2, 3, 4 and 5) were isolated from the rhizome of Anemone raddeana. The effect of these triterpenoid saponins on stimulus-induced superoxide generation in human neutrophils was assayed by measuring the reduction of ferricytochrome c using a dual-beam spectrophotometer. The phosphorylation of neutrophil proteins, and translocation of p67(phox), p47(phox) and Rac to plasma membrane were investigated using specific monoclonal antibodies. The five oleanolic acid triterpenoid saponins used in this experiment suppressed N-formyl-methionyl-leucyl-phenylalanine (fMLP)-induced superoxide generation in a concentration-dependent manner. OTS-1, 2 and 4 suppressed phorbol 12-myristate 13-acetate (PMA)- and arachidonic acid (AA)-induced superoxide generation in a concentration-dependent manner, but OTS-3 and 5 showed no effect. fMLP- and PMA-induced tyrosyl or serine/threonine phosphorylation, and fMLP-, PMA- and AA-induced translocation of p67(phox), p47(phox) and Rac to plasma membrane were in parallel with the suppression of the stimulus-induced superoxide generation. Copyright © 2011 Elsevier B.V. All rights reserved.

Physiological reactivity of pregnant women to evoked fetal startle

PubMed Central

DiPietro, Janet A.; Voegtline, Kristin M.; Costigan, Kathleen A.; Aguirre, Frank; Kivlighan, Katie; Chen, Ping

2013-01-01

Objective The bidirectional nature of mother-child interaction is widely acknowledged during infancy and childhood. Prevailing models during pregnancy focus on unidirectional influences exerted by the pregnant woman on the developing fetus. Prior work has indicated that the fetus also affects the pregnant woman. Our objective was to determine whether a maternal psychophysiological response to stimulation of the fetus could be isolated. Methods Using a longitudinal design, an airborne auditory stimulus was used to elicit a fetal heart rate and motor response at 24 (n = 47) and 36 weeks (n = 45) gestation. Women were blind to condition (stimulus versus sham). Maternal parameters included cardiac (heart rate) and electrodermal (skin conductance) responses. Multilevel modeling of repeated measures with 5 data points per second was used to examine fetal and maternal responses. Results As expected, compared to a sham condition, the stimulus generated a fetal motor response at both gestational ages, consistent with a mild fetal startle. Fetal stimulation was associated with significant, transient slowing of maternal heart rate coupled with increased skin conductance within 10 s of the stimulus at both gestational ages. Nulliparous women showed greater electrodermal responsiveness. The magnitude of the fetal motor response significantly corresponded to the maternal skin conductance response at 5, 10, 15, and 30 s following stimulation. Conclusion Elicited fetal movement exerts an independent influence on the maternal autonomic nervous system. This finding contributes to current models of the dyadic relationship during pregnancy between fetus and pregnant woman. PMID:24119937

Visual Cues Contribute Differentially to Audiovisual Perception of Consonants and Vowels in Improving Recognition and Reducing Cognitive Demands in Listeners with Hearing Impairment Using Hearing Aids

ERIC Educational Resources Information Center

Moradi, Shahram; Lidestam, Bjorn; Danielsson, Henrik; Ng, Elaine Hoi Ning; Ronnberg, Jerker

2017-01-01

Purpose: We sought to examine the contribution of visual cues in audiovisual identification of consonants and vowels--in terms of isolation points (the shortest time required for correct identification of a speech stimulus), accuracy, and cognitive demands--in listeners with hearing impairment using hearing aids. Method: The study comprised 199…

Allelopathic and bioherbicidal potential of Cladonia verticillaris on the germination and growth of Lactuca sativa.

PubMed

Tigre, R C; Silva, N H; Santos, M G; Honda, N K; Falcão, E P S; Pereira, E C

2012-10-01

Responses to germination and initial growth of Lactuca sativa (lettuce) submitted to organic extracts and purified compounds of Cladonia verticillaris ("salambaia") were analyzed in this work. The experiments were conducted in laboratory conditions using extracts and pure compounds at different concentrations. None of the assays showed any influence on the germination of L. sativa seeds using C. verticillaris extracts; however, modifications in leaf area and seedling hypocotyl and root development occurred. In the growth experiments, seedlings exposed to ether or acetone extract showed diminished hypocotyl growth in detriment to the root stimulus, compared to controls. Increases in extract concentrations led to the formation of abnormal seedlings. To determine the allelochemicals of C. verticillaris, its principal components, fumarprotocetraric and protocetraric acids, were isolated and then analyzed by high performance liquid chromatography (HPLC). When the seedlings were exposed to the two acids separately, presented increased leaf area at all concentrations. In contrast, hypocotyl and root stimulus was observed only in the presence of protocetraric acid at different concentrations. Fumarprotocetraric as well as protocetraric acids, isolated and purified from C. verticillaris and Parmotrema dilatatum respectively, influenced the development of L. sativa seedlings at high concentrations, indicating a possible bioherbicide potential of these acids. Crown Copyright © 2012. Published by Elsevier Inc. All rights reserved.

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.

The ventricular intracardiac unipolar paced-evoked potential in an isolated animal heart.

PubMed

Economides, A P; Walton, C; Gergely, S

1988-02-01

The endocardial unipolar paced evoked response has excited a great deal of interest due to its possible use in the measurement of the metabolic state of the body and other pacer-related areas. Although rate-responsive pacing utilizing this signal has been clinically evaluated, little is known regarding the behavior of the components of this waveform under normal physiological conditions. We have developed an electronic circuit which allows the recording of the evoked response within a few milliseconds of a pacing stimulus of 5 V and 0.5 ms duration being applied using a single unipolar, smooth platinum electrode of 14 mm2 surface area. The paced evoked response was measured using a total of 20 isolated rabbit heart preparations. Five were run for 8 hours and the remaining fifteen were run for 5 hours. Our results indicate that the waveform components of the evoked response remain stable while the preparation is viable, but that two of the time-related measurements change with loss of viability. A significant lengthening of the stimulus-R interval was seen together with a dramatic shortening of the R-T period. The net result of these changes was an overall reduction of 17% in the complex duration. In addition, we found the R-T shortening to be a sensitive measure of myocardial integrity. We conclude that the combination of our interface charge elimination circuit and the isolated heart preparation has proved a useful system for the investigation of the paced evoked potential. Furthermore, the loss of myocardial viability has a complex action on this response.

On a method to detect long-latency excitations and inhibitions of single hand muscle motoneurons in man.

PubMed

Awiszus, F; Feistner, H; Schäfer, S S

1991-01-01

The peri-stimulus-time histogram (PSTH) analysis of stimulus-related neuronal spike train data is usually regarded as a method to detect stimulus-induced excitations or inhibitions. However, for a fairly regularly discharging neuron such as the human alpha-motoneuron, long-latency modulations of a PSTH are difficult to interpret as PSTH modulations can also occur as a consequence of a modulated neuronal autocorrelation. The experiments reported here were made (i) to investigate the extent to which a PSTH of a human hand-muscle motoneuron may be contaminated by features of the autocorrelation and (ii) to develop methods that display the motoneuronal excitations and inhibitions without such contamination. Responses of 29 single motor units to electrical ulnar nerve stimulation below motor threshold were investigated in the first dorsal interosseous muscle of three healthy volunteers using an experimental protocol capable of demonstrating the presence of autocorrelative modulations in the neuronal response. It was found for all units that the PSTH as well as the cumulative sum (CUSUM) derived from these responses were severely affected by the presence of autocorrelative features. On the other hand, calculating the CUSUM in a slightly modified form yielded--for all units investigated--a neuronal output feature sensitive only to motoneuronal excitations and inhibitions induced by the afferent volley. The price that has to be paid to arrive at such a modified CUSUM (mCUSUM) was a high computational effort prohibiting the on-line availability of this output feature during the experiment. It was found, however, that an interspike interval superposition plot (IISP)--easily obtainable during the experiment--is also free of autocorrelative features.(ABSTRACT TRUNCATED AT 250 WORDS)

Functional Dissociation of Latency-Variable, Stimulus- and Response-Locked Target P3 Sub-components in Task-Switching.

PubMed

Brydges, Christopher R; Barceló, Francisco

2018-01-01

Cognitive control warrants efficient task performance in dynamic and changing environments through adjustments in executive attention, stimulus and response selection. The well-known P300 component of the human event-related potential (ERP) has long been proposed to index "context-updating"-critical for cognitive control-in simple target detection tasks. However, task switching ERP studies have revealed both target P3 (300-350 ms) and later sustained P3-like potentials (400-1,200 ms) to first targets ensuing transition cues, although it remains unclear whether these target P3-like potentials also reflect context updating operations. To address this question, we applied novel single-trial EEG analyses-residue iteration decomposition (RIDE)-in order to disentangle target P3 sub-components in a sample of 22 young adults while they either repeated or switched (updated) task rules. The rationale was to revise the context updating hypothesis of P300 elicitation in the light of new evidence suggesting that "the context" consists of not only the sensory units of stimulation, but also associated motor units, and intermediate low- and high-order sensorimotor units, all of which may need to be dynamically updated on a trial by trial basis. The results showed functionally distinct target P3-like potentials in stimulus-locked, response-locked, and intermediate RIDE component clusters overlying parietal and frontal regions, implying multiple functionally distinct, though temporarily overlapping context updating operations. These findings support a reformulated version of the context updating hypothesis, and reveal a rich family of distinct target P3-like sub-components during the reactive control of target detection in task-switching, plausibly indexing the complex and dynamic workings of frontoparietal cortical networks subserving cognitive control.

Functional Dissociation of Latency-Variable, Stimulus- and Response-Locked Target P3 Sub-components in Task-Switching

PubMed Central

Brydges, Christopher R.; Barceló, Francisco

2018-01-01

Cognitive control warrants efficient task performance in dynamic and changing environments through adjustments in executive attention, stimulus and response selection. The well-known P300 component of the human event-related potential (ERP) has long been proposed to index “context-updating”—critical for cognitive control—in simple target detection tasks. However, task switching ERP studies have revealed both target P3 (300–350 ms) and later sustained P3-like potentials (400–1,200 ms) to first targets ensuing transition cues, although it remains unclear whether these target P3-like potentials also reflect context updating operations. To address this question, we applied novel single-trial EEG analyses—residue iteration decomposition (RIDE)—in order to disentangle target P3 sub-components in a sample of 22 young adults while they either repeated or switched (updated) task rules. The rationale was to revise the context updating hypothesis of P300 elicitation in the light of new evidence suggesting that “the context” consists of not only the sensory units of stimulation, but also associated motor units, and intermediate low- and high-order sensorimotor units, all of which may need to be dynamically updated on a trial by trial basis. The results showed functionally distinct target P3-like potentials in stimulus-locked, response-locked, and intermediate RIDE component clusters overlying parietal and frontal regions, implying multiple functionally distinct, though temporarily overlapping context updating operations. These findings support a reformulated version of the context updating hypothesis, and reveal a rich family of distinct target P3-like sub-components during the reactive control of target detection in task-switching, plausibly indexing the complex and dynamic workings of frontoparietal cortical networks subserving cognitive control. PMID:29515383

Relationship between functional electrical stimulation duty cycle and fatigue in wrist extensor muscles of patients with hemiparesis.

PubMed

Packman-Braun, R

1988-01-01

The purpose of this study was to investigate, in a sample of patients with hemiparesis secondary to cerebrovascular accident, the relationship between the ratio of stimulus on time to off time and muscle fatigue using a commercial electrical stimulation unit. An experimental model was used to test the hypothesis that the smaller the stimulus off time relative to stimulus on time, the greater will be the muscle fatigue over time. The wrist extensor muscles of 18 patients with hemiparesis were stimulated electrically, and isometric force output was recorded continuously using an adapted strain gauge-recorder apparatus. For each testing session, peak on time of the electrical stimulus was set at 5 seconds, and off time was set at 5, 15, or 25 seconds. Six randomly assigned treatment groups participated in three separate treatment sessions in a different order at 48-hour intervals. Treatment sessions were continued either until wrist extensor muscle force output decreased to 50% of its initial value or for a maximum of 30 minutes. Data analysis revealed that significant differences in muscle tension developed among all duty cycles (p less than .01). Duty-cycle ratios of 1:1, 1:3, and 1:5 were shown to be progressively less fatiguing. Within the limits of this investigation, the 1:5 duty-cycle ratio was determined to be the best suited for initial use in programs of prolonged stimulation to the wrist extensor muscles of patients with hemiparesis. The hypothesis was accepted that the smaller the stimulus off time (rest interval) with respect to the stimulus on time, the greater will be the muscle fatigue over time.

A Decline in Response Variability Improves Neural Signal Detection during Auditory Task Performance.

PubMed

von Trapp, Gardiner; Buran, Bradley N; Sen, Kamal; Semple, Malcolm N; Sanes, Dan H

2016-10-26

The detection of a sensory stimulus arises from a significant change in neural activity, but a sensory neuron's response is rarely identical to successive presentations of the same stimulus. Large trial-to-trial variability would limit the central nervous system's ability to reliably detect a stimulus, presumably affecting perceptual performance. However, if response variability were to decrease while firing rate remained constant, then neural sensitivity could improve. Here, we asked whether engagement in an auditory detection task can modulate response variability, thereby increasing neural sensitivity. We recorded telemetrically from the core auditory cortex of gerbils, both while they engaged in an amplitude-modulation detection task and while they sat quietly listening to the identical stimuli. Using a signal detection theory framework, we found that neural sensitivity was improved during task performance, and this improvement was closely associated with a decrease in response variability. Moreover, units with the greatest change in response variability had absolute neural thresholds most closely aligned with simultaneously measured perceptual thresholds. Our findings suggest that the limitations imposed by response variability diminish during task performance, thereby improving the sensitivity of neural encoding and potentially leading to better perceptual sensitivity. The detection of a sensory stimulus arises from a significant change in neural activity. However, trial-to-trial variability of the neural response may limit perceptual performance. If the neural response to a stimulus is quite variable, then the response on a given trial could be confused with the pattern of neural activity generated when the stimulus is absent. Therefore, a neural mechanism that served to reduce response variability would allow for better stimulus detection. By recording from the cortex of freely moving animals engaged in an auditory detection task, we found that variability of the neural response becomes smaller during task performance, thereby improving neural detection thresholds. Copyright © 2016 the authors 0270-6474/16/3611097-10$15.00/0.

A Decline in Response Variability Improves Neural Signal Detection during Auditory Task Performance

PubMed Central

Buran, Bradley N.; Sen, Kamal; Semple, Malcolm N.; Sanes, Dan H.

2016-01-01

The detection of a sensory stimulus arises from a significant change in neural activity, but a sensory neuron's response is rarely identical to successive presentations of the same stimulus. Large trial-to-trial variability would limit the central nervous system's ability to reliably detect a stimulus, presumably affecting perceptual performance. However, if response variability were to decrease while firing rate remained constant, then neural sensitivity could improve. Here, we asked whether engagement in an auditory detection task can modulate response variability, thereby increasing neural sensitivity. We recorded telemetrically from the core auditory cortex of gerbils, both while they engaged in an amplitude-modulation detection task and while they sat quietly listening to the identical stimuli. Using a signal detection theory framework, we found that neural sensitivity was improved during task performance, and this improvement was closely associated with a decrease in response variability. Moreover, units with the greatest change in response variability had absolute neural thresholds most closely aligned with simultaneously measured perceptual thresholds. Our findings suggest that the limitations imposed by response variability diminish during task performance, thereby improving the sensitivity of neural encoding and potentially leading to better perceptual sensitivity. SIGNIFICANCE STATEMENT The detection of a sensory stimulus arises from a significant change in neural activity. However, trial-to-trial variability of the neural response may limit perceptual performance. If the neural response to a stimulus is quite variable, then the response on a given trial could be confused with the pattern of neural activity generated when the stimulus is absent. Therefore, a neural mechanism that served to reduce response variability would allow for better stimulus detection. By recording from the cortex of freely moving animals engaged in an auditory detection task, we found that variability of the neural response becomes smaller during task performance, thereby improving neural detection thresholds. PMID:27798189

Women Artists: Multicultural Visions.

ERIC Educational Resources Information Center

LaDuke, Betty

This resource gathers together explorations of women's art from Asia, Latin America, Eastern Europe, and the United States as a stimulus for interdisciplinary discussion and investigation. Part 1, "Art, Ecology, and Spirituality", focuses on traditional artists from Borneo, India, and Mexico, whose symbolic images are linked to goddesses…

Unitary Responses in Frog Olfactory Epithelium to Sterically Related Molecules at Low Concentrations

PubMed Central

Getchell, Thomas V.

1974-01-01

Responses of receptor cells in the frog's olfactory epithelium were recorded using platinum-black metal-filled microelectrodes. Spontaneous activity varied over a wide range from 0.07 to 1.8 spikes/s. Mean interspike intervals ranged from 13.7 to 0.5 s. Excitatory responses to six sterically related compounds at low concentrations were investigated. Stimuli were delivered in an aqueous medium. Thresholds for impulse initiation varied from greater than 1 mM down to the nanomolar concentration range. Thresholds of different olfactory receptors to the same stimulus could vary by several log units. Thresholds of the same receptor cell to different stimuli could be within the same order of magnitude, or could vary by as much as 5 log units. Based upon quantitative measures of stimulus-evoked excitatory responses it appeared that some receptors did not discriminate among sterically related molecules, whereas other receptors clearly discriminated between stimuli which evoke similar odor sensations. PMID:4211101

Responses of prefrontal multisensory neurons to mismatching faces and vocalizations.

PubMed

Diehl, Maria M; Romanski, Lizabeth M

2014-08-20

Social communication relies on the integration of auditory and visual information, which are present in faces and vocalizations. Evidence suggests that the integration of information from multiple sources enhances perception compared with the processing of a unimodal stimulus. Our previous studies demonstrated that single neurons in the ventrolateral prefrontal cortex (VLPFC) of the rhesus monkey (Macaca mulatta) respond to and integrate conspecific vocalizations and their accompanying facial gestures. We were therefore interested in how VLPFC neurons respond differentially to matching (congruent) and mismatching (incongruent) faces and vocalizations. We recorded VLPFC neurons during the presentation of movies with congruent or incongruent species-specific facial gestures and vocalizations as well as their unimodal components. Recordings showed that while many VLPFC units are multisensory and respond to faces, vocalizations, or their combination, a subset of neurons showed a significant change in neuronal activity in response to incongruent versus congruent vocalization movies. Among these neurons, we typically observed incongruent suppression during the early stimulus period and incongruent enhancement during the late stimulus period. Incongruent-responsive VLPFC neurons were both bimodal and nonlinear multisensory, fostering their ability to respond to changes in either modality of a face-vocalization stimulus. These results demonstrate that ventral prefrontal neurons respond to changes in either modality of an audiovisual stimulus, which is important in identity processing and for the integration of multisensory communication information. Copyright © 2014 the authors 0270-6474/14/3411233-11$15.00/0.

Stimulus induced bursts in severe postanoxic encephalopathy.

PubMed

Tjepkema-Cloostermans, Marleen C; Wijers, Elisabeth T; van Putten, Michel J A M

2016-11-01

To report on a distinct effect of auditory and sensory stimuli on the EEG in comatose patients with severe postanoxic encephalopathy. In two comatose patients admitted to the Intensive Care Unit (ICU) with severe postanoxic encephalopathy and burst-suppression EEG, we studied the effect of external stimuli (sound and touch) on the occurrence of bursts. In patient A bursts could be induced by either auditory or sensory stimuli. In patient B bursts could only be induced by touching different facial regions (forehead, nose and chin). When stimuli were presented with relatively long intervals, bursts persistently followed the stimuli, while stimuli with short intervals (<1s) did not induce bursts. In both patients bursts were not accompanied by myoclonia. Both patients deceased. Bursts in patients with a severe postanoxic encephalopathy can be induced by external stimuli, resulting in stimulus-dependent burst-suppression. Stimulus induced bursts should not be interpreted as prognostic favourable EEG reactivity. Copyright © 2016 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Autonomous Motility of Polymer Films.

PubMed

Treml, Benjamin E; McKenzie, Ruel N; Buskohl, Philip; Wang, David; Kuhn, Michael; Tan, Loon-Seng; Vaia, Richard A

2018-02-01

Adaptive soft materials exhibit a diverse set of behaviors including reconfiguration, actuation, and locomotion. These responses however, are typically optimized in isolation. Here, the interrelation between these behaviors is established through a state space framework, using Nylon 6 thin films in a humidity gradient as an experimental testbed. It is determined that the dynamic behaviors are a result of not only a response to but also an interaction with the applied stimulus, which can be tuned via control of the environment and film characteristics, including size, permeability, and coefficient of hygroscopic expansion to target a desired behavior such as multimodal locomotion. Using these insights, it is demonstrated that films simultaneously harvest energy and information from the environment to autonomously move down a stimulus gradient. Improved understanding of the coupling between an adaptive material and its environment aids the development of materials that integrate closed loop autonomous sensing, actuation, and locomotion. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Optical, thermal and dielectric studies in linear hydrogen bonded liquid crystal homologous series

NASA Astrophysics Data System (ADS)

Vijayakumar, V. N.; Madhu Mohan, M. L. N.

2011-08-01

A novel series of hydrogen bonded liquid crystals (HBLC) have been isolated with hydrogen bond forming between fluoro benzoic acid and various alkyloxy benzoic acids respectively. Phase diagram is constructed from the transition temperatures obtained by Differential Scanning Calorimetry (DSC) and Polarizing Optical Microscopic (POM) studies. A new Smectic ordering which is referred as Smectic R is characterized which exhibits a ribbon like phase. Declinations are observed on these ribbons manifesting the presence of the helicoidal structure. Another interesting feature is the observation of optical shuttering action in some of the complexes with the application of external stimulus in the entire thermal range of Nematic phase. Further this phenomenon is reversible in the sense that when the applied stimulus is withdrawn original texture of Nematic is restored. Unwinding of the helix coupled with molecular dipolar reorientation with the application of external field is supposed to be the major reasons for the observed phenomenon.

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.

Electric stimulus duration alters network-mediated responses depending on retinal ganglion cell type

NASA Astrophysics Data System (ADS)

Im, Maesoon; Werginz, Paul; Fried, Shelley I.

2018-06-01

Objective. To improve the quality of artificial vision that arises from retinal prostheses, it is important to bring electrically-elicited neural activity more in line with the physiological signaling patterns that arise normally in the healthy retina. Our previous study reported that indirect activation produces a closer match to physiological responses in ON retinal ganglion cells (RGCs) than in OFF cells (Im and Fried 2015 J. Physiol. 593 3677-96). This suggests that a preferential activation of ON RGCs would shape the overall retinal response closer to natural signaling. Recently, we found that changes to the rate at which stimulation was delivered could bias responses towards a stronger ON component (Im and Fried 2016a J. Neural Eng. 13 025002), raising the possibility that changes to other stimulus parameters can similarly bias towards stronger ON responses. Here, we explore the effects of changing stimulus duration on the responses in ON and OFF types of brisk transient (BT) and brisk sustained (BS) RGCs. Approach. We used cell-attached patch clamp to record RGC spiking in the isolated rabbit retina. Targeted RGCs were first classified as ON or OFF type by their light responses, and further sub-classified as BT or BS types by their responses to both light and electric stimuli. Spiking in targeted RGCs was recorded in response to electric pulses with durations varying from 5 to100 ms. Stimulus amplitude was adjusted at each duration to hold total charge constant for all experiments. Main results. We found that varying stimulus durations modulated responses differentially for ON versus OFF cells: in ON cells, spike counts decreased significantly with increasing stimulus duration while in OFF cells the changes were more modest. The maximum ratio of ON versus OFF responses occurred at a duration of ~10 ms. The difference in response strength for BT versus BS cells was much larger in ON cells than in OFF cells. Significance. The stimulation rates preferred by subjects during clinical trials are similar to the rates that maximize the ON/OFF response ratio in in vitro testing (Im and Fried 2016a J. Neural Eng. 13 025002). Here, we determine the stimulus duration that produces the strongest bias towards ON responses and speculate that it will further enhance clinical effectiveness.

Neuropeptide Y is a prejunctional inhibitor of vagal but not sympathetic inotropic responses in guinea-pig isolated left atria

PubMed Central

Serone, Adrian P; Angus, James A

1999-01-01

The effects of NPY and related peptides were examined on basal contractile force and nerve-mediated inotropic responses to electrical field stimulation of the guinea-pig isolated left atrium.Electrical field stimulus (EFS)-inotropic response curves were constructed by applying 1-64 trains of four field pulses (200 Hz, 0.1 ms duration, 100 V) across isolated left atria (paced at 4 Hz, 2 ms, 1–4 V) within the atrial refractory period. Curves were constructed in presence of vehicle, propranolol (1 μM) or atropine (1 μM) to determine appropriate stimulus conditions.The effects of PYY (1–10,000 nM), NPY (0.01–10 μM), N-Ac-[Leu28,31]NPY(24–36) (N-A[L]NPY(24–36); 0.01–10 μM) and clonidine (0.1–1000 nM) were examined on the positive and negative inotropic responses to EFS (eight trains, four pulses per refractory period).NPY-related peptides had no effect on basal force of contraction nor on the inotropic concentration-response curves to bethanechol or isoprenaline. All three peptides inhibited vagally-mediated negative inotropic responses; rank order of potency PYY>NPY⩾N-A[L]NPY(24–36) was consistent with an action at prejunctional Y2-receptors. Clonidine concentration-dependently inhibited sympathetic inotropic responses. However, PYY, NPY and N-A[L]NPY(24–36) failed to mediate any significant inhibition of the positive inotropic response to EFS.These data demonstrate that NPY is an effective inhibitor of vagal but not sympathetically-mediated inotropic responses in the guinea-pig isolated left atria. This may suggest that endogenously co-released NPY is important in mediating cross talk between efferent components of the autonomic nervous system modulating cardiac contractility, acting overall to sustain positive inotropic responses. PMID:10385237

Generalization of value in reinforcement learning by humans.

PubMed

Wimmer, G Elliott; Daw, Nathaniel D; Shohamy, Daphna

2012-04-01

Research in decision-making has focused on the role of dopamine and its striatal targets in guiding choices via learned stimulus-reward or stimulus-response associations, behavior that is well described by reinforcement learning theories. However, basic reinforcement learning is relatively limited in scope and does not explain how learning about stimulus regularities or relations may guide decision-making. A candidate mechanism for this type of learning comes from the domain of memory, which has highlighted a role for the hippocampus in learning of stimulus-stimulus relations, typically dissociated from the role of the striatum in stimulus-response learning. Here, we used functional magnetic resonance imaging and computational model-based analyses to examine the joint contributions of these mechanisms to reinforcement learning. Humans performed a reinforcement learning task with added relational structure, modeled after tasks used to isolate hippocampal contributions to memory. On each trial participants chose one of four options, but the reward probabilities for pairs of options were correlated across trials. This (uninstructed) relationship between pairs of options potentially enabled an observer to learn about option values based on experience with the other options and to generalize across them. We observed blood oxygen level-dependent (BOLD) activity related to learning in the striatum and also in the hippocampus. By comparing a basic reinforcement learning model to one augmented to allow feedback to generalize between correlated options, we tested whether choice behavior and BOLD activity were influenced by the opportunity to generalize across correlated options. Although such generalization goes beyond standard computational accounts of reinforcement learning and striatal BOLD, both choices and striatal BOLD activity were better explained by the augmented model. Consistent with the hypothesized role for the hippocampus in this generalization, functional connectivity between the ventral striatum and hippocampus was modulated, across participants, by the ability of the augmented model to capture participants' choice. Our results thus point toward an interactive model in which striatal reinforcement learning systems may employ relational representations typically associated with the hippocampus. © 2012 The Authors. European Journal of Neuroscience © 2012 Federation of European Neuroscience Societies and Blackwell Publishing Ltd.

Level-tolerant duration selectivity in the auditory cortex of the velvety free-tailed bat Molossus molossus.

PubMed

Macías, Silvio; Hernández-Abad, Annette; Hechavarría, Julio C; Kössl, Manfred; Mora, Emanuel C

2015-05-01

It has been reported previously that in the inferior colliculus of the bat Molossus molossus, neuronal duration tuning is ambiguous because the tuning type of the neurons dramatically changes with the sound level. In the present study, duration tuning was examined in the auditory cortex of M. molossus to describe if it is as ambiguous as the collicular tuning. From a population of 174 cortical 104 (60 %) neurons did not show duration selectivity (all-pass). Around 5 % (9 units) responded preferentially to stimuli having longer durations showing long-pass duration response functions, 35 (20 %) responded to a narrow range of stimulus durations showing band-pass duration response functions, 24 (14 %) responded most strongly to short stimulus durations showing short-pass duration response functions and two neurons (1 %) responded best to two different stimulus durations showing a two-peaked duration-response function. The majority of neurons showing short- (16 out of 24) and band-pass (24 out 35) selectivity displayed "O-shaped" duration response areas. In contrast to the inferior colliculus, duration tuning in the auditory cortex of M. molossus appears level tolerant. That is, the type of duration selectivity and the stimulus duration eliciting the maximum response were unaffected by changing sound level.

Dual Functions of Perirhinal Cortex in Fear Conditioning

PubMed Central

Kent, Brianne A.; Brown, Thomas H.

2012-01-01

The present review examines the role of perirhinal cortex (PRC) in Pavlovian fear conditioning. The focus is on rats, partly because so much is known, behaviorally and neurobiologically, about fear conditioning in these animals. In addition, the neuroanatomy and neurophysiology of rat PRC have been described in considerable detail at the cellular and systems levels. The evidence suggests that PRC can serve at least two types of mnemonic functions in Pavlovian fear conditioning. The first function, termed "stimulus unitization," refers to the ability to treat two or more separate items or stimulus elements as a single entity. Supporting evidence for this perceptual function comes from studies of context conditioning as well as delay conditioning to discontinuous auditory cues. In a delay paradigm, the conditional stimulus (CS) and unconditional stimulus (US) overlap temporally and co-terminate. The second PRC function entails a type of "transient memory." Supporting evidence comes from studies of trace cue conditioning, where there is a temporal gap or trace interval between the CS offset and the US onset. For learning to occur, there must be a transient CS representation during the trace interval. We advance a novel neurophysiological mechanism for this transient representation. These two hypothesized functions of PRC are consistent with inferences based on non-aversive forms of learning. PMID:22903623

Reward inference by primate prefrontal and striatal neurons.

PubMed

Pan, Xiaochuan; Fan, Hongwei; Sawa, Kosuke; Tsuda, Ichiro; Tsukada, Minoru; Sakagami, Masamichi

2014-01-22

The brain contains multiple yet distinct systems involved in reward prediction. To understand the nature of these processes, we recorded single-unit activity from the lateral prefrontal cortex (LPFC) and the striatum in monkeys performing a reward inference task using an asymmetric reward schedule. We found that neurons both in the LPFC and in the striatum predicted reward values for stimuli that had been previously well experienced with set reward quantities in the asymmetric reward task. Importantly, these LPFC neurons could predict the reward value of a stimulus using transitive inference even when the monkeys had not yet learned the stimulus-reward association directly; whereas these striatal neurons did not show such an ability. Nevertheless, because there were two set amounts of reward (large and small), the selected striatal neurons were able to exclusively infer the reward value (e.g., large) of one novel stimulus from a pair after directly experiencing the alternative stimulus with the other reward value (e.g., small). Our results suggest that although neurons that predict reward value for old stimuli in the LPFC could also do so for new stimuli via transitive inference, those in the striatum could only predict reward for new stimuli via exclusive inference. Moreover, the striatum showed more complex functions than was surmised previously for model-free learning.

Anopheline and culicine mosquitoes are not repelled by surfaces treated with the entomopathogenic fungi Metarhizium anisopliae and Beauveria bassiana.

PubMed

Mnyone, Ladslaus L; Koenraadt, Constantianus Jm; Lyimo, Issa N; Mpingwa, Monica W; Takken, Willem; Russell, Tanya L

2010-08-27

Entomopathogenic fungi, Metarhizium anisopliae and Beauveria bassiana, are promising bio-pesticides for application against adult malaria mosquito vectors. An understanding of the behavioural responses of mosquitoes towards these fungi is necessary to guide development of fungi beyond the 'proof of concept' stage and to design suitable intervention tools. Here we tested whether oil-formulations of the two fungi could be detected and avoided by adult Anopheles gambiae s.s., Anopheles arabiensis and Culex quinquefasciatus. The bioassays used a glass chamber divided into three compartments (each 250 × 250 × 250 mm): release, middle and stimulus compartments. Netting with or without fungus was fitted in front of the stimulus compartment. Mosquitoes were released and the proportion that entered the stimulus compartment was determined and compared between treatments. Treatments were untreated netting (control 1), netting with mineral oil (control 2) and fungal conidia formulated in mineral oil evaluated at three different dosages (2 × 1010, 4 × 1010 and 8 × 1010 conidia m-2). Neither fungal strain was repellent as the mean proportion of mosquitoes collected in the stimulus compartment did not differ between experiments with surfaces treated with and without fungus regardless of the fungal isolate and mosquito species tested. Our results indicate that mineral-oil formulations of M. anisopliae and B. bassiana were not repellent against the mosquito species tested. Therefore, both fungi are suitable candidates for the further development of tools that aim to control host-seeking or resting mosquitoes using entomopathogenic fungi.

Anopheline and culicine mosquitoes are not repelled by surfaces treated with the entomopathogenic fungi Metarhizium anisopliae and Beauveria bassiana

PubMed Central

2010-01-01

Background Entomopathogenic fungi, Metarhizium anisopliae and Beauveria bassiana, are promising bio-pesticides for application against adult malaria mosquito vectors. An understanding of the behavioural responses of mosquitoes towards these fungi is necessary to guide development of fungi beyond the 'proof of concept' stage and to design suitable intervention tools. Methods Here we tested whether oil-formulations of the two fungi could be detected and avoided by adult Anopheles gambiae s.s., Anopheles arabiensis and Culex quinquefasciatus. The bioassays used a glass chamber divided into three compartments (each 250 × 250 × 250 mm): release, middle and stimulus compartments. Netting with or without fungus was fitted in front of the stimulus compartment. Mosquitoes were released and the proportion that entered the stimulus compartment was determined and compared between treatments. Treatments were untreated netting (control 1), netting with mineral oil (control 2) and fungal conidia formulated in mineral oil evaluated at three different dosages (2 × 1010, 4 × 1010 and 8 × 1010 conidia m-2). Results Neither fungal strain was repellent as the mean proportion of mosquitoes collected in the stimulus compartment did not differ between experiments with surfaces treated with and without fungus regardless of the fungal isolate and mosquito species tested. Conclusion Our results indicate that mineral-oil formulations of M. anisopliae and B. bassiana were not repellent against the mosquito species tested. Therefore, both fungi are suitable candidates for the further development of tools that aim to control host-seeking or resting mosquitoes using entomopathogenic fungi. PMID:20799937

Strategic Implications of the Native Hawaiian Sovereignty Movement

DTIC Science & Technology

2010-11-09

and domestic histories of both Mexico and the United States, and has a defining impact on the gains and losses of territorial land between the two...Type B (HIB), Hepatitis B and Varicella (Chickenpox).18 In 2009, Hawaii received over 7.4 million in stimulus funding from the Federal Government

Reinventing School Finance: Falling Forward

ERIC Educational Resources Information Center

Picus, Lawrence O.; Odden, Allan R.

2011-01-01

States and school districts are facing unprecedented financial pressure due to the continued poor performance of the United States's economy. Dramatic shortfalls in funding due to reduced tax collections were held off for 2 years thanks to federal stimulus funds, but with these revenues already consumed and little likelihood of more in the near…

Heirs of Osler: medical bibliophiles in America.

PubMed

Saffron, M H

1992-11-01

An heir is one who appears to acquire a trait from a predecessor or carries on his tradition. The author presents details about the great bibliophiles who received their stimulus from William Osler, his associates, or his writings. William Osler influenced the formation of private libraries in the United States.

On the search for an appropriate metric for reaction time to suprathreshold increments and decrements.

PubMed

Vassilev, Angel; Murzac, Adrian; Zlatkova, Margarita B; Anderson, Roger S

2009-03-01

Weber contrast, DeltaL/L, is a widely used contrast metric for aperiodic stimuli. Zele, Cao & Pokorny [Zele, A. J., Cao, D., & Pokorny, J. (2007). Threshold units: A correct metric for reaction time? Vision Research, 47, 608-611] found that neither Weber contrast nor its transform to detection-threshold units equates human reaction times in response to luminance increments and decrements under selective rod stimulation. Here we show that their rod reaction times are equated when plotted against the spatial luminance ratio between the stimulus and its background (L(max)/L(min), the larger and smaller of background and stimulus luminances). Similarly, reaction times to parafoveal S-cone selective increments and decrements from our previous studies [Murzac, A. (2004). A comparative study of the temporal characteristics of processing of S-cone incremental and decremental signals. PhD thesis, New Bulgarian University, Sofia, Murzac, A., & Vassilev, A. (2004). Reaction time to S-cone increments and decrements. In: 7th European conference on visual perception, Budapest, August 22-26. Perception, 33, 180 (Abstract).], are better described by the spatial luminance ratio than by Weber contrast. We assume that the type of stimulus detection by temporal (successive) luminance discrimination, by spatial (simultaneous) luminance discrimination or by both [Sperling, G., & Sondhi, M. M. (1968). Model for visual luminance discrimination and flicker detection. Journal of the Optical Society of America, 58, 1133-1145.] determines the appropriateness of one or other contrast metric for reaction time.

Pramipexole-induced disruption of behavioral processes fundamental to intertemporal choice.

PubMed

Johnson, Patrick S; Stein, Jeffrey S; Smits, Rochelle R; Madden, Gregory J

2013-05-01

Evaluating the effects of presession drug administration on intertemporal choice in nonhumans is a useful approach for identifying compounds that promote impulsive behavior in clinical populations, such as those prescribed the dopamine agonist pramipexole (PPX). Based on the results of previous studies, it is unclear whether PPX increases rats' impulsive choice or attenuates aspects of stimulus control. The present study was designed to experimentally isolate behavioral processes fundamental to intertemporal choice and challenge them pharmacologically with PPX administration. In Experiment 1, the hypothesis that PPX increases impulsive choice as a result of enhanced sensitivity to reinforcer delays was tested and disconfirmed. That is, acute PPX diminished delay sensitivity in a manner consistent with disruption of stimulus control whereas repeated PPX had no effect on delay sensitivity. Experiments 2 and 3 elaborated upon this finding by examining the effects of repeated PPX on rats' discrimination of response-reinforcer contingencies and reinforcer amounts, respectively. Accuracy of both discriminations was reduced by PPX. Collectively these results provide no support for past studies that have suggested PPX increases impulsive choice. Instead, PPX impairs stimulus control over choice behavior. The behavioral approach adopted herein could be profitably integrated with genetic and other biobehavioral models to advance our understanding of impulsive behavior associated with drug administration. © Society for the Experimental Analysis of Behavior.

Visual cortex responses reflect temporal structure of continuous quasi-rhythmic sensory stimulation.

PubMed

Keitel, Christian; Thut, Gregor; Gross, Joachim

2017-02-01

Neural processing of dynamic continuous visual input, and cognitive influences thereon, are frequently studied in paradigms employing strictly rhythmic stimulation. However, the temporal structure of natural stimuli is hardly ever fully rhythmic but possesses certain spectral bandwidths (e.g. lip movements in speech, gestures). Examining periodic brain responses elicited by strictly rhythmic stimulation might thus represent ideal, yet isolated cases. Here, we tested how the visual system reflects quasi-rhythmic stimulation with frequencies continuously varying within ranges of classical theta (4-7Hz), alpha (8-13Hz) and beta bands (14-20Hz) using EEG. Our findings substantiate a systematic and sustained neural phase-locking to stimulation in all three frequency ranges. Further, we found that allocation of spatial attention enhances EEG-stimulus locking to theta- and alpha-band stimulation. Our results bridge recent findings regarding phase locking ("entrainment") to quasi-rhythmic visual input and "frequency-tagging" experiments employing strictly rhythmic stimulation. We propose that sustained EEG-stimulus locking can be considered as a continuous neural signature of processing dynamic sensory input in early visual cortices. Accordingly, EEG-stimulus locking serves to trace the temporal evolution of rhythmic as well as quasi-rhythmic visual input and is subject to attentional bias. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

Low-level and high-level modulations of fixational saccades and high frequency oscillatory brain activity in a visual object classification task

PubMed Central

Kosilo, Maciej; Wuerger, Sophie M.; Craddock, Matt; Jennings, Ben J.; Hunt, Amelia R.; Martinovic, Jasna

2013-01-01

Until recently induced gamma-band activity (GBA) was considered a neural marker of cortical object representation. However, induced GBA in the electroencephalogram (EEG) is susceptible to artifacts caused by miniature fixational saccades. Recent studies have demonstrated that fixational saccades also reflect high-level representational processes. Do high-level as opposed to low-level factors influence fixational saccades? What is the effect of these factors on artifact-free GBA? To investigate this, we conducted separate eye tracking and EEG experiments using identical designs. Participants classified line drawings as objects or non-objects. To introduce low-level differences, contours were defined along different directions in cardinal color space: S-cone-isolating, intermediate isoluminant, or a full-color stimulus, the latter containing an additional achromatic component. Prior to the classification task, object discrimination thresholds were measured and stimuli were scaled to matching suprathreshold levels for each participant. In both experiments, behavioral performance was best for full-color stimuli and worst for S-cone isolating stimuli. Saccade rates 200–700 ms after stimulus onset were modulated independently by low and high-level factors, being higher for full-color stimuli than for S-cone isolating stimuli and higher for objects. Low-amplitude evoked GBA and total GBA were observed in very few conditions, showing that paradigms with isoluminant stimuli may not be ideal for eliciting such responses. We conclude that cortical loops involved in the processing of objects are preferentially excited by stimuli that contain achromatic information. Their activation can lead to relatively early exploratory eye movements even for foveally-presented stimuli. PMID:24391611

Ca2+ and frequency dependence of exocytosis in isolated somata of magnocellular supraoptic neurones of the rat hypothalamus

PubMed Central

Soldo, Brandi L; Giovannucci, David R; Stuenkel, Edward L; Moises, Hylan C

2004-01-01

In addition to action potential-evoked exocytotic release at neurohypophysial nerve terminals, the neurohormones arginine vasopressin (aVP) and oxytocin (OT) undergo Ca2+-dependent somatodendritic release within the supraoptic and paraventricular hypothalamic nuclei. However, the cellular and molecular mechanisms that underlie this release have not been elucidated. In the present study, the whole-cell patch-clamp technique was utilized in combination with high-time-resolved measurements of membrane capacitance (Cm) and microfluorometric measurements of cytosolic free Ca2+ concentration ([Ca2+]i) to examine the Ca2+ and stimulus dependence of exocytosis in the somata of magnocellular neurosecretory cells (MNCs) isolated from rat supraoptic nucleus (SON). Single depolarizing steps (≥20 ms) that evoked high-voltage-activated (HVA) Ca2+ currents (ICa) and elevations in intracellular Ca2+ concentration were accompanied by an increase in Cm in a majority (40/47) of SON neurones. The Cm responses were composed of an initial Ca2+-independent, transient component and a subsequent, sustained phase of increased Cm (termed ΔCm) mediated by an influx of Ca2+, and increased with corresponding prolongation of depolarizing step durations (20–200 ms). From this relationship we estimated the rate of vesicular release to be 1533 vesicles s−1. Delivery of neurone-derived action potential waveforms (APWs) as stimulus templates elicited ICa and also induced a ΔCm, provided APWs were applied in trains of greater than 13 Hz. A train of APWs modelled after the bursting pattern recorded from an OT-containing neurone during the milk ejection reflex was effective in supporting an exocytotic ΔCm in isolated MNCs, indicating that the somata of SON neurones respond to physiological patterns of neuronal activity with Ca2+-dependent exocytotic activity. PMID:14645448

Extracellular voltage threshold settings can be tuned for optimal encoding of movement and stimulus parameters

NASA Astrophysics Data System (ADS)

Oby, Emily R.; Perel, Sagi; Sadtler, Patrick T.; Ruff, Douglas A.; Mischel, Jessica L.; Montez, David F.; Cohen, Marlene R.; Batista, Aaron P.; Chase, Steven M.

2016-06-01

Objective. A traditional goal of neural recording with extracellular electrodes is to isolate action potential waveforms of an individual neuron. Recently, in brain-computer interfaces (BCIs), it has been recognized that threshold crossing events of the voltage waveform also convey rich information. To date, the threshold for detecting threshold crossings has been selected to preserve single-neuron isolation. However, the optimal threshold for single-neuron identification is not necessarily the optimal threshold for information extraction. Here we introduce a procedure to determine the best threshold for extracting information from extracellular recordings. We apply this procedure in two distinct contexts: the encoding of kinematic parameters from neural activity in primary motor cortex (M1), and visual stimulus parameters from neural activity in primary visual cortex (V1). Approach. We record extracellularly from multi-electrode arrays implanted in M1 or V1 in monkeys. Then, we systematically sweep the voltage detection threshold and quantify the information conveyed by the corresponding threshold crossings. Main Results. The optimal threshold depends on the desired information. In M1, velocity is optimally encoded at higher thresholds than speed; in both cases the optimal thresholds are lower than are typically used in BCI applications. In V1, information about the orientation of a visual stimulus is optimally encoded at higher thresholds than is visual contrast. A conceptual model explains these results as a consequence of cortical topography. Significance. How neural signals are processed impacts the information that can be extracted from them. Both the type and quality of information contained in threshold crossings depend on the threshold setting. There is more information available in these signals than is typically extracted. Adjusting the detection threshold to the parameter of interest in a BCI context should improve our ability to decode motor intent, and thus enhance BCI control. Further, by sweeping the detection threshold, one can gain insights into the topographic organization of the nearby neural tissue.

Extracellular voltage threshold settings can be tuned for optimal encoding of movement and stimulus parameters

PubMed Central

Oby, Emily R; Perel, Sagi; Sadtler, Patrick T; Ruff, Douglas A; Mischel, Jessica L; Montez, David F; Cohen, Marlene R; Batista, Aaron P; Chase, Steven M

2018-01-01

Objective A traditional goal of neural recording with extracellular electrodes is to isolate action potential waveforms of an individual neuron. Recently, in brain–computer interfaces (BCIs), it has been recognized that threshold crossing events of the voltage waveform also convey rich information. To date, the threshold for detecting threshold crossings has been selected to preserve single-neuron isolation. However, the optimal threshold for single-neuron identification is not necessarily the optimal threshold for information extraction. Here we introduce a procedure to determine the best threshold for extracting information from extracellular recordings. We apply this procedure in two distinct contexts: the encoding of kinematic parameters from neural activity in primary motor cortex (M1), and visual stimulus parameters from neural activity in primary visual cortex (V1). Approach We record extracellularly from multi-electrode arrays implanted in M1 or V1 in monkeys. Then, we systematically sweep the voltage detection threshold and quantify the information conveyed by the corresponding threshold crossings. Main Results The optimal threshold depends on the desired information. In M1, velocity is optimally encoded at higher thresholds than speed; in both cases the optimal thresholds are lower than are typically used in BCI applications. In V1, information about the orientation of a visual stimulus is optimally encoded at higher thresholds than is visual contrast. A conceptual model explains these results as a consequence of cortical topography. Significance How neural signals are processed impacts the information that can be extracted from them. Both the type and quality of information contained in threshold crossings depend on the threshold setting. There is more information available in these signals than is typically extracted. Adjusting the detection threshold to the parameter of interest in a BCI context should improve our ability to decode motor intent, and thus enhance BCI control. Further, by sweeping the detection threshold, one can gain insights into the topographic organization of the nearby neural tissue. PMID:27097901

Extracellular voltage threshold settings can be tuned for optimal encoding of movement and stimulus parameters.

PubMed

Oby, Emily R; Perel, Sagi; Sadtler, Patrick T; Ruff, Douglas A; Mischel, Jessica L; Montez, David F; Cohen, Marlene R; Batista, Aaron P; Chase, Steven M

2016-06-01

A traditional goal of neural recording with extracellular electrodes is to isolate action potential waveforms of an individual neuron. Recently, in brain-computer interfaces (BCIs), it has been recognized that threshold crossing events of the voltage waveform also convey rich information. To date, the threshold for detecting threshold crossings has been selected to preserve single-neuron isolation. However, the optimal threshold for single-neuron identification is not necessarily the optimal threshold for information extraction. Here we introduce a procedure to determine the best threshold for extracting information from extracellular recordings. We apply this procedure in two distinct contexts: the encoding of kinematic parameters from neural activity in primary motor cortex (M1), and visual stimulus parameters from neural activity in primary visual cortex (V1). We record extracellularly from multi-electrode arrays implanted in M1 or V1 in monkeys. Then, we systematically sweep the voltage detection threshold and quantify the information conveyed by the corresponding threshold crossings. The optimal threshold depends on the desired information. In M1, velocity is optimally encoded at higher thresholds than speed; in both cases the optimal thresholds are lower than are typically used in BCI applications. In V1, information about the orientation of a visual stimulus is optimally encoded at higher thresholds than is visual contrast. A conceptual model explains these results as a consequence of cortical topography. How neural signals are processed impacts the information that can be extracted from them. Both the type and quality of information contained in threshold crossings depend on the threshold setting. There is more information available in these signals than is typically extracted. Adjusting the detection threshold to the parameter of interest in a BCI context should improve our ability to decode motor intent, and thus enhance BCI control. Further, by sweeping the detection threshold, one can gain insights into the topographic organization of the nearby neural tissue.

Genome sequences of Salmonella enterica subsp. Kentucky ST152 isolated from dairy cows in the United States

USDA-ARS?s Scientific Manuscript database

Salmonella enterica subsp. enterica serovar Kentucky is frequently isolated from dairy cows in the United States, but is an infrequent cause of human salmonellosis. To investigate the genomic features of S. Kentucky strains isolated from these animals, genomes of eight isolates were sequenced and ad...

Analysis of compound action potentials elicited with specific current stimulating pulses in an isolated rat sciatic nerve.

PubMed

Žužek, Monika C; Rozman, Janez; Pečlin, Polona; Vrecl, Milka; Frangež, Robert

2017-02-01

The ability to selectively stimulate Aα, Aβ-fibers and Aδ-fibers in an isolated rat sciatic nerve (SNR) was assessed. The stimulus used was a current, biphasic pulse with a quasitrapezoidal cathodic phase and rectangular anodic phase where parameters were systematically varied: intensity of the cathodic phase (ic); width of the cathodic phase (tc); width of the cathodic exponential decay (texp) and time constant of the exponential decay (τexp). A SNR was stimulated using a pair of hook electrodes while conduction velocity (CV) and compound action potentials (CAP) were measured at two sites along the SNR using another two pairs of electrodes. Results showed that the highest CAP1 (8.5-9 mV), shall be expected when parameters of the stimulus were within the following range: ic=3.8-4 mA, tc=350-400 μs and texp=330-440 μs. Results also showed that with ascending tc and texp, CV of the corresponding superficial region of the SNR was reduced in both, conduction velocity of CAP1 and conduction velocity of CAP2. It was concluded that action potentials (APs) were activated in the Aβ-fibers and Aδ-fibers along with a slight AP inhibition in the Aβ-fibers. The obtained results, could serve as a tool for developing multi-electrode systems that potentially enable fiber-type selective stimulation of nerve fibers.

Application of HB17, an Arabidopsis class II homeodomain-leucine zipper transcription factor, to regulate chloroplast number and photosynthetic capacity.

PubMed

Hymus, Graham J; Cai, Suqin; Kohl, Elizabeth A; Holtan, Hans E; Marion, Colleen M; Tiwari, Shiv; Maszle, Don R; Lundgren, Marjorie R; Hong, Melissa C; Channa, Namitha; Loida, Paul; Thompson, Rebecca; Taylor, J Philip; Rice, Elena; Repetti, Peter P; Ratcliffe, Oliver J; Reuber, T Lynne; Creelman, Robert A

2013-11-01

Transcription factors are proposed as suitable targets for the control of traits such as yield or food quality in plants. This study reports the results of a functional genomics research effort that identified ATHB17, a transcription factor from the homeodomain-leucine zipper class II family, as a novel target for the enhancement of photosynthetic capacity. It was shown that ATHB17 is expressed natively in the root quiescent centre (QC) from Arabidopsis embryos and seedlings. Analysis of the functional composition of genes differentially expressed in the QC from a knockout mutant (athb17-1) compared with its wild-type sibling revealed the over-representation of genes involved in auxin stimulus, embryo development, axis polarity specification, and plastid-related processes. While no other phenotypes were observed in athb17-1 plants, overexpression of ATHB17 produced a number of phenotypes in Arabidopsis including enhanced chlorophyll content. Image analysis of isolated mesophyll cells of 35S::ATHB17 lines revealed an increase in the number of chloroplasts per unit cell size, which is probably due to an increase in the number of proplastids per meristematic cell. Leaf physiological measurements provided evidence of improved photosynthetic capacity in 35S::ATHB17 lines on a per unit leaf area basis. Estimates of the capacity for ribulose-1,5-bisphosphate-saturated and -limited photosynthesis were significantly higher in 35S::ATHB17 lines.

Application of HB17, an Arabidopsis class II homeodomain-leucine zipper transcription factor, to regulate chloroplast number and photosynthetic capacity

PubMed Central

Kohl, Elizabeth A.; Tiwari, Shiv; Lundgren, Marjorie R.; Channa, Namitha; Creelman, Robert A.

2013-01-01

Transcription factors are proposed as suitable targets for the control of traits such as yield or food quality in plants. This study reports the results of a functional genomics research effort that identified ATHB17, a transcription factor from the homeodomain-leucine zipper class II family, as a novel target for the enhancement of photosynthetic capacity. It was shown that ATHB17 is expressed natively in the root quiescent centre (QC) from Arabidopsis embryos and seedlings. Analysis of the functional composition of genes differentially expressed in the QC from a knockout mutant (athb17-1) compared with its wild-type sibling revealed the over-representation of genes involved in auxin stimulus, embryo development, axis polarity specification, and plastid-related processes. While no other phenotypes were observed in athb17-1 plants, overexpression of ATHB17 produced a number of phenotypes in Arabidopsis including enhanced chlorophyll content. Image analysis of isolated mesophyll cells of 35S::ATHB17 lines revealed an increase in the number of chloroplasts per unit cell size, which is probably due to an increase in the number of proplastids per meristematic cell. Leaf physiological measurements provided evidence of improved photosynthetic capacity in 35S::ATHB17 lines on a per unit leaf area basis. Estimates of the capacity for ribulose-1,5-bisphosphate-saturated and -limited photosynthesis were significantly higher in 35S::ATHB17 lines. PMID:24006420

Probability matching in perceptrons: Effects of conditional dependence and linear nonseparability.

PubMed

Dawson, Michael R W; Gupta, Maya

2017-01-01

Probability matching occurs when the behavior of an agent matches the likelihood of occurrence of events in the agent's environment. For instance, when artificial neural networks match probability, the activity in their output unit equals the past probability of reward in the presence of a stimulus. Our previous research demonstrated that simple artificial neural networks (perceptrons, which consist of a set of input units directly connected to a single output unit) learn to match probability when presented different cues in isolation. The current paper extends this research by showing that perceptrons can match probabilities when presented simultaneous cues, with each cue signaling different reward likelihoods. In our first simulation, we presented up to four different cues simultaneously; the likelihood of reward signaled by the presence of one cue was independent of the likelihood of reward signaled by other cues. Perceptrons learned to match reward probabilities by treating each cue as an independent source of information about the likelihood of reward. In a second simulation, we violated the independence between cues by making some reward probabilities depend upon cue interactions. We did so by basing reward probabilities on a logical combination (AND or XOR) of two of the four possible cues. We also varied the size of the reward associated with the logical combination. We discovered that this latter manipulation was a much better predictor of perceptron performance than was the logical structure of the interaction between cues. This indicates that when perceptrons learn to match probabilities, they do so by assuming that each signal of a reward is independent of any other; the best predictor of perceptron performance is a quantitative measure of the independence of these input signals, and not the logical structure of the problem being learned.

Probability matching in perceptrons: Effects of conditional dependence and linear nonseparability

PubMed Central

2017-01-01

Probability matching occurs when the behavior of an agent matches the likelihood of occurrence of events in the agent’s environment. For instance, when artificial neural networks match probability, the activity in their output unit equals the past probability of reward in the presence of a stimulus. Our previous research demonstrated that simple artificial neural networks (perceptrons, which consist of a set of input units directly connected to a single output unit) learn to match probability when presented different cues in isolation. The current paper extends this research by showing that perceptrons can match probabilities when presented simultaneous cues, with each cue signaling different reward likelihoods. In our first simulation, we presented up to four different cues simultaneously; the likelihood of reward signaled by the presence of one cue was independent of the likelihood of reward signaled by other cues. Perceptrons learned to match reward probabilities by treating each cue as an independent source of information about the likelihood of reward. In a second simulation, we violated the independence between cues by making some reward probabilities depend upon cue interactions. We did so by basing reward probabilities on a logical combination (AND or XOR) of two of the four possible cues. We also varied the size of the reward associated with the logical combination. We discovered that this latter manipulation was a much better predictor of perceptron performance than was the logical structure of the interaction between cues. This indicates that when perceptrons learn to match probabilities, they do so by assuming that each signal of a reward is independent of any other; the best predictor of perceptron performance is a quantitative measure of the independence of these input signals, and not the logical structure of the problem being learned. PMID:28212422

Comparison of UV C light and chemicals for disinfection of surfaces in hospital isolation units.

PubMed

Andersen, B M; Bånrud, H; Bøe, E; Bjordal, O; Drangsholt, F

2006-07-01

To determine the bactericidal effect on surfaces of ceiling- and wall-mounted UV C (UVC) light (wavelength, 254 nm) in isolation units, compared with standard hospital environmental cleaning and chemical disinfection during final disinfection after patients are treated for infections. Microbial samples were obtained from surfaces in isolation units (patient room, anteroom, and bathroom) before and after irradiation with UVC, chloramine disinfection, and standard hospital environmental cleaning. Samples were tested using standard contact plates. Four identical, negative air-pressure isolation units (patient room, anteroom, and bathroom) with a defined number of ceiling- and wall-mounted UVC light units. The UVC distribution was monitored in one isolation unit after irradiation for approximately 40 minutes, corresponding to doses ranging from 160 J/m2 in a shadowed area to 19,230 J/m2 at the mostly highly exposed site (which is high enough to inactivate most bacterial organisms, including spores). UVC disinfection significantly reduced the number of bacteria on surfaces directly or indirectly exposed to UVC to a very low number, as did 5% chloramine disinfection alone (P<.001 for both). Completely shadowed areas in the isolation unit (eg, the bed rail, lockers, and mattresses) still required disinfection by chemicals. Disinfection with UVC light may significantly reduce environmental bacterial contamination and thereby protect the next patient housed in an isolation room. UVC disinfection may not be used alone but is a good addition to chemical disinfection.

Neural Correlates and Mechanisms of Spatial Release From Masking: Single-Unit and Population Responses in the Inferior Colliculus

PubMed Central

Lane, Courtney C.; Delgutte, Bertrand

2007-01-01

Spatial release from masking (SRM), a factor in listening in noisy environments, is the improvement in auditory signal detection obtained when a signal is separated in space from a masker. To study the neural mechanisms of SRM, we recorded from single units in the inferior colliculus (IC) of barbiturate-anesthetized cats, focusing on low-frequency neurons sensitive to interaural time differences. The stimulus was a broadband chirp train with a 40-Hz repetition rate in continuous broadband noise, and the unit responses were measured for several signal and masker (virtual) locations. Masked thresholds (the lowest signal-to-noise ratio, SNR, for which the signal could be detected for 75% of the stimulus presentations) changed systematically with signal and masker location. Single-unit thresholds did not necessarily improve with signal and masker separation; instead, they tended to reflect the units’ azimuth preference. Both how the signal was detected (through a rate increase or decrease) and how the noise masked the signal response (suppressive or excitatory masking) changed with signal and masker azimuth, consistent with a cross-correlator model of binaural processing. However, additional processing, perhaps related to the signal’s amplitude modulation rate, appeared to influence the units’ responses. The population masked thresholds (the most sensitive unit’s threshold at each signal and masker location) did improve with signal and masker separation as a result of the variety of azimuth preferences in our unit sample. The population thresholds were similar to human behavioral thresholds in both SNR value and shape, indicating that these units may provide a neural substrate for low-frequency SRM. PMID:15857966

Stimulus Dependence of Correlated Variability across Cortical Areas

PubMed Central

Cohen, Marlene R.

2016-01-01

The way that correlated trial-to-trial variability between pairs of neurons in the same brain area (termed spike count or noise correlation, rSC) depends on stimulus or task conditions can constrain models of cortical circuits and of the computations performed by networks of neurons (Cohen and Kohn, 2011). In visual cortex, rSC tends not to depend on stimulus properties (Kohn and Smith, 2005; Huang and Lisberger, 2009) but does depend on cognitive factors like visual attention (Cohen and Maunsell, 2009; Mitchell et al., 2009). However, neurons across visual areas respond to any visual stimulus or contribute to any perceptual decision, and the way that information from multiple areas is combined to guide perception is unknown. To gain insight into these issues, we recorded simultaneously from neurons in two areas of visual cortex (primary visual cortex, V1, and the middle temporal area, MT) while rhesus monkeys viewed different visual stimuli in different attention conditions. We found that correlations between neurons in different areas depend on stimulus and attention conditions in very different ways than do correlations within an area. Correlations across, but not within, areas depend on stimulus direction and the presence of a second stimulus, and attention has opposite effects on correlations within and across areas. This observed pattern of cross-area correlations is predicted by a normalization model where MT units sum V1 inputs that are passed through a divisive nonlinearity. Together, our results provide insight into how neurons in different areas interact and constrain models of the neural computations performed across cortical areas. SIGNIFICANCE STATEMENT Correlations in the responses of pairs of neurons within the same cortical area have been a subject of growing interest in systems neuroscience. However, correlated variability between different cortical areas is likely just as important. We recorded simultaneously from neurons in primary visual cortex and the middle temporal area while rhesus monkeys viewed different visual stimuli in different attention conditions. We found that correlations between neurons in different areas depend on stimulus and attention conditions in very different ways than do correlations within an area. The observed pattern of cross-area correlations was predicted by a simple normalization model. Our results provide insight into how neurons in different areas interact and constrain models of the neural computations performed across cortical areas. PMID:27413163

Identification of Plasmid-Mediated Quinolone Resistance in Salmonella Isolated from Swine Ceca and Retail Pork Chops in the United States.

PubMed

Tyson, Gregory H; Tate, Heather P; Zhao, Shaohua; Li, Cong; Dessai, Uday; Simmons, Mustafa; McDermott, Patrick F

2017-10-01

Fluoroquinolones are important antimicrobial drugs used to treat human Salmonella infections, and resistance is rare in the United States for isolates from human and animal sources. Recently, a number of Salmonella isolates from swine cecal contents and retail pork products from National Antimicrobial Resistance Monitoring System (NARMS) surveillance exhibited decreased susceptibility to ciprofloxacin. We identified two qnrB19 quinolone resistance plasmids that are predominantly responsible for this phenomenon and found them distributed among several Salmonella serotypes isolated throughout the United States.

Sensory Prioritization in Rats: Behavioral Performance and Neuronal Correlates.

PubMed

Lee, Conrad C Y; Diamond, Mathew E; Arabzadeh, Ehsan

2016-03-16

Operating with some finite quantity of processing resources, an animal would benefit from prioritizing the sensory modality expected to provide key information in a particular context. The present study investigated whether rats dedicate attentional resources to the sensory modality in which a near-threshold event is more likely to occur. We manipulated attention by controlling the likelihood with which a stimulus was presented from one of two modalities. In a whisker session, 80% of trials contained a brief vibration stimulus applied to whiskers and the remaining 20% of trials contained a brief change of luminance. These likelihoods were reversed in a visual session. When a stimulus was presented in the high-likelihood context, detection performance increased and was faster compared with the same stimulus presented in the low-likelihood context. Sensory prioritization was also reflected in neuronal activity in the vibrissal area of primary somatosensory cortex: single units responded differentially to the whisker vibration stimulus when presented with higher probability compared with lower probability. Neuronal activity in the vibrissal cortex displayed signatures of multiplicative gain control and enhanced response to vibration stimuli during the whisker session. In conclusion, rats allocate priority to the more likely stimulus modality and the primary sensory cortex may participate in the redistribution of resources. Detection of low-amplitude events is critical to survival; for example, to warn prey of predators. To formulate a response, decision-making systems must extract minute neuronal signals from the sensory modality that provides key information. Here, we identify the behavioral and neuronal correlates of sensory prioritization in rats. Rats were trained to detect whisker vibrations or visual flickers. Stimuli were embedded in two contexts in which either visual or whisker modality was more likely to occur. When a stimulus was presented in the high-likelihood context, detection was faster and more reliable. Neuronal recording from the vibrissal cortex revealed enhanced representation of vibrations in the prioritized context. These results establish the rat as an alternative model organism to primates for studying attention. Copyright © 2016 the authors 0270-6474/16/363243-11$15.00/0.

Shapers of Southern History: Autobiographical Reflections

ERIC Educational Resources Information Center

Badger, Tony

2006-01-01

A British historian of the American South examines the forces of contingency and the stimulus of teaching that led him to become a historian of the United States and, in particular, the American South. Belonging to a generation of British historians who aimed to make their work indistinguishable from their American counterparts, he has been forced…

Improving Accuracy of Portion-Size Estimations through a Stimulus Equivalence Paradigm

ERIC Educational Resources Information Center

Hausman, Nicole L.; Borrero, John C.; Fisher, Alyssa; Kahng, SungWoo

2014-01-01

The prevalence of obesity continues to increase in the United States (Gordon-Larsen, The, & Adair, 2010). Obesity can be attributed, in part, to overconsumption of energy-dense foods. Given that overeating plays a role in the development of obesity, interventions that teach individuals to identify and consume appropriate portion sizes are…

Joint Space Doctrine: Catapulting into the Future

DTIC Science & Technology

1994-01-01

Information dominance will provide the stimulus for the military space program in the near term. Maximizing the capabilities of the information weapon, however, requires formulating joint space doctrine that has broad support and applicability. This doctrine will provide a significant advantage for the United States over those nations which employ space assets in a piecemeal

Second-Order Schedules of Token Reinforcement with Pigeons: Implications for Unit Price

ERIC Educational Resources Information Center

Bullock, Christopher E.; Hackenberg, Timothy D.

2006-01-01

Four pigeons were exposed to second-order schedules of token reinforcement, with stimulus lights serving as token reinforcers. Tokens were earned according to a fixed-ratio (token-production) schedule, with the opportunity to exchange tokens for food (exchange period) occurring after a fixed number had been produced (exchange-production ratio).…

International and National Environmental Education: A Status Report - 1974.

ERIC Educational Resources Information Center

Roth, Robert E.

This report focuses on the current status of environmental education in the U.S. and a number of selected countries around the world. The scope and primary concerns of environmental education are defined, and the stimulus created by the United Nations Stockholm Conference on the Human Environment is discussed. On the international scene…

A simple handheld pupillometer for chromatic Flicker studies

NASA Astrophysics Data System (ADS)

Bernabei, M.; Tinarelli, R.; Peretto, L.; Rovati, L.

2014-02-01

A portable pupillometer has been developed which is capable of performing accurate measurements of the pupil diameter during chromatic flicker stimulations. The handheld measuring system records the near-infrared image of the pupil at the rate of 25 fps and simultaneously stimulates the eye using a diffused flicker light generated by light emitting diodes (LEDs). Intensity, frequency and chromatic coordinates of the stimulus can be easily adjusted using a user-friendly graphical interface. Thanks to a chromatic monitoring of the stimulus close to the plane of the eye, photopically matched conditions can be easily achieved. The pupil diameter/area can be measured during flickering stimuli that are generated with frequency in a range of 0.1-20 Hz. The electronic unit, properly connected to the personal computer through a USB port, drives the optical unit, which can be easily held in a hand. The software interface controlling the system was developed in LabVIEW. This paper describes the instrument optical setup, front-end electronics and data processing. Moreover preliminary results obtained on a voluntary are reported.

The Neuropeptide Tac2 Controls a Distributed Brain State Induced by Chronic Social Isolation Stress.

PubMed

Zelikowsky, Moriel; Hui, May; Karigo, Tomomi; Choe, Andrea; Yang, Bin; Blanco, Mario R; Beadle, Keith; Gradinaru, Viviana; Deverman, Benjamin E; Anderson, David J

2018-05-17

Chronic social isolation causes severe psychological effects in humans, but their neural bases remain poorly understood. 2 weeks (but not 24 hr) of social isolation stress (SIS) caused multiple behavioral changes in mice and induced brain-wide upregulation of the neuropeptide tachykinin 2 (Tac2)/neurokinin B (NkB). Systemic administration of an Nk3R antagonist prevented virtually all of the behavioral effects of chronic SIS. Conversely, enhancing NkB expression and release phenocopied SIS in group-housed mice, promoting aggression and converting stimulus-locked defensive behaviors to persistent responses. Multiplexed analysis of Tac2/NkB function in multiple brain areas revealed dissociable, region-specific requirements for both the peptide and its receptor in different SIS-induced behavioral changes. Thus, Tac2 coordinates a pleiotropic brain state caused by SIS via a distributed mode of action. These data reveal the profound effects of prolonged social isolation on brain chemistry and function and suggest potential new therapeutic applications for Nk3R antagonists. Copyright © 2018 Elsevier Inc. All rights reserved.

Implicit Value Updating Explains Transitive Inference Performance: The Betasort Model

PubMed Central

Jensen, Greg; Muñoz, Fabian; Alkan, Yelda; Ferrera, Vincent P.; Terrace, Herbert S.

2015-01-01

Transitive inference (the ability to infer that B > D given that B > C and C > D) is a widespread characteristic of serial learning, observed in dozens of species. Despite these robust behavioral effects, reinforcement learning models reliant on reward prediction error or associative strength routinely fail to perform these inferences. We propose an algorithm called betasort, inspired by cognitive processes, which performs transitive inference at low computational cost. This is accomplished by (1) representing stimulus positions along a unit span using beta distributions, (2) treating positive and negative feedback asymmetrically, and (3) updating the position of every stimulus during every trial, whether that stimulus was visible or not. Performance was compared for rhesus macaques, humans, and the betasort algorithm, as well as Q-learning, an established reward-prediction error (RPE) model. Of these, only Q-learning failed to respond above chance during critical test trials. Betasort’s success (when compared to RPE models) and its computational efficiency (when compared to full Markov decision process implementations) suggests that the study of reinforcement learning in organisms will be best served by a feature-driven approach to comparing formal models. PMID:26407227

Implicit Value Updating Explains Transitive Inference Performance: The Betasort Model.

PubMed

Jensen, Greg; Muñoz, Fabian; Alkan, Yelda; Ferrera, Vincent P; Terrace, Herbert S

2015-01-01

Transitive inference (the ability to infer that B > D given that B > C and C > D) is a widespread characteristic of serial learning, observed in dozens of species. Despite these robust behavioral effects, reinforcement learning models reliant on reward prediction error or associative strength routinely fail to perform these inferences. We propose an algorithm called betasort, inspired by cognitive processes, which performs transitive inference at low computational cost. This is accomplished by (1) representing stimulus positions along a unit span using beta distributions, (2) treating positive and negative feedback asymmetrically, and (3) updating the position of every stimulus during every trial, whether that stimulus was visible or not. Performance was compared for rhesus macaques, humans, and the betasort algorithm, as well as Q-learning, an established reward-prediction error (RPE) model. Of these, only Q-learning failed to respond above chance during critical test trials. Betasort's success (when compared to RPE models) and its computational efficiency (when compared to full Markov decision process implementations) suggests that the study of reinforcement learning in organisms will be best served by a feature-driven approach to comparing formal models.

A survey of dermatophytes isolated from human patients in the United States from 1979 to 1981 with chronological listings of worldwide incidence of five dermatophytes often isolated in the United States.

PubMed

Sinski, J T; Flouras, K

1984-03-15

A survey of dermatophytes isolated from patients seeking medical advice was made from 1979 to 1981 in the United States. The survey included 54 locations with data from 40 cities and 2 states. Correlations of these data with that of the other localities of the world were made to illustrate the dynamic epidemiology of several common dermatophytes. The most often isolated dermatophyte in this survey was Trichophyton rubrum having 53.66% of the total for these three calendar years. In a chronological listing of ringworm infections caused by this organism, many areas of the world have reported similar increased incidence of this pathogen. Trichophyton tonsurans was isolated 27.85% of the total. A dramatic increase of this pathogen as a cause of tinea capitis has been observed in most cities of the United States. It has been isolated in 25 different countries of the world. The percentage of isolation of Trichophyton mentagrophytes was 8.56%. This percentage may not be near the true incidence of infection by this dermatophyte because the infections are mild and respond to treatment without the individual seeking medical advice. Since the 1950s the percentage of isolations of the total has dropped for T. mentagrophytes in the United States. Epidermophyton floccosum accounted for 4.36% of the total. In a few areas of the world it causes over 30% of the total of dermatophytoses. Microsporum canis was isolated 3.72% of the total in the United States. It has recently been reported to be the dominant agent of tinea capitis in several South American countries, Tucson, Arizona and Kuwait. Once the dominant pathogen of tinea capitis in children in the United States, it was replaced by Microsporum audouinii before 1960. Today in the United States, M. audouinii only accounts for 0.30% of the total. It is considered eliminated as a pathogen in England. In this survey, isolated less than 1.0% of the total were Microsporum gypseum. Microsporum ferrugineum , Microsporum nanum , Microsporum fulvum and Trichophyton schoenleinii . Trichophyton meginii and Trichophyton terrestre were reported isolated but no numerical data were available.

Metastable neural dynamics mediates expectation

NASA Astrophysics Data System (ADS)

Mazzucato, Luca; La Camera, Giancarlo; Fontanini, Alfredo

Sensory stimuli are processed faster when their presentation is expected compared to when they come as a surprise. We previously showed that, in multiple single-unit recordings from alert rat gustatory cortex, taste stimuli can be decoded faster from neural activity if preceded by a stimulus-predicting cue. However, the specific computational process mediating this anticipatory neural activity is unknown. Here, we propose a biologically plausible model based on a recurrent network of spiking neurons with clustered architecture. In the absence of stimulation, the model neural activity unfolds through sequences of metastable states, each state being a population vector of firing rates. We modeled taste stimuli and cue (the same for all stimuli) as two inputs targeting subsets of excitatory neurons. As observed in experiment, stimuli evoked specific state sequences, characterized in terms of `coding states', i.e., states occurring significantly more often for a particular stimulus. When stimulus presentation is preceded by a cue, coding states show a faster and more reliable onset, and expected stimuli can be decoded more quickly than unexpected ones. This anticipatory effect is unrelated to changes of firing rates in stimulus-selective neurons and is absent in homogeneous balanced networks, suggesting that a clustered organization is necessary to mediate the expectation of relevant events. Our results demonstrate a novel mechanism for speeding up sensory coding in cortical circuits. NIDCD K25-DC013557 (LM); NIDCD R01-DC010389 (AF); NSF IIS-1161852 (GL).

Possible stimuli for strength and power adaptation : acute metabolic responses.

PubMed

Crewther, Blair; Cronin, John; Keogh, Justin

2006-01-01

The metabolic response to resistance exercise, in particular lactic acid or lactate, has a marked influence upon the muscular environment, which may enhance the training stimulus (e.g. motor unit activation, hormones or muscle damage) and thereby contribute to strength and power adaptation. Hypertrophy schemes have resulted in greater lactate responses (%) than neuronal and dynamic power schemes, suggesting possible metabolic-mediated changes in muscle growth. Factors such as age, sex, training experience and nutrition may also influence the lactate responses to resistance exercise and thereafter, muscular adaptation. Although the importance of the mechanical and hormonal stimulus to strength and power adaptation is well recognised, the contribution of the metabolic stimulus is largely unknown. Relatively few studies for example, have examined metabolic change across neuronal and dynamic power schemes, and not withstanding the fact that those mechanisms underpinning muscular adaptation, in relation to the metabolic stimulus, remain highly speculative. Inconsistent findings and methodological limitations within research (e.g. programme design, sampling period, number of samples) make interpretation further difficult. We contend that strength and power research needs to investigate those metabolic mechanisms likely to contribute to weight-training adaptation. Further research is also needed to examine the metabolic responses to different loading schemes, as well as interactions across age, sex and training status, so our understanding of how to optimise strength and power development is improved.

Oscillatory encoding of visual stimulus familiarity.

PubMed

Kissinger, Samuel T; Pak, Alexandr; Tang, Yu; Masmanidis, Sotiris C; Chubykin, Alexander A

2018-06-18

Familiarity of the environment changes the way we perceive and encode incoming information. However, the neural substrates underlying this phenomenon are poorly understood. Here we describe a new form of experience-dependent low frequency oscillations in the primary visual cortex (V1) of awake adult male mice. The oscillations emerged in visually evoked potentials (VEPs) and single-unit activity following repeated visual stimulation. The oscillations were sensitive to the spatial frequency content of a visual stimulus and required the muscarinic acetylcholine receptors (mAChRs) for their induction and expression. Finally, ongoing visually evoked theta (4-6 Hz) oscillations boost the VEP amplitude of incoming visual stimuli if the stimuli are presented at the high excitability phase of the oscillations. Our results demonstrate that an oscillatory code can be used to encode familiarity and serves as a gate for oncoming sensory inputs. Significance Statement. Previous experience can influence the processing of incoming sensory information by the brain and alter perception. However, the mechanistic understanding of how this process takes place is lacking. We have discovered that persistent low frequency oscillations in the primary visual cortex encode information about familiarity and the spatial frequency of the stimulus. These familiarity evoked oscillations influence neuronal responses to the oncoming stimuli in a way that depends on the oscillation phase. Our work demonstrates a new mechanism of visual stimulus feature detection and learning. Copyright © 2018 the authors.

COMMUNICATION: Electrophysiological response dynamics during focal cortical infarction

NASA Astrophysics Data System (ADS)

Chiganos, Terry C., Jr.; Jensen, Winnie; Rousche, Patrick J.

2006-12-01

While the intracellular processes of hypoxia-induced necrosis and the intercellular mechanisms of post-ischemic neurotoxicity associated with stroke are well documented, the dynamic electrophysiological (EP) response of neurons within the core or periinfarct zone remains unclear. The present study validates a method for continuous measurement of the local EP responses during focal cortical infarction induced via photothrombosis. Single microwire electrodes were acutely implanted into the primary auditory cortex of eight rats. Multi-unit neural activity, evoked via a continuous 2 Hz click stimulus, was recorded before, during and after infarction to assess neuronal function in response to local, permanent ischemia. During sham infarction, the average stimulus-evoked peak firing rate over 20 min remained stable at 495.5 ± 14.5 spikes s-1, indicating temporal stability of neural function under normal conditions. Stimulus-evoked peak firing was reliably reduced to background levels (firing frequency in the absence of stimulus) following initiation of photothrombosis over a period of 439 ± 92 s. The post-infarction firing patterns exhibited unique temporal degradation of the peak firing rate, suggesting a variable response to ischemic challenge. Despite the inherent complexity of cerebral ischemia secondary to microvascular occlusion, complete loss of EP function consistently occurred 300-600 s after photothrombosis. The results suggest that microwire recording during photothrombosis provides a simple and highly efficacious strategy for assessing the electrophysiological dynamics of cortical infarction.

Comparison of apoptosis in human primary pulmonary endothelial cells and a brain microvascular endothelial cell line co-cultured with Plasmodium falciparum field isolates.

PubMed

Essone, Jean Claude Biteghe Bi; N'Dilimabaka, Nadine; Ondzaga, Julien; Lekana-Douki, Jean Bernard; Mba, Dieudonné Nkoghe; Deloron, Philippe; Mazier, Dominique; Gay, Frédrérick; Touré Ndouo, Fousseyni S

2017-06-27

Plasmodium falciparum infection can progress unpredictably to severe forms including respiratory distress and cerebral malaria. The mechanisms underlying the variable natural course of malaria remain elusive. The cerebral microvascular endothelial cells-D3 and lung endothelial cells both from human were cultured separately and challenged with P. falciparum field isolates taken directly from malaria patients or 3D7 strain (in vitro maintained culture). The capacity of these P. falciparum isolates to induce endothelial cell apoptosis via cytoadherence or not was then assessed. Overall, 27 P. falciparum isolates were collected from patients with uncomplicated malaria (n = 25) or severe malaria (n = 2). About half the isolates (n = 17) were able to bind brain endothelial cells (12 isolates, 44%) or lung endothelial cells (17 isolates, 63%) or both (12 isolates, 44%). Sixteen (59%) of the 27 isolates were apoptogenic for brain and/or lung endothelial cells. The apoptosis stimulus could be cytoadherence, direct cell-cell contact without cytoadherence, or diffusible soluble factors. While some of the apoptogenic isolates used two stimuli (direct contact with or without cytoadherence, plus soluble factors) to induce apoptosis, others used only one. Among the 16 apoptogenic isolates, eight specifically targeted brain endothelial cells, one lung endothelial cells, and seven both. These results indicate that the brain microvascular cell line was more susceptible to apoptosis triggered by P. falciparum than the primary pulmonary endothelial cells and may have relevance to host-parasite interaction.

Medial prefrontal cortex circuit function during retrieval and extinction of associative learning under anesthesia.

PubMed

Fenton, G E; Halliday, D M; Mason, R; Stevenson, C W

2014-04-18

Associative learning is encoded under anesthesia and involves the medial prefrontal cortex (mPFC). Neuronal activity in mPFC increases in response to a conditioned stimulus (CS+) previously paired with an unconditioned stimulus (US) but not during presentation of an unpaired stimulus (CS-) in anesthetized animals. Studies in conscious animals have shown dissociable roles for different mPFC subregions in mediating various memory processes, with the prelimbic (PL) and infralimbic (IL) cortex involved in the retrieval and extinction of conditioned responding, respectively. Therefore PL and IL may also play different roles in mediating the retrieval and extinction of discrimination learning under anesthesia. Here we used in vivo electrophysiology to examine unit and local field potential (LFP) activity in PL and IL before and after auditory discrimination learning and during later retrieval and extinction testing in anesthetized rats. Animals received repeated presentations of two distinct sounds, one of which was paired with footshock (US). In separate control experiments animals received footshocks without sounds. After discrimination learning the paired (CS+) and unpaired (CS-) sounds were repeatedly presented alone. We found increased unit firing and LFP power in PL and, to a lesser extent, IL after discrimination learning but not after footshocks alone. After discrimination learning, unit firing and LFP power increased in PL and IL in response to presentation of the first CS+, compared to the first CS-. However, PL and IL activity increased during the last CS- presentation, such that activity during presentation of the last CS+ and CS- did not differ. These results confirm previous findings and extend them by showing that increased PL and IL activity result from encoding of the CS+/US association rather than US presentation. They also suggest that extinction may occur under anesthesia and might be represented at the neural level in PL and IL. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

Enhancement of equivalence class formation by pretraining discriminative functions.

PubMed

Nartey, Richard K; Arntzen, Erik; Fields, Lanny

2015-03-01

The present experiment showed that a simple discriminative function acquired by an abstract stimulus through simultaneous and/or successive discrimination training enhanced the formation of an equivalence class of which that stimulus was a member. College students attempted to form three equivalence classes composed of three nodes and five members (A→B→C→D→E), using the simultaneous protocol. In the PIC group, the C stimuli were pictures and the A, B, D, and E stimuli were abstract shapes. In the ABS group, all of the stimuli were abstract shapes. In the SIM + SUCC (simultaneous and successive) group, simple discriminations were formed with the C stimuli through both simultaneous and successive discrimination training before class formation. Finally, in the SIM-only and SUCC-only groups, prior to class formation, simple discriminations were established for the C stimuli with a simultaneous procedure and a successive procedure, respectively. Equivalence classes were formed by 80% and 70% of the participants in the PIC and SIM + SUCC groups respectively, by 30% in the SUCC-only group, and by 10% apiece in the ABS and SIM-only groups. Thus, pretraining of combined simultaneous and successive discriminations enhanced class formation, as did the inclusion of a meaningful stimulus in a class. The isolated effect of forming successive discriminations was more influential than that of forming simultaneous discriminations. The establishment of both discriminations together produced an enhancement greater than the sum of the two procedures alone. Finally, a sorting test documented the maintenance of the classes formed during the simultaneous protocol. These results also provide a stimulus control-function account of the class-enhancing effects of meaningful stimuli.

Isolation of mesenchymal stromal/stem cells from cryopreserved umbilical cord blood cells.

PubMed

Fujii, Sumie; Miura, Yasuo; Iwasa, Masaki; Yoshioka, Satoshi; Fujishiro, Aya; Sugino, Noriko; Kaneko, Hitomi; Nakagawa, Yoko; Hirai, Hideyo; Takaori-Kondo, Akifumi; Ichinohe, Tatsuo; Maekawa, Taira

2017-07-05

Umbilical cord blood (UCB) has advantages over other tissues because it can be obtained without an invasive procedure and complex processing. We explored the availability of cryopreserved UCB cells as a source of mesenchymal stromal/stem cells (MSCs). MSCs were successfully isolated from six of 30 UCB units (median volume, 34.0 mL; median nucleated cell number, 4.4×10 8 ) that were processed and cryopreserved using CP-1/human serum albumin. This isolation rate was lower than that (57%) from non-cryopreserved UCB cells. The number of nucleated cells before and after hydroxyethyl starch separation, UCB unit volume, and cell viability after thawing did not significantly differ between UCB units from which MSCs were successfully isolated and those from which they were not. When CryoSure-DEX40 was used as a cryoprotectant, MSCs were isolated from two of ten UCB units. Logistic regression analysis demonstrated that the cryopreservation method was not significantly associated with the success of MSC isolation. The isolated MSCs had a similar morphology and surface marker expression profile as bone marrow-derived MSCs and were able to differentiate into osteogenic, adipogenic, and chondrogenic cells. In summary, MSCs can be isolated from cryopreserved UCB cells. However, the cryopreservation process reduces the isolation rate; therefore, freshly donated UCB cells are preferable for the isolation of MSCs.

Shape Selectivity of Middle Superior Temporal Sulcus Body Patch Neurons

PubMed Central

2017-01-01

Abstract Functional MRI studies in primates have demonstrated cortical regions that are strongly activated by visual images of bodies. The presence of such body patches in macaques allows characterization of the stimulus selectivity of their single neurons. Middle superior temporal sulcus body (MSB) patch neurons showed similar stimulus selectivity for natural, shaded, and textured images compared with their silhouettes, suggesting that shape is an important determinant of MSB responses. Here, we examined and modeled the shape selectivity of single MSB neurons. We measured the responses of single MSB neurons to a variety of shapes producing a wide range of responses. We used an adaptive stimulus sampling procedure, selecting and modifying shapes based on the responses of the neuron. Forty percent of shapes that produced the maximal response were rated by humans as animal-like, but the top shape of many MSB neurons was not judged as resembling a body. We fitted the shape selectivity of MSB neurons with a model that parameterizes shapes in terms of curvature and orientation of contour segments, with a pixel-based model, and with layers of units of convolutional neural networks (CNNs). The deep convolutional layers of CNNs provided the best goodness-of-fit, with a median explained explainable variance of the neurons’ responses of 77%. The goodness-of-fit increased along the convolutional layers’ hierarchy but was lower for the fully connected layers. Together with demonstrating the successful modeling of single unit shape selectivity with deep CNNs, the data suggest that semantic or category knowledge determines only slightly the single MSB neuron’s shape selectivity. PMID:28660250

Olfactory cortical adaptation facilitates detection of odors against background.

PubMed

Kadohisa, Mikiko; Wilson, Donald A

2006-03-01

Detection and discrimination of odors generally, if not always, occurs against an odorous background. On any given inhalation, olfactory receptor neurons will be activated by features of both the target odorant and features of background stimuli. To identify a target odorant against a background therefore, the olfactory system must be capable of grouping a subset of features into an odor object distinct from the background. Our previous work has suggested that rapid homosynaptic depression of afferents to the anterior piriform cortex (aPCX) contributes to both cortical odor adaptation to prolonged stimulation and habituation of simple odor-evoked behaviors. We hypothesize here that this process may also contribute to figure-ground separation of a target odorant from background stimulation. Single-unit recordings were made from both mitral/tufted cells and aPCX neurons in urethan-anesthetized rats and mice. Single-unit responses to odorant stimuli and their binary mixtures were determined. One of the odorants was randomly selected as the background and presented for 50 s. Forty seconds after the onset of the background stimulus, the second target odorant was presented, producing a binary mixture. The results suggest that mitral/tufted cells continue to respond to the background odorant and, when the target odorant is presented, had response magnitudes similar to that evoked by the binary mixture. In contrast, aPCX neurons filter out the background stimulus while maintaining responses to the target stimulus. Thus the aPCX acts as a filter driven most strongly by changing stimuli, providing a potential mechanism for olfactory figure-ground separation and selective reading of olfactory bulb output.

Recruitment order of quadriceps motor units: femoral nerve vs. direct quadriceps stimulation.

PubMed

Rodriguez-Falces, Javier; Place, Nicolas

2013-12-01

To investigate potential differences in the recruitment order of motor units (MUs) in the quadriceps femoris when electrical stimulation is applied over the quadriceps belly versus the femoral nerve. M-waves and mechanical twitches were evoked using femoral nerve stimulation and direct quadriceps stimulation of gradually increasing intensity from 20 young, healthy subjects. Recruitment order was investigated by analysing the time-to-peak twitch and the time interval from the stimulus artefact to the M-wave positive peak (M-wave latency) for the vastus medialis (VM) and vastus lateralis (VL) muscles. During femoral nerve stimulation, time-to-peak twitch and M-wave latency decreased consistently (P < 0.05) with increasing stimulus intensity, whereas, during graded direct quadriceps stimulation, time-to-peak twitch and VL M-wave latency did not show a clear trend (P > 0.05). For the VM muscle, M-wave latency decreased with increasing stimulation level for both femoral nerve and direct quadriceps stimulation, whereas, for the VL muscle, the variation of M-wave latency with stimulus intensity was different for the two stimulation geometries (P < 0.05). Femoral nerve stimulation activated MUs according to the size principle, whereas the recruitment order during direct quadriceps stimulation was more complex, depending ultimately on the architecture of the peripheral nerve and its terminal branches below the stimulating electrodes for each muscle. For the VM, MUs were orderly recruited for both stimulation geometries, whereas, for the VL muscle, MUs were orderly recruited for femoral nerve stimulation, but followed no particular order for direct quadriceps stimulation.

Identification of Plasmid-Mediated Quinolone Resistance in Salmonella Isolated from Swine Ceca and Retail Pork Chops in the United States

PubMed Central

Tate, Heather P.; Zhao, Shaohua; Li, Cong; Dessai, Uday; Simmons, Mustafa; McDermott, Patrick F.

2017-01-01

ABSTRACT Fluoroquinolones are important antimicrobial drugs used to treat human Salmonella infections, and resistance is rare in the United States for isolates from human and animal sources. Recently, a number of Salmonella isolates from swine cecal contents and retail pork products from National Antimicrobial Resistance Monitoring System (NARMS) surveillance exhibited decreased susceptibility to ciprofloxacin. We identified two qnrB19 quinolone resistance plasmids that are predominantly responsible for this phenomenon and found them distributed among several Salmonella serotypes isolated throughout the United States. PMID:28784677

Sensitivity to image recurrence across eye-movement-like image transitions through local serial inhibition in the retina

PubMed Central

Krishnamoorthy, Vidhyasankar; Weick, Michael; Gollisch, Tim

2017-01-01

Standard models of stimulus encoding in the retina postulate that image presentations activate neurons according to the increase of preferred contrast inside the receptive field. During natural vision, however, images do not arrive in isolation, but follow each other rapidly, separated by sudden gaze shifts. We here report that, contrary to standard models, specific ganglion cells in mouse retina are suppressed after a rapid image transition by changes in visual patterns across the transition, but respond with a distinct spike burst when the same pattern reappears. This sensitivity to image recurrence depends on opposing effects of glycinergic and GABAergic inhibition and can be explained by a circuit of local serial inhibition. Rapid image transitions thus trigger a mode of operation that differs from the processing of simpler stimuli and allows the retina to tag particular image parts or to detect transition types that lead to recurring stimulus patterns. DOI: http://dx.doi.org/10.7554/eLife.22431.001 PMID:28230526

Simulation of axonal excitability using a Spreadsheet template created in Microsoft Excel.

PubMed

Brown, A M

2000-08-01

The objective of this present study was to implement an established simulation protocol (A.M. Brown, A methodology for simulating biological systems using Microsoft Excel, Comp. Methods Prog. Biomed. 58 (1999) 181-90) to model axonal excitability. The simulation protocol involves the use of in-cell formulas directly typed into a spreadsheet and does not require any programming skills or use of the macro language. Once the initial spreadsheet template has been set up the simulations described in this paper can be executed with a few simple keystrokes. The model axon contained voltage-gated ion channels that were modeled using Hodgkin Huxley style kinetics. The basic properties of axonal excitability modeled were: (1) threshold of action potential firing, demonstrating that not only are the stimulus amplitude and duration critical in the generation of an action potential, but also the resting membrane potential; (2) refractoriness, the phenomenon of reduced excitability immediately following an action potential. The difference between the absolute refractory period, when no amount of stimulus will elicit an action potential, and relative refractory period, when an action potential may be generated by applying increased stimulus, was demonstrated with regard to the underlying state of the Na(+) and K(+) channels; (3) temporal summation, a process by which two sub-threshold stimuli can unite to elicit an action potential was shown to be due to conductance changes outlasting the first stimulus and summing with the second stimulus-induced conductance changes to drive the membrane potential past threshold; (4) anode break excitation, where membrane hyperpolarization was shown to produce an action potential by removing Na(+) channel inactivation that is present at resting membrane potential. The simulations described in this paper provide insights into mechanisms of axonal excitation that can be carried out by following an easily understood protocol.

Recent Visual Experience Shapes Visual Processing in Rats through Stimulus-Specific Adaptation and Response Enhancement.

PubMed

Vinken, Kasper; Vogels, Rufin; Op de Beeck, Hans

2017-03-20

From an ecological point of view, it is generally suggested that the main goal of vision in rats and mice is navigation and (aerial) predator evasion [1-3]. The latter requires fast and accurate detection of a change in the visual environment. An outstanding question is whether there are mechanisms in the rodent visual system that would support and facilitate visual change detection. An experimental protocol frequently used to investigate change detection in humans is the oddball paradigm, in which a rare, unexpected stimulus is presented in a train of stimulus repetitions [4]. A popular "predictive coding" theory of cortical responses states that neural responses should decrease for expected sensory input and increase for unexpected input [5, 6]. Despite evidence for response suppression and enhancement in noninvasive scalp recordings in humans with this paradigm [7, 8], it has proven challenging to observe both phenomena in invasive action potential recordings in other animals [9-11]. During a visual oddball experiment, we recorded multi-unit spiking activity in rat primary visual cortex (V1) and latero-intermediate area (LI), which is a higher area of the rodent ventral visual stream. In rat V1, there was only evidence for response suppression related to stimulus-specific adaptation, and not for response enhancement. However, higher up in area LI, spiking activity showed clear surprise-based response enhancement in addition to stimulus-specific adaptation. These results show that neural responses along the rat ventral visual stream become increasingly sensitive to changes in the visual environment, suggesting a system specialized in the detection of unexpected events. Copyright © 2017 Elsevier Ltd. All rights reserved.

Study of aggregative behavior of Rhinophrynus dorsalis tadpoles: design and analysis

USGS Publications Warehouse

Foster, M.S.; McDiarmid, R.W.

1982-01-01

We conducted experiments using the apparatus and design followed by Wassersug and Hessler (1971) and Wassersug (1973) to test the aggregative behavior of tadpoles of Rhinophrynus dorsalis in response to visual and olfactory stimuli. Results neither supported nor refuted the hypothesis that either stimulus is used as a mechanism for school formation. The exercise did lead to doubts about the experimental design. Some ambiguity resulted from the fact that the significance of the results depended upon the way in which the data were analyzed. Several alternative methods were considered. We also observed tadpoles reared in isolation to determine the effect of prior social conditioning on aggregative behavior. Isolates grew less than group-reared animals, were less active, and exhibited a strong avoidance reaction when subsequently exposed to conspecifics.

Multichannel activity propagation across an engineered axon network

NASA Astrophysics Data System (ADS)

Chen, H. Isaac; Wolf, John A.; Smith, Douglas H.

2017-04-01

Objective. Although substantial progress has been made in mapping the connections of the brain, less is known about how this organization translates into brain function. In particular, the massive interconnectivity of the brain has made it difficult to specifically examine data transmission between two nodes of the connectome, a central component of the ‘neural code.’ Here, we investigated the propagation of multiple streams of asynchronous neuronal activity across an isolated in vitro ‘connectome unit.’ Approach. We used the novel technique of axon stretch growth to create a model of a long-range cortico-cortical network, a modular system consisting of paired nodes of cortical neurons connected by axon tracts. Using optical stimulation and multi-electrode array recording techniques, we explored how input patterns are represented by cortical networks, how these representations shift as they are transmitted between cortical nodes and perturbed by external conditions, and how well the downstream node distinguishes different patterns. Main results. Stimulus representations included direct, synaptic, and multiplexed responses that grew in complexity as the distance between the stimulation source and recorded neuron increased. These representations collapsed into patterns with lower information content at higher stimulation frequencies. With internodal activity propagation, a hierarchy of network pathways, including latent circuits, was revealed using glutamatergic blockade. As stimulus channels were added, divergent, non-linear effects were observed in local versus distant network layers. Pairwise difference analysis of neuronal responses suggested that neuronal ensembles generally outperformed individual cells in discriminating input patterns. Significance. Our data illuminate the complexity of spiking activity propagation in cortical networks in vitro, which is characterized by the transformation of an input into myriad outputs over several network layers. These results provide insight into how the brain potentially processes information and generates the neural code and could guide the development of clinical therapies based on multichannel brain stimulation.

Biodiversity of indigenous staphylococci of naturally fermented dry sausages and manufacturing environments of small-scale processing units.

PubMed

Leroy, Sabine; Giammarinaro, Philippe; Chacornac, Jean-Paul; Lebert, Isabelle; Talon, Régine

2010-04-01

The staphylococcal community of the environments of nine French small-scale processing units and their naturally fermented meat products was identified by analyzing 676 isolates. Fifteen species were accurately identified using validated molecular methods. The three prevalent species were Staphylococcus equorum (58.4%), Staphylococcus saprophyticus (15.7%) and Staphylococcus xylosus (9.3%). S. equorum was isolated in all the processing units in similar proportion in meat and environmental samples. S. saprophyticus was also isolated in all the processing units with a higher percentage in environmental samples. S. xylosus was present sporadically in the processing units and its prevalence was higher in meat samples. The genetic diversity of the strains within the three species isolated from one processing unit was studied by PFGE and revealed a high diversity for S. equorum and S. saprophyticus both in the environment and the meat isolates. The genetic diversity remained high through the manufacturing steps. A small percentage of the strains of the two species share the two ecological niches. These results highlight that some strains, probably introduced by the meat, will persist in the manufacturing environment, while other strains are more adapted to the meat products.

Bioreactors for guiding muscle tissue growth and development.

PubMed

Dennis, R G; Smith, B; Philp, A; Donnelly, K; Baar, K

2009-01-01

Muscle tissue bioreactors are devices which are employed to guide and monitor the development of engineered muscle tissue. These devices have a modern history that can be traced back more than a century, because the key elements of muscle tissue bioreactors have been studied for a very long time. These include barrier isolation and culture of cells, tissues and organs after isolation from a host organism; the provision of various stimuli intended to promote growth and maintain the muscle, such as electrical and mechanical stimulation; and the provision of a perfusate such as culture media or blood derived substances. An accurate appraisal of our current progress in the development of muscle bioreactors can only be made in the context of the history of this endeavor. Modern efforts tend to focus more upon the use of computer control and the application of mechanical strain as a stimulus, as well as substrate surface modifications to induce cellular organization at the early stages of culture of isolated muscle cells.

Effects of Social Isolation on Glucocorticoid Regulation in Social Mammals

PubMed Central

Hawkley, Louise C.; Cole, Steve W.; Capitanio, John P.; Norman, Greg J.; Cacioppo, John T.

2012-01-01

The regulation and function of the hypothalamic-pituitary-adrenocortical (HPA) axis and glucocorticoids have been well conserved across vertebrate species. Glucocorticoids influence a wide range of physiological functions that include glucose regulation, metabolism, inflammatory control, as well as cardiovascular, reproductive, and neuronal effects. Some of these are relatively quick-acting non-genomic effects, but most are slower-acting genomic effects. Thus, any stimulus that affects HPA function has the potential to exert wide-ranging short-term and long-term effects on much of vertebrate physiology. Here, we review the effects of social isolation on the functioning of the HPA axis in social species, and on glucocorticoid physiology in social mammals in particular. Evidence indicates that objective and perceived social isolation alter HPA regulation, although the nature and direction of the HPA response differs among species and across age. The inconsistencies in the direction and nature of HPA effects have implications for drawing cross-species conclusions about the effects of social isolation, and are particularly problematic for understanding HPA-related physiological processes in humans. The animal and human data are incommensurate because, for example, animal studies of objective isolation have typically not been modeled on, or for comparability with, the subjective experience of isolation in humans. An animal model of human isolation must be taken more seriously if we want to advance our understanding of the mechanisms for the effects of objective and perceived isolation in humans. PMID:22663934

Tuition and Fees at Virginia's State-Supported Colleges and Universities, 2009-10

ERIC Educational Resources Information Center

Zheng, Yan; Hix, Dan

2009-01-01

In order to speed the national economic recovery, create and save jobs, and provide services to people affected by the recession, the 111th United States Congress enacted and President Obama signed into law the American Recovery and Reinvestment Act of 2009 (ARRA)--an economic stimulus package worth $787 billion--on February 17, 2009. Virginia…

Is School Funding Fair? A National Report Card. Fourth Edition

ERIC Educational Resources Information Center

Baker, Bruce D.; Sciarra, David G.; Farrie, Danielle

2015-01-01

While the United States was recovering from the recent economic stress caused by the Great Recession, individual state economies were improving at a slow pace. In 2012, state education budgets came to a crossroads, as most states had exhausted their allocations of federal stimulus dollars. Prior editions of this report noted how many states used…

Characterizing Oscillatory Bursts in Single-Trial EEG Data

NASA Technical Reports Server (NTRS)

Knuth, K. H.; Shah, A. S.; Lakatos, P.; Schroeder, C. E.

2004-01-01

Oscillatory bursts in numerous bands ranging from low (theta) to high frequencies (e.g., gamma) undoubtedly play an important role in cortical dynamics. Largely because of the inadequacy of existing analytic techniques. however, oscillatory bursts and their role in cortical processing remains poorly understood. To study oscillatory bursts effectively one must be able to isolate them and characterize them in the single trial. We describe a series of straightforward analysis techniques that produce useful indices of burst characteristics. First, stimulus-evoked responses are estimated using Differentially Variable Component Analysis (dVCA), and are subtracted from the single-trial. The single-trial characteristics of the evoked responses are stored to identify possible correlations with burst activity. Time-frequency (T-F), or wavelet, analyses are then applied to the single trial residuals. While T-F plots have been used in recent studies to identify and isolate bursts, we go further by fitting each burst in the T-F plot with a two-dimensional Gaussian. This provides a set of burst characteristics, such as, center time. burst duration, center frequency. frequency dispersion. and amplitude, all of which contribute to the accurate characterization of the individual burst. The burst phase can also be estimated. Burst characteristics can be quantified with several standard techniques (e.g.. histogramming and clustering), as well as Bayesian techniques (e.g., blocking) to allow a more parametric description analysis of the characteristics of oscillatory bursts, and the relationships of specific parameters to cortical excitability and stimulus integration.

[One-year longitudinal change in parameters of myopic school children trained by a new accommodative training device--uncorrected visual acuity, refraction, axial length, accommodation, and pupil reaction].

PubMed

Watanabe, Kumiko; Hara, Naoto; Kimijima, Masumi; Kotegawa, Yasue; Ohno, Koji; Arimoto, Ako; Mukuno, Kazuo; Hisahara, Satoru; Horie, Hidenori

2012-10-01

School children with myopia were trained using a visual stimulation device that generated an isolated blur stimulus on a visual target, with a constant retinal image size and constant brightness. Uncorrected visual acuity, cycloplegic refraction, axial length, dynamic accommodation and papillary reaction were measured to investigate the effectiveness of the training. There were 45 school children with myopia without any other ophthalmic diseases. The mean age of the children was 8.9 +/- 2.0 years (age range; 6-16)and the mean refraction was -1.56 +/- 0.58 D (mean +/- standard deviation). As a visual stimulus, a white ring on a black background with a constant ratio of visual target size to retinal image size, irrespective of the distance, was displayed on a liquid crystal display (LCD), and the LCD was quickly moved from a proximal to a distal position to produce an isolated blur stimulus. Training with this visual stimulus was carried out in the relaxation phase of accommodation. Uncorrected visual acuity, cycloplegic refraction, axial length, dynamic accommodation and pupillary reaction were investigated before training and every 3 months during the training. Of the 45 subjects, 42 (93%) could be trained for 3 consecutive months, 33 (73%) for 6 months, 23 (51%) for 9 months, and 21 (47%) for 12 months. The mean refraction decreased by 0.83 +/- 0.56 D (mean +/- standard deviation) and the mean axial length increased by 0.47 +/- 0.16 mm at 1 year, showing that the training bad some effect in improving the visual acuity. In the tests of the dynamic accommodative responses, the latency of the accommodative-phase decreased from 0.4 +/- 0.2 sec to 0.3 +/- 0.1 sec at 1 year, the gain of the accommodative-phase improved from 69.0 +/- 27.0% to 93.3 +/- 13.4%, the maximum speed of the accommodative-phase increased from 5.1 +/- 2.2 D/sec to 6.8 +/- 2.2 D/sec and the gain of the relaxation-phase significantly improved from 52.1 +/- 26.0% to 72.7 +/- 13.7% (corresponding t-test, p < 0.005). No significant changes were observed in the pupillary reaction. The training device was useful for improving the accommodative functions and accommodative excess, suggesting that it may be able to suppress the progression of low myopia, development of which is known to be strongly influenced by environmental factors.

Comparison of the gentamicin resistance transposon Tn5281 with regions encoding gentamicin resistance in Enterococcus faecalis isolates from diverse geographic locations.

PubMed Central

Hodel-Christian, S L; Murray, B E

1992-01-01

The genetic determinant encoding gentamicin resistance (Gmr) on the beta-lactamase encoding plasmid pBEM10 of Enterococcus faecalis HH22 is carried on a transposon, termed Tn5281, that is highly related to the staphylococcal Gmr transposons Tn4001 found in Australian isolates of Staphylococcus aureus and Tn4031 found in United States isolates of Staphylococcus epidermidis. We have now studied plasmid DNA from Gmr strains of E. faecalis isolated from diverse geographical locations (Houston, Pennsylvania, Thailand, and Chile) by using restriction endonuclease analysis and DNA-DNA hybridization to determine whether other Gmr E. faecalis carry Tn5281 or a similar type of element. We also compared these enterococci to several United States isolates of Staphylococcus aureus with nonmobile Gmr determinants. Three E. faecalis isolates (from Houston and Chile) carried Tn5281-like elements, whereas two isolates (from Houston and Pennsylvania) had restriction endonuclease and DNA-DNA hybridization patterns more similar to those of the Tn4001-IS257 hybrid found in the nonmobile Gmr determinants in United States isolates of S. aureus. A strain from Thailand had a third pattern unrelated to either Tn5281 or the nonmobile Gmr determinants present in United States isolates of S. aureus. Our results demonstrate that there is both similarity and diversity between the Gmr determinant of strains of E. faecalis isolated in diverse geographic locations. Images PMID:1332593

The effect of incipient presbyopia on the correspondence between accommodation and vergence.

PubMed

Baker, Fiona J; Gilmartin, Bernard

2002-06-01

To investigate the accommodation-convergence relationship during the incipient phase of presbyopia. The study aimed to differentiate between the current theories of presbyopia and to explore the mechanisms by which the oculomotor system compensates for the change in the accommodation-convergence relationship contingent on a declining amplitude of accommodation. Using a Canon R-1 open-view autorefractor and a haploscope device, measurements were made of the stimulus and response accommodative convergence/accommodation ratios and the convergence accommodation/convergence ratio of 28 subjects aged 35-45 years at the commencement of the study. Amplitude of accommodation was assessed using a push-down technique. The measurements were repeated at 4-monthly intervals over a 2-year period. The results showed that with the decline in the amplitude of accommodation there is an increase in the accommodative convergence response per unit of accommodative response and a decrease in the convergence accommodation response per unit of convergence. The results of this study fail to support the Hess-Gullstrand theory of presbyopia in that the ciliary muscle effort required to produce a unit change in accommodation increases, rather than stays constant, with age. Data show that the near vision response is limited to the maximum vergence response that can be tolerated and, despite being within the amplitude of accommodation, a stimulus may still appear blurred because the vergence component determines the proportion of available accommodation utilised during near vision.

Microsatellite Typing of Aspergillus flavus Strains in a Tunisian Onco-hematology Unit.

PubMed

Gheith, Soukeina; Saghrouni, Fatma; Normand, Anne-Cécile; Bannour, Wadiaa; Khelif, Abderrahim; Piarroux, Renaud; Ben Said, Moncef; Njah, Mansour; Ranque, Stéphane

2016-04-01

Aspergillus flavus is the most common species associated with invasive aspergillosis in Tunisia. The molecular epidemiology of the species is poorly documented. We used five highly discriminative microsatellite markers for the genotyping of clinical and hospital environmental A. flavus strains to assess whether IA could be hospital-acquired in the onco-hematology unit of the Farhat Hached teaching hospital of Sousse, Tunisia. The genotyping of 18 clinical isolates, collected from sputa of 17 acute leukemia patients, and 81 isolates, collected in these patients' hospital environment and food, identified 57 isolates that were grouped in 10 clones, each of them including 2-17 isolates. The remaining 42 isolates showed a unique genotype. Two main transmission scenarios were observed: (1) the same clone was isolated from different patients; (2) the same clone was isolated from a patient, its hospital environment and/or food. These findings strongly suggest the occurrence of hospital-acquired A. flavus infection/colonization in the investigated onco-hematology unit.

Fuel cell system including a unit for electrical isolation of a fuel cell stack from a manifold assembly and method therefor

DOEpatents

Kelley; Dana A. , Farooque; Mohammad , Davis; Keith

2007-10-02

A fuel cell system with improved electrical isolation having a fuel cell stack with a positive potential end and a negative potential, a manifold for use in coupling gases to and from a face of the fuel cell stack, an electrical isolating assembly for electrically isolating the manifold from the stack, and a unit for adjusting an electrical potential of the manifold such as to impede the flow of electrolyte from the stack across the isolating assembly.

Suppression and Contrast Normalization in Motion Processing

PubMed Central

2017-01-01

Sensory neurons are activated by a range of stimuli to which they are said to be tuned. Usually, they are also suppressed by another set of stimuli that have little effect when presented in isolation. The interactions between preferred and suppressive stimuli are often quite complex and vary across neurons, even within a single area, making it difficult to infer their collective effect on behavioral responses mediated by activity across populations of neurons. Here, we investigated this issue by measuring, in human subjects (three males), the suppressive effect of static masks on the ocular following responses induced by moving stimuli. We found a wide range of effects, which depend in a nonlinear and nonseparable manner on the spatial frequency, contrast, and spatial location of both stimulus and mask. Under some conditions, the presence of the mask can be seen as scaling the contrast of the driving stimulus. Under other conditions, the effect is more complex, involving also a direct scaling of the behavioral response. All of this complexity at the behavioral level can be captured by a simple model in which stimulus and mask interact nonlinearly at two stages, one monocular and one binocular. The nature of the interactions is compatible with those observed at the level of single neurons in primates, usually broadly described as divisive normalization, without having to invoke any scaling mechanism. SIGNIFICANCE STATEMENT The response of sensory neurons to their preferred stimulus is often modulated by stimuli that are not effective when presented alone. Individual neurons can exhibit multiple modulatory effects, with considerable variability across neurons even in a single area. Such diversity has made it difficult to infer the impact of these modulatory mechanisms on behavioral responses. Here, we report the effects of a stationary mask on the reflexive eye movements induced by a moving stimulus. A model with two stages, each incorporating a divisive modulatory mechanism, reproduces our experimental results and suggests that qualitative variability of masking effects in cortical neurons might arise from differences in the extent to which such effects are inherited from earlier stages. PMID:29018158

Virtual Balancing for Studying and Training Postural Control.

PubMed

Buettner, Daniela; Dalin, Daniela; Wiesmeier, Isabella K; Maurer, Christoph

2017-01-01

Postural control during free stance has been frequently interpreted in terms of balancing an inverted pendulum. This even holds, if subjects do not balance their own, but an external body weight. We introduce here a virtual balancing apparatus, which produces torque in the ankle joint as a function of ankle angle resembling the gravity and inertial effects of free standing. As a first aim of this study, we systematically modified gravity, damping, and inertia to examine its effect on postural control beyond the physical constraints given in the real world. As a second aim, we compared virtual balancing to free stance to test its suitability for balance training in patients who are not able to balance their full body weight due to certain medical conditions. In a feasibility study, we analyzed postural control during free stance and virtual balancing in 15 healthy subjects. Postural control was characterized by spontaneous sway measures and measures of perturbed stance. During free stance, perturbations were induced by pseudorandom anterior-posterior tilts of the body support surface. In the virtual balancing task, we systematically varied the anterior-posterior position of the foot plate where the balancing forces are zero following a similar pseudorandom stimulus profile. We found that subjects' behavior during virtual balancing resembles free stance on a tilting platform. This specifically holds for the profile of body excursions as a function of stimulus frequencies. Moreover, non-linearity between stimulus and response amplitude is similar in free and virtual balancing. The overall larger stimulus induced body excursions together with an altered phase behavior between stimulus and response could be in part explained by the limited use of vestibular and visual feedback in our experimental setting. Varying gravity or damping significantly affected postural behavior. Inertia as an isolated factor had a mild effect on the response functions. We conclude that virtual balancing may be well suited to simulate conditions which could otherwise only be realized in space experiments or during parabolic flights. Further studies are needed to examine patients' potential benefit of virtual balance training.

Neural correlates of olfactory learning paradigms in an identified neuron in the honeybee brain.

PubMed

Mauelshagen, J

1993-02-01

1. Sensitization and classical odor conditioning of the proboscis extension reflex were functionally analyzed by repeated intracellular recordings from a single identified neuron (PE1-neuron) in the central bee brain. This neuron belongs to the class of "extrinsic cells" arising from the pedunculus of the mushroom bodies and has extensive arborizations in the median and lateral protocerebrum. The recordings were performed on isolated bee heads. 2. Two different series of physiological experiments were carried out with the use of a similar temporal succession of stimuli as in previous behavioral experiments. In the first series, one group of animals was used for a single conditioning trial [conditioned stimulus (CS), carnation; unconditioned stimulus (US), sucrose solution to the antennae and proboscis), a second group was used for sensitization (sensitizing stimulus, sucrose solution to the antennae and/or proboscis), and the third group served as control (no sucrose stimulation). In the second series, a differential conditioning paradigm (paired odor CS+, carnation; unpaired odor CS-, orange blossom) was applied to test the associative nature of the conditioning effect. 3. The PE1-neuron showed a characteristic burstlike odor response before the training procedures. The treatments resulted in different spike-frequency modulations of this response, which were specific for the nonassociative and associative stimulus paradigms applied. During differential conditioning, there are dynamic up and down modulations of spike frequencies and of the DC potentials underlying the responses to the CS+. Overall, only transient changes in the minute range were observed. 4. The results of the sensitization procedures suggest two qualitatively different US pathways. The comparison between sensitization and one-trial conditioning shows differential effects of nonassociative and associative stimulus paradigms on the response behavior of the PE1-neuron. The results of the differential conditioning procedure reveal that the effect observed for the one-trial conditioning paradigm is of an associative nature and that there might be modulations, which are specific for single and multiple trial conditioning procedures. It is hypothesized that the PE1-neuron is a possible element involved in the short-term acquisition, rather than in the long-term storage, of an associative olfactory memory in the honeybee.

Virtual Balancing for Studying and Training Postural Control

PubMed Central

Buettner, Daniela; Dalin, Daniela; Wiesmeier, Isabella K.; Maurer, Christoph

2017-01-01

Postural control during free stance has been frequently interpreted in terms of balancing an inverted pendulum. This even holds, if subjects do not balance their own, but an external body weight. We introduce here a virtual balancing apparatus, which produces torque in the ankle joint as a function of ankle angle resembling the gravity and inertial effects of free standing. As a first aim of this study, we systematically modified gravity, damping, and inertia to examine its effect on postural control beyond the physical constraints given in the real world. As a second aim, we compared virtual balancing to free stance to test its suitability for balance training in patients who are not able to balance their full body weight due to certain medical conditions. In a feasibility study, we analyzed postural control during free stance and virtual balancing in 15 healthy subjects. Postural control was characterized by spontaneous sway measures and measures of perturbed stance. During free stance, perturbations were induced by pseudorandom anterior-posterior tilts of the body support surface. In the virtual balancing task, we systematically varied the anterior-posterior position of the foot plate where the balancing forces are zero following a similar pseudorandom stimulus profile. We found that subjects' behavior during virtual balancing resembles free stance on a tilting platform. This specifically holds for the profile of body excursions as a function of stimulus frequencies. Moreover, non-linearity between stimulus and response amplitude is similar in free and virtual balancing. The overall larger stimulus induced body excursions together with an altered phase behavior between stimulus and response could be in part explained by the limited use of vestibular and visual feedback in our experimental setting. Varying gravity or damping significantly affected postural behavior. Inertia as an isolated factor had a mild effect on the response functions. We conclude that virtual balancing may be well suited to simulate conditions which could otherwise only be realized in space experiments or during parabolic flights. Further studies are needed to examine patients' potential benefit of virtual balance training. PMID:29018320

Fine typing of methicillin-resistant Staphylococcus aureus isolates using direct repeat unit and staphylococcal interspersed repeat unit typing methods.

PubMed

Ho, Cheng-Mao; Ho, Mao-Wang; Li, Chi-Yuan; Lu, Jang-Jih

2015-08-01

Methicillin-resistant Staphylococcus aureus (MRSA) typing is an important epidemiologic tool for monitoring trends and preventing outbreaks. However, the efficiency of various MRSA typing methods for each SCCmec MRSA isolate is rarely evaluated. A total of 157 MRSA isolates from four different regions in Taiwan were typed with five different molecular methods, including SCCmec typing, multilocus sequence typing (MLST), spa typing, mec-associated direct repeat unit (dru) copy number determination, and staphylococcal interspersed repeat unit (SIRU) profiling. There were four SCCmec types, eight MLST types, 15 spa types, 11 dru types, and 31 SIRU profiles. The most common type determined by each molecular typing method was SCCmec III (115 isolates, 73.2%), ST239 (99 isolates, 63.1%), t037 (107 isolates, 68.2%), 14 dru copies (76 isolates, 48.4%), and SIRU profile 3013722 (102 isolates, 65%), respectively. When using the combination of MLST, spa typing, and dru copy number, ST5-t002-4 (n = 8), ST239-t037-14 (n = 68), ST59-t437-9 (n = 9), and ST59-t437-11 (n = 6) were found to be the most common types of SCCmec types II (n = 9), III (n = 115), IV (n = 21), and VT (n = 11) isolates, respectively. SCCmec type III isolates were further classified into 11 dru types. Of the 21 SCCmec type IV isolates, 14 SIRU profiles were found. Seven SIRU patterns were observed in the 11 SCCmec type VT isolates. Different typing methods showed a similar Hunter-Gaston discrimination index among the 157 MRSA isolates. However, dru and SIRU typing methods had a better discriminatory power for SCCmec type III and SCCmec types IV and VT isolates, respectively, suggesting that dru and SIRU can be used to further type these isolates. Copyright © 2013. Published by Elsevier B.V.

Allozyme differentiation of intersterility groups of Heterobasidion annosum isolated from conifers in the western United States

Treesearch

W.J. Otrosina; T.E. Chase; F.W. Cobb

1992-01-01

Allozyme analysis was conducted on 64 isolates from basidiocarps of Heterobasidion annosum. The isolates belonged to the "S" and "P" intersterility groups and were collected from five conifer species found in the western United States. Ten allozyme loci distributed among eight enzyme systems were examined. Intersterility groups differed at nine...

Improving accuracy of portion-size estimations through a stimulus equivalence paradigm.

PubMed

Hausman, Nicole L; Borrero, John C; Fisher, Alyssa; Kahng, SungWoo

2014-01-01

The prevalence of obesity continues to increase in the United States (Gordon-Larsen, The, & Adair, 2010). Obesity can be attributed, in part, to overconsumption of energy-dense foods. Given that overeating plays a role in the development of obesity, interventions that teach individuals to identify and consume appropriate portion sizes are warranted. Specifically, interventions that teach individuals to estimate portion sizes correctly without the use of aids may be critical to the success of nutrition education programs. The current study evaluated the use of a stimulus equivalence paradigm to teach 9 undergraduate students to estimate portion size accurately. Results suggested that the stimulus equivalence paradigm was effective in teaching participants to make accurate portion size estimations without aids, and improved accuracy was observed in maintenance sessions that were conducted 1 week after training. Furthermore, 5 of 7 participants estimated the target portion size of novel foods during extension sessions. These data extend existing research on teaching accurate portion-size estimations and may be applicable to populations who seek treatment (e.g., overweight or obese children and adults) to teach healthier eating habits. © Society for the Experimental Analysis of Behavior.

A three-year surveillance of nosocomial infections by methicillin-resistant Staphylococcus haemolyticus in newborns reveals the disinfectant as a possible reservoir.

PubMed

Ben Saida, N; Marzouk, M; Ferjeni, A; Boukadida, J

2009-05-01

Study of the clonality of methicillin-resistant Staphylococcus haemolyticus responsible of epidemic infections in a neonatal intensive care unit. Methicillin-resistant Staphylococcus haemolyticus isolates were collected during the period from March 2004 to November 2006, from newborns, the clean hands of nurses and from disinfectant bottles used in the unit. Molecular typing by pulsed-field gel electrophoresis (PFGE) was achieved for all isolates. Forty-six isolates of S. haemolyticus resistant to methicillin were collected from 42 newborns, the hand of two nurses and from two disinfectant bottles used in the unit. PFGE analysis revealed five types (A, B, C, D and E) among newborns isolates. Types A and B were predominant. Nurses' isolates revealed PFGE types similar to types A and B. Disinfectant isolates were of type B. qacA/B PCR analysis revealed that the majority of type B isolates contain the disinfectant resistance gene qacA/B. No isolate of type A possessed this gene. These results suggest that MRSH neonatal infections are caused by a limited number of clones. Clone B was able to survive in disinfectant bottles and to conserve its ability to infect newborns. We therefore conclude that the disinfectant can serve as a reservoir for MRSH and point out the need to control all disinfectants used in a neonatal intensive care unit.

Correlates and Cross-Linguistic Comparisons of Informativeness and Efficiency on Nicholas and Brookshire Discourse Stimuli in Spanish/English Bilingual Adults

ERIC Educational Resources Information Center

Edmonds, Lisa A.

2013-01-01

Purpose: The purpose of this study was to determine (a) correlates of informativeness and efficiency in discourse and (b) potential cross-linguistic and stimulus type (picture vs. nonpicture) differences in measures of informativeness and efficiency in Spanish/English bilingual adults in the United States. Method: Eighty-eight Spanish/English…

Is Big Brother Watching You? The Evolving Role of the State in Regulating and Conducting Quality Assurance. CIQG Publication Series

ERIC Educational Resources Information Center

Salmi, Jamil

2015-01-01

A recent report published in the United Kingdom proposed the image of "an avalanche" to describe the radical changes affecting tertiary education in many parts of the world (Barber, Donnelly and Rizvi, 2013). Indeed, powerful transformative forces of three kinds--rupture factors, crisis factors and stimulus factors--are challenging…

The Integration of Object Levels and Their Content: A Theory of Global/Local Processing and Related Hemispheric Differences

ERIC Educational Resources Information Center

Hubner, Ronald; Volberg, Gregor

2005-01-01

This article presents and tests the authors' integration hypothesis of global/local processing, which proposes that at early stages of processing, the identities of global and local units of a hierarchical stimulus are represented separately from information about their respective levels and that, therefore, identity and level information have to…

Advanced Neuroscience Interface Research

DTIC Science & Technology

2002-05-01

in vitro. Herein, we also report on the utilization of in vitro high -resolution MRS of a specimen of the same tumor with the ... The prior use of VEs to treat phobias has centered on the repeated presentation of the fear- inducing stimulus to the patient in such a manner that the ...inherent in pneumatic headphones (as sound propagates from the driver unit into the

National Year of Reading: A Year-Long Celebration and a Lasting Legacy

ERIC Educational Resources Information Center

Ellard, Robyn; Kelly, Paula; McKerracher, Sue

2012-01-01

The alarming statistic that just under half (46%) of adult Australians cannot read confidently was a stimulus for Australian libraries to found the National Year of Reading (NYR). The idea for this campaign was based on the success of the United Kingdom's National Year of Reading (National Literacy Trust 2008), a campaign that aimed to build a…

Creativity and Education: Comparing the National Curricula of the States of the European Union and the United Kingdom

ERIC Educational Resources Information Center

Wyse, Dominic; Ferrari, Anusca

2015-01-01

In the past 20 years the importance of creativity as part of young people's education has increasingly been recognised. The stimulus for the growing emphasis on creativity has come from diverse sources including drives for greater national economic prosperity and enlightenment visions of young people's education. One facet of creativity in…

Long-term memory, neurogenesis, and signal novelty.

PubMed

Sokolov, E N; Nezlina, N I

2004-10-01

According to our suggested hypothesis, long-term memory is a collection of "gnostic units," selectively tuned to past events. The formation of long-term memory occurs with the involvement of constantly appearing new neurons which differentiate from stem cells during the process of neurogenesis, in particular in adults. Conversion of precursor neurons into "gnostic units" selective in relation to ongoing events, supplemented by the involvement of hippocampal "novelty neurons," which increase the flow of information needing to be fixed in long-term memory. "Gnostic units" form before the informational processes occurring in the ventral ("what?") and dorsal ("where?") systems. Formation of new "gnostic units" selectively tuned to a particular event results from the combination of excitation of the detector for stimulus characteristics and the novelty signal generated by "novelty neurons" in the hippocampus.

In vivo observation of transient photoreceptor movement correlated with oblique light stimulation

NASA Astrophysics Data System (ADS)

Lu, Yiming; Liu, Changgeng; Yao, Xincheng

2018-02-01

Rod-dominated transient retinal phototropism (TRP) has been observed in freshly isolated retinas, promising a noninvasive biomarker for high resolution assessment of retinal physiology. However, in vivo mapping of TRP is challenging due to its fast time course and sub-cellular signal magnitude. By developing a line-scanning and virtually structured detection based super-resolution ophthalmoscope, we report here in vivo observation of TRP in frog retina. In vivo characterization of TRP time course and magnitude were implemented by using variable light stimulus intensities.

Genetic variation of wheat streak mosaic virus in the United States Pacific Northwest.

PubMed

Robinson, Megan D; Murray, Timothy D

2013-01-01

Wheat streak mosaic virus (WSMV), the cause of wheat streak mosaic, is a widespread and damaging pathogen of wheat. WSMV is not a chronic problem of annual wheat in the United States Pacific Northwest but could negatively affect the establishment of perennial wheat, which is being developed as an alternative to annual wheat to prevent soil erosion. Fifty local isolates of WSMV were collected from 2008 to 2010 near Lewiston, ID, Pullman, WA, and the United States Department of Agriculture Central Ferry Research Station, near Pomeroy, WA to determine the amount of genetic variation present in the region. The coat protein gene from each isolate was sequenced and the data subjected to four different methods of phylogenetic analyses. Two well-supported clades of WSMV were identified. Isolates in clade I share sequence similarity with isolates from Central Europe; this is the first report of isolates from Central Europe being reported in the United States. Isolates in clade II are similar to isolates originating from Australia, Argentina, and the American Pacific Northwest. Nine isolates showed evidence of recombination and the same two well-supported clades were observed when recombinant isolates were omitted from the analysis. More polymorphic sites, parsimony informative sites, and increased diversity were observed in clade II than clade I, suggesting more recent establishment of the virus in the latter. The observed diversity within both clades could make breeding for durable disease resistance in perennial wheat difficult if there is a differential response of WSMV resistance genes to isolates from different clades.

Ca(2+) and frequency dependence of exocytosis in isolated somata of magnocellular supraoptic neurones of the rat hypothalamus.

PubMed

Soldo, Brandi L; Giovannucci, David R; Stuenkel, Edward L; Moises, Hylan C

2004-03-16

In addition to action potential-evoked exocytotic release at neurohypophysial nerve terminals, the neurohormones arginine vasopressin (aVP) and oxytocin (OT) undergo Ca(2+)-dependent somatodendritic release within the supraoptic and paraventricular hypothalamic nuclei. However, the cellular and molecular mechanisms that underlie this release have not been elucidated. In the present study, the whole-cell patch-clamp technique was utilized in combination with high-time-resolved measurements of membrane capacitance (C(m)) and microfluorometric measurements of cytosolic free Ca(2+) concentration ([Ca(2+)](i)) to examine the Ca(2+) and stimulus dependence of exocytosis in the somata of magnocellular neurosecretory cells (MNCs) isolated from rat supraoptic nucleus (SON). Single depolarizing steps (> or =20 ms) that evoked high-voltage-activated (HVA) Ca(2+) currents (I(Ca)) and elevations in intracellular Ca(2+) concentration were accompanied by an increase in C(m) in a majority (40/47) of SON neurones. The C(m) responses were composed of an initial Ca(2+)-independent, transient component and a subsequent, sustained phase of increased C(m) (termed DeltaC(m)) mediated by an influx of Ca(2+), and increased with corresponding prolongation of depolarizing step durations (20-200 ms). From this relationship we estimated the rate of vesicular release to be 1533 vesicles s(-1). Delivery of neurone-derived action potential waveforms (APWs) as stimulus templates elicited I(Ca) and also induced a DeltaC(m), provided APWs were applied in trains of greater than 13 Hz. A train of APWs modelled after the bursting pattern recorded from an OT-containing neurone during the milk ejection reflex was effective in supporting an exocytotic DeltaC(m) in isolated MNCs, indicating that the somata of SON neurones respond to physiological patterns of neuronal activity with Ca(2+)-dependent exocytotic activity.

Application of Roll-Isolated Inertial Measurement Units to the Instrumentation of Spinning Vehicles

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

BEADER,MARK E.

Roll-isolated inertial measurement units are developed at Sandia for use in the instrumentation, guidance, and control of rapidly spinning vehicles. Roll-isolation is accomplished by supporting the inertial instrument cluster (gyros and accelerometers) on a single gimbal, the axis of which is parallel to the vehicle's spin axis. A rotary motor on the gimbal is driven by a servo loop to null the roll gyro output, thus inertially stabilizing the gimbal and instrument cluster while the vehicle spins around it. Roll-isolation prevents saturation of the roll gyro by the high vehicle spin rate, and vastly reduces measurement errors arising from gyromore » scale factor and alignment uncertainties. Nine versions of Sandia-developed roll-isolated inertial measurement units have been flown on a total of 27 flight tests since 1972.« less

Genomic Analysis of a Pan-Resistant Isolate of Klebsiella pneumoniae, United States 2016

PubMed Central

Lutgring, Joseph D.; Lonsway, David R.; Anderson, Karen F.; Kiehlbauch, Julia A.; Chen, Lei; Walters, Maroya Spalding; Sjölund-Karlsson, Maria; Rasheed, J. Kamile; Kallen, Alexander; Halpin, Alison Laufer

2018-01-01

ABSTRACT Antimicrobial resistance is a threat to public health globally and leads to an estimated 23,000 deaths annually in the United States alone. Here, we report the genomic characterization of an unusual Klebsiella pneumoniae, nonsusceptible to all 26 antibiotics tested, that was isolated from a U.S. patient. The isolate harbored four known beta-lactamase genes, including plasmid-mediated blaNDM-1 and blaCMY-6, as well as chromosomal blaCTX-M-15 and blaSHV-28, which accounted for resistance to all beta-lactams tested. In addition, sequence analysis identified mechanisms that could explain all other reported nonsusceptibility results, including nonsusceptibility to colistin, tigecycline, and chloramphenicol. Two plasmids, IncA/C2 and IncFIB, were closely related to mobile elements described previously and isolated from Gram-negative bacteria from China, Nepal, India, the United States, and Kenya, suggesting possible origins of the isolate and plasmids. This is one of the first K. pneumoniae isolates in the United States to have been reported to the Centers for Disease Control and Prevention (CDC) as nonsusceptible to all drugs tested, including all beta-lactams, colistin, and tigecycline. PMID:29615503

Investigation of the speed of reaction on external stimulus in schizophrenic psychosis.

PubMed

Zampera, E

1997-06-01

In 30 schizophrenic examinees, the latention time was measured. This time is referred to as an interval between the start of the stimulus and the response to the stimulus in the skin-galvanic reflex. Elementary stimulation has been applied, using device's timer tone and clapping of hands, which should simulate and associate the thunderclap. The intensity of psychosis was measured according to the Metric scale of psychotic behavior by Rogina, while the intensity of anxiety was measured by psychological tests: Rorschach's psycho-diagnostic test and Spillberger's questionnaire for anxiety. The reaction to the stimulus and latention time were registered using polygraph unit in order to record skin-galvanic reflex. The research was performed at two separate time points: prior to the therapy with derivatives of the phenothiazine group (the experimental examination group), and 25 days after the therapy (control group). The research has shown that the latention time in schizophrenic examinees does not significantly differ from the corresponding time in healthy controls, and it averages 2.30 seconds. Furthermore, no statistically significant difference in latention time before and after the therapy was observed. However, before the therapy started, i.e. in experimental group," the examinees who were psychotic to a greater extent have shown longer latention than those less psychotic. Additional finding was that the examinees from experimental group who were more anxious according to psychological tests have also shown longer latention time. After the therapy, the reaction to the external stimulus was stronger, which was expressed in increased reaction amplitude in skin-galvanic reflex. The latention time was prolonged, especially in case of examinees that were psychotic to a smaller extent before the therapy. We can conclude that so-called transformed psychotic anxiety was replaced after the therapy with a "new" anxiety-existential fear, i.e. the stronger anxious expectation and confusion appeared because the anxiety in its "free-floating" form remained very high. After the therapy, psychotic protection failed to appear and the reaction characteristics are a consequence of the delaying the confrontation with reality, which was registered as a prolonged latention time, i.e. response to external stimulus.

Discrete coding of stimulus value, reward expectation, and reward prediction error in the dorsal striatum.

PubMed

Oyama, Kei; Tateyama, Yukina; Hernádi, István; Tobler, Philippe N; Iijima, Toshio; Tsutsui, Ken-Ichiro

2015-11-01

To investigate how the striatum integrates sensory information with reward information for behavioral guidance, we recorded single-unit activity in the dorsal striatum of head-fixed rats participating in a probabilistic Pavlovian conditioning task with auditory conditioned stimuli (CSs) in which reward probability was fixed for each CS but parametrically varied across CSs. We found that the activity of many neurons was linearly correlated with the reward probability indicated by the CSs. The recorded neurons could be classified according to their firing patterns into functional subtypes coding reward probability in different forms such as stimulus value, reward expectation, and reward prediction error. These results suggest that several functional subgroups of dorsal striatal neurons represent different kinds of information formed through extensive prior exposure to CS-reward contingencies. Copyright © 2015 the American Physiological Society.

Discrete coding of stimulus value, reward expectation, and reward prediction error in the dorsal striatum

PubMed Central

Oyama, Kei; Tateyama, Yukina; Hernádi, István; Tobler, Philippe N.; Iijima, Toshio

2015-01-01

To investigate how the striatum integrates sensory information with reward information for behavioral guidance, we recorded single-unit activity in the dorsal striatum of head-fixed rats participating in a probabilistic Pavlovian conditioning task with auditory conditioned stimuli (CSs) in which reward probability was fixed for each CS but parametrically varied across CSs. We found that the activity of many neurons was linearly correlated with the reward probability indicated by the CSs. The recorded neurons could be classified according to their firing patterns into functional subtypes coding reward probability in different forms such as stimulus value, reward expectation, and reward prediction error. These results suggest that several functional subgroups of dorsal striatal neurons represent different kinds of information formed through extensive prior exposure to CS-reward contingencies. PMID:26378201

Threshold setting by the surround of cat retinal ganglion cells.

PubMed

Barlow, H B; Levick, W R

1976-08-01

1. The slope of curves relating the log increment threshold to log background luminance in cat retinal ganglion cells is affected by the area and duration of the test stimulus, as it is in human pyschophysical experiments. 2. Using large area, long duration stimuli the slopes average 0-82 and approach close to 1 (Weber's Law) in the steepest cases. Small stimuli gave an average of 0-53 for on-centre units using brief stimuli, and 0-56 for off-centre units, using long stimuli. Slopes under 0-5 (square root law) were not found over an extended range of luminances. 3. On individual units the slope was generally greater for larger and longer test stimulus, but no unit showed the full extent of change from slope of 0-5 to slope of 1. 4. The above differences hold for objective measures of quantum/spike ratio, as well as for thresholds either judged by ear or assessed by calculation. 5. The steeper slope of the curves for large area, long duration test stimuli compared with small, long duration stimuli, is associated with the increased effectiveness of antagonism from the surround at high backgrounds. This change may be less pronounced in off-centre units, one of which (probably transient Y-type) showed no difference of slope, and gave parallel area-threshold curves at widely separated background luminances, confirming the importance of differential surround effectiveness in changing the slope of the curves. 6. In on-centre units, the increased relative effectiveness of the surround is associated with the part of the raised background light that falls on the receptive field centre. 7. It is suggested that the variable surround functions as a zero-offset control that sets the threshold excitation required for generating impulses, and that this is separate from gain-setting adaptive mechanisms. This may be how ganglion cells maintain high incremental sensitivity in spite of a strong maintained excitatory drive that would otherwise cause compressive response non-linearities.

Sequence of Reston Virus Isolate AZ-1435, an Ebolavirus Isolate Obtained during the 1989-1990 Reston Virus Epizootic in the United States.

PubMed

Cornish, Joseph P; Diaz, Larissa; Ricklefs, Stacy M; Kanakabandi, Kishore; Sword, Jennifer; Jahrling, Peter B; Kuhn, Jens H; Porcella, Stephen F; Johnson, Reed F

2017-01-12

Reston virus (RESTV) was discovered in 1989-1990 during three connected epizootics of highly lethal viral hemorrhagic fever among captive macaques in primate housing facilities in the United States and Philippines. Currently, only one RESTV isolate from that outbreak (named Pennsylvania) has been sequenced. Here, we report the sequence of a second isolate, Reston virus/M.fascicularis-tc/USA/1990/Philippines89-AZ1435. Copyright © 2017 Cornish et al.

Legionellosis acquired through a dental unit: a case study.

PubMed

Schönning, C; Jernberg, C; Klingenberg, D; Andersson, S; Pääjärvi, A; Alm, E; Tano, E; Lytsy, B

2017-05-01

In 2012, an elderly immunocompromised man died from legionellosis at a hospital in Uppsala, Sweden. The patient had visited a dental ward at the hospital during the incubation period. Legionella spp. at a concentration of 2000 colony-forming units/L were isolated from the cupfiller outlet providing water for oral rinsing. Isolates from the patient and the dental unit were Legionella pneumophila serogroup 1, subgroup Knoxville and ST9. Pulsed-field gel electrophoresis and whole-genome sequencing strongly suggested that the isolates were of common origin. This report presents one of few documented cases of legionellosis acquired through a dental unit. Copyright © 2017 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.

Habituation of LG-mediated tailflip in the crayfish.

PubMed

Nagayama, Toshiki; Araki, Makoto

2015-06-01

Crayfish escape from threatening stimuli by tailflipping. If a stimulus is applied to the rear, crayfish escape up and forwards in a summersault maneuver that is mediated by the activation of lateral giant (LG) interneurons. The occurrence probability of LG-mediated tailflip, however, diminishes and habituates if a stimulus is repeatedly applied. Since crayfish have a relatively simple CNS with many identifiable neurons, crayfish represent a good animal to analyze the cellular basis of habituation. A reduction in the amplitude of the EPSP in the LGs, caused by direct chemical synaptic connection from sensory afferents by repetitive stimulations, is essential to bring about an inactivation of the LGs. The spike response of the LGs recovers within several minutes of habituation, but the LGs subsequently fail to spike when an additional stimulus is applied after specific periods following habituation. These results indicate that a decline in synaptic efficacy from the mechanosensory afferents recovers readily after a short delay, but then the excitability of the LGs themselves decreases. Furthermore, the processes underlying habituation are modulated depending on a social status. When two crayfish encounter each other, a winner-loser relationship is established. With a short interstimulus interval of 5 s, the rate of habituation of the LG in both socially dominant and subordinate crayfish becomes lower than in socially isolated animals. Serotonin and octopamine affect this social status-dependent modulation of habituation by means of activation of downstream second messenger system of cAMP and IP3 cascades, respectively.

Effect of acoustic similarity on short-term auditory memory in the monkey

PubMed Central

Scott, Brian H.; Mishkin, Mortimer; Yin, Pingbo

2013-01-01

Recent evidence suggests that the monkey’s short-term memory in audition depends on a passively retained sensory trace as opposed to a trace reactivated from long-term memory for use in working memory. Reliance on a passive sensory trace could render memory particularly susceptible to confusion between sounds that are similar in some acoustic dimension. If so, then in delayed matching-to-sample, the monkey’s performance should be predicted by the similarity in the salient acoustic dimension between the sample and subsequent test stimulus, even at very short delays. To test this prediction and isolate the acoustic features relevant to short-term memory, we examined the pattern of errors made by two rhesus monkeys performing a serial, auditory delayed match-to-sample task with interstimulus intervals of 1 s. The analysis revealed that false-alarm errors did indeed result from similarity-based confusion between the sample and the subsequent nonmatch stimuli. Manipulation of the stimuli showed that removal of spectral cues was more disruptive to matching behavior than removal of temporal cues. In addition, the effect of acoustic similarity on false-alarm response was stronger at the first nonmatch stimulus than at the second one. This pattern of errors would be expected if the first nonmatch stimulus overwrote the sample’s trace, and suggests that the passively retained trace is not only vulnerable to similarity-based confusion but is also highly susceptible to overwriting. PMID:23376550

Deformation strain is the main physical driver for skeletal precursors to undergo osteogenesis in earlier stages of osteogenic cell maturation.

PubMed

Ramani-Mohan, Ram-Kumar; Schwedhelm, Ivo; Finne-Wistrand, Anna; Krug, Melanie; Schwarz, Thomas; Jakob, Franz; Walles, Heike; Hansmann, Jan

2018-03-01

Mesenchymal stem cells play a major role during bone remodelling and are thus of high interest for tissue engineering and regenerative medicine applications. Mechanical stimuli, that is, deformation strain and interstitial fluid-flow-induced shear stress, promote osteogenic lineage commitment. However, the predominant physical stimulus that drives early osteogenic cell maturation is not clearly identified. The evaluation of each stimulus is challenging, as deformation and fluid-flow-induced shear stress interdepend. In this study, we developed a bioreactor that was used to culture mesenchymal stem cells harbouring a strain-responsive AP-1 luciferase reporter construct, on porous scaffolds. In addition to the reporter, mineralization and vitality of the cells was investigated by alizarin red staining and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. Quantification of the expression of genes associated to bone regeneration and bone remodelling was used to confirm alizarin red measurements. Controlled perfusion and deformation of the 3-dimensional scaffold facilitated the alteration of the expression of osteogenic markers, luciferase activity, and calcification. To isolate the specific impact of scaffold deformation, a computational model was developed to derive a perfusion flow profile that results in dynamic shear stress conditions present in periodically loaded scaffolds. In comparison to actually deformed scaffolds, a lower expression of all measured readout parameters indicated that deformation strain is the predominant stimulus for skeletal precursors to undergo osteogenesis in earlier stages of osteogenic cell maturation. Copyright © 2017 John Wiley & Sons, Ltd.

The Semicircular Canal Microphonic

NASA Technical Reports Server (NTRS)

Rabbitt, R. D.; Boyle, R.; Highstein, S. M.; Dalton, Bonnie P. (Technical Monitor)

2002-01-01

Present experiments were designed to quantify the alternating current (AC) component of the semicircular canal microphonic for angular motion stimulation as a function of stimulus frequency and amplitude. The oyster toadfish, Opsanus tau, was used as the experimental model. Calibrated mechanical indentation of the horizontal canal duct was used as a stimulus to generate hair-cell and afferent responses reproducing those present during head rotation. Sensitivity to polarization of the endolymph DC voltage re: perilymph was also investigated. Modulation of endolymph voltage was recorded using conventional glass electrodes and lock-in amplification over the frequency range 0.2-80 Hz. Access to the endolymph for inserting voltage recording and current passing electrodes was obtained by sectioning the anterior canal at its apex and isolating the cut ends in air. For sinusoidal stimulation below approx.10 Hz, the horizontal semicircular canal AC microphonic was nearly independent of stimulus frequency and equal to approximately 4 microV per micron indent (equivalent to approx. 1 microV per deg/s). A saturating nonlinearity decreasing the microphonic gain was present for stimuli exceeding approx.3 micron indent (approx. 12 deg/s angular velocity). The phase was not sensitive to the saturating nonlinearity. The microphonic exhibited a resonance near 30Hz consistent with basolateral current hair cell resonance observed previously in voltage-clamp records from semicircular canal hair cells. The magnitude and phase of the microphonic exhibited sensitivity to endolymphatic polarization consistent with electro-chemical reversal of hair cell transduction currents.

Effect of acoustic similarity on short-term auditory memory in the monkey.

PubMed

Scott, Brian H; Mishkin, Mortimer; Yin, Pingbo

2013-04-01

Recent evidence suggests that the monkey's short-term memory in audition depends on a passively retained sensory trace as opposed to a trace reactivated from long-term memory for use in working memory. Reliance on a passive sensory trace could render memory particularly susceptible to confusion between sounds that are similar in some acoustic dimension. If so, then in delayed matching-to-sample, the monkey's performance should be predicted by the similarity in the salient acoustic dimension between the sample and subsequent test stimulus, even at very short delays. To test this prediction and isolate the acoustic features relevant to short-term memory, we examined the pattern of errors made by two rhesus monkeys performing a serial, auditory delayed match-to-sample task with interstimulus intervals of 1 s. The analysis revealed that false-alarm errors did indeed result from similarity-based confusion between the sample and the subsequent nonmatch stimuli. Manipulation of the stimuli showed that removal of spectral cues was more disruptive to matching behavior than removal of temporal cues. In addition, the effect of acoustic similarity on false-alarm response was stronger at the first nonmatch stimulus than at the second one. This pattern of errors would be expected if the first nonmatch stimulus overwrote the sample's trace, and suggests that the passively retained trace is not only vulnerable to similarity-based confusion but is also highly susceptible to overwriting. Copyright © 2013 Elsevier B.V. All rights reserved.

Genotypic relatedness and antimicrobial resistance of Salmonella Heidelberg isolated from chickens and turkeys in the midwestern United States.

PubMed

Nisar, Muhammad; Kassem, Issmat I; Rajashekara, Gireesh; Goyal, Sagar M; Lauer, Dale; Voss, Shauna; Nagaraja, Kakambi V

2017-05-01

Salmonella is one of the most common causes of foodborne illnesses in humans in the United States, and domestic poultry is considered an important source of this pathogen. Salmonella enterica subsp. enterica serovar Heidelberg is the fourth most commonly reported Salmonella from retail meats and food animals in the United States. We assessed the genotypes and antimicrobial resistance phenotypes of Salmonella Heidelberg isolated from various chicken and turkey hatcheries and breeder farms in the Midwest. The genotypes of 33 S. Heidelberg isolates from chickens ( n = 19) and turkeys ( n = 14) were compared using pulsed-field gel electrophoresis analysis. Cluster analysis of the fingerprints showed that the majority of the chicken isolates grouped together with 87% similarity; those from turkeys clustered with 88% similarity. Similarity between chicken and turkey isolates was also high (86%). Isolates from turkeys were generally more genetically diverse than those from chickens. Antimicrobial susceptibility analysis detected resistance to sulfisoxazole (36% of the isolates), streptomycin (33%), gentamicin (27%), tetracycline (24%), ampicillin and amoxicillin-clavulanic acid (15%), cefoxitin (12%), ceftriaxone and ceftiofur (12%), and chloramphenicol (9%). None of the isolates was resistant to azithromycin, ciprofloxacin, or nalidixic acid. Although the number of the isolates was limited in our study, we conclude that S. Heidelberg isolates from the same host generally clustered together and that a considerable number of the isolates were resistant to a number of antimicrobial agents.

Redundancy management of multiple KT-70 inertial measurement units applicable to the space shuttle

NASA Technical Reports Server (NTRS)

Cook, L. J.

1975-01-01

Results of an investigation of velocity failure detection and isolation for 3 inertial measuring units (IMU) and 2 inertial measuring units (IMU) configurations are presented. The failure detection and isolation algorithm performance was highly successful and most types of velocity errors were detected and isolated. The failure detection and isolation algorithm also included attitude FDI but was not evaluated because of the lack of time and low resolution in the gimbal angle synchro outputs. The shuttle KT-70 IMUs will have dual-speed resolvers and high resolution gimbal angle readouts. It was demonstrated by these tests that a single computer utilizing a serial data bus can successfully control a redundant 3-IMU system and perform FDI.

Abundance and Distribution of Geographically Isolated Wetlands across the Conterminous United States

EPA Science Inventory

Geographically isolated wetlands (GIWS) are important landscape elements involved in hydrologic, biogeochemical, and biological functioning. Their influence, under certain circumstances, can significantly affect other waters of the Unites States. However, there have been no data-...

Complete Genome Sequence of Tomato Mosaic Virus Isolated from Jasmine in the United States

PubMed Central

Fillmer, Kornelia; Adkins, Scott; Pongam, Patchara

2015-01-01

Tomato mosaic virus was reported from jasmine in Florida. We present the first complete genome sequence of a tomato mosaic virus isolate from this woody perennial plant in the United States. PMID:26159525

Outbreak of Invasive Wound Mucormycosis in a Burn Unit Due to Multiple Strains of Mucor circinelloides f. circinelloides Resolved by Whole-Genome Sequencing

PubMed Central

2018-01-01

ABSTRACT Mucorales are ubiquitous environmental molds responsible for mucormycosis in diabetic, immunocompromised, and severely burned patients. Small outbreaks of invasive wound mucormycosis (IWM) have already been reported in burn units without extensive microbiological investigations. We faced an outbreak of IWM in our center and investigated the clinical isolates with whole-genome sequencing (WGS) analysis. We analyzed M. circinelloides isolates from patients in our burn unit (BU1, Hôpital Saint-Louis, Paris, France) together with nonoutbreak isolates from Burn Unit 2 (BU2, Paris area) and from France over a 2-year period (2013 to 2015). A total of 21 isolates, including 14 isolates from six BU1 patients, were analyzed by whole-genome sequencing (WGS). Phylogenetic classification based on de novo assembly and assembly free approaches showed that the clinical isolates clustered in four highly divergent clades. Clade 1 contained at least one of the strains from the six epidemiologically linked BU1 patients. The clinical isolates were specific to each patient. Two patients were infected with more than two strains from different clades, suggesting that an environmental reservoir of clonally unrelated isolates was the source of contamination. Only two patients from BU1 shared one strain, which could correspond to direct transmission or contamination with the same environmental source. In conclusion, WGS of several isolates per patients coupled with precise epidemiological data revealed a complex situation combining potential cross-transmission between patients and multiple contaminations with a heterogeneous pool of strains from a cryptic environmental reservoir. PMID:29691339

A review of basin morphology and pool hydrology of isolated ponded wetlands: implications for seasonal forest pools of the northeastern United States

Treesearch

Robert T. Brooks; Robert T. Brooks

2005-01-01

Seasonal forest pools (SFPs) are geographically- and hydrologically- isolated ponded wetlands, in that they are topographically isolated from other surface waters. SFPs occur commonly throughout the temperate forests of the eastern United States and adjacent Canada. SFPs are ephemeral in occurrence, typically drying annually. The regular drying of SFPs excludes fish...

Event related aspects of somatosensory and auditory evoked potentials: noise or signals?

PubMed

Stowell, H

1985-05-01

The so-called Vertex Potential (VP) of human scalp-conducted and event related brain potential (ERBP), which occur as a slow and often large, biphasic sinusoid within the 100-400 msec time segment after transient stimulation in the three main sensory modalities, are the longest researched of all human evoked potential (EP) phenomena. Its variable amplitude has been directly correlated, in experiments expressly tailored for the purpose, with input/output variables such as the rate of acceleration of given stimulus parameters from a state of relative rest (RM function), interstimulus interval (ISI), stimulus intensity, skin potential and resistance changes (SPR and SRR), the peripheral electroneurogram (ENG), and experimentally isolated C-fiber afference; and with neuropsychological variables such as attention or vigilance, visual acuity, response time, subjective stimulus probability or expectancy, acute pain of both fast and slow kinds, intelligence quotient (IQ), and psychometric personality scores (e.g., extraversion versus introversion and neuroticism versus normality). Unfortunately, the cerebral, neural origins of the VP, if any, are unknown; it is reported as usually absent from cortex-surface EP in those primates and mammals hitherto studied, and also from human extracranial event related magnetic fields of the brain (ERMFb) insofar as these reveal only superficial tangential sources; but a possible analog has been recorded from deep subcortical electrodes during human neurosurgery. In view of the increasing published range and quantity of direct correlates of VP amplitude, and of the scarcity of data about its neuroanatomy and neurophysiology, it seemed a good idea to do some rudimentary signal analysis. Preliminary results from five subjects confirm earlier data: The VP of somatosensory (SEP) and auditory (AEP) evoked potentials, as obtained by scalp-conductance and either averaged or single-epoch, can be resolved into inconsistently stimulus synchronized frequency components which are also present as relatively unsynchronized waves in the theta and alpha bands (approx. 2-13 Hz) of the unstimulated or near-threshold-stimulated electroencephalogram (EEG). In averages of numerous single trials (20 less than N less than 102), initiated at interstimulus intervals longer than 2.5 sec and deliberately sequenced so that the initiator could learn to estimate the timing of stimulus onsets, the phase coherence of the power-dominant alpha and theta waves within the 100-400 msec time segment of ERBP is obvious when the stimulus is an intense transient and psychologically not "habituated".(ABSTRACT TRUNCATED AT 400 WORDS)

M protein gene type distribution among group A streptococcal clinical isolates recovered in Mexico City, Mexico, from 1991 to 2000, and Durango, Mexico, from 1998 to 1999: overlap with type distribution within the United States.

PubMed

Espinosa, Luz Elena; Li, Zhongya; Gomez Barreto, Demostenes; Calderon Jaimes, Ernesto; Rodriguez, Romeo S; Sakota, Varja; Facklam, Richard R; Beall, Bernard

2003-01-01

To examine the type distribution of pathogenic group A streptococcal (GAS) strains in Mexico, we determined the emm types of 423 GAS isolates collected from ill patients residing in Mexico (Durango or Mexico City). These included 282 throat isolates and 107 isolates from normally sterile sites. Of the other isolates, 38 were recovered from other miscellaneous infections. A total of 31 different emm types were found, revealing a broad overlap between commonly occurring emm types in Mexico and the United States. The information obtained in this study is consistent with the possibility that multivalent, M type-specific vaccines prepared for GAS strain distribution within the United States could theoretically protect against the majority of GAS strains causing disease in the two cities surveyed in Mexico.

M Protein Gene Type Distribution among Group A Streptococcal Clinical Isolates Recovered in Mexico City, Mexico, from 1991 to 2000, and Durango, Mexico, from 1998 to 1999: Overlap with Type Distribution within the United States

PubMed Central

Espinosa, Luz Elena; Li, Zhongya; Barreto, Demostenes Gomez; Jaimes, Ernesto Calderon; Rodriguez, Romeo S.; Sakota, Varja; Facklam, Richard R.; Beall, Bernard

2003-01-01

To examine the type distribution of pathogenic group A streptococcal (GAS) strains in Mexico, we determined the emm types of 423 GAS isolates collected from ill patients residing in Mexico (Durango or Mexico City). These included 282 throat isolates and 107 isolates from normally sterile sites. Of the other isolates, 38 were recovered from other miscellaneous infections. A total of 31 different emm types were found, revealing a broad overlap between commonly occurring emm types in Mexico and the United States. The information obtained in this study is consistent with the possibility that multivalent, M type-specific vaccines prepared for GAS strain distribution within the United States could theoretically protect against the majority of GAS strains causing disease in the two cities surveyed in Mexico. PMID:12517875

Cue competition in evaluative conditioning as a function of the learning process.

PubMed

Kattner, Florian; Green, C Shawn

2015-11-01

Evaluative conditioning (EC) is the change in the valence of a stimulus resulting from pairings with an affective (unconditioned) stimulus (US). With some exceptions, previous work has indicated that this form of conditioning might be insensitive to cue competition effects such as blocking and overshadowing. Here we assessed whether the extent of cue competition in EC depends upon the type of contingency learning during conditioning. Specifically, we contrasted a learning task that biased participants toward cognitive/inferential learning (i.e., predicting the US) with a learning task that prevented prolonged introspection (i.e., a rapid response made to the US). In all cases, standard EC effects were observed, with the subjective liking of stimuli changed in the direction of the valence of the US. More importantly, when inferential learning was likely, larger EC effects occurred for isolated stimuli than for compounds (indicating overshadowing). No blocking effects on explicit evaluations were observed for either learning task. Contingency judgments and implicit evaluations, however, were sensitive to blocking, indicating that the absence of a blocking effect on explicit evaluations might be due to inferences that occur during testing.

High-throughput behavioral screening method for detecting auditory response defects in zebrafish.

PubMed

Bang, Pascal I; Yelick, Pamela C; Malicki, Jarema J; Sewell, William F

2002-08-30

We have developed an automated, high-throughput behavioral screening method for detecting hearing defects in zebrafish. Our assay monitors a rapid escape reflex in response to a loud sound. With this approach, 36 adult zebrafish, restrained in visually isolated compartments, can be simultaneously assessed for responsiveness to near-field 400 Hz sinusoidal tone bursts. Automated, objective determinations of responses are achieved with a computer program that obtains images at precise times relative to the acoustic stimulus. Images taken with a CCD video camera before and after stimulus presentation are subtracted to reveal a response to the sound. Up to 108 fish can be screened per hour. Over 6500 fish were tested to validate the reliability of the assay. We found that 1% of these animals displayed hearing deficits. The phenotypes of non-responders were further assessed with radiological analysis for defects in the gross morphology of the auditory system. Nearly all of those showed abnormalities in conductive elements of the auditory system: the swim bladder or Weberian ossicles. Copyright 2002 Elsevier Science B.V.

Norepinephrine is coreleased with serotonin in mouse taste buds.

PubMed

Huang, Yijen A; Maruyama, Yutaka; Roper, Stephen D

2008-12-03

ATP and serotonin (5-HT) are neurotransmitters secreted from taste bud receptor (type II) and presynaptic (type III) cells, respectively. Norepinephrine (NE) has also been proposed to be a neurotransmitter or paracrine hormone in taste buds. Yet, to date, the specific stimulus for NE release in taste buds is not well understood, and the identity of the taste cells that secrete NE is not known. Chinese hamster ovary cells were transfected with alpha(1A) adrenoceptors and loaded with fura-2 ("biosensors") to detect NE secreted from isolated mouse taste buds and taste cells. Biosensors responded to low concentrations of NE (>or=10 nm) with a reliable fura-2 signal. NE biosensors did not respond to stimulation with KCl or taste compounds. However, we recorded robust responses from NE biosensors when they were positioned against mouse circumvallate taste buds and the taste buds were stimulated with KCl (50 mm) or a mixture of taste compounds (cycloheximide, 10 microm; saccharin, 2 mm; denatonium, 1 mm; SC45647, 100 microm). NE biosensor responses evoked by stimulating taste buds were reversibly blocked by prazosin, an alpha(1A) receptor antagonist. Together, these findings indicate that taste bud cells secrete NE when they are stimulated. We isolated individual taste bud cells to identify the origin of NE release. NE was secreted only from presynaptic (type III) taste cells and not receptor (type II) cells. Stimulus-evoked NE release depended on Ca(2+) in the bathing medium. Using dual biosensors (sensitive to 5-HT and NE), we found all presynaptic cells secrete 5-HT and 33% corelease NE with 5-HT.

Does skeletal muscle have an 'epi'-memory? The role of epigenetics in nutritional programming, metabolic disease, aging and exercise.

PubMed

Sharples, Adam P; Stewart, Claire E; Seaborne, Robert A

2016-08-01

Skeletal muscle mass, quality and adaptability are fundamental in promoting muscle performance, maintaining metabolic function and supporting longevity and healthspan. Skeletal muscle is programmable and can 'remember' early-life metabolic stimuli affecting its function in adult life. In this review, the authors pose the question as to whether skeletal muscle has an 'epi'-memory? Following an initial encounter with an environmental stimulus, we discuss the underlying molecular and epigenetic mechanisms enabling skeletal muscle to adapt, should it re-encounter the stimulus in later life. We also define skeletal muscle memory and outline the scientific literature contributing to this field. Furthermore, we review the evidence for early-life nutrient stress and low birth weight in animals and human cohort studies, respectively, and discuss the underlying molecular mechanisms culminating in skeletal muscle dysfunction, metabolic disease and loss of skeletal muscle mass across the lifespan. We also summarize and discuss studies that isolate muscle stem cells from different environmental niches in vivo (physically active, diabetic, cachectic, aged) and how they reportedly remember this environment once isolated in vitro. Finally, we will outline the molecular and epigenetic mechanisms underlying skeletal muscle memory and review the epigenetic regulation of exercise-induced skeletal muscle adaptation, highlighting exercise interventions as suitable models to investigate skeletal muscle memory in humans. We believe that understanding the 'epi'-memory of skeletal muscle will enable the next generation of targeted therapies to promote muscle growth and reduce muscle loss to enable healthy aging. © 2016 The Authors. Aging Cell published by the Anatomical Society and John Wiley & Sons Ltd.

Cluster-based analysis improves predictive validity of spike-triggered receptive field estimates

PubMed Central

Malone, Brian J.

2017-01-01

Spectrotemporal receptive field (STRF) characterization is a central goal of auditory physiology. STRFs are often approximated by the spike-triggered average (STA), which reflects the average stimulus preceding a spike. In many cases, the raw STA is subjected to a threshold defined by gain values expected by chance. However, such correction methods have not been universally adopted, and the consequences of specific gain-thresholding approaches have not been investigated systematically. Here, we evaluate two classes of statistical correction techniques, using the resulting STRF estimates to predict responses to a novel validation stimulus. The first, more traditional technique eliminated STRF pixels (time-frequency bins) with gain values expected by chance. This correction method yielded significant increases in prediction accuracy, including when the threshold setting was optimized for each unit. The second technique was a two-step thresholding procedure wherein clusters of contiguous pixels surviving an initial gain threshold were then subjected to a cluster mass threshold based on summed pixel values. This approach significantly improved upon even the best gain-thresholding techniques. Additional analyses suggested that allowing threshold settings to vary independently for excitatory and inhibitory subfields of the STRF resulted in only marginal additional gains, at best. In summary, augmenting reverse correlation techniques with principled statistical correction choices increased prediction accuracy by over 80% for multi-unit STRFs and by over 40% for single-unit STRFs, furthering the interpretational relevance of the recovered spectrotemporal filters for auditory systems analysis. PMID:28877194

Response of cat cerebellar vermis induced by sound. I. Influence of drugs on responses of single units.

PubMed

Jastreboff, P J; Tarnecki, R

1975-01-01

Experiments were done on the cats under Chloralose and/or Nembutal anesthesia. A click was used as a standard acoustic stimulus. The type of responses of single units from cerebellar vermis lobuli V-VII were analyzed. At least four different types of single unit reactions were observed and one of these - oscillatory - was produced by the presence of Flaxedil simultaneously with Chloralose. The system that controls the activity of the middle-ear-muscles can be suspected as the source of the oscillatory pattern of the cerebellar response. Latencies were found to be constant, independent of anesthesia, but it was necessary to have a low level of Nembutal anesthesia because of the overriding inhibitory influence of Nembutal.

Septicemia during compromised host treated in a protected isolation unit.

PubMed

Nagao, T; Watanabe, K; Komatsuda, M; Arimori, S; Sawamura, S; Ozawa, A; Shotsu, A; Sasaki, S

1980-01-01

Bacteriological, hematological and immunological data were evaluated in patients with septicemia in a protected isolation unit. Patients were randomly given antimicrobial prophylaxis. Three out of four episodes of septicemia occurred 2 to 4 days after discontinuing oral nonabsorbed antibiotics at the stage of leukopenia and immunodeficiency induced by chemotherapy. Death occurred within 10 days in two patients whose peripheral white blood counts did not recover. In the other patients sepricemia was suppressed and complete remission was achieved in one of them. Parentheral administration of antibiotics is necessary after discontinuing oral prophylactic antibiotics in a protected isolation unit.

A New Approach to Model Pitch Perception Using Sparse Coding

PubMed Central

Furst, Miriam; Barak, Omri

2017-01-01

Our acoustical environment abounds with repetitive sounds, some of which are related to pitch perception. It is still unknown how the auditory system, in processing these sounds, relates a physical stimulus and its percept. Since, in mammals, all auditory stimuli are conveyed into the nervous system through the auditory nerve (AN) fibers, a model should explain the perception of pitch as a function of this particular input. However, pitch perception is invariant to certain features of the physical stimulus. For example, a missing fundamental stimulus with resolved or unresolved harmonics, or a low and high-level amplitude stimulus with the same spectral content–these all give rise to the same percept of pitch. In contrast, the AN representations for these different stimuli are not invariant to these effects. In fact, due to saturation and non-linearity of both cochlear and inner hair cells responses, these differences are enhanced by the AN fibers. Thus there is a difficulty in explaining how pitch percept arises from the activity of the AN fibers. We introduce a novel approach for extracting pitch cues from the AN population activity for a given arbitrary stimulus. The method is based on a technique known as sparse coding (SC). It is the representation of pitch cues by a few spatiotemporal atoms (templates) from among a large set of possible ones (a dictionary). The amount of activity of each atom is represented by a non-zero coefficient, analogous to an active neuron. Such a technique has been successfully applied to other modalities, particularly vision. The model is composed of a cochlear model, an SC processing unit, and a harmonic sieve. We show that the model copes with different pitch phenomena: extracting resolved and non-resolved harmonics, missing fundamental pitches, stimuli with both high and low amplitudes, iterated rippled noises, and recorded musical instruments. PMID:28099436

A New Approach to Model Pitch Perception Using Sparse Coding.

PubMed

Barzelay, Oded; Furst, Miriam; Barak, Omri

2017-01-01

Our acoustical environment abounds with repetitive sounds, some of which are related to pitch perception. It is still unknown how the auditory system, in processing these sounds, relates a physical stimulus and its percept. Since, in mammals, all auditory stimuli are conveyed into the nervous system through the auditory nerve (AN) fibers, a model should explain the perception of pitch as a function of this particular input. However, pitch perception is invariant to certain features of the physical stimulus. For example, a missing fundamental stimulus with resolved or unresolved harmonics, or a low and high-level amplitude stimulus with the same spectral content-these all give rise to the same percept of pitch. In contrast, the AN representations for these different stimuli are not invariant to these effects. In fact, due to saturation and non-linearity of both cochlear and inner hair cells responses, these differences are enhanced by the AN fibers. Thus there is a difficulty in explaining how pitch percept arises from the activity of the AN fibers. We introduce a novel approach for extracting pitch cues from the AN population activity for a given arbitrary stimulus. The method is based on a technique known as sparse coding (SC). It is the representation of pitch cues by a few spatiotemporal atoms (templates) from among a large set of possible ones (a dictionary). The amount of activity of each atom is represented by a non-zero coefficient, analogous to an active neuron. Such a technique has been successfully applied to other modalities, particularly vision. The model is composed of a cochlear model, an SC processing unit, and a harmonic sieve. We show that the model copes with different pitch phenomena: extracting resolved and non-resolved harmonics, missing fundamental pitches, stimuli with both high and low amplitudes, iterated rippled noises, and recorded musical instruments.

A method for real-time visual stimulus selection in the study of cortical object perception

PubMed Central

Leeds, Daniel D.; Tarr, Michael J.

2016-01-01

The properties utilized by visual object perception in the mid- and high-level ventral visual pathway are poorly understood. To better establish and explore possible models of these properties, we adopt a data-driven approach in which we repeatedly interrogate neural units using functional Magnetic Resonance Imaging (fMRI) to establish each unit’s image selectivity. This approach to imaging necessitates a search through a broad space of stimulus properties using a limited number of samples. To more quickly identify the complex visual features underlying human cortical object perception, we implemented a new functional magnetic resonance imaging protocol in which visual stimuli are selected in real-time based on BOLD responses to recently shown images. Two variations of this protocol were developed, one relying on natural object stimuli and a second based on synthetic object stimuli, both embedded in feature spaces based on the complex visual properties of the objects. During fMRI scanning, we continuously controlled stimulus selection in the context of a real-time search through these image spaces in order to maximize neural responses across predetermined 1 cm3 brain regions. Elsewhere we have reported the patterns of cortical selectivity revealed by this approach (Leeds 2014). In contrast, here our objective is to present more detailed methods and explore the technical and biological factors influencing the behavior of our real-time stimulus search. We observe that: 1) Searches converged more reliably when exploring a more precisely parameterized space of synthetic objects; 2) Real-time estimation of cortical responses to stimuli are reasonably consistent; 3) Search behavior was acceptably robust to delays in stimulus displays and subject motion effects. Overall, our results indicate that real-time fMRI methods may provide a valuable platform for continuing study of localized neural selectivity, both for visual object representation and beyond. PMID:26973168

Modification of persistent responses in medial prefrontal cortex during learning in trace eyeblink conditioning

PubMed Central

2014-01-01

Persistent spiking in response to a discrete stimulus is considered to reflect the active maintenance of a memory for that stimulus until a behavioral response is made. This response pattern has been reported in learning paradigms that impose a temporal gap between stimulus presentation and behavioral response, including trace eyeblink conditioning. However, it is unknown whether persistent responses are acquired as a function of learning or simply represent an already existing category of response type. This fundamental question was addressed by recording single-unit activity in the medial prefrontal cortex (mPFC) of rabbits during the initial learning phase of trace eyeblink conditioning. Persistent responses to the tone conditioned stimulus were observed in the mPFC during the very first training sessions. Further analysis revealed that most cells with persistent responses showed this pattern during the very first training trial, before animals had experienced paired training. However, persistent cells showed reliable decreases in response magnitude over the first training session, which were not observed on the second day of training or for sessions in which learning criterion was met. This modification of response magnitude was specific to persistent responses and was not observed for cells showing phasic tone-evoked responses. The data suggest that persistent responses to discrete stimuli do not require learning but that the ongoing robustness of such responses over the course of training is modified as a result of experience. Putative mechanisms for this modification are discussed, including changes in cellular or network properties, neuromodulatory tone, and/or the synaptic efficacy of tone-associated inputs. PMID:25080570

Induction and modulation of persistent activity in a layer V PFC microcircuit model

PubMed Central

Papoutsi, Athanasia; Sidiropoulou, Kyriaki; Cutsuridis, Vassilis; Poirazi, Panayiota

2013-01-01

Working memory refers to the temporary storage of information and is strongly associated with the prefrontal cortex (PFC). Persistent activity of cortical neurons, namely the activity that persists beyond the stimulus presentation, is considered the cellular correlate of working memory. Although past studies suggested that this type of activity is characteristic of large scale networks, recent experimental evidence imply that small, tightly interconnected clusters of neurons in the cortex may support similar functionalities. However, very little is known about the biophysical mechanisms giving rise to persistent activity in small-sized microcircuits in the PFC. Here, we present a detailed biophysically—yet morphologically simplified—microcircuit model of layer V PFC neurons that incorporates connectivity constraints and is validated against a multitude of experimental data. We show that (a) a small-sized network can exhibit persistent activity under realistic stimulus conditions. (b) Its emergence depends strongly on the interplay of dADP, NMDA, and GABAB currents. (c) Although increases in stimulus duration increase the probability of persistent activity induction, variability in the stimulus firing frequency does not consistently influence it. (d) Modulation of ionic conductances (Ih, ID, IsAHP, IcaL, IcaN, IcaR) differentially controls persistent activity properties in a location dependent manner. These findings suggest that modulation of the microcircuit's firing characteristics is achieved primarily through changes in its intrinsic mechanism makeup, supporting the hypothesis of multiple bi-stable units in the PFC. Overall, the model generates a number of experimentally testable predictions that may lead to a better understanding of the biophysical mechanisms of persistent activity induction and modulation in the PFC. PMID:24130519

Temporal variability of spectro-temporal receptive fields in the anesthetized auditory cortex.

PubMed

Meyer, Arne F; Diepenbrock, Jan-Philipp; Ohl, Frank W; Anemüller, Jörn

2014-01-01

Temporal variability of neuronal response characteristics during sensory stimulation is a ubiquitous phenomenon that may reflect processes such as stimulus-driven adaptation, top-down modulation or spontaneous fluctuations. It poses a challenge to functional characterization methods such as the receptive field, since these often assume stationarity. We propose a novel method for estimation of sensory neurons' receptive fields that extends the classic static linear receptive field model to the time-varying case. Here, the long-term estimate of the static receptive field serves as the mean of a probabilistic prior distribution from which the short-term temporally localized receptive field may deviate stochastically with time-varying standard deviation. The derived corresponding generalized linear model permits robust characterization of temporal variability in receptive field structure also for highly non-Gaussian stimulus ensembles. We computed and analyzed short-term auditory spectro-temporal receptive field (STRF) estimates with characteristic temporal resolution 5-30 s based on model simulations and responses from in total 60 single-unit recordings in anesthetized Mongolian gerbil auditory midbrain and cortex. Stimulation was performed with short (100 ms) overlapping frequency-modulated tones. Results demonstrate identification of time-varying STRFs, with obtained predictive model likelihoods exceeding those from baseline static STRF estimation. Quantitative characterization of STRF variability reveals a higher degree thereof in auditory cortex compared to midbrain. Cluster analysis indicates that significant deviations from the long-term static STRF are brief, but reliably estimated. We hypothesize that the observed variability more likely reflects spontaneous or state-dependent internal fluctuations that interact with stimulus-induced processing, rather than experimental or stimulus design.

Hallucinogens as discriminative stimuli in animals: LSD, phenethylamines, and tryptamines.

PubMed

Winter, J C

2009-04-01

Although man's first encounters with hallucinogens predate written history, it was not until the rise of the sister disciplines of organic chemistry and pharmacology in the nineteenth century that scientific studies became possible. Mescaline was the first to be isolated and its chemical structure determined. Since then, additional drugs have been recovered from their natural sources and synthetic chemists have contributed many more. Given their profound effects upon human behavior and the need for verbal communication to access many of these effects, some see humans as ideal subjects for study of hallucinogens. However, if we are to determine the mechanisms of action of these agents, establish hypotheses testable in human subjects, and explore the mechanistic links between hallucinogens and such apparently disparate topics as idiopathic psychosis, transcendental states, drug abuse, stress disorders, and cognitive dysfunction, studies in animals are essential. Stimulus control by hallucinogens has provided an intuitively attractive approach to the study of these agents in nonverbal species. The intent of this review is to provide a brief account of events from the time of the first demonstration of hallucinogen-induced stimulus control to the present. In general, the review is limited to lysergic acid diethylamide (LSD) and the hallucinogenic derivatives of phenethylamine and tryptamine. The pharmacological basis for stimulus control by LSD and hallucinogenic phenethylamines and tryptamines is serotonergic in nature. The 5-HT(2A) receptor appears to be the primary site of action with significant modulation by other serotonergic sites including 5-HT(2C) and 5-HT(1A) receptors. Interactions with other neurotransmitters, especially glutamate and dopamine, are under active investigation. Most studies to date have been conducted in the rat but transgenic mice offer interesting possibilities. Hallucinogen-induced stimulus control provides a unique behavioral tool for the prediction of subjective effects in man and for the elucidation of the pharmacological mechanisms of the action of these agents.

Single-Trial Analysis of V1 Responses Suggests Two Transmission States

NASA Technical Reports Server (NTRS)

Shah, A. S.; Knuth, K. H.; Truccolo, W. A.; Mehta, A. D.; McGinnis, T.; OConnell, N.; Ding, M.; Bressler, S. L.; Schroeder, C. E.

2002-01-01

Sensory processing in the visual, auditory, and somatosensory systems is often studied by recording electrical activity in response to a stimulus of interest. Typically, multiple trial responses to the stimulus are averaged to isolate the stereotypic response from noise. However, averaging ignores dynamic variability in the neuronal response, which is potentially critical to understanding stimulus-processing schemes. Thus, we developed the multiple component, Event-Related Potential (mcERP) model. This model asserts that multiple components, defined as stereotypic waveforms, comprise the stimulus-evoked response and that these components may vary in amplitude and latency from trial to trial. Application of this model to data recorded simultaneously from all six laminae of V1 in an awake, behaving monkey performing a visual discrimination yielded three components. The first component localized to granular V1, the second was located in supragranular V1, and the final component displayed a multi-laminar distribution. These modeling results, which take into account single-trial response dynamics, illustrated that the initial activation of VI occurs in the granular layer followed by activation in the supragranular layers. This finding is expected because the average response in those layers demonstrates the same progression and because anatomical evidence suggests that the feedforward input in V1 enters the granular layer and progresses to supragranular layers. In addition to these findings, the granular component of the model displayed several interesting trial-to-trial characteristics including (1) a bimodal latency distribution, (2) a latency-related variation in response amplitude, (3) a latency correlation with the supragranular component, and (4) an amplitude and latency association with the multi-laminar component. Direct analyses of the single-trial data were consistent with these model predictions. These findings suggest that V1 has at least 2 transmission states, which may be modulated by various effects such as attention, dynamics in local EEG rhythm, or variation in sensory inputs.

Effects of a cochlear implant simulation on immediate memory in normal-hearing adults

PubMed Central

Burkholder, Rose A.; Pisoni, David B.; Svirsky, Mario A.

2012-01-01

This study assessed the effects of stimulus misidentification and memory processing errors on immediate memory span in 25 normal-hearing adults exposed to degraded auditory input simulating signals provided by a cochlear implant. The identification accuracy of degraded digits in isolation was measured before digit span testing. Forward and backward digit spans were shorter when digits were degraded than when they were normal. Participants’ normal digit spans and their accuracy in identifying isolated digits were used to predict digit spans in the degraded speech condition. The observed digit spans in degraded conditions did not differ significantly from predicted digit spans. This suggests that the decrease in memory span is related primarily to misidentification of digits rather than memory processing errors related to cognitive load. These findings provide complementary information to earlier research on auditory memory span of listeners exposed to degraded speech either experimentally or as a consequence of a hearing-impairment. PMID:16317807

Nanowire sensor, sensor array, and method for making the same

NASA Technical Reports Server (NTRS)

Homer, Margie (Inventor); Fleurial, Jean-Pierre (Inventor); Bugga, Ratnakumar (Inventor); Vasquez, Richard (Inventor); Yun, Minhee (Inventor); Myung, Nosang (Inventor); Choi, Daniel (Inventor); Goddard, William (Inventor); Ryan, Margaret (Inventor); Yen, Shiao-Pin (Inventor)

2012-01-01

The present invention relates to a nanowire sensor and method for forming the same. More specifically, the nanowire sensor comprises at least one nanowire formed on a substrate, with a sensor receptor disposed on a surface of the nanowire, thereby forming a receptor-coated nanowire. The nanowire sensor can be arranged as a sensor sub-unit comprising a plurality of homogeneously receptor-coated nanowires. A plurality of sensor subunits can be formed to collectively comprise a nanowire sensor array. Each sensor subunit in the nanowire sensor array can be formed to sense a different stimulus, allowing a user to sense a plurality of stimuli. Additionally, each sensor subunit can be formed to sense the same stimuli through different aspects of the stimulus. The sensor array is fabricated through a variety of techniques, such as by creating nanopores on a substrate and electrodepositing nanowires within the nanopores.

Identification of a Plasmid-Mediated Quinolone Resistance Gene in Salmonella Isolates from Texas Dairy Farm Environmental Samples.

PubMed

Cummings, K J; Rodriguez-Rivera, L D; Norman, K N; Ohta, N; Scott, H M

2017-06-01

A recent increase in plasmid-mediated quinolone resistance (PMQR) has been detected among Salmonella isolated from humans in the United States, and it is necessary to determine the sources of human infection. We had previously isolated Salmonella from dairy farm environmental samples collected in Texas, and isolates were tested for anti-microbial susceptibility. Two isolates, serotyped as Salmonella Muenster, showed the discordant pattern of nalidixic acid susceptibility and intermediate susceptibility to ciprofloxacin. For this project, whole-genome sequencing of both isolates was performed to detect genes associated with quinolone resistance. The plasmid-mediated qnrB19 gene and IncR plasmid type were identified in both isolates. To our knowledge, this is the first report of PMQR in Salmonella isolated from food animals or agricultural environments in the United States. © 2016 Blackwell Verlag GmbH.

Suppression of bulboreticular unit responses to noxious stimuli by analgesic mesencephalic stimulation.

PubMed

Morrow, T J; Casey, K L

1983-01-01

The responses of 302 neurons in the medial medullary reticular formation (MRF) to a variety of noxious and innocuous somatic stimuli were studied in anesthetized and awake rats. In addition, the effects of analgesic electrical stimulation in the mesencephalon (MES) on unit responses were examined. Tail shock was the most effective stimulus, exciting more than 80% of all units recorded. This stimulus was considered separately during data analysis, since it could not be classified as noxious or innocuous. Noxious somatic stimuli (including pinch, firm pressure, pin prick, and radiant heating of the tail above 45 degrees C were especially effective in eliciting discharge in a significant fraction of all cells in both awake (123/205) and anesthetized (45/97) animals. Nociceptive neurons could be classified as nociceptive specific (NS) or wide dynamic range (WDR) depending on their responses to all somatic stimuli tested. Nociceptive neurons showed no preferential anatomical distribution. Most neurons, including those responsive to noxious inputs, exhibited large, often bilateral receptive fields which frequently covered the tail, one or more limbs, and extensive areas of the body or head. Electrical stimulation within or adjacent to the mesencephalic periaqueductal gray matter depressed the spontaneous and evoked discharge of MRF neurons in both acute and chronic preparations. This inhibition showed a significant preference (p less than 0.001, chi-square statistic) for units that were excited by somatic and especially noxious stimuli. No units were facilitated by MES stimulation. In the awake rat, unit suppression closely followed the time course and level of MES-induced analgesia. Excitability data from the acute experiments suggest that this response inhibition may be the result of a direct action on MRF neurons. Anesthesia severely depressed the spontaneous discharge of MRF neurons as well as the activity evoked by innocuous somatic stimulation. Our data suggest that analgesia produced by MES stimulation is at least in part due to the depression of MRF unit activity, and support the hypothesis that MRF neurons play a critical role in the mediation of behavioral responses to noxious stimuli.

On the origins of naming and other symbolic behavior

PubMed Central

Horne, Pauline J.; Lowe, C. Fergus

1996-01-01

We identify naming as the basic unit of verbal behavior, describe the conditions under which it is learned, and outline its crucial role in the development of stimulus classes and, hence, of symbolic behavior. Drawing upon B. F. Skinner's functional analysis and the theoretical work of G. H. Mead and L. S. Vygotsky, we chart how a child, through learning listener behavior and then echoic responding, learns bidirectional relations between classes of objects or events and his or her own speaker-listener behavior, thus acquiring naming—a higher order behavioral relation. Once established, the bidirectionality incorporated in naming extends across behavior classes such as those identified by Skinner as the mand, tact, and intraverbal so that each becomes a variant of the name relation. We indicate how our account informs the specification of rule-governed behavior and provides the basis for an experimental analysis of symbolic behavior. Furthermore, because naming is both evoked by, and itself evokes, classes of events it brings about new or emergent behavior such as that reported in studies of stimulus equivalence. This account is supported by data from a wide range of match-to-sample studies that also provide evidence that stimulus equivalence in humans is not a unitary phenomenon but the outcome of a number of different types of naming behavior. PMID:16812780

The absolute threshold of cone vision

PubMed Central

Koeing, Darran; Hofer, Heidi

2013-01-01

We report measurements of the absolute threshold of cone vision, which has been previously underestimated due to sub-optimal conditions or overly strict subjective response criteria. We avoided these limitations by using optimized stimuli and experimental conditions while having subjects respond within a rating scale framework. Small (1′ fwhm), brief (34 msec), monochromatic (550 nm) stimuli were foveally presented at multiple intensities in dark-adapted retina for 5 subjects. For comparison, 4 subjects underwent similar testing with rod-optimized stimuli. Cone absolute threshold, that is, the minimum light energy for which subjects were just able to detect a visual stimulus with any response criterion, was 203 ± 38 photons at the cornea, ∼0.47 log units lower than previously reported. Two-alternative forced-choice measurements in a subset of subjects yielded consistent results. Cone thresholds were less responsive to criterion changes than rod thresholds, suggesting a limit to the stimulus information recoverable from the cone mosaic in addition to the limit imposed by Poisson noise. Results were consistent with expectations for detection in the face of stimulus uncertainty. We discuss implications of these findings for modeling the first stages of human cone vision and interpreting psychophysical data acquired with adaptive optics at the spatial scale of the receptor mosaic. PMID:21270115

Reward Inference by Primate Prefrontal and Striatal Neurons

PubMed Central

Pan, Xiaochuan; Fan, Hongwei; Sawa, Kosuke; Tsuda, Ichiro; Tsukada, Minoru

2014-01-01

The brain contains multiple yet distinct systems involved in reward prediction. To understand the nature of these processes, we recorded single-unit activity from the lateral prefrontal cortex (LPFC) and the striatum in monkeys performing a reward inference task using an asymmetric reward schedule. We found that neurons both in the LPFC and in the striatum predicted reward values for stimuli that had been previously well experienced with set reward quantities in the asymmetric reward task. Importantly, these LPFC neurons could predict the reward value of a stimulus using transitive inference even when the monkeys had not yet learned the stimulus–reward association directly; whereas these striatal neurons did not show such an ability. Nevertheless, because there were two set amounts of reward (large and small), the selected striatal neurons were able to exclusively infer the reward value (e.g., large) of one novel stimulus from a pair after directly experiencing the alternative stimulus with the other reward value (e.g., small). Our results suggest that although neurons that predict reward value for old stimuli in the LPFC could also do so for new stimuli via transitive inference, those in the striatum could only predict reward for new stimuli via exclusive inference. Moreover, the striatum showed more complex functions than was surmised previously for model-free learning. PMID:24453328

Augmented Hebbian reweighting accounts for accuracy and induced bias in perceptual learning with reverse feedback

PubMed Central

Liu, Jiajuan; Dosher, Barbara Anne; Lu, Zhong-Lin

2015-01-01

Using an asymmetrical set of vernier stimuli (−15″, −10″, −5″, +10″, +15″) together with reverse feedback on the small subthreshold offset stimulus (−5″) induces response bias in performance (Aberg & Herzog, 2012; Herzog, Eward, Hermens, & Fahle, 2006; Herzog & Fahle, 1999). These conditions are of interest for testing models of perceptual learning because the world does not always present balanced stimulus frequencies or accurate feedback. Here we provide a comprehensive model for the complex set of asymmetric training results using the augmented Hebbian reweighting model (Liu, Dosher, & Lu, 2014; Petrov, Dosher, & Lu, 2005, 2006) and the multilocation integrated reweighting theory (Dosher, Jeter, Liu, & Lu, 2013). The augmented Hebbian learning algorithm incorporates trial-by-trial feedback, when present, as another input to the decision unit and uses the observer's internal response to update the weights otherwise; block feedback alters the weights on bias correction (Liu et al., 2014). Asymmetric training with reversed feedback incorporates biases into the weights between representation and decision. The model correctly predicts the basic induction effect, its dependence on trial-by-trial feedback, and the specificity of bias to stimulus orientation and spatial location, extending the range of augmented Hebbian reweighting accounts of perceptual learning. PMID:26418382

Augmented Hebbian reweighting accounts for accuracy and induced bias in perceptual learning with reverse feedback.

PubMed

Liu, Jiajuan; Dosher, Barbara Anne; Lu, Zhong-Lin

2015-01-01

Using an asymmetrical set of vernier stimuli (-15″, -10″, -5″, +10″, +15″) together with reverse feedback on the small subthreshold offset stimulus (-5″) induces response bias in performance (Aberg & Herzog, 2012; Herzog, Eward, Hermens, & Fahle, 2006; Herzog & Fahle, 1999). These conditions are of interest for testing models of perceptual learning because the world does not always present balanced stimulus frequencies or accurate feedback. Here we provide a comprehensive model for the complex set of asymmetric training results using the augmented Hebbian reweighting model (Liu, Dosher, & Lu, 2014; Petrov, Dosher, & Lu, 2005, 2006) and the multilocation integrated reweighting theory (Dosher, Jeter, Liu, & Lu, 2013). The augmented Hebbian learning algorithm incorporates trial-by-trial feedback, when present, as another input to the decision unit and uses the observer's internal response to update the weights otherwise; block feedback alters the weights on bias correction (Liu et al., 2014). Asymmetric training with reversed feedback incorporates biases into the weights between representation and decision. The model correctly predicts the basic induction effect, its dependence on trial-by-trial feedback, and the specificity of bias to stimulus orientation and spatial location, extending the range of augmented Hebbian reweighting accounts of perceptual learning.

Application of DNA probes for rRNA and vanA genes to investigation of a nosocomial cluster of vancomycin-resistant enterococci.

PubMed Central

Woodford, N; Morrison, D; Johnson, A P; Briant, V; George, R C; Cookson, B

1993-01-01

DNA probes specific for genes encoding rRNA and the glycopeptide resistance gene vanA were used to investigate a cluster of vancomycin-resistant (MICs, > 512 mg/liter) Enterococcus faecalis and Enterococcus faecium isolated from separate patients in a renal unit in a London hospital. When digested with BamHI, 12 of 13 vancomycin-resistant E. faecalis isolates exhibited a common restriction fragment length polymorphism pattern of rRNA genes (ribotype). A vanA probe hybridized with chromosomal DNA in these 12 isolates. The other isolate of vancomycin-resistant E. faecalis had a different ribotype and the vanA gene was located on plasmid DNA. These data suggest that cross-infection with a single strain of vancomycin-resistant E. faecalis occurred in most instances. In contrast, 23 vancomycin-resistant E. faecium isolates showed greater heterogeneity, comprising 8 ribotypes, suggesting that multiple strains were present in the unit. Twenty-one of these 23 isolates harbored a 24-MDa plasmid which hybridized with the vanA probe, implying that interstrain dissemination of a vancomycin resistance plasmid may have occurred among E. faecium isolates in the renal unit. Images PMID:8096216

Hardware interface for isolation of vibrations in flexible manipulators: Development and applications

NASA Technical Reports Server (NTRS)

Manouchehri, Davoud; Lindsay, Thomas; Ghosh, David

1994-01-01

NASA's Langley Research Center (LaRC) is addressing the problem of isolating the vibrations of the Shuttle remote manipulator system (RMS) from its end-effector and/or payload by modeling an RMS flat-floor simulator with a dynamic payload. Analysis of the model can lead to control techniques that will improve the speed, accuracy, and safety of the RMS in capturing satellites and eventually facilitate berthing with the space station. Rockwell International Corporation, also involved in vibration isolation, has developed a hardware interface unit to isolate the end-effector from the vibrations of an arm on a Shuttle robotic tile processing system (RTPS). To apply the RTPS isolation techniques to long-reach arms like the RMS, engineers have modeled the dynamics of the hardware interface unit with simulation software. By integrating the Rockwell interface model with the NASA LaRC RMS simulator model, investigators can study the use of a hardware interface to isolate dynamic payloads from the RMS. The interface unit uses both active and passive compliance and damping for vibration isolation. Thus equipped, the RMS could be used as a telemanipulator with control characteristics for capture and berthing operations. The hardware interface also has applications in industry.

A comparison of methods for teaching receptive language to toddlers with autism.

PubMed

Vedora, Joseph; Grandelski, Katrina

2015-01-01

The use of a simple-conditional discrimination training procedure, in which stimuli are initially taught in isolation with no other comparison stimuli, is common in early intensive behavioral intervention programs. Researchers have suggested that this procedure may encourage the development of faulty stimulus control during training. The current study replicated previous work that compared the simple-conditional and the conditional-only methods to teach receptive labeling of pictures to young children with autism spectrum disorder. Both methods were effective, but the conditional-only method required fewer sessions to mastery. © Society for the Experimental Analysis of Behavior.

Measuring the motor output of the pontomedullary reticular formation in the monkey: do stimulus-triggered averaging and stimulus trains produce comparable results in the upper limbs?

PubMed

Herbert, Wendy J; Davidson, Adam G; Buford, John A

2010-06-01

The pontomedullary reticular formation (PMRF) of the monkey produces motor outputs to both upper limbs. EMG effects evoked from stimulus-triggered averaging (StimulusTA) were compared with effects from stimulus trains to determine whether both stimulation methods produced comparable results. Flexor and extensor muscles of scapulothoracic, shoulder, elbow, and wrist joints were studied bilaterally in two male M. fascicularis monkeys trained to perform a bilateral reaching task. The frequency of facilitation versus suppression responses evoked in the muscles was compared between methods. Stimulus trains were more efficient (94% of PMRF sites) in producing responses than StimulusTA (55%), and stimulus trains evoked responses from more muscles per site than from StimulusTA. Facilitation (72%) was more common from stimulus trains than StimulusTA (39%). In the overall results, a bilateral reciprocal activation pattern of ipsilateral flexor and contralateral extensor facilitation was evident for StimulusTA and stimulus trains. When the comparison was restricted to cases where both methods produced a response in a given muscle from the same site, agreement was very high, at 80%. For the remaining 20%, discrepancies were accounted for mainly by facilitation from stimulus trains when StimulusTA produced suppression, which was in agreement with the under-representation of suppression in the stimulus train data as a whole. To the extent that the stimulus train method may favor transmission through polysynaptic pathways, these results suggest that polysynaptic pathways from the PMRF more often produce facilitation in muscles that would typically demonstrate suppression with StimulusTA.

Characterizing Response to Elemental Unit of Acoustic Imaging Noise: An fMRI Study

PubMed Central

Luh, Wen-Ming; Talavage, Thomas M.

2010-01-01

Acoustic imaging noise produced during functional magnetic resonance imaging (fMRI) studies can hinder auditory fMRI research analysis by altering the properties of the acquired time-series data. Acoustic imaging noise can be especially confounding when estimating the time course of the hemodynamic response (HDR) in auditory event-related fMRI (fMRI) experiments. This study is motivated by the desire to establish a baseline function that can serve not only as a comparison to other quantities of acoustic imaging noise for determining how detrimental is one's experimental noise, but also as a foundation for a model that compensates for the response to acoustic imaging noise. Therefore, the amplitude and spatial extent of the HDR to the elemental unit of acoustic imaging noise (i.e., a single ping) associated with echoplanar acquisition were characterized and modeled. Results from this fMRI study at 1.5 T indicate that the group-averaged HDR in left and right auditory cortex to acoustic imaging noise (duration of 46 ms) has an estimated peak magnitude of 0.29% (right) to 0.48% (left) signal change from baseline, peaks between 3 and 5 s after stimulus presentation, and returns to baseline and remains within the noise range approximately 8 s after stimulus presentation. PMID:19304477

Prevalence of factor H-binding protein variants and NadA among meningococcal group B isolates from the United States: implications for the development of a multicomponent group B vaccine.

PubMed

Beernink, Peter T; Welsch, Jo Anne; Harrison, Lee H; Leipus, Arunas; Kaplan, Sheldon L; Granoff, Dan M

2007-05-15

Two promising recombinant meningococcal protein vaccines are in development. One contains factor H-binding protein (fHBP) variants (v.) 1 and 2, whereas the other contains v.1 and 4 other antigens discovered by genome mining (5 component [5C]). Antibodies against fHBP are bactericidal against strains within a variant group. There are limited data on the prevalence of strains expressing different fHBP variants in the United States. A total of 143 group B isolates from patients hospitalized in the United States were tested for fHBP variant by quantitative polymerase chain reaction, for reactivity with 6 anti-fHBP monoclonal antibodies (MAb) by dot immunoblotting, and for susceptibility to bactericidal activity of mouse antisera. fHBP v.1 isolates predominated in California (83%), whereas isolates expressing v.1 (53%) or v.2 (42%) were common in 9 other states. Isolates representative of 5 anti-fHBP MAb-binding phenotypes (70% of isolates) were highly susceptible to anti-fHBP v.1 or v.2 bactericidal activity, whereas 3 phenotypes were approximately 50% susceptible. Collectively, antibodies against the fHBP v.1 and v.2 vaccine and the 5C vaccine killed 76% and 83% of isolates, respectively. Susceptibility to bactericidal activity can be predicted, in part, on the basis of fHBP phenotypes. Both vaccines have the potential to prevent most group B disease in the United States.

H-theorem and Maxwell demon in quantum physics

NASA Astrophysics Data System (ADS)

Kirsanov, N. S.; Lebedev, A. V.; Sadovskyy, I. A.; Suslov, M. V.; Vinokur, V. M.; Blatter, G.; Lesovik, G. B.

2018-02-01

The Second Law of Thermodynamics states that temporal evolution of an isolated system occurs with non-diminishing entropy. In quantum realm, this holds for energy-isolated systems the evolution of which is described by the so-called unital quantum channel. The entropy of a system evolving in a non-unital quantum channel can, in principle, decrease. We formulate a general criterion of unitality for the evolution of a quantum system, enabling a simple and rigorous approach for finding and identifying the processes accompanied by decreasing entropy in energy-isolated systems. We discuss two examples illustrating our findings, the quantum Maxwell demon and heating-cooling process within a two-qubit system.

Robust tactile sensory responses in finger area of primate motor cortex relevant to prosthetic control

NASA Astrophysics Data System (ADS)

Schroeder, Karen E.; Irwin, Zachary T.; Bullard, Autumn J.; Thompson, David E.; Bentley, J. Nicole; Stacey, William C.; Patil, Parag G.; Chestek, Cynthia A.

2017-08-01

Objective. Challenges in improving the performance of dexterous upper-limb brain-machine interfaces (BMIs) have prompted renewed interest in quantifying the amount and type of sensory information naturally encoded in the primary motor cortex (M1). Previous single unit studies in monkeys showed M1 is responsive to tactile stimulation, as well as passive and active movement of the limbs. However, recent work in this area has focused primarily on proprioception. Here we examined instead how tactile somatosensation of the hand and fingers is represented in M1. Approach. We recorded multi- and single units and thresholded neural activity from macaque M1 while gently brushing individual finger pads at 2 Hz. We also recorded broadband neural activity from electrocorticogram (ECoG) grids placed on human motor cortex, while applying the same tactile stimulus. Main results. Units displaying significant differences in firing rates between individual fingers (p  <  0.05) represented up to 76.7% of sorted multiunits across four monkeys. After normalizing by the number of channels with significant motor finger responses, the percentage of electrodes with significant tactile responses was 74.9%  ±  24.7%. No somatotopic organization of finger preference was obvious across cortex, but many units exhibited cosine-like tuning across multiple digits. Sufficient sensory information was present in M1 to correctly decode stimulus position from multiunit activity above chance levels in all monkeys, and also from ECoG gamma power in two human subjects. Significance. These results provide some explanation for difficulties experienced by motor decoders in clinical trials of cortically controlled prosthetic hands, as well as the general problem of disentangling motor and sensory signals in primate motor cortex during dextrous tasks. Additionally, examination of unit tuning during tactile and proprioceptive inputs indicates cells are often tuned differently in different contexts, reinforcing the need for continued refinement of BMI training and decoding approaches to closed-loop BMI systems for dexterous grasping.

Differential activation of motor units in the wrist extensor muscles during the tonic vibration reflex in man.

PubMed Central

Romaiguère, P; Vedel, J P; Azulay, J P; Pagni, S

1991-01-01

1. Single motor unit activity was recorded in the extensor carpi radialis longus and extensor carpi radialis brevis muscles of five healthy human subjects, using metal microelectrodes. 2. Motor units were characterized on the basis of their twitch contraction times and their force recruitment thresholds during voluntary imposed-ramp contractions. 3. The discharge patterns of forty-three motor units were studied during tonic vibration reflex elicited by prolonged (150 s) trains of vibration (30 Hz) applied to the distal tendons of the muscles. The temporal relationships between the individual small tendon taps of the vibratory stimulus and the motor unit impulses were analysed on dot raster displays and post-stimulus time histograms. 4. After tendon taps, the impulses of motor units with long twitch contraction times (mean +/- S.D., 47.2 +/- 10.7 ms) and low recruitment thresholds (0.88 +/- 0.6 N) formed a single narrow peak (P1) with a latency (22.7 +/- 1.4 ms) which was comparable to that of the tendon jerk in the extensor carpi radialis muscles. These motor units were named 'P1 units'. On the other hand, the response of motor units with shorter twitch contraction times (31.1 +/- 3.3 ms) and higher recruitment thresholds (3.21 +/- 1.3 N) showed two peaks: a short latency (23.4 +/- 1.3 ms) P1 peak similar to the previous one and a P2 peak occurring 9.4 +/- 1.2 ms later. These motor units were named 'P1-P2 units'. 5. When the reflex contraction increased slowly, the P1 peaks of 'P1-P2 units' were clearly predominant at the beginning of the contraction, during the rising phase of the motor unit discharge frequency, while the P2 peaks became predominant when the units had reached their maximal discharge frequency. 6. Increasing the tendon vibration frequency (35, 55, 75, 95 Hz) did not modify the 'P1 unit' discharge pattern. Due to interference between vibration period and peak latencies, increasing the vibration frequency caused the P1 and P2 peaks of 'P1-P2 units' to overlap. 7. Superficial cutaneous stimulation of the dorsal side of the forearm during tendon vibration noticeably decreased the P1 peaks in both types of motor units. In the P2 peaks it could result in either a decrease or an increase but the average effect was a slight increase. 8. When applied 10 s before tendon vibration, cutaneous stimulation considerably suppressed the tonic vibration reflex.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:1822565

Whole genome sequencing and phylogenetic analysis of Bluetongue virus serotype 2 strains isolated in the Americas including a novel strain from the western United States.

PubMed

Gaudreault, Natasha N; Mayo, Christie E; Jasperson, Dane C; Crossley, Beate M; Breitmeyer, Richard E; Johnson, Donna J; Ostlund, Eileen N; MacLachlan, N James; Wilson, William C

2014-07-01

Bluetongue is a potentially fatal arboviral disease of domestic and wild ruminants that is characterized by widespread edema and tissue necrosis. Bluetongue virus (BTV) serotypes 10, 11, 13, and 17 occur throughout much of the United States, whereas serotype 2 (BTV-2) was previously only detected in the southeastern United States. Since 1998, 10 other BTV serotypes have also been isolated from ruminants in the southeastern United States. In 2010, BTV-2 was identified in California for the first time, and preliminary sequence analysis indicated that the virus isolate was closely related to BTV strains circulating in the southeastern United States. In the current study, the whole genome sequence of the California strain of BTV-2 was compared with those of other BTV-2 strains in the Americas. The results of the analysis suggest co-circulation of genetically distinct viruses in the southeastern United States, and further suggest that the 2010 western isolate is closely related to southeastern strains of BTV. Although it remains uncertain as to how this novel virus was translocated to California, the findings of the current study underscore the need for ongoing surveillance of this economically important livestock disease.

Total main rotor isolation system analysis

NASA Technical Reports Server (NTRS)

Sankewitsch, V.

1981-01-01

Requirements, preliminary design, and verification procedures for a total main rotor isolation system at n/rev are presented. The fuselage is isolated from the vibration inducing main rotor at one frequency in all degrees of freedom by four antiresonant isolation units. Effects of parametric variations on isolation system performance are evaluated.

Carving Executive Control at Its Joints: Working Memory Capacity Predicts Stimulus-Stimulus, but Not Stimulus-Response, Conflict

ERIC Educational Resources Information Center

Meier, Matt E.; Kane, Michael J.

2015-01-01

Three experiments examined the relation between working memory capacity (WMC) and 2 different forms of cognitive conflict: stimulus-stimulus (S-S) and stimulus-response (S-R) interference. Our goal was to test whether WMC's relation to conflict-task performance is mediated by stimulus-identification processes (captured by S-S conflict),…

Molecular Epidemiological Study of Aspergillus fumigatus in a Bone Marrow Transplantation Unit by PCR Amplification of Ribosomal Intergenic Spacer Sequences

PubMed Central

Radford, Sarah A.; Johnson, Elizabeth M.; Leeming, John P.; Millar, Michael R.; Cornish, Jacqueline M.; Foot, Annabel B. M.; Warnock, David W.

1998-01-01

We have developed a PCR-based method for the subspecific discrimination of Aspergillus fumigatus types by using two primers designed to amplify the intergenic spacer regions between ribosomal DNA transcription units. The method permitted the reproducible discrimination of 11 distinct DNA types among a total of 119 isolates of A. fumigatus collected from patients and from the environment of a bone marrow transplantation (BMT) unit over a three-year period. Ten DNA types of A. fumigatus were isolated from patients in the BMT unit; eight of these types were also found in the hospital environment, and six of these were present in the unit itself. Thirteen BMT patients developed infection with one of three DNA types some months after these had first been found in the environment of the unit. In other instances, the same DNA types of A. fumigatus were isolated from BMT patients that were later recovered from the environment of the unit. Several DNA types of A. fumigatus were found in the hospital environment over an 18-month period. Molecular typing of multiple isolates of A. fumigatus, obtained from postmortem tissue samples, showed that one patient was infected with a single DNA type, but two others had up to three different DNA types. Our findings suggest that A. fumigatus infection in BMT recipients may be nosocomial in origin and underline the need for careful environmental monitoring of units in which high-risk patients are housed. PMID:9574694

A six-month Serratia marcescens outbreak in a Neonatal Intensive Care Unit.

PubMed

Morillo, Áurea; González, Verónica; Aguayo, Josefa; Carreño, Concepción; Torres, María José; Jarana, Daniel; Artacho, María José; Jiménez, Francisco; Conde, Manuel; Aznar, Javier

2016-12-01

To investigate a Serratia marcescens (S. marcescens) outbreak in a Neonatal Unit in a tertiary university hospital. Descriptive study of children admitted to the Unit with S. marcescens infection from November 2012 to March 2013. Conventional microbiological methods for clinical and environmental samples were used. The clonal relationship between all available isolates was established by molecular methods. A multidisciplinary team was formed, and preventive measures were taken. S. marcescens was isolated from 18 children. The overall attack rate was 12%, and the case fatality rate in the Intensive Care Unit was 23.5%. The most prevalent types of infections were pneumonia (6), conjunctivitis (6), and bloodstream infection (5). Clinical isolates and environmental isolates obtained from an incubator belonged to a unique clone. The clonal relationship between all S. marcescens strains helped us to identify the possible source of the outbreak. Isolation of S. marcescens from stored water in a container, and from the surface of an incubator after cleaning, suggests a possible environmental source as the outbreak origin, which has been perpetuated due to a failure of cleaning methods in the Unit. The strict hygiene and cleaning measures were the main factors that contributed to the end of the outbreak. Copyright © 2016 Elsevier España, S.L.U. and Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica. All rights reserved.

Serological Relationships Among Feline Caliciviruses

PubMed Central

Povey, R. C.

1974-01-01

A total of 46 strains of feline calicivirus isolates from the United Kingdom, United States, Australia, and New Zealand were used in an investigation of their serological relationships based on the serum neutralization test. Although demonstrable antigenic variation exists between these isolates, it is shown that significant in vitro cross-activity exists between all these isolates to greater or lesser extent. All isolates tested may be regarded as serological variants of a single serotype of feline calicivirus. It is postulated that this relationship would provide for considerable cross-protection during successive exposures of cats to various feline caliciviruses. PMID:4435957

A novel pathogenic Mammalian orthoreovirus from diarrheic pigs and Swine blood meal in the United States.

PubMed

Thimmasandra Narayanappa, Athmaram; Sooryanarain, Harini; Deventhiran, Jagadeeswaran; Cao, Dianjun; Ammayappan Venkatachalam, Backiyalakshmi; Kambiranda, Devaiah; LeRoith, Tanya; Heffron, Connie Lynn; Lindstrom, Nicole; Hall, Karen; Jobst, Peter; Sexton, Cary; Meng, Xiang-Jin; Elankumaran, Subbiah

2015-05-19

Since May 2013, outbreaks of porcine epidemic diarrhea have devastated the U.S. swine industry, causing immense economic losses. Two different swine enteric coronaviruses (porcine epidemic diarrhea virus and Delta coronavirus) have been isolated from the affected swine population. The disease has been reported from at least 32 states of the United States and other countries, including Mexico, Peru, Dominican Republic, Canada, Columbia, Ecuador, and Ukraine, with repeated outbreaks in previously infected herds. Here we report the isolation and characterization of a novel mammalian orthoreovirus 3 (MRV3) from diarrheic feces of piglets from these outbreaks in three states and ring-dried swine blood meal from multiple sources. MRV3 could not be isolated from healthy or pigs that had recovered from epidemic diarrhea from four states. Several MRV3 isolates were obtained from chloroform-extracted pig feces or blood meal in cell cultures or developing chicken embryos. Biological characterization of two representative isolates revealed trypsin resistance and thermostability at 90°C. NextGen sequencing of ultrapurified viruses indicated a strong homology of the S1 segment to mammalian and bat MRV3. Neonatal piglets experimentally infected with these viruses or a chloroform extract of swine blood meal developed severe diarrhea and acute gastroenteritis with 100% mortality within 3 days postinfection. Therefore, the novel porcine MRV3 may contribute to enteric disease along with other swine enteric viruses. The role of MRV3 in the current outbreaks of porcine epidemic diarrhea in the United States remains to be determined, but the pathogenic nature of the virus warrants further investigations on its epidemiology and prevalence. Porcine orthoreoviruses causing diarrhea have been reported in China and Korea but not in the United States. We have isolated and characterized two pathogenic reassortant MRV3 isolates from swine fecal samples from porcine epidemic diarrhea outbreaks and ring-dried swine blood meal in the United States. These fecal and blood meal isolates or a chloroform extract of blood meal induced severe diarrhea and mortality in experimentally infected neonatal pigs. Genetic and phylogenetic analyses of two MRV3 isolates revealed that they are identical but differed significantly from nonpathogenic mammalian orthoreoviruses circulating in the United States. The present study provides a platform for immediate development of suitable vaccines and diagnostics to prevent and control porcine orthoreovirus diarrhea. Copyright © 2015 Thimmasandra Narayanappa et al.

Control of preference in children by conditioned positive reinforcement.

PubMed

Favell, J E; Favell, J E

1972-07-01

A preference measure was employed with children to evaluate the conditioned positive reinforcing function of a stimulus that preceded reinforcement. A match-to-sample procedure was arranged in which subjects could respond to either the form or color dimension of a compound sample stimulus. Intermittent token reinforcement was provided equally for color and form matches. Two stimuli were employed (Stimulus A and Stimulus B), each consisting of a distinctive tone and colored light. One of these stimuli (the paired stimulus) preceded each token delivery, and the other did not (nonpaired stimulus). The paired stimulus was dependent upon each response to one match dimension, and the nonpaired stimulus followed each response to the other dimension. Three of the five subjects responded primarily to the dimension that was followed by the paired stimulus. This effect was obtained regardless of which stimulus (A or B) was paired and on which match dimension (color or form) the paired stimulus was dependent. These results were unaltered by discontinuing the nonpaired stimulus. The other two subjects demonstrated consistent preferences for the form dimension and Stimulus A, respectively.

Mobile phones and computer keyboards: unlikely reservoirs of multidrug-resistant organisms in the tertiary intensive care unit.

PubMed

Smibert, O C; Aung, A K; Woolnough, E; Carter, G P; Schultz, M B; Howden, B P; Seemann, T; Spelman, D; McGloughlin, S; Peleg, A Y

2018-03-02

Few studies have used molecular epidemiological methods to study transmission links to clinical isolates in intensive care units. Ninety-four multidrug-resistant organisms (MDROs) cultured from routine specimens from intensive care unit (ICU) patients over 13 weeks were stored (11 meticillin-resistant Staphylococcus aureus (MRSA), two vancomycin-resistant enterococci and 81 Gram-negative bacteria). Medical staff personal mobile phones, departmental phones, and ICU keyboards were swabbed and cultured for MDROs; MRSA was isolated from two phones. Environmental and patient isolates of the same genus were selected for whole genome sequencing. On whole genome sequencing, the mobile phone isolates had a pairwise single nucleotide polymorphism (SNP) distance of 183. However, >15,000 core genome SNPs separated the mobile phone and clinical isolates. In a low-endemic setting, mobile phones and keyboards appear unlikely to contribute to hospital-acquired MDROs. Copyright © 2018 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.

Effect of nucleus accumbens lesions on socially motivated behaviour of young domestic chicks.

PubMed

Zachar, Gergely; Tóth, András Sebestyén; Balogh, Márton; Csillag, András

2017-06-01

Behaviour of young domestic chicks when isolated from conspecifics is influenced by two conflicting drives: fear of potential predator and craving for company. The nucleus accumbens (Ac) has been suggested to influence social behaviour, as well as motivation in goal-directed tasks. In this study, the Ac of 1-day-old domestic chicks was lesioned bilaterally, using radiofrequency method. Open field behaviour before and after presenting a silhouette of a bird of prey was recorded, followed by a behavioural test to measure group size preference and social motivation of chicks. Ac-lesioned individuals emitted more distress calls and ambulated more in the open field test, however, they reacted to the predatory stimulus very similarly to control chicks: their vocalization was reduced and the intergroup difference in motor activity also disappeared. There was no difference between the lesioned and control chicks in the latency to approach their conspecifics in the social motivation test, and both groups chose the larger flock (eight) of conspecifics over the smaller one (three). Concerning the role of Ac in social behaviour, a difference between lesioned and sham birds was evident here only in the absence of detectable stimulus (predator or conspecifics). These findings may reflect either decreased fear of exposure to predators or increased craving for conspecifics suggesting that the likely function of Ac is to modulate goal-driven, including socially driven, behaviours, especially when the direct stimulus representing the goal is absent. This is in harmony with the known promotion of impulsiveness by Ac lesions. © 2016 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

Delivery of nicotine in an extract of a smokeless tobacco product reduces its reinforcement-attenuating and discriminative stimulus effects in rats

PubMed Central

Harris, Andrew C.; Stepanov, Irina; Pentel, Paul R.; LeSage, Mark G.

2012-01-01

Rationale Animal models of tobacco addiction rely on administration of nicotine alone or nicotine combined with isolated constituents. Models using tobacco extracts derived from tobacco products and containing a range of tobacco constituents might more accurately simulate tobacco exposure in humans. Objective To compare the effects of nicotine alone and an aqueous smokeless tobacco extract in several addiction-related animal behavioral models. Methods Nicotine alone and nicotine dose-equivalent concentrations of extract were compared in terms of their acute effects on intracranial self-stimulation (ICSS) thresholds, discriminative stimulus effects, and effects on locomotor activity. Results Similar levels of nicotine and minor alkaloids were achieved using either artificial saliva or saline for extraction, supporting the clinical relevance of the saline extracts used in these studies. Extract produced reinforcement-enhancing (ICSS threshold-decreasing) effects similar to those of nicotine alone at low to moderate nicotine doses, but reduced reinforcement-attenuating (ICSS threshold-increasing) effects at a high nicotine dose. In rats trained to discriminate nicotine alone from saline, intermediate extract doses did not substitute for the training dose as well as nicotine alone. Locomotor stimulant effects and nicotine distribution to brain were similar following administration of extract or nicotine alone. Conclusions The reinforcement-attenuating and discriminative stimulus effects of nicotine delivered in an extract of a commercial smokeless tobacco product differed from those of nicotine alone. Extracts of tobacco products may be useful for evaluating the abuse liability of those products and understanding the role of non-nicotine constituents in tobacco addiction. PMID:21960181

Delivery of nicotine in an extract of a smokeless tobacco product reduces its reinforcement-attenuating and discriminative stimulus effects in rats.

PubMed

Harris, Andrew C; Stepanov, Irina; Pentel, Paul R; Lesage, Mark G

2012-04-01

Animal models of tobacco addiction rely on administration of nicotine alone or nicotine combined with isolated constituents. Models using tobacco extracts derived from tobacco products and containing a range of tobacco constituents might more accurately simulate tobacco exposure in humans. To compare the effects of nicotine alone and an aqueous smokeless tobacco extract in several addiction-related animal behavioral models. Nicotine alone and nicotine dose-equivalent concentrations of extract were compared in terms of their acute effects on intracranial self-stimulation (ICSS) thresholds, discriminative stimulus effects, and effects on locomotor activity. Similar levels of nicotine and minor alkaloids were achieved using either artificial saliva or saline for extraction, supporting the clinical relevance of the saline extracts used in these studies. Extract produced reinforcement-enhancing (ICSS threshold-decreasing) effects similar to those of nicotine alone at low to moderate nicotine doses, but reduced reinforcement-attenuating (ICSS threshold-increasing) effects at a high nicotine dose. In rats trained to discriminate nicotine alone from saline, intermediate extract doses did not substitute for the training dose as well as nicotine alone. Locomotor stimulant effects and nicotine distribution to brain were similar following administration of extract or nicotine alone. The reinforcement-attenuating and discriminative stimulus effects of nicotine delivered in an extract of a commercial smokeless tobacco product differed from those of nicotine alone. Extracts of tobacco products may be useful for evaluating the abuse liability of those products and understanding the role of non-nicotine constituents in tobacco addiction.

Emotion modulates activity in the 'what' but not 'where' auditory processing pathway.

PubMed

Kryklywy, James H; Macpherson, Ewan A; Greening, Steven G; Mitchell, Derek G V

2013-11-15

Auditory cortices can be separated into dissociable processing pathways similar to those observed in the visual domain. Emotional stimuli elicit enhanced neural activation within sensory cortices when compared to neutral stimuli. This effect is particularly notable in the ventral visual stream. Little is known, however, about how emotion interacts with dorsal processing streams, and essentially nothing is known about the impact of emotion on auditory stimulus localization. In the current study, we used fMRI in concert with individualized auditory virtual environments to investigate the effect of emotion during an auditory stimulus localization task. Surprisingly, participants were significantly slower to localize emotional relative to neutral sounds. A separate localizer scan was performed to isolate neural regions sensitive to stimulus location independent of emotion. When applied to the main experimental task, a significant main effect of location, but not emotion, was found in this ROI. A whole-brain analysis of the data revealed that posterior-medial regions of auditory cortex were modulated by sound location; however, additional anterior-lateral areas of auditory cortex demonstrated enhanced neural activity to emotional compared to neutral stimuli. The latter region resembled areas described in dual pathway models of auditory processing as the 'what' processing stream, prompting a follow-up task to generate an identity-sensitive ROI (the 'what' pathway) independent of location and emotion. Within this region, significant main effects of location and emotion were identified, as well as a significant interaction. These results suggest that emotion modulates activity in the 'what,' but not the 'where,' auditory processing pathway. Copyright © 2013 Elsevier Inc. All rights reserved.

47 CFR 76.2000 - Exclusive access to multiple dwelling units generally.

Code of Federal Regulations, 2010 CFR

2010-10-01

... time share units, academic campuses and dormitories, military bases, hotels, rooming houses, prisons..., Receiver-generated, Responsibility 76.617 Isolation, Terminal 76.5 J-L Leakage measurements, Signal 76.601... noise 76.5 T Technical standards 76.605 Terminal isolation 76.5 Terminal, Subscriber 76.5 Tests...

47 CFR 76.2000 - Exclusive access to multiple dwelling units generally.

Code of Federal Regulations, 2011 CFR

2011-10-01

... time share units, academic campuses and dormitories, military bases, hotels, rooming houses, prisons..., Receiver-generated, Responsibility 76.617 Isolation, Terminal 76.5 J-L Leakage measurements, Signal 76.601... noise 76.5 T Technical standards 76.605 Terminal isolation 76.5 Terminal, Subscriber 76.5 Tests...

High prevalence of antimicrobial resistance among Shigella isolates in the United States tested by the National Antimicrobial Resistance Monitoring System from 1999 to 2002.

PubMed

Sivapalasingam, Sumathi; Nelson, Jennifer M; Joyce, Kevin; Hoekstra, Mike; Angulo, Frederick J; Mintz, Eric D

2006-01-01

Shigella spp. infect approximately 450,000 persons annually in the United States, resulting in over 6,000 hospitalizations. Since 1999, the National Antimicrobial Resistance Monitoring System (NARMS) for Enteric Bacteria has tested every 10th Shigella isolate from 16 state or local public health laboratories for susceptibility to 15 antimicrobial agents. From 1999 to 2002, NARMS tested 1,604 isolates. Among 1,598 isolates identified to species level, 1,278 (80%) were Shigella sonnei, 295 (18%) were Shigella flexneri, 18 (1%) were Shigella boydii, and 7 (0.4%) were Shigella dysenteriae. Overall, 1,251 (78%) were resistant to ampicillin and 744 (46%) were resistant to trimethoprim-sulfamethoxazole (TMP-SMX). Prevalence of TMP-SMX- or ampicillin- and TMP-SMX-resistant Shigella sonnei isolates varied by geographic region, with lower rates in the South and Midwest regions (TMP-SMX resistance, 27% and 30%, respectively; ampicillin and TMP-SMX resistance, 25% and 22%, respectively) and higher rates in the East and West regions (TMP-SMX resistance, 66% and 80%, respectively; ampicillin and TMP-SMX resistance, 54% and 65%, respectively). Nineteen isolates (1%) were resistant to nalidixic acid (1% of S. sonnei and 2% of S. flexneri isolates); 12 (63%) of these isolates had decreased susceptibility to ciprofloxacin. One S. flexneri isolate was resistant to ciprofloxacin. All isolates were susceptible to ceftriaxone. Since 1986, resistance to ampicillin and TMP-SMX has dramatically increased. Shigella isolates in the United States remain susceptible to ciprofloxacin and ceftriaxone.

High Prevalence of Antimicrobial Resistance among Shigella Isolates in the United States Tested by the National Antimicrobial Resistance Monitoring System from 1999 to 2002

PubMed Central

Sivapalasingam, Sumathi; Nelson, Jennifer M.; Joyce, Kevin; Hoekstra, Mike; Angulo, Frederick J.; Mintz, Eric D.

2006-01-01

Shigella spp. infect approximately 450,000 persons annually in the United States, resulting in over 6,000 hospitalizations. Since 1999, the National Antimicrobial Resistance Monitoring System (NARMS) for Enteric Bacteria has tested every 10th Shigella isolate from 16 state or local public health laboratories for susceptibility to 15 antimicrobial agents. From 1999 to 2002, NARMS tested 1,604 isolates. Among 1,598 isolates identified to species level, 1,278 (80%) were Shigella sonnei, 295 (18%) were Shigella flexneri, 18 (1%) were Shigella boydii, and 7 (0.4%) were Shigella dysenteriae. Overall, 1,251 (78%) were resistant to ampicillin and 744 (46%) were resistant to trimethoprim-sulfamethoxazole (TMP-SMX). Prevalence of TMP-SMX- or ampicillin- and TMP-SMX-resistant Shigella sonnei isolates varied by geographic region, with lower rates in the South and Midwest regions (TMP-SMX resistance, 27% and 30%, respectively; ampicillin and TMP-SMX resistance, 25% and 22%, respectively) and higher rates in the East and West regions (TMP-SMX resistance, 66% and 80%, respectively; ampicillin and TMP-SMX resistance, 54% and 65%, respectively). Nineteen isolates (1%) were resistant to nalidixic acid (1% of S. sonnei and 2% of S. flexneri isolates); 12 (63%) of these isolates had decreased susceptibility to ciprofloxacin. One S. flexneri isolate was resistant to ciprofloxacin. All isolates were susceptible to ceftriaxone. Since 1986, resistance to ampicillin and TMP-SMX has dramatically increased. Shigella isolates in the United States remain susceptible to ciprofloxacin and ceftriaxone. PMID:16377666

Sex and the stimulus-movement effect: Differences in acquisition of autoshaped responding in cynomolgus monkeys.

PubMed

Rice, Nathaniel C; Makar, Jennifer R; Myers, Todd M

2017-03-15

The stimulus-movement effect refers to the phenomenon in which stimulus discrimination or acquisition of a response is facilitated by moving stimuli as opposed to stationary stimuli. The effect has been found in monkeys, rats, and humans, but the experiments conducted did not provide adequate female representation to investigate potential sex differences. The current experiment analyzed acquisition of stimulus touching in a progressive series of classical conditioning procedures in cynomolgus monkeys (Macaca fascicularis) as a function of sex and stimulus movement. Classical conditioning tasks arrange two or more stimuli in relation to each other with different temporal and predictive relations. Autoshaping procedures overlay operant contingencies onto a classical-conditioning stimulus arrangement. In the present case, a neutral stimulus (a small gray square displayed on a touchscreen) functioned as the conditional stimulus and a food pellet functioned as the unconditional stimulus. Although touching is not required to produce food, with repeated stimulus pairings subjects eventually touch the stimulus. Across conditions of increasing stimulus correlation and temporal contiguity, male monkeys acquired the response faster with a moving stimulus. In contrast, females acquired the response faster with a stationary stimulus. These results demonstrate that the stimulus-movement effect may be differentially affected by sex and indicate that additional experiments with females are needed to determine how sex interacts with behavioral phenomena discovered and elaborated almost exclusively using males. Published by Elsevier Inc.

Influence of stimulus and oral adaptation temperature on gustatory responses in central taste-sensitive neurons

PubMed Central

Li, Jinrong

2015-01-01

The temperature of taste stimuli can modulate gustatory processing. Perceptual data indicate that the adapted temperature of oral epithelia also influences gustation, although little is known about the neural basis of this effect. Here, we electrophysiologically recorded orosensory responses (spikes) to 25°C (cool) and 35°C (warm) solutions of sucrose (0.1 and 0.3 M), NaCl (0.004, 0.1, and 0.3 M), and water from taste-sensitive neurons in the nucleus of the solitary tract in mice under varied thermal adaptation of oral epithelia. Conditions included presentation of taste stimuli isothermal to adaptation temperatures of 25°C (constant cooling) and 35°C (constant warming), delivery of 25°C stimuli following 35°C adaptation (relative cooling), and presentation of 35°C stimuli following 25°C adaptation (relative warming). Responses to sucrose in sucrose-oriented cells (n = 15) were enhanced under the constant and relative warming conditions compared with constant cooling, where contiguous cooling across adaptation and stimulus periods induced the lowest and longest latency responses to sucrose. Yet compared with constant warming, cooling sucrose following warm adaptation (relative cooling) only marginally reduced activity to 0.1 M sucrose and did not alter responses to 0.3 M sucrose. Thus, warmth adaptation counteracted the attenuation in sucrose activity associated with stimulus cooling. Analysis of sodium-oriented (n = 25) neurons revealed adaptation to cool water, and cooling taste solutions enhanced unit firing to 0.004 M (perithreshold) NaCl, whereas warmth adaptation and stimulus warming could facilitate activity to 0.3 M NaCl. The concentration dependence of this thermal effect may reflect a dual effect of temperature on the sodium reception mechanism that drives sodium-oriented cells. PMID:25673737

Selective attention to phonology dynamically modulates initial encoding of auditory words within the left hemisphere.

PubMed

Yoncheva, Yuliya; Maurer, Urs; Zevin, Jason D; McCandliss, Bruce D

2014-08-15

Selective attention to phonology, i.e., the ability to attend to sub-syllabic units within spoken words, is a critical precursor to literacy acquisition. Recent functional magnetic resonance imaging evidence has demonstrated that a left-lateralized network of frontal, temporal, and posterior language regions, including the visual word form area, supports this skill. The current event-related potential (ERP) study investigated the temporal dynamics of selective attention to phonology during spoken word perception. We tested the hypothesis that selective attention to phonology dynamically modulates stimulus encoding by recruiting left-lateralized processes specifically while the information critical for performance is unfolding. Selective attention to phonology was captured by manipulating listening goals: skilled adult readers attended to either rhyme or melody within auditory stimulus pairs. Each pair superimposed rhyming and melodic information ensuring identical sensory stimulation. Selective attention to phonology produced distinct early and late topographic ERP effects during stimulus encoding. Data-driven source localization analyses revealed that selective attention to phonology led to significantly greater recruitment of left-lateralized posterior and extensive temporal regions, which was notably concurrent with the rhyme-relevant information within the word. Furthermore, selective attention effects were specific to auditory stimulus encoding and not observed in response to cues, arguing against the notion that they reflect sustained task setting. Collectively, these results demonstrate that selective attention to phonology dynamically engages a left-lateralized network during the critical time-period of perception for achieving phonological analysis goals. These findings suggest a key role for selective attention in on-line phonological computations. Furthermore, these findings motivate future research on the role that neural mechanisms of attention may play in phonological awareness impairments thought to underlie developmental reading disabilities. Copyright © 2014 The Authors. Published by Elsevier Inc. All rights reserved.

Selective attention to phonology dynamically modulates initial encoding of auditory words within the left hemisphere

PubMed Central

Yoncheva; Maurer, Urs; Zevin, Jason; McCandliss, Bruce

2015-01-01

Selective attention to phonology, i.e., the ability to attend to sub-syllabic units within spoken words, is a critical precursor to literacy acquisition. Recent functional magnetic resonance imaging evidence has demonstrated that a left-lateralized network of frontal, temporal, and posterior language regions, including the visual word form area, supports this skill. The current event-related potential (ERP) study investigated the temporal dynamics of selective attention to phonology during spoken word perception. We tested the hypothesis that selective atten tion to phonology dynamically modulates stimulus encoding by recruiting left-lateralized processes specifically while the information critical for performance is unfolding. Selective attention to phonology was captured by ma nipulating listening goals: skilled adult readers attended to either rhyme or melody within auditory stimulus pairs. Each pair superimposed rhyming and melodic information ensuring identical sensory stimulation. Selective attention to phonology produced distinct early and late topographic ERP effects during stimulus encoding. Data- driven source localization analyses revealed that selective attention to phonology led to significantly greater re cruitment of left-lateralized posterior and extensive temporal regions, which was notably concurrent with the rhyme-relevant information within the word. Furthermore, selective attention effects were specific to auditory stimulus encoding and not observed in response to cues, arguing against the notion that they reflect sustained task setting. Collectively, these results demonstrate that selective attention to phonology dynamically engages a left-lateralized network during the critical time-period of perception for achieving phonological analysis goals. These findings support the key role of selective attention to phonology in the development of literacy and motivate future research on the neural bases of the interaction between phonological awareness and literacy, deemed central to both typical and atypical reading development. PMID:24746955

Source recognition by stimulus content in the MTL.

PubMed

Park, Heekyeong; Abellanoza, Cheryl; Schaeffer, James; Gandy, Kellen

2014-03-17

Source memory is considered to be the cornerstone of episodic memory that enables us to discriminate similar but different events. In the present fMRI study, we investigated whether neural correlates of source retrieval differed by stimulus content in the medial temporal lobe (MTL) when the item and context had been integrated as a perceptually unitized entity. Participants were presented with a list of items either in verbal or pictorial form overlaid on a colored square and instructed to integrate both the item and context into a single image. At test, participants judged the study status of test items and the color in which studied items were presented. Source recognition invariant of stimulus content elicited retrieval activity in both the left anterior hippocampus extending to the perirhinal cortex and the right posterior hippocampus. Word-selective source recognition was related to activity in the left perirhinal cortex, whereas picture-selective source recognition was identified in the left posterior hippocampus. Neural activity sensitive to novelty detection common to both words and pictures was found in the left anterior and right posterior hippocampus. Novelty detection selective to words was associated with the left perirhinal cortex, while activity sensitive to new pictures was identified in the bilateral hippocampus and adjacent MTL cortices, including the parahippocampal, entorhinal, and perirhinal cortices. These findings provide further support for the integral role of the hippocampus both in source recognition and in detection of new stimuli across stimulus content. Additionally, novelty effects in the MTL reveal the integral role of the MTL cortex as the interface for processing new information. Collectively, the present findings demonstrate the importance of the MTL for both previously experienced and novel events. Copyright © 2014 Elsevier B.V. All rights reserved.

Induction and modulation of persistent activity in a layer V PFC microcircuit model.

PubMed

Papoutsi, Athanasia; Sidiropoulou, Kyriaki; Cutsuridis, Vassilis; Poirazi, Panayiota

2013-01-01

Working memory refers to the temporary storage of information and is strongly associated with the prefrontal cortex (PFC). Persistent activity of cortical neurons, namely the activity that persists beyond the stimulus presentation, is considered the cellular correlate of working memory. Although past studies suggested that this type of activity is characteristic of large scale networks, recent experimental evidence imply that small, tightly interconnected clusters of neurons in the cortex may support similar functionalities. However, very little is known about the biophysical mechanisms giving rise to persistent activity in small-sized microcircuits in the PFC. Here, we present a detailed biophysically-yet morphologically simplified-microcircuit model of layer V PFC neurons that incorporates connectivity constraints and is validated against a multitude of experimental data. We show that (a) a small-sized network can exhibit persistent activity under realistic stimulus conditions. (b) Its emergence depends strongly on the interplay of dADP, NMDA, and GABAB currents. (c) Although increases in stimulus duration increase the probability of persistent activity induction, variability in the stimulus firing frequency does not consistently influence it. (d) Modulation of ionic conductances (I h , I D , I sAHP, I caL, I caN, I caR) differentially controls persistent activity properties in a location dependent manner. These findings suggest that modulation of the microcircuit's firing characteristics is achieved primarily through changes in its intrinsic mechanism makeup, supporting the hypothesis of multiple bi-stable units in the PFC. Overall, the model generates a number of experimentally testable predictions that may lead to a better understanding of the biophysical mechanisms of persistent activity induction and modulation in the PFC.

Fear of falling and postural reactivity in patients with glaucoma.

PubMed

Daga, Fábio B; Diniz-Filho, Alberto; Boer, Erwin R; Gracitelli, Carolina P B; Abe, Ricardo Y; Medeiros, Felipe A

2017-01-01

To investigate the relationship between postural metrics obtained by dynamic visual stimulation in a virtual reality environment and the presence of fear of falling in glaucoma patients. This cross-sectional study included 35 glaucoma patients and 26 controls that underwent evaluation of postural balance by a force platform during presentation of static and dynamic visual stimuli with head-mounted goggles (Oculus Rift). In dynamic condition, a peripheral translational stimulus was used to induce vection and assess postural reactivity. Standard deviations of torque moments (SDTM) were calculated as indicative of postural stability. Fear of falling was assessed by a standardized questionnaire. The relationship between a summary score of fear of falling and postural metrics was investigated using linear regression models, adjusting for potentially confounding factors. Subjects with glaucoma reported greater fear of falling compared to controls (-0.21 vs. 0.27; P = 0.039). In glaucoma patients, postural metrics during dynamic visual stimulus were more associated with fear of falling (R2 = 18.8%; P = 0.001) than static (R2 = 3.0%; P = 0.005) and dark field (R2 = 5.7%; P = 0.007) conditions. In the univariable model, fear of falling was not significantly associated with binocular standard perimetry mean sensitivity (P = 0.855). In the multivariable model, each 1 Nm larger SDTM in anteroposterior direction during dynamic stimulus was associated with a worsening of 0.42 units in the fear of falling questionnaire score (P = 0.001). In glaucoma patients, postural reactivity to a dynamic visual stimulus using a virtual reality environment was more strongly associated with fear of falling than visual field testing and traditional balance assessment.

Fear of falling and postural reactivity in patients with glaucoma

PubMed Central

Daga, Fábio B.; Diniz-Filho, Alberto; Boer, Erwin R.; Gracitelli, Carolina P. B.; Abe, Ricardo Y.; Medeiros, Felipe A.

2017-01-01

Purpose To investigate the relationship between postural metrics obtained by dynamic visual stimulation in a virtual reality environment and the presence of fear of falling in glaucoma patients. Methods This cross-sectional study included 35 glaucoma patients and 26 controls that underwent evaluation of postural balance by a force platform during presentation of static and dynamic visual stimuli with head-mounted goggles (Oculus Rift). In dynamic condition, a peripheral translational stimulus was used to induce vection and assess postural reactivity. Standard deviations of torque moments (SDTM) were calculated as indicative of postural stability. Fear of falling was assessed by a standardized questionnaire. The relationship between a summary score of fear of falling and postural metrics was investigated using linear regression models, adjusting for potentially confounding factors. Results Subjects with glaucoma reported greater fear of falling compared to controls (-0.21 vs. 0.27; P = 0.039). In glaucoma patients, postural metrics during dynamic visual stimulus were more associated with fear of falling (R2 = 18.8%; P = 0.001) than static (R2 = 3.0%; P = 0.005) and dark field (R2 = 5.7%; P = 0.007) conditions. In the univariable model, fear of falling was not significantly associated with binocular standard perimetry mean sensitivity (P = 0.855). In the multivariable model, each 1 Nm larger SDTM in anteroposterior direction during dynamic stimulus was associated with a worsening of 0.42 units in the fear of falling questionnaire score (P = 0.001). Conclusion In glaucoma patients, postural reactivity to a dynamic visual stimulus using a virtual reality environment was more strongly associated with fear of falling than visual field testing and traditional balance assessment. PMID:29211742

The immediate effect of a brief energy psychology intervention (Emotional Freedom Techniques) on specific phobias: a pilot study.

PubMed

Salas, Martha M; Brooks, Audrey J; Rowe, Jack E

2011-01-01

Specific phobia is one of the most prevalent anxiety disorders. Emotional Freedom Techniques (EFT) has been shown to improve anxiety symptoms; however, their application to specific phobias has received limited attention. This pilot study examined whether EFT, a brief exposure therapy that combines cognitive and somatic elements, had an immediate effect on the reduction of anxiety and behavior associated with specific phobias. The study utilized a crossover design with participants randomly assigned to either diaphragmatic breathing or EFT as the first treatment. The study was conducted at a regional university in the Southwestern United States. Twenty-two students meeting criteria for a phobic response to a specific stimulus (≥8 on an 11-point subjective units of distress scale). Participants completed a total of five two-minute rounds in each treatment intervention. Study measures included a behavioral approach test (BAT), Subjective Units of Distress Scale (SUDS), and Beck Anxiety Inventory (BAI). Emotional Freedom Techniques significantly reduced phobia-related anxiety (BAI P = .042; SUDS P = .002) and ability to approach the feared stimulus (BAT P = .046) whether presented as an initial treatment or following diaphragmatic breathing. When presented as the initial treatment, the effects of EFT remained through the presentation of the comparison intervention. The efficacy of EFT in treating specific phobias demonstrated in several earlier studies is corroborated by the current investigation. Comparison studies between EFT and the most effective established therapies for treating specific phobias are recommended. Copyright © 2011 Elsevier Inc. All rights reserved.

Acyl-coenzyme A oxidases 1 and 3 in brown trout (Salmo trutta f. fario): Can peroxisomal fatty acid β-oxidation be regulated by estrogen signaling?

PubMed

Madureira, Tânia Vieira; Castro, L Filipe C; Rocha, Eduardo

2016-02-01

Acyl-coenzyme A oxidases 1 (Acox1) and 3 (Acox3) are key enzymes in the regulation of lipid homeostasis. Endogenous and exogenous factors can disrupt their normal expression/activity. This study presents for the first time the isolation and characterization of Acox1 and Acox3 in brown trout (Salmo trutta f. fario). Additionally, as previous data point to the existence of a cross-talk between two nuclear receptors, namely peroxisome proliferator-activated receptors and estrogen receptors, it was here evaluated after in vitro exposures of trout hepatocytes the interference caused by ethynylestradiol in the mRNA levels of an inducible (by peroxisome proliferators) and a non-inducible oxidase. The isolated Acox1 and Acox3 show high levels of sequence conservation compared to those of other teleosts. Additionally, it was found that Acox1 has two alternative splicing isoforms, corresponding to 3I and 3II isoforms of exon 3 splicing variants. Both isoforms display tissue specificity, with Acox1-3II presenting a more ubiquitous expression in comparison with Acox1-3I. Acox3 was expressed in almost all brown trout tissues. According to real-time PCR data, the highest estrogenic stimulus was able to cause a down-regulation of Acox1 and an up-regulation of Acox3. So, for Acox1 we found a negative association between an estrogenic input and a directly activated PPARα target gene. In conclusion, changes in hormonal estrogenic stimulus may impact the mobilization of hepatic lipids to the gonads, with ultimate consequences in reproduction. Further studies using in vivo assays will be fundamental to clarify these issues.

Multilocus sequence typing (MLST) analysis of Propionibacterium acnes isolates from radical prostatectomy specimens.

PubMed

Mak, Tim N; Yu, Shu-Han; De Marzo, Angelo M; Brüggemann, Holger; Sfanos, Karen S

2013-05-01

Inflammation is commonly observed in radical prostatectomy specimens, and evidence suggests that inflammation may contribute to prostate carcinogenesis. Multiple microorganisms have been implicated in serving as a stimulus for prostatic inflammation. The pro-inflammatory anaerobe, Propionibacterium acnes, is ubiquitously found on human skin and is associated with the skin disease acne vulgaris. Recent studies have shown that P. acnes can be detected in prostatectomy specimens by bacterial culture or by culture-independent molecular techniques. Radical prostatectomy tissue samples were obtained from 30 prostate cancer patients and subject to both aerobic and anaerobic culture. Cultured species were identified by 16S rDNA gene sequencing. Propionibacterium acnes isolates were typed using multilocus sequence typing (MLST). Our study confirmed that P. acnes can be readily cultured from prostatectomy tissues (7 of 30 cases, 23%). In some cases, multiple isolates of P. acnes were cultured as well as other Propionibacterium species, such as P. granulosum and P. avidum. Overall, 9 of 30 cases (30%) were positive for Propionibacterium spp. MLST analyses identified eight different sequence types (STs) among prostate-derived P. acnes isolates. These STs belong to two clonal complexes, namely CC36 (type I-2) and CC53/60 (type II), or are CC53/60-related singletons. MLST typing results indicated that prostate-derived P. acnes isolates do not fall within the typical skin/acne STs, but rather are characteristic of STs associated with opportunistic infections and/or urethral flora. The MLST typing results argue against the likelihood that prostatectomy-derived P. acnes isolates represent contamination from skin flora. Copyright © 2012 Wiley Periodicals, Inc.

Where’s the Noise? Key Features of Spontaneous Activity and Neural Variability Arise through Learning in a Deterministic Network

PubMed Central

Hartmann, Christoph; Lazar, Andreea; Nessler, Bernhard; Triesch, Jochen

2015-01-01

Even in the absence of sensory stimulation the brain is spontaneously active. This background “noise” seems to be the dominant cause of the notoriously high trial-to-trial variability of neural recordings. Recent experimental observations have extended our knowledge of trial-to-trial variability and spontaneous activity in several directions: 1. Trial-to-trial variability systematically decreases following the onset of a sensory stimulus or the start of a motor act. 2. Spontaneous activity states in sensory cortex outline the region of evoked sensory responses. 3. Across development, spontaneous activity aligns itself with typical evoked activity patterns. 4. The spontaneous brain activity prior to the presentation of an ambiguous stimulus predicts how the stimulus will be interpreted. At present it is unclear how these observations relate to each other and how they arise in cortical circuits. Here we demonstrate that all of these phenomena can be accounted for by a deterministic self-organizing recurrent neural network model (SORN), which learns a predictive model of its sensory environment. The SORN comprises recurrently coupled populations of excitatory and inhibitory threshold units and learns via a combination of spike-timing dependent plasticity (STDP) and homeostatic plasticity mechanisms. Similar to balanced network architectures, units in the network show irregular activity and variable responses to inputs. Additionally, however, the SORN exhibits sequence learning abilities matching recent findings from visual cortex and the network’s spontaneous activity reproduces the experimental findings mentioned above. Intriguingly, the network’s behaviour is reminiscent of sampling-based probabilistic inference, suggesting that correlates of sampling-based inference can develop from the interaction of STDP and homeostasis in deterministic networks. We conclude that key observations on spontaneous brain activity and the variability of neural responses can be accounted for by a simple deterministic recurrent neural network which learns a predictive model of its sensory environment via a combination of generic neural plasticity mechanisms. PMID:26714277

Contrasting patterns of genetic diversity and population structure of Armillaria mellea sensu stricto in the eastern and western United States.

PubMed

Baumgartner, Kendra; Travadon, Renaud; Bruhn, Johann; Bergemann, Sarah E

2010-07-01

ABSTRACT Armillaria mellea infects hundreds of plant species in natural and managed ecosystems throughout the Northern hemisphere. Previously reported nuclear genetic divergence between eastern and western U.S. isolates is consistent with the disjunct range of A. mellea in North America, which is restricted mainly to both coasts of the United States. We investigated patterns of population structure and genetic diversity of the eastern (northern and southern Appalachians, Ozarks, and western Great Lakes) and western (Berkeley, Los Angeles, St. Helena, and San Jose, CA) regions of the United States. In total, 156 diploid isolates were genotyped using 12 microsatellite loci. Absence of genetic differentiation within either eastern subpopulations (theta(ST) = -0.002, P = 0.5 ) or western subpopulations (theta(ST) = 0.004, P = 0.3 ) suggests that spore dispersal within each region is sufficient to prevent geographic differentiation. In contrast to the western United States, our finding of more than one genetic cluster of isolates within the eastern United States (K = 3), revealed by Bayesian assignment of multilocus genotypes in STRUCTURE and confirmed by genetic multivariate analyses, suggests that eastern subpopulations are derived from multiple founder sources. The existence of amplifiable and nonamplifiable loci and contrasting patterns of genetic diversity between the two regions demonstrate that there are two geographically isolated, divergent genetic pools of A. mellea in the United States.

Motion mechanisms with different spatiotemporal characteristics identified by an MAE technique with superimposed gratings.

PubMed

Shioiri, Satoshi; Matsumiya, Kazumichi

2009-05-29

We investigated spatiotemporal characteristics of motion mechanisms using a new type of motion aftereffect (MAE) we found. Our stimulus comprised two superimposed sinusoidal gratings with different spatial frequencies. After exposure to the moving stimulus, observers perceived the MAE in the static test in the direction opposite to that of the high spatial frequency grating even when low spatial frequency motion was perceived during adaptation. In contrast, in the flicker test, the MAE was perceived in the direction opposite to that of the low spatial frequency grating. These MAEs indicate that two different motion systems contribute to motion perception and can be isolated by using different test stimuli. Using a psychophysical technique based on the MAE, we investigated the differences between the two motion mechanisms. The results showed that the static MAE is the aftereffect of the motion system with a high spatial and low temporal frequency tuning (slow motion detector) and the flicker MAE is the aftereffect of the motion system with a low spatial and high temporal frequency tuning (fast motion detector). We also revealed that the two motion detectors differ in orientation tuning, temporal frequency tuning, and sensitivity to relative motion.

Interactions between gravitropism and phototropism in plants

NASA Technical Reports Server (NTRS)

Correll, Melanie J.; Kiss, John Z.

2002-01-01

To receive adequate light and nutrients for survival, plants orient stems and stem-like organs toward light and away from the gravity vector and, conversely, orient roots into the soil, away from light toward the direction of gravity. Therefore, both gravity and light can influence the differential growth of plant organs. To add to the complexity of the interactions between gravity and light, each stimulus can enhance or reduce the effectiveness of the other. On earth, the constant presence of gravity makes it difficult to determine whether plant growth and development is influenced by gravity or light alone or the combination of the two stimuli. In the past decade, our understanding of the gravity and light transduction pathways has advanced through the use of mutants in either gravitropic or phototropic responses and the use of innovative techniques that reduce the effects of one stimulus on the other. Thus, both unique and common elements in the transduction pathways of the gravitropic and phototropic responses have been isolated. This article is focused on the interactions between the light- and gravity-transduction pathways and describes methods used to separate the influences of these two environmental stimuli.

Interactions between gravitropism and phototropism in plants.

PubMed

Correll, Melanie J; Kiss, John Z

2002-06-01

To receive adequate light and nutrients for survival, plants orient stems and stem-like organs toward light and away from the gravity vector and, conversely, orient roots into the soil, away from light toward the direction of gravity. Therefore, both gravity and light can influence the differential growth of plant organs. To add to the complexity of the interactions between gravity and light, each stimulus can enhance or reduce the effectiveness of the other. On earth, the constant presence of gravity makes it difficult to determine whether plant growth and development is influenced by gravity or light alone or the combination of the two stimuli. In the past decade, our understanding of the gravity and light transduction pathways has advanced through the use of mutants in either gravitropic or phototropic responses and the use of innovative techniques that reduce the effects of one stimulus on the other. Thus, both unique and common elements in the transduction pathways of the gravitropic and phototropic responses have been isolated. This article is focused on the interactions between the light- and gravity-transduction pathways and describes methods used to separate the influences of these two environmental stimuli.

Dissociation of verbal working memory system components using a delayed serial recall task.

PubMed

Chein, J M; Fiez, J A

2001-11-01

Functional magnetic resonance imaging (fMRI) was used to investigate the neural substrates of component processes in verbal working memory. Based on behavioral research using manipulations of verbal stimulus type to dissociate storage, rehearsal, and executive components of verbal working memory, we designed a delayed serial recall task requiring subjects to encode, maintain, and overtly recall sets of verbal items for which phonological similarity, articulatory length, and lexical status were manipulated. By using a task with temporally extended trials, we were able to exploit the temporal resolution afforded by fMRI to partially isolate neural contributions to encoding, maintenance, and retrieval stages of task performance. Several regions commonly associated with maintenance, including supplementary motor, premotor, and inferior frontal areas, were found to be active across all three trial stages. Additionally, we found that left inferior frontal and supplementary motor regions showed patterns of stimulus and temporal sensitivity implicating them in distinct aspects of articulatory rehearsal, while no regions showed a pattern of sensitivity consistent with a role in phonological storage. Regional modulation by task difficulty was further investigated as a measure of executive processing. We interpret our findings as they relate to notions about the cognitive architecture underlying verbal working memory performance.

A review and guidance for pattern selection in spatiotemporal system

NASA Astrophysics Data System (ADS)

Wang, Chunni; Ma, Jun

2018-03-01

Pattern estimation and selection in media can give important clues to understand the collective response to external stimulus by detecting the observable variables. Both reaction-diffusion systems (RDs) and neuronal networks can be treated as multi-agent systems from molecular level, intrinsic cooperation, competition. An external stimulus or attack can cause collapse of spatial order and distribution, while appropriate noise can enhance the consensus in the spatiotemporal systems. Pattern formation and synchronization stability can bridge isolated oscillators and the network by coupling these nodes with appropriate connection types. As a result, the dynamical behaviors can be detected and discussed by developing different spatial patterns and realizing network synchronization. Indeed, the collective response of network and multi-agent system depends on the local kinetics of nodes and cells. It is better to know the standard bifurcation analysis and stability control schemes before dealing with network problems. In this review, dynamics discussion and synchronization control on low-dimensional systems, pattern formation and synchronization stability on network, wave stability in RDs and neuronal network are summarized. Finally, possible guidance is presented when some physical effects such as polarization field and electromagnetic induction are considered.

Lesions of the fornix and anterior thalamic nuclei dissociate different aspects of hippocampal-dependent spatial learning: implications for the neural basis of scene learning.

PubMed

Aggleton, John P; Poirier, Guillaume L; Aggleton, Hugh S; Vann, Seralynne D; Pearce, John M

2009-06-01

The present study used 2 different discrimination tasks designed to isolate distinct components of visuospatial learning: structural learning and geometric learning. Structural learning refers to the ability to learn the precise combination of stimulus identity with stimulus location. Rats with anterior thalamic lesions and fornix lesions were unimpaired on a configural learning task in which the rats learned 3 concurrent mirror-image discriminations (structural learning). Indeed, both lesions led to facilitated learning. In contrast, anterior thalamic lesions impaired the geometric discrimination (e.g., swim to the corner with the short wall to the right of the long wall). Finally, both the fornix and anterior thalamic lesions severely impaired T-maze alternation, a task that taxes an array of spatial strategies including allocentric learning. This pattern of dissociations and double dissociations highlights how distinct classes of spatial learning rely on different systems, even though they may converge on the hippocampus. Consequently, the findings suggest that structural learning is heavily dependent on cortico-hippocampal interactions. In contrast, subcortical inputs (such as those from the anterior thalamus) contribute to geometric learning. Copyright (c) 2009 APA, all rights reserved.

Detection and molecular characterization of Escherichia coli CTX-M-15 and Klebsiella pneumoniae SHV-12 β-lactamases from bovine mastitis isolates in the United Kingdom.

PubMed

Timofte, Dorina; Maciuca, Iuliana E; Evans, Nicholas J; Williams, Helen; Wattret, Andrew; Fick, Jenny C; Williams, Nicola J

2014-01-01

Recent reports raised concerns about the role that farm stock may play in the dissemination of extended-spectrum β-lactamase (ESBL)-producing bacteria. This study characterized the ESBLs in two Escherichia coli and three Klebsiella pneumoniae subsp. pneumoniae isolates from cases of clinical bovine mastitis in the United Kingdom. Bacterial culture and sensitivity testing of bovine mastitic milk samples identified Gram-negative cefpodoxime-resistant isolates, which were assessed for their ESBL phenotypes. Conjugation experiments and PCR-based replicon typing (PBRT) were used for characterization of transferable plasmids. E. coli isolates belonged to sequence type 88 (ST88; determined by multilocus sequence typing) and carried blaCTX-M-15 and blaTEM-1, while K. pneumoniae subsp. pneumoniae isolates carried blaSHV-12 and blaTEM-1. Conjugation experiments demonstrated that blaCTX-M-15 and blaTEM-1 were carried on a conjugative plasmid in E. coli, and PBRT identified this to be an IncI1 plasmid. The resistance genes were nontransferable in K. pneumoniae subsp. pneumoniae isolates. Moreover, in the E. coli isolates, an association of ISEcp1 and IS26 with blaCTX-M-15 was found where the IS26 element was inserted upstream of both ISEcp1 and the blaCTX-M promoter, a genetic arrangement highly similar to that described in some United Kingdom human isolates. We report the first cases in Europe of bovine mastitis due to E. coli CTX-M-15 and also of bovine mastitis due to K. pneumoniae subsp. pneumoniae SHV-12 β-lactamases in the United Kingdom. We also describe the genetic environment of blaCTX-M-15 and highlight the role that IncI1 plasmids may play in the spread and dissemination of ESBL genes, which have been described in both human and cattle isolates.

Detection and Molecular Characterization of Escherichia coli CTX-M-15 and Klebsiella pneumoniae SHV-12 β-Lactamases from Bovine Mastitis Isolates in the United Kingdom

PubMed Central

Maciuca, Iuliana E.; Evans, Nicholas J.; Williams, Helen; Wattret, Andrew; Fick, Jenny C.; Williams, Nicola J.

2014-01-01

Recent reports raised concerns about the role that farm stock may play in the dissemination of extended-spectrum β-lactamase (ESBL)-producing bacteria. This study characterized the ESBLs in two Escherichia coli and three Klebsiella pneumoniae subsp. pneumoniae isolates from cases of clinical bovine mastitis in the United Kingdom. Bacterial culture and sensitivity testing of bovine mastitic milk samples identified Gram-negative cefpodoxime-resistant isolates, which were assessed for their ESBL phenotypes. Conjugation experiments and PCR-based replicon typing (PBRT) were used for characterization of transferable plasmids. E. coli isolates belonged to sequence type 88 (ST88; determined by multilocus sequence typing) and carried blaCTX-M-15 and blaTEM-1, while K. pneumoniae subsp. pneumoniae isolates carried blaSHV-12 and blaTEM-1. Conjugation experiments demonstrated that blaCTX-M-15 and blaTEM-1 were carried on a conjugative plasmid in E. coli, and PBRT identified this to be an IncI1 plasmid. The resistance genes were nontransferable in K. pneumoniae subsp. pneumoniae isolates. Moreover, in the E. coli isolates, an association of ISEcp1 and IS26 with blaCTX-M-15 was found where the IS26 element was inserted upstream of both ISEcp1 and the blaCTX-M promoter, a genetic arrangement highly similar to that described in some United Kingdom human isolates. We report the first cases in Europe of bovine mastitis due to E. coli CTX-M-15 and also of bovine mastitis due to K. pneumoniae subsp. pneumoniae SHV-12 β-lactamases in the United Kingdom. We also describe the genetic environment of blaCTX-M-15 and highlight the role that IncI1 plasmids may play in the spread and dissemination of ESBL genes, which have been described in both human and cattle isolates. PMID:24247146

Development and validation of primary human myometrial cell culture models to study pregnancy and labour.

PubMed

Mosher, Andrea A; Rainey, Kelly J; Bolstad, Seunghwa S; Lye, Stephen J; Mitchell, Bryan F; Olson, David M; Wood, Stephen L; Slater, Donna M

2013-01-01

The development of the in vitro cell culture model has greatly facilitated the ability to study gene expression and regulation within human tissues. Within the human uterus, the upper (fundal) segment and the lower segment may provide distinct functions throughout pregnancy and during labour. We have established primary cultured human myometrial cells, isolated from both upper and lower segment regions of the pregnant human uterus, and validated them for the purpose of studying human pregnancy and labour. The specific objectives of this study were to monitor the viability and characterize the expression profile using selected cellular, contractile and pregnancy associated markers in the primary cultured human myometrial cells. Labour has been described as an inflammatory process; therefore, the ability of these cells to respond to an inflammatory stimulus was also investigated. Myometrial cells isolated from paired upper segment (US) and lower segment (LS) biopsies, obtained from women undergoing Caesarean section deliveries at term prior to the onset of labour, were used to identify expression of; α smooth muscle actin, calponin, caldesmon, connexin 43, cyclo-oxygenase-2 (COX-2), oxytocin receptor, tropomyosin and vimentin, by RT-PCR and/or immunocytochemistry. Interleukin (IL)-1β was used to treat cells, subsequently expression of COX-2 mRNA and release of interleukin-8 (CXCL8), were measured. ANOVA followed by Bonferroni's multiple comparisons test was performed. We demonstrate that US and LS human myometrial cells stably express all markers examined to at least passage ten (p10). Connexin 43, COX-2 and vimentin mRNA expression were significantly higher in LS cells compared to US cells. Both cell populations respond to IL-1β, demonstrated by a robust release of CXCL8 and increased expression of COX-2 mRNA from passage one (p1) through to p10. Isolated primary myometrial cells maintain expression of smooth muscle and pregnancy-associated markers and retain their ability to respond to an inflammatory stimulus. These distinct myometrial cell models will provide a useful tool to investigate mechanisms underlying the process of human labour and the concept of functional regionalization of the pregnant uterus.

Combining MRI and VEP imaging to isolate the temporal response of visual cortical areas

NASA Astrophysics Data System (ADS)

Carney, Thom; Ales, Justin; Klein, Stanley A.

2008-02-01

The human brain has well over 30 cortical areas devoted to visual processing. Classical neuro-anatomical as well as fMRI studies have demonstrated that early visual areas have a retinotopic organization whereby adjacent locations in visual space are represented in adjacent areas of cortex within a visual area. At the 2006 Electronic Imaging meeting we presented a method using sprite graphics to obtain high resolution retinotopic visual evoked potential responses using multi-focal m-sequence technology (mfVEP). We have used this method to record mfVEPs from up to 192 non overlapping checkerboard stimulus patches scaled such that each patch activates about 12 mm2 of cortex in area V1 and even less in V2. This dense coverage enables us to incorporate cortical folding constraints, given by anatomical MRI and fMRI results from the same subject, to isolate the V1 and V2 temporal responses. Moreover, the method offers a simple means of validating the accuracy of the extracted V1 and V2 time functions by comparing the results between left and right hemispheres that have unique folding patterns and are processed independently. Previous VEP studies have been contradictory as to which area responds first to visual stimuli. This new method accurately separates the signals from the two areas and demonstrates that both respond with essentially the same latency. A new method is introduced which describes better ways to isolate cortical areas using an empirically determined forward model. The method includes a novel steady state mfVEP and complex SVD techniques. In addition, this evolving technology is put to use examining how stimulus attributes differentially impact the response in different cortical areas, in particular how fast nonlinear contrast processing occurs. This question is examined using both state triggered kernel estimation (STKE) and m-sequence "conditioned kernels". The analysis indicates different contrast gain control processes in areas V1 and V2. Finally we show that our m-sequence multi-focal stimuli have advantages for integrating EEG and MEG for improved dipole localization.

Molecular Phylogeny of the Psittacid Herpesviruses Causing Pacheco's Disease: Correlation of Genotype with Phenotypic Expression

PubMed Central

Tomaszewski, Elizabeth K.; Kaleta, Erhard F.; Phalen, David N.

2003-01-01

Fragments of 419 bp of the UL16 open reading frame from 73 psittacid herpesviruses (PsHVs) from the United States and Europe were sequenced. All viruses caused Pacheco's disease, and serotypes of the European isolates were known. A phylogenetic tree derived from these sequences demonstrated that the PsHVs that cause Pacheco's disease comprised four major genotypes, with each genotype including between two and four variants. With the exception of two viruses, the serotypes of the virus isolates could be predicted by the genotypes. Genotypes 1 and 4 corresponded to serotype 1 isolates, genotype 2 corresponded to serotype 2 isolates, and genotype 3 corresponded to serotype 3 isolates. The single serotype 4 virus mapped to genotype 4. DNA from a virus with a unique serotype could not be amplified with primers that amplified DNA from all other PsHVs, and its classification remains unknown. Viruses representing all four genotypes were found in both the United States and Europe, and it was therefore predicted that serotypes 1, 2, and 3 were present in the United States. Serotype 4 was represented by a single European isolate that could not be genetically distinguished from serotype 1 viruses; therefore, the presence of serotype 4 in the United States could not be predicted. Viruses of genotype 4 were found to be the most commonly associated with Pacheco's disease in macaws and conures and were least likely to be isolated in chicken embryo fibroblasts in the United States. All four genotypes caused deaths in Amazon parrots, but genotype 4 was associated with Pacheco's disease only in Amazons in Europe. Genotypes 2, 3, and 4, but not 1, were found in African grey parrots. Although parrots from the Pacific distribution represent a relatively small percentage of the total number of birds with Pacheco's disease, all four genotypes were found to cause disease in these species. PMID:14512573

Microbiological assessment of indoor air of a teaching hospital in Nigeria.

PubMed

Awosika, S A; Olajubu, F A; Amusa, N A

2012-06-01

To investigate the quality of indoor air of different wards and units of Olabisi Onabanjo University Teaching Hospital, Sagamu, to ascertain their contribution to infection rate in the hospital. The microbial quality of indoor air of nine wards/units of Olabisi Onabanjo University Teaching Hospital, Sagamu, Nigeria was conducted. Sedimentation technique using open Petri-dishes containing different culture media was employed and samplings were done twice daily, one in the morning shortly after cleaning and before influx of people/patients into the wards/units and the other in the evening when a lot of activities would have taken place in these wards. Isolates were identified according to standard methods. Results showed that there was a statistically significant difference (χ(2) = 6.016 7) in the bacteria population of the different sampling time whereas it was not so for fungi population (χ(2) = 0.285 7). Male medical ward (MMW) and male surgical general (MSG) recorded the highest bacterial and fungal growth while the operating theatre (OT) was almost free of microbial burden. The bacteria isolates were Staphylococcus aureus, Klebsiella sp., Bacillus cereus, Bacillus subtilis, Streptococcus pyogenes and Serratia marscences while the fungi isolates included Aspergillus flavus, Penicillium sp., Fusarium sp., Candida albicans and Alternaria sp. Staphylococcus aureus was the predominantly isolated bacterium while Penicillium sp. was the most isolated fungus. Though most of the microbial isolates were potential and or opportunistic pathogens, there was no correlation between the isolates in this study and the surveillance report of nosocomial infection during the period of study, hence the contribution of the indoor air cannot be established. From the reduction noticed in the morning samples, stringent measures such as proper disinfection and regular cleaning, restriction of patient relatives' movement in and out of the wards/units need to be enforced so as to improve the quality of indoor air of our hospital wards/units.

West Nile Virus Isolation in Human and Mosquitoes, Mexico

PubMed Central

Elizondo-Quiroga, Darwin; Davis, C. Todd; Fernandez-Salas, Ildefonso; Escobar-Lopez, Roman; Olmos, Dolores Velasco; Gastalum, Lourdes Cecilia Soto; Acosta, Magaly Aviles; Elizondo-Quiroga, Armando; Gonzalez-Rojas, Jose I.; Cordero, Juan F. Contreras; Guzman, Hilda; Travassos da Rosa, Amelia; Blitvich, Bradley J.; Barrett, Alan D.T.; Beaty, Barry J.

2005-01-01

West Nile virus has been isolated for the first time in Mexico, from a sick person and from mosquitoes (Culex quinquefasciatus). Partial sequencing and analysis of the 2 isolates indicate that they are genetically similar to other recent isolates from northern Mexico and the western United States. PMID:16229779

Effects of stimulus order on discrimination processes in comparative and equality judgements: data and models.

PubMed

Dyjas, Oliver; Ulrich, Rolf

2014-01-01

In typical discrimination experiments, participants are presented with a constant standard and a variable comparison stimulus and their task is to judge which of these two stimuli is larger (comparative judgement). In these experiments, discrimination sensitivity depends on the temporal order of these stimuli (Type B effect) and is usually higher when the standard precedes rather than follows the comparison. Here, we outline how two models of stimulus discrimination can account for the Type B effect, namely the weighted difference model (or basic Sensation Weighting model) and the Internal Reference Model. For both models, the predicted psychometric functions for comparative judgements as well as for equality judgements, in which participants indicate whether they perceived the two stimuli to be equal or not equal, are derived and it is shown that the models also predict a Type B effect for equality judgements. In the empirical part, the models' predictions are evaluated. To this end, participants performed a duration discrimination task with comparative judgements and with equality judgements. In line with the models' predictions, a Type B effect was observed for both judgement types. In addition, a time-order error, as indicated by shifts of the psychometric functions, and differences in response times were observed only for the equality judgement. Since both models entail distinct additional predictions, it seems worthwhile for future research to unite the two models into one conceptual framework.

Non-invasive method for selection of electrodes and stimulus parameters for FES applications with intrafascicular arrays

NASA Astrophysics Data System (ADS)

Dowden, B. R.; Frankel, M. A.; Normann, R. A.; Clark, G. A.

2012-02-01

High-channel-count intrafascicular electrode arrays provide comprehensive and selective access to the peripheral nervous system. One practical difficulty in using several electrode arrays to evoke coordinated movements in paralyzed limbs is the identification of the appropriate stimulation channels and stimulus parameters to evoke desired movements. Here we present the use of a six degree-of-freedom load cell placed under the foot of a feline to characterize the muscle activation produced by three 100-electrode Utah Slanted Electrode Arrays (USEAs) implanted into the femoral nerves, sciatic nerves, and muscular branches of the sciatic nerves of three cats. Intramuscular stimulation was used to identify the endpoint force directions produced by 15 muscles of the hind limb, and these directions were used to classify the forces produced by each intrafascicular USEA electrode as flexion or extension. For 451 USEA electrodes, stimulus intensities for threshold and saturation muscle forces were identified, and the 3D direction and linearity of the force recruitment curves were determined. Further, motor unit excitation independence for 198 electrode pairs was measured using the refractory technique. This study demonstrates the utility of 3D endpoint force monitoring as a simple and non-invasive metric for characterizing the muscle-activation properties of hundreds of implanted peripheral nerve electrodes, allowing for electrode and parameter selection for neuroprosthetic applications.

Non-invasive method for selection of electrodes and stimulus parameters for FES applications with intrafascicular arrays.

PubMed

Dowden, B R; Frankel, M A; Normann, R A; Clark, G A

2012-02-01

High-channel-count intrafascicular electrode arrays provide comprehensive and selective access to the peripheral nervous system. One practical difficulty in using several electrode arrays to evoke coordinated movements in paralyzed limbs is the identification of the appropriate stimulation channels and stimulus parameters to evoke desired movements. Here we present the use of a six degree-of-freedom load cell placed under the foot of a feline to characterize the muscle activation produced by three 100-electrode Utah Slanted Electrode Arrays (USEAs) implanted into the femoral nerves, sciatic nerves, and muscular branches of the sciatic nerves of three cats. Intramuscular stimulation was used to identify the endpoint force directions produced by 15 muscles of the hind limb, and these directions were used to classify the forces produced by each intrafascicular USEA electrode as flexion or extension. For 451 USEA electrodes, stimulus intensities for threshold and saturation muscle forces were identified, and the 3D direction and linearity of the force recruitment curves were determined. Further, motor unit excitation independence for 198 electrode pairs was measured using the refractory technique. This study demonstrates the utility of 3D endpoint force monitoring as a simple and non-invasive metric for characterizing the muscle-activation properties of hundreds of implanted peripheral nerve electrodes, allowing for electrode and parameter selection for neuroprosthetic applications.

The inferior colliculus encodes the Franssen auditory spatial illusion

PubMed Central

Rajala, Abigail Z.; Yan, Yonghe; Dent, Micheal L.; Populin, Luis C.

2014-01-01

Illusions are effective tools for the study of the neural mechanisms underlying perception because neural responses can be correlated to the physical properties of stimuli and the subject’s perceptions. The Franssen illusion (FI) is an auditory spatial illusion evoked by presenting a transient, abrupt tone and a slowly rising, sustained tone of the same frequency simultaneously on opposite sides of the subject. Perception of the FI consists of hearing a single sound, the sustained tone, on the side that the transient was presented. Both subcortical and cortical mechanisms for the FI have been proposed, but, to date, there is no direct evidence for either. The data show that humans and rhesus monkeys perceive the FI similarly. Recordings were taken from single units of the inferior colliculus in the monkey while they indicated the perceived location of sound sources with their gaze. The results show that the transient component of the Franssen stimulus, with a shorter first spike latency and higher discharge rate than the sustained tone, encodes the perception of sound location. Furthermore, the persistent erroneous perception of the sustained stimulus location is due to continued excitation of the same neurons, first activated by the transient, by the sustained stimulus without location information. These results demonstrate for the first time, on a trial-by-trial basis, a correlation between perception of an auditory spatial illusion and a subcortical physiological substrate. PMID:23899307

Encoding of the amplitude modulation of pulsatile electrical stimulation in the feline cochlear nucleus by neurons in the inferior colliculus; effects of stimulus pulse rate

NASA Astrophysics Data System (ADS)

McCreery, Douglas; Han, Martin; Pikov, Victor; Yadav, Kamal; Pannu, Satinderpall

2013-10-01

Objectives. Persons without a functional auditory nerve cannot benefit from cochlear implants, but some hearing can be restored by an auditory brainstem implant (ABI) with stimulating electrodes implanted on the surface of the cochlear nucleus (CN). Most users benefit from their ABI, but speech recognition tends to be poorer than for users of cochlear implants. Psychophysical studies suggest that poor modulation detection may contribute to the limited performance of ABI users. In a cat model, we determined how the pulse rate of the electrical stimulus applied within or on the CN affects temporal and rate encoding of amplitude modulation (AM) by neurons in the central nucleus of the inferior colliculus (ICC). Approach. Stimulating microelectrodes were implanted chronically in and on the cats' CN, and multi-site recording microelectrodes were implanted chronically into the ICC. Encoding of AM pulse trains by neurons in the ICC was characterized as vector strength (VS), the synchrony of neural activity with the AM, and as the mean rate of neuronal action potentials (neuronal spike rate (NSR)). Main results. For intranuclear microstimulation, encoding of AM as VS was up to 3 dB greater when stimulus pulse rate was increased from 250 to 500 pps, but only for neuronal units with low best acoustic frequencies, and when the electrical stimulation was modulated at low frequencies (10-20 Hz). For stimulation on the surface of the CN, VS was similar at 250 and 500 pps, and the dynamic range of the VS was reduced for pulse rates greater than 250 pps. Modulation depth was encoded strongly as VS when the maximum stimulus amplitude was held constant across a range of modulation depth. This ‘constant maximum’ protocol allows enhancement of modulation depth while preserving overall dynamic range. However, modulation depth was not encoded as strongly as NSR. Significance. The findings have implications for improved sound processors for present and future ABIs. The performance of ABIs may benefit from using pulse rates greater than those presently used in most ABIs, and by sound processing strategies that enhance the modulation depth of the electrical stimulus while preserving dynamic range.

The occurrence of mycoplasmas in selected wild North American waterfowl

USGS Publications Warehouse

Goldberg, Diana R.; Samuel, M.D.; Thomas, C.B.; Sharp, P.; Krapu, G.L.; Robb, J.R.; Kenow, K.P.; Korschgen, C.E.; Chipley, W.H.; Conroy, M.J.; Kleven, S.H.

1995-01-01

We determined the prevalence of mycoplasma infection in breeding mallard (Anas platyrhynchos) and canvasback (Aythya valisineria) hens and their broods from the central United States (1988 to 1990); and wintering American black duck (Anas rubripes) and mallard hens from the eastern United States (1990 to 1993). Mycoplasmas were isolated by culturing tracheal swabs from 656 live birds and tissue samples from 112 dead waterfowl. Nine (18%) of 51 mycoplasma isolates were identified as Mycoplasma anatis; M. anatis was recovered from four mallards, a black duck, and a gadwall (Anas strepera) duckling. Nineteen (37%) of 51 mycoplasma isolates were identified as Mycoplasma cloacale; these isolates were obtained from mallard, canvasback, and black duck adults, and from a mallard duckling. Additional unspeciated mycoplasmas were isolated from mallards, black ducks, and one canvasback.

Extraintestinal Pathogenic and Antimicrobial-Resistant Escherichia coli, Including Sequence Type 131 (ST131), from Retail Chicken Breasts in the United States in 2013

PubMed Central

Porter, Stephen B.; Johnston, Brian; Thuras, Paul; Clock, Sarah; Crupain, Michael; Rangan, Urvashi

2017-01-01

ABSTRACT Chicken meat products are hypothesized to be vehicles for transmitting antimicrobial-resistant and extraintestinal pathogenic Escherichia coli (ExPEC) to consumers. To reassess this hypothesis in the current era of heightened concerns about antimicrobial use in food animals, we analyzed 175 chicken-source E. coli isolates from a 2013 Consumer Reports national survey. Isolates were screened by PCR for ExPEC-defining virulence genes. The 25 ExPEC isolates (12% of 175) and a 2:1 randomly selected set of 50 non-ExPEC isolates were assessed for their phylogenetic/clonal backgrounds and virulence genotypes for comparison with their resistance profiles and the claims on the retail packaging label (“organic,” “no antibiotics,” and “natural”). Compared with the findings for non-ExPEC isolates, the group of ExPEC isolates had a higher prevalence of phylogroup B2 isolates (44% versus 4%; P < 0.001) and a lower prevalence of phylogroup A isolates (4% versus 30%; P = 0.001), a higher prevalence of multiple individual virulence genes, higher virulence scores (median, 11 [range, 4 to 16] versus 8 [range, 1 to 14]; P = 0.001), and higher resistance scores (median, 4 [range, 0 to 8] versus 3 [range, 0 to 10]; P < 0.001). All five isolates of sequence type 131 (ST131) were ExPEC (P = 0.003), were as extensively resistant as the other isolates tested, and had higher virulence scores than the other isolates tested (median, 12 [range, 11 to 13] versus 8 [range, 1 to 16]; P = 0.005). Organic labeling predicted lower resistance scores (median, 2 [range, 0 to 3] versus 4 [range, 0 to 10]; P = 0.008) but no difference in ExPEC status or virulence scores. These findings document a persisting reservoir of extensively antimicrobial-resistant ExPEC isolates, including isolates from ST131, in retail chicken products in the United States, suggesting a potential public health threat. IMPORTANCE We found that among Escherichia coli isolates from retail chicken meat products purchased across the United States in 2013 (many of these isolates being extensively antibiotic resistant), a minority had genetic profiles suggesting an ability to cause extraintestinal infections in humans, such as urinary tract infection, implying a risk of foodborne disease. Although isolates from products labeled “organic” were less extensively antibiotic resistant than other isolates, they did not appear to be less virulent. These findings suggest that retail chicken products in the United States, even if they are labeled “organic,” pose a potential health threat to consumers because they are contaminated with extensively antibiotic-resistant and, presumably, virulent E. coli isolates. PMID:28062464

Auditory thresholds in the American cockroach (Orthoptera: Blattidae): estimates using single-unit and compound-action potential recordings.

PubMed

Decker, T N; Jones, T A; Gold, R E

1989-06-01

Recent commercial suggestions that insect populations can be controlled through the use of ultrasound raises the question of whether or not certain insects have receptors that are sensitive to high-frequency sound. Single neural unit discharges and compound-action potentials were recorded from the ventral nerve cord in the American cockroach, Periplaneta americana L., to constant rise time tone pulses from 100 to 40,000 hertz (Hz). Unit responses and compound-action potentials show that the cockroach is insensitive to sound above approximately 3,000 Hz. Data relating latency of the response to intensity of the stimulus suggest that the cockroach cercal system operates on the principle of energy envelope detection. Decreases in latency likely occur primarily as a result of increases in the rate of membrane depolarization in cercal dendrites.

Pure culture response of ectomycorrhizal fungi to imposed water stress

Treesearch

Mark D. Coleman; Caroline S. Bledsoe; William Lopushinsky

1989-01-01

The ability of ectomycorrhizal fungal isolates to tolerate imposed water stress in pure culture was examined in 55 isolates of 18 species. Water potential treatments, adjusted with polyethylene glycol, were applied to Petri dish units. These units allowed colony diameter measurements of fungi grown on liquid media. Delayed growth initiation and inhibition of growth...

Importance of Carolina Bays to the Avifauna of Pinelands in the Southeastern United States

Treesearch

Stephen Czapka; John Kilgo

2011-01-01

Past anthropogenic activity has led to the destruction or alteration of Carolina bay wetlands throughout the southeastern United States. Presently, urban development, combined with a 2001 ruling by the US Supreme Court relaxing protection of isolated wetlands, poses an increasing threat to these and other isolated wetland systems; however, little information exists on...

A detailed description of the sequential probability ratio test for 2-IMU FDI

NASA Technical Reports Server (NTRS)

Rich, T. M.

1976-01-01

The sequential probability ratio test (SPRT) for 2-IMU FDI (inertial measuring unit failure detection/isolation) is described. The SPRT is a statistical technique for detecting and isolating soft IMU failures originally developed for the strapdown inertial reference unit. The flowchart of a subroutine incorporating the 2-IMU SPRT is included.

Hypervirulent emm59 Clone in Invasive Group A Streptococcus Outbreak, Southwestern United States.

PubMed

Engelthaler, David M; Valentine, Michael; Bowers, Jolene; Pistole, Jennifer; Driebe, Elizabeth M; Terriquez, Joel; Nienstadt, Linus; Carroll, Mark; Schumacher, Mare; Ormsby, Mary Ellen; Brady, Shane; Livar, Eugene; Yazzie, Del; Waddell, Victor; Peoples, Marie; Komatsu, Kenneth; Keim, Paul

2016-04-01

The hyper-virulent emm59 genotype of invasive group A Streptococcus was identified in northern Arizona in 2015. Eighteen isolates belonging to a genomic cluster grouped most closely with recently identified isolates in New Mexico. The continued transmission of emm59 in the southwestern United States poses a public health concern.

Functional mapping of the primate auditory system.

PubMed

Poremba, Amy; Saunders, Richard C; Crane, Alison M; Cook, Michelle; Sokoloff, Louis; Mishkin, Mortimer

2003-01-24

Cerebral auditory areas were delineated in the awake, passively listening, rhesus monkey by comparing the rates of glucose utilization in an intact hemisphere and in an acoustically isolated contralateral hemisphere of the same animal. The auditory system defined in this way occupied large portions of cerebral tissue, an extent probably second only to that of the visual system. Cortically, the activated areas included the entire superior temporal gyrus and large portions of the parietal, prefrontal, and limbic lobes. Several auditory areas overlapped with previously identified visual areas, suggesting that the auditory system, like the visual system, contains separate pathways for processing stimulus quality, location, and motion.

The importance of unitization for familiarity-based learning.

PubMed

Parks, Colleen M; Yonelinas, Andrew P

2015-05-01

It is often assumed that recollection is necessary to support memory for novel associations, whereas familiarity supports memory for single items. However, the levels of unitization framework assumes that familiarity can support associative memory under conditions in which the components of an association are unitized (i.e., treated as a single coherent item). In the current study we tested two critical assumptions of this framework. First, does unitization reflect a specialized form of learning or is it simply a form of semantic or elaborative encoding, and, second, can the beneficial effects of unitization on familiarity be observed for across-domain associations or are they limited to creating new associations between items that are from the same stimulus domains? Unitization was found to increase associative recognition but not item recognition. It affected familiarity more than recollection, increased associative but not item priming, and was dissociable from levels of processing effects. Moreover, unitization effects were found to be particularly effective in supporting face-word and fractal-sound pairs. The current results indicate that unitization reflects a specialized form of learning that supports associative familiarity of within- and across-domain associations. (c) 2015 APA, all rights reserved).

The importance of unitization for familiarity-based learning

PubMed Central

Parks, Colleen M.; Yonelinas, Andrew P.

2014-01-01

It is often assumed that recollection is necessary to support memory for novel associations, whereas familiarity supports memory for single items. However, the levels of unitization (LOU) framework assumes that familiarity can support associative memory under conditions in which the components of an association are unitized (i.e., treated as a single coherent item). In the current study we test two critical assumptions of this framework. First, does unitization reflect a specialized form of learning or is it simply a form of semantic or elaborative encoding, and, second, can the beneficial effects of unitization on familiarity be observed for across-domain associations or are they limited to creating new associations between items that are from the same stimulus domains? Unitization was found to increase associative recognition but not item recognition, it affected familiarity more so than recollection, it increased associative but not item priming, and it was dissociable from levels of processing effects. Moreover, unitization effects were found to be particularly effective in supporting face-word and fractal-sound pairs. The current results indicate that unitization reflects a specialized form of learning that supports associative familiarity of within- and across-domain associations. PMID:25329077

Parallel and orthogonal stimulus in ultradiluted neural networks

NASA Astrophysics Data System (ADS)

Sobral, G. A., Jr.; Vieira, V. M.; Lyra, M. L.; da Silva, C. R.

2006-10-01

Extending a model due to Derrida, Gardner, and Zippelius, we have studied the recognition ability of an extreme and asymmetrically diluted version of the Hopfield model for associative memory by including the effect of a stimulus in the dynamics of the system. We obtain exact results for the dynamic evolution of the average network superposition. The stimulus field was considered as proportional to the overlapping of the state of the system with a particular stimulated pattern. Two situations were analyzed, namely, the external stimulus acting on the initialization pattern (parallel stimulus) and the external stimulus acting on a pattern orthogonal to the initialization one (orthogonal stimulus). In both cases, we obtained the complete phase diagram in the parameter space composed of the stimulus field, thermal noise, and network capacity. Our results show that the system improves its recognition ability for parallel stimulus. For orthogonal stimulus two recognition phases emerge with the system locking at the initialization or stimulated pattern. We confront our analytical results with numerical simulations for the noiseless case T=0 .

Analysis of clinical and food-borne isolates of Listeria monocytogenes in the United States by multilocus enzyme electrophoresis and application of the method to epidemiologic investigations.

PubMed Central

Bibb, W F; Gellin, B G; Weaver, R; Schwartz, B; Plikaytis, B D; Reeves, M W; Pinner, R W; Broome, C V

1990-01-01

To investigate the microbiology and epidemiology of the 1,700 sporadic cases of listeriosis that occur annually in the United States, we developed a multilocus enzyme electrophoresis (MEE) typing system for Listeria monocytogenes. We studied 390 isolates by MEE. Eighty-two electrophoretic types (ETs) were defined. Two distinct clusters of ETs, ET group A (ETGA) and ET group B (ETGB), separated at a genetic distance of 0.440, were identified. Strains of ETGB were associated with perinatal listeriosis (P = 0.03). All strains of H antigen type a were in ETGA, while all strains of H antigen type b were in ETGB. Among 328 clinical isolates from cases of literiosis, 55 ETs of L. monocytogenes were defined. Thirty-four ETs were identified among 62 isolates from food products. The mean number of strains per ET (5.2) was significantly higher among clinical isolates than among food-borne isolates. Examination of isolates from outbreaks further documented the link between cases and contaminated food products. In one investigation, we found 11 different ETs, ruling out a single common source as a cause of that outbreak. By examining a large number of isolates collected over a specified time in diverse geographic locations in the United States, we have begun to establish a baseline for the study of the epidemiology of listeriosis by MEE. PMID:2117880

Effects of Carbon Dioxide and Oxygen Levels on Auditory Sensitivity and Frequency Tuning as Measured by the Stimulus Frequency Otoacoustic Emission Test

DTIC Science & Technology

2009-09-14

support of this project in arranging diver schedules so they could serve as study participants. The authors also wish to thank staff at Mimosa Acoustics...however, has now been implemented in a commercial unit, the Mimosa Acoustics SFOAE system. SFOAEs potentially provide more frequency-specific...Medical Research Laboratory, Massachusetts Eye and Ear Infirmary, and Mimosa Acoustics, Inc. (Lapsley Miller, Boege, Marshall, Shera, and Jeng, 2004

A Study to Determine the Perception of Unintended Messages by Viewers of two United States Army Television Commercials.

DTIC Science & Technology

1991-11-29

inter,:reted in ways not intended; the percepLion of subliminal messages is based on demographic characteristics and subculture influence; and...receiver and sender, and must be dealt with accordingly. For instance, if the sender of the message must compete with a louder auditory stimulus, this...these themes. Hoijer concluded that television programs do stimulate thought processes, and there is a connection between the contents 18 of the program

Properties of human motoneurones and their synaptic noise deduced from motor unit recordings with the aid of computer modelling.

PubMed

Matthews, P B

1999-01-01

This paper reviews two new facets of the behaviour of human motoneurones; these were demonstrated by modelling combined with analysis of long periods of low-frequency tonic motor unit firing (sub-primary range). 1) A novel transformation of the interval histogram has shown that the effective part of the membrane's post-spike voltage trajectory is a segment of an exponential (rather than linear), with most spikes being triggered by synaptic noise before the mean potential reaches threshold. The curvature of the motoneurone's trajectory affects virtually all measures of its behaviour and response to stimulation. The 'trajectory' is measured from threshold, and so includes any changes in threshold during the interspike interval. 2) A novel rhythmic stimulus (amplitude-modulated pulsed vibration) has been used to show that the motoneurone produces appreciable phase-advance during sinusoidal excitation. At low frequencies, the advance increases with rising stimulus frequency but then, slightly below the motoneurones mean firing rate, it suddenly becomes smaller. The gain has a maximum for stimuli at the mean firing rate (the 'carrier'). Such behaviour is functionally important since it affects the motoneurone's response to any rhythmic input, whether generated peripherally by the receptors (as in tremor) or by the CNS (as with cortical oscillations). Low mean firing rates favour tremor, since the high gain and reduced phase advance at the 'carrier' reduce the stability of the stretch reflex.

Comparative phenotypic and genotypic analyses of Salmonella Rissen that originated from food animals in Thailand and United States.

PubMed

Pornsukarom, S; Patchanee, P; Erdman, M; Cray, P F; Wittum, T; Lee, J; Gebreyes, W A

2015-03-01

Salmonella enterica serovar Rissen has been recognized as one of the most common serovar among humans and pork production systems in different parts of the world, especially Asia. In the United States, this serovar caused outbreaks but its epidemiologic significance remains unknown. The objectives of this study were to compare the phenotypic (antimicrobial susceptibility) and genotypic attributes of Salmonella Rissen isolated in Thailand (Thai) and the United States (US). All the Thai isolates (n = 30) were recovered from swine faecal samples. The US isolates (n = 35) were recovered from swine faecal samples (n = 29), cattle (n = 2), chicken (n = 2), dog (n = 1) and a ready-to-eat product (n = 1). The antimicrobial susceptibility of isolates was determined using the Kirby-Bauer disk diffusion method with a panel of 12 antimicrobials. Pulse-field gel electrophoresis (PFGE) was used to determine the genotypic diversity of isolates. All Thai isolates showed multidrug resistance (MDR) with the most frequent antibiotic resistance shown against ampicillin (100%), sulfisoxazole (96.7%), tetracycline (93.3%), streptomycin (90%) and chloramphenicol (30%). About half of the isolates of USA origin were pan-susceptible and roughly 30% were resistant to only tetracycline (R-type: Te). Salmonella Rissen isolated from Thailand and the USA in this study were found to be clonally unrelated. Genotypic analyses indicated that isolates were clustered primarily based on the geographic origin implying the limited clonality among the strains. Clonal relatedness among different host species within the same geography (USA) was found. We found genotypic similarity in Thai and US isolates in few instances but with no epidemiological link. Further studies to assess propensity for increased inter-regional transmission and dissemination is warranted. © 2014 Blackwell Verlag GmbH.

A Shared Population of Epidemic Methicillin-Resistant Staphylococcus aureus 15 Circulates in Humans and Companion Animals

PubMed Central

Harrison, Ewan M.; Weinert, Lucy A.; Holden, Matthew T. G.; Welch, John J.; Wilson, Katherine; Morgan, Fiona J. E.; Harris, Simon R.; Loeffler, Anette; Boag, Amanda K.; Peacock, Sharon J.; Paterson, Gavin K.; Waller, Andrew S.; Parkhill, Julian

2014-01-01

ABSTRACT Methicillin-resistant Staphylococcus aureus (MRSA) is a global human health problem causing infections in both hospitals and the community. Companion animals, such as cats, dogs, and horses, are also frequently colonized by MRSA and can become infected. We sequenced the genomes of 46 multilocus sequence type (ST) 22 MRSA isolates from cats and dogs in the United Kingdom and compared these to an extensive population framework of human isolates from the same lineage. Phylogenomic analyses showed that all companion animal isolates were interspersed throughout the epidemic MRSA-15 (EMRSA-15) pandemic clade and clustered with human isolates from the United Kingdom, with human isolates basal to those from companion animals, suggesting a human source for isolates infecting companion animals. A number of isolates from the same veterinary hospital clustered together, suggesting that as in human hospitals, EMRSA-15 isolates are readily transmitted in the veterinary hospital setting. Genome-wide association analysis did not identify any host-specific single nucleotide polymorphisms (SNPs) or virulence factors. However, isolates from companion animals were significantly less likely to harbor a plasmid encoding erythromycin resistance. When this plasmid was present in animal-associated isolates, it was more likely to contain mutations mediating resistance to clindamycin. This finding is consistent with the low levels of erythromycin and high levels of clindamycin used in veterinary medicine in the United Kingdom. This study furthers the “one health” view of infectious diseases that the pathogen pool of human and animal populations are intrinsically linked and provides evidence that antibiotic usage in animal medicine is shaping the population of a major human pathogen. PMID:24825010

Attention modulates spatial priority maps in the human occipital, parietal and frontal cortices

PubMed Central

Sprague, Thomas C.; Serences, John T.

2014-01-01

Computational theories propose that attention modulates the topographical landscape of spatial ‘priority’ maps in regions of visual cortex so that the location of an important object is associated with higher activation levels. While single-unit recording studies have demonstrated attention-related increases in the gain of neural responses and changes in the size of spatial receptive fields, the net effect of these modulations on the topography of region-level priority maps has not been investigated. Here, we used fMRI and a multivariate encoding model to reconstruct spatial representations of attended and ignored stimuli using activation patterns across entire visual areas. These reconstructed spatial representations reveal the influence of attention on the amplitude and size of stimulus representations within putative priority maps across the visual hierarchy. Our results suggest that attention increases the amplitude of stimulus representations in these spatial maps, particularly in higher visual areas, but does not substantively change their size. PMID:24212672

Feature-Based Visual Short-Term Memory Is Widely Distributed and Hierarchically Organized.

PubMed

Dotson, Nicholas M; Hoffman, Steven J; Goodell, Baldwin; Gray, Charles M

2018-06-15

Feature-based visual short-term memory is known to engage both sensory and association cortices. However, the extent of the participating circuit and the neural mechanisms underlying memory maintenance is still a matter of vigorous debate. To address these questions, we recorded neuronal activity from 42 cortical areas in monkeys performing a feature-based visual short-term memory task and an interleaved fixation task. We find that task-dependent differences in firing rates are widely distributed throughout the cortex, while stimulus-specific changes in firing rates are more restricted and hierarchically organized. We also show that microsaccades during the memory delay encode the stimuli held in memory and that units modulated by microsaccades are more likely to exhibit stimulus specificity, suggesting that eye movements contribute to visual short-term memory processes. These results support a framework in which most cortical areas, within a modality, contribute to mnemonic representations at timescales that increase along the cortical hierarchy. Copyright © 2018 Elsevier Inc. All rights reserved.

The effect of the blackout method on acquisition and generalization1

PubMed Central

Wildemann, Donald G.; Holland, James G.

1973-01-01

In discrimination training with the Lyons' blackout method, pecks to the negative stimulus are prevented by darkening the chamber each time the subject approaches the negative stimulus. Stimulus generalization along a stimulus dimension was measured after training with this method. For comparison, generalization was also measured after reinforced responding to the positive stimulus without discrimination training, and after discrimination training by extinction of pecks to the negative stimulus. The blackout procedure and the extinction of pecks to the negative stimulus both produced a peak shift in the generalization gradients. The results suggest that after discrimination training in which the positive and negative stimulus are on the same continuum, the blackout method produces extinction-like effects on generalization tests. PMID:16811655

Anti-extinction in the tactile modality.

PubMed

White, Rebekah C; Aimola Davies, Anne M

2013-01-01

Patients with extinction fail to report a contralesional stimulus when it is presented at the same time as an ipsilesional stimulus, and patients with unilateral neglect fail to report a contralesional stimulus even when there is no competing ipsilesional stimulus. Whereas extinction and neglect are common following stroke, the related phenomenon of anti-extinction is rare--there are four cases of anti-extinction in the literature, and all four cases demonstrated anti-extinction in the visual modality. Patients with anti-extinction do report a contralesional stimulus when it is presented at the same time as an ipsilesional stimulus; but, like patients with neglect, they fail to report a contralesional stimulus when there is no competing ipsilesional stimulus. We present the first case ofanti-extinction in the tactile modality.

Variables influencing stimulus overselectivity and "tunnel vision" in developmentally delayed children.

PubMed

Rincover, A; Ducharme, J M

1987-01-01

Three variables (diagnosis, location of cues, and MA of learners) influencing stimulus control and stimulus overselectivity in autistic children were assessed. Eight autistic and 8 intellectually average children, matched on MA, were trained on two discrimination tasks; one task contained two "within-stimulus" (i.e., physically connected) cues; the other contained the same two cues presented "extra-stimulus" (i.e., physically separate). Generalization gradients were used following training to measure the degree of stimulus control acquired by each cue. Results showed: autistic subjects tended to respond overselectively only in the extra-stimulus condition; MA was positively correlated with breadth of learning; and when autistic children were overselective to one cue, some stimulus control was also acquired by the second cue. The notion of tunnel vision was discussed, as it may represent a "keystone" deficit interfering with stimulus control and learning by autistic children.

Second-order schedules: comparison of different procedures for scheduling paired and nonpaired brief stimuli.

PubMed

Stubbs, D A; Cohen, S L

1972-11-01

Pigeons performed on a second-order schedule in which fixed-interval components were maintained under a variable-interval schedule. Completion of each fixed-interval component resulted in a brief-stimulus presentation and/or food. The relation of the brief stimulus and food was varied across conditions. Under some conditions, the brief stimulus was never paired with food. Under other conditions, the brief stimulus was paired with food; three different pairing procedures were used: (a) a response produced the simultaneous onset of the stimulus and food; (b) a response produced the stimulus before food with the stimulus remaining on during food presentation; (c) a response produced the stimulus and the offset of the stimulus was simultaneous with the onset of the food cycle. The various pairing and nonpairing operations all produced similar effects on performance. Under all conditions, response rates were positively accelerated within fixed-interval components. Total response rates and Index of Curvature measures were similar across conditions. In one condition, a blackout was paired with food; with this different stimulus in effect, less curvature resulted. The results suggest that pairing of a stimulus is not a necessary condition for within-component patterning under some second-order schedules.

Second-order schedules: comparison of different procedures for scheduling paired and nonpaired brief stimuli

PubMed Central

Stubbs, D. Alan; Cohen, Steven L.

1972-01-01

Pigeons performed on a second-order schedule in which fixed-interval components were maintained under a variable-interval schedule. Completion of each fixed-interval component resulted in a brief-stimulus presentation and/or food. The relation of the brief stimulus and food was varied across conditions. Under some conditions, the brief stimulus was never paired with food. Under other conditions, the brief stimulus was paired with food; three different pairing procedures were used: (a) a response produced the simultaneous onset of the stimulus and food; (b) a response produced the stimulus before food with the stimulus remaining on during food presentation; (c) a response produced the stimulus and the offset of the stimulus was simultaneous with the onset of the food cycle. The various pairing and nonpairing operations all produced similar effects on performance. Under all conditions, response rates were positively accelerated within fixed-interval components. Total response rates and Index of Curvature measures were similar across conditions. In one condition, a blackout was paired with food; with this different stimulus in effect, less curvature resulted. The results suggest that pairing of a stimulus is not a necessary condition for within-component patterning under some second-order schedules. PMID:16811634

Effect of substituted benzimidazoles on acid secretion in isolated and enriched guinea pig parietal cells.

PubMed Central

Sewing, K F; Harms, P; Schulz, G; Hannemann, H

1983-01-01

The inhibitory effect of the three benzimidazole derivatives timoprazole, picoprazole, and omeprazole on histamine and dbcAMP stimulated 14C-aminopyrine accumulation (= H+ secretion) has been studied in isolated and enriched guinea-pig parietal cells. All compounds tested inhibited H+ secretion in a concentration dependent manner with IC50 values of 8.5 +/- 1.9 mumol/l for timoprazole, 3.9 +/- 0.7 mumol/l for picoprazole, and 0.13 +/- 0.03 mumol/l for omeprazole. The IC50 of timoprazole, when dbcAMP was used as a stimulus, did not differ significantly from that of histamine stimulation. The type of inhibition was of a non-competitive nature. The full acid response to histamine after temporary exposure of the cells to the benzimidazoles could be restored by washing the cells twice; this suggests that the inhibition is reversible. The data - among others - indicate that the properties of the benzimidazoles described here would allow these compounds to be used as effective antisecretagogues. PMID:6303916

Phenotyping sensory nerve endings in vitro in the mouse

PubMed Central

Zimmermann, Katharina; Hein, Alexander; Hager, Ulrich; Kaczmarek, Jan Stefan; Turnquist, Brian P; Clapham, David E; Reeh, Peter W

2014-01-01

This protocol details methods to identify and record from cutaneous primary afferent axons in an isolated mammalian skin–saphenous nerve preparation. The method is based on extracellular recordings of propagated action potentials from single-fiber receptive fields. Cutaneous nerve endings show graded sensitivities to various stimulus modalities that are quantified by adequate and controlled stimulation of the superfused skin with heat, cold, touch, constant punctate pressure or chemicals. Responses recorded from single-fibers are comparable with those obtained in previous in vivo experiments on the same species. We describe the components and the setting-up of the basic equipment of a skin–nerve recording station (few days), the preparation of the skin and the adherent saphenous nerve in the mouse (15–45 min) and the isolation and recording of neurons (approximately 1–3 h per recording). In addition, stimulation techniques, protocols to achieve single-fiber recordings, issues of data acquisition and action potential discrimination are discussed in detail. PMID:19180088

The Holistic Impact of Classroom Spaces on Learning in Specific Subjects

PubMed Central

Barrett, Peter; Davies, Fay; Zhang, Yufan; Barrett, Lucinda

2016-01-01

The Holistic Evidence and Design (HEAD) study of U.K. primary schools sought to isolate the impact of the physical design of classrooms on the learning progress of pupils aged from 5 to 11 years (U.S. kindergarten to fifth grade). One hundred fifty-three classrooms were assessed and links made to the learning of the 3,766 pupils in them. Through multilevel modeling, the role of physical design was isolated from the influences of the pupils’ characteristics. This article presents analyses for the three main subjects assessed, namely, reading, writing, and math. Variations in the importance of the physical design parameters are revealed for the learning of each subject. In addition to some common factors, such as lighting, a heavy salience for Individualization in relation to math becomes apparent and the importance emerges of Connection for reading and of Links to Nature for writing. Possible explanations are suggested. These results provide a stimulus for additional finesse in practice and for further investigation by researchers. PMID:28458394

Distinguishing response conflict and task conflict in the Stroop task: evidence from ex-Gaussian distribution analysis.

PubMed

Steinhauser, Marco; Hübner, Ronald

2009-10-01

It has been suggested that performance in the Stroop task is influenced by response conflict as well as task conflict. The present study investigated the idea that both conflict types can be isolated by applying ex-Gaussian distribution analysis which decomposes response time into a Gaussian and an exponential component. Two experiments were conducted in which manual versions of a standard Stroop task (Experiment 1) and a separated Stroop task (Experiment 2) were performed under task-switching conditions. Effects of response congruency and stimulus bivalency were used to measure response conflict and task conflict, respectively. Ex-Gaussian analysis revealed that response conflict was mainly observed in the Gaussian component, whereas task conflict was stronger in the exponential component. Moreover, task conflict in the exponential component was selectively enhanced under task-switching conditions. The results suggest that ex-Gaussian analysis can be used as a tool to isolate different conflict types in the Stroop task. PsycINFO Database Record (c) 2009 APA, all rights reserved.

The sympathetic mechanism in the isolated pulmonary artery of the rabbit

PubMed Central

Bevan, J. A.; Su, C.

1964-01-01

The nature of postganglionic sympathetic nervous transmission to vascular muscle in vitro was studied using the recurrent cardiac nerve-pulmonary artery preparation of the rabbit. Experiments, similar to those which in other tissues have provided evidence to support a role for acetylcholine at the sympathetic postganglionic nerve-effector cell junction, were carried out. The contractile response of the isolated artery to acetylcholine was blocked completely by atropine. High concentrations of acetylcholine and of hemicholinium had no effect on the contractile response to sympathetic nerve stimulation. Physostigmine, atropine and hemicholinium were without influence on the relationship between nerve stimulus frequency and response. Yohimbine, bretylium and reserpine blocked completely the response to nerve stimulation but did not affect that to applied acetylcholine. These results support the view that transmission in this preparation at the sympathetic postganglionic nerve-effector cell junction is mediated by an adrenaline-like transmitter and provide no evidence for the view that acetylcholne is involved at this site. PMID:14126048

Laboratory bioassays and field-cage trials of Metarhizium spp. isolates with field-collected Mormon crickets (Anabrus simplex)

USDA-ARS?s Scientific Manuscript database

The Mormon cricket, Anabrus simplex, is an important pest in the western United States. This study evaluates the virulence of 32 isolates of Metarhizium towards field-collected Mormon crickets. Additionally, several isolates were tested in outdoor field-cage studies. All 32 Metarhizium isolates were...

Intracellular origin and ultrastructure of platelet-derived microparticles.

PubMed

Ponomareva, A A; Nevzorova, T A; Mordakhanova, E R; Andrianova, I A; Rauova, L; Litvinov, R I; Weisel, J W

2017-08-01

Essentials Platelet microparticles play a major role in pathologies, including hemostasis and thrombosis. Platelet microparticles have been analyzed and classified based on their ultrastructure. The structure and intracellular origin of microparticles depend on the cell-activating stimulus. Thrombin-treated platelets fall apart and form microparticles that contain cellular organelles. Background Platelet-derived microparticles comprise the major population of circulating blood microparticles that play an important role in hemostasis and thrombosis. Despite numerous studies on the (patho)physiological roles of platelet-derived microparticles, mechanisms of their formation and structural details remain largely unknown. Objectives Here we studied the formation, ultrastructure and composition of platelet-derived microparticles from isolated human platelets, either quiescent or stimulated with one of the following activators: arachidonic acid, ADP, collagen, thrombin or calcium ionophore A23187. Methods Using flow cytometry, transmission and scanning electron microscopy, we analyzed the intracellular origin, structural diversity and size distributions of the subcellular particles released from platelets. Results The structure, dimensions and intracellular origin of microparticles depend on the cell-activating stimulus. The main structural groups include a vesicle surrounded by one thin membrane or multivesicular structures. Thrombin, unlike other stimuli, induced formation of microparticles not only from the platelet plasma membrane and cytoplasm but also from intracellular structures. A fraction of these vesicular particles having an intracellular origin contained organelles, such as mitochondria, glycogen granules and vacuoles. The size of platelet-derived microparticles depended on the nature of the cell-activating stimulus. Conclusion The results obtained provide a structural basis for the qualitative differences of various platelet activators, for specific physiological and pathological effects of microparticles, and for development of advanced assays. © 2017 International Society on Thrombosis and Haemostasis.

Rules, culture, and fitness

PubMed Central

Baum, William M.

1995-01-01

Behavior analysis risks intellectual isolation unless it integrates its explanations with evolutionary theory. Rule-governed behavior is an example of a topic that requires an evolutionary perspective for a full understanding. A rule may be defined as a verbal discriminative stimulus produced by the behavior of a speaker under the stimulus control of a long-term contingency between the behavior and fitness. As a discriminative stimulus, the rule strengthens listener behavior that is reinforced in the short run by socially mediated contingencies, but which also enters into the long-term contingency that enhances the listener's fitness. The long-term contingency constitutes the global context for the speaker's giving the rule. When a rule is said to be “internalized,” the listener's behavior has switched from short- to long-term control. The fitness-enhancing consequences of long-term contingencies are health, resources, relationships, or reproduction. This view ties rules both to evolutionary theory and to culture. Stating a rule is a cultural practice. The practice strengthens, with short-term reinforcement, behavior that usually enhances fitness in the long run. The practice evolves because of its effect on fitness. The standard definition of a rule as a verbal statement that points to a contingency fails to distinguish between a rule and a bargain (“If you'll do X, then I'll do Y”), which signifies only a single short-term contingency that provides mutual reinforcement for speaker and listener. In contrast, the giving and following of a rule (“Dress warmly; it's cold outside”) can be understood only by reference also to a contingency providing long-term enhancement of the listener's fitness or the fitness of the listener's genes. Such a perspective may change the way both behavior analysts and evolutionary biologists think about rule-governed behavior. ImagesFigure 1 PMID:22478201

Comparison of aortic and carotid baroreflex stimulus-response characteristics in humans

NASA Technical Reports Server (NTRS)

Smith, S. A.; Querry, R. G.; Fadel, P. J.; Weiss, M. W.; Olivencia-Yurvati, A.; Shi, X.; Raven, P. B.

2001-01-01

In order to characterize the stimulus-response relationships of the arterial, aortic, and carotid baroreflexes in mediating cardiac chronotropic function, we measured heart rate (HR) responses elicited by acute changes in mean arterial pressure (MAP) and carotid sinus pressure (CSP) in 11 healthy individuals. Arterial (aortic + carotid) baroreflex control of HR was quantified using ramped changes in MAP induced by bolus injection of phenylephrine (PE) and sodium nitroprusside (SN). To assess aortic-cardiac responses, neck pressure (NP) and suction (NS) were applied during PE and SN administration, respectively, to counter alterations in CSP thereby isolating the aortic baroreflex. Graded levels of NP and NS were delivered to the carotid sinus using a customized neck collar device to assess the carotid-cardiac baroreflex, independent of drug infusion. The operating characteristics of each reflex were determined from the logistic function of the elicited HR response to the induced change in MAP. The arterial pressures at which the threshold was located on the stimulus-response curves determined for the arterial, aortic and carotid baroreflexes were not significantly different (72+/-4, 67+/-3, and 72+/-4 mm Hg, respectively, P > 0.05). Similarly, the MAP at which the saturation of the reflex responses were elicited did not differ among the baroreflex arcs examined (98+/-3, 99+/-2, and 102+/-3 mm Hg, respectively). These data suggest that the baroreceptor populations studied operate over the same range of arterial pressures. This finding indicates each baroreflex functions as both an important anti-hypotensive and anti-hypertensive mechanism. In addition, this investigation describes a model of aortic baroreflex function in normal healthy humans, which may prove useful in identifying the origin of baroreflex dysfunction in disease- and training-induced conditions.

Negative Emotion Does Not Modulate Rapid Feature Integration Effects

PubMed Central

Trübutschek, Darinka; Egner, Tobias

2012-01-01

Emotional arousal at encoding is known to facilitate later memory recall. In the present study, we asked whether this emotion-modulation of episodic memory is also evident at very short time scales, as measured by “feature integration effects,” the moment-by-moment binding of relevant stimulus and response features in episodic memory. This question was motivated by recent findings that negative emotion appears to potentiate first-order trial sequence effects in classic conflict tasks, which has been attributed to emotion-modulation of conflict-driven cognitive control processes. However, these effects could equally well have been carried by emotion-modulation of mnemonic feature binding processes, which were perfectly confounded with putative control processes in these studies. In the present experiments, we tried to shed light on this question by testing explicitly whether feature integration processes, assessed in isolation of conflict–control, are in fact susceptible to negative emotion-modulation. For this purpose, we adopted a standard protocol for assessing the rapid binding of stimulus and response features in episodic memory (Experiment 1) and paired it with the presentation of either neutral or fearful background face stimuli, shown either at encoding only (Experiment 2), or at both encoding and retrieval (Experiment 3). Whereas reliable feature integration effects were observed in all three experiments, no evidence for emotion-modulation of these effects was detected, in spite of significant effects of emotion on response times. These findings suggest that rapid feature integration of foreground stimulus and response features is not subject to modulation by negative emotional background stimuli and further suggest that previous reports of emotion-modulated trial–transition effects are likely attributable to the effects of emotion on cognitive control processes. PMID:22509172

Visual search by chimpanzees (Pan): assessment of controlling relations.

PubMed Central

Tomonaga, M

1995-01-01

Three experimentally sophisticated chimpanzees (Pan), Akira, Chloe, and Ai, were trained on visual search performance using a modified multiple-alternative matching-to-sample task in which a sample stimulus was followed by the search display containing one target identical to the sample and several uniform distractors (i.e., negative comparison stimuli were identical to each other). After they acquired this task, they were tested for transfer of visual search performance to trials in which the sample was not followed by the uniform search display (odd-item search). Akira showed positive transfer of visual search performance to odd-item search even when the display size (the number of stimulus items in the search display) was small, whereas Chloe and Ai showed a transfer only when the display size was large. Chloe and Ai used some nonrelational cues such as perceptual isolation of the target among uniform distractors (so-called pop-out). In addition to the odd-item search test, various types of probe trials were presented to clarify the controlling relations in multiple-alternative matching to sample. Akira showed a decrement of accuracy as a function of the display size when the search display was nonuniform (i.e., each "distractor" stimulus was not the same), whereas Chloe and Ai showed perfect performance. Furthermore, when the sample was identical to the uniform distractors in the search display, Chloe and Ai never selected an odd-item target, but Akira selected it when the display size was large. These results indicated that Akira's behavior was controlled mainly by relational cues of target-distractor oddity, whereas an identity relation between the sample and the target strongly controlled the performance of Chloe and Ai. PMID:7714449

Failure of bacterial screening to detect Staphylococcus aureus: the English experience of donor follow-up.

PubMed

Brailsford, S R; Tossell, J; Morrison, R; McDonald, C P; Pitt, T L

2018-05-24

Between February 2011 and December 2016, over 1·6 million platelet units, 36% pooled platelets, underwent bacterial screening prior to issue. Contamination rates for apheresis and pooled platelets were 0·02% and 0·07%, respectively. Staphylococcus aureus accounted for 21 contaminations, including four pooled platelets, one confirmed transfusion-transmitted infection (TTI) and three 'near-miss' incidents detected on visual inspection which were negative on screening. We describe follow-up investigations of 16 donors for skin carriage of S. aureus and molecular characterisation of donor and pack isolates. Units were screened by the BacT/ALERT 3D detection system. Contributing donors were interviewed and consent requested for skin and nasal swabbing. S. aureus isolates were referred for spa gene type and DNA macrorestriction profile to determine identity between carriage strains and packs. Donors of 10 apheresis and two pooled packs screen positive for S. aureus were confirmed as the source of contamination; seven had a history of skin conditions, predominantly eczema; 11 were nasal carriers. The 'near-miss' incidents were associated with apheresis donors, two donors harboured strains indistinguishable from the pack strain. The TTI was due to a screen-negative pooled unit, and a nasal isolate of one donor was indistinguishable from that in the unit. Staphylococcus aureus contamination is rare but potentially harmful in platelet units. Donor isolates showed almost universal correspondence in molecular type with pack isolates, thus confirming the source of contamination. The importance of visual inspection of packs prior to transfusion is underlined by the 'near-miss' incidents. © 2018 International Society of Blood Transfusion.

First Complete Genome Sequence of Papaya ringspot virus-W Isolated from a Gourd in the United States.

PubMed

Ali, Akhtar

2017-01-12

In the United States, the Papaya ringspot virus was first reported from papaya in Florida in 1949. Here, we determined the first complete genome sequence (10,302 nucleotides) of a Papaya ringspot virus-W isolate, which was collected from a commercial field of gourd in Tulsa, OK. Copyright © 2017 Ali.

Notes from the field: Shigella with decreased susceptibility to azithromycin among men who have sex with men - United States, 2002-2013.

PubMed

Heiman, Katherine E; Karlsson, Maria; Grass, Julian; Howie, Becca; Kirkcaldy, Robert D; Mahon, Barbara; Brooks, John T; Bowen, Anna

2014-02-14

Bacteria of the genus Shigella cause approximately 500,000 illnesses each year in the United States. Diarrhea (sometimes bloody), fever, and stomach cramps typically start 1-2 days after exposure and usually resolve in 5-7 days. For patients with severe disease, bloody diarrhea, or compromised immune systems, antibiotic treatment is recommended, but resistance to traditional first-line antibiotics (e.g., ampicillin and trimethoprim-sulfamethoxazole) is common. For multidrugresistant cases, azithromycin, the most frequently prescribed antibiotic in the United States, is recommended for both children and adults. However, not all Shigellae are susceptible to azithromycin. Nonsusceptible isolates exist but are not usually identified because there are no clinical laboratory guidelines for azithromycin susceptibility testing. However, to monitor susceptibility of Shigellae in the United States, CDC's National Antimicrobial Resistance Monitoring System (NARMS) has, since 2011, routinely measured the azithromycin minimum inhibitory concentration (MIC) for every 20th Shigella isolate submitted from public health laboratories to CDC, as well as outbreak-associated isolates. All known U.S. Shigella isolates with decreased susceptibility to azithromycin (DSA-Shigella), and the illnesses caused by them, are described in this report.

Diminished Baroreflex Control of Forearm Vascular Resistance Following Training

NASA Technical Reports Server (NTRS)

Mack, G. W.; Thompson, C. A.; Doerr, D. F.; Nadel, E. R.; Convertino, V. A.

1991-01-01

The stimulus-response characteristics of cardiopulmonary baroreflex control of forearm vascular resistance (FVR units in mm Hg x min x I00 ml/ml) were studied in 14 volunteers before and after 10 wk of endurance training. We assessed the relationship betaleen reflex stimulus (changes in central venous pressure, CVP) and response (FVR) during unloading of cardiopulmonary baroreceptors with lower body negative pressure (LBNP, 0 to - 2O mm Hg). Changes in CVP during LBNP were estimated from pressure changes in a large peripheral vein in the dependent arm of the subject in the right lateral decubitus position. Maximal oxygen uptake (VO(sub 2max)) and total blood volume increased with endurance training from 37.8 +/- 1.4 ml/min x kg and 63.6 +/- 2.1 ml/kg to 45.3 +/- 1.4 ml/ min x kg and 69.3 +/- 2.8 ml/kg respectively (P less than 0.05). Reflex forearm vasoconstriction occurred in response to a reduction in estimated CVP, and the absolute change in FVR per unit of CVP was reduced from -5.96 +/- 0.79 to -4.06 +/- 0.52 units x mm/ Hg (P less than 0.05) following exercise training but was unchanged from -6.10 to 0.57 to -6.22 +/- 0.94 units x mm/ Hg for the time control group (N = 7). Resting values for FVR were similar before and after exercise training; however, resting estimated CVP was elevated from 9.5 +/- 0.5 mm x Hg before training to 11.3 +/- 0.6 mm x Hg after training. The reduction in sensitivity of the cardiopulmonary baroreflex control of FVR was linearly related to the increase in blood volume (r = 0.65, P less than 0.05). suggesting that diminished cardiopulmonary baroreflex control of FVR in physically fit individuals is related, in part, to a training-induced blood volume expansion.

Stimulus Variables and Interpersonal Attraction: The Stimulus Context.

ERIC Educational Resources Information Center

Griffitt, William

In interpersonal attraction, studies and judgment research evaluation of a stimulus is often a function of the context within which the stimulus appears. The first experiment was designed to examine "contrast effects" (shifts in the rated value of a stimulus away from the contextual values) when all attitudinal information was received from two…

Flight representative positive isolation disconnect

NASA Technical Reports Server (NTRS)

Rosener, A. A.; Jonkoniec, T. G.

1977-01-01

Resolutions were developed for each problem encountered and a tradeoff analysis was performed to select a final configuration for a flight representative PID (Positive Isolation Disconnect) that is reduced in size and comparable in weight and pressure drop to the developmental PID. A 6.35 mm (1/4-inch) line size PID was fabricated and tested. The flight representative PID consists of two coupled disconnect halves, each capable of fluid isolation with essentially zero clearance between them for zero leakage upon disconnect half disengagement. An interlocking foolproofing technique prevents uncoupling of disconnect halves prior to fluid isolation. Future development efforts for the Space Shuttle subsystems that would benefit from the use of the positive isolation disconnect are also recommended. Customary units were utilized for principal measurements and calculations with conversion factors being inserted in equations to convert the results to the international system of units.

Airborne Acoustic Perception by a Jumping Spider.

PubMed

Shamble, Paul S; Menda, Gil; Golden, James R; Nitzany, Eyal I; Walden, Katherine; Beatus, Tsevi; Elias, Damian O; Cohen, Itai; Miles, Ronald N; Hoy, Ronald R

2016-11-07

Jumping spiders (Salticidae) are famous for their visually driven behaviors [1]. Here, however, we present behavioral and neurophysiological evidence that these animals also perceive and respond to airborne acoustic stimuli, even when the distance between the animal and the sound source is relatively large (∼3 m) and with stimulus amplitudes at the position of the spider of ∼65 dB sound pressure level (SPL). Behavioral experiments with the jumping spider Phidippus audax reveal that these animals respond to low-frequency sounds (80 Hz; 65 dB SPL) by freezing-a common anti-predatory behavior characteristic of an acoustic startle response. Neurophysiological recordings from auditory-sensitive neural units in the brains of these jumping spiders showed responses to low-frequency tones (80 Hz at ∼65 dB SPL)-recordings that also represent the first record of acoustically responsive neural units in the jumping spider brain. Responses persisted even when the distances between spider and stimulus source exceeded 3 m and under anechoic conditions. Thus, these spiders appear able to detect airborne sound at distances in the acoustic far-field region, beyond the near-field range often thought to bound acoustic perception in arthropods that lack tympanic ears (e.g., spiders) [2]. Furthermore, direct mechanical stimulation of hairs on the patella of the foreleg was sufficient to generate responses in neural units that also responded to airborne acoustic stimuli-evidence that these hairs likely play a role in the detection of acoustic cues. We suggest that these auditory responses enable the detection of predators and facilitate an acoustic startle response. VIDEO ABSTRACT. Copyright © 2016 Elsevier Ltd. All rights reserved.

Response of semicircular canal dependent units in vestibular nuclei to rotation of a linear acceleration vector without angular acceleration

PubMed Central

Benson, A. J.; Guedry, F. E.; Jones, G. Melvill

1970-01-01

1. Recent experiments have shown that rotation of a linear acceleration vector round the head can generate involuntary ocular nystagmus in the absence of angular acceleration. The present experiments examine the suggestion that adequate stimulation of the semicircular canals may contribute to this response. 2. Decerebrate cats were located in a stereotaxic device on a platform, slung from four parallel cables, which could be driven smoothly round a circular orbit without inducing significant angular movement of the platform. This Parallel Swing Rotation (PSR) generated a centripetal acceleration of 4·4 m/sec2 which rotated round the head at 0·52 rev/sec. 3. The discharge frequency of specifically lateral canal-dependent neural units in the vestibular nuclei of cats was recorded during PSR to right and left, and in the absence of motion. The dynamic responses to purely angular motion were also examined on a servo-driven turntable. 4. Without exception all proven canal-dependent cells examined (twenty-nine cells in nine cats) were more active during PSR in the direction of endolymph circulation assessed to be excitatory to the unit, than during PSR in the opposite direction. 5. The observed changes in discharge frequency are assessed to have been of a magnitude appropriate for the generation of the involuntary oculomotor response induced by the same stimulus in the intact animal. 6. The findings suggest that a linear acceleration vector which rotates in the plane of the lateral semicircular canals can be an adequate stimulus to ampullary receptors, though an explanation which invokes the modulation of canal cells by a signal dependent upon the sequential activation of macular receptors cannot be positively excluded. PMID:5501270

Roles of octopaminergic and dopaminergic neurons in appetitive and aversive memory recall in an insect.

PubMed

Mizunami, Makoto; Unoki, Sae; Mori, Yasuhiro; Hirashima, Daisuke; Hatano, Ai; Matsumoto, Yukihisa

2009-08-04

In insect classical conditioning, octopamine (the invertebrate counterpart of noradrenaline) or dopamine has been suggested to mediate reinforcing properties of appetitive or aversive unconditioned stimulus, respectively. However, the roles of octopaminergic and dopaminergic neurons in memory recall have remained unclear. We studied the roles of octopaminergic and dopaminergic neurons in appetitive and aversive memory recall in olfactory and visual conditioning in crickets. We found that pharmacological blockade of octopamine and dopamine receptors impaired aversive memory recall and appetitive memory recall, respectively, thereby suggesting that activation of octopaminergic and dopaminergic neurons and the resulting release of octopamine and dopamine are needed for appetitive and aversive memory recall, respectively. On the basis of this finding, we propose a new model in which it is assumed that two types of synaptic connections are formed by conditioning and are activated during memory recall, one type being connections from neurons representing conditioned stimulus to neurons inducing conditioned response and the other being connections from neurons representing conditioned stimulus to octopaminergic or dopaminergic neurons representing appetitive or aversive unconditioned stimulus, respectively. The former is called 'stimulus-response connection' and the latter is called 'stimulus-stimulus connection' by theorists studying classical conditioning in higher vertebrates. Our model predicts that pharmacological blockade of octopamine or dopamine receptors during the first stage of second-order conditioning does not impair second-order conditioning, because it impairs the formation of the stimulus-response connection but not the stimulus-stimulus connection. The results of our study with a cross-modal second-order conditioning were in full accordance with this prediction. We suggest that insect classical conditioning involves the formation of two kinds of memory traces, which match to stimulus-stimulus connection and stimulus-response connection. This is the first study to suggest that classical conditioning in insects involves, as does classical conditioning in higher vertebrates, the formation of stimulus-stimulus connection and its activation for memory recall, which are often called cognitive processes.

Prestimulus alpha power predicts fidelity of sensory encoding in perceptual decision making.

PubMed

Lou, Bin; Li, Yun; Philiastides, Marios G; Sajda, Paul

2014-02-15

Pre-stimulus α power has been shown to correlate with the behavioral accuracy of perceptual decisions. In most cases, these correlations have been observed by comparing α power for different behavioral outcomes (e.g. correct vs incorrect trials). In this paper we investigate such covariation within the context of behaviorally-latent fluctuations in task-relevant post-stimulus neural activity. Specially we consider variations of pre-stimulus α power with post-stimulus EEG components in a two alternative forced choice visual discrimination task. EEG components, discriminative of stimulus class, are identified using a linear multivariate classifier and only the variability of the components for correct trials (regardless of stimulus class, and for nominally identical stimuli) are correlated with the corresponding pre-stimulus α power. We find a significant relationship between the mean and variance of the pre-stimulus α power and the variation of the trial-to-trial magnitude of an early post-stimulus EEG component. This relationship is not seen for a later EEG component that is also discriminative of stimulus class and which has been previously linked to the quality of evidence driving the decision process. Our results suggest that early perceptual representations, rather than temporally later neural correlates of the perceptual decision, are modulated by pre-stimulus state. © 2013 Elsevier Inc. All rights reserved.

Prestimulus alpha power predicts fidelity of sensory encoding in perceptual decision making

PubMed Central

Lou, Bin; Li, Yun; Philiastides, Marios G.; Sajda, Paul

2013-01-01

Pre-stimulus α power has been shown to correlate with the behavioral accuracy of perceptual decisions. In most cases, these correlations have been observed by comparing α power for different behavioral outcomes (e.g. correct vs incorrect trials). In this paper we investigate such covariation within the context of behaviorally-latent fluctuations in task-relevant post-stimulus neural activity. Specially we consider variations of pre-stimulus α power with post-stimulus EEG components in a two alternative forced choice visual discrimination task. EEG components, discriminative of stimulus class, are identified using a linear multivariate classifier and only the variability of the components for correct trials (regardless of stimulus class, and for nominally identical stimuli) are correlated with the corresponding pre-stimulus α power. We find a significant relationship between the mean and variance of the pre-stimulus α power and the variation of the trial-to-trial magnitude of an early post-stimulus EEG component. This relationship is not seen for a later EEG component that is also discriminative of stimulus class and which has been previously linked to the quality of evidence driving the decision process. Our results suggest that early perceptual representations, rather than temporally later neural correlates of the perceptual decision, are modulated by pre-stimulus state. PMID:24185020

Stimulus generalization, discrimination learning, and peak shift in horses.

PubMed Central

Dougherty, D M; Lewis, P

1991-01-01

Using horses, we investigated three aspects of the stimulus control of lever-pressing behavior: stimulus generalization, discrimination learning, and peak shift. Nine solid black circles, ranging in size from 0.5 in. to 4.5 in. (1.3 cm to 11.4 cm) served as stimuli. Each horse was shaped, using successive approximations, to press a rat lever with its lip in the presence of a positive stimulus, the 2.5-in. (6.4-cm) circle. Shaping proceeded quickly and was comparable to that of other laboratory organisms. After responding was maintained on a variable-interval 30-s schedule, stimulus generalization gradients were collected from 2 horses prior to discrimination training. During discrimination training, grain followed lever presses in the presence of a positive stimulus (a 2.5-in circle) and never followed lever presses in the presence of a negative stimulus (a 1.5-in. [3.8-cm] circle). Three horses met a criterion of zero responses to the negative stimulus in fewer than 15 sessions. Horses given stimulus generalization testing prior to discrimination training produced symmetrical gradients; horses given discrimination training prior to generalization testing produced asymmetrical gradients. The peak of these gradients shifted away from the negative stimulus. These results are consistent with discrimination, stimulus generalization, and peak-shift phenomena observed in other organisms. PMID:1940765

Stimulus Effects on Local Preference: Stimulus-Response Contingencies, Stimulus-Food Pairing, and Stimulus-Food Correlation

ERIC Educational Resources Information Center

Davison, Michael; Baum, William M.

2010-01-01

Four pigeons were trained in a procedure in which concurrent-schedule food ratios changed unpredictably across seven unsignaled components after 10 food deliveries. Additional green-key stimulus presentations also occurred on the two alternatives, sometimes in the same ratio as the component food ratio, and sometimes in the inverse ratio. In eight…

Distribution of Genes Encoding Putative Transmissibility Factors among Epidemic and Nonepidemic Strains of Burkholderia cepacia from Cystic Fibrosis Patients in the United Kingdom

PubMed Central

Clode, Fiona E.; Kaufmann, Mary E.; Malnick, Henry; Pitt, Tyrone L.

2000-01-01

In the last 15 years, Burkholderia cepacia has emerged as a significant pathogen in cystic fibrosis (CF) patients, mainly due to the severity of infection observed in a subset of patients and the fear of transmission of the organism to noncolonized patients. Although patients who deteriorate rapidly cannot be predicted by microbiological characteristics, three genetic markers have been described for strains that spread between patients. These are the cblA gene, encoding giant cable pili; a hybrid of two insertion sequences, IS1356 and IS402; and a 1.4-kb open reading frame known as the B. cepacia epidemic strain marker (BCESM). The latter two are of unknown function. An epidemic strain lineage was previously identified among CF patients in the United Kingdom that apparently had spread from North America and that was characterized by a specific random amplified polymorphic DNA (RAPD) pattern. We searched for the described genetic markers using specific PCR assays with 117 patient isolates of B. cepacia from 40 United Kingdom hospitals. Isolates were grouped according to genomovar and epidemic strain lineage RAPD pattern with a 10-base primer, P272. A total of 41 isolates from patients in 12 hospitals were classified as the epidemic strain, and 40 of these were distributed in genomovars IIIa (11 isolates), IIIb (1 isolate), and IIIc (28 isolates). All isolates of the epidemic strain were positive for the cblA gene and BCESM, but two lacked the insertion sequence hybrid. None of the 76 sporadic isolates contained cblA or the insertion sequence hybrid, but 11 of them were positive for BCESM. Nonepidemic isolates were distributed among genomovars I or IV (9), II (49), IIIa (11), IIIb (3), and IIIc (4). There were three clusters of cross-infection (one involving two patients and two involving three patients) with isolates of genomovar II. We conclude that in the United Kingdom, a single clonal lineage has spread between and within some hospitals providing care for CF patients. The presence of the cblA gene is the most specific marker for the epidemic strain. We recommend that all isolates of B. cepacia from CF patients should be screened by PCR to influence segregation and infection control strategies. PMID:10790095

Stimulus-response correspondence effect as a function of temporal overlap between relevant and irrelevant information processing.

PubMed

Wang, Dong-Yuan Debbie; Richard, F Dan; Ray, Brittany

2016-01-01

The stimulus-response correspondence (SRC) effect refers to advantages in performance when stimulus and response correspond in dimensions or features, even if the common features are irrelevant to the task. Previous research indicated that the SRC effect depends on the temporal course of stimulus information processing. The current study investigated how the temporal overlap between relevant and irrelevant stimulus processing influences the SRC effect. In this experiment, the irrelevant stimulus (a previously associated tone) preceded the relevant stimulus (a coloured rectangle). The irrelevant and relevant stimuli onset asynchrony was varied to manipulate the temporal overlap between the irrelevant and relevant stimuli processing. Results indicated that the SRC effect size varied as a quadratic function of the temporal overlap between the relevant stimulus and irrelevant stimulus. This finding extends previous experimental observations that the SRC effect size varies in an increasing or decreasing function with reaction time. The current study demonstrated a quadratic function between effect size and the temporal overlap.

Sex differences in audiovisual discrimination learning by Bengalese finches (Lonchura striata var. domestica).

PubMed

Seki, Yoshimasa; Okanoya, Kazuo

2008-02-01

Both visual and auditory information are important for songbirds, especially in developmental and sexual contexts. To investigate bimodal cognition in songbirds, the authors conducted audiovisual discrimination training in Bengalese finches. The authors used two types of stimulus: an "artificial stimulus," which is a combination of simple figures and sound, and a "biological stimulus," consisting of video images of singing males along with their songs. The authors found that while both sexes predominantly used visual cues in the discrimination tasks, males tended to be more dependent on auditory information for the biological stimulus. Female responses were always dependent on the visual stimulus for both stimulus types. Only males changed their discrimination strategy according to stimulus type. Although males used both visual and auditory cues for the biological stimulus, they responded to the artificial stimulus depending only on visual information, as the females did. These findings suggest a sex difference in innate auditory sensitivity. (c) 2008 APA.

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

Sobral, G. A. Jr.; Vieira, V. M.; Lyra, M. L.

Extending a model due to Derrida, Gardner, and Zippelius, we have studied the recognition ability of an extreme and asymmetrically diluted version of the Hopfield model for associative memory by including the effect of a stimulus in the dynamics of the system. We obtain exact results for the dynamic evolution of the average network superposition. The stimulus field was considered as proportional to the overlapping of the state of the system with a particular stimulated pattern. Two situations were analyzed, namely, the external stimulus acting on the initialization pattern (parallel stimulus) and the external stimulus acting on a pattern orthogonalmore » to the initialization one (orthogonal stimulus). In both cases, we obtained the complete phase diagram in the parameter space composed of the stimulus field, thermal noise, and network capacity. Our results show that the system improves its recognition ability for parallel stimulus. For orthogonal stimulus two recognition phases emerge with the system locking at the initialization or stimulated pattern. We confront our analytical results with numerical simulations for the noiseless case T=0.« less

Threshold units: A correct metric for reaction time?

PubMed Central

Zele, Andrew J.; Cao, Dingcai; Pokorny, Joel

2007-01-01

Purpose To compare reaction time (RT) to rod incremental and decremental stimuli expressed in physical contrast units or psychophysical threshold units. Methods Rod contrast detection thresholds and suprathreshold RTs were measured for Rapid-On and Rapid-Off ramp stimuli. Results Threshold sensitivity to Rapid-Off stimuli was higher than to Rapid-On stimuli. Suprathreshold RTs specified in Weber contrast for Rapid-Off stimuli were shorter than for Rapid-On stimuli. Reaction time data expressed in multiples of threshold reversed the outcomes: Reaction times for Rapid-On stimuli were shorter than those for Rapid-Off stimuli. The use of alternative contrast metrics also failed to equate RTs. Conclusions A case is made that the interpretation of RT data may be confounded when expressed in threshold units. Stimulus energy or contrast is the only metric common to the response characteristics of the cells underlying speeded responses. The use of threshold metrics for RT can confuse the interpretation of an underlying physiological process. PMID:17240416

Response of cat cerebellar vermis induced by sound. II. The role of the mossy and climbing fibers in acoustic transmission to the cerebellar cortex and influence of stimuli parameters.

PubMed

Jastreboff, P J; Tarnecki, R

1975-01-01

Experiments were performed on cats under Chloralose or Nembutal anesthesia. The parameters of the acoustic click stimuli were found to have a strong influence on the responses registered from both the surface of the cerebellar vermis lobuli V up VII as well as from single units. It was shown that a stimulus frequency rate not greater than 1/2 s should be used, since higher frequencies caused strong attenuation of the response. The type of anesthesia did not change the latencies of reactions of both evoked potentials and single units. However, decreasing the strength of the click resulted in increased response latencies, in the case of single unit reactions. A very strong influence of weak visual stimuli on units was also observed. It is suggested that mossy fibers are the most important fibers in the transmission of acoustic information to the cerebellar cortex.

Whole Genome Shotgun Analysis: the Resolving Power to Distinguish 2009 and 2010 Clinical Isolates of Salmonella Typhimurium Possessing the Same PFGE Type

USDA-ARS?s Scientific Manuscript database

Between 2009 and 2011, Salmonella enterica subsp. enterica serovar Typhimurium with the JPXX01.0014 pulse field gel electrophoresis (PFGE) type was isolated across the United States. The 2009 isolates were associated with an outbreak from an unidentified food source, while later isolates were linked...

A Consistent Wave Impact Load Model for Studying Structure, Equipment Ruggedness, Shock Isolation Seats, and Human Comfort in Small High Speed Craft

DTIC Science & Technology

2016-11-01

acceleration at a cross-section was used as a measure of the wave impact load in units of g. Later developments included publication of the envelope...Republic, 4 – 7 October 2004. PICKFORD, E.V., MAHONE, R.R., WOLK, H.L. (1975). Slam/Shock Isolation Pedestal, United States Patent Number, 3,912,248, 14...accelerations. The rigid body peak acceleration is a measure of the impact load in units of g. In the following plots the data corresponds to head-sea

Continuous- and discrete-time stimulus sequences for high stimulus rate paradigm in evoked potential studies.

PubMed

Wang, Tao; Huang, Jiang-hua; Lin, Lin; Zhan, Chang'an A

2013-01-01

To obtain reliable transient auditory evoked potentials (AEPs) from EEGs recorded using high stimulus rate (HSR) paradigm, it is critical to design the stimulus sequences of appropriate frequency properties. Traditionally, the individual stimulus events in a stimulus sequence occur only at discrete time points dependent on the sampling frequency of the recording system and the duration of stimulus sequence. This dependency likely causes the implementation of suboptimal stimulus sequences, sacrificing the reliability of resulting AEPs. In this paper, we explicate the use of continuous-time stimulus sequence for HSR paradigm, which is independent of the discrete electroencephalogram (EEG) recording system. We employ simulation studies to examine the applicability of the continuous-time stimulus sequences and the impacts of sampling frequency on AEPs in traditional studies using discrete-time design. Results from these studies show that the continuous-time sequences can offer better frequency properties and improve the reliability of recovered AEPs. Furthermore, we find that the errors in the recovered AEPs depend critically on the sampling frequencies of experimental systems, and their relationship can be fitted using a reciprocal function. As such, our study contributes to the literature by demonstrating the applicability and advantages of continuous-time stimulus sequences for HSR paradigm and by revealing the relationship between the reliability of AEPs and sampling frequencies of the experimental systems when discrete-time stimulus sequences are used in traditional manner for the HSR paradigm.

Visual awareness suppression by pre-stimulus brain stimulation; a neural effect.

PubMed

Jacobs, Christianne; Goebel, Rainer; Sack, Alexander T

2012-01-02

Transcranial magnetic stimulation (TMS) has established the functional relevance of early visual cortex (EVC) for visual awareness with great temporal specificity non-invasively in conscious human volunteers. Many studies have found a suppressive effect when TMS was applied over EVC 80-100 ms after the onset of the visual stimulus (post-stimulus TMS time window). Yet, few studies found task performance to also suffer when TMS was applied even before visual stimulus presentation (pre-stimulus TMS time window). This pre-stimulus TMS effect, however, remains controversially debated and its origin had mainly been ascribed to TMS-induced eye-blinking artifacts. Here, we applied chronometric TMS over EVC during the execution of a visual discrimination task, covering an exhaustive range of visual stimulus-locked TMS time windows ranging from -80 pre-stimulus to 300 ms post-stimulus onset. Electrooculographical (EoG) recordings, sham TMS stimulation, and vertex TMS stimulation controlled for different types of non-neural TMS effects. Our findings clearly reveal TMS-induced masking effects for both pre- and post-stimulus time windows, and for both objective visual discrimination performance and subjective visibility. Importantly, all effects proved to be still present after post hoc removal of eye blink trials, suggesting a neural origin for the pre-stimulus TMS suppression effect on visual awareness. We speculate based on our data that TMS exerts its pre-stimulus effect via generation of a neural state which interacts with subsequent visual input. Copyright © 2011 Elsevier Inc. All rights reserved.

Xylella fastidiosa Isolates from Both subsp. multiplex and fastidiosa Cause Disease on Southern Highbush Blueberry (Vaccinium sp.) Under Greenhouse Conditions.

PubMed

Oliver, J E; Cobine, P A; De La Fuente, L

2015-07-01

Xylella fastidiosa is a xylem-limited gram-negative plant pathogen that affects numerous crop species, including grape, citrus, peach, pecan, and almond. Recently, X. fastidiosa has also been found to be the cause of bacterial leaf scorch on blueberry in the southeastern United States. Thus far, all X. fastidiosa isolates obtained from infected blueberry have been classified as X. fastidiosa subsp. multiplex; however, X. fastidiosa subsp. fastidiosa isolates are also present in the southeastern United States and commonly cause Pierce's disease of grapevines. In this study, seven southeastern U.S. isolates of X. fastidiosa, including three X. fastidiosa subsp. fastidiosa isolates from grape, one X. fastidiosa subsp. fastidiosa isolate from elderberry, and three X. fastidiosa subsp. multiplex isolates from blueberry, were used to infect the southern highbush blueberry 'Rebel'. Following inoculation, all isolates colonized blueberry, and isolates from both X. fastidiosa subsp. multiplex and X. fastidiosa subsp. fastidiosa caused symptoms, including characteristic stem yellowing and leaf scorch symptoms as well as dieback of the stem tips. Two X. fastidiosa subsp. multiplex isolates from blueberry caused more severe symptoms than the other isolates examined, and infection with these two isolates also had a significant impact on host mineral nutrient content in sap and leaves. These findings have potential implications for understanding X. fastidiosa host adaptation and expansion and the development of emerging diseases caused by this bacterium.

United States Air Force High School Apprenticeship Program: 1989 Program Management Report. Volume 3

DTIC Science & Technology

1988-12-01

orrtent of visual or auditory stimulus exposed to the eyes o- oays -t a level below normal threshold, it is possible to perceive the subliminal stimuli...usually to small or vague to be consciously recognized, but they are declared to influence the 87-6 viewer’s subconsc’ious sex drive. Stimulation below...programs the mechanisms to stimulate career interests in science and technology in high school students showing promise in these areas. The Air Force High

Genealogy of the "grandmother cell".

PubMed

Gross, Charles G

2002-10-01

A "grandmother cell" is a hypothetical neuron that responds only to a highly complex, specific, and meaningful stimulus, such as the image of one's grandmother. The term originated in a parable Jerry Lettvin told in 1967. A similar concept had been systematically developed a few years earlier by Jerzy Konorski who called such cells "gnostic" units. This essay discusses the origin, influence, and current status of these terms and of the alternative view that complex stimuli are represented by the pattern of firing across ensembles of neurons.

A crown ether appended super gelator with multiple stimulus responsiveness.

PubMed

Dong, Shengyi; Zheng, Bo; Xu, Donghua; Yan, Xuzhou; Zhang, Mingming; Huang, Feihe

2012-06-26

A crown ether appended super gelator is designed and synthesized. It can gel a variety of organic solvents and shows excellent gelation properties with both low critical gelation concentration and short gelation time. Due to the introduction of the crown ether moiety and a secondary ammonium unit, the supramolecular gels show reversible gel-sol transitions. The supramolecular gels can also be molded into shape-persistent and free-standing objects. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Comparative analysis of Edwardsiella tarda isolates from fish in the eastern United States suggests the existence of two genetically distinct species, Edwardsiella tarda and Edwardsiella pseudotarda sp. nov

USDA-ARS?s Scientific Manuscript database

Edwardsiella tarda, a Gram-negative member of the family Enterobacteriaceae, is often implicated in significant losses in aquaculture facilities worldwide. Here, we assessed the intra-specific variability of a collection of E. tarda isolates from 4 different fish species in the eastern United State...

An Evaluation of the Number of Presentations of Target Sounds during Stimulus-Stimulus Pairing Trials

ERIC Educational Resources Information Center

Miliotis, Adriane; Sidener, Tina M.; Reeve, Kenneth F.; Carbone, Vincent; Sidener, David W.; Rader, Lisa; Delmolino, Lara

2012-01-01

Stimulus-stimulus pairing (SSP) of vocalizations pairs the speech of others with the delivery of highly preferred items. The goal of this procedure is to produce a temporary increase in vocalizations, thus creating a larger variety of sounds that can subsequently be brought under appropriate stimulus control (Esch, Carr, & Grow, 2009). In this…

Duration of the Unconditioned Stimulus in Appetitive Conditioning of Honeybees Differentially Impacts Learning, Long-Term Memory Strength, and the Underlying Protein Synthesis

ERIC Educational Resources Information Center

Marter, Kathrin; Grauel, M. Katharina; Lewa, Carmen; Morgenstern, Laura; Buckemüller, Christina; Heufelder, Karin; Ganz, Marion; Eisenhardt, Dorothea

2014-01-01

This study examines the role of stimulus duration in learning and memory formation of honeybees ("Apis mellifera"). In classical appetitive conditioning honeybees learn the association between an initially neutral, conditioned stimulus (CS) and the occurrence of a meaningful stimulus, the unconditioned stimulus (US). Thereby the CS…

Genomic Analysis of a Pan-Resistant Isolate of Klebsiella pneumoniae, United States 2016.

PubMed

de Man, Tom J B; Lutgring, Joseph D; Lonsway, David R; Anderson, Karen F; Kiehlbauch, Julia A; Chen, Lei; Walters, Maroya Spalding; Sjölund-Karlsson, Maria; Rasheed, J Kamile; Kallen, Alexander; Halpin, Alison Laufer

2018-04-03

Antimicrobial resistance is a threat to public health globally and leads to an estimated 23,000 deaths annually in the United States alone. Here, we report the genomic characterization of an unusual Klebsiella pneumoniae , nonsusceptible to all 26 antibiotics tested, that was isolated from a U.S. The isolate harbored four known beta-lactamase genes, including plasmid-mediated bla NDM-1 and bla CMY-6 , as well as chromosomal bla CTX-M-15 and bla SHV-28 , which accounted for resistance to all beta-lactams tested. In addition, sequence analysis identified mechanisms that could explain all other reported nonsusceptibility results, including nonsusceptibility to colistin, tigecycline, and chloramphenicol. Two plasmids, IncA/C2 and IncFIB, were closely related to mobile elements described previously and isolated from Gram-negative bacteria from China, Nepal, India, the United States, and Kenya, suggesting possible origins of the isolate and plasmids. This is one of the first K. pneumoniae isolates in the United States to have been reported to the Centers for Disease Control and Prevention (CDC) as nonsusceptible to all drugs tested, including all beta-lactams, colistin, and tigecycline. IMPORTANCE Antimicrobial resistance is a major public health threat worldwide. Bacteria that are nonsusceptible or resistant to all antimicrobials available are of major concern to patients and the public because of lack of treatment options and potential for spread. A Klebsiella pneumoniae strain that was nonsusceptible to all tested antibiotics was isolated from a U.S. Mechanisms that could explain all observed phenotypic antimicrobial resistance phenotypes, including resistance to colistin and beta-lactams, were identified through whole-genome sequencing. The large variety of resistance determinants identified demonstrates the usefulness of whole-genome sequencing for detecting these genes in an outbreak response. Sequencing of isolates with rare and unusual phenotypes can provide information on how these extremely resistant isolates develop, including whether resistance is acquired on mobile elements or accumulated through chromosomal mutations. Moreover, this provides further insight into not only detecting these highly resistant organisms but also preventing their spread.

Rational-emotive behavior therapy and the formation of stimulus equivalence classes.

PubMed

Plaud, J J; Gaither, G A; Weller, L A; Bigwood, S J; Barth, J; von Duvillard, S P

1998-08-01

Stimulus equivalence is a behavioral approach to analyzing the "meaning" of stimulus sets and has an implication for clinical psychology. The formation of three-member (A --> B --> C) stimulus equivalence classes was used to investigate the effects of three different sets of sample and comparison stimuli on emergent behavior. The three stimulus sets were composed of Rational-Emotive Behavior Therapy (REBT)-related words, non-REBT emotionally charged words, and a third category of neutral words composed of flower labels. Sixty-two women and men participated in a modified matching-to-sample experiment. Using a mixed cross-over design, and controlling for serial order effects, participants received conditional training and emergent relationship training in the three stimulus set conditions. Results revealed a significant interaction between the formation of stimulus equivalence classes and stimulus meaning, indicating consistently biased responding in favor of reaching criterion responding more slowly for REBT-related and non-REBT emotionally charged words. Results were examined in the context of an analysis of the importance of stimulus meaning on behavior and the relation of stimulus meaning to behavioral and cognitive theories, with special appraisal given to the influence of fear-related discriminative stimuli on behavior.

[Analysis of electrically evoked response (EER) in relation to the central visual pathway of the cat (1). Wave shape of the cat EER].

PubMed

Fukatsu, Y; Miyake, Y; Sugita, S; Saito, A; Watanabe, S

1990-11-01

To analyze the Electrically evoked response (EER) in relation to the central visual pathway, the authors studied the properties of wave patterns and peak latencies of EER in 35 anesthetized adult cats. The cat EER showed two early positive waves on outward current (cornea cathode) stimulus and three or four early positive waves on inward current (cornea anode) stimulus. These waves were recorded within 50 ms after stimulus onset, and were the most consistent components in cat EER. The stimulus threshold for EER showed a less individual variation than amplitude. The difference of stimulus threshold between outward and inward current stimulus was also essentially negligible. The stimulus threshold was higher in early components than in late components. The peak latency of EER became shorter and the amplitude became higher, as the stimulus intensity was increased. However, this tendency was reversed and some wavelets started to appear when the stimulus was extremely strong. The recording using short stimulus duration and bipolar electrodes enabled us to reduce the electrical artifact of EER. These results obtained from cats were compared with those of humans and rabbits.

Patterns of multi-drug resistant bacteria at first culture from patients admitted to a third level University hospital in Calabria from 2011 to 2014: implications for empirical therapy and infection control.

PubMed

Reale, Mariaconcetta; Strazzulla, Alessio; Quirino, Angela; Rizzo, Claudia; Marano, Vito; Postorino, Maria Concetta; Mazzitelli, Maria; Greco, Giuseppe; Pisani, Vincenzo; Costa, Chiara; Cesana, Bruno Mario; Liberto, Maria Carla; Torti, Carlo; Focà, Alfredo

2017-06-01

Surveillance of antimicrobial drug resistance is fundamental to guide empirical treatment. However, the European Antimicrobial Resistance Surveillance Network provides a general picture, which might not be applicable to clinical settings that are excluded from this survey. We evaluated resistance patterns of ESKAPE isolates over a four-year period in a third level University hospital in the province of Catanzaro (Southern Italy). In this retrospective study, we evaluated the frequency of ESKAPE isolates with different resistance patterns (group 1=low-resistant bacteria; group 2=multi-drug and extremely drug-resistant bacteria; group 3=pan-resistant bacteria), stratified by year (2011, 2012, 2013 and 2014), hospital units (intensive care units, medical and surgical units) and by sample type (urine, blood, wound swabs, respiratory samples, other samples). Chi square test was applied to find differences between isolates with different resistance patterns by hospital unit and by organs and systems. Cochran-Armitage trend test was applied to assess the trend in resistance patterns during the four years analyzed. Amongst 2385 isolates, Escherichia coli (38%) was the most frequent, followed by Pseudomonas aeruginosa (15%), Klebsiella pneumoniae (14%), Staphylococcus aureus (13%), Acinetobacter baumannii (9%), Enterococcus faecalis (8%) and Enterococcus faecium (3%). From 2011 to 2014, frequency of isolates in group 2 plus 3 decreased from 23% to 14% (chi square=55.093; p<0.0001), particularly for E. coli and K. pneumoniae, but the trend increased for S. aureus (from 5% in 2011 to 10% in 2014), and remained stable for the other species. Frequency of isolates in group 2 plus 3 was higher in intensive care units for K. pneumoniae (chi square =32.292; p<0.0001), A. baumannii (chi square =6.947; p<0.0001) and S. aureus (chi square =22.079; p<0.0001). It was also higher from blood than from different sources for most species.

One-year surveillance of ESKAPE pathogens in an intensive care unit of Monterrey, Mexico.

PubMed

Llaca-Díaz, Jorge Martín; Mendoza-Olazarán, Soraya; Camacho-Ortiz, Adrian; Flores, Samantha; Garza-González, Elvira

2012-01-01

Bacterial species from the ESKAPE group (i.e. Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter species) are frequently resistant to antibiotics. The purpose of this study was to monitor the incidence of ESKAPE pathogens at the intensive care unit (ICU) of a tertiary care hospital in Monterrey, Mexico. All clinically relevant organisms isolated from June 2011 to June 2012 were included. Identification and susceptibility testing was performed using panels from Sensititre. Resistance to oxacillin, for S. aureus, and the production of extended spectrum β-lactamases (ESBLs), for K. pneumonia, were determined as defined by the Clinical Laboratory Standards Institute. Also, the presence of vanA and vanB genes was determined in E. faecium vancomycin (VAN)-resistant isolates. The majority of pathogens (64.5%) isolated in the ICU unit were from the ESKAPE group. The organisms most frequently isolated were A. baumannii (15.8%) and P. aeruginosa (14.3%). A high resistance to carbapenems was detected for A. baumannii (75.3%) while 62% of S. aureus isolates were confirmed to be methicillin resistant. Of the K. pneumoniae isolates, 36.9% were ESBL producers. We detected three E. faecium VAN-resistant isolates, all of which contained the vanA gene. The presence of the ESKAPE group of pathogens is a major problem in the ICU setting. The results of this study support the implementation of special antimicrobial strategies to specifically target these microorganisms. Copyright © 2013 S. Karger AG, Basel.

Extrafoveally applied flashing light affects contrast thresholds of achromatic and S-cone isolating, but not L-M cone modulated stimuli.

PubMed

Őze, A; Puszta, A; Buzás, P; Kóbor, P; Braunitzer, G; Nagy, A

2018-06-21

Flashing light stimulation is often used to investigate the visual system. However, the magnitude of the effect of this stimulus on the various subcortical pathways is not well investigated. The signals of conscious vision are conveyed by the magnocellular, parvocellular and koniocellular pathways. Parvocellular and koniocellular pathways (or more precisely, the L-M opponent and S-cone isolating channels) can be accessed by isoluminant red-green (L-M) and S-cone isolating stimuli, respectively. The main goal of the present study was to explore how costimulation with strong white extrafoveal light flashes alters the perception of stimuli specific to these pathways. Eleven healthy volunteers with negative neurological and ophthalmological history were enrolled for the study. Isoluminance of L-M and S-cone isolating sine-wave gratings was set individually, using the minimum motion procedure. The contrast thresholds for these stimuli as well as for achromatic gratings were determined by an adaptive staircase procedure where subjects had to indicate the orientation (horizontal, oblique or vertical) of the gratings. Thresholds were then determined again while a strong white peripheral light flash was presented 50 ms before each trial. Peripheral light flashes significantly (p < 0.05) increased the contrast thresholds of the achromatic and S-cone isolating stimuli. The threshold elevation was especially marked in case of the achromatic stimuli. However, the contrast threshold for the L-M stimuli was not significantly influenced by the light flashes. We conclude that extrafoveally applied light flashes influence predominantly the perception of achromatic stimuli. Copyright © 2018 Elsevier B.V. All rights reserved.

Multidrug-resistant Strains of Salmonella enterica Typhimurium, United States, 1997–19981

PubMed Central

Whichard, Jean; Rossiter, Shannon; Holland, Ben; Stamey, Karen; Headrick, Marcia L.; Barrett, Timothy J.; Angulo, Frederick J.

2004-01-01

To evaluate multidrug-resistant strains of Salmonella enterica Typhimurium, including definitive type 104 (DT104) in the United States, we reviewed data from the National Antimicrobial Resistance Monitoring System (NARMS). In 1997–1998, 25% (703) of 2,767 serotyped Salmonella isolates received at NARMS were S. Typhimurium; antimicrobial susceptibility testing and phage typing were completed for 697. Fifty-eight percent (402) were resistant to >1 antimicrobial agent. Three multidrug-resistant (>5 drugs) strains accounted for 74% (296) of all resistant isolates. Ceftriaxone resistance was present in 3% (8), and nalidixic acid resistance in 1% (4), of these multidrug-resistant strains. By phage typing, 37% (259) of S. Typhimurium isolates were DT104, 30% (209) were of undefined type and 15% (103) were untypable. Fifty percent (202) of resistant (>1 drug) isolates were DT104. Multidrug-resistant S. Typhimurium isolates, particularly DT104, account for a substantial proportion of S. Typhimurium isolates; ceftriaxone resistance is exhibited by some of these strains. PMID:15200811

Multidrug-resistant strains of Salmonella enterica Typhimurium, United States, 1997-1998.

PubMed

Rabatsky-Ehr, Therese; Whichard, Jean; Rossiter, Shannon; Holland, Ben; Stamey, Karen; Headrick, Marcia L; Barrett, Timothy J; Angulo, Frederick J

2004-05-01

To evaluate multidrug-resistant strains of Salmonella enterica serotype Typhimurium, including definitive type 104 (DT104) in the United States, we reviewed data from the National Antimicrobial Resistance Monitoring System (NARMS). In 1997 to 1998, 703 (25%) of 2,767 serotyped Salmonella isolates received at NARMS were S. Typhimurium; antimicrobial susceptibility testing and phage typing were completed for 697. Fifty-eight percent (402) were resistant to > or = 1 antimicrobial agent. Three multidrug-resistant (> or = 5 drugs) strains accounted for (74%) 296 of all resistant isolates. Ceftriaxone resistance was present in 8 (3%), and nalidixic acid resistance in 4 (1%), of these multidrug-resistant strains. By phage typing, 259 (37%) of S. Typhimurium isolates were DT104, 209 (30%) were of undefined type and 103 (15%) were untypable. Fifty percent (202) of resistant (> or = 1 drug) isolates were DT104. Multidrug-resistant S. Typhimurium isolates, particularly DT104, account for a substantial proportion of S. Typhimurium isolates; ceftriaxone resistance is exhibited by some of these strains.

Taxonomic and Biological Characterization of Steinernema rarum Found in the Southeastern United States

PubMed Central

Nguyen, Khuong B.; Shapiro-Ilan, David I.; Fuxa, James R.; Wood, Bruce W.; Bertolotti, Maria A.; Adams, Byron J.

2006-01-01

Two Steinernema isolates found in Louisiana and Mississippi were later identified as isolates of S. rarum. DNA sequences of ITS regions of the United States isolates are identical with sequences of Argentinean S. rarum strains Samiento and Noetinger and differ by two bases from the Arroyo Cabral isolate from Córdoba, Argentina. SEM observations revealed several new structures in the isolates from the US: female face views have a hexagonal-star perioral disc and eye-shaped lips; some females do not have cephalic papillae; lateral fields of infective juveniles are variable; there are two openings observed close to the posterior edge of the cloaca. Virulence of the US isolates to Anthonomus grandis, Diaprepes abbreviatus, Solenopsis invicta, Coptotermes formosanus, Agrotis ipsilon, Spodoptera frugiperda, and Trichoplusia ni and reproductive potential were evaluated in comparison with other heterorhabditid and steinernematid nematodes. Results such as particularly high virulence to S. frugiperda indicate that the biocontrol potential of the new S. rarum strains merits further study. PMID:19259427

Roles of neuronal NK1 and NK3 receptors in synaptic transmission during motility reflexes in the guinea-pig ileum

PubMed Central

Johnson, P J; Bornstein, J C; Burcher, E

1998-01-01

The role of NK1 and NK3 receptors in synaptic transmission between myenteric neurons during motility reflexes in the guinea-pig ileum was investigated by recording intracellularly the reflex responses of the circular muscle to distension or compression of the mucosal villi. Experiments were performed in a three-chambered organ bath that enabled drugs to be selectively applied to different sites along the reflex pathways.When applied in the recording chamber, an NK1 receptor antagonist, SR140333 (100 nM), reduced by 40–50% the amplitudes of inhibitory junction potentials (i.j.ps) evoked in the circular muscle by activation of descending reflex pathways. This effect was abolished when synaptic transmission in the stimulus region was blocked with physiological saline containing 0.1 mM Ca2+ plus 10 mM Mg2+, leaving only the component of the descending reflex pathway conducted via long anally directed collaterals of intrinsic sensory neurons.SR140333 (100 nM) had no effect on descending reflex i.j.ps when applied to the stimulus region. Ascending reflexes were also unaffected by SR140333 in the stimulus region or between the stimulus and recording sites.Septide (10 nM), an NK1 receptor agonist, enhanced descending reflexes by 30–60% when in the recording chamber. [Sar9,Met(O2)11]substance P had no effect at 10 nM, but potentiated distension-evoked reflexes at 100 nM.A selective NK3 receptor antagonist, SR142801 (100 nM), when applied to the stimulus region, reduced the amplitude of descending reflex responses to compression by 40%, but had no effect on responses to distension. SR142801 (100 nM) had no effect when applied to other regions of the descending reflex pathways.SR142801 (100 nM) only inhibited ascending reflexes when applied at the recording site. However, after nicotinic transmission in the stimulus region was blocked, SR142801 (100 nM) at this site reduced responses to compression.Contractions of the circular muscle of isolated rings of ileum evoked by low concentrations of septide, but not [Sar9,Met(O2)11]substance P, were potentiated by tetrodotoxin (300 nM).Contractile responses evoked by an NK3 receptor agonist, senktide, were non-competitively inhibited by SR142801. After excitatory neuromuscular transmission was blocked, senktide produced inhibitory responses that were also antagonised by SR142801, but to a lesser extent and in an apparently competitive manner.These results indicate that tachykinins acting via NK1 receptors partly mediate transmission to inhibitory motor neurons. NK3 receptors play a role in transmission from intrinsic sensory neurons and from ascending interneurons to excitatory motor neurons during motility reflexes. PMID:9723948

A Novel Unit Cell for Active Switches in the Millimeter-Wave Frequency Range

NASA Astrophysics Data System (ADS)

Müller, Daniel; Scherer, Gunnar; Lewark, Ulrich J.; Massler, Hermann; Wagner, Sandrine; Tessmann, Axel; Leuther, Arnulf; Zwick, Thomas; Kallfass, Ingmar

2018-02-01

This paper presents a novel transistor unit cell which is intended to realize compact active switches in the high millimeter-wave frequency range. The unit cell consists of the combination of shunt and common gate transistor within a four-finger transistor cell, achieving gain in the amplifying state as well as good isolation in the isolating state. Gate width-dependent characteristics of the unit cell as well as the design of actual switch implementations are discussed in detail. To verify the concept, two switches, a single pole double throw (SPDT) switch and single pole quadruple throw (SP4T) switch, intended for the WR3 frequency range (220-325 GHz) were manufactured and characterized. The measured gain at 250 GHz is 4.6 and 2.2 dB for the SPDT and SP4T switch, respectively. An isolation of more than 24 dB for the SPDT switch and 12.8 dB for the SP4T switch was achieved.

Deciphering the contribution of intrinsic and synaptic currents to the effects of transient synaptic inputs on human motor unit discharge

PubMed Central

Powers, Randall K.; Türker, Kemal S.

2010-01-01

The amplitude and time course of synaptic potentials in human motoneurons can be estimated in tonically discharging motor units by measuring stimulus-evoked changes in the rate and probability of motor unit action potentials. However, in spite of the fact that some of these techniques have been used for over thirty years, there is still no consensus on the best way to estimate the characteristics of synaptic potentials or on the accuracy of these estimates. In this review, we compare different techniques for estimating synaptic potentials from human motor unit discharge and also discuss relevant animal models in which estimated synaptic potentials can be compared to those directly measured from intracellular recordings. We also review the experimental evidence on how synaptic noise and intrinsic motoneuron properties influence their responses to synaptic inputs. Finally, we consider to what extent recordings of single motor unit discharge in humans can be used to distinguish the contribution of changes in synaptic inputs versus changes in intrinsic motoneuron properties to altered motoneuron responses following CNS injury. PMID:20427230

The neural circuits of innate fear: detection, integration, action, and memorization

PubMed Central

Silva, Bianca A.; Gross, Cornelius T.

2016-01-01

How fear is represented in the brain has generated a lot of research attention, not only because fear increases the chances for survival when appropriately expressed but also because it can lead to anxiety and stress-related disorders when inadequately processed. In this review, we summarize recent progress in the understanding of the neural circuits processing innate fear in rodents. We propose that these circuits are contained within three main functional units in the brain: a detection unit, responsible for gathering sensory information signaling the presence of a threat; an integration unit, responsible for incorporating the various sensory information and recruiting downstream effectors; and an output unit, in charge of initiating appropriate bodily and behavioral responses to the threatful stimulus. In parallel, the experience of innate fear also instructs a learning process leading to the memorization of the fearful event. Interestingly, while the detection, integration, and output units processing acute fear responses to different threats tend to be harbored in distinct brain circuits, memory encoding of these threats seems to rely on a shared learning system. PMID:27634145

Phenotypic and Genotypic Characterization of Enterobacteriaceae Producing Oxacillinase-48–Like Carbapenemases, United States

PubMed Central

Zhu, Wenming; de Man, Tom J.B.; Avillan, Johannetsy J.; Anderson, Karen F.; Lonsway, David R.; Rowe, Lori A.; Batra, Dhwani; Rasheed, J. Kamile; Limbago, Brandi M.

2018-01-01

Oxacillinase (OXA)–48–like carbapenemases remain relatively uncommon in the United States. We performed phenotypic and genotypic characterization of 30 Enterobacteriaceae producing OXA-48–like carbapenemases that were recovered from patients during 2010–2014. Isolates were collected from 12 states and not associated with outbreaks, although we could not exclude limited local transmission. The alleles β-lactamase OXA-181 (blaOXA-181) (43%), blaOXA-232 (33%), and blaOXA-48 (23%) were found. All isolates were resistant to ertapenem and showed positive results for the ertapenem and meropenem modified Hodge test and the modified carbapenem inactivation method; 73% showed a positive result for the Carba Nordmann–Poirel test. Whole-genome sequencing identified extended-spectrum β-lactamase genes in 93% of isolates. In all blaOXA-232 isolates, the gene was on a ColKP3 plasmid. A total of 12 of 13 isolates harboring blaOXA-181 contained the insertion sequence ΔISEcp1. In all isolates with blaOXA-48, the gene was located on a TN1999 transposon; these isolates also carried IncL/M plasmids. PMID:29553324

Spatial parameters at the basis of social transfer of learning.

PubMed

Lugli, Luisa; Iani, Cristina; Milanese, Nadia; Sebanz, Natalie; Rubichi, Sandro

2015-06-01

Recent research indicates that practicing on a joint spatial compatibility task with an incompatible stimulus-response mapping affects subsequent joint Simon task performance, eliminating the social Simon effect. It has been well established that in individual contexts, for transfer of learning to occur, participants need to practice an incompatible association between stimulus and response positions. The mechanisms underlying transfer of learning in joint task performance are, however, less well understood. The present study was aimed at assessing the relative contribution of 3 different spatial relations characterizing the joint practice context: stimulus-response, stimulus-participant, and participant-response relations. In 3 experiments, the authors manipulated the stimulus-response, stimulus-participant, and response-participant associations. We found that learning from the practice task did not transfer to the subsequent task when during practice stimulus-response associations were spatially incompatible and stimulus-participant associations were compatible (Experiment 1). However, a transfer of learning was evident when stimulus-participant associations were spatially incompatible. This occurred both when response-participant associations were incompatible (Experiment 2) and when they were compatible (Experiment 3). These results seem to support an agent corepresentation account of correspondence effects emerging in joint settings since they suggest that, in social contexts, critical to obtain transfer-of-learning effects is the spatial relation between stimulus and participant positions while the spatial relation between stimulus and response positions is irrelevant. (c) 2015 APA, all rights reserved).

Mycobacterium chimaera colonisation of heater–cooler units (HCU) in Western Australia, 2015: investigation of possible iatrogenic infection using whole genome sequencing

PubMed Central

Robinson, James Owen; Coombs, Geoffrey Wallace; Speers, David John; Keehner, Terillee; Keil, Anthony David; D’Abrera, Victoria; Boan, Peter; Pang, Stanley

2016-01-01

Following the reported link between heater–cooler unit (HCU) colonisation with Mycobacterium chimaera and endocarditis, mycobacterial sampling of all HCUs in use in Western Australia was initiated from August 2015, revealing M. chimaera colonisation in 10 of 15 HCUs. After M. chimaera was isolated from a pleural biopsy from a cardiothoracic patient who may have been exposed to a colonised HCU, a whole genome sequencing investigation was performed involving 65 specimens from 15 HCUs across five hospitals to assess if this infection was related to the HCU. Genetic relatedness was found between the 10 HCU M. chimaera isolates from four hospitals. However the M. chimaera isolate from the cardiothoracic patient was not genetically related to the HCU M. chimaera isolates from that hospital, nor to the other HCU isolates, indicating that the HCUs were not the source of the infection in this patient. PMID:27918263

Internal state of monkey primary visual cortex (V1) predicts figure-ground perception.

PubMed

Supèr, Hans; van der Togt, Chris; Spekreijse, Henk; Lamme, Victor A F

2003-04-15

When stimulus information enters the visual cortex, it is rapidly processed for identification. However, sometimes the processing of the stimulus is inadequate and the subject fails to notice the stimulus. Human psychophysical studies show that this occurs during states of inattention or absent-mindedness. At a neurophysiological level, it remains unclear what these states are. To study the role of cortical state in perception, we analyzed neural activity in the monkey primary visual cortex before the appearance of a stimulus. We show that, before the appearance of a reported stimulus, neural activity was stronger and more correlated than for a not-reported stimulus. This indicates that the strength of neural activity and the functional connectivity between neurons in the primary visual cortex participate in the perceptual processing of stimulus information. Thus, to detect a stimulus, the visual cortex needs to be in an appropriate state.

The Mere Exposure Instruction Effect.

PubMed

Van Dessel, Pieter; Mertens, Gaëtan; Smith, Colin Tucker; De Houwer, Jan

2017-09-01

The mere exposure effect refers to the well-established finding that people evaluate a stimulus more positively after repeated exposure to that stimulus. We investigated whether a change in stimulus evaluation can occur also when participants are not repeatedly exposed to a stimulus, but are merely instructed that one stimulus will occur frequently and another stimulus will occur infrequently. We report seven experiments showing that (1) mere exposure instructions influence implicit stimulus evaluations as measured with an Implicit Association Test (IAT), personalized Implicit Association Test (pIAT), or Affect Misattribution Procedure (AMP), but not with an Evaluative Priming Task (EPT), (2) mere exposure instructions influence explicit evaluations, and (3) the instruction effect depends on participants' memory of which stimulus will be presented more frequently. We discuss how these findings inform us about the boundary conditions of mere exposure instruction effects, as well as the mental processes that underlie mere exposure and mere exposure instruction effects.

Genotyping of Brucella melitensis strains from dromedary camels (Camelus dromedarius) from the United Arab Emirates with multiple-locus variable-number tandem repeat analysis.

PubMed

Gyuranecz, Miklós; Wernery, Ulli; Kreizinger, Zsuzsa; Juhász, Judit; Felde, Orsolya; Nagy, Péter

2016-04-15

Camel brucellosis is a widespread zoonotic disease in camel-rearing countries caused by Brucella melitensis and Brucella abortus. The aim of this study was the first genetic analysis of B. melitensis strains isolated from dromedary camels (Camelus dromedarius) using multiple-locus variable-number tandem repeat analysis (MLVA). MLVA 16 and its MLVA 8 and MLVA11 subsets were used to determine the genotypes of 15 B. melitensis isolates from dromedary camels (11 strains) and other host species (4 strains) from the United Arab Emirates and the results were then compared to B. melitensis MLVA genotypes from other parts of the world. Five, including two novel genotypes were identified with MLVA 8. MLVA 16 further discriminated these five genotypes to ten variants. The eleven camel isolates clustered into four main genetic groups within the East-Mediterranean and African clades and this clustering correlated with the geographic origin of the hosts (United Arab Emirates, Kingdom of Saudi Arabia and Sudan) and the date of their isolation. The camel strains were also genetically related to strains isolated from wild and domestic ruminants from their close habitat or from other parts of the world. Although limited number of strains were analysed, based on our data imported animals from foreign countries, local small ruminants and wildlife species are hypothesized to be the main sources of camel brucellosis in the United Arab Emirates. MLVA was successfully applied to determine the epidemiological links between the different camel B. melitensis infections in the United Arab Emirates and it can be a beneficial tool in future disease control programs. Copyright © 2016 Elsevier B.V. All rights reserved.

Contributions of retinal input and phenomenal representation of a fixation object to the saccadic gap effect.

PubMed

Ueda, Hiroshi; Takahashi, Kohske; Watanabe, Katsumi

2013-04-19

The saccadic "gap effect" refers to a phenomenon whereby saccadic reaction times (SRTs) are shortened by the removal of a visual fixation stimulus prior to target presentation. In the current study, we investigated whether the gap effect was influenced by retinal input of a fixation stimulus, as well as phenomenal permanence and/or expectation of the re-emergence of a fixation stimulus. In Experiment 1, we used an occluded fixation stimulus that was gradually hidden by a moving plate prior to the target presentation, which produced the impression that the fixation stimulus still remained and would reappear from behind the plate. We found that the gap effect was significantly weakened with the occluded fixation stimulus. However, the SRT with the occluded fixation stimulus was still shorter in comparison to when the fixation stimulus physically remained on the screen. In Experiment 2, we investigated whether this effect was due to phenomenal maintenance or expectation of the reappearance of the fixation stimulus; this was achieved by using occluding plates that were an identical color to the background screen, giving the impression of reappearance of the fixation stimulus but not of its maintenance. The result showed that the gap effect was still weakened by the same degree even without phenomenal maintenance of the fixation stimulus. These results suggest that the saccadic gap effect is modulated by both retinal input and subjective expectation of re-emergence of the fixation stimulus. In addition to oculomotor mechanisms, other components, such as attentional mechanisms, likely contribute to facilitation of the subsequent action. Copyright © 2013 Elsevier Ltd. All rights reserved.

The Physiology of Bone Pain. How Much Do We Really Know?

PubMed Central

Nencini, Sara; Ivanusic, Jason J.

2016-01-01

Pain is associated with most bony pathologies. Clinical and experimental observations suggest that bone pain can be derived from noxious stimulation of the periosteum or bone marrow. Sensory neurons are known to innervate the periosteum and marrow cavity, and most of these have a morphology and molecular phenotype consistent with a role in nociception. However, little is known about the physiology of these neurons, and therefore information about mechanisms that generate and maintain bone pain is lacking. The periosteum has received greater attention relative to the bone marrow, reflecting the easier access of the periosteum for experimental assessment. With the electrophysiological preparations used, investigators have been able to record from single periosteal units in isolation, and there is a lot of information available about how they respond to different stimuli, including those that are noxious. In contrast, preparations used to study sensory neurons that innervate the bone marrow have been limited to recording multi-unit activity in whole nerves, and whilst they clearly report responses to noxious stimulation, it is not possible to define responses for single sensory neurons that innervate the bone marrow. There is only limited evidence that peripheral sensory neurons that innervate bone can be sensitized or that they can be activated by multiple stimulus types, and at present this only exists in part for periosteal units. In the central nervous system, it is clear that spinal dorsal horn neurons can be activated by noxious stimuli applied to bone. Some can be sensitized under pathological conditions and may contribute in part to secondary or referred pain associated with bony pathology. Activity related to stimulation of sensory nerves that innervate bone has also been reported in neurons of the spinoparabrachial pathway and the somatosensory cortices, both known for roles in coding information about pain. Whilst these provide some clues as to the way information about bone pain is centrally coded, they need to be expanded to further our understanding of other central territories involved. There is a lot more to learn about the physiology of peripheral sensory neurons that innervate bone and their central projections. PMID:27199772

Antimicrobial Susceptibility and Clonality of Clinical Ureaplasma Isolates in the United States

PubMed Central

Fernández, Javier; Karau, Melissa J.; Cunningham, Scott A.; Greenwood-Quaintance, Kerryl E.

2016-01-01

Ureaplasma urealyticum and Ureaplasma parvum are pathogens involved in urogenital tract and intrauterine infections and also in systemic diseases in newborns and immunosuppressed patients. There is limited information on the antimicrobial susceptibility and clonality of these species. In this study, we report the susceptibility of 250 contemporary isolates of Ureaplasma (202 U. parvum and 48 U. urealyticum isolates) recovered at Mayo Clinic, Rochester, MN. MICs of doxycycline, azithromycin, ciprofloxacin, tetracycline, erythromycin, and levofloxacin were determined by broth microdilution, with MICS of the last three interpreted according to CLSI guidelines. Levofloxacin resistance was found in 6.4% and 5.2% of U. parvum and U. urealyticum isolates, respectively, while 27.2% and 68.8% of isolates, respectively, showed ciprofloxacin MICs of ≥4 μg/ml. The resistance mechanism of levofloxacin-resistant isolates was due to mutations in parC, with the Ser83Leu substitution being most frequent, followed by Glu87Lys. No macrolide resistance was found among the 250 isolates studied; a single U. parvum isolate was tetracycline resistant. tet(M) was found in 10 U. parvum isolates, including the single tetracycline-resistant isolate, as well as in 9 isolates which had low tetracycline and doxycycline MICs. Multilocus sequence typing (MLST) performed on a selection of 46 isolates showed high diversity within the clinical Ureaplasma isolates studied, regardless of antimicrobial susceptibility. The present work extends previous knowledge regarding susceptibility to antimicrobial agents, resistance mechanisms, and clonality of Ureaplasma species in the United States. PMID:27246773

Analysis of isolates within species of anuran trypanosomes using random amplified polymorphic DNA.

PubMed

Lun, Z R; Desser, S S

1996-01-01

A total of 20 decamer primers were used to generate random applied polymorphic DNA (RAPD) markers from 5 isolates of Trypanosoma fallisi, 3 isolates of T. ranarum, 2 isolates of T. rotatorium, and 2 isolates of T. rotatorium-like trypanosomes in addition to 2 species from the American Type Culture Collection, T. chattoni (ATCC 50294) and Trypanosoma sp. (ATCC 50295). A slight polymorphism was observed among the four isolates of T. fallisi obtained form American toads, Bufo americanus, collected in Algonquin Park, Ontario, Canada, and an isolate obtained from the same species of host collected in Marquette, Michigan, United States, and produced similarity coefficients ranging from 80.7% to 96.9%. Pronounced polymorphism was recorded among the three isolates of T. ranarum from bullfrogs, Rana catesbeiana, collected in Ontario, Canada, and in Maryland, United States, and from a Northern leopard frog, R. pipiens, collected in Minnesota (USA). The similarity coefficients ranged from 54.7% to 59.5%, suggesting that alleles of these isolates were conserved over a wide geographic range. The high degree of polymorphism observed in two isolates of T. rotatorium from a bullfrog collected in Ontario and two isolates of a T. rotatorium-like parasite from the green frog R. clamitans, collected in Louisiana (USA) suggests that they are different species. These results reflect the high similarity among isolates from the same geographic location and the pronounced polymorphism apparent among isolates from distant geographic locations.

Coding “What” and “When” in the Archer Fish Retina

PubMed Central

Vasserman, Genadiy; Shamir, Maoz; Ben Simon, Avi; Segev, Ronen

2010-01-01

Traditionally, the information content of the neural response is quantified using statistics of the responses relative to stimulus onset time with the assumption that the brain uses onset time to infer stimulus identity. However, stimulus onset time must also be estimated by the brain, making the utility of such an approach questionable. How can stimulus onset be estimated from the neural responses with sufficient accuracy to ensure reliable stimulus identification? We address this question using the framework of colour coding by the archer fish retinal ganglion cell. We found that stimulus identity, “what”, can be estimated from the responses of best single cells with an accuracy comparable to that of the animal's psychophysical estimation. However, to extract this information, an accurate estimation of stimulus onset is essential. We show that stimulus onset time, “when”, can be estimated using a linear-nonlinear readout mechanism that requires the response of a population of 100 cells. Thus, stimulus onset time can be estimated using a relatively simple readout. However, large nerve cell populations are required to achieve sufficient accuracy. PMID:21079682

A LANDSCAPE ECOLOGY APPROACH TO IDENTIFYING ECOLOGICAL VULNERABILITY IN GEOGRAPHICALLY ISOLATED WETLANDS

EPA Science Inventory

U.S. EPA 's Office of Research and Development is using a landscape approach to assess the ecological/hydrologic functions of geographically isolated wetlands in the mid-western, southern, and western regions of the United States. Geographically isolated wetlands are considered t...

Mapping isolated wetlands in a Karst landscape: GIS and remote sensing methods

EPA Science Inventory

Isolated wetlands occur in many areas of the United States, and although they are relatively common, they are a resource not yet thoroughly understood by the scientific community. Isolated wetlands have received increased attention recently, due to the 2001 Solid Waste Agency of ...

Stimulus homogeneity enhances implicit learning: evidence from contextual cueing.

PubMed

Feldmann-Wüstefeld, Tobias; Schubö, Anna

2014-04-01

Visual search for a target object is faster if the target is embedded in a repeatedly presented invariant configuration of distractors ('contextual cueing'). It has also been shown that the homogeneity of a context affects the efficiency of visual search: targets receive prioritized processing when presented in a homogeneous context compared to a heterogeneous context, presumably due to grouping processes at early stages of visual processing. The present study investigated in three Experiments whether context homogeneity also affects contextual cueing. In Experiment 1, context homogeneity varied on three levels of the task-relevant dimension (orientation) and contextual cueing was most pronounced for context configurations with high orientation homogeneity. When context homogeneity varied on three levels of the task-irrelevant dimension (color) and orientation homogeneity was fixed, no modulation of contextual cueing was observed: high orientation homogeneity led to large contextual cueing effects (Experiment 2) and low orientation homogeneity led to low contextual cueing effects (Experiment 3), irrespective of color homogeneity. Enhanced contextual cueing for homogeneous context configurations suggest that grouping processes do not only affect visual search but also implicit learning. We conclude that memory representation of context configurations are more easily acquired when context configurations can be processed as larger, grouped perceptual units. However, this form of implicit perceptual learning is only improved by stimulus homogeneity when stimulus homogeneity facilitates grouping processes on a dimension that is currently relevant in the task. Copyright © 2014 Elsevier B.V. All rights reserved.

Decoding conjunctions of direction-of-motion and binocular disparity from human visual cortex.

PubMed

Seymour, Kiley J; Clifford, Colin W G

2012-05-01

Motion and binocular disparity are two features in our environment that share a common correspondence problem. Decades of psychophysical research dedicated to understanding stereopsis suggest that these features interact early in human visual processing to disambiguate depth. Single-unit recordings in the monkey also provide evidence for the joint encoding of motion and disparity across much of the dorsal visual stream. Here, we used functional MRI and multivariate pattern analysis to examine where in the human brain conjunctions of motion and disparity are encoded. Subjects sequentially viewed two stimuli that could be distinguished only by their conjunctions of motion and disparity. Specifically, each stimulus contained the same feature information (leftward and rightward motion and crossed and uncrossed disparity) but differed exclusively in the way these features were paired. Our results revealed that a linear classifier could accurately decode which stimulus a subject was viewing based on voxel activation patterns throughout the dorsal visual areas and as early as V2. This decoding success was conditional on some voxels being individually sensitive to the unique conjunctions comprising each stimulus, thus a classifier could not rely on independent information about motion and binocular disparity to distinguish these conjunctions. This study expands on evidence that disparity and motion interact at many levels of human visual processing, particularly within the dorsal stream. It also lends support to the idea that stereopsis is subserved by early mechanisms also tuned to direction of motion.

Baroreflex Responses to Acute Changes in Blood Volume in Humans

NASA Technical Reports Server (NTRS)

Thompson, Cynthia A.; Tatro, Dana L.; Ludwig, David A.; Convertino, Victor A.

1990-01-01

To test the hypothesis that acute changes in plasma volume affect the stimulus-response relations of high- and low- pressure baroreflexes, eight men (27-44 yr old) underwent measurements for carotid-cardiac and cardiopulmonary baro- reflex responses under the following three volemic conditions: hypovolemic, normovolemic, and hypervolemic. The stimulus- response relation of the carotid-cardiac response curve was generated using a neck cuff device, which delivered pressure changes between +40 and -65 mmHg in continuous steps of 15 mmHg. The stimulus-response relationships of the cardiopulmonary baroreflex were studied by measurements of Forearm Vascular Resistance (FVR) and Peripheral Venotis Pressure (PVP) during low levels of lower body negative pressure (O to -20 mmHg). Altered vascular volume had no effect on response relations of the carotid-cardiac baroreflex but did alter the gain of the cardiopulmonary baroreflex (-7.93 q 1.71, -4.36 q 1.38, and -2.56 q 1.59 peripheral resistance units/mmHg for hypovolemic, normovolemic, and hypervolemic, respectively) independent of shifts in baseline FVR and PVP. These results indicate greater demand for vasoconstriction for equal reductions in venous pressure during progressive hypovolemia; this condition may compromise the capacity to provide adequate peripheral resistance during severe orthostatic stress. Fluid loading before reentry after spaceflight may act to restore vasoconstrictive capacity of the cardiopulnionary baroreflex but may not be an effective countermeasure against potential post- flight impairment of the carotid-cardiac baroreflex.

Local sensitivity to stimulus orientation and spatial frequency within the receptive fields of neurons in visual area 2 of macaque monkeys

PubMed Central

Tao, X.; Zhang, B.; Smith, E. L.; Nishimoto, S.; Ohzawa, I.

2012-01-01

We used dynamic dense noise stimuli and local spectral reverse correlation methods to reveal the local sensitivities of neurons in visual area 2 (V2) of macaque monkeys to orientation and spatial frequency within their receptive fields. This minimized the potentially confounding assumptions that are inherent in stimulus selections. The majority of neurons exhibited a relatively high degree of homogeneity for the preferred orientations and spatial frequencies in the spatial matrix of facilitatory subfields. However, about 20% of all neurons showed maximum orientation differences between neighboring subfields that were greater than 25 deg. The neurons preferring horizontal or vertical orientations showed less inhomogeneity in space than the neurons preferring oblique orientations. Over 50% of all units also exhibited suppressive profiles, and those were more heterogeneous than facilitatory profiles. The preferred orientation and spatial frequency of suppressive profiles differed substantially from those of facilitatory profiles, and the neurons with suppressive subfields had greater orientation selectivity than those without suppressive subfields. The peak suppression occurred with longer delays than the peak facilitation. These results suggest that the receptive field profiles of the majority of V2 neurons reflect the orderly convergence of V1 inputs over space, but that a subset of V2 neurons exhibit more complex response profiles having both suppressive and facilitatory subfields. These V2 neurons with heterogeneous subfield profiles could play an important role in the initial processing of complex stimulus features. PMID:22114163

Involvement of the human midbrain and thalamus in auditory deviance detection.

PubMed

Cacciaglia, Raffaele; Escera, Carles; Slabu, Lavinia; Grimm, Sabine; Sanjuán, Ana; Ventura-Campos, Noelia; Ávila, César

2015-02-01

Prompt detection of unexpected changes in the sensory environment is critical for survival. In the auditory domain, the occurrence of a rare stimulus triggers a cascade of neurophysiological events spanning over multiple time-scales. Besides the role of the mismatch negativity (MMN), whose cortical generators are located in supratemporal areas, cumulative evidence suggests that violations of auditory regularities can be detected earlier and lower in the auditory hierarchy. Recent human scalp recordings have shown signatures of auditory mismatch responses at shorter latencies than those of the MMN. Moreover, animal single-unit recordings have demonstrated that rare stimulus changes cause a release from stimulus-specific adaptation in neurons of the primary auditory cortex, the medial geniculate body (MGB), and the inferior colliculus (IC). Although these data suggest that change detection is a pervasive property of the auditory system which may reside upstream cortical sites, direct evidence for the involvement of subcortical stages in the human auditory novelty system is lacking. Using event-related functional magnetic resonance imaging during a frequency oddball paradigm, we here report that auditory deviance detection occurs in the MGB and the IC of healthy human participants. By implementing a random condition controlling for neural refractoriness effects, we show that auditory change detection in these subcortical stations involves the encoding of statistical regularities from the acoustic input. These results provide the first direct evidence of the existence of multiple mismatch detectors nested at different levels along the human ascending auditory pathway. Copyright © 2015 Elsevier Ltd. All rights reserved.

Quantitative responses of spinothalamic lamina I neurones to graded mechanical stimulation in the cat

PubMed Central

Andrew, David; Craig, A D (Bud)

2002-01-01

Nociceptive spinothalamic tract (STT) neurones in lamina I of the lumbosacral spinal cord of anaesthetized cats were characterized by recording their responses to graded mechanical stimulation with controlled forces of 10-120 g and probes of 5.0, 0.5 and 0.1 mm2 contact area. Neurones were identified by antidromic activation from the contralateral thalamus, and cells that responded to noxious stimulation were categorized as either nociceptive specific (NS, n = 20) or as polymodal nociceptive (HPC, responsive to heat, pinch and cold, n = 19) based on their responses to quantitative thermal stimuli. The mean responses of the 39 units increased linearly as stimulus intensity increased, and the population stimulus-response curves evoked by each of the three probes were all significantly different from each other. Thresholds were 45 g for the 5.0 mm2 probe, 30 g for the 0.5 mm2 probe and 20 g for the 0.1 mm2 probe. Further analysis showed that the NS neurones encoded both stimulus intensity and area (probe size) significantly better than HPC neurones in terms of their thresholds to individual probes, their peak discharge rates, their suprathreshold responsiveness and their ability to discriminate the three different probe sizes. These differences are consistent with the known differences between the mechanical encoding properties of A-fibre nociceptors, which provide the dominant inputs to NS neurones, and C-fibre nociceptors, which are the dominant inputs to HPC cells. Comparison of the stimulus-response curves of NS and HPC neurones indicated that the discharge of NS neurones better match the psychophysics of mechanical pain sensations in humans than the discharge of the HPC neurones do. Our findings support the view that NS neurones have a prominent role in mechanical pain and sharpness, and they corroborate the concept that the lamina I STT projection comprises several discrete channels that are integrated in the forebrain to generate qualitatively distinct sensations. PMID:12482896

Influence of double stimulation on sound-localization behavior in barn owls.

PubMed

Kettler, Lutz; Wagner, Hermann

2014-12-01

Barn owls do not immediately approach a source after they hear a sound, but wait for a second sound before they strike. This represents a gain in striking behavior by avoiding responses to random incidents. However, the first stimulus is also expected to change the threshold for perceiving the subsequent second sound, thus possibly introducing some costs. We mimicked this situation in a behavioral double-stimulus paradigm utilizing saccadic head turns of owls. The first stimulus served as an adapter, was presented in frontal space, and did not elicit a head turn. The second stimulus, emitted from a peripheral source, elicited the head turn. The time interval between both stimuli was varied. Data obtained with double stimulation were compared with data collected with a single stimulus from the same positions as the second stimulus in the double-stimulus paradigm. Sound-localization performance was quantified by the response latency, accuracy, and precision of the head turns. Response latency was increased with double stimuli, while accuracy and precision were decreased. The effect depended on the inter-stimulus interval. These results suggest that waiting for a second stimulus may indeed impose costs on sound localization by adaptation and this reduces the gain obtained by waiting for a second stimulus.

Generalization of a tactile stimulus in horses.

PubMed Central

Dougherty, D M; Lewis, P

1993-01-01

Using horses, we investigated the control of operant behavior by a tactile stimulus (the training stimulus) and the generalization of behavior to six other similar test stimuli. In a stall, the experimenters mounted a response panel in the doorway. Located on this panel were a response lever and a grain dispenser. The experimenters secured a tactile-stimulus belt to the horse's back. The stimulus belt was constructed by mounting seven solenoids along a piece of burlap in a manner that allowed each to provide the delivery of a tactile stimulus, a repetitive light tapping, at different locations (spaced 10.0 cm apart) along the horse's back. Two preliminary steps were necessary before generalization testing: training a measurable response (lip pressing) and training on several reinforcement schedules in the presence of a training stimulus (tapping by one of the solenoids). We then gave each horse two generalization test sessions. Results indicated that the horses' behavior was effectively controlled by the training stimulus. Horses made the greatest number of responses to the training stimulus, and the tendency to respond to the other test stimuli diminished as the stimuli became farther away from the training stimulus. These findings are discussed in the context of behavioral principles and their relevance to the training of horses. PMID:8315368

Generalization of a tactile stimulus in horses.

PubMed

Dougherty, D M; Lewis, P

1993-05-01

Using horses, we investigated the control of operant behavior by a tactile stimulus (the training stimulus) and the generalization of behavior to six other similar test stimuli. In a stall, the experimenters mounted a response panel in the doorway. Located on this panel were a response lever and a grain dispenser. The experimenters secured a tactile-stimulus belt to the horse's back. The stimulus belt was constructed by mounting seven solenoids along a piece of burlap in a manner that allowed each to provide the delivery of a tactile stimulus, a repetitive light tapping, at different locations (spaced 10.0 cm apart) along the horse's back. Two preliminary steps were necessary before generalization testing: training a measurable response (lip pressing) and training on several reinforcement schedules in the presence of a training stimulus (tapping by one of the solenoids). We then gave each horse two generalization test sessions. Results indicated that the horses' behavior was effectively controlled by the training stimulus. Horses made the greatest number of responses to the training stimulus, and the tendency to respond to the other test stimuli diminished as the stimuli became farther away from the training stimulus. These findings are discussed in the context of behavioral principles and their relevance to the training of horses.

Short-term memory for event duration: modality specificity and goal dependency.

PubMed

Takahashi, Kohske; Watanabe, Katsumi

2012-11-01

Time perception is involved in various cognitive functions. This study investigated the characteristics of short-term memory for event duration by examining how the length of the retention period affects inter- and intramodal duration judgment. On each trial, a sample stimulus was followed by a comparison stimulus, after a variable delay period (0.5-5 s). The sample and comparison stimuli were presented in the visual or auditory modality. The participants determined whether the comparison stimulus was longer or shorter than the sample stimulus. The distortion pattern of subjective duration during the delay period depended on the sensory modality of the comparison stimulus but was not affected by that of the sample stimulus. When the comparison stimulus was visually presented, the retained duration of the sample stimulus was shortened as the delay period increased. Contrarily, when the comparison stimulus was presented in the auditory modality, the delay period had little to no effect on the retained duration. Furthermore, whenever the participants did not know the sensory modality of the comparison stimulus beforehand, the effect of the delay period disappeared. These results suggest that the memory process for event duration is specific to sensory modality and that its performance is determined depending on the sensory modality in which the retained duration will be used subsequently.

Electrophysiology and Innervation of the Photosensitive Epistellar Body in the Lesser Octopus Eledone cirrhosa.

PubMed

Cobb, C S; Williamson, R

1998-08-01

The innervation and responses to light of the cephalopod epistellar body were investigated in preparations isolated from the stellate ganglia of the lesser or northern octopus, Eledone cirrhosa. Extracellular generator potentials in response to flashes of light were recorded from these photosensitive vesicles, with the amplitude of the response being found to be dependent upon the intensity of the flash and the level of ambient illumination. Intracellular recordings from photoreceptor cells of the epistellar body showed that they had resting potentials of about -49 +/- 7 mV (mean +/- SD, n = 43) and were depolarized by flashes of white, but not red (>650 nm) light. The evoked depolarization consisted of a transient component, followed by a steady plateau in which the amplitude of the depolarization was well correlated with the log of the stimulus intensity. The evoked depolarizations induced action potentials in the photoreceptor cells, with the frequency of firing being well correlated with the stimulus intensity. The morphologies of individual photoreceptor cells were visualized by intracellular injections of the fluorescent dye Lucifer yellow, and the path of the epistellar nerve across the stellate ganglion, into the pallial nerve, toward the brain was traced using the lipophilic dye Di-I. This pathway was confirmed physiologically by recording light-evoked responses from the cut end of the pallial nerve.

Wireless Strain Measurement with a Micromachined Magnetoelastic Resonator Using Ringdown Frequency Locking

PubMed Central

Green, Scott R.; Gianchandani, Yogesh B.

2017-01-01

Resonant magnetoelastic devices are widely used as anti-theft tags and are also being investigated for a range of sensing applications. The vast majority of magnetoelastic devices are operated at resonance, and rely upon an external interface to wirelessly detect the resonant frequency, and other characteristics. For micromachined devices, this detection method must accommodate diminished signal strength and elevated resonant frequencies. Feedthrough of the interrogating stimulus to the detector also presents a significant challenge. This paper describes a method of interrogating wireless magnetoelastic strain sensors using a new frequency-lock approach. Following a brief excitation pulse, the sensor ring-down is analyzed and a feedback loop is used to match the excitation frequency and the resonant frequency. Data acquisition hardware is used in conjunction with custom software to implement the frequency-lock loop. Advantages of the method include temporal isolation of interrogating stimulus from the sensor response and near real-time tracking of resonant frequencies. The method was investigated using a family of wireless strain sensors with resonant frequencies ranging from 120 to 240 kHz. Strain levels extending to 3.5 mstrain and sensitivities up to 14300 ppm/mstrain were measured with response times faster than 0.5 s. The standard deviation of the locked frequency did not exceed 0.1%. PMID:28713873

The power of instructions: Proactive configuration of stimulus-response translation.

PubMed

Meiran, Nachshon; Pereg, Maayan; Kessler, Yoav; Cole, Michael W; Braver, Todd S

2015-05-01

Humans are characterized by an especially highly developed ability to use instructions to prepare toward upcoming events; yet, it is unclear just how powerful instructions can be. Although prior work provides evidence that instructions can be sufficiently powerful to proactively program working memory to execute stimulus-response (S-R) translations, in a reflexlike fashion (intention-based reflexivity [IBR]), the results to date have been equivocal. To overcome this shortcoming, we developed, and tested in 4 studies, a novel paradigm (the NEXT paradigm) that isolates IBR effects even prior to first task execution. In each miniblock, participants received S-R mapping instructions for a new task. Prior to implementing this mapping, responses were required to advance through screens during a preparatory (NEXT) phase. When the NEXT response was incompatible with the instructed S-R mapping, interference (IBR effect) was observed. This NEXT compatibility effect and performance in the implementation (GO) trials barely changed when prior practice of a few trials was provided. Finally, a manipulation that encouraged preparation resulted in relatively durable NEXT compatibility effects (indicating durable preparatory efforts) coupled with improved GO performance (indicating the success of these efforts). Together, these findings establish IBR as a marker of instructed proactive control. (c) 2015 APA, all rights reserved).

Self-organization of head-centered visual responses under ecological training conditions.

PubMed

Mender, Bedeho M W; Stringer, Simon M

2014-01-01

We have studied the development of head-centered visual responses in an unsupervised self-organizing neural network model which was trained under ecological training conditions. Four independent spatio-temporal characteristics of the training stimuli were explored to investigate the feasibility of the self-organization under more ecological conditions. First, the number of head-centered visual training locations was varied over a broad range. Model performance improved as the number of training locations approached the continuous sampling of head-centered space. Second, the model depended on periods of time where visual targets remained stationary in head-centered space while it performed saccades around the scene, and the severity of this constraint was explored by introducing increasing levels of random eye movement and stimulus dynamics. Model performance was robust over a range of randomization. Third, the model was trained on visual scenes where multiple simultaneous targets where always visible. Model self-organization was successful, despite never being exposed to a visual target in isolation. Fourth, the duration of fixations during training were made stochastic. With suitable changes to the learning rule, it self-organized successfully. These findings suggest that the fundamental learning mechanism upon which the model rests is robust to the many forms of stimulus variability under ecological training conditions.

Modelling auditory attention

PubMed Central

Kaya, Emine Merve

2017-01-01

Sounds in everyday life seldom appear in isolation. Both humans and machines are constantly flooded with a cacophony of sounds that need to be sorted through and scoured for relevant information—a phenomenon referred to as the ‘cocktail party problem’. A key component in parsing acoustic scenes is the role of attention, which mediates perception and behaviour by focusing both sensory and cognitive resources on pertinent information in the stimulus space. The current article provides a review of modelling studies of auditory attention. The review highlights how the term attention refers to a multitude of behavioural and cognitive processes that can shape sensory processing. Attention can be modulated by ‘bottom-up’ sensory-driven factors, as well as ‘top-down’ task-specific goals, expectations and learned schemas. Essentially, it acts as a selection process or processes that focus both sensory and cognitive resources on the most relevant events in the soundscape; with relevance being dictated by the stimulus itself (e.g. a loud explosion) or by a task at hand (e.g. listen to announcements in a busy airport). Recent computational models of auditory attention provide key insights into its role in facilitating perception in cluttered auditory scenes. This article is part of the themed issue ‘Auditory and visual scene analysis’. PMID:28044012

Extracting binaural information from simultaneous targets and distractors: Effects of amplitude modulation and asynchronous envelopes

PubMed Central

Stellmack, Mark A.; Byrne, Andrew J.; Viemeister, Neal F.

2010-01-01

When different components of a stimulus carry different binaural information, processing of binaural information in a target component is often affected. The present experiments examine whether such interference is affected by amplitude modulation and the relative phase of modulation of the target and distractors. In all experiments, listeners attempted to discriminate interaural time differences of a target stimulus in the presence of distractor stimuli with ITD=0. In Experiment 1, modulation of the distractors but not the target reduced interference between components. In Experiment 2, synthesized musical notes exhibited little binaural interference when there were slight asynchronies between different streams of notes (31 or 62 ms). The remaining experiments suggested that the reduction in binaural interference in the previous experiments was due neither to the complex spectra of the synthesized notes nor to greater detectability of the target in the presence of modulated distractors. These data suggest that this interference is reduced when components are modulated in ways that result in the target appearing briefly in isolation, not because of segregation cues. These data also suggest that modulation and asynchronies between modulators that might be encountered in real-world listening situations are adequate to reduce binaural interference to inconsequential levels. PMID:20815459

Distinct neural and neuromuscular strategies underlie independent evolution of simplified advertisement calls

PubMed Central

Leininger, Elizabeth C.; Kelley, Darcy B.

2013-01-01

Independent or convergent evolution can underlie phenotypic similarity of derived behavioural characters. Determining the underlying neural and neuromuscular mechanisms sheds light on how these characters arose. One example of evolutionarily derived characters is a temporally simple advertisement call of male African clawed frogs (Xenopus) that arose at least twice independently from a more complex ancestral pattern. How did simplification occur in the vocal circuit? To distinguish shared from divergent mechanisms, we examined activity from the calling brain and vocal organ (larynx) in two species that independently evolved simplified calls. We find that each species uses distinct neural and neuromuscular strategies to produce the simplified calls. Isolated  Xenopus borealis brains produce fictive vocal patterns that match temporal patterns of actual male calls; the larynx converts nerve activity faithfully into muscle contractions and single clicks. In contrast, fictive patterns from isolated Xenopus boumbaensis brains are short bursts of nerve activity; the isolated larynx requires stimulus bursts to produce a single click of sound. Thus, unlike X. borealis, the output of the X. boumbaensis hindbrain vocal pattern generator is an ancestral burst-type pattern, transformed by the larynx into single clicks. Temporally simple advertisement calls in genetically distant species of Xenopus have thus arisen independently via reconfigurations of central and peripheral vocal neuroeffectors. PMID:23407829

Distinct neural and neuromuscular strategies underlie independent evolution of simplified advertisement calls.

PubMed

Leininger, Elizabeth C; Kelley, Darcy B

2013-04-07

Independent or convergent evolution can underlie phenotypic similarity of derived behavioural characters. Determining the underlying neural and neuromuscular mechanisms sheds light on how these characters arose. One example of evolutionarily derived characters is a temporally simple advertisement call of male African clawed frogs (Xenopus) that arose at least twice independently from a more complex ancestral pattern. How did simplification occur in the vocal circuit? To distinguish shared from divergent mechanisms, we examined activity from the calling brain and vocal organ (larynx) in two species that independently evolved simplified calls. We find that each species uses distinct neural and neuromuscular strategies to produce the simplified calls. Isolated Xenopus borealis brains produce fictive vocal patterns that match temporal patterns of actual male calls; the larynx converts nerve activity faithfully into muscle contractions and single clicks. In contrast, fictive patterns from isolated Xenopus boumbaensis brains are short bursts of nerve activity; the isolated larynx requires stimulus bursts to produce a single click of sound. Thus, unlike X. borealis, the output of the X. boumbaensis hindbrain vocal pattern generator is an ancestral burst-type pattern, transformed by the larynx into single clicks. Temporally simple advertisement calls in genetically distant species of Xenopus have thus arisen independently via reconfigurations of central and peripheral vocal neuroeffectors.

Stimulus onset predictability modulates proactive action control in a Go/No-go task

PubMed Central

Berchicci, Marika; Lucci, Giuliana; Spinelli, Donatella; Di Russo, Francesco

2015-01-01

The aim of the study was to evaluate whether the presence/absence of visual cues specifying the onset of an upcoming, action-related stimulus modulates pre-stimulus brain activity, associated with the proactive control of goal-directed actions. To this aim we asked 12 subjects to perform an equal probability Go/No-go task with four stimulus configurations in two conditions: (1) uncued, i.e., without any external information about the timing of stimulus onset; and (2) cued, i.e., with external visual cues providing precise information about the timing of stimulus onset. During task both behavioral performance and event-related potentials (ERPs) were recorded. Behavioral results showed faster response times in the cued than uncued condition, confirming existing literature. ERPs showed novel results in the proactive control stage, that started about 1 s before the motor response. We observed a slow rising prefrontal positive activity, more pronounced in the cued than the uncued condition. Further, also pre-stimulus activity of premotor areas was larger in cued than uncued condition. In the post-stimulus period, the P3 amplitude was enhanced when the time of stimulus onset was externally driven, confirming that external cueing enhances processing of stimulus evaluation and response monitoring. Our results suggest that different pre-stimulus processing come into play in the two conditions. We hypothesize that the large prefrontal and premotor activities recorded with external visual cues index the monitoring of the external stimuli in order to finely regulate the action. PMID:25964751

33 CFR 62.29 - Isolated danger marks.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 33 Navigation and Navigable Waters 1 2013-07-01 2013-07-01 false Isolated danger marks. 62.29 Section 62.29 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY AIDS TO NAVIGATION UNITED STATES AIDS TO NAVIGATION SYSTEM The U.S. Aids to Navigation System § 62.29 Isolated danger...

33 CFR 62.29 - Isolated danger marks.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 33 Navigation and Navigable Waters 1 2014-07-01 2014-07-01 false Isolated danger marks. 62.29 Section 62.29 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY AIDS TO NAVIGATION UNITED STATES AIDS TO NAVIGATION SYSTEM The U.S. Aids to Navigation System § 62.29 Isolated danger...

33 CFR 62.29 - Isolated danger marks.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 33 Navigation and Navigable Waters 1 2012-07-01 2012-07-01 false Isolated danger marks. 62.29 Section 62.29 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY AIDS TO NAVIGATION UNITED STATES AIDS TO NAVIGATION SYSTEM The U.S. Aids to Navigation System § 62.29 Isolated danger...

33 CFR 62.29 - Isolated danger marks.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 33 Navigation and Navigable Waters 1 2011-07-01 2011-07-01 false Isolated danger marks. 62.29 Section 62.29 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY AIDS TO NAVIGATION UNITED STATES AIDS TO NAVIGATION SYSTEM The U.S. Aids to Navigation System § 62.29 Isolated danger...

Mycelial compatibility and aggressiveness comparison of Sclerotinia sclerotiorum isolates from Brazil and the United States

USDA-ARS?s Scientific Manuscript database

Variability of Sclerotinia sclerotiorum isolates collected in Brazil and the USA were determined by mycelial compatibility grouping (MCG) and inoculations of soybean cultivars. Two experiments for MCGs and two for aggressiveness were conducted with two sets of isolates. The first set included nine i...

33 CFR 62.29 - Isolated danger marks.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Isolated danger marks. 62.29 Section 62.29 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY AIDS TO NAVIGATION UNITED STATES AIDS TO NAVIGATION SYSTEM The U.S. Aids to Navigation System § 62.29 Isolated danger...

Baseline Sensitivity to Fluopicolide in Phytophthora Capsici Isolates from the Eastern United States

USDA-ARS?s Scientific Manuscript database

Fluopicolide was registered in 2007 to control diseases caused by Oomycete pathogens such as Phytophthora capsici on cucurbits and peppers. In this study, 69 isolates of P. capsici from Michigan (24 isolates), South Carolina (17), Georgia (14), Florida (11), and North Carolina (3) recovered from wa...

Molecular characterization of resistance to extended-spectrum cephalosporins in clinical Escherichia coli isolates from companion animals in the United States.

PubMed

Shaheen, Bashar W; Nayak, Rajesh; Foley, Steven L; Kweon, Ohgew; Deck, Joanna; Park, Miseon; Rafii, Fatemeh; Boothe, Dawn M

2011-12-01

Resistance to extended-spectrum cephalosporins (ESC) among members of the family Enterobacteriaceae occurs worldwide; however, little is known about ESC resistance in Escherichia coli strains from companion animals. Clinical isolates of E. coli were collected from veterinary diagnostic laboratories throughout the United States from 2008 to 2009. E. coli isolates (n = 54) with reduced susceptibility to ceftazidime or cefotaxime (MIC ≥ 16 μg/ml) and extended-spectrum-β-lactamase (ESBL) phenotypes were analyzed. PCR and sequencing were used to detect mutations in ESBL-encoding genes and the regulatory region of the chromosomal gene ampC. Conjugation experiments and plasmid identification were conducted to examine the transferability of resistance to ESCs. All isolates carried the bla(CTX-M-1)-group β-lactamase genes in addition to one or more of the following β-lactamase genes: bla(TEM), bla(SHV-3), bla(CMY-2), bla(CTX-M-14-like), and bla(OXA-1.) Different bla(TEM) sequence variants were detected in some isolates (n = 40). Three isolates harbored a bla(TEM-181) gene with a novel mutation resulting in an Ala184Val substitution. Approximately 78% of the isolates had mutations in promoter/attenuator regions of the chromosomal gene ampC, one of which was a novel insertion of adenine between bases -28 and -29. Plasmids ranging in size from 11 to 233 kbp were detected in the isolates, with a common plasmid size of 93 kbp identified in 60% of isolates. Plasmid-mediated transfer of β-lactamase genes increased the MICs (≥ 16-fold) of ESCs for transconjugants. Replicon typing among isolates revealed the predominance of IncI and IncFIA plasmids, followed by IncFIB plasmids. This study shows the emergence of conjugative plasmid-borne ESBLs among E. coli strains from companion animals in the United States, which may compromise the effective therapeutic use of ESCs in veterinary medicine.

Room contamination, patient colonization pressure, and the risk of vancomycin-resistant Enterococcus colonization on a unit dedicated to the treatment of hematologic malignancies and hematopoietic stem cell transplantation.

PubMed

Ford, Clyde D; Lopansri, Bert K; Gazdik, Michaela A; Webb, Brandon; Snow, Gregory L; Hoda, Daanish; Adams, Barbara; Petersen, Finn Bo

2016-10-01

Contaminated surfaces and colonization pressure are risk factors for vancomycin-resistant Enterococcus (VRE) colonization in intensive care units (ICUs). Whether these apply to modern units dedicated to the care of hematologic malignancies and hematopoietic stem cell transplant (HSCT) procedures is unknown. We reviewed the records of 780 consecutive admissions for acute leukemia, autologous HSCT, or allogeneic HSCT in which the patient was at risk for hospital-acquired VRE and underwent weekly surveillance. We also obtained staff and room cultures, observed staff behavior, and performed VRE molecular strain typing on selected isolates. The overall rate of VRE colonization was 11.4 cases/1,000 patient days. Cultures of room surfaces revealed VRE isolates in 10% of terminally cleaned rooms. A prior VRE-colonized room occupant did not increase risk, and paired isolates from 20 patients and prior occupants were indistinguishable on molecular typing in only 1 pair. VRE colonization pressure was significantly associated with acquisition. Cultures of unit personnel and shared equipment were negative except for weighing scales. Observation of unit clinical personnel showed high compliance for hand sanitation and but less so for gowns. Conversely, ancillary staff showed poor compliance. Transmission of VRE from room surfaces seems to be an infrequent event. Encouraging adherence to surveillance, disinfection, and contact isolation protocols may decrease VRE colonization rates. Copyright © 2016. Published by Elsevier Inc.

Comparative Analysis of Extended-Spectrum-β-Lactamase CTX-M-65-Producing Salmonella enterica Serovar Infantis Isolates from Humans, Food Animals, and Retail Chickens in the United States

PubMed Central

Folster, Jason P.; Hsu, Chih-Hao; Chen, Jessica; Hoffmann, Maria; Li, Cong; Morales, Cesar; Tyson, Gregory H.; Mukherjee, Sampa; Brown, Allison C.; Green, Alice; Wilson, Wanda; Dessai, Uday; Abbott, Jason; Joseph, Lavin; Haro, Jovita; Ayers, Sherry; McDermott, Patrick F.; Zhao, Shaohua

2017-01-01

ABSTRACT We sequenced the genomes of 10 Salmonella enterica serovar Infantis isolates containing blaCTX-M-65 obtained from chicken, cattle, and human sources collected between 2012 and 2015 in the United States through routine National Antimicrobial Resistance Monitoring System (NARMS) surveillance and product sampling programs. We also completely assembled the plasmids from four of the isolates. All isolates had a D87Y mutation in the gyrA gene and harbored between 7 and 10 resistance genes [aph(4)-Ia, aac(3)-IVa, aph(3′)-Ic, blaCTX-M-65, fosA3, floR, dfrA14, sul1, tetA, aadA1] located in two distinct sites of a megaplasmid (∼316 to 323 kb) similar to that described in a blaCTX-M-65-positive S. Infantis isolate from a patient in Italy. High-quality single nucleotide polymorphism (hqSNP) analysis revealed that all U.S. isolates were closely related, separated by only 1 to 38 pairwise high-quality SNPs, indicating a high likelihood that strains from humans, chickens, and cattle recently evolved from a common ancestor. The U.S. isolates were genetically similar to the blaCTX-M-65-positive S. Infantis isolate from Italy, with a separation of 34 to 47 SNPs. This is the first report of the blaCTX-M-65 gene and the pESI (plasmid for emerging S. Infantis)-like megaplasmid from S. Infantis in the United States, and it illustrates the importance of applying a global One Health human and animal perspective to combat antimicrobial resistance. PMID:28483962

Comparative Analysis of Extended-Spectrum-β-Lactamase CTX-M-65-Producing Salmonella enterica Serovar Infantis Isolates from Humans, Food Animals, and Retail Chickens in the United States.

PubMed

Tate, Heather; Folster, Jason P; Hsu, Chih-Hao; Chen, Jessica; Hoffmann, Maria; Li, Cong; Morales, Cesar; Tyson, Gregory H; Mukherjee, Sampa; Brown, Allison C; Green, Alice; Wilson, Wanda; Dessai, Uday; Abbott, Jason; Joseph, Lavin; Haro, Jovita; Ayers, Sherry; McDermott, Patrick F; Zhao, Shaohua

2017-07-01

We sequenced the genomes of 10 Salmonella enterica serovar Infantis isolates containing bla CTX-M-65 obtained from chicken, cattle, and human sources collected between 2012 and 2015 in the United States through routine National Antimicrobial Resistance Monitoring System (NARMS) surveillance and product sampling programs. We also completely assembled the plasmids from four of the isolates. All isolates had a D87Y mutation in the gyrA gene and harbored between 7 and 10 resistance genes [ aph(4)-Ia , aac(3)-IVa , aph(3 ' )-Ic , bla CTX-M-65 , fosA3 , floR , dfrA14 , sul1 , tetA , aadA1 ] located in two distinct sites of a megaplasmid (∼316 to 323 kb) similar to that described in a bla CTX-M-65 -positive S Infantis isolate from a patient in Italy. High-quality single nucleotide polymorphism (hqSNP) analysis revealed that all U.S. isolates were closely related, separated by only 1 to 38 pairwise high-quality SNPs, indicating a high likelihood that strains from humans, chickens, and cattle recently evolved from a common ancestor. The U.S. isolates were genetically similar to the bla CTX-M-65 -positive S Infantis isolate from Italy, with a separation of 34 to 47 SNPs. This is the first report of the bla CTX-M-65 gene and the pESI (plasmid for emerging S Infantis)-like megaplasmid from S Infantis in the United States, and it illustrates the importance of applying a global One Health human and animal perspective to combat antimicrobial resistance. Copyright © 2017 American Society for Microbiology.

Responses of Rostral Fastigial Nucleus Neurons of Conscious Cats to Rotations in Vertical Planes

PubMed Central

Miller, D. M.; Cotter, L.A.; Gandhi, N. J.; Schor, R. H.; Huff, N. O.; Raj, S. G.; Shulman, J. A.; Yates, B. J.

2008-01-01

The rostral fastigial nucleus (RFN) of the cerebellum is thought to play an important role in postural control, and recent studies in conscious nonhuman primates suggest that this region also participates in the sensory processing required to compute body motion in space. The goal of the present study was to examine the dynamic and spatial responses to sinusoidal rotations in vertical planes of RFN neurons in conscious cats, and determine if they are similar to responses reported for monkeys. Approximately half of the RFN neurons examined were classified as graviceptive, since their firing was synchronized with stimulus position and the gain of their responses was relatively unaffected by the frequency of the tilts. The large majority (80%) of graviceptive RFN neurons were activated by pitch rotations. Most of the remaining RFN units exhibited responses to vertical oscillations that encoded stimulus velocity, and approximately 50% of these velocity units had a response vector orientation aligned near the plane of a single vertical semicircular canal. Unlike in primates, few feline RFN neurons had responses to vertical rotations that suggested integration of graviceptive (otolith) and velocity (vertical semicircular canal) signals. These data indicate that the physiological role of the RFN may differ between primates and lower mammals. The RFN in rats and cats in known to be involved in adjusting blood pressure and breathing during postural alterations in the transverse (pitch) plane. The relatively simple responses of many RFN neurons in cats are appropriate for triggering such compensatory autonomic responses. PMID:18571332

Interdependent encoding of pitch, timbre and spatial location in auditory cortex

PubMed Central

Bizley, Jennifer K.; Walker, Kerry M. M.; Silverman, Bernard W.; King, Andrew J.; Schnupp, Jan W. H.

2009-01-01

Because we can perceive the pitch, timbre and spatial location of a sound source independently, it seems natural to suppose that cortical processing of sounds might separate out spatial from non-spatial attributes. Indeed, recent studies support the existence of anatomically segregated ‘what’ and ‘where’ cortical processing streams. However, few attempts have been made to measure the responses of individual neurons in different cortical fields to sounds that vary simultaneously across spatial and non-spatial dimensions. We recorded responses to artificial vowels presented in virtual acoustic space to investigate the representations of pitch, timbre and sound source azimuth in both core and belt areas of ferret auditory cortex. A variance decomposition technique was used to quantify the way in which altering each parameter changed neural responses. Most units were sensitive to two or more of these stimulus attributes. Whilst indicating that neural encoding of pitch, location and timbre cues is distributed across auditory cortex, significant differences in average neuronal sensitivity were observed across cortical areas and depths, which could form the basis for the segregation of spatial and non-spatial cues at higher cortical levels. Some units exhibited significant non-linear interactions between particular combinations of pitch, timbre and azimuth. These interactions were most pronounced for pitch and timbre and were less commonly observed between spatial and non-spatial attributes. Such non-linearities were most prevalent in primary auditory cortex, although they tended to be small compared with stimulus main effects. PMID:19228960

The effect of changes in stimulus level on electrically evoked cortical auditory potentials.

PubMed

Kim, Jae-Ryong; Brown, Carolyn J; Abbas, Paul J; Etler, Christine P; O'Brien, Sara

2009-06-01

The purpose of this study was to determine whether the electrically evoked acoustic change complex (EACC) could be used to assess sensitivity to changes in stimulus level in cochlear implant (CI) recipients and to investigate the relationship between EACC amplitude and rate of growth of the N1-P2 onset response with increases in stimulus level. Twelve postlingually deafened adults using Nucleus CI24 CIs participated in this study. Nucleus Implant Communicator (NIC) routines were used to bypass the speech processor and to control the stimulation of the implant directly. The stimulus consisted of an 800 msec burst of a 1000 pps biphasic pulse train. A change in the stimulus level was introduced 400 msec after stimulus onset. Band-pass filtering (1 to 100 Hz) was used to minimize stimulus artifact. Four to six recordings of 50 sweeps were obtained for each condition, and averaged responses were analyzed in the time domain using standard peak picking procedures. Cortical auditory change potentials were recorded from CI users in response to both increases and decreases in stimulation level. The amplitude of the EACC was found to be dependent on the magnitude of the stimulus change. Increases in stimulus level elicited more robust EACC responses than decreases in stimulus level. Also, EACC amplitudes were significantly correlated with the slope of the growth of the onset response. This work describes the effect of change in stimulus level on electrically evoked auditory change potentials in CI users. The amplitude of the EACC was found to be related both to the magnitude of the stimulus change introduced and to the rate of growth of the N1-P2 onset response. To the extent that the EACC reflects processing of stimulus change, it could potentially be a valuable tool for assessing neural processing of the kinds of stimulation patterns produced by a CI. Further studies are needed, however, to determine the relationships between the EACC and psychophysical measures of intensity discrimination in CI recipients.

Using Single-trial EEG to Predict and Analyze Subsequent Memory

PubMed Central

Noh, Eunho; Herzmann, Grit; Curran, Tim; de Sa, Virginia R.

2013-01-01

We show that it is possible to successfully predict subsequent memory performance based on single-trial EEG activity before and during item presentation in the study phase. Two-class classification was conducted to predict subsequently remembered vs. forgotten trials based on subjects’ responses in the recognition phase. The overall accuracy across 18 subjects was 59.6 % by combining pre- and during-stimulus information. The single-trial classification analysis provides a dimensionality reduction method to project the high-dimensional EEG data onto a discriminative space. These projections revealed novel findings in the pre- and during-stimulus period related to levels of encoding. It was observed that the pre-stimulus information (specifically oscillatory activity between 25–35Hz) −300 to 0 ms before stimulus presentation and during-stimulus alpha (7–12 Hz) information between 1000–1400 ms after stimulus onset distinguished between recollection and familiarity while the during-stimulus alpha information and temporal information between 400–800 ms after stimulus onset mapped these two states to similar values. PMID:24064073

Activity-dependent extracellular K+ accumulation in rat optic nerve: the role of glial and axonal Na+ pumps

PubMed Central

Ransom, Christopher B; Ransom, Bruce R; Sontheimer, Harald

2000-01-01

We measured activity-dependent changes in [K+]o with K+-selective microelectrodes in adult rat optic nerve, a CNS white matter tract, to investigate the factors responsible for post-stimulus recovery of [K+]o.Post-stimulus recovery of [K+]o followed a double-exponential time course with an initial, fast time constant, τfast, of 0.9 ± 0.2 s (mean ±s.d.) and a later, slow time constant, τslow, of 4.2 ± 1 s following a 1 s, 100 Hz stimulus. τfast, but not τslow, decreased with increasing activity-dependent rises in [K+]o. τslow, but not τfast, increased with increasing stimulus duration.Post-stimulus recovery of [K+]o was temperature sensitive. The apparent temperature coefficients (Q10, 27–37°C) for the fast and slow components following a 1 s, 100 Hz stimulus were 1.7 and 2.6, respectively.Post-stimulus recovery of [K+]o was sensitive to Na+ pump inhibition with 50 μM strophanthidin. Following a 1 s, 100 Hz stimulus, 50 μM strophanthidin increased τfast and τslow by 81 and 464%, respectively. Strophanthidin reduced the temperature sensitivity of post-stimulus recovery of [K+]o.Post-stimulus recovery of [K+]o was minimally affected by the K+ channel blocker Ba2+ (0.2 mm). Following a 10 s, 100 Hz stimulus, 0.2 mm Ba2+ increased τfast and τslow by 24 and 18%, respectively.Stimulated increases in [K+]o were followed by undershoots of [K+]o. Post-stimulus undershoot amplitude increased with stimulus duration but was independent of the peak preceding [K+]o increase.These observations imply that two distinct processes contribute to post-stimulus recovery of [K+]o in central white matter. The results are compatible with a model of K+ removal that attributes the fast, initial phase of K+ removal to K+ uptake by glial Na+ pumps and the slower, sustained decline to K+ uptake via axonal Na+ pumps. PMID:10713967

Does air gas aesthesiometry generate a true mechanical stimulus for corneal sensitivity measurement?

PubMed

Nosch, Daniela S; Pult, Heiko; Albon, Julie; Purslow, Christine; Murphy, Paul J

2018-03-01

Belmonte Ocular Pain Meter (OPM) air jet aesthesiometry overcomes some of the limitations of the Cochet-Bonnet aesthesiometer. However, for true mechanical corneal sensitivity measurement, the airflow stimulus temperature of the aesthesiometer must equal ocular surface temperature (OST), to avoid additional response from temperature-sensitive nerves. The aim of this study was to determine: (A) the stimulus temperature inducing no or least change in OST; and (B) to evaluate if OST remains unchanged with different stimulus durations and airflow rates. A total of 14 subjects (mean age 25.14 ± 2.18 years; seven women) participated in this clinical cohort study: (A) OST was recorded using an infrared camera (FLIR A310) during the presentation of airflow stimuli, at five temperatures, ambient temperature (AT) +5°C, +10°C, +15°C, +20°C and +30°C, using the OPM aesthesiometer (duration three seconds; over a four millimetre distance; airflow rate 60 ml/min); and (B) OST measurements were repeated with two stimulus temperatures (AT +10°C and +15°C) while varying stimulus durations (three seconds and five seconds) and airflow rates (30, 60, 80 and 100 ml/min). Inclusion criteria were age <40 years, no contact lens wear, absence of ocular disease including dry eye, and no use of artificial tears. Repeated measures (analysis of variance) and appropriate post-hoc t-tests were applied. (A) Stimulus temperatures of AT +10°C and +15°C induced the least changes in OST (-0.20 ± 0.13°C and 0.08 ± 0.05°C). (B) OST changes were statistically significant with both stimulus temperatures and increased with increasing airflow rates (p < 0.001), and were more marked with stimulus temperature AT +10°C. A true mechanical threshold for corneal sensitivity cannot be established with the air stimulus of the Belmonte OPM because its air jet stimulus with mechanical setting is likely to have a thermal component. Appropriate stimulus selection for an air jet aesthesiometer must incorporate stimulus temperature control that can vary with stimulus duration and airflow rate. © 2017 Optometry Australia.

Detection of neonatal unit clusters of Candida parapsilosis fungaemia by microsatellite genotyping: Results from laboratory-based sentinel surveillance, South Africa, 2009-2010.

PubMed

Magobo, Rindidzani E; Naicker, Serisha D; Wadula, Jeannette; Nchabeleng, Maphoshane; Coovadia, Yacoob; Hoosen, Anwar; Lockhart, Shawn R; Govender, Nelesh P

2017-05-01

Neonatal candidaemia is a common, deadly and costly hospital-associated disease. To determine the genetic diversity of Candida parapsilosis causing fungaemia in South African neonatal intensive care units (NICUs). From February 2009 through to August 2010, cases of candidaemia were reported through laboratory-based surveillance. C. parapsilosis isolates from neonatal cases were submitted for identification by internal transcribed spacer (ITS) region sequencing, antifungal susceptibility testing and microsatellite genotyping. Cluster analysis was performed using Unweighted Pair Group Method with Arithmetic Mean (UPGMA). Of 1671 cases with a viable Candida isolate, 393 (24%) occurred among neonates. Isolates from 143 neonatal cases were confirmed as C. parapsilosis sensu stricto. Many isolates were resistant to fluconazole (77/143; 54%) and voriconazole (20/143; 14%). Of 79 closely-related genotypes, 18 were represented by ≥2 isolates; 61 genotypes had a single isolate each. Seven clusters, comprised of 82 isolates, were identified at five hospitals in three provinces. Isolates belonging to certain clusters were significantly more likely to be fluconazole resistant: all cluster 7 isolates and the majority of cluster 4 (78%), 5 (89%) and 6 (67%) isolates (P<.001). Candida parapsilosis-associated candidaemia in public-sector NICUs was caused by closely related genotypes and there was molecular evidence of undetected outbreaks as well as intra-hospital transmission. © 2017 Blackwell Verlag GmbH.

Incidence of Connected Consciousness after Tracheal Intubation: A Prospective, International, Multicenter Cohort Study of the Isolated Forearm Technique.

PubMed

Sanders, Robert D; Gaskell, Amy; Raz, Aeyal; Winders, Joel; Stevanovic, Ana; Rossaint, Rolf; Boncyk, Christina; Defresne, Aline; Tran, Gabriel; Tasbihgou, Seth; Meier, Sascha; Vlisides, Phillip E; Fardous, Hussein; Hess, Aaron; Bauer, Rebecca M; Absalom, Anthony; Mashour, George A; Bonhomme, Vincent; Coburn, Mark; Sleigh, Jamie

2017-02-01

The isolated forearm technique allows assessment of consciousness of the external world (connected consciousness) through a verbal command to move the hand (of a tourniquet-isolated arm) during intended general anesthesia. Previous isolated forearm technique data suggest that the incidence of connected consciousness may approach 37% after a noxious stimulus. The authors conducted an international, multicenter, pragmatic study to establish the incidence of isolated forearm technique responsiveness after intubation in routine practice. Two hundred sixty adult patients were recruited at six sites into a prospective cohort study of the isolated forearm technique after intubation. Demographic, anesthetic, and intubation data, plus postoperative questionnaires, were collected. Univariate statistics, followed by bivariate logistic regression models for age plus variable, were conducted. The incidence of isolated forearm technique responsiveness after intubation was 4.6% (12/260); 5 of 12 responders reported pain through a second hand squeeze. Responders were younger than nonresponders (39 ± 17 vs. 51 ± 16 yr old; P = 0.01) with more frequent signs of sympathetic activation (50% vs. 2.4%; P = 0.03). No participant had explicit recall of intraoperative events when questioned after surgery (n = 253). Across groups, depth of anesthesia monitoring values showed a wide range; however, values were higher for responders before (54 ± 20 vs. 42 ± 14; P = 0.02) and after (52 ± 16 vs. 43 ± 16; P = 0.02) intubation. In patients not receiving total intravenous anesthesia, exposure to volatile anesthetics before intubation reduced the odds of responding (odds ratio, 0.2 [0.1 to 0.8]; P = 0.02) after adjustment for age. Intraoperative connected consciousness occurred frequently, although the rate is up to 10-times lower than anticipated. This should be considered a conservative estimate of intraoperative connected consciousness.

Critical role of foreground stimuli in perceiving visually induced self-motion (vection).

PubMed

Nakamura, S; Shimojo, S

1999-01-01

The effects of a foreground stimulus on vection (illusory perception of self-motion induced by a moving background stimulus) were examined in two experiments. The experiments reveal that the presentation of a foreground pattern with a moving background stimulus may affect vection. The foreground stimulus facilitated vection strength when it remained stationary or moved slowly in the opposite direction to that of the background stimulus. On the other hand, there was a strong inhibition of vection when the foreground stimulus moved slowly with, or quickly against, the background. These results suggest that foreground stimuli, as well as background stimuli, play an important role in perceiving self-motion.

Relationship between inter-stimulus-intervals and intervals of autonomous activities in a neuronal network.

PubMed

Ito, Hidekatsu; Minoshima, Wataru; Kudoh, Suguru N

2015-08-01

To investigate relationships between neuronal network activity and electrical stimulus, we analyzed autonomous activity before and after electrical stimulus. Recordings of autonomous activity were performed using dissociated culture of rat hippocampal neurons on a multi-electrodes array (MEA) dish. Single stimulus and pared stimuli were applied to a cultured neuronal network. Single stimulus was applied every 1 min, and paired stimuli was performed by two sequential stimuli every 1 min. As a result, the patterns of synchronized activities of a neuronal network were changed after stimulus. Especially, long range synchronous activities were induced by paired stimuli. When 1 s inter-stimulus-intervals (ISI) and 1.5 s ISI paired stimuli are applied to a neuronal network, relatively long range synchronous activities expressed in case of 1.5 s ISI. Temporal synchronous activity of neuronal network is changed according to inter-stimulus-intervals (ISI) of electrical stimulus. In other words, dissociated neuronal network can maintain given information in temporal pattern and a certain type of an information maintenance mechanism was considered to be implemented in a semi-artificial dissociated neuronal network. The result is useful toward manipulation technology of neuronal activity in a brain system.

An isolation-enhanced quad-element antenna using suspended solid wires for LTE small-cell base stations

NASA Astrophysics Data System (ADS)

Chen, Yen-Sheng; Zhou, Huang-Cheng

2017-05-01

This paper presents a multiple-input-multiple-output (MIMO) antenna that has four-unit elements enabled by an isolation technique for long-term evolution (LTE) small-cell base stations. While earlier studies on MIMO base-station antennas cope with either a lower LTE band (698-960 MHz) or an upper LTE band (1710-2690 MHz), the proposed antenna meets the full LTE specification, yet it uses the maximum number of unit elements to increase channel capacity. The antenna configuration is optimized for good impedance matching and high radiation efficiency. In particular, as the spacing between unit elements is so small that severe mutual coupling occurs, we propose a simple structure with extremely low costs to enhance the isolation. By using suspended solid wires interconnecting the position having strong coupled current of two adjacent elements, an isolation enhancement of 37 dB is achieved. Although solid wires inherently aim at direct-current applications, this work successfully employs such a low-cost technique to microwave antenna development. Experimental results have validated the design guidelines and the proposed configuration, showing that antenna performances including impedance matching, isolation, radiation features, signal correlation, and channel capacity gain are highly desired for LTE small-cell base stations.

Observing Behavior and Atypically Restricted Stimulus Control

ERIC Educational Resources Information Center

Dube, William V.; Dickson, Chata A.; Balsamo, Lyn M.; O'Donnell, Kristin Lombard; Tomanari, Gerson Y.; Farren, Kevin M.; Wheeler, Emily E.; McIlvane, William J.

2010-01-01

Restricted stimulus control refers to discrimination learning with atypical limitations in the range of controlling stimuli or stimulus features. In the study reported here, 4 normally capable individuals and 10 individuals with intellectual disabilities (ID) performed two-sample delayed matching to sample. Sample-stimulus observing was recorded…

Outbreak of Invasive Wound Mucormycosis in a Burn Unit Due to Multiple Strains of Mucor circinelloides f. circinelloides Resolved by Whole-Genome Sequencing.

PubMed

Garcia-Hermoso, Dea; Criscuolo, Alexis; Lee, Soo Chan; Legrand, Matthieu; Chaouat, Marc; Denis, Blandine; Lafaurie, Matthieu; Rouveau, Martine; Soler, Charles; Schaal, Jean-Vivien; Mimoun, Maurice; Mebazaa, Alexandre; Heitman, Joseph; Dromer, Françoise; Brisse, Sylvain; Bretagne, Stéphane; Alanio, Alexandre

2018-04-24

Mucorales are ubiquitous environmental molds responsible for mucormycosis in diabetic, immunocompromised, and severely burned patients. Small outbreaks of invasive wound mucormycosis (IWM) have already been reported in burn units without extensive microbiological investigations. We faced an outbreak of IWM in our center and investigated the clinical isolates with whole-genome sequencing (WGS) analysis. We analyzed M. circinelloides isolates from patients in our burn unit (BU1, Hôpital Saint-Louis, Paris, France) together with nonoutbreak isolates from Burn Unit 2 (BU2, Paris area) and from France over a 2-year period (2013 to 2015). A total of 21 isolates, including 14 isolates from six BU1 patients, were analyzed by whole-genome sequencing (WGS). Phylogenetic classification based on de novo assembly and assembly free approaches showed that the clinical isolates clustered in four highly divergent clades. Clade 1 contained at least one of the strains from the six epidemiologically linked BU1 patients. The clinical isolates were specific to each patient. Two patients were infected with more than two strains from different clades, suggesting that an environmental reservoir of clonally unrelated isolates was the source of contamination. Only two patients from BU1 shared one strain, which could correspond to direct transmission or contamination with the same environmental source. In conclusion, WGS of several isolates per patients coupled with precise epidemiological data revealed a complex situation combining potential cross-transmission between patients and multiple contaminations with a heterogeneous pool of strains from a cryptic environmental reservoir. IMPORTANCE Invasive wound mucormycosis (IWM) is a severe infection due to environmental molds belonging to the order Mucorales. Severely burned patients are particularly at risk for IWM. Here, we used whole-genome sequencing (WGS) analysis to resolve an outbreak of IWM due to Mucor circinelloides that occurred in our hospital (BU1). We sequenced 21 clinical isolates, including 14 from BU1 and 7 unrelated isolates, and compared them to the reference genome (1006PhL). This analysis revealed that the outbreak was mainly due to multiple strains that seemed patient specific, suggesting that the patients were more likely infected from a pool of diverse strains from the environment rather than from direct transmission among them. This study revealed the complexity of a Mucorales outbreak in the settings of IWM in burn patients, which has been highlighted based on WGS combined with careful sampling. Copyright © 2018 Garcia-Hermoso et al.

Structural study of the exopolysaccharide produced by a clinical isolate of Burkholderia cepacia.

PubMed

Cescutti, P; Bosco, M; Picotti, F; Impallomeni, G; Leitão, J H; Richau, J A; Sá-Correia, I

2000-07-14

The primary structure of the exopolysaccharide produced by a clinical isolate of the bacterium Burkholderia cepacia was studied by means of methylation analysis, selective degradation, NMR spectroscopy, and electrospray mass spectrometry. The resulting data showed that the parent repeating unit of the exopolysaccharide is a highly branched heptasaccharide with the following structure: Two acetyl groups are present per repeating unit, as noncarbohydrate substituents. Copyright 2000 Academic Press.

Development of an Isolator System for PET Drug Compounding with Sterilization and Dispensing Units.

PubMed

Waki, Atsuo; Hashimoto, Yuuki; Suzuki, Hisashi; Mizukawa, Yousuke; Kinoshita, Toshiaki; Ichihara, Hironobu; Kaneko, Izumi; Iwakuma, Kazuko; Kawamura, Kazuki; Zhang, Ming-Rong; Fujibayashi, Yasuhisa

2016-01-01

To maintain sterility of PET drug is the most important for in-house positron emission tomography (PET) drug manufacturing, and sanitary control of the laboratory to perform aseptic procedure is the key point for the sterility of PET drugs. However, rigorous sanitary control affects both the high cost and the low efficiency. To conquer those, we developed an isolator system especially for PET drug compounding including sterilization and dispensing units. This system consists of a HEPA unit for inlet and outlet, positive regulation of the ear inside isolator, a sterilizer with vapored hydrogen peroxide and a dispenser with self-shield for radiation. We set the materials for the dispenser through gloves, and the compounding such as sterilization and dispensing PET drugs to the containers is performed automatically without radiation. High level assurance of PET drug sterility is expected to be accomplished in the PET centers of the hospitals without high level sanitary control.

Second-order schedules: discrimination of components1

PubMed Central

Squires, Nancy; Norborg, James; Fantino, Edmund

1975-01-01

Pigeons were exposed to a series of second-order schedules in which the completion of a fixed number of fixed-interval components produced food. In Experiment 1, brief (2 sec) stimulus presentations occurred as each fixed-interval component was completed. During the brief-stimulus presentation terminating the last fixed-interval component, a response was required on a second key, the brief-stimulus key, to produce food. Responses on the brief-stimulus key before the last brief-stimulus presentation had no scheduled consequences, but served as a measure of the extent to which the final component was discriminated from preceding components. Whether there were one, two, four, or eight fixed-interval components, responses on the brief-stimulus key occurred during virtually every brief-stimulus presentation. In Experiment 2, an attempt was made to punish unnecessary responses on the brief-stimulus key, i.e., responses on the brief-stimulus key that occurred before the last component. None of the pigeons learned to withhold these responses, even though they produced a 15-sec timeout and loss of primary reinforcement. In Experiment 3, different key colors were associated with each component of a second-order schedule (a chain schedule). In contrast to Experiment 1, brief-stimulus key responses were confined to the last component. It was concluded that pigeons do not discriminate well between components of second-order schedules unless a unique exteroceptive cue is provided for each component. The relative discriminability of the components may account for the observed differences in initial-component response rates between comparable brief-stimulus, tandem, and chain schedules. PMID:16811868

An arousing, musically enhanced bird song stimulus mediates circadian rhythm phase advances in dim light.

PubMed

Goel, Namni

2006-09-01

A musically enhanced bird song stimulus presented in the early subjective night phase delays human circadian rhythms. This study determined the phase-shifting effects of the same stimulus in the early subjective day. Eleven subjects (ages 18-63 yr; mean +/- SD: 28.0 +/- 16.6 yr) completed two 4-day laboratory sessions in constant dim light (<20 lux). They received two consecutive presentations of either a 2-h musically enhanced bird song or control stimulus from 0600 to 0800 on the second and third mornings while awake. The 4-day sessions employing either the stimulus or control were counterbalanced. Core body temperature (CBT) was collected throughout the study, and salivary melatonin was obtained every 30 min from 1900 to 2330 on the baseline and poststimulus/postcontrol nights. Dim light melatonin onset and CBT minimum circadian phase before and after stimulus or control presentation was assessed. The musically enhanced bird song stimulus produced significantly larger phase advances of the circadian melatonin (mean +/- SD: 0.87 +/- 0.36 vs. 0.24 +/- 0.22 h) and CBT (1.08 +/- 0.50 vs. 0.43 +/- 0.37 h) rhythms than the control. The stimulus also decreased fatigue and total mood disturbance, suggesting arousing effects. This study shows that a musically enhanced bird song stimulus presented during the early subjective day phase advances circadian rhythms. However, it remains unclear whether the phase shifts are due directly to effects of the stimulus on the clock or are arousal- or dim light-mediated effects. This nonphotic stimulus mediates circadian resynchronization in either the phase advance or delay direction.

Stimulus Equalization: Temporary Reduction of Stimulus Complexity to Facilitate Discrimination Learning.

ERIC Educational Resources Information Center

Hoko, J. Aaron; LeBlanc, Judith M.

1988-01-01

Because disabled learners may profit from procedures using gradual stimulus change, this study utilized a microcomputer to investigate the effectiveness of stimulus equalization, an error reduction procedure involving an abrupt but temporary reduction of dimensional complexity. The procedure was found to be generally effective and implications for…

Antimicrobial Susceptibility and Clonality of Clinical Ureaplasma Isolates in the United States.

PubMed

Fernández, Javier; Karau, Melissa J; Cunningham, Scott A; Greenwood-Quaintance, Kerryl E; Patel, Robin

2016-08-01

Ureaplasma urealyticum and Ureaplasma parvum are pathogens involved in urogenital tract and intrauterine infections and also in systemic diseases in newborns and immunosuppressed patients. There is limited information on the antimicrobial susceptibility and clonality of these species. In this study, we report the susceptibility of 250 contemporary isolates of Ureaplasma (202 U. parvum and 48 U. urealyticum isolates) recovered at Mayo Clinic, Rochester, MN. MICs of doxycycline, azithromycin, ciprofloxacin, tetracycline, erythromycin, and levofloxacin were determined by broth microdilution, with MICS of the last three interpreted according to CLSI guidelines. Levofloxacin resistance was found in 6.4% and 5.2% of U. parvum and U. urealyticum isolates, respectively, while 27.2% and 68.8% of isolates, respectively, showed ciprofloxacin MICs of ≥4 μg/ml. The resistance mechanism of levofloxacin-resistant isolates was due to mutations in parC, with the Ser83Leu substitution being most frequent, followed by Glu87Lys. No macrolide resistance was found among the 250 isolates studied; a single U. parvum isolate was tetracycline resistant. tet(M) was found in 10 U. parvum isolates, including the single tetracycline-resistant isolate, as well as in 9 isolates which had low tetracycline and doxycycline MICs. Multilocus sequence typing (MLST) performed on a selection of 46 isolates showed high diversity within the clinical Ureaplasma isolates studied, regardless of antimicrobial susceptibility. The present work extends previous knowledge regarding susceptibility to antimicrobial agents, resistance mechanisms, and clonality of Ureaplasma species in the United States. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

Synthesis of Bisindole Alkaloids from the Apocynaceae Which Contain a Macroline or Sarpagine Unit: A Review

PubMed Central

Rahman, Md Toufiqur; Phani Babu Tiruveedhula, Veera V. N.; Cook, James M.

2016-01-01

Bisindole natural products consist of two monomeric indole alkaloid units as their obligate constituents. Bisindoles are more potent with respect to their biological activity than their corresponding monomeric units. In addition, the synthesis of bisindoles are far more challenging than the synthesis of monomeric indole alkaloids. Herein is reviewed the enantiospecific total and partial synthesis of bisindole alkaloids isolated primarily from the Alstonia genus of the Apocynaceae family. The monomeric units belong to the sarpagine, ajmaline, macroline, vobasine, and pleiocarpamine series. An up-to-date discussion of their isolation, characterization, biological activity as well as approaches to their partial and total synthesis by means of both synthetic and biosynthetic strategies are presented. PMID:27854259

Visual attractiveness is leaky: the asymmetrical relationship between face and hair.

PubMed

Saegusa, Chihiro; Intoy, Janis; Shimojo, Shinsuke

2015-01-01

Predicting personality is crucial when communicating with people. It has been revealed that the perceived attractiveness or beauty of the face is a cue. As shown in the well-known "what is beautiful is good" stereotype, perceived attractiveness is often associated with desirable personality. Although such research on attractiveness used mainly the face isolated from other body parts, the face is not always seen in isolation in the real world. Rather, it is surrounded by one's hairstyle, and is perceived as a part of total presence. In human vision, perceptual organization/integration occurs mostly in a bottom up, task-irrelevant fashion. This raises an intriguing possibility that task-irrelevant stimulus that is perceptually integrated with a target may influence our affective evaluation. In such a case, there should be a mutual influence between attractiveness perception of the face and surrounding hair, since they are assumed to share strong and unique perceptual organization. In the current study, we examined the influence of a task-irrelevant stimulus on our attractiveness evaluation, using face and hair as stimuli. The results revealed asymmetrical influences in the evaluation of one while ignoring the other. When hair was task-irrelevant, it still affected attractiveness of the face, but only if the hair itself had never been evaluated by the same evaluator. On the other hand, the face affected the hair regardless of whether the face itself was evaluated before. This has intriguing implications on the asymmetry between face and hair, and perceptual integration between them in general. Together with data from a post hoc questionnaire, it is suggested that both implicit non-selective and explicit selective processes contribute to attractiveness evaluation. The findings provide an understanding of attractiveness perception in real-life situations, as well as a new paradigm to reveal unknown implicit aspects of information integration for emotional judgment.

Visual attractiveness is leaky: the asymmetrical relationship between face and hair

PubMed Central

Saegusa, Chihiro; Intoy, Janis; Shimojo, Shinsuke

2015-01-01

Predicting personality is crucial when communicating with people. It has been revealed that the perceived attractiveness or beauty of the face is a cue. As shown in the well-known “what is beautiful is good” stereotype, perceived attractiveness is often associated with desirable personality. Although such research on attractiveness used mainly the face isolated from other body parts, the face is not always seen in isolation in the real world. Rather, it is surrounded by one’s hairstyle, and is perceived as a part of total presence. In human vision, perceptual organization/integration occurs mostly in a bottom up, task-irrelevant fashion. This raises an intriguing possibility that task-irrelevant stimulus that is perceptually integrated with a target may influence our affective evaluation. In such a case, there should be a mutual influence between attractiveness perception of the face and surrounding hair, since they are assumed to share strong and unique perceptual organization. In the current study, we examined the influence of a task-irrelevant stimulus on our attractiveness evaluation, using face and hair as stimuli. The results revealed asymmetrical influences in the evaluation of one while ignoring the other. When hair was task-irrelevant, it still affected attractiveness of the face, but only if the hair itself had never been evaluated by the same evaluator. On the other hand, the face affected the hair regardless of whether the face itself was evaluated before. This has intriguing implications on the asymmetry between face and hair, and perceptual integration between them in general. Together with data from a post hoc questionnaire, it is suggested that both implicit non-selective and explicit selective processes contribute to attractiveness evaluation. The findings provide an understanding of attractiveness perception in real-life situations, as well as a new paradigm to reveal unknown implicit aspects of information integration for emotional judgment. PMID:25914656

Differences in virulence and sporulation of Phytophthora kernoviae isolates originating from two distinct geographical regions

USDA-ARS?s Scientific Manuscript database

Phytophthora kernoviae has only been isolated from the United Kingdom (U.K.) and New Zealand. To understand what differences may exist between isolates from these two distinct geographical regions, virulence studies on three host plants and sporulation on host leaves were conducted on select isolat...

Adverse Impact of Racial Isolation on Student Performance: A Study in North Carolina

ERIC Educational Resources Information Center

Sharma, Andy; Joyner, Ann Moss; Osment, Ashley

2014-01-01

This study examines the impact of racial isolation on high school student performance in North Carolina, a state in the southeast United States. Our research goal is to investigate if increased isolation negatively impacts Black students' academic performance. Employing the North Carolina State Department of Public Instruction (NCDPI) dataset, we…

Antimicrobial resistance of Salmonella enterica isolates from bulk tank milk and milk filters in the United States

USDA-ARS?s Scientific Manuscript database

Non-typhoid Salmonella is frequently associated with dairy cattle and their environment. Despite well-developed milking hygiene protocols, fecal contamination can occur and Salmonella has often been isolated from bulk milk. Salmonella isolates were recovered from US bulk tank milk as part of the NAH...

Vibration sensory thresholds depend on pressure of applied stimulus.

PubMed

Lowenthal, L M; Hockaday, T D

1987-01-01

Vibration sensory thresholds (VSTs) were estimated in 40 healthy subjects and 8 with diabetic peripheral neuropathy. A vibrameter and a biothesiometer were used at four sites and at differing pressures. In normal subjects, with the vibrameter at 200 g, mean VST +/- SE for all sites was 1.87 micron +/- 0.22 and at 400 g dropped to 1.08 micron +/- 0.15 (P less than .0001). In 20 of these subjects with a biothesiometer at 200 and 400 g, mean VST fell from 12.8 +/- 1.5 to 11.1 +/- 1.1 (arbitrary units) (P = .01) when the greater pressure was applied. In the 8 subjects with peripheral neuropathy, with the vibrameter at 200 and 400 g, respectively, mean VST fell from 70.7 +/- 26 to 7.2 +/- 1.8. VST in these subjects was estimated again after 1 mo and showed strong correlations with the previous values. Biothesiometer results correlated with vibrameter results at all sites. Thus, VST decreases as the pressure of the applied stimulus is increased and this effect appears to be more marked in peripheral neuropathy. This has important consequences in monitoring this condition.

A dual-process perspective on fluency-based aesthetics: the pleasure-interest model of aesthetic liking.

PubMed

Graf, Laura K M; Landwehr, Jan R

2015-11-01

In this article, we develop an account of how aesthetic preferences can be formed as a result of two hierarchical, fluency-based processes. Our model suggests that processing performed immediately upon encountering an aesthetic object is stimulus driven, and aesthetic preferences that accrue from this processing reflect aesthetic evaluations of pleasure or displeasure. When sufficient processing motivation is provided by a perceiver's need for cognitive enrichment and/or the stimulus' processing affordance, elaborate perceiver-driven processing can emerge, which gives rise to fluency-based aesthetic evaluations of interest, boredom, or confusion. Because the positive outcomes in our model are pleasure and interest, we call it the Pleasure-Interest Model of Aesthetic Liking (PIA Model). Theoretically, this model integrates a dual-process perspective and ideas from lay epistemology into processing fluency theory, and it provides a parsimonious framework to embed and unite a wealth of aesthetic phenomena, including contradictory preference patterns for easy versus difficult-to-process aesthetic stimuli. © 2015 by the Society for Personality and Social Psychology, Inc.

Dynamic binding of visual features by neuronal/stimulus synchrony.

PubMed

Iwabuchi, A

1998-05-01

When people see a visual scene, certain parts of the visual scene are treated as belonging together and we regard them as a perceptual unit, which is called a "figure". People focus on figures, and the remaining parts of the scene are disregarded as "ground". In Gestalt psychology this process is called "figure-ground segregation". According to current perceptual psychology, a figure is formed by binding various visual features in a scene, and developments in neuroscience have revealed that there are many feature-encoding neurons, which respond to such features specifically. It is not known, however, how the brain binds different features of an object into a coherent visual object representation. Recently, the theory of binding by neuronal synchrony, which argues that feature binding is dynamically mediated by neuronal synchrony of feature-encoding neurons, has been proposed. This review article portrays the problem of figure-ground segregation and features binding, summarizes neurophysiological and psychophysical experiments and theory relevant to feature binding by neuronal/stimulus synchrony, and suggests possible directions for future research on this topic.

Isolation and characterisation of the biological repeating unit of cepacian, the exopolysaccharide produced by bacteria of the Burkholderia cepacia complex.

PubMed

Cescutti, Paola; Foschiatti, Michela; Furlanis, Linda; Lagatolla, Cristina; Rizzo, Roberto

2010-07-02

The repeating unit of cepacian, the exopolysaccharide produced by the majority of the microorganisms belonging to the Burkholderia cepacia complex, was isolated from inner bacterial membranes and investigated by mass spectrometry, with and without prior derivatisation. Interpretation of the mass spectra led to the determination of the biological repeating unit primary structure, thus disclosing the nature of the oligosaccharide produced in vivo. Moreover, mass spectra recorded on the native sample revealed that acetyl substitution was very variable, producing a mixture of repeating units containing zero to four acyl groups. At the same time, finding acetylated oligosaccharides showed that binding of these substituents occurred in the cellular periplasmic space, before the polymerisation process took place. In the chromatographic peak containing the repeating unit, oligosaccharides shorter than the repeating unit co-eluted. Mass spectrometric analysis showed that they were biosynthetic intermediates of the repeating unit and further investigation revealed the biosynthetic sequence of cepacian building block. Copyright 2010 Elsevier Ltd. All rights reserved.

Stimulus size dependence of hue changes induced by chromatic surrounds.

PubMed

Kellner, Christian Johannes; Wachtler, Thomas

2016-03-01

A chromatic surround induces a change in the perceived hue of a stimulus. This shift in hue depends on the chromatic difference between the stimulus and the surround. We investigated how chromatic induction varies with stimulus size and whether the size dependence depends on the surround hue. Subjects performed asymmetric matching of color stimuli with different sizes in surrounds of different chromaticities. Generally, induced hue shifts decreased with increasing stimulus size. This decrease was quantitatively different for different surround hues. However, when size effects were normalized to an overall induction strength, the chromatic specificity was largely reduced. The separability of inducer chromaticity and stimulus size suggests that these effects are mediated by different neural mechanisms.

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

Fox, J.W.; Elzinga, M.; Tu, A.T.

The primary structure of myotoxin a, a myotoxin protein from the venom of the North American rattlesnake Crotalus viridis viridis, was determined and the position of the disulfide bonds assigned. The toxin was isolated, carboxymethylated, and cleaved by cyanogen bromide, and the resultant peptides were isolated. The cyanogen bromide peptides were subjected to amino acid sequence analysis. In order to assign the positions of the three disulfide bonds, the native toxin was cleaved sequentially with cyanogen bromide and trypsin. A two peptide unit connected by one disulfide bond was isolated and characterized, and a three-peptide unit connected by two disulfidemore » bonds was isolated. One peptide in the three-peptide unit was identified as Cys-Cys-Lys. In order to establish the linkages between the peptides and Cys-Cys-Lys, one cycle of Edman degradation was carried out such that the Cys-Cys bond was cleaved. Upon isolation and analysis of the cleavage products, the disulfide bonds connecting the three peptides were determined. The positions of the disulfide bridges of myotoxin a were determined to be totally different from those of neurotoxins isolated from snake venoms. The sequence of myotoxin a was compared with the sequences of other snake venom toxins using the computer program RELATE to determine whether myotoxin a is similar to any other types of toxins. From the computer analysis, myotoxin a did not show any close relationship to other toxins except crotamine from the South American rattlesnake Crotalus durissus terrificus.« less

Population Structure of Listeria monocytogenes Serotype 4b Isolates from Sporadic Human Listeriosis Cases in the United States from 2003 to 2008

PubMed Central

Ward, Todd J.; Graves, Lewis M.; Tarr, Cheryl L.; Siletzky, Robin M.; Kathariou, Sophia

2014-01-01

Listeria monocytogenes can cause severe food-borne disease (listeriosis). Numerous outbreaks have involved three serotype 4b epidemic clones (ECs): ECI, ECII, and ECIa. However, little is known about the population structure of L. monocytogenes serotype 4b from sporadic listeriosis in the United States, even though most cases of human listeriosis are in fact sporadic. Here we analyzed 136 serotype 4b isolates from sporadic cases in the United States, 2003 to 2008, utilizing multiple tools including multilocus genotyping, pulsed-field gel electrophoresis, and sequence analysis of the inlAB locus. ECI, ECII, and ECIa were frequently encountered (32, 17, and 7%, respectively). However, annually 30 to 68% of isolates were outside these ECs, and several novel clonal groups were identified. An estimated 33 and 17% of the isolates, mostly among the ECs, were resistant to cadmium and arsenic, respectively, but resistance to benzalkonium chloride was uncommon (3%) among the sporadic isolates. The frequency of clonal groups fluctuated within the 6-year study period, without consistent trends. However, on several occasions, temporal clusters of isolates with indistinguishable genotypes were detected, suggesting the possibility of hidden multistate outbreaks. Our analysis suggests a complex population structure of serotype 4b L. monocytogenes from sporadic disease, with important contributions by ECs and several novel clonal groups. Continuous monitoring will be needed to assess long-term trends in clonality patterns and population structure of L. monocytogenes from sporadic listeriosis. PMID:24705322

Population structure of Listeria monocytogenes serotype 4b isolates from sporadic human listeriosis cases in the United States from 2003 to 2008.

PubMed

Lee, Sangmi; Ward, Todd J; Graves, Lewis M; Tarr, Cheryl L; Siletzky, Robin M; Kathariou, Sophia

2014-06-01

Listeria monocytogenes can cause severe food-borne disease (listeriosis). Numerous outbreaks have involved three serotype 4b epidemic clones (ECs): ECI, ECII, and ECIa. However, little is known about the population structure of L. monocytogenes serotype 4b from sporadic listeriosis in the United States, even though most cases of human listeriosis are in fact sporadic. Here we analyzed 136 serotype 4b isolates from sporadic cases in the United States, 2003 to 2008, utilizing multiple tools including multilocus genotyping, pulsed-field gel electrophoresis, and sequence analysis of the inlAB locus. ECI, ECII, and ECIa were frequently encountered (32, 17, and 7%, respectively). However, annually 30 to 68% of isolates were outside these ECs, and several novel clonal groups were identified. An estimated 33 and 17% of the isolates, mostly among the ECs, were resistant to cadmium and arsenic, respectively, but resistance to benzalkonium chloride was uncommon (3%) among the sporadic isolates. The frequency of clonal groups fluctuated within the 6-year study period, without consistent trends. However, on several occasions, temporal clusters of isolates with indistinguishable genotypes were detected, suggesting the possibility of hidden multistate outbreaks. Our analysis suggests a complex population structure of serotype 4b L. monocytogenes from sporadic disease, with important contributions by ECs and several novel clonal groups. Continuous monitoring will be needed to assess long-term trends in clonality patterns and population structure of L. monocytogenes from sporadic listeriosis.

Genetic diversity of clinical Mycobacterium avium subsp. hominissuis and Mycobacterium intracellulare isolates causing pulmonary diseases recovered from different geographical regions.

PubMed

Ichikawa, Kazuya; van Ingen, Jakko; Koh, Won-Jung; Wagner, Dirk; Salfinger, Max; Inagaki, Takayuki; Uchiya, Kei-Ichi; Nakagawa, Taku; Ogawa, Kenji; Yamada, Kiyofumi; Yagi, Tetsuya

2015-12-01

Mycobacterium avium complex (MAC) infections are increasing annually in many countries. MAC strains are the most common nontuberculous mycobacterial pathogens isolated from respiratory samples and predominantly consist of two species, Mycobacterium avium and Mycobacterium intracellulare. The aim of this study was to analyze the molecular epidemiology and genetic backgrounds of clinical MAC isolates collected from The Netherlands, Germany, United States, Korea and Japan. Variable numbers of tandem repeats (VNTR) analysis was used to examine the genetic relatedness of clinical isolates of M. avium subsp. hominissuis (n=261) and M. intracellulare (n=116). Minimum spanning tree and unweighted pair group method using arithmetic averages analyses based on the VNTR data indicated that M. avium subsp. hominissuis isolates from Japan shared a high degree of genetic relatedness with Korean isolates, but not with isolates from Europe or the United States, whereas M. intracellulare isolates did not show any specific clustering by geographic origin. The findings from the present study indicate that strains of M. avium subsp. hominissuis, but not M. intracellulare, exhibit geographical differences in genetic diversity and imply that MAC strains may have different sources, routes of transmission and perhaps clinical manifestations. Copyright © 2015 Elsevier B.V. All rights reserved.

Cardiovascular collapse after labetalol for hypertensive crisis in an undiagnosed pheochromocytoma during cesarean section.

PubMed

Kuok, Chi-Hang; Yen, Chia-Rong; Huang, Chong-Sin; Ko, Yuan-Pi; Tsai, Pei-Shan

2011-06-01

Pheochromocytoma is a catecholamine-producing tumor but rarely delayingly diagnosed until during pregnancy. We reported a pregnant woman who underwent emergent cesarean section because of intrauterine growth retardation, oligohydramnios, and hypertension. The existence of an undiagnosed pheochromocytoma was suspected by the unusual hemodynamic response to spinal anesthesia, abdominal compressions, and operative stimulus. Hypertensive crisis occurred during the operation and she was sent to the intensive care unit for postoperative care. In the intensive care unit, cardiovascular collapse occurred after nonselective β-adrenergic blockade. Unexpected hypertensive crisis during the perioperative period should alert clinicians to the possibility of a pheochromocytoma. For the treatment of choice, nonselective β-adrenergic blockade should not be used before the α-blockade. Copyright © 2011. Published by Elsevier B.V.

The influence of spontaneous activity on stimulus processing in primary visual cortex.

PubMed

Schölvinck, M L; Friston, K J; Rees, G

2012-02-01

Spontaneous activity in the resting human brain has been studied extensively; however, how such activity affects the local processing of a sensory stimulus is relatively unknown. Here, we examined the impact of spontaneous activity in primary visual cortex on neuronal and behavioural responses to a simple visual stimulus, using functional MRI. Stimulus-evoked responses remained essentially unchanged by spontaneous fluctuations, combining with them in a largely linear fashion (i.e., with little evidence for an interaction). However, interactions between spontaneous fluctuations and stimulus-evoked responses were evident behaviourally; high levels of spontaneous activity tended to be associated with increased stimulus detection at perceptual threshold. Our results extend those found in studies of spontaneous fluctuations in motor cortex and higher order visual areas, and suggest a fundamental role for spontaneous activity in stimulus processing. Copyright © 2011. Published by Elsevier Inc.

Discriminative stimuli that follow the absence of reinforcement are preferred by pigeons over those that follow reinforcement.

PubMed

Friedrich, Andrea M; Clement, Tricia S; Zentall, Thomas R

2005-08-01

Clement, Feltus, Kaiser, and Zentall (2000) found that when pigeons have to work to obtain a discriminative stimulus that is followed by reinforcement, they prefer a discriminative stimulus that requires greater effort over one that requires less effort. The authors suggested that such a preference results from the greater change in hedonic value that occurs between the more aversive event and the onset of the stimulus that signals reinforcement, a contrast effect. It was hypothesized that any stimulus that follows a relatively more aversive event would be preferred over a stimulus that follows a relatively less aversive event. In the present experiment, the authors tested the counterintuitive prediction of that theory, that pigeons should prefer a discriminative stimulus that follows the absence of reinforcement over a discriminative stimulus that follows reinforcement. Results supported the theory.

Dissociating Stimulus-Set and Response-Set in the Context of Task-Set Switching

PubMed Central

Kieffaber, Paul D.; Kruschke, John K.; Cho, Raymond Y.; Walker, Philip M.; Hetrick, William P.

2014-01-01

The primary aim of the present research was to determine how stimulus-set and response-set components of task-set contribute to switch costs and conflict processing. Three experiments are described wherein participants completed an explicitly cued task-switching procedure. Experiment 1 established that task switches requiring a reconfiguration of both stimulus- and response-set incurred larger residual switch costs than task switches requiring the reconfiguration of stimulus-set alone. Between-task interference was also drastically reduced for response-set conflict compared with stimulus-set conflict. A second experiment replicated these findings and demonstrated that stimulus- and response-conflict have dissociable effects on the “decision time” and “motor time” components of total response time. Finally, a third experiment replicated Experiment 2 and demonstrated that the stimulus- and response- components of task switching and conflict processing elicit dissociable neural activity as evidence by event-related brain potentials. PMID:22984990

The perception of regularity in an isochronous stimulus in zebra finches (Taeniopygia guttata) and humans.

PubMed

van der Aa, Jeroen; Honing, Henkjan; ten Cate, Carel

2015-06-01

Perceiving temporal regularity in an auditory stimulus is considered one of the basic features of musicality. Here we examine whether zebra finches can detect regularity in an isochronous stimulus. Using a go/no go paradigm we show that zebra finches are able to distinguish between an isochronous and an irregular stimulus. However, when the tempo of the isochronous stimulus is changed, it is no longer treated as similar to the training stimulus. Training with three isochronous and three irregular stimuli did not result in improvement of the generalization. In contrast, humans, exposed to the same stimuli, readily generalized across tempo changes. Our results suggest that zebra finches distinguish the different stimuli by learning specific local temporal features of each individual stimulus rather than attending to the global structure of the stimuli, i.e., to the temporal regularity. Copyright © 2015 Elsevier B.V. All rights reserved.