Axonal Conduction Delays, Brain State, and Corticogeniculate Communication

PubMed Central

2017-01-01

Thalamocortical conduction times are short, but layer 6 corticothalamic axons display an enormous range of conduction times, some exceeding 40–50 ms. Here, we investigate (1) how axonal conduction times of corticogeniculate (CG) neurons are related to the visual information conveyed to the thalamus, and (2) how alert versus nonalert awake brain states affect visual processing across the spectrum of CG conduction times. In awake female Dutch-Belted rabbits, we found 58% of CG neurons to be visually responsive, and 42% to be unresponsive. All responsive CG neurons had simple, orientation-selective receptive fields, and generated sustained responses to stationary stimuli. CG axonal conduction times were strongly related to modulated firing rates (F1 values) generated by drifting grating stimuli, and their associated interspike interval distributions, suggesting a continuum of visual responsiveness spanning the spectrum of axonal conduction times. CG conduction times were also significantly related to visual response latency, contrast sensitivity (C-50 values), directional selectivity, and optimal stimulus velocity. Increasing alertness did not cause visually unresponsive CG neurons to become responsive and did not change the response linearity (F1/F0 ratios) of visually responsive CG neurons. However, for visually responsive CG neurons, increased alertness nearly doubled the modulated response amplitude to optimal visual stimulation (F1 values), significantly shortened response latency, and dramatically increased response reliability. These effects of alertness were uniform across the broad spectrum of CG axonal conduction times. SIGNIFICANCE STATEMENT Corticothalamic neurons of layer 6 send a dense feedback projection to thalamic nuclei that provide input to sensory neocortex. While sensory information reaches the cortex after brief thalamocortical axonal delays, corticothalamic axons can exhibit conduction delays of <2 ms to 40–50 ms. Here, in the corticogeniculate visual system of awake rabbits, we investigate the functional significance of this axonal diversity, and the effects of shifting alert/nonalert brain states on corticogeniculate processing. We show that axonal conduction times are strongly related to multiple visual response properties, suggesting a continuum of visual responsiveness spanning the spectrum of corticogeniculate axonal conduction times. We also show that transitions between awake brain states powerfully affect corticogeniculate processing, in some ways more strongly than in layer 4. PMID:28559382

The Comparison of Visual Working Memory Representations with Perceptual Inputs

PubMed Central

Hyun, Joo-seok; Woodman, Geoffrey F.; Vogel, Edward K.; Hollingworth, Andrew

2008-01-01

The human visual system can notice differences between memories of previous visual inputs and perceptions of new visual inputs, but the comparison process that detects these differences has not been well characterized. This study tests the hypothesis that differences between the memory of a stimulus array and the perception of a new array are detected in a manner that is analogous to the detection of simple features in visual search tasks. That is, just as the presence of a task-relevant feature in visual search can be detected in parallel, triggering a rapid shift of attention to the object containing the feature, the presence of a memory-percept difference along a task-relevant dimension can be detected in parallel, triggering a rapid shift of attention to the changed object. Supporting evidence was obtained in a series of experiments that examined manual reaction times, saccadic reaction times, and event-related potential latencies. However, these experiments also demonstrated that a slow, limited-capacity process must occur before the observer can make a manual change-detection response. PMID:19653755

A convergent and essential interneuron pathway for Mauthner-cell-mediated escapes.

PubMed

Lacoste, Alix M B; Schoppik, David; Robson, Drew N; Haesemeyer, Martin; Portugues, Ruben; Li, Jennifer M; Randlett, Owen; Wee, Caroline L; Engert, Florian; Schier, Alexander F

2015-06-01

The Mauthner cell (M-cell) is a command-like neuron in teleost fish whose firing in response to aversive stimuli is correlated with short-latency escapes [1-3]. M-cells have been proposed as evolutionary ancestors of startle response neurons of the mammalian reticular formation [4], and studies of this circuit have uncovered important principles in neurobiology that generalize to more complex vertebrate models [3]. The main excitatory input was thought to originate from multisensory afferents synapsing directly onto the M-cell dendrites [3]. Here, we describe an additional, convergent pathway that is essential for the M-cell-mediated startle behavior in larval zebrafish. It is composed of excitatory interneurons called spiral fiber neurons, which project to the M-cell axon hillock. By in vivo calcium imaging, we found that spiral fiber neurons are active in response to aversive stimuli capable of eliciting escapes. Like M-cell ablations, bilateral ablations of spiral fiber neurons largely eliminate short-latency escapes. Unilateral spiral fiber neuron ablations shift the directionality of escapes and indicate that spiral fiber neurons excite the M-cell in a lateralized manner. Their optogenetic activation increases the probability of short-latency escapes, supporting the notion that spiral fiber neurons help activate M-cell-mediated startle behavior. These results reveal that spiral fiber neurons are essential for the function of the M-cell in response to sensory cues and suggest that convergent excitatory inputs that differ in their input location and timing ensure reliable activation of the M-cell, a feedforward excitatory motif that may extend to other neural circuits. Copyright © 2015 Elsevier Ltd. All rights reserved.

Laterodorsal nucleus of the thalamus: A processor of somatosensory inputs.

PubMed

Bezdudnaya, Tatiana; Keller, Asaf

2008-04-20

The laterodorsal (LD) nucleus of the thalamus has been considered a "higher order" nucleus that provides inputs to limbic cortical areas. Although its functions are largely unknown, it is often considered to be involved in spatial learning and memory. Here we provide evidence that LD is part of a hitherto unknown pathway for processing somatosensory information. Juxtacellular and extracellular recordings from LD neurons reveal that they respond to vibrissa stimulation with short latency (median = 7 ms) and large magnitude responses (median = 1.2 spikes/stimulus). Most neurons (62%) had large receptive fields, responding to six and more individual vibrissae. Electrical stimulation of the trigeminal nucleus interpolaris (SpVi) evoked short latency responses (median = 3.8 ms) in vibrissa-responsive LD neurons. Labeling produced by anterograde and retrograde neuroanatomical tracers confirmed that LD neurons receive direct inputs from SpVi. Electrophysiological and neuroanatomical analyses revealed also that LD projects upon the cingulate and retrosplenial cortex, but has only sparse projections to the barrel cortex. These findings suggest that LD is part of a novel processing stream involved in spatial orientation and learning related to somatosensory cues. (c) 2008 Wiley-Liss, Inc.

Inter-individual variation in reciprocal Ia inhibition is dependent on the descending volleys delivered from corticospinal neurons to Ia interneurons.

PubMed

Kubota, Shinji; Uehara, Kazumasa; Morishita, Takuya; Hirano, Masato; Funase, Kozo

2014-02-01

We investigated the extent to which the corticospinal inputs delivered to Ia inhibitory interneurons influence the strength of disynaptic reciprocal Ia inhibition. Seventeen healthy subjects participated in this study. The degree of reciprocal Ia inhibition was determined via short-latency (condition-test interval: 1-3ms) suppression of Sol H-reflex by conditioning stimulation of common peroneal nerve. The effect of corticospinal descending inputs on Ia inhibitory interneurons was assessed by evaluating the conditioning effect of transcranial magnetic stimulation (TMS) on the Sol H-reflex. Then, we determined the relationship between the degree of reciprocal Ia inhibition and the conditioning effect of TMS on the Sol H-reflex. We found that the degree of reciprocal Ia inhibition and the extent of change in the amplitude of the TMS-conditioned H-reflex, which was measured from short latency facilitation to inhibition, displayed a strong correlation (r=0.76, p<0.01) in the resting conditions. The extent of reciprocal Ia inhibition is affected by the corticospinal descending inputs delivered to Ia inhibitory interneurons, which might explain the inter-individual variations in reciprocal Ia inhibition. Copyright © 2013 Elsevier Ltd. All rights reserved.

Descending pathways controlling visually guided updating of reaching in cats.

PubMed

Pettersson, L-G; Perfiliev, S

2002-10-01

This study uses a previously described paradigm (Pettersson et al., 1997) to investigate the ability of cats to change the direction of ongoing reaching when the target is shifted sideways; the effect on the switching latency of spinal cord lesions was investigated. Large ventral lesions transecting the ventral funicle and the ventral half of the lateral funicle gave a 20-30 ms latency prolongation of switching in the medial (right) direction, but less prolongation of switching directed laterally (left), and in one cat the latencies of switching directed laterally were unchanged. It may be inferred that the command for switching in the lateral direction can be mediated by the dorsally located cortico- and rubrospinal tracts whereas the command for short-latency switching in the medial direction is mediated by ventral pathways. A restricted ventral lesion transecting the tectospinal pathway did not change the switching latency. Comparison of different ventral lesions revealed prolongation of the latency if the lesion included a region extending dorsally along the ventral horn and from there ventrally as a vertical strip, so it may be postulated that the command for fast switching, directed medially, is mediated by a reticulospinal pathway within this location. A hypothesis is forwarded suggesting that the visual control is exerted via ponto-cerebellar pathways.

How Is the Serial Order of a Visual Sequence Represented? Insights from Transposition Latencies

ERIC Educational Resources Information Center

Hurlstone, Mark J.; Hitch, Graham J.

2018-01-01

A central goal of research on short-term memory (STM) over the past 2 decades has been to identify the mechanisms that underpin the representation of serial order, and to establish whether these mechanisms are the same across different modalities and domains (e.g., verbal, visual, spatial). A fruitful approach to addressing this question has…

Response-dependent dynamics of cell-specific inhibition in cortical networks in vivo

PubMed Central

El-Boustani, Sami; Sur, Mriganka

2014-01-01

In the visual cortex, inhibitory neurons alter the computations performed by target cells via combination of two fundamental operations, division and subtraction. The origins of these operations have been variously ascribed to differences in neuron classes, synapse location or receptor conductances. Here, by utilizing specific visual stimuli and single optogenetic probe pulses, we show that the function of parvalbumin-expressing and somatostatin-expressing neurons in mice in vivo is governed by the overlap of response timing between these neurons and their targets. In particular, somatostatin-expressing neurons respond at longer latencies to small visual stimuli compared with their target neurons and provide subtractive inhibition. With large visual stimuli, however, they respond at short latencies coincident with their target cells and switch to provide divisive inhibition. These results indicate that inhibition mediated by these neurons is a dynamic property of cortical circuits rather than an immutable property of neuronal classes. PMID:25504329

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.

Axonal Conduction Delays, Brain State, and Corticogeniculate Communication.

PubMed

Stoelzel, Carl R; Bereshpolova, Yulia; Alonso, Jose-Manuel; Swadlow, Harvey A

2017-06-28

Thalamocortical conduction times are short, but layer 6 corticothalamic axons display an enormous range of conduction times, some exceeding 40-50 ms. Here, we investigate (1) how axonal conduction times of corticogeniculate (CG) neurons are related to the visual information conveyed to the thalamus, and (2) how alert versus nonalert awake brain states affect visual processing across the spectrum of CG conduction times. In awake female Dutch-Belted rabbits, we found 58% of CG neurons to be visually responsive, and 42% to be unresponsive. All responsive CG neurons had simple, orientation-selective receptive fields, and generated sustained responses to stationary stimuli. CG axonal conduction times were strongly related to modulated firing rates (F1 values) generated by drifting grating stimuli, and their associated interspike interval distributions, suggesting a continuum of visual responsiveness spanning the spectrum of axonal conduction times. CG conduction times were also significantly related to visual response latency, contrast sensitivity (C-50 values), directional selectivity, and optimal stimulus velocity. Increasing alertness did not cause visually unresponsive CG neurons to become responsive and did not change the response linearity (F1/F0 ratios) of visually responsive CG neurons. However, for visually responsive CG neurons, increased alertness nearly doubled the modulated response amplitude to optimal visual stimulation (F1 values), significantly shortened response latency, and dramatically increased response reliability. These effects of alertness were uniform across the broad spectrum of CG axonal conduction times. SIGNIFICANCE STATEMENT Corticothalamic neurons of layer 6 send a dense feedback projection to thalamic nuclei that provide input to sensory neocortex. While sensory information reaches the cortex after brief thalamocortical axonal delays, corticothalamic axons can exhibit conduction delays of <2 ms to 40-50 ms. Here, in the corticogeniculate visual system of awake rabbits, we investigate the functional significance of this axonal diversity, and the effects of shifting alert/nonalert brain states on corticogeniculate processing. We show that axonal conduction times are strongly related to multiple visual response properties, suggesting a continuum of visual responsiveness spanning the spectrum of corticogeniculate axonal conduction times. We also show that transitions between awake brain states powerfully affect corticogeniculate processing, in some ways more strongly than in layer 4. Copyright © 2017 the authors 0270-6474/17/376342-17$15.00/0.

Visual field asymmetries in visual evoked responses

PubMed Central

Hagler, Donald J.

2014-01-01

Behavioral responses to visual stimuli exhibit visual field asymmetries, but cortical folding and the close proximity of visual cortical areas make electrophysiological comparisons between different stimulus locations problematic. Retinotopy-constrained source estimation (RCSE) uses distributed dipole models simultaneously constrained by multiple stimulus locations to provide separation between individual visual areas that is not possible with conventional source estimation methods. Magnetoencephalography and RCSE were used to estimate time courses of activity in V1, V2, V3, and V3A. Responses to left and right hemifield stimuli were not significantly different. Peak latencies for peripheral stimuli were significantly shorter than those for perifoveal stimuli in V1, V2, and V3A, likely related to the greater proportion of magnocellular input to V1 in the periphery. Consistent with previous results, sensor magnitudes for lower field stimuli were about twice as large as for upper field, which is only partially explained by the proximity to sensors for lower field cortical sources in V1, V2, and V3. V3A exhibited both latency and amplitude differences for upper and lower field responses. There were no differences for V3, consistent with previous suggestions that dorsal and ventral V3 are two halves of a single visual area, rather than distinct areas V3 and VP. PMID:25527151

Inhibition to excitation ratio regulates visual system responses and behavior in vivo.

PubMed

Shen, Wanhua; McKeown, Caroline R; Demas, James A; Cline, Hollis T

2011-11-01

The balance of inhibitory to excitatory (I/E) synaptic inputs is thought to control information processing and behavioral output of the central nervous system. We sought to test the effects of the decreased or increased I/E ratio on visual circuit function and visually guided behavior in Xenopus tadpoles. We selectively decreased inhibitory synaptic transmission in optic tectal neurons by knocking down the γ2 subunit of the GABA(A) receptors (GABA(A)R) using antisense morpholino oligonucleotides or by expressing a peptide corresponding to an intracellular loop of the γ2 subunit, called ICL, which interferes with anchoring GABA(A)R at synapses. Recordings of miniature inhibitory postsynaptic currents (mIPSCs) and miniature excitatory PSCs (mEPSCs) showed that these treatments decreased the frequency of mIPSCs compared with control tectal neurons without affecting mEPSC frequency, resulting in an ∼50% decrease in the ratio of I/E synaptic input. ICL expression and γ2-subunit knockdown also decreased the ratio of optic nerve-evoked synaptic I/E responses. We recorded visually evoked responses from optic tectal neurons, in which the synaptic I/E ratio was decreased. Decreasing the synaptic I/E ratio in tectal neurons increased the variance of first spike latency in response to full-field visual stimulation, increased recurrent activity in the tectal circuit, enlarged spatial receptive fields, and lengthened the temporal integration window. We used the benzodiazepine, diazepam (DZ), to increase inhibitory synaptic activity. DZ increased optic nerve-evoked inhibitory transmission but did not affect evoked excitatory currents, resulting in an increase in the I/E ratio of ∼30%. Increasing the I/E ratio with DZ decreased the variance of first spike latency, decreased spatial receptive field size, and lengthened temporal receptive fields. Sequential recordings of spikes and excitatory and inhibitory synaptic inputs to the same visual stimuli demonstrated that decreasing or increasing the I/E ratio disrupted input/output relations. We assessed the effect of an altered I/E ratio on a visually guided behavior that requires the optic tectum. Increasing and decreasing I/E in tectal neurons blocked the tectally mediated visual avoidance behavior. Because ICL expression, γ2-subunit knockdown, and DZ did not directly affect excitatory synaptic transmission, we interpret the results of our study as evidence that partially decreasing or increasing the ratio of I/E disrupts several measures of visual system information processing and visually guided behavior in an intact vertebrate.

Tectonigral Projections in the Primate: A Pathway for Pre-Attentive Sensory Input to Midbrain Dopaminergic Neurons

PubMed Central

May, Paul J.; McHaffie, John G.; Stanford, Terrence R.; Jiang, Huai; Costello, M. Gabriela; Coizet, Veronique; Hayes, Lauren M.; Haber, Suzanne N.; Redgrave, Peter

2010-01-01

Much of the evidence linking the short-latency phasic signaling of midbrain dopaminergic neurons with reward-prediction errors used in learning and habit formation comes from recording the visual responses of monkey dopaminergic neurons. However, the information encoded by dopaminergic neuron activity is constrained by the qualities of the afferent visual signals made available to these cells. Recent evidence from rats and cats indicates the primary source of this visual input originates subcortically, via a direct tectonigral projection. The present anatomical study sought to establish whether a direct tectonigral projection is a significant feature of the primate brain. Injections of anterograde tracers into the superior colliculus of macaque monkeys labelled terminal arbors throughout the substantia nigra, with the densest terminations in the dorsal tier. Labelled boutons were found in close association (possibly indicative of synaptic contact) with ventral midbrain neurons staining positively for the dopaminergic marker tyrosine hydroxylase. Injections of retrograde tracer confined to the macaque substantia nigra retrogradely labelled small to medium sized neurons in the intermediate and deep layers of the superior colliculus. Together, these data indicate that a direct tectonigral projection is also a feature of the monkey brain, and therefore likely to have been conserved throughout mammalian evolution. Insofar as the superior colliculus is configured to detect unpredicted, biologically salient, sensory events, it may be safer to regard the phasic responses of midbrain dopaminergic neurons as ‘sensory prediction errors’ rather than ‘reward prediction errors’, in which case, dopamine-based theories of reinforcement learning will require revision. PMID:19175405

Attention modulates specific motor cortical circuits recruited by transcranial magnetic stimulation.

PubMed

Mirdamadi, J L; Suzuki, L Y; Meehan, S K

2017-09-17

Skilled performance and acquisition is dependent upon afferent input to motor cortex. The present study used short-latency afferent inhibition (SAI) to probe how manipulation of sensory afference by attention affects different circuits projecting to pyramidal tract neurons in motor cortex. SAI was assessed in the first dorsal interosseous muscle while participants performed a low or high attention-demanding visual detection task. SAI was evoked by preceding a suprathreshold transcranial magnetic stimulus with electrical stimulation of the median nerve at the wrist. To isolate different afferent intracortical circuits in motor cortex SAI was evoked using either posterior-anterior (PA) or anterior-posterior (PA) monophasic current. In an independent sample, somatosensory processing during the same attention-demanding visual detection tasks was assessed using somatosensory-evoked potentials (SEP) elicited by median nerve stimulation. SAI elicited by AP TMS was reduced under high compared to low visual attention demands. SAI elicited by PA TMS was not affected by visual attention demands. SEPs revealed that the high visual attention load reduced the fronto-central P20-N30 but not the contralateral parietal N20-P25 SEP component. P20-N30 reduction confirmed that the visual attention task altered sensory afference. The current results offer further support that PA and AP TMS recruit different neuronal circuits. AP circuits may be one substrate by which cognitive strategies shape sensorimotor processing during skilled movement by altering sensory processing in premotor areas. Copyright © 2017 IBRO. Published by Elsevier Ltd. All rights reserved.

Concurrent deployment of visual attention and response selection bottleneck in a dual-task: Electrophysiological and behavioural evidence.

PubMed

Reimer, Christina B; Strobach, Tilo; Schubert, Torsten

2017-12-01

Visual attention and response selection are limited in capacity. Here, we investigated whether visual attention requires the same bottleneck mechanism as response selection in a dual-task of the psychological refractory period (PRP) paradigm. The dual-task consisted of an auditory two-choice discrimination Task 1 and a conjunction search Task 2, which were presented at variable temporal intervals (stimulus onset asynchrony, SOA). In conjunction search, visual attention is required to select items and to bind their features resulting in a serial search process around the items in the search display (i.e., set size). We measured the reaction time of the visual search task (RT2) and the N2pc, an event-related potential (ERP), which reflects lateralized visual attention processes. If the response selection processes in Task 1 influence the visual attention processes in Task 2, N2pc latency and amplitude would be delayed and attenuated at short SOA compared to long SOA. The results, however, showed that latency and amplitude were independent of SOA, indicating that visual attention was concurrently deployed to response selection. Moreover, the RT2 analysis revealed an underadditive interaction of SOA and set size. We concluded that visual attention does not require the same bottleneck mechanism as response selection in dual-tasks.

Repeatability of short-duration transient visual evoked potentials in normal subjects.

PubMed

Tello, Celso; De Moraes, Carlos Gustavo V; Prata, Tiago S; Derr, Peter; Patel, Jayson; Siegfried, John; Liebmann, Jeffrey M; Ritch, Robert

2010-06-01

To evaluate the within-session and inter-session repeatability of a new, short-duration transient visual evoked potential (SD-tVEP) device on normal individuals, we tested 30 normal subjects (20/20 visual acuity, normal 24-2 SITA Standard VF) with SD-tVEP. Ten of these subjects had their tests repeated within 1-2 months from the initial visit. Synchronized single-channel EEG was recorded using a modified Diopsys Enfant System (Diopsys, Inc., Pine Brook, New Jersey, USA). A checkerboard stimulus was modulated at two reversals per second. Two different contrasts of checkerboard reversal patterns were used: 85% Michelson contrast with a mean luminance of 66.25 cd/m(2) and 10% Michelson contrast with a mean luminance of 112 cd/m(2). Each test lasted 20 s. Both eyes, independently and together, were tested 10 times (5 times at each contrast level). The following information was identified from the filtered N75-P100-N135 complex: N75 amplitude, N75 latency, P100 amplitude, P100 latency, and Delta Amplitude (N75-P100). The median values for each eye's five SD-tVEP parameters were calculated and grouped into two data sets based on contrast level. Mean age was 27.3 +/- 5.2 years. For OD only, the median (95% confidence intervals) of Delta Amplitude (N75-P100) amplitudes at 10% and 85% contrast were 4.6 uV (4.1-5.9) and 7.1 uV (5.15-9.31). The median P100 latencies were 115.2 ms (112.0-117.7) and 104.0 ms (99.9-106.0). There was little within-session variability for any of these parameters. Intraclass correlation coefficients ranged between 0.64 and 0.98, and within subject coefficients of variation were 3-5% (P100 latency) and 15-30% (Delta Amplitude (N75-P100) amplitude). Bland-Altman plots showed good agreement between the first and fifth test sessions (85% contrast Delta Amplitude (N75-P100) delta amplitude, mean difference, 0.48 mV, 95% CI, -0.18-1.12; 85% contrast P100 latency delay, -0.82 ms, 95% CI, -3.12-1.46; 10% contrast Delta Amplitude (N75-P100) amplitude, 0.58 mV, 95% CI, -0.27-1.45; 10% contrast P100 latency delay, -2.05 mV, 95% CI, -5.12-1.01). The inter-eye correlation and agreement were significant for both SD-tVEP amplitude and P100 latency measurements. For the subset of eyes in which the inter-session repeatability was tested, the intraclass correlation coefficients ranged between 0.71 and 0.86 with good agreement shown on Bland-Altman plots. Short-duration transient VEP technology showed good within-session, inter-session repeatability, and good inter-eye correlation and agreement.

First-spike latency in Hodgkin's three classes of neurons.

PubMed

Wang, Hengtong; Chen, Yueling; Chen, Yong

2013-07-07

We study the first-spike latency (FSL) in Hodgkin's three classes of neurons with the Morris-Lecar neuron model. It is found that all the three classes of neurons can encode an external stimulus into FSLs. With DC inputs, the FSLs of all of the neurons decrease with input intensity. With input current decreased to the threshold, class 1 neurons show an arbitrary long FSL whereas class 2 and 3 neurons exhibit the short-limit FSLs. When the input current is sinusoidal, the amplitude, frequency and initial phase can be encoded by all the three classes of neurons. The FSLs of all of the neurons decrease with the input amplitude and frequency. When the input frequency is too high, all of the neurons respond with infinite FSLs. When the initial phase increases, the FSL decreases and then jumps to a maximal value and finally decreases linearly. With changes in the input parameters, the FSLs of the class 1 and 2 neurons exhibit similar properties. However, the FSL of the class 3 neurons became slightly longer and only produces responses for a narrow range of initial phase if input frequencies are low. Moreover, our results also show that the FSL and firing rate responses are mutually independent processes and that neurons can encode an external stimulus into different FSLs and firing rates simultaneously. This finding is consistent with the current theory of dual or multiple complementary coding mechanisms. Copyright © 2013 Elsevier Ltd. All rights reserved.

Neuronal activity in the lateral cerebellum of the cat related to visual stimuli at rest, visually guided step modification, and saccadic eye movements

PubMed Central

Marple-Horvat, D E; Criado, J M; Armstrong, D M

1998-01-01

The discharge patterns of 166 lateral cerebellar neurones were studied in cats at rest and during visually guided stepping on a horizontal circular ladder. A hundred and twelve cells were tested against one or both of two visual stimuli: a brief full-field flash of light delivered during eating or rest, and a rung which moved up as the cat approached. Forty-five cells (40%) gave a short latency response to one or both of these stimuli. These visually responsive neurones were found in hemispheral cortex (rather than paravermal) and the lateral cerebellar nucleus (rather than nucleus interpositus).Thirty-seven cells (of 103 tested, 36%) responded to flash. The cortical visual response (mean onset latency 38 ms) was usually an increase in Purkinje cell discharge rate, of around 50 impulses s−1 and representing 1 or 2 additional spikes per trial (1.6 on average). The nuclear response to flash (mean onset latency 27 ms) was usually an increased discharge rate which was shorter lived and converted rapidly to a depression of discharge or return to control levels, so that there were on average only an additional 0.6 spikes per trial. A straightforward explanation of the difference between the cortical and nuclear response would be that the increased inhibitory Purkinje cell output cuts short the nuclear response.A higher proportion of cells responded to rung movement, sixteen of twenty-five tested (64%). Again most responded with increased discharge, which had longer latency than the flash response (first change in dentate output ca 60 ms after start of movement) and longer duration. Peak frequency changes were twice the size of those in response to flash, at 100 impulses s−1 on average and additional spikes per trial were correspondingly 3–4 times higher. Both cortical and nuclear responses were context dependent, being larger when the rung moved when the cat was closer than further away.A quarter of cells (20 of 84 tested, 24%) modulated their activity in advance of saccades, increasing their discharge rate. Four-fifths of these were non-reciprocally directionally selective. Saccade-related neurones were usually susceptible to other influences, i.e. their activity was not wholly explicable in terms of saccade parameters.Substantial numbers of visually responsive neurones also discharged in relation to stepping movements while other visually responsive neurones discharged in advance of saccadic eye movements. And more than half the cells tested were active in relation both to eye movements and to stepping movements. These combinations of properties qualify even individual cerebellar neurones to participate in the co-ordination of visually guided eye and limb movements. PMID:9490874

Haptic over visual information in the distribution of visual attention after tool-use in near and far space.

PubMed

Park, George D; Reed, Catherine L

2015-10-01

Despite attentional prioritization for grasping space near the hands, tool-use appears to transfer attentional bias to the tool's end/functional part. The contributions of haptic and visual inputs to attentional distribution along a tool were investigated as a function of tool-use in near (Experiment 1) and far (Experiment 2) space. Visual attention was assessed with a 50/50, go/no-go, target discrimination task, while a tool was held next to targets appearing near the tool-occupied hand or tool-end. Target response times (RTs) and sensitivity (d-prime) were measured at target locations, before and after functional tool practice for three conditions: (1) open-tool: tool-end visible (visual + haptic inputs), (2) hidden-tool: tool-end visually obscured (haptic input only), and (3) short-tool: stick missing tool's length/end (control condition: hand occupied but no visual/haptic input). In near space, both open- and hidden-tool groups showed a tool-end, attentional bias (faster RTs toward tool-end) before practice; after practice, RTs near the hand improved. In far space, the open-tool group showed no bias before practice; after practice, target RTs near the tool-end improved. However, the hidden-tool group showed a consistent tool-end bias despite practice. Lack of short-tool group results suggested that hidden-tool group results were specific to haptic inputs. In conclusion, (1) allocation of visual attention along a tool due to tool practice differs in near and far space, and (2) visual attention is drawn toward the tool's end even when visually obscured, suggesting haptic input provides sufficient information for directing attention along the tool.

Neuronal responses to face-like stimuli in the monkey pulvinar.

PubMed

Nguyen, Minh Nui; Hori, Etsuro; Matsumoto, Jumpei; Tran, Anh Hai; Ono, Taketoshi; Nishijo, Hisao

2013-01-01

The pulvinar nuclei appear to function as the subcortical visual pathway that bypasses the striate cortex, rapidly processing coarse facial information. We investigated responses from monkey pulvinar neurons during a delayed non-matching-to-sample task, in which monkeys were required to discriminate five categories of visual stimuli [photos of faces with different gaze directions, line drawings of faces, face-like patterns (three dark blobs on a bright oval), eye-like patterns and simple geometric patterns]. Of 401 neurons recorded, 165 neurons responded differentially to the visual stimuli. These visual responses were suppressed by scrambling the images. Although these neurons exhibited a broad response latency distribution, face-like patterns elicited responses with the shortest latencies (approximately 50 ms). Multidimensional scaling analysis indicated that the pulvinar neurons could specifically encode face-like patterns during the first 50-ms period after stimulus onset and classify the stimuli into one of the five different categories during the next 50-ms period. The amount of stimulus information conveyed by the pulvinar neurons and the number of stimulus-differentiating neurons were consistently higher during the second 50-ms period than during the first 50-ms period. These results suggest that responsiveness to face-like patterns during the first 50-ms period might be attributed to ascending inputs from the superior colliculus or the retina, while responsiveness to the five different stimulus categories during the second 50-ms period might be mediated by descending inputs from cortical regions. These findings provide neurophysiological evidence for pulvinar involvement in social cognition and, specifically, rapid coarse facial information processing. © 2012 Federation of European Neuroscience Societies and Blackwell Publishing Ltd.

[Visual perception of Kanji characters and complicated figures. II. Visual P300 event-related potentials in patients with mental retardation].

PubMed

Sata, Yoshimi; Inagaki, Masumi; Shirane, Seiko; Kaga, Makiko

2002-11-01

In order to objectively evaluate visual perception of patients with mental retardation (MR), the P300 event-related potentials (ERPs) for visual oddball tasks were recorded in 26 patients and 13 age-matched healthy volunteers. The latency and amplitude of visual P300 in response to the Japanese ideogram stimuli (a pair of familiar Kanji characters or unfamiliar Kanji characters) and a pair of meaningless complicated figures were measured. In almost all MR patients visual P300 was observed, however, the peak latency was significantly prolonged compared to control subjects. There was no significant difference of P300 latency among the three tasks. The distribution pattern of P300 in MR patients was different from that in the controls and the amplitudes in the frontal region was larger in MR patients. The latency decreased with age even in both groups. The developmental change of P300 latency corresponded to developmental age rather than the chronological age. These findings suggest that MR patients have impairment in processing of visual perception. Assessment of P300 latencies to the visual stimuli may be useful as an objective indicator of mental deficit.

Correspondence between visual and electrical input filters of ON and OFF mouse retinal ganglion cells

NASA Astrophysics Data System (ADS)

Sekhar, S.; Jalligampala, A.; Zrenner, E.; Rathbun, D. L.

2017-08-01

Objective. Over the past two decades retinal prostheses have made major strides in restoring functional vision to patients blinded by diseases such as retinitis pigmentosa. Presently, implants use single pulses to activate the retina. Though this stimulation paradigm has proved beneficial to patients, an unresolved problem is the inability to selectively stimulate the on and off visual pathways. To this end our goal was to test, using white noise, voltage-controlled, cathodic, monophasic pulse stimulation, whether different retinal ganglion cell (RGC) types in the wild type retina have different electrical input filters. This is an important precursor to addressing pathway-selective stimulation. Approach. Using full-field visual flash and electrical and visual Gaussian noise stimulation, combined with the technique of spike-triggered averaging (STA), we calculate the electrical and visual input filters for different types of RGCs (classified as on, off or on-off based on their response to the flash stimuli). Main results. Examining the STAs, we found that the spiking activity of on cells during electrical stimulation correlates with a decrease in the voltage magnitude preceding a spike, while the spiking activity of off cells correlates with an increase in the voltage preceding a spike. No electrical preference was found for on-off cells. Comparing STAs of wild type and rd10 mice revealed narrower electrical STA deflections with shorter latencies in rd10. Significance. This study is the first comparison of visual cell types and their corresponding temporal electrical input filters in the retina. The altered input filters in degenerated rd10 retinas are consistent with photoreceptor stimulation underlying visual type-specific electrical STA shapes in wild type retina. It is therefore conceivable that existing implants could target partially degenerated photoreceptors that have only lost their outer segments, but not somas, to selectively activate the on and off visual pathways.

Visual Evoked Potential to Assess Retinopathy in Gestational Diabetes Mellitus.

PubMed

Hari Kumar, K V S; Ahmad, F M H; Sood, Sandeep; Mansingh, Sudhir

2016-04-01

We evaluated for early retinopathy using the visual evoked potential (VEP) in patients with gestational diabetes mellitus (GDM) and type 2 diabetes mellitus during pregnancy. All patients with GDM and type 2 diabetes seen between June and October of 2014 were included in this cross-sectional, observational study. Patients with secondary diabetes, ocular or major illness were excluded from the study. VEP was recorded in both eyes to derive prominent positive peak latency (P100), amplitude and initial negative deflection (N75) latency. The data were compared with 10 gestational age-matched controls with normal glucose tolerance. Appropriate statistical methods were used for comparison among the 3 groups. The study participants (40 with GDM, 10 with type 2 diabetes, 10 with normal glucose tolerance) had a median (25th to 75th interquartile range) age of 26 (24.3, 30) years, a gestational age of 24.5 (21, 27) weeks and weights of 66.8 (63.4, 71.5) kg. The P100 latencies were comparable among the 3 groups (p=0.0577). However, patients with any diabetes (GDM and type 2 diabetes) had prolonged P100 latencies (p=0.0139) and low P100 amplitudes (p=0.0391) in comparison to controls. P100 latency showed a direct correlation with hyperglycemia (p=0.0118). Our data showed that VEP abnormalities are detectable even in the short-term hyperglycemia of GDM and type 2 diabetes. Copyright © 2016 Canadian Diabetes Association. Published by Elsevier Inc. All rights reserved.

Acute and Chronic Noradrenergic Effects on Cortical Excitability in Healthy Humans

PubMed Central

Kuo, Hsiao-I; Paulus, Walter; Batsikadze, Giorgi; Jamil, Asif; Kuo, Min-Fang

2017-01-01

Abstract Background Noradrenaline is a major neuromodulator in the central nervous system, and it is involved in the pathophysiology of diverse neuropsychiatric diseases. Previous transcranial magnetic stimulation studies suggested that acute application of selective noradrenaline reuptake inhibitors enhances cortical excitability in the human brain. However, other, such like clinical effects, usually require prolonged noradrenaline reuptake inhibitor treatment, which might go along with different physiological effects. Methods The purpose of this study was to investigate the acute and chronic effects of the selective noradrenaline reuptake inhibitor reboxetine on cortical excitability in healthy humans in a double-blind, placebo-controlled, randomized crossover study. Sixteen subjects were assessed with different transcranial magnetic stimulation measurements: motor thresholds, input-output curve, short-latency intracortical inhibition and intracortical facilitation, I-wave facilitation, and short-interval afferent inhibition before and after placebo or reboxetine (8 mg) single-dose administration. Afterwards, the same subjects took reboxetine (8 mg/d) consecutively for 21 days. During this period (subjects underwent 2 experimental sessions with identical transcranial magnetic stimulation measures under placebo or reboxetine), transcranial magnetic stimulation measurements were assessed before and after drug intake. Results Both single-dose and chronic administration of reboxetine increased cortical excitability; increased the slope of the input-output curve, intracortical facilitation, and I-wave facilitation; but decreased short-latency intracortical inhibition and short-interval afferent inhibition. Moreover, chronic reboxetine showed a larger enhancement of intracortical facilitation and I-wave facilitation compared with single-dose application. Conclusions The results show physiological mechanisms of noradrenergic enhancement possibly underlying the functional effects of reboxetine regarding acute and chronic application. PMID:28430976

Synaptic physiology of the flow of information in the cat's visual cortex in vivo

PubMed Central

Hirsch, Judith A; Martinez, Luis M; Alonso, José-Manuel; Desai, Komal; Pillai, Cinthi; Pierre, Carhine

2002-01-01

Each stage of the striate cortical circuit extracts novel information about the visual environment. We asked if this analytic process reflected laminar variations in synaptic physiology by making whole-cell recording with dye-filled electrodes from the cat's visual cortex and thalamus; the stimuli were flashed spots. Thalamic afferents terminate in layer 4, which contains two types of cell, simple and complex, distinguished by the spatial structure of the receptive field. Previously, we had found that the postsynaptic and spike responses of simple cells reliably followed the time course of flash-evoked thalamic activity. Here we report that complex cells in layer 4 (or cells intermediate between simple and complex) similarly reprised thalamic activity (response/trial, 99 ± 1.9 %; response duration 159 ± 57 ms; latency 25 ± 4 ms; average ± standard deviation; n = 7). Thus, all cells in layer 4 share a common synaptic physiology that allows secure integration of thalamic input. By contrast, at the second cortical stage (layer 2+3), where layer 4 directs its output, postsynaptic responses did not track simple patterns of antecedent activity. Typical responses to the static stimulus were intermittent and brief (response/trial, 31 ± 40 %; response duration 72 ± 60 ms, latency 39 ± 7 ms; n = 11). Only richer stimuli like those including motion evoked reliable responses. All told, the second level of cortical processing differs markedly from the first. At that later stage, ascending information seems strongly gated by connections between cortical neurons. Inputs must be combined in newly specified patterns to influence intracortical stages of processing. PMID:11927691

Contralateral Effects and Binaural Interactions in Dorsal Cochlear Nucleus

PubMed Central

2005-01-01

The dorsal cochlear nucleus (DCN) receives afferent input from the auditory nerve and is thus usually thought of as a monaural nucleus, but it also receives inputs from the contralateral cochlear nucleus as well as descending projections from binaural nuclei. Evidence suggests that some of these commissural and efferent projections are excitatory, whereas others are inhibitory. The goals of this study were to investigate the nature and effects of these inputs in the DCN by measuring DCN principal cell (type IV unit) responses to a variety of contralateral monaural and binaural stimuli. As expected, the results of contralateral stimulation demonstrate a mixture of excitatory and inhibitory influences, although inhibitory effects predominate. Most type IV units are weakly, if at all, inhibited by tones but are strongly inhibited by broadband noise (BBN). The inhibition evoked by BBN is also low threshold and short latency. This inhibition is abolished and excitation is revealed when strychnine, a glycine-receptor antagonist, is applied to the DCN; application of bicuculline, a GABAA-receptor antagonist, has similar effects but does not block the onset of inhibition. Manipulations of discrete fiber bundles suggest that the inhibitory, but not excitatory, inputs to DCN principal cells enter the DCN via its output pathway, and that the short latency inhibition is carried by commissural axons. Consistent with their respective monaural effects, responses to binaural tones as a function of interaural level difference are essentially the same as responses to ipsilateral tones, whereas binaural BBN responses decrease with increasing contralateral level. In comparison to monaural responses, binaural responses to virtual space stimuli show enhanced sensitivity to the elevation of a sound source in ipsilateral space but reduced sensitivity in contralateral space. These results show that the contralateral inputs to the DCN are functionally relevant in natural listening conditions, and that one role of these inputs is to enhance DCN processing of spectral sound localization cues produced by the pinna. PMID:16075189

Influence of P300 latency jitter on event related potential-based brain-computer interface performance

NASA Astrophysics Data System (ADS)

Aricò, P.; Aloise, F.; Schettini, F.; Salinari, S.; Mattia, D.; Cincotti, F.

2014-06-01

Objective. Several ERP-based brain-computer interfaces (BCIs) that can be controlled even without eye movements (covert attention) have been recently proposed. However, when compared to similar systems based on overt attention, they displayed significantly lower accuracy. In the current interpretation, this is ascribed to the absence of the contribution of short-latency visual evoked potentials (VEPs) in the tasks performed in the covert attention modality. This study aims to investigate if this decrement (i) is fully explained by the lack of VEP contribution to the classification accuracy; (ii) correlates with lower temporal stability of the single-trial P300 potentials elicited in the covert attention modality. Approach. We evaluated the latency jitter of P300 evoked potentials in three BCI interfaces exploiting either overt or covert attention modalities in 20 healthy subjects. The effect of attention modality on the P300 jitter, and the relative contribution of VEPs and P300 jitter to the classification accuracy have been analyzed. Main results. The P300 jitter is higher when the BCI is controlled in covert attention. Classification accuracy negatively correlates with jitter. Even disregarding short-latency VEPs, overt-attention BCI yields better accuracy than covert. When the latency jitter is compensated offline, the difference between accuracies is not significant. Significance. The lower temporal stability of the P300 evoked potential generated during the tasks performed in covert attention modality should be regarded as the main contributing explanation of lower accuracy of covert-attention ERP-based BCIs.

Multiple pathways carry signals from short-wavelength-sensitive ('blue') cones to the middle temporal area of the macaque.

PubMed

Jayakumar, Jaikishan; Roy, Sujata; Dreher, Bogdan; Martin, Paul R; Vidyasagar, Trichur R

2013-01-01

We recorded spike activity of single neurones in the middle temporal visual cortical area (MT or V5) of anaesthetised macaque monkeys. We used flashing, stationary spatially circumscribed, cone-isolating and luminance-modulated stimuli of uniform fields to assess the effects of signals originating from the long-, medium- or short- (S) wavelength-sensitive cone classes. Nearly half (41/86) of the tested MT neurones responded reliably to S-cone-isolating stimuli. Response amplitude in the majority of the neurones tested further (19/28) was significantly reduced, though not always completely abolished, during reversible inactivation of visuotopically corresponding regions of the ipsilateral primary visual cortex (striate cortex, area V1). Thus, the present data indicate that signals originating in S-cones reach area MT, either via V1 or via a pathway that does not go through area V1. We did not find a significant difference between the mean latencies of spike responses of MT neurones to signals that bypass V1 and those that do not; the considerable overlap we observed precludes the use of spike-response latency as a criterion to define the routes through which the signals reach MT.

Group II muscle afferents probably contribute to the medium latency soleus stretch reflex during walking in humans

PubMed Central

Grey, Michael J; Ladouceur, Michel; Andersen, Jacob B; Nielsen, Jens Bo; Sinkjær, Thomas

2001-01-01

The objective of this study was to determine which afferents contribute to the medium latency response of the soleus stretch reflex resulting from an unexpected perturbation during human walking. Fourteen healthy subjects walked on a treadmill at approximately 3.5 km h−1 with the left ankle attached to a portable stretching device. The soleus stretch reflex was elicited by applying small amplitude (∼8 deg) dorsiflexion perturbations 200 ms after heel contact. Short and medium latency responses were observed with latencies of 55 ± 5 and 78 ± 6 ms, respectively. The short latency response was velocity sensitive (P < 0.001), while the medium latency response was not (P = 0.725). Nerve cooling increased the delay of the medium latency component to a greater extent than that of the short latency component (P < 0.005). Ischaemia strongly decreased the short latency component (P = 0.004), whereas the medium latency component was unchanged (P = 0.437). Two hours after the ingestion of tizanidine, an α2-adrenergic receptor agonist known to selectively depress the transmission in the group II afferent pathway, the medium latency reflex was strongly depressed (P = 0.007), whereas the short latency component was unchanged (P = 0.653). An ankle block with lidocaine hydrochloride was performed to suppress the cutaneous afferents of the foot and ankle. Neither the short (P = 0.453) nor medium (P = 0.310) latency reflexes were changed. Our results support the hypothesis that, during walking the medium latency component of the stretch reflex resulting from an unexpected perturbation is contributed to by group II muscle afferents. PMID:11483721

Minimizing Input-to-Output Latency in Virtual Environment

NASA Technical Reports Server (NTRS)

Adelstein, Bernard D.; Ellis, Stephen R.; Hill, Michael I.

2009-01-01

A method and apparatus were developed to minimize latency (time delay ) in virtual environment (VE) and other discrete- time computer-base d systems that require real-time display in response to sensor input s. Latency in such systems is due to the sum of the finite time requi red for information processing and communication within and between sensors, software, and displays.

Encoding of Spatio-Temporal Input Characteristics by a CA1 Pyramidal Neuron Model

PubMed Central

Pissadaki, Eleftheria Kyriaki; Sidiropoulou, Kyriaki; Reczko, Martin; Poirazi, Panayiota

2010-01-01

The in vivo activity of CA1 pyramidal neurons alternates between regular spiking and bursting, but how these changes affect information processing remains unclear. Using a detailed CA1 pyramidal neuron model, we investigate how timing and spatial arrangement variations in synaptic inputs to the distal and proximal dendritic layers influence the information content of model responses. We find that the temporal delay between activation of the two layers acts as a switch between excitability modes: short delays induce bursting while long delays decrease firing. For long delays, the average firing frequency of the model response discriminates spatially clustered from diffused inputs to the distal dendritic tree. For short delays, the onset latency and inter-spike-interval succession of model responses can accurately classify input signals as temporally close or distant and spatially clustered or diffused across different stimulation protocols. These findings suggest that a CA1 pyramidal neuron may be capable of encoding and transmitting presynaptic spatiotemporal information about the activity of the entorhinal cortex-hippocampal network to higher brain regions via the selective use of either a temporal or a rate code. PMID:21187899

Influence of hypoglycaemia, with or without caffeine ingestion, on visual sensation and performance.

PubMed

Owen, G; Watson, J; McGown, A; Sharma, S; Deary, I; Kerr, D; Barrett, G

2001-06-01

Full-field visual evoked potentials and visual information processing were measured in 16 normal, healthy subjects during a hyperinsulinaemic clamp. A randomized cross-over design was used across three conditions: hypoglycaemia and caffeine; hypoglycaemia and placebo; and euglycaemia and caffeine. The latency of the P100 component of the pattern-reversal visual evoked potential increased significantly from rest to hypoglycaemia, but no effect of caffeine was found. Subjects were subsequently divided into two median groups based on the increase in P100 latency in the placebo condition (Group 1, +0.5 ms; Group 2, +5.6 ms). In the absence of caffeine, an inverse correlation between the increase in P100 latency from rest and a deterioration in visual movement detection was found for Group 2, but not for Group 1. Caffeine ingestion resulted in a further increase in P100 latency, from rest to hypoglycaemia, for subjects in Group 2. Hypoglycaemia in the absence of caffeine produces changes in visual sensation from rest to hypoglycaemia. In those subjects most sensitive to the effects of hypoglycaemia (Group 2), the increase in P100 latency was associated with poorer performance in tests of visual information processing. Caffeine ingestion produced further increases in P100 latency in these subjects.

Short- and long-latency auditory evoked potentials in individuals with vestibular dysfunction.

PubMed

Santos Filha, Valdete Alves Valentins Dos; Bruckmann, Mirtes; Garcia, Michele Vargas

2018-01-01

Purpose Evaluate the auditory pathway at the brainstem and cortical levels in individuals with peripheral vestibular dysfunction. Methods The study sample was composed 19 individuals aged 20-80 years that presented exam results suggestive of Peripheral Vestibular Disorder (PVD) or Vestibular Dysfunction (VD). Participants underwent evaluation of the auditory pathway through Brainstem Auditory Evoked Potentials (BAEP) (short latency) and P1, N1, P2, N2, and P300 cortical potentials (long latency). Results Nine individuals presented diagnosis of VD and 10 participants were diagnosed with PVD. The overall average of the long latency potentials of the participants was within the normal range, whereas an increased mean was observed in the short latency of waves III and V of the left ear, as well as in the I - III interpeak interval of both ears. Association of the auditory potentials with VD and PVD showed statistically significant correlation only in the III - V interpeak interval of the right ear for short latency. Comparison between the long and short latencies in the groups showed differences between VD and PVD, but without statistical significance. Conclusion No statistically significant correlation was observed between VD/PVD and the auditory evoked potentials; however, for the long latency potentials, individuals with VD presented higher latency in P1, N1, P2, and N2, where as participants with PVD showed higher latency in P300. In the short latency potentials, there was an increase in the absolute latencies in the VD group and in the interpeak intervals in the PVD group.

Comparison of multifocal visual evoked potential, standard automated perimetry and optical coherence tomography in assessing visual pathway in multiple sclerosis patients

PubMed Central

Laron, Michal; Cheng, Han; Zhang, Bin; Schiffman, Jade S.; Tang, Rosa A.; Frishman, Laura J.

2010-01-01

Background Multifocal visual evoked potentials (mfVEP) measure local response amplitude and latency in the field of vision Objective To compare the sensitivity of mfVEP, Humphrey visual field (HVF) and optical coherence tomography (OCT) in detecting visual abnormality in multiple sclerosis (MS) patients. Methods MfVEP, HVF, and OCT (retinal nerve fiber layer [RNFL]) were performed in 47 MS-ON eyes (last optic neuritis (ON) attack ≥ 6 months prior) and 65 MS-no-ON eyes without ON history. Criteria to define an eye as abnormal were: mfVEP 1) amplitude/latency: either amplitude or latency probability plots meeting cluster criteria with 95% specificity 2) amplitude or latency alone (specificity: 97% and 98%, respectively); HVF and OCT, mean deviation and RNFL thickness meeting p < 0.05, respectively. Results MfVEP (amplitude/latency) identified more abnormality in MS-ON eyes (89%) than HVF (72%), OCT (62%), mfVEP amplitude (66%) or latency (67%) alone. 18% of MS-no-ON eyes were abnormal for both mfVEP (amplitude/latency) and HVF compared to 8% with OCT. Agreement between tests ranged from 60% to 79%. MfVEP (amplitude/latency) categorized an additional 15% of MS-ON eyes as abnormal compared to HVF and OCT combined. Conclusions MfVEP, which detects both demyelination (increased latency) and neural degeneration (reduced amplitude) revealed more abnormality than HVF or OCT in MS patients. PMID:20207786

Complex regional pain syndrome (CRPS) or continuous unilateral distal experimental pain stimulation in healthy subjects does not bias visual attention towards one hemifield.

PubMed

Filippopulos, Filipp M; Grafenstein, Jessica; Straube, Andreas; Eggert, Thomas

2015-11-01

In natural life pain automatically draws attention towards the painful body part suggesting that it interacts with different attentional mechanisms such as visual attention. Complex regional pain syndrome (CRPS) patients who typically report on chronic distally located pain of one extremity may suffer from so-called neglect-like symptoms, which have also been linked to attentional mechanisms. The purpose of the study was to further evaluate how continuous pain conditions influence visual attention. Saccade latencies were recorded in two experiments using a common visual attention paradigm whereby orientating saccades to cued or uncued lateral visual targets had to be performed. In the first experiment saccade latencies of healthy subjects were measured under two conditions: one in which continuous experimental pain stimulation was applied to the index finger to imitate a continuous pain situation, and one without pain stimulation. In the second experiment saccade latencies of patients suffering from CRPS were compared to controls. The results showed that neither the continuous experimental pain stimulation during the experiment nor the chronic pain in CRPS led to an unilateral increase of saccade latencies or to a unilateral increase of the cue effect on latency. The results show that unilateral, continuously applied pain stimuli or chronic pain have no or only very limited influence on visual attention. Differently from patients with visual neglect, patients with CRPS did not show strong side asymmetries of saccade latencies or of cue effects on saccade latencies. Thus, neglect-like clinical symptoms of CRPS patients do not involve the allocation of visual attention.

Cumulative latency advance underlies fast visual processing in desynchronized brain state

PubMed Central

Wang, Xu-dong; Chen, Cheng; Zhang, Dinghong; Yao, Haishan

2014-01-01

Fast sensory processing is vital for the animal to efficiently respond to the changing environment. This is usually achieved when the animal is vigilant, as reflected by cortical desynchronization. However, the neural substrate for such fast processing remains unclear. Here, we report that neurons in rat primary visual cortex (V1) exhibited shorter response latency in the desynchronized state than in the synchronized state. In vivo whole-cell recording from the same V1 neurons undergoing the two states showed that both the resting and visually evoked conductances were higher in the desynchronized state. Such conductance increases of single V1 neurons shorten the response latency by elevating the membrane potential closer to the firing threshold and reducing the membrane time constant, but the effects only account for a small fraction of the observed latency advance. Simultaneous recordings in lateral geniculate nucleus (LGN) and V1 revealed that LGN neurons also exhibited latency advance, with a degree smaller than that of V1 neurons. Furthermore, latency advance in V1 increased across successive cortical layers. Thus, latency advance accumulates along various stages of the visual pathway, likely due to a global increase of membrane conductance in the desynchronized state. This cumulative effect may lead to a dramatic shortening of response latency for neurons in higher visual cortex and play a critical role in fast processing for vigilant animals. PMID:24347634

Cumulative latency advance underlies fast visual processing in desynchronized brain state.

PubMed

Wang, Xu-dong; Chen, Cheng; Zhang, Dinghong; Yao, Haishan

2014-01-07

Fast sensory processing is vital for the animal to efficiently respond to the changing environment. This is usually achieved when the animal is vigilant, as reflected by cortical desynchronization. However, the neural substrate for such fast processing remains unclear. Here, we report that neurons in rat primary visual cortex (V1) exhibited shorter response latency in the desynchronized state than in the synchronized state. In vivo whole-cell recording from the same V1 neurons undergoing the two states showed that both the resting and visually evoked conductances were higher in the desynchronized state. Such conductance increases of single V1 neurons shorten the response latency by elevating the membrane potential closer to the firing threshold and reducing the membrane time constant, but the effects only account for a small fraction of the observed latency advance. Simultaneous recordings in lateral geniculate nucleus (LGN) and V1 revealed that LGN neurons also exhibited latency advance, with a degree smaller than that of V1 neurons. Furthermore, latency advance in V1 increased across successive cortical layers. Thus, latency advance accumulates along various stages of the visual pathway, likely due to a global increase of membrane conductance in the desynchronized state. This cumulative effect may lead to a dramatic shortening of response latency for neurons in higher visual cortex and play a critical role in fast processing for vigilant animals.

Time-resolved neuroimaging of visual short term memory consolidation by post-perceptual attention shifts.

PubMed

Hecht, Marcus; Thiemann, Ulf; Freitag, Christine M; Bender, Stephan

2016-01-15

Post-perceptual cues can enhance visual short term memory encoding even after the offset of the visual stimulus. However, both the mechanisms by which the sensory stimulus characteristics are buffered as well as the mechanisms by which post-perceptual selective attention enhances short term memory encoding remain unclear. We analyzed late post-perceptual event-related potentials (ERPs) in visual change detection tasks (100ms stimulus duration) by high-resolution ERP analysis to elucidate these mechanisms. The effects of early and late auditory post-cues (300ms or 850ms after visual stimulus onset) as well as the effects of a visual interference stimulus were examined in 27 healthy right-handed adults. Focusing attention with post-perceptual cues at both latencies significantly improved memory performance, i.e. sensory stimulus characteristics were available for up to 850ms after stimulus presentation. Passive watching of the visual stimuli without auditory cue presentation evoked a slow negative wave (N700) over occipito-temporal visual areas. N700 was strongly reduced by a visual interference stimulus which impeded memory maintenance. In contrast, contralateral delay activity (CDA) still developed in this condition after the application of auditory post-cues and was thereby dissociated from N700. CDA and N700 seem to represent two different processes involved in short term memory encoding. While N700 could reflect visual post processing by automatic attention attraction, CDA may reflect the top-down process of searching selectively for the required information through post-perceptual attention. Copyright © 2015 Elsevier Inc. All rights reserved.

Technical note: real-time web-based wireless visual guidance system for radiotherapy.

PubMed

Lee, Danny; Kim, Siyong; Palta, Jatinder R; Kim, Taeho

2017-06-01

Describe a Web-based wireless visual guidance system that mitigates issues associated with hard-wired audio-visual aided patient interactive motion management systems that are cumbersome to use in routine clinical practice. Web-based wireless visual display duplicates an existing visual display of a respiratory-motion management system for visual guidance. The visual display of the existing system is sent to legacy Web clients over a private wireless network, thereby allowing a wireless setting for real-time visual guidance. In this study, active breathing coordinator (ABC) trace was used as an input for visual display, which captured and transmitted to Web clients. Virtual reality goggles require two (left and right eye view) images for visual display. We investigated the performance of Web-based wireless visual guidance by quantifying (1) the network latency of visual displays between an ABC computer display and Web clients of a laptop, an iPad mini 2 and an iPhone 6, and (2) the frame rate of visual display on the Web clients in frames per second (fps). The network latency of visual display between the ABC computer and Web clients was about 100 ms and the frame rate was 14.0 fps (laptop), 9.2 fps (iPad mini 2) and 11.2 fps (iPhone 6). In addition, visual display for virtual reality goggles was successfully shown on the iPhone 6 with 100 ms and 11.2 fps. A high network security was maintained by utilizing the private network configuration. This study demonstrated that a Web-based wireless visual guidance can be a promising technique for clinical motion management systems, which require real-time visual display of their outputs. Based on the results of this study, our approach has the potential to reduce clutter associated with wired-systems, reduce space requirements, and extend the use of medical devices from static usage to interactive and dynamic usage in a radiotherapy treatment vault.

Spatial and temporal features of superordinate semantic processing studied with fMRI and EEG.

PubMed

Costanzo, Michelle E; McArdle, Joseph J; Swett, Bruce; Nechaev, Vladimir; Kemeny, Stefan; Xu, Jiang; Braun, Allen R

2013-01-01

The relationships between the anatomical representation of semantic knowledge in the human brain and the timing of neurophysiological mechanisms involved in manipulating such information remain unclear. This is the case for superordinate semantic categorization-the extraction of general features shared by broad classes of exemplars (e.g., living vs. non-living semantic categories). We proposed that, because of the abstract nature of this information, input from diverse input modalities (visual or auditory, lexical or non-lexical) should converge and be processed in the same regions of the brain, at similar time scales during superordinate categorization-specifically in a network of heteromodal regions, and late in the course of the categorization process. In order to test this hypothesis, we utilized electroencephalography and event related potentials (EEG/ERP) with functional magnetic resonance imaging (fMRI) to characterize subjects' responses as they made superordinate categorical decisions (living vs. non-living) about objects presented as visual pictures or auditory words. Our results reveal that, consistent with our hypothesis, during the course of superordinate categorization, information provided by these diverse inputs appears to converge in both time and space: fMRI showed that heteromodal areas of the parietal and temporal cortices are active during categorization of both classes of stimuli. The ERP results suggest that superordinate categorization is reflected as a late positive component (LPC) with a parietal distribution and long latencies for both stimulus types. Within the areas and times in which modality independent responses were identified, some differences between living and non-living categories were observed, with a more widespread spatial extent and longer latency responses for categorization of non-living items.

Spatial and temporal features of superordinate semantic processing studied with fMRI and EEG

PubMed Central

Costanzo, Michelle E.; McArdle, Joseph J.; Swett, Bruce; Nechaev, Vladimir; Kemeny, Stefan; Xu, Jiang; Braun, Allen R.

2013-01-01

The relationships between the anatomical representation of semantic knowledge in the human brain and the timing of neurophysiological mechanisms involved in manipulating such information remain unclear. This is the case for superordinate semantic categorization—the extraction of general features shared by broad classes of exemplars (e.g., living vs. non-living semantic categories). We proposed that, because of the abstract nature of this information, input from diverse input modalities (visual or auditory, lexical or non-lexical) should converge and be processed in the same regions of the brain, at similar time scales during superordinate categorization—specifically in a network of heteromodal regions, and late in the course of the categorization process. In order to test this hypothesis, we utilized electroencephalography and event related potentials (EEG/ERP) with functional magnetic resonance imaging (fMRI) to characterize subjects' responses as they made superordinate categorical decisions (living vs. non-living) about objects presented as visual pictures or auditory words. Our results reveal that, consistent with our hypothesis, during the course of superordinate categorization, information provided by these diverse inputs appears to converge in both time and space: fMRI showed that heteromodal areas of the parietal and temporal cortices are active during categorization of both classes of stimuli. The ERP results suggest that superordinate categorization is reflected as a late positive component (LPC) with a parietal distribution and long latencies for both stimulus types. Within the areas and times in which modality independent responses were identified, some differences between living and non-living categories were observed, with a more widespread spatial extent and longer latency responses for categorization of non-living items. PMID:23847490

Correlation of Visually Evoked Functional and Blood Flow Changes in the Rat Retina Measured With a Combined OCT+ERG System.

PubMed

Tan, Bingyao; Mason, Erik; MacLellan, Benjamin; Bizheva, Kostadinka K

2017-03-01

To correlate visually evoked functional and blood flow changes in the rat retina measured simultaneously with a combined optical coherence tomography and electroretinography system (OCT+ERG). Male Brown Norway (n = 6) rats were dark adapted and anesthetized with ketamine/xylazine. Visually evoked changes in the retinal blood flow (RBF) and functional response were measured simultaneously with an OCT+ERG system with 3-μm axial resolution in retinal tissue and 47-kHz image acquisition rate. Both single flash (10 and 200 ms) and flicker (10 Hz, 20% duty cycle, 1- and 2-second duration) stimuli were projected onto the retina with a custom visual stimulator, integrated into the OCT imaging probe. Total axial RBF was calculated from circular Doppler OCT scans by integrating over the arterial and venal flow. Temporary increase in the RBF was observed with the 10- and 200-ms continuous stimuli (∼1% and ∼4% maximum RBF change, respectively) and the 10-Hz flicker stimuli (∼8% for 1-second duration and ∼10% for 2-second duration). Doubling the flicker stimulus duration resulted in ∼25% increase in the RBF peak magnitude with no significant change in the peak latency. Single flash (200 ms) and flicker (10 Hz, 1 second) stimuli of the same illumination intensity and photon flux resulted in ∼2× larger peak RBF magnitude and ∼25% larger RBF peak latency for the flicker stimulus. Short, single flash and flicker stimuli evoked measureable RBF changes with larger RBF magnitude and peak latency observed for the flicker stimuli.

Dynamic Target Match Signals in Perirhinal Cortex Can Be Explained by Instantaneous Computations That Act on Dynamic Input from Inferotemporal Cortex

PubMed Central

Pagan, Marino

2014-01-01

Finding sought objects requires the brain to combine visual and target signals to determine when a target is in view. To investigate how the brain implements these computations, we recorded neural responses in inferotemporal cortex (IT) and perirhinal cortex (PRH) as macaque monkeys performed a delayed-match-to-sample target search task. Our data suggest that visual and target signals were combined within or before IT in the ventral visual pathway and then passed onto PRH, where they were reformatted into a more explicit target match signal over ∼10–15 ms. Accounting for these dynamics in PRH did not require proposing dynamic computations within PRH itself but, rather, could be attributed to instantaneous PRH computations performed upon an input representation from IT that changed with time. We found that the dynamics of the IT representation arose from two commonly observed features: individual IT neurons whose response preferences were not simply rescaled with time and variable response latencies across the population. Our results demonstrate that these types of time-varying responses have important consequences for downstream computation and suggest that dynamic representations can arise within a feedforward framework as a consequence of instantaneous computations performed upon time-varying inputs. PMID:25122904

Dynamic modulation of corticospinal excitability and short-latency afferent inhibition during onset and maintenance phase of selective finger movement.

PubMed

Cho, Hyun Joo; Panyakaew, Pattamon; Thirugnanasambandam, Nivethida; Wu, Tianxia; Hallett, Mark

2016-06-01

During highly selective finger movement, corticospinal excitability is reduced in surrounding muscles at the onset of movement but this phenomenon has not been demonstrated during maintenance of movement. Sensorimotor integration may play an important role in selective movement. We sought to investigate how corticospinal excitability and short-latency afferent inhibition changes in active and surrounding muscles during onset and maintenance of selective finger movement. Using transcranial magnetic stimulation (TMS) and paired peripheral stimulation, input-output recruitment curve and short-latency afferent inhibition (SAI) were measured in the first dorsal interosseus and abductor digiti minimi muscles during selective index finger flexion. Motor surround inhibition was present only at the onset phase, but not at the maintenance phase of movement. SAI was reduced at onset but not at the maintenance phase of movement in both active and surrounding muscles. Our study showed dynamic changes in corticospinal excitability and sensorimotor modulation for active and surrounding muscles in different movement states. SAI does not appear to contribute to motor surround inhibition at the movement onset phase. Also, there seems to be different inhibitory circuit(s) other than SAI for the movement maintenance phase in order to delineate the motor output selectively when corticospinal excitability is increased in both active and surrounding muscles. This study enhances our knowledge of dynamic changes in corticospinal excitability and sensorimotor interaction in different movement states to understand normal and disordered movements. Published by Elsevier Ireland Ltd.

A spatiotemporal profile of visual system activation revealed by current source density analysis in the awake macaque.

PubMed

Schroeder, C E; Mehta, A D; Givre, S J

1998-01-01

We investigated the spatiotemporal activation pattern, produced by one visual stimulus, across cerebral cortical regions in awake monkeys. Laminar profiles of postsynaptic potentials and action potentials were indexed with current source density (CSD) and multiunit activity profiles respectively. Locally, we found contrasting activation profiles in dorsal and ventral stream areas. The former, like V1 and V2, exhibit a 'feedforward' profile, with excitation beginning at the depth of Lamina 4, followed by activation of the extragranular laminae. The latter often displayed a multilaminar/columnar profile, with initial responses distributed across the laminae and reflecting modulation rather than excitation; CSD components were accompanied by either no changes or by suppression of action potentials. System-wide, response latencies indicated a large dorsal/ventral stream latency advantage, which generalizes across a wide range of methods. This predicts a specific temporal ordering of dorsal and ventral stream components of visual analysis, as well as specific patterns of dorsal-ventral stream interaction. Our findings support a hierarchical model of cortical organization that combines serial and parallel elements. Critical in such a model is the recognition that processing within a location typically entails multiple temporal components or 'waves' of activity, driven by input conveyed over heterogeneous pathways from the retina.

Temporal and spatial localization of prediction-error signals in the visual brain.

PubMed

Johnston, Patrick; Robinson, Jonathan; Kokkinakis, Athanasios; Ridgeway, Samuel; Simpson, Michael; Johnson, Sam; Kaufman, Jordy; Young, Andrew W

2017-04-01

It has been suggested that the brain pre-empts changes in the environment through generating predictions, although real-time electrophysiological evidence of prediction violations in the domain of visual perception remain elusive. In a series of experiments we showed participants sequences of images that followed a predictable implied sequence or whose final image violated the implied sequence. Through careful design we were able to use the same final image transitions across predictable and unpredictable conditions, ensuring that any differences in neural responses were due only to preceding context and not to the images themselves. EEG and MEG recordings showed that early (N170) and mid-latency (N300) visual evoked potentials were robustly modulated by images that violated the implied sequence across a range of types of image change (expression deformations, rigid-rotations and visual field location). This modulation occurred irrespective of stimulus object category. Although the stimuli were static images, MEG source reconstruction of the early latency signal (N/M170) localized expectancy violation signals to brain areas associated with motion perception. Our findings suggest that the N/M170 can index mismatches between predicted and actual visual inputs in a system that predicts trajectories based on ongoing context. More generally we suggest that the N/M170 may reflect a "family" of brain signals generated across widespread regions of the visual brain indexing the resolution of top-down influences and incoming sensory data. This has important implications for understanding the N/M170 and investigating how the brain represents context to generate perceptual predictions. Copyright © 2017 Elsevier B.V. All rights reserved.

Act quickly, decide later: long-latency visual processing underlies perceptual decisions but not reflexive behavior.

PubMed

Jolij, Jacob; Scholte, H Steven; van Gaal, Simon; Hodgson, Timothy L; Lamme, Victor A F

2011-12-01

Humans largely guide their behavior by their visual representation of the world. Recent studies have shown that visual information can trigger behavior within 150 msec, suggesting that visually guided responses to external events, in fact, precede conscious awareness of those events. However, is such a view correct? By using a texture discrimination task, we show that the brain relies on long-latency visual processing in order to guide perceptual decisions. Decreasing stimulus saliency leads to selective changes in long-latency visually evoked potential components reflecting scene segmentation. These latency changes are accompanied by almost equal changes in simple RTs and points of subjective simultaneity. Furthermore, we find a strong correlation between individual RTs and the latencies of scene segmentation related components in the visually evoked potentials, showing that the processes underlying these late brain potentials are critical in triggering a response. However, using the same texture stimuli in an antisaccade task, we found that reflexive, but erroneous, prosaccades, but not antisaccades, can be triggered by earlier visual processes. In other words: The brain can act quickly, but decides late. Differences between our study and earlier findings suggesting that action precedes conscious awareness can be explained by assuming that task demands determine whether a fast and unconscious, or a slower and conscious, representation is used to initiate a visually guided response.

Audiovisual Rehabilitation in Hemianopia: A Model-Based Theoretical Investigation

PubMed Central

Magosso, Elisa; Cuppini, Cristiano; Bertini, Caterina

2017-01-01

Hemianopic patients exhibit visual detection improvement in the blind field when audiovisual stimuli are given in spatiotemporally coincidence. Beyond this “online” multisensory improvement, there is evidence of long-lasting, “offline” effects induced by audiovisual training: patients show improved visual detection and orientation after they were trained to detect and saccade toward visual targets given in spatiotemporal proximity with auditory stimuli. These effects are ascribed to the Superior Colliculus (SC), which is spared in these patients and plays a pivotal role in audiovisual integration and oculomotor behavior. Recently, we developed a neural network model of audiovisual cortico-collicular loops, including interconnected areas representing the retina, striate and extrastriate visual cortices, auditory cortex, and SC. The network simulated unilateral V1 lesion with possible spared tissue and reproduced “online” effects. Here, we extend the previous network to shed light on circuits, plastic mechanisms, and synaptic reorganization that can mediate the training effects and functionally implement visual rehabilitation. The network is enriched by the oculomotor SC-brainstem route, and Hebbian mechanisms of synaptic plasticity, and is used to test different training paradigms (audiovisual/visual stimulation in eye-movements/fixed-eyes condition) on simulated patients. Results predict different training effects and associate them to synaptic changes in specific circuits. Thanks to the SC multisensory enhancement, the audiovisual training is able to effectively strengthen the retina-SC route, which in turn can foster reinforcement of the SC-brainstem route (this occurs only in eye-movements condition) and reinforcement of the SC-extrastriate route (this occurs in presence of survived V1 tissue, regardless of eye condition). The retina-SC-brainstem circuit may mediate compensatory effects: the model assumes that reinforcement of this circuit can translate visual stimuli into short-latency saccades, possibly moving the stimuli into visual detection regions. The retina-SC-extrastriate circuit is related to restitutive effects: visual stimuli can directly elicit visual detection with no need for eye movements. Model predictions and assumptions are critically discussed in view of existing behavioral and neurophysiological data, forecasting that other oculomotor compensatory mechanisms, beyond short-latency saccades, are likely involved, and stimulating future experimental and theoretical investigations. PMID:29326578

Audiovisual Rehabilitation in Hemianopia: A Model-Based Theoretical Investigation.

PubMed

Magosso, Elisa; Cuppini, Cristiano; Bertini, Caterina

2017-01-01

Hemianopic patients exhibit visual detection improvement in the blind field when audiovisual stimuli are given in spatiotemporally coincidence. Beyond this "online" multisensory improvement, there is evidence of long-lasting, "offline" effects induced by audiovisual training: patients show improved visual detection and orientation after they were trained to detect and saccade toward visual targets given in spatiotemporal proximity with auditory stimuli. These effects are ascribed to the Superior Colliculus (SC), which is spared in these patients and plays a pivotal role in audiovisual integration and oculomotor behavior. Recently, we developed a neural network model of audiovisual cortico-collicular loops, including interconnected areas representing the retina, striate and extrastriate visual cortices, auditory cortex, and SC. The network simulated unilateral V1 lesion with possible spared tissue and reproduced "online" effects. Here, we extend the previous network to shed light on circuits, plastic mechanisms, and synaptic reorganization that can mediate the training effects and functionally implement visual rehabilitation. The network is enriched by the oculomotor SC-brainstem route, and Hebbian mechanisms of synaptic plasticity, and is used to test different training paradigms (audiovisual/visual stimulation in eye-movements/fixed-eyes condition) on simulated patients. Results predict different training effects and associate them to synaptic changes in specific circuits. Thanks to the SC multisensory enhancement, the audiovisual training is able to effectively strengthen the retina-SC route, which in turn can foster reinforcement of the SC-brainstem route (this occurs only in eye-movements condition) and reinforcement of the SC-extrastriate route (this occurs in presence of survived V1 tissue, regardless of eye condition). The retina-SC-brainstem circuit may mediate compensatory effects: the model assumes that reinforcement of this circuit can translate visual stimuli into short-latency saccades, possibly moving the stimuli into visual detection regions. The retina-SC-extrastriate circuit is related to restitutive effects: visual stimuli can directly elicit visual detection with no need for eye movements. Model predictions and assumptions are critically discussed in view of existing behavioral and neurophysiological data, forecasting that other oculomotor compensatory mechanisms, beyond short-latency saccades, are likely involved, and stimulating future experimental and theoretical investigations.

Are Covert Saccade Functionally Relevant in Vestibular Hypofunction?

PubMed

Hermann, R; Pelisson, D; Dumas, O; Urquizar, Ch; Truy, E; Tilikete, C

2018-06-01

The vestibulo-ocular reflex maintains gaze stabilization during angular or linear head accelerations, allowing adequate dynamic visual acuity. In case of bilateral vestibular hypofunction, patients use saccades to compensate for the reduced vestibulo-ocular reflex function, with covert saccades occurring even during the head displacement. In this study, we questioned whether covert saccades help maintain dynamic visual acuity, and evaluated which characteristic of these saccades are the most relevant to improve visual function. We prospectively included 18 patients with chronic bilateral vestibular hypofunction. Subjects underwent evaluation of dynamic visual acuity in the horizontal plane as well as video recording of their head and eye positions during horizontal head impulse tests in both directions (36 ears tested). Frequency, latency, consistency of covert saccade initiation, and gain of covert saccades as well as residual vestibulo-ocular reflex gain were calculated. We found no correlation between residual vestibulo-ocular reflex gain and dynamic visual acuity. Dynamic visual acuity performance was however positively correlated with the frequency and gain of covert saccades and negatively correlated with covert saccade latency. There was no correlation between consistency of covert saccade initiation and dynamic visual acuity. Even though gaze stabilization in space during covert saccades might be of very short duration, these refixation saccades seem to improve vision in patients with bilateral vestibular hypofunction during angular head impulses. These findings emphasize the need for specific rehabilitation technics that favor the triggering of covert saccades. The physiological origin of covert saccades is discussed.

Normal aging affects movement execution but not visual motion working memory and decision-making delay during cue-dependent memory-based smooth-pursuit.

PubMed

Fukushima, Kikuro; Barnes, Graham R; Ito, Norie; Olley, Peter M; Warabi, Tateo

2014-07-01

Aging affects virtually all functions including sensory/motor and cognitive activities. While retinal image motion is the primary input for smooth-pursuit, its efficiency/accuracy depends on cognitive processes. Elderly subjects exhibit gain decrease during initial and steady-state pursuit, but reports on latencies are conflicting. Using a cue-dependent memory-based smooth-pursuit task, we identified important extra-retinal mechanisms for initial pursuit in young adults including cue information priming and extra-retinal drive components (Ito et al. in Exp Brain Res 229:23-35, 2013). We examined aging effects on parameters for smooth-pursuit using the same tasks. Elderly subjects were tested during three task conditions as previously described: memory-based pursuit, simple ramp-pursuit just to follow motion of a single spot, and popping-out of the correct spot during memory-based pursuit to enhance retinal image motion. Simple ramp-pursuit was used as a task that did not require visual motion working memory. To clarify aging effects, we then compared the results with the previous young subject data. During memory-based pursuit, elderly subjects exhibited normal working memory of cue information. Most movement-parameters including pursuit latencies differed significantly between memory-based pursuit and simple ramp-pursuit and also between young and elderly subjects. Popping-out of the correct spot motion was ineffective for enhancing initial pursuit in elderly subjects. However, the latency difference between memory-based pursuit and simple ramp-pursuit in individual subjects, which includes decision-making delay in the memory task, was similar between the two groups. Our results suggest that smooth-pursuit latencies depend on task conditions and that, although the extra-retinal mechanisms were functional for initial pursuit in elderly subjects, they were less effective.

Mismatch Negativity with Visual-only and Audiovisual Speech

PubMed Central

Ponton, Curtis W.; Bernstein, Lynne E.; Auer, Edward T.

2009-01-01

The functional organization of cortical speech processing is thought to be hierarchical, increasing in complexity and proceeding from primary sensory areas centrifugally. The current study used the mismatch negativity (MMN) obtained with electrophysiology (EEG) to investigate the early latency period of visual speech processing under both visual-only (VO) and audiovisual (AV) conditions. Current density reconstruction (CDR) methods were used to model the cortical MMN generator locations. MMNs were obtained with VO and AV speech stimuli at early latencies (approximately 82-87 ms peak in time waveforms relative to the acoustic onset) and in regions of the right lateral temporal and parietal cortices. Latencies were consistent with bottom-up processing of the visible stimuli. We suggest that a visual pathway extracts phonetic cues from visible speech, and that previously reported effects of AV speech in classical early auditory areas, given later reported latencies, could be attributable to modulatory feedback from visual phonetic processing. PMID:19404730

ShortRead: a bioconductor package for input, quality assessment and exploration of high-throughput sequence data

PubMed Central

Morgan, Martin; Anders, Simon; Lawrence, Michael; Aboyoun, Patrick; Pagès, Hervé; Gentleman, Robert

2009-01-01

Summary: ShortRead is a package for input, quality assessment, manipulation and output of high-throughput sequencing data. ShortRead is provided in the R and Bioconductor environments, allowing ready access to additional facilities for advanced statistical analysis, data transformation, visualization and integration with diverse genomic resources. Availability and Implementation: This package is implemented in R and available at the Bioconductor web site; the package contains a ‘vignette’ outlining typical work flows. Contact: mtmorgan@fhcrc.org PMID:19654119

Perception of linear horizontal self-motion induced by peripheral vision /linearvection/ - Basic characteristics and visual-vestibular interactions

NASA Technical Reports Server (NTRS)

Berthoz, A.; Pavard, B.; Young, L. R.

1975-01-01

The basic characteristics of the sensation of linear horizontal motion have been studied. Objective linear motion was induced by means of a moving cart. Visually induced linear motion perception (linearvection) was obtained by projection of moving images at the periphery of the visual field. Image velocity and luminance thresholds for the appearance of linearvection have been measured and are in the range of those for image motion detection (without sensation of self motion) by the visual system. Latencies of onset are around 1 sec and short term adaptation has been shown. The dynamic range of the visual analyzer as judged by frequency analysis is lower than the vestibular analyzer. Conflicting situations in which visual cues contradict vestibular and other proprioceptive cues show, in the case of linearvection a dominance of vision which supports the idea of an essential although not independent role of vision in self motion perception.

C145 as a short-latency electrophysiological index of cognitive compensation in Alzheimer's disease

PubMed Central

Chapman, Robert M.; Porsteinsson, Anton P.; Gardner, Margaret N.; Mapstone, Mark; McCrary, John W.; Sandoval, Tiffany C.; Guillily, Maria D.; DeGrush, Elizabeth; Reilly, Lindsey A.

2012-01-01

Brain plasticity and cognitive compensation in the elderly are of increasing interest, and Alzheimer's disease (AD) offers an opportunity to elucidate how the brain may overcome damage. We provide neurophysiological evidence of a short-latency ERP component (C145) linked to stimulus relevancy that may reflect cognitive compensation in early-stage Alzheimer's disease (AD). Thirty-six subjects with early-stage, mild AD and 36 like-aged normal elderly (Controls) had their EEG recorded while performing our Number-Letter task, a cognitive/perceptual paradigm that manipulates stimulus relevancies. ERP components, including C145, were extracted from ERPs using Principal Components Analysis. C145 amplitudes and spatial distributions were compared among Controls, AD subjects with high performance on the Number-Letter task, and AD subjects with low performance. Compared to AD subjects, Control subjects showed enhanced C145 processing of visual stimuli in the occipital region where differential processing of relevant stimuli occurred. AD high performers recruited central brain areas in processing task relevancy. Controls and AD low performers did not show a significant task relevancy effect in these areas. We conclude that short-latency ERP components can detect electrophysiological differences in early-stage AD that reflect altered cognition. Differences in C145 amplitudes between AD and normal elderly groups regarding brain locations and types of task effects suggest compensatory mechanisms can occur in the AD brain to overcome loss of normal functionality, and this early compensation may have a profound effect on the cognitive efficiency of AD individuals. PMID:22886016

Common neural structures activated by epidural and transcutaneous lumbar spinal cord stimulation: Elicitation of posterior root-muscle reflexes

PubMed Central

Freundl, Brigitta; Binder, Heinrich; Minassian, Karen

2018-01-01

Epidural electrical stimulation of the lumbar spinal cord is currently regaining momentum as a neuromodulation intervention in spinal cord injury (SCI) to modify dysregulated sensorimotor functions and augment residual motor capacity. There is ample evidence that it engages spinal circuits through the electrical stimulation of large-to-medium diameter afferent fibers within lumbar and upper sacral posterior roots. Recent pilot studies suggested that the surface electrode-based method of transcutaneous spinal cord stimulation (SCS) may produce similar neuromodulatory effects as caused by epidural SCS. Neurophysiological and computer modeling studies proposed that this noninvasive technique stimulates posterior-root fibers as well, likely activating similar input structures to the spinal cord as epidural stimulation. Here, we add a yet missing piece of evidence substantiating this assumption. We conducted in-depth analyses and direct comparisons of the electromyographic (EMG) characteristics of short-latency responses in multiple leg muscles to both stimulation techniques derived from ten individuals with SCI each. Post-activation depression of responses evoked by paired pulses applied either epidurally or transcutaneously confirmed the reflex nature of the responses. The muscle responses to both techniques had the same latencies, EMG peak-to-peak amplitudes, and waveforms, except for smaller responses with shorter onset latencies in the triceps surae muscle group and shorter offsets of the responses in the biceps femoris muscle during epidural stimulation. Responses obtained in three subjects tested with both methods at different time points had near-identical waveforms per muscle group as well as same onset latencies. The present results strongly corroborate the activation of common neural input structures to the lumbar spinal cord—predominantly primary afferent fibers within multiple posterior roots—by both techniques and add to unraveling the basic mechanisms underlying electrical SCS. PMID:29381748

Close similarity between spatiotemporal frequency tunings of human cortical responses and involuntary manual following responses to visual motion.

PubMed

Amano, Kaoru; Kimura, Toshitaka; Nishida, Shin'ya; Takeda, Tsunehiro; Gomi, Hiroaki

2009-02-01

Human brain uses visual motion inputs not only for generating subjective sensation of motion but also for directly guiding involuntary actions. For instance, during arm reaching, a large-field visual motion is quickly and involuntarily transformed into a manual response in the direction of visual motion (manual following response, MFR). Previous attempts to correlate motion-evoked cortical activities, revealed by brain imaging techniques, with conscious motion perception have resulted only in partial success. In contrast, here we show a surprising degree of similarity between the MFR and the population neural activity measured by magnetoencephalography (MEG). We measured the MFR and MEG induced by the same motion onset of a large-field sinusoidal drifting grating with changing the spatiotemporal frequency of the grating. The initial transient phase of these two responses had very similar spatiotemporal tunings. Specifically, both the MEG and MFR amplitudes increased as the spatial frequency was decreased to, at most, 0.05 c/deg, or as the temporal frequency was increased to, at least, 10 Hz. We also found in peak latency a quantitative agreement (approximately 100-150 ms) and correlated changes against spatiotemporal frequency changes between MEG and MFR. In comparison with these two responses, conscious visual motion detection is known to be most sensitive (i.e., have the lowest detection threshold) at higher spatial frequencies and have longer and more variable response latencies. Our results suggest a close relationship between the properties of involuntary motor responses and motion-evoked cortical activity as reflected by the MEG.

Objective instrumental memory and performance tests for evaluation of patients with brain damage: a search for a behavioral diagnostic tool.

PubMed

Harness, B Z; Bental, E; Carmon, A

1976-03-01

Cognition and performance of patients with localized and diffuse brain damage was evaluated through the application of objective perceptual testing. A series of visual perceptual and verbal tests, memory tests, as well as reaction time tasks were administered to the patients by logic programming equipment. In order to avoid a bias due to communicative disorders, all responses were motor, and achievement was scored in terms of correct identification and latencies of response. Previously established norms based on a large sample of non-brain-damaged hospitalized patients served to standardize the performance of the brain-damaged patient since preliminary results showed that age and educational level constitute an important variable affecting performance of the control group. The achievement of brain-damaged patients, corrected for these factors, was impaired significantly in all tests with respect to both recognition and speed of performance. Lateralized effects of brain damage were not significantly demonstrated. However, when the performance was analyzed with respect to the locus of visual input, it was found that patients with right hemispheric lesions showed impairment mainly on perception of figurative material, and that this deficit was more apparent in the left visual field. Conversely, patients with left hemispheric lesions tended to show impairment on perception of visually presented verbal material when the input was delivered to the right visual field.

Effects of Antipsychotic Drugs Haloperidol and Clozapine on Visual Responses of Retinal Ganglion Cells in a Rat Model of Retinitis Pigmentosa.

PubMed

Jensen, Ralph J

2016-12-01

In the P23H rat model of retinitis pigmentosa, the dopamine D2 receptor antagonists sulpiride and eticlopride appear to improve visual responses of retinal ganglion cells (RGCs) by increasing light sensitivity of RGCs and transforming abnormal, long-latency ON-center RGCs into OFF-center cells. Antipsychotic drugs are believed to mediate their therapeutic benefits by blocking D2 receptors. This investigation was conducted to test whether haloperidol (a typical antipsychotic drug) and clozapine (an atypical antipsychotic drug) could similarly alter the light responses of RGCs in the P23H rat retina. Extracellular recordings were made from RGCs in isolated P23H rat retinas. Responses of RGCs to flashes of light were evaluated before and during bath application of a drug. Both haloperidol and clozapine increased light sensitivity of RGCs on average by ∼0.3 log unit. For those ON-center RGCs that exhibit an abnormally long-latency response to the onset of a small spot of light, both haloperidol and clozapine brought out a short-latency OFF response and markedly reduced the long-latency ON response. The selective serotonin 5-HT2A antagonist MDL 100907 had similar effects on RGCs. The effects of haloperidol on light responses of RGCs can be explained by its D2 receptor antagonism. The effects of clozapine on light responses of RGCs on the other hand may largely be due to its 5-HT2A receptor antagonism. Overall, the results suggest that antipsychotic drugs may be useful in improving vision in patients with retinitis pigmentosa.

The sequence of cortical activity inferred by response latency variability in the human ventral pathway of face processing.

PubMed

Lin, Jo-Fu Lotus; Silva-Pereyra, Juan; Chou, Chih-Che; Lin, Fa-Hsuan

2018-04-11

Variability in neuronal response latency has been typically considered caused by random noise. Previous studies of single cells and large neuronal populations have shown that the temporal variability tends to increase along the visual pathway. Inspired by these previous studies, we hypothesized that functional areas at later stages in the visual pathway of face processing would have larger variability in the response latency. To test this hypothesis, we used magnetoencephalographic data collected when subjects were presented with images of human faces. Faces are known to elicit a sequence of activity from the primary visual cortex to the fusiform gyrus. Our results revealed that the fusiform gyrus showed larger variability in the response latency compared to the calcarine fissure. Dynamic and spectral analyses of the latency variability indicated that the response latency in the fusiform gyrus was more variable than in the calcarine fissure between 70 ms and 200 ms after the stimulus onset and between 4 Hz and 40 Hz, respectively. The sequential processing of face information from the calcarine sulcus to the fusiform sulcus was more reliably detected based on sizes of the response variability than instants of the maximal response peaks. With two areas in the ventral visual pathway, we show that the variability in response latency across brain areas can be used to infer the sequence of cortical activity.

Pattern Visual Evoked Potential as a Predictor of Occlusion Therapy for Amblyopia

PubMed Central

Chung, Woosuk; Hong, Samin; Lee, Jong Bok

2008-01-01

Purpose This study was conducted to investigate the role of the pattern visual evoked potential (pVEP) as a predictor of occlusion therapy for patients with strabismic, anisometropic, and isometropic amblyopia. The secondary aim was to compare the characteristics of pVEP between strabismic and anisometropic amblyopia. Methods This retrospective comparative case series included 120 patients who had received occlusion therapy or a glasses prescription for correction of strabismic, anisometropic, and isometropic amblyopia (20 patients had strabismic amblyopia, 41 patients had anisometropic amblyopia, and 59 patients had isometropic amblyopia). For each patient, the value of the P100 latency on pVEP at the time of the initial diagnosis of amblyopia was collected. Subsequently, the P100 latency was compared according to types of amblyopia. Fifty of 120 patients (7 patients with strabismic amblyopia, 21 patients with anisometropic amblyopia, and 22 patients with isometropic amblyopia) who were followed-up for longer than 6 months were divided into two groups based on the value of their P100 latency (Group 1, P100 latency 120 msec or less; Group 2, P100 latency longer than 120 msec.) The amount of visual improvement after occlusion therapy or glasses was compared between two study groups. Results The mean P100 latency was 119.7±25.2 msec in eyes with strabismic amblyopia and 111.9±17.8 msec in eyes with non-strabismic (anisometropic or isometropic) amblyopia (p=0.213). In Group 1, the mean visual improvement after occlusion therapy or glasses was 3.69±2.14 lines on Dr. Hahn's standard test chart; in Group 2, the mean improvement was 2.27±2.21 lines (p=0.023). Conclusions The P100 latency on pVEP at the time of initial diagnosis was significantly related to the visual improvement after occlusion therapy or glasses in patients with strabismic, anisometropic, and isometropic amblyopia. Therefore, it was presumed that patients with a delayed P100 latency might have less visual improvement after occlusion therapy or glasses. In addition, there was no apparent difference in P100 latency between patients with strabismic and non-strabismic (anisometropic or isometropic) amblyopia. PMID:19096243

Pattern visual evoked potential as a predictor of occlusion therapy for amblyopia.

PubMed

Chung, Woosuk; Hong, Samin; Lee, Jong Bok; Han, Sueng-Han

2008-12-01

This study was conducted to investigate the role of the pattern visual evoked potential (pVEP) as a predictor of occlusion therapy for patients with strabismic, anisometropic, and isometropic amblyopia. The secondary aim was to compare the characteristics of pVEP between strabismic and anisometropic amblyopia. This retrospective comparative case series included 120 patients who had received occlusion therapy or a glasses prescription for correction of strabismic, anisometropic, and isometropic amblyopia (20 patients had strabismic amblyopia, 41 patients had anisometropic amblyopia, and 59 patients had isometropic amblyopia). For each patient, the value of the P100 latency on pVEP at the time of the initial diagnosis of amblyopia was collected. Subsequently, the P100 latency was compared according to types of amblyopia. Fifty of 120 patients (7 patients with strabismic amblyopia, 21 patients with anisometropic amblyopia, and 22 patients with isometropic amblyopia) who were followed-up for longer than 6 months were divided into two groups based on the value of their P100 latency (Group 1, P100 latency 120 msec or less; Group 2, P100 latency longer than 120 msec.) The amount of visual improvement after occlusion therapy or glasses was compared between two study groups. The mean P100 latency was 119.7+/-25.2 msec in eyes with strabismic amblyopia and 111.9+/-17.8 msec in eyes with non-strabismic (anisometropic or isometropic) amblyopia (p=0.213). In Group 1, the mean visual improvement after occlusion therapy or glasses was 3.69+/-2.14 lines on Dr. Hahn's standard test chart; in Group 2, the mean improvement was 2.27+/-2.21 lines (p=0.023). The P100 latency on pVEP at the time of initial diagnosis was significantly related to the visual improvement after occlusion therapy or glasses in patients with strabismic, anisometropic, and isometropic amblyopia. Therefore, it was presumed that patients with a delayed P100 latency might have less visual improvement after occlusion therapy or glasses. In addition, there was no apparent difference in P100 latency between patients with strabismic and non-strabismic (anisometropic or isometropic) amblyopia.

Effect of task demands on dual coding of pictorial stimuli.

PubMed

Babbitt, B C

1982-01-01

Recent studies have suggested that verbal labeling of a picture does not occur automatically. Although several experiments using paired-associate tasks produced little evidence indicating the use of a verbal code with picture stimuli, the tasks were probably not sensitive to whether the codes were activated initially. It is possible that verbal labels were activated at input, but not used later in performing the tasks. The present experiment used a color-naming interference task in order to assess, with a more sensitive measure, the amount of verbal coding occurring in response to word or picture input. Subjects named the color of ink in which words were printed following either word or picture input. If verbal labeling of the input occurs, then latency of color naming should increase when the input item and color-naming word are related. The results provided substantial evidence of such verbal activation when the input items were words. However, the presence of verbal activation with picture input was a function of task demands. Activation occurred when a recall memory test was used, but not when a recognition memory test was used. The results support the conclusion that name information (labels) need not be activated during presentation of visual stimuli.

The strength of attentional biases reduces as visual short-term memory load increases

PubMed Central

Shimi, A.

2013-01-01

Despite our visual system receiving irrelevant input that competes with task-relevant signals, we are able to pursue our perceptual goals. Attention enhances our visual processing by biasing the processing of the input that is relevant to the task at hand. The top-down signals enabling these biases are therefore important for regulating lower level sensory mechanisms. In three experiments, we examined whether we apply similar biases to successfully maintain information in visual short-term memory (VSTM). We presented participants with targets alongside distracters and we graded their perceptual similarity to vary the extent to which they competed. Experiments 1 and 2 showed that the more items held in VSTM before the onset of the distracters, the more perceptually distinct the distracters needed to be for participants to retain the target accurately. Experiment 3 extended these behavioral findings by demonstrating that the perceptual similarity between target and distracters exerted a significantly greater effect on occipital alpha amplitudes, depending on the number of items already held in VSTM. The trade-off between VSTM load and target-distracter competition suggests that VSTM and perceptual competition share a partially overlapping mechanism, namely top-down inputs into sensory areas. PMID:23576694

[A delayed motor production of open chains of linear strokes presented visually in static and dynamic modes: a comparison between 9 to 11 years old children and adults].

PubMed

Antonova, A A; Absatova, K A; Korneev, A A; Kurgansky, A V

2015-01-01

The production of drawing movements was studied in 29 right-handed children of 9-to-11 years old. The movements were the sequences of horizontal and vertical linear stokes conjoined at right angle (open polygonal chains) referred to throughout the paper as trajectories. The length of a trajectory varied from 4 to 6. The trajectories were presented visually to a subject in static (linedrawing) and dynamic (moving cursor that leaves no trace) modes. The subjects were asked to draw (copy) a trajectory in response to delayed go-signal (short click) as fast as possible without lifting the pen. The production latency time, the average movement duration along a trajectory segment, and overall number of errors committed by a subject during trajectory production were analyzed. A comparison of children's data with similar data in adults (16 subjects) shows the following. First, a substantial reduction in error rate is observed in the age range between 9 and 11 years old for both static and dynamic modes of trajectory presentation, with children of 11 still committing more error than adults. Second, the averaged movement duration shortens with age while the latency time tends to increase. Third, unlike the adults, the children of 9-11 do not show any difference in latency time between static and dynamic modes of visual presentation of trajectories. The difference in trajectory production between adult and children is attributed to the predominant involvement of on-line programming in children and pre-programming in adults.

Short-term desensitization of fast escape behavior associated with suppression of Mauthner cell activity in larval zebrafish.

PubMed

Takahashi, Megumi; Inoue, Maya; Tanimoto, Masashi; Kohashi, Tsunehiko; Oda, Yoichi

2017-08-01

Escape is among the simplest animal behaviors employed to study the neural mechanisms underlying learning. Teleost fishes exhibit behavioral learning of fast escape initiated with a C-shaped body bend (C-start). C-starts are subdivided into short-latency (SLC) and long-latency (LLC) types in larval zebrafish. Whether these two can be separately modified, and the neural correlates of this modification, however, remains undetermined. We thus performed Ca 2+ imaging of Mauthner (M-) cells, a pair of giant hindbrain neurons constituting a core element of SLC circuit, during behavioral learning in larval zebrafish. The Ca 2+ response corresponding to a single spiking of the M-cells was coupled with SLCs but not LLCs. Conditioning with a repeated weak sound at subthreshold intensity to elicit C-starts selectively suppressed SLC occurrence for 10min without affecting LLC responsiveness. The short-term desensitization of SLC was associated with the suppression of M-cell activity, suggesting that changes in single neuron responsiveness mediate behavioral learning. The conditioning did not affect the acoustically evoked mechanotransduction of inner ear hair cells, further suggesting plastic change in transmission efficacy within the auditory input circuit between the hair cells and the M-cell. Copyright © 2017 Elsevier Ireland Ltd and Japan Neuroscience Society. All rights reserved.

Correlation of pattern reversal visual evoked potential parameters with the pattern standard deviation in primary open angle glaucoma.

PubMed

Kothari, Ruchi; Bokariya, Pradeep; Singh, Ramji; Singh, Smita; Narang, Purvasha

2014-01-01

To evaluate whether glaucomatous visual field defect particularly the pattern standard deviation (PSD) of Humphrey visual field could be associated with visual evoked potential (VEP) parameters of patients having primary open angle glaucoma (POAG). Visual field by Humphrey perimetry and simultaneous recordings of pattern reversal visual evoked potential (PRVEP) were assessed in 100 patients with POAG. The stimulus configuration for VEP recordings consisted of the transient pattern reversal method in which a black and white checker board pattern was generated (full field) and displayed on VEP monitor (colour 14″) by an electronic pattern regenerator inbuilt in an evoked potential recorder (RMS EMG EP MARK II). The results of our study indicate that there is a highly significant (P<0.001) negative correlation of P100 amplitude and a statistically significant (P<0.05) positive correlation of N70 latency, P100 latency and N155 latency with the PSD of Humphrey visual field in the subjects of POAG in various age groups as evaluated by Student's t-test. Prolongation of VEP latencies were mirrored by a corresponding increase of PSD values. Conversely, as PSD increases the magnitude of VEP excursions were found to be diminished.

Visual mental image generation does not overlap with visual short-term memory: a dual-task interference study.

PubMed

Borst, Gregoire; Niven, Elaine; Logie, Robert H

2012-04-01

Visual mental imagery and working memory are often assumed to play similar roles in high-order functions, but little is known of their functional relationship. In this study, we investigated whether similar cognitive processes are involved in the generation of visual mental images, in short-term retention of those mental images, and in short-term retention of visual information. Participants encoded and recalled visually or aurally presented sequences of letters under two interference conditions: spatial tapping or irrelevant visual input (IVI). In Experiment 1, spatial tapping selectively interfered with the retention of sequences of letters when participants generated visual mental images from aural presentation of the letter names and when the letters were presented visually. In Experiment 2, encoding of the sequences was disrupted by both interference tasks. However, in Experiment 3, IVI interfered with the generation of the mental images, but not with their retention, whereas spatial tapping was more disruptive during retention than during encoding. Results suggest that the temporary retention of visual mental images and of visual information may be supported by the same visual short-term memory store but that this store is not involved in image generation.

Stretch reflex excitability of the anti-gravity ankle extensor muscle in elderly humans.

PubMed

Kawashima, N; Nakazawa, K; Yamamoto, S-I; Nozaki, D; Akai, M; Yano, H

2004-01-01

To examine whether the stretch reflex excitability of the soleus muscle changes with age, stretch reflexes at rest (REST) and during weak voluntary contractions (ACT) were elicited in 18 older and 14 younger subjects. The amplitude of the stretch reflex responses and gain, defined as the gradient of the regression line for the relation between stretch reflex responses against the angular velocity of the applied perturbation, were evaluated in each short-latency (M1) and two long-latency components (M2 and M3). It was found that in the older group, both the amplitude and gain of the M1 component did not change from the REST to the ACT conditions, whereas in the younger group both variables significantly increased from the REST to ACT conditions. The latency of the M1 component was significantly shorter under the REST condition (older vs. younger: 51.8 +/- 7.37 vs. 55.1 +/- 8.69 ms), while no group differences were found in those variables under the ACT condition, suggesting that the muscle-tendon complexes of SOL muscles of the older subjects were less elastic and had less slack, probably due to age-related histochemical alterations. Further, the Hoffman reflex (H-reflex), elicited during the REST condition in 10 older and 11 younger subjects showed no significant differences, suggesting that the soleus motoneuron response to the Ia input was comparable between the two subject groups. The histochemical alterations occurring with the ageing process might augment the short-latency stretch reflex in the SOL muscle without enhancement of motoneuronal excitability, and this effect might be masked when the muscle is voluntarily activated.

Absence of Visual Input Results in the Disruption of Grid Cell Firing in the Mouse.

PubMed

Chen, Guifen; Manson, Daniel; Cacucci, Francesca; Wills, Thomas Joseph

2016-09-12

Grid cells are spatially modulated neurons within the medial entorhinal cortex whose firing fields are arranged at the vertices of tessellating equilateral triangles [1]. The exquisite periodicity of their firing has led to the suggestion that they represent a path integration signal, tracking the organism's position by integrating speed and direction of movement [2-10]. External sensory inputs are required to reset any errors that the path integrator would inevitably accumulate. Here we probe the nature of the external sensory inputs required to sustain grid firing, by recording grid cells as mice explore familiar environments in complete darkness. The absence of visual cues results in a significant disruption of grid cell firing patterns, even when the quality of the directional information provided by head direction cells is largely preserved. Darkness alters the expression of velocity signaling within the entorhinal cortex, with changes evident in grid cell firing rate and the local field potential theta frequency. Short-term (<1.5 s) spike timing relationships between grid cell pairs are preserved in the dark, indicating that network patterns of excitatory and inhibitory coupling between grid cells exist independently of visual input and of spatially periodic firing. However, we find no evidence of preserved hexagonal symmetry in the spatial firing of single grid cells at comparable short timescales. Taken together, these results demonstrate that visual input is required to sustain grid cell periodicity and stability in mice and suggest that grid cells in mice cannot perform accurate path integration in the absence of reliable visual cues. Copyright © 2016 The Author(s). Published by Elsevier Ltd.. All rights reserved.

[Visual perception of Japanese characters and complicated figures: developmental changes of visual P300 event-related potentials].

PubMed

Sata, Yoshimi; Inagaki, Masumi; Shirane, Seiko; Kaga, Makiko

2002-07-01

In order to evaluate developmental change of visual perception, the P300 event-related potentials (ERPs) of visual oddball task were recorded in 34 healthy volunteers ranging from 7 to 37 years of age. The latency and amplitude of visual P300 in response to the Japanese ideogram stimuli (a pair of familiar Kanji characters or unfamiliar Kanji characters) and a pair of meaningless complicated figures were measured. Visual P300 was dominant at parietal area in almost all subjects. There was a significant difference of P300 latency among the three tasks. Reaction time to the both kind of Kanji tasks were significantly shorter than those to the complicated figure task. P300 latencies to the familiar Kanji, unfamiliar Kanji and figure stimuli decreased until 25.8, 26.9 and 29.4 years of age, respectively, and regression analysis revealed that a positive quadratic function could be fitted to the data. Around 9 years of age, the P300 latency/age slope was largest in the unfamiliar Kanji task. These findings suggest that visual P300 development depends on both the complexity of the tasks and specificity of the stimuli, which might reflect the variety in visual information processing.

Sensor Spatial Distortion, Visual Latency, and Update Rate Effects on 3D Tracking in Virtual Environments

NASA Technical Reports Server (NTRS)

Ellis, S. R.; Adelstein, B. D.; Baumeler, S.; Jense, G. J.; Jacoby, R. H.; Trejo, Leonard (Technical Monitor)

1998-01-01

Several common defects that we have sought to minimize in immersing virtual environments are: static sensor spatial distortion, visual latency, and low update rates. Human performance within our environments during large amplitude 3D tracking was assessed by objective and subjective methods in the presence and absence of these defects. Results show that 1) removal of our relatively small spatial sensor distortion had minor effects on the tracking activity, 2) an Adapted Cooper-Harper controllability scale proved the most sensitive subjective indicator of the degradation of dynamic fidelity caused by increasing latency and decreasing frame rates, and 3) performance, as measured by normalized RMS tracking error or subjective impressions, was more markedly influenced by changing visual latency than by update rate.

Attentional sensitivity and asymmetries of vertical saccade generation in monkey

NASA Technical Reports Server (NTRS)

Zhou, Wu; King, W. M.; Shelhamer, M. J. (Principal Investigator)

2002-01-01

The first goal of this study was to systematically document asymmetries in vertical saccade generation. We found that visually guided upward saccades have not only shorter latencies, but higher peak velocities, shorter durations and smaller errors. The second goal was to identify possible mechanisms underlying the asymmetry in vertical saccade latencies. Based on a recent model of saccade generation, three stages of saccade generation were investigated using specific behavioral paradigms: attention shift to a visual target (CUED paradigm), initiation of saccade generation (GAP paradigm) and release of the motor command to execute the saccade (DELAY paradigm). Our results suggest that initiation of a saccade (or "ocular disengagement") and its motor release contribute little to the asymmetry in vertical saccade latency. However, analysis of saccades made in the CUED paradigm indicated that it took less time to shift attention to a target in the upper visual field than to a target in the lower visual field. These data suggest that higher attentional sensitivity to targets in the upper visual field may contribute to shorter latencies of upward saccades.

Correlation between electrical and hemodynamic responses during visual stimulation with graded contrasts

NASA Astrophysics Data System (ADS)

Si, Juanning; Zhang, Xin; Li, Yuejun; Zhang, Yujin; Zuo, Nianming; Jiang, Tianzi

2016-09-01

Brain functional activity involves complex cellular, metabolic, and vascular chain reactions, making it difficult to comprehend. Electroencephalography (EEG) and functional near infrared spectroscopy (fNIRS) have been combined into a multimodal neuroimaging method that captures both electrophysiological and hemodynamic information to explore the spatiotemporal characteristics of brain activity. Because of the significance of visually evoked functional activity in clinical applications, numerous studies have explored the amplitude of the visual evoked potential (VEP) to clarify its relationship with the hemodynamic response. However, relatively few studies have investigated the influence of latency, which has been frequently used to diagnose visual diseases, on the hemodynamic response. Moreover, because the latency and the amplitude of VEPs have different roles in coding visual information, investigating the relationship between latency and the hemodynamic response should be helpful. In this study, checkerboard reversal tasks with graded contrasts were used to evoke visual functional activity. Both EEG and fNIRS were employed to investigate the relationship between neuronal electrophysiological activities and the hemodynamic responses. The VEP amplitudes were linearly correlated with the hemodynamic response, but the VEP latency showed a negative linear correlation with the hemodynamic response.

Whole-field visual motion drives swimming in larval zebrafish via a stochastic process

PubMed Central

Portugues, Ruben; Haesemeyer, Martin; Blum, Mirella L.; Engert, Florian

2015-01-01

ABSTRACT Caudo-rostral whole-field visual motion elicits forward locomotion in many organisms, including larval zebrafish. Here, we investigate the dependence on the latency to initiate this forward swimming as a function of the speed of the visual motion. We show that latency is highly dependent on speed for slow speeds (<10 mm s−1) and then plateaus for higher values. Typical latencies are >1.5 s, which is much longer than neuronal transduction processes. What mechanisms underlie these long latencies? We propose two alternative, biologically inspired models that could account for this latency to initiate swimming: an integrate and fire model, which is history dependent, and a stochastic Poisson model, which has no history dependence. We use these models to predict the behavior of larvae when presented with whole-field motion of varying speed and find that the stochastic process shows better agreement with the experimental data. Finally, we discuss possible neuronal implementations of these models. PMID:25792753

Whole-field visual motion drives swimming in larval zebrafish via a stochastic process.

PubMed

Portugues, Ruben; Haesemeyer, Martin; Blum, Mirella L; Engert, Florian

2015-05-01

Caudo-rostral whole-field visual motion elicits forward locomotion in many organisms, including larval zebrafish. Here, we investigate the dependence on the latency to initiate this forward swimming as a function of the speed of the visual motion. We show that latency is highly dependent on speed for slow speeds (<10 mm s(-1)) and then plateaus for higher values. Typical latencies are >1.5 s, which is much longer than neuronal transduction processes. What mechanisms underlie these long latencies? We propose two alternative, biologically inspired models that could account for this latency to initiate swimming: an integrate and fire model, which is history dependent, and a stochastic Poisson model, which has no history dependence. We use these models to predict the behavior of larvae when presented with whole-field motion of varying speed and find that the stochastic process shows better agreement with the experimental data. Finally, we discuss possible neuronal implementations of these models. © 2015. Published by The Company of Biologists Ltd.

Effects of Length of Retention Interval on Proactive Interference in Short-Term Visual Memory

ERIC Educational Resources Information Center

Meudell, Peter R.

1977-01-01

These experiments show two things: (a) In visual memory, long-term interference on a current item from items previously stored only seems to occur when the current item's retention interval is relatively long, and (b) the visual code appears to decay rapidly, reaching asymptote within 3 seconds of input in the presence of an interpolated task.…

Primary visual response (M100) delays in adolescents with FASD as measured with MEG.

PubMed

Coffman, Brian A; Kodituwakku, Piyadasa; Kodituwakku, Elizabeth L; Romero, Lucinda; Sharadamma, Nirupama Muniswamy; Stone, David; Stephen, Julia M

2013-11-01

Fetal alcohol spectrum disorders (FASD) are debilitating, with effects of prenatal alcohol exposure persisting into adolescence and adulthood. Complete characterization of FASD is crucial for the development of diagnostic tools and intervention techniques to decrease the high cost to individual families and society of this disorder. In this experiment, we investigated visual system deficits in adolescents (12-21 years) diagnosed with an FASD by measuring the latency of patients' primary visual M100 responses using MEG. We hypothesized that patients with FASD would demonstrate delayed primary visual responses compared to controls. M100 latencies were assessed both for FASD patients and age-matched healthy controls for stimuli presented at the fovea (central stimulus) and at the periphery (peripheral stimuli; left or right of the central stimulus) in a saccade task requiring participants to direct their attention and gaze to these stimuli. Source modeling was performed on visual responses to the central and peripheral stimuli and the latency of the first prominent peak (M100) in the occipital source timecourse was identified. The peak latency of the M100 responses were delayed in FASD patients for both stimulus types (central and peripheral), but the difference in latency of primary visual responses to central vs. peripheral stimuli was significant only in FASD patients, indicating that, while FASD patients' visual systems are impaired in general, this impairment is more pronounced in the periphery. These results suggest that basic sensory deficits in this population may contribute to sensorimotor integration deficits described previously in this disorder. Copyright © 2012 Wiley Periodicals, Inc.

Is that a belt or a snake? object attentional selection affects the early stages of visual sensory processing

PubMed Central

2012-01-01

Background There is at present crescent empirical evidence deriving from different lines of ERPs research that, unlike previously observed, the earliest sensory visual response, known as C1 component or P/N80, generated within the striate cortex, might be modulated by selective attention to visual stimulus features. Up to now, evidence of this modulation has been related to space location, and simple features such as spatial frequency, luminance, and texture. Additionally, neurophysiological conditions, such as emotion, vigilance, the reflexive or voluntary nature of input attentional selection, and workload have also been related to C1 modulations, although at least the workload status has received controversial indications. No information is instead available, at present, for objects attentional selection. Methods In this study object- and space-based attention mechanisms were conjointly investigated by presenting complex, familiar shapes of artefacts and animals, intermixed with distracters, in different tasks requiring the selection of a relevant target-category within a relevant spatial location, while ignoring the other shape categories within this location, and, overall, all the categories at an irrelevant location. EEG was recorded from 30 scalp electrode sites in 21 right-handed participants. Results and Conclusions ERP findings showed that visual processing was modulated by both shape- and location-relevance per se, beginning separately at the latency of the early phase of a precocious negativity (60-80 ms) at mesial scalp sites consistent with the C1 component, and a positivity at more lateral sites. The data also showed that the attentional modulation progressed conjointly at the latency of the subsequent P1 (100-120 ms) and N1 (120-180 ms), as well as later-latency components. These findings support the views that (1) V1 may be precociously modulated by direct top-down influences, and participates to object, besides simple features, attentional selection; (2) object spatial and non-spatial features selection might begin with an early, parallel detection of a target object in the visual field, followed by the progressive focusing of spatial attention onto the location of an actual target for its identification, somehow in line with neural mechanisms reported in the literature as "object-based space selection", or with those proposed for visual search. PMID:22300540

Efficient visual object and word recognition relies on high spatial frequency coding in the left posterior fusiform gyrus: evidence from a case-series of patients with ventral occipito-temporal cortex damage.

PubMed

Roberts, Daniel J; Woollams, Anna M; Kim, Esther; Beeson, Pelagie M; Rapcsak, Steven Z; Lambon Ralph, Matthew A

2013-11-01

Recent visual neuroscience investigations suggest that ventral occipito-temporal cortex is retinotopically organized, with high acuity foveal input projecting primarily to the posterior fusiform gyrus (pFG), making this region crucial for coding high spatial frequency information. Because high spatial frequencies are critical for fine-grained visual discrimination, we hypothesized that damage to the left pFG should have an adverse effect not only on efficient reading, as observed in pure alexia, but also on the processing of complex non-orthographic visual stimuli. Consistent with this hypothesis, we obtained evidence that a large case series (n = 20) of patients with lesions centered on left pFG: 1) Exhibited reduced sensitivity to high spatial frequencies; 2) demonstrated prolonged response latencies both in reading (pure alexia) and object naming; and 3) were especially sensitive to visual complexity and similarity when discriminating between novel visual patterns. These results suggest that the patients' dual reading and non-orthographic recognition impairments have a common underlying mechanism and reflect the loss of high spatial frequency visual information normally coded in the left pFG.

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.

Seeing the hand while reaching speeds up on-line responses to a sudden change in target position

PubMed Central

Reichenbach, Alexandra; Thielscher, Axel; Peer, Angelika; Bülthoff, Heinrich H; Bresciani, Jean-Pierre

2009-01-01

Goal-directed movements are executed under the permanent supervision of the central nervous system, which continuously processes sensory afferents and triggers on-line corrections if movement accuracy seems to be compromised. For arm reaching movements, visual information about the hand plays an important role in this supervision, notably improving reaching accuracy. Here, we tested whether visual feedback of the hand affects the latency of on-line responses to an external perturbation when reaching for a visual target. Two types of perturbation were used: visual perturbation consisted in changing the spatial location of the target and kinesthetic perturbation in applying a force step to the reaching arm. For both types of perturbation, the hand trajectory and the electromyographic (EMG) activity of shoulder muscles were analysed to assess whether visual feedback of the hand speeds up on-line corrections. Without visual feedback of the hand, on-line responses to visual perturbation exhibited the longest latency. This latency was reduced by about 10% when visual feedback of the hand was provided. On the other hand, the latency of on-line responses to kinesthetic perturbation was independent of the availability of visual feedback of the hand. In a control experiment, we tested the effect of visual feedback of the hand on visual and kinesthetic two-choice reaction times – for which coordinate transformation is not critical. Two-choice reaction times were never facilitated by visual feedback of the hand. Taken together, our results suggest that visual feedback of the hand speeds up on-line corrections when the position of the visual target with respect to the body must be re-computed during movement execution. This facilitation probably results from the possibility to map hand- and target-related information in a common visual reference frame. PMID:19675067

A special role for binocular visual input during development and as a component of occlusion therapy for treatment of amblyopia.

PubMed

Mitchell, Donald E

2008-01-01

To review work on animal models of deprivation amblyopia that points to a special role for binocular visual input in the development of spatial vision and as a component of occlusion (patching) therapy for amblyopia. The studies reviewed employ behavioural methods to measure the effects of various early experiential manipulations on the development of the visual acuity of the two eyes. Short periods of concordant binocular input, if continuous, can offset much longer daily periods of monocular deprivation to allow the development of normal visual acuity in both eyes. It appears that the visual system does not weigh all visual input equally in terms of its ability to impact on the development of vision but instead places greater weight on concordant binocular exposure. Experimental models of patching therapy for amblyopia imposed on animals in which amblyopia had been induced by a prior period of early monocular deprivation, indicate that the benefits of patching therapy may be only temporary and decline rapidly after patching is discontinued. However, when combined with critical amounts of binocular visual input each day, the benefits of patching can be both heightened and made permanent. Taken together with demonstrations of retained binocular connections in the visual cortex of monocularly deprived animals, a strong argument is made for inclusion of specific training of stereoscopic vision for part of the daily periods of binocular exposure that should be incorporated as part of any patching protocol for amblyopia.

Context effects on smooth pursuit and manual interception of a disappearing target.

PubMed

Kreyenmeier, Philipp; Fooken, Jolande; Spering, Miriam

2017-07-01

In our natural environment, we interact with moving objects that are surrounded by richly textured, dynamic visual contexts. Yet most laboratory studies on vision and movement show visual objects in front of uniform gray backgrounds. Context effects on eye movements have been widely studied, but it is less well known how visual contexts affect hand movements. Here we ask whether eye and hand movements integrate motion signals from target and context similarly or differently, and whether context effects on eye and hand change over time. We developed a track-intercept task requiring participants to track the initial launch of a moving object ("ball") with smooth pursuit eye movements. The ball disappeared after a brief presentation, and participants had to intercept it in a designated "hit zone." In two experiments ( n = 18 human observers each), the ball was shown in front of a uniform or a textured background that either was stationary or moved along with the target. Eye and hand movement latencies and speeds were similarly affected by the visual context, but eye and hand interception (eye position at time of interception, and hand interception timing error) did not differ significantly between context conditions. Eye and hand interception timing errors were strongly correlated on a trial-by-trial basis across all context conditions, highlighting the close relation between these responses in manual interception tasks. Our results indicate that visual contexts similarly affect eye and hand movements but that these effects may be short-lasting, affecting movement trajectories more than movement end points. NEW & NOTEWORTHY In a novel track-intercept paradigm, human observers tracked a briefly shown object moving across a textured, dynamic context and intercepted it with their finger after it had disappeared. Context motion significantly affected eye and hand movement latency and speed, but not interception accuracy; eye and hand position at interception were correlated on a trial-by-trial basis. Visual context effects may be short-lasting, affecting movement trajectories more than movement end points. Copyright © 2017 the American Physiological Society.

Shades of grey; Assessing the contribution of the magno- and parvocellular systems to neural processing of the retinal input in the human visual system from the influence of neural population size and its discharge activity on the VEP.

PubMed

Marcar, Valentine L; Baselgia, Silvana; Lüthi-Eisenegger, Barbara; Jäncke, Lutz

2018-03-01

Retinal input processing in the human visual system involves a phasic and tonic neural response. We investigated the role of the magno- and parvocellular systems by comparing the influence of the active neural population size and its discharge activity on the amplitude and latency of four VEP components. We recorded the scalp electric potential of 20 human volunteers viewing a series of dartboard images presented as a pattern reversing and pattern on-/offset stimulus. These patterns were designed to vary both neural population size coding the temporal- and spatial luminance contrast property and the discharge activity of the population involved in a systematic manner. When the VEP amplitude reflected the size of the neural population coding the temporal luminance contrast property of the image, the influence of luminance contrast followed the contrast response function of the parvocellular system. When the VEP amplitude reflected the size of the neural population responding to the spatial luminance contrast property the image, the influence of luminance contrast followed the contrast response function of the magnocellular system. The latencies of the VEP components examined exhibited the same behavior across our stimulus series. This investigation demonstrates the complex interplay of the magno- and parvocellular systems on the neural response as captured by the VEP. It also demonstrates a linear relationship between stimulus property, neural response, and the VEP and reveals the importance of feedback projections in modulating the ongoing neural response. In doing so, it corroborates the conclusions of our previous study.

Physical Feature Encoding and Word Recognition Abilities Are Altered in Children with Intractable Epilepsy: Preliminary Neuromagnetic Evidence

PubMed Central

Pardos, Maria; Korostenskaja, Milena; Xiang, Jing; Fujiwara, Hisako; Lee, Ki H.; Horn, Paul S.; Byars, Anna; Vannest, Jennifer; Wang, Yingying; Hemasilpin, Nat; Rose, Douglas F.

2015-01-01

Objective evaluation of language function is critical for children with intractable epilepsy under consideration for epilepsy surgery. The purpose of this preliminary study was to evaluate word recognition in children with intractable epilepsy by using magnetoencephalography (MEG). Ten children with intractable epilepsy (M/F 6/4, mean ± SD 13.4 ± 2.2 years) were matched on age and sex to healthy controls. Common nouns were presented simultaneously from visual and auditory sensory inputs in “match” and “mismatch” conditions. Neuromagnetic responses M1, M2, M3, M4, and M5 with latencies of ~100 ms, ~150 ms, ~250 ms, ~350 ms, and ~450 ms, respectively, elicited during the “match” condition were identified. Compared to healthy children, epilepsy patients had both significantly delayed latency of the M1 and reduced amplitudes of M3 and M5 responses. These results provide neurophysiologic evidence of altered word recognition in children with intractable epilepsy. PMID:26146459

Visual working memory modulates low-level saccade target selection: Evidence from rapidly generated saccades in the global effect paradigm

PubMed Central

Hollingworth, Andrew; Matsukura, Michi; Luck, Steven J.

2013-01-01

In three experiments, we examined the influence of visual working memory (VWM) on the metrics of saccade landing position in a global effect paradigm. Participants executed a saccade to the more eccentric object in an object pair appearing on the horizontal midline, to the left or right of central fixation. While completing the saccade task, participants maintained a color in VWM for an unrelated memory task. Either the color of the saccade target matched the memory color (target match), the color of the distractor matched the memory color (distractor match), or the colors of neither object matched the memory color (no match). In the no-match condition, saccades tended to land at the midpoint between the two objects: the global, or averaging, effect. However, when one of the two objects matched VWM, the distribution of landing position shifted toward the matching object, both for target match and for distractor match. VWM modulation of landing position was observed even for the fastest quartile of saccades, with a mean latency as low as 112 ms. Effects of VWM on such rapidly generated saccades, with latencies in the express-saccade range, indicate that VWM interacts with the initial sweep of visual sensory processing, modulating perceptual input to oculomotor systems and thereby biasing oculomotor selection. As a result, differences in memory match produce effects on landing position similar to the effects generated by differences in physical salience. PMID:24190909

Gamma oscillation maintains stimulus structure-dependent synchronization in cat visual cortex.

PubMed

Samonds, Jason M; Bonds, A B

2005-01-01

Visual cortical cells demonstrate both oscillation and synchronization, although the underlying causes and functional significance of these behaviors remain uncertain. We simultaneously recorded single-unit activity with microelectrode arrays in supragranular layers of area 17 of cats paralyzed and anesthetized with propofol and N(2)O. Rate-normalized autocorrelograms of 24 cells reveal bursting (100%) and gamma oscillation (63%). Renewal density analysis, used to explore the source of oscillation, suggests a contribution from extrinsic influences such as feedback. However, a bursting refractory period, presumably membrane-based, could also encourage oscillatory firing. When we investigated the source of synchronization for 60 cell pairs we found only moderate correlation of synchrony with bursts and oscillation. We did, nonetheless, discover a possible functional role for oscillation. In all cases of cross-correlograms that exhibited oscillation, the strength of the synchrony was maintained throughout the stimulation period. When no oscillation was apparent, 75% of the cell pairs showed decay in their synchronization. The synchrony between cells is strongly dependent on similar response onset latencies. We therefore propose that structured input, which yields tight organization of latency, is a more likely candidate for the source of synchronization than oscillation. The reliable synchrony at response onset could be driven by spatial and temporal correlation of the stimulus that is preserved through the earlier stages of the visual system. Oscillation then contributes to maintenance of the synchrony to enhance reliable transmission of the information for higher cognitive processing.

Haptic Cues for Balance: Use of a Cane Provides Immediate Body Stabilization

PubMed Central

Sozzi, Stefania; Crisafulli, Oscar; Schieppati, Marco

2017-01-01

Haptic cues are important for balance. Knowledge of the temporal features of their effect may be crucial for the design of neural prostheses. Touching a stable surface with a fingertip reduces body sway in standing subjects eyes closed (EC), and removal of haptic cue reinstates a large sway pattern. Changes in sway occur rapidly on changing haptic conditions. Here, we describe the effects and time-course of stabilization produced by a haptic cue derived from a walking cane. We intended to confirm that cane use reduces body sway, to evaluate the effect of vision on stabilization by a cane, and to estimate the delay of the changes in body sway after addition and withdrawal of haptic input. Seventeen healthy young subjects stood in tandem position on a force platform, with eyes closed or open (EO). They gently lowered the cane onto and lifted it from a second force platform. Sixty trials per direction of haptic shift (Touch → NoTouch, T-NT; NoTouch → Touch, NT-T) and visual condition (EC-EO) were acquired. Traces of Center of foot Pressure (CoP) and the force exerted by cane were filtered, rectified, and averaged. The position in space of a reflective marker positioned on the cane tip was also acquired by an optoelectronic device. Cross-correlation (CC) analysis was performed between traces of cane tip and CoP displacement. Latencies of changes in CoP oscillation in the frontal plane EC following the T-NT and NT-T haptic shift were statistically estimated. The CoP oscillations were larger in EC than EO under both T and NT (p < 0.001) and larger during NT than T conditions (p < 0.001). Haptic-induced effect under EC (Romberg quotient NT/T ~ 1.2) was less effective than that of vision under NT condition (EC/EO ~ 1.5) (p < 0.001). With EO cane had little effect. Cane displacement lagged CoP displacement under both EC and EO. Latencies to changes in CoP oscillations were longer after addition (NT-T, about 1.6 s) than withdrawal (T-NT, about 0.9 s) of haptic input (p < 0.001). These latencies were similar to those occurring on fingertip touch, as previously shown. Overall, data speak in favor of substantial equivalence of the haptic information derived from both “direct” fingertip contact and “indirect” contact with the floor mediated by the cane. Cane, finger and visual inputs would be similarly integrated in the same neural centers for balance control. Haptic input from a walking aid and its processing time should be considered when designing prostheses for locomotion. PMID:29311785

Evaluation of visual field parameters in patients with chronic obstructive pulmonary disease.

PubMed

Demir, Helin Deniz; Inönü, Handan; Kurt, Semiha; Doruk, Sibel; Aydın, Erdinc; Etikan, Ilker

2012-08-01

To evaluate the effects of chronic obstructive pulmonary disease (COPD) on retina and optic nerve. Thirty-eight patients with COPD and 29 healthy controls, totally 67 subjects, were included in the study. Visual evoked potentials (VEP) and visual field assessment (both standard achromatic perimetry (SAP) and short-wavelength automated perimetry (SWAP)) were performed on each subject after ophthalmological, neurological and pulmonary examinations. Mean deviation (MD), pattern standard deviation (PSD) and corrected pattern standard deviation (CPSD) were significantly different between patient and control groups as for both SAP and SWAP measurements (p = 0.001, 0.019, 0.009 and p = 0.004,0.019, 0.031, respectively). Short-term fluctuation (SF) was not statistically different between the study and the control groups (p = 0.874 and 0.694, respectively). VEP P100 latencies were significantly different between patients with COPD and the controls (p = 0.019). Chronic obstructive pulmonary disease is a systemic disease, and hypoxia in COPD seems to affect the retina and the optic nerve. © 2012 The Authors. Acta Ophthalmologica © 2012 Acta Ophthalmologica Scandinavica Foundation.

Visual and Auditory Memory: Relationships to Reading Achievement.

ERIC Educational Resources Information Center

Bruning, Roger H.; And Others

1978-01-01

Good and poor readers' visual and auditory memory were tested. No group differences existed for single mode presentation in recognition frequency or latency. With multimodal presentation, good readers had faster latencies. Dual coding and self-terminating memory search hypotheses were supported. Implications for the reading process and reading…

Reduced Short- and Long-Latency Afferent Inhibition Following Acute Muscle Pain: A Potential Role in the Recovery of Motor Output.

PubMed

Burns, Emma; Chipchase, Lucinda Sian; Schabrun, Siobhan May

2016-02-13

. Corticomotor output is reduced in response to acute muscle pain, yet the mechanisms that underpin this effect remain unclear. Here the authors investigate the effect of acute muscle pain on short-latency afferent inhibition, long-latency afferent inhibition, and long-interval intra-cortical inhibition to determine whether these mechanisms could plausibly contribute to reduced motor output in pain. . Observational same subject pre-post test design. . Neurophysiology research laboratory. . Healthy, right-handed human volunteers (n = 22, 9 male; mean age ± standard deviation, 22.6 ± 7.8 years). . Transcranial magnetic stimulation was used to assess corticomotor output, short-latency afferent inhibition, long-latency afferent inhibition, and long-interval intra-cortical inhibition before, during, immediately after, and 15 minutes after hypertonic saline infusion into right first dorsal interosseous muscle. Pain intensity and quality were recorded using an 11-point numerical rating scale and the McGill Pain Questionnaire. . Compared with baseline, corticomotor output was reduced at all time points (p = 0.001). Short-latency afferent inhibition was reduced immediately after (p = 0.039), and long-latency afferent inhibition 15 minutes after (p = 0.035), the resolution of pain. Long-interval intra-cortical inhibition was unchanged at any time point (p = 0.36). . These findings suggest short- and long-latency afferent inhibition, mechanisms thought to reflect the integration of sensory information with motor output at the cortex, are reduced following acute muscle pain. Although the functional relevance is unclear, the authors hypothesize a reduction in these mechanisms may contribute to the restoration of normal motor output after an episode of acute muscle pain. © 2016 American Academy of Pain Medicine. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Spatial attention during saccade decisions.

PubMed

Jonikaitis, Donatas; Klapetek, Anna; Deubel, Heiner

2017-07-01

Behavioral measures of decision making are usually limited to observations of decision outcomes. In the present study, we made use of the fact that oculomotor and sensory selection are closely linked to track oculomotor decision making before oculomotor responses are made. We asked participants to make a saccadic eye movement to one of two memorized target locations and observed that visual sensitivity increased at both the chosen and the nonchosen saccade target locations, with a clear bias toward the chosen target. The time course of changes in visual sensitivity was related to saccadic latency, with the competition between the chosen and nonchosen targets resolved faster before short-latency saccades. On error trials, we observed an increased competition between the chosen and nonchosen targets. Moreover, oculomotor selection and visual sensitivity were influenced by top-down and bottom-up factors as well as by selection history and predicted the direction of saccades. Our findings demonstrate that saccade decisions have direct visual consequences and show that decision making can be traced in the human oculomotor system well before choices are made. Our results also indicate a strong association between decision making, saccade target selection, and visual sensitivity. NEW & NOTEWORTHY We show that saccadic decisions can be tracked by measuring spatial attention. Spatial attention is allocated in parallel to the two competing saccade targets, and the time course of spatial attention differs for fast-slow and for correct-erroneous decisions. Saccade decisions take the form of a competition between potential saccade goals, which is associated with spatial attention allocation to those locations. Copyright © 2017 the American Physiological Society.

Effect of ethanol on the visual-evoked potential in rat: dynamics of ON and OFF responses.

PubMed

Dulinskas, Redas; Buisas, Rokas; Vengeliene, Valentina; Ruksenas, Osvaldas

2017-01-01

The effect of acute ethanol administration on the flash visual-evoked potential (VEP) was investigated in numerous studies. However, it is still unclear which brain structures are responsible for the differences observed in stimulus onset (ON) and offset (OFF) responses and how these responses are modulated by ethanol. The aim of our study was to investigate the pattern of ON and OFF responses in the visual system, measured as amplitude and latency of each VEP component following acute administration of ethanol. VEPs were recorded at the onset and offset of a 500 ms visual stimulus in anesthetized male Wistar rats. The effect of alcohol on VEP latency and amplitude was measured for one hour after injection of 2 g/kg ethanol dose. Three VEP components - N63, P89 and N143 - were analyzed. Our results showed that, except for component N143, ethanol increased the latency of both ON and OFF responses in a similar manner. The latency of N143 during OFF response was not affected by ethanol but its amplitude was reduced. Our study demonstrated that the activation of the visual system during the ON response to a 500 ms visual stimulus is qualitatively different from that during the OFF response. Ethanol interfered with processing of the stimulus duration at the level of the visual cortex and reduced the activation of cortical regions.

Risk assessment in man and mouse.

PubMed

Balci, Fuat; Freestone, David; Gallistel, Charles R

2009-02-17

Human and mouse subjects tried to anticipate at which of 2 locations a reward would appear. On a randomly scheduled fraction of the trials, it appeared with a short latency at one location; on the complementary fraction, it appeared after a longer latency at the other location. Subjects of both species accurately assessed the exogenous uncertainty (the probability of a short versus a long trial) and the endogenous uncertainty (from the scalar variability in their estimates of an elapsed duration) to compute the optimal target latency for a switch from the short- to the long-latency location. The optimal latency was arrived at so rapidly that there was no reliably discernible improvement over trials. Under these nonverbal conditions, humans and mice accurately assess risks and behave nearly optimally. That this capacity is well-developed in the mouse opens up the possibility of a genetic approach to the neurobiological mechanisms underlying risk assessment.

Risk assessment in man and mouse

PubMed Central

Balci, Fuat; Freestone, David; Gallistel, Charles R.

2009-01-01

Human and mouse subjects tried to anticipate at which of 2 locations a reward would appear. On a randomly scheduled fraction of the trials, it appeared with a short latency at one location; on the complementary fraction, it appeared after a longer latency at the other location. Subjects of both species accurately assessed the exogenous uncertainty (the probability of a short versus a long trial) and the endogenous uncertainty (from the scalar variability in their estimates of an elapsed duration) to compute the optimal target latency for a switch from the short- to the long-latency location. The optimal latency was arrived at so rapidly that there was no reliably discernible improvement over trials. Under these nonverbal conditions, humans and mice accurately assess risks and behave nearly optimally. That this capacity is well-developed in the mouse opens up the possibility of a genetic approach to the neurobiological mechanisms underlying risk assessment. PMID:19188592

Source analysis of short and long latency vestibular-evoked potentials (VsEPs) produced by left vs. right ear air-conducted 500 Hz tone pips.

PubMed

Todd, N P M; Paillard, A C; Kluk, K; Whittle, E; Colebatch, J G

2014-06-01

Todd et al. (2014) have recently demonstrated the presence of vestibular dependent changes both in the morphology and in the intensity dependence of auditory evoked potentials (AEPs) when passing through the vestibular threshold as determined by vestibular evoked myogenic potentials (VEMPs). In this paper we extend this work by comparing left vs. right ear stimulation and by conducting a source analysis of the resulting evoked potentials of short and long latency. Ten healthy, right-handed subjects were recruited and evoked potentials were recorded to both left- and right-ear sound stimulation, above and below vestibular threshold. Below VEMP threshold, typical AEPs were recorded, consisting of mid-latency (MLR) waves Na and Pa followed by long latency AEPs (LAEPs) N1 and P2. In the supra-threshold condition, the expected changes in morphology were observed, consisting of: (1) short-latency vestibular evoked potentials (VsEPs) which have no auditory correlate, i.e. the ocular VEMP (OVEMP) and inion response related potentials; (2) a later deflection, labelled N42/P52, followed by the LAEPs N1 and P2. Statistical analysis of the vestibular dependent responses indicated a contralateral effect for inion related short-latency responses and a left-ear/right-hemisphere advantage for the long-latency responses. Source analysis indicated that the short-latency effects may be mediated by a contralateral projection to left cerebellum, while the long-latency effects were mediated by a contralateral projection to right cingulate cortex. In addition we found evidence of a possible vestibular contribution to the auditory T-complex in radial temporal lobe sources. These last results raise the possibility that acoustic activation of the otolith organs could potentially contribute to auditory processing. Copyright © 2014 The Authors. Published by Elsevier B.V. All rights reserved.

Synaptic activation of putative sensory neurons by hexamethonium-sensitive nerve pathways in mouse colon.

PubMed

Hibberd, Timothy J; Travis, Lee; Wiklendt, Lukasz; Costa, Marcello; Brookes, Simon J H; Hu, Hongzhen; Keating, Damien J; Spencer, Nick J

2018-01-01

The gastrointestinal tract contains its own independent population of sensory neurons within the gut wall. These sensory neurons have been referred to as intrinsic primary afferent neurons (IPANs) and can be identified by immunoreactivity to calcitonin gene-related peptide (CGRP) in mice. A common feature of IPANs is a paucity of fast synaptic inputs observed during sharp microelectrode recordings. Whether this is observed using different recording techniques is of particular interest for understanding the physiology of these neurons and neural circuit modeling. Here, we imaged spontaneous and evoked activation of myenteric neurons in isolated whole preparations of mouse colon and correlated recordings with CGRP and nitric oxide synthase (NOS) immunoreactivity, post hoc. Calcium indicator fluo 4 was used for this purpose. Calcium responses were recorded in nerve cell bodies located 5-10 mm oral to transmural electrical nerve stimuli. A total of 618 recorded neurons were classified for CGRP or NOS immunoreactivity. Aboral electrical stimulation evoked short-latency calcium transients in the majority of myenteric neurons, including ~90% of CGRP-immunoreactive Dogiel type II neurons. Activation of Dogiel type II neurons had a time course consistent with fast synaptic transmission and was always abolished by hexamethonium (300 μM) and by low-calcium Krebs solution. The nicotinic receptor agonist 1,1-dimethyl-4-phenylpiperazinium iodide (during synaptic blockade) directly activated Dogiel type II neurons. The present study suggests that murine colonic Dogiel type II neurons receive prominent fast excitatory synaptic inputs from hexamethonium-sensitive neural pathways. NEW & NOTEWORTHY Myenteric neurons in isolated mouse colon were recorded using calcium imaging and then neurochemically defined. Short-latency calcium transients were detected in >90% of calcitonin gene-related peptide-immunoreactive neurons to electrical stimulation of hexamethonium-sensitive pathways. Putative sensory Dogiel type II calcitonin gene-related peptide-immunoreactive myenteric neurons may receive widespread fast synaptic inputs in mouse colon.

Online control of reaching and pointing to visual, auditory, and multimodal targets: Effects of target modality and method of determining correction latency.

PubMed

Holmes, Nicholas P; Dakwar, Azar R

2015-12-01

Movements aimed towards objects occasionally have to be adjusted when the object moves. These online adjustments can be very rapid, occurring in as little as 100ms. More is known about the latency and neural basis of online control of movements to visual than to auditory target objects. We examined the latency of online corrections in reaching-to-point movements to visual and auditory targets that could change side and/or modality at movement onset. Visual or auditory targets were presented on the left or right sides, and participants were instructed to reach and point to them as quickly and as accurately as possible. On half of the trials, the targets changed side at movement onset, and participants had to correct their movements to point to the new target location as quickly as possible. Given different published approaches to measuring the latency for initiating movement corrections, we examined several different methods systematically. What we describe here as the optimal methods involved fitting a straight-line model to the velocity of the correction movement, rather than using a statistical criterion to determine correction onset. In the multimodal experiment, these model-fitting methods produced significantly lower latencies for correcting movements away from the auditory targets than away from the visual targets. Our results confirm that rapid online correction is possible for auditory targets, but further work is required to determine whether the underlying control system for reaching and pointing movements is the same for auditory and visual targets. Copyright © 2015 Elsevier Ltd. All rights reserved.

Early and late beta-band power reflect audiovisual perception in the McGurk illusion

PubMed Central

Senkowski, Daniel; Keil, Julian

2015-01-01

The McGurk illusion is a prominent example of audiovisual speech perception and the influence that visual stimuli can have on auditory perception. In this illusion, a visual speech stimulus influences the perception of an incongruent auditory stimulus, resulting in a fused novel percept. In this high-density electroencephalography (EEG) study, we were interested in the neural signatures of the subjective percept of the McGurk illusion as a phenomenon of speech-specific multisensory integration. Therefore, we examined the role of cortical oscillations and event-related responses in the perception of congruent and incongruent audiovisual speech. We compared the cortical activity elicited by objectively congruent syllables with incongruent audiovisual stimuli. Importantly, the latter elicited a subjectively congruent percept: the McGurk illusion. We found that early event-related responses (N1) to audiovisual stimuli were reduced during the perception of the McGurk illusion compared with congruent stimuli. Most interestingly, our study showed a stronger poststimulus suppression of beta-band power (13–30 Hz) at short (0–500 ms) and long (500–800 ms) latencies during the perception of the McGurk illusion compared with congruent stimuli. Our study demonstrates that auditory perception is influenced by visual context and that the subsequent formation of a McGurk illusion requires stronger audiovisual integration even at early processing stages. Our results provide evidence that beta-band suppression at early stages reflects stronger stimulus processing in the McGurk illusion. Moreover, stronger late beta-band suppression in McGurk illusion indicates the resolution of incongruent physical audiovisual input and the formation of a coherent, illusory multisensory percept. PMID:25568160

Early and late beta-band power reflect audiovisual perception in the McGurk illusion.

PubMed

Roa Romero, Yadira; Senkowski, Daniel; Keil, Julian

2015-04-01

The McGurk illusion is a prominent example of audiovisual speech perception and the influence that visual stimuli can have on auditory perception. In this illusion, a visual speech stimulus influences the perception of an incongruent auditory stimulus, resulting in a fused novel percept. In this high-density electroencephalography (EEG) study, we were interested in the neural signatures of the subjective percept of the McGurk illusion as a phenomenon of speech-specific multisensory integration. Therefore, we examined the role of cortical oscillations and event-related responses in the perception of congruent and incongruent audiovisual speech. We compared the cortical activity elicited by objectively congruent syllables with incongruent audiovisual stimuli. Importantly, the latter elicited a subjectively congruent percept: the McGurk illusion. We found that early event-related responses (N1) to audiovisual stimuli were reduced during the perception of the McGurk illusion compared with congruent stimuli. Most interestingly, our study showed a stronger poststimulus suppression of beta-band power (13-30 Hz) at short (0-500 ms) and long (500-800 ms) latencies during the perception of the McGurk illusion compared with congruent stimuli. Our study demonstrates that auditory perception is influenced by visual context and that the subsequent formation of a McGurk illusion requires stronger audiovisual integration even at early processing stages. Our results provide evidence that beta-band suppression at early stages reflects stronger stimulus processing in the McGurk illusion. Moreover, stronger late beta-band suppression in McGurk illusion indicates the resolution of incongruent physical audiovisual input and the formation of a coherent, illusory multisensory percept. Copyright © 2015 the American Physiological Society.

Empirical mode decomposition processing to improve multifocal-visual-evoked-potential signal analysis in multiple sclerosis

PubMed Central

2018-01-01

Objective To study the performance of multifocal-visual-evoked-potential (mfVEP) signals filtered using empirical mode decomposition (EMD) in discriminating, based on amplitude, between control and multiple sclerosis (MS) patient groups, and to reduce variability in interocular latency in control subjects. Methods MfVEP signals were obtained from controls, clinically definitive MS and MS-risk progression patients (radiologically isolated syndrome (RIS) and clinically isolated syndrome (CIS)). The conventional method of processing mfVEPs consists of using a 1–35 Hz bandpass frequency filter (XDFT). The EMD algorithm was used to decompose the XDFT signals into several intrinsic mode functions (IMFs). This signal processing was assessed by computing the amplitudes and latencies of the XDFT and IMF signals (XEMD). The amplitudes from the full visual field and from ring 5 (9.8–15° eccentricity) were studied. The discrimination index was calculated between controls and patients. Interocular latency values were computed from the XDFT and XEMD signals in a control database to study variability. Results Using the amplitude of the mfVEP signals filtered with EMD (XEMD) obtains higher discrimination index values than the conventional method when control, MS-risk progression (RIS and CIS) and MS subjects are studied. The lowest variability in interocular latency computations from the control patient database was obtained by comparing the XEMD signals with the XDFT signals. Even better results (amplitude discrimination and latency variability) were obtained in ring 5 (9.8–15° eccentricity of the visual field). Conclusions Filtering mfVEP signals using the EMD algorithm will result in better identification of subjects at risk of developing MS and better accuracy in latency studies. This could be applied to assess visual cortex activity in MS diagnosis and evolution studies. PMID:29677200

Transcutaneous Electrical Nerve Stimulation Effects on Neglect: A Visual-Evoked Potential Study

PubMed Central

Pitzalis, Sabrina; Spinelli, Donatella; Vallar, Giuseppe; Di Russo, Francesco

2013-01-01

We studied the effects of transcutaneous electrical nerve stimulation (TENS) in six right-brain-damaged patients with left unilateral spatial neglect (USN), using both standard clinical tests (reading, line, and letter cancelation, and line bisection), and electrophysiological measures (steady-state visual-evoked potentials, SSVEP). TENS was applied on left neck muscles for 15′, and measures were recorded before, immediately after, and 60′ after stimulation. Behavioral results showed that the stimulation temporarily improved the deficit in all patients. In cancelation tasks, omissions and performance asymmetries between the two hand-sides were reduced, as well as the rightward deviation in line bisection. Before TENS, SSVEP average latency to stimuli displayed in the left visual half-field [LVF (160 ms)] was remarkably longer than to stimuli shown in the right visual half-field [RVF (120 ms)]. Immediately after TENS, latency to LVF stimuli was 130 ms; 1 h after stimulation the effect of TENS faded, with latency returning to baseline. TENS similarly affected also the latency SSVEP of 12 healthy participants, and their line bisection performance, with effects smaller in size. The present study, first, replicates evidence concerning the positive behavioral effects of TENS on the manifestations of left USN in right-brain-damaged patients; second, it shows putatively related electrophysiological effects on the SSVEP latency. These behavioral and novel electrophysiological results are discussed in terms of specific directional effects of left somatosensory stimulation on egocentric coordinates, which in USN patients are displaced toward the side of the cerebral lesion. Showing that visual-evoked potentials latency is modulated by proprioceptive stimulation, we provide electrophysiological evidence to the effect that TENS may improve some manifestations of USN, with implications for its rehabilitation. PMID:23966919

[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.

Latency in Visionic Systems: Test Methods and Requirements

NASA Technical Reports Server (NTRS)

Bailey, Randall E.; Arthur, J. J., III; Williams, Steven P.; Kramer, Lynda J.

2005-01-01

A visionics device creates a pictorial representation of the external scene for the pilot. The ultimate objective of these systems may be to electronically generate a form of Visual Meteorological Conditions (VMC) to eliminate weather or time-of-day as an operational constraint and provide enhancement over actual visual conditions where eye-limiting resolution may be a limiting factor. Empirical evidence has shown that the total system delays or latencies including the imaging sensors and display systems, can critically degrade their utility, usability, and acceptability. Definitions and measurement techniques are offered herein as common test and evaluation methods for latency testing in visionics device applications. Based upon available data, very different latency requirements are indicated based upon the piloting task, the role in which the visionics device is used in this task, and the characteristics of the visionics cockpit display device including its resolution, field-of-regard, and field-of-view. The least stringent latency requirements will involve Head-Up Display (HUD) applications, where the visionics imagery provides situational information as a supplement to symbology guidance and command information. Conversely, the visionics system latency requirement for a large field-of-view Head-Worn Display application, providing a Virtual-VMC capability from which the pilot will derive visual guidance, will be the most stringent, having a value as low as 20 msec.

Effects of ischaemia upon reflex electromyographic responses evoked by stretch and vibration in human wrist flexor muscles.

PubMed Central

Cody, F W; Goodwin, C N; Richardson, H C

1987-01-01

1. The reflex electromyographic responses evoked in a wrist flexor muscle, flexor carpi radialis (f.c.r.), by forcible extension of the wrist ('stretch') and by vibration of the flexor tendon have been studied in normal subjects. Reflexes were elicited during the maintenance of a low level of voluntary flexor contraction (5% maximum). Stretch regularly produced a relatively prolonged (ca. 100 ms duration) increase in e.m.g. activity which was usually divisible into short-latency (ca. 25 ms, M1) and long-latency (ca. 50 ms, M2) peaks. Vibration produced a single, phasic peak, at short latency, with no sign of an accompanying long-latency wave comparable to the M2 stretch response. 2. Ischaemia was induced by inflation of a blood-pressure cuff around the upper arm and its effects upon the reflex patterns were studied. During ischaemia M1 stretch responses showed a more rapid and pronounced decline than did M2 responses and were abolished before voluntary power was appreciably affected. Vibration-evoked short-latency peaks changed in an essentially parallel manner to M1 stretch reflexes. During recovery from ischaemia M2 reflexes were restored before short-latency responses. 3. The patterns of reflex reductions in e.m.g. upon withdrawal of stimulation were also studied. Such troughs in activity, under non-ischaemic conditions, regularly commenced at short latency and were of relatively small amplitude. The records of several of the subjects, and particularly ones obtained during ischaemia, suggested that release of stretch (with concomitant stretch of antagonists) could elicit an additive, long-latency decline in e.m.g. The existence of any such separate, delayed component was never observed upon termination of vibration. 4. Measurements of changes in the latencies and durations of reflex components, accompanying the progression of ischaemia, indicated that depression of early reflex activity resulted in part from increases in the latencies of these initial peaks but predominantly reflected simultaneous and separate reductions in their amplitudes. 5. The generation of short-latency reflexes by stretch and vibration, both of which stimuli powerfully excite muscle spindle primary endings, and the marked susceptibility of these responses to ischaemia supports their being mediated by group Ia afferents. The contrasting behaviour of M2 stretch responses, both regarding their absence with vibration and their resistance to ischaemia, suggests that they depend crucially upon a separate group of reflex afferents.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:3443959

Influence of rotating shift work on visual reaction time and visual evoked potential.

PubMed

R V, Hemamalini; N, Krishnamurthy; A, Saravanan

2014-10-01

The present day life style is changing the circadian rhythm of the body especially in rotating night shift workers. The impact of this prolongs their reaction time. Night shift also interferes with the circadian variation of pupil size which may affect the visual evoked potential. To compare the visual reaction time, visual evoked potential (VEP) in rotating night shift workers & day workers and also to correlate the changes in visual reaction time with visual evoked potential. Forty healthy male security guards & staff (25 - 35 y) who did rotating night shifts at least for six months & 40 d workers (25 - 35 y) who did not do night shift in last two years were involved in the study. Visual reaction time and the latency & amplitude of VEP were recorded. Kolmogorov- Smirnov test for normalcy showed the latencies & amplitude of VEP to be normally distributed. Student's unpaired t test showed significant difference (p<0.05) in the visual time and in the latencies of VEP between night shift & day workers. There was no significant difference in the amplitude of VEP. Night shift workers who are prone to circadian rhythm alteration will have prolonged visual reaction time & visual evoked potential abnormalities. Implementation of Bright Light Therapy would be beneficial to the night shift worker.

Whisker row deprivation affects the flow of sensory information through rat barrel cortex.

PubMed

Jacob, Vincent; Mitani, Akinori; Toyoizumi, Taro; Fox, Kevin

2017-01-01

Whisker trimming causes substantial reorganization of neuronal response properties in barrel cortex. However, little is known about experience-dependent rerouting of sensory processing following sensory deprivation. To address this, we performed in vivo intracellular recordings from layers 2/3 (L2/3), layer 4 (L4), layer 5 regular-spiking (L5RS), and L5 intrinsically bursting (L5IB) neurons and measured their multiwhisker receptive field at the level of spiking activity, membrane potential, and synaptic conductance before and after sensory deprivation. We used Chernoff information to quantify the "sensory information" contained in the firing patterns of cells in response to spared and deprived whisker stimulation. In the control condition, information for flanking-row and same-row whiskers decreased in the order L4, L2/3, L5IB, L5RS. However, after whisker-row deprivation, spared flanking-row whisker information was reordered to L4, L5RS, L5IB, L2/3. Sensory information from the trimmed whiskers was reduced and delayed in L2/3 and L5IB neurons, whereas sensory information from spared whiskers was increased and advanced in L4 and L5RS neurons. Sensory information from spared whiskers was increased in L5IB neurons without a latency change. L5RS cells exhibited the largest changes in sensory information content through an atypical plasticity combining a significant decrease in spontaneous activity and an increase in a short-latency excitatory conductance. Sensory cortical plasticity is usually quantified by changes in evoked firing rate. In this study we quantified plasticity by changes in sensory detection performance using Chernoff information and receiver operating characteristic analysis. We found that whisker deprivation causes a change in information flow within the cortical layers and that layer 5 regular-spiking cells, despite showing only a small potentiation of short-latency input, show the greatest increase in information content for the spared input partly by decreasing their spontaneous activity. Copyright © 2017 the American Physiological Society.

The search for instantaneous vection: An oscillating visual prime reduces vection onset latency.

PubMed

Palmisano, Stephen; Riecke, Bernhard E

2018-01-01

Typically it takes up to 10 seconds or more to induce a visual illusion of self-motion ("vection"). However, for this vection to be most useful in virtual reality and vehicle simulation, it needs to be induced quickly, if not immediately. This study examined whether vection onset latency could be reduced towards zero using visual display manipulations alone. In the main experiments, visual self-motion simulations were presented to observers via either a large external display or a head-mounted display (HMD). Priming observers with visually simulated viewpoint oscillation for just ten seconds before the main self-motion display was found to markedly reduce vection onset latencies (and also increase ratings of vection strength) in both experiments. As in earlier studies, incorporating this simulated viewpoint oscillation into the self-motion displays themselves was also found to improve vection. Average onset latencies were reduced from 8-9s in the no oscillating control condition to as little as 4.6 s (for external displays) or 1.7 s (for HMDs) in the combined oscillation condition (when both the visual prime and the main self-motion display were oscillating). As these display manipulations did not appear to increase the likelihood or severity of motion sickness in the current study, they could possibly be used to enhance computer generated simulation experiences and training in the future, at no additional cost.

The search for instantaneous vection: An oscillating visual prime reduces vection onset latency

PubMed Central

Riecke, Bernhard E.

2018-01-01

Typically it takes up to 10 seconds or more to induce a visual illusion of self-motion (“vection”). However, for this vection to be most useful in virtual reality and vehicle simulation, it needs to be induced quickly, if not immediately. This study examined whether vection onset latency could be reduced towards zero using visual display manipulations alone. In the main experiments, visual self-motion simulations were presented to observers via either a large external display or a head-mounted display (HMD). Priming observers with visually simulated viewpoint oscillation for just ten seconds before the main self-motion display was found to markedly reduce vection onset latencies (and also increase ratings of vection strength) in both experiments. As in earlier studies, incorporating this simulated viewpoint oscillation into the self-motion displays themselves was also found to improve vection. Average onset latencies were reduced from 8-9s in the no oscillating control condition to as little as 4.6 s (for external displays) or 1.7 s (for HMDs) in the combined oscillation condition (when both the visual prime and the main self-motion display were oscillating). As these display manipulations did not appear to increase the likelihood or severity of motion sickness in the current study, they could possibly be used to enhance computer generated simulation experiences and training in the future, at no additional cost. PMID:29791445

The influence of target angular velocity on visual latency difference determined using the rotating Pulfrich effect.

PubMed

Nickalls, R W

1996-09-01

Visual latency difference was determined directly in normal volunteers, using the rotating Pulfrich technique described by Nickalls [Vision Research, 26, 367-372 (1986)]. Subjects fixated a black vertical rod rotating clockwise on a horizontal turntable turning with constant angular velocity (16.6,33.3 or 44.7 revs/min) with a neutral density filter (OD 0.7 or 1.5) in front of the right eye. For all subjects the latency difference associated with the 1.5 OD filter was significantly greater (P < 0.001) with the rod rotating at 16.6 rev/min than at 33.3 revs/min. The existence of an inverse relationship between latency difference and angular velocity is hypothesized.

Mid-latency auditory evoked potential response revealed as an evidence of neural plasticity in blinnd individuals.

PubMed

Muthusamy, Anbarasi; Gajendran, Rajkumar; Rao B, Vishwanatha

2014-01-01

There is a general impression that visually blind individuals show an exceptionally better perception of other sensory modalities such as hearing, touch and smell sensations. In this study, we intended to compare the mid-latency auditory evoked potential response (MLAEP) or Middle latency Response (MLR) to get an idea of the activity pattern of auditory thalamus and cortex between 30 visually handicapped subjects and 30 normal sighted subjects. The results showed a decrease in many of the MLR wave latencies, but highly significant for the wave Pa (P value <0.002). This fact can be reflected as an evidence of existence of cross-modal neuroplasticity. We also inferred that there are significant gender differences with latencies shorter in males than females (P value <0.02) in the blind subjects group which could be attributed to their rehabilitation training.

Intracortical circuits amplify sound-evoked activity in primary auditory cortex following systemic injection of salicylate in the rat

PubMed Central

Chrostowski, Michael; Salvi, Richard J.; Allman, Brian L.

2012-01-01

A high dose of sodium salicylate temporarily induces tinnitus, mild hearing loss, and possibly hyperacusis in humans and other animals. Salicylate has well-established effects on cochlear function, primarily resulting in the moderate reduction of auditory input to the brain. Despite decreased peripheral sensitivity and output, salicylate induces a paradoxical enhancement of the sound-evoked field potential at the level of the primary auditory cortex (A1). Previous electrophysiologic studies have begun to characterize changes in thalamorecipient layers of A1; however, A1 is a complex neural circuit with recurrent intracortical connections. To describe the effects of acute systemic salicylate treatment on both thalamic and intracortical sound-driven activity across layers of A1, we applied current-source density (CSD) analysis to field potentials sampled across cortical layers in the anesthetized rat. CSD maps were normally characterized by a large, short-latency, monosynaptic, thalamically driven sink in granular layers followed by a lower amplitude, longer latency, polysynaptic, intracortically driven sink in supragranular layers. Following systemic administration of salicylate, there was a near doubling of both granular and supragranular sink amplitudes at higher sound levels. The supragranular sink amplitude input/output function changed from becoming asymptotic at approximately 50 dB to sharply nonasymptotic, often dominating the granular sink amplitude at higher sound levels. The supragranular sink also exhibited a significant decrease in peak latency, reflecting an acceleration of intracortical processing of the sound-evoked response. Additionally, multiunit (MU) activity was altered by salicylate; the normally onset/sustained MU response type was transformed into a primarily onset response type in granular and infragranular layers. The results from CSD analysis indicate that salicylate significantly enhances sound-driven response via intracortical circuits. PMID:22496535

A Dual-Route Perspective on Brain Activation in Response to Visual Words: Evidence for a Length by Lexicality Interaction in the Visual Word Form Area (VWFA)

PubMed Central

Schurz, Matthias; Sturm, Denise; Richlan, Fabio; Kronbichler, Martin; Ladurner, Gunther; Wimmer, Heinz

2010-01-01

Based on our previous work, we expected the Visual Word Form Area (VWFA) in the left ventral visual pathway to be engaged by both whole-word recognition and by serial sublexical coding of letter strings. To examine this double function, a phonological lexical decision task (i.e., “Does xxx sound like an existing word?”) presented short and long letter strings of words, pseudohomophones, and pseudowords (e.g., Taxi, Taksi and Tazi). Main findings were that the length effect for words was limited to occipital regions and absent in the VWFA. In contrast, a marked length effect for pseudowords was found throughout the ventral visual pathway including the VWFA, as well as in regions presumably engaged by visual attention and silent-articulatory processes. The length by lexicality interaction on brain activation corresponds to well-established behavioral findings of a length by lexicality interaction on naming latencies and speaks for the engagement of the VWFA by both lexical and sublexical processes. PMID:19896538

A dual-route perspective on brain activation in response to visual words: evidence for a length by lexicality interaction in the visual word form area (VWFA).

PubMed

Schurz, Matthias; Sturm, Denise; Richlan, Fabio; Kronbichler, Martin; Ladurner, Gunther; Wimmer, Heinz

2010-02-01

Based on our previous work, we expected the Visual Word Form Area (VWFA) in the left ventral visual pathway to be engaged by both whole-word recognition and by serial sublexical coding of letter strings. To examine this double function, a phonological lexical decision task (i.e., "Does xxx sound like an existing word?") presented short and long letter strings of words, pseudohomophones, and pseudowords (e.g., Taxi, Taksi and Tazi). Main findings were that the length effect for words was limited to occipital regions and absent in the VWFA. In contrast, a marked length effect for pseudowords was found throughout the ventral visual pathway including the VWFA, as well as in regions presumably engaged by visual attention and silent-articulatory processes. The length by lexicality interaction on brain activation corresponds to well-established behavioral findings of a length by lexicality interaction on naming latencies and speaks for the engagement of the VWFA by both lexical and sublexical processes. Copyright (c) 2009 Elsevier Inc. All rights reserved.

Aging effects on the Binaural Interaction Component of the Auditory Brainstem Response in the Mongolian Gerbil: Effects of Interaural Time and Level Differences

PubMed Central

Laumen, Geneviève; Tollin, Daniel J.; Beutelmann, Rainer; Klump, Georg M.

2016-01-01

The effect of interaural time difference (ITD) and interaural level difference (ILD) on wave 4 of the binaural and summed monaural auditory brainstem responses (ABRs) as well as on the DN1 component of the binaural interaction component (BIC) of the ABR in young and old Mongolian gerbils (Meriones unguiculatus) was investigated. Measurements were made at a fixed sound pressure level (SPL) and a fixed level above visually detected ABR threshold to compensate for individual hearing threshold differences. In both stimulation modes (fixed SPL and fixed level above visually detected ABR threshold) an effect of ITD on the latency and the amplitude of wave 4 as well as of the BIC was observed. With increasing absolute ITD values BIC latencies were increased and amplitudes were decreased. ILD had a much smaller effect on these measures. Old animals showed a reduced amplitude of the DN1 component. This difference was due to a smaller wave 4 in the summed monaural ABRs of old animals compared to young animals whereas wave 4 in the binaural-evoked ABR showed no age-related difference. In old animals the small amplitude of the DN1 component was correlated with small binaural-evoked wave 1 and wave 3 amplitudes. This suggests that the reduced peripheral input affects central binaural processing which is reflected in the BIC. PMID:27173973

Delayed P100-Like Latencies in Multiple Sclerosis: A Preliminary Investigation Using Visual Evoked Spread Spectrum Analysis

PubMed Central

Kiiski, Hanni S. M.; Ní Riada, Sinéad; Lalor, Edmund C.; Gonçalves, Nuno R.; Nolan, Hugh; Whelan, Robert; Lonergan, Róisín; Kelly, Siobhán; O'Brien, Marie Claire; Kinsella, Katie; Bramham, Jessica; Burke, Teresa; Ó Donnchadha, Seán; Hutchinson, Michael; Tubridy, Niall; Reilly, Richard B.

2016-01-01

Conduction along the optic nerve is often slowed in multiple sclerosis (MS). This is typically assessed by measuring the latency of the P100 component of the Visual Evoked Potential (VEP) using electroencephalography. The Visual Evoked Spread Spectrum Analysis (VESPA) method, which involves modulating the contrast of a continuous visual stimulus over time, can produce a visually evoked response analogous to the P100 but with a higher signal-to-noise ratio and potentially higher sensitivity to individual differences in comparison to the VEP. The main objective of the study was to conduct a preliminary investigation into the utility of the VESPA method for probing and monitoring visual dysfunction in multiple sclerosis. The latencies and amplitudes of the P100-like VESPA component were compared between healthy controls and multiple sclerosis patients, and multiple sclerosis subgroups. The P100-like VESPA component activations were examined at baseline and over a 3-year period. The study included 43 multiple sclerosis patients (23 relapsing-remitting MS, 20 secondary-progressive MS) and 42 healthy controls who completed the VESPA at baseline. The follow-up sessions were conducted 12 months after baseline with 24 MS patients (15 relapsing-remitting MS, 9 secondary-progressive MS) and 23 controls, and again at 24 months post-baseline with 19 MS patients (13 relapsing-remitting MS, 6 secondary-progressive MS) and 14 controls. The results showed P100-like VESPA latencies to be delayed in multiple sclerosis compared to healthy controls over the 24-month period. Secondary-progressive MS patients had most pronounced delay in P100-like VESPA latency relative to relapsing-remitting MS and controls. There were no longitudinal P100-like VESPA response differences. These findings suggest that the VESPA method is a reproducible electrophysiological method that may have potential utility in the assessment of visual dysfunction in multiple sclerosis. PMID:26726800

Visual event-related potential changes in two subtypes of multiple system atrophy, MSA-C and MSA-P.

PubMed

Kamitani, Toshiaki; Kuroiwa, Yoshiyuki; Wang, Lihong; Li, Mei; Suzuki, Yume; Takahashi, Tatsuya; Ikegami, Tadashi; Matsubara, Sho

2002-08-01

We investigated the visual event-related potentials (ERPs) in two subtypes of multisystem atrophy (MSA) in 15 MSA-C patients, 12 MSA-P patients, and 21 normal control (NC) subjects. We used a visual oddball task to elicit ERPs. No significant changes were seen in N1 or N2 latency, in either MSA-C or MSA-P, compared with the NC group. An early stage of visual information process related to N1 and a visual discrimination process related to N2 might be preserved in both MSA-C and MSA-P. The P3a peak was more frequently undetectable in MSA than in the NC group. Significant P3a amplitude reduction in both MSA-C and MSA-P suggests impairment of the automatic cognitive processing in both MSA-C and MSA-P. Significant difference was found in P3b latency and P3b amplitude only in MSA-C, compared with the NC group. The result suggests the impairment of the controlled cognitive processing after the visual discrimination process in the MSA-C group. We further investigated the correlation between visual ERP changes and magnetic resonance imaging (MRI) data. Quantitative MRI measurements showed reduced size of the pons, cerebellum, perisylvian cerebral area, and deep cerebral gray matter in both MSA-C and MSA-P, and of the corpus callosum only in MSA-P, as compared to NC group. In both MSA-C and MSA-P, P3b latency was significantly correlated with the size on MRI of the pons and the cerebellum. P3b latency in the whole MSA group was also significantly correlated with the size of the pons and the cerebellum. These results indicate that P3b latency changes in parallel with the volume of the pons and the cerebellum in both MSA-C and MSA-P.

Individual and Developmental Differences in Disengagement of Fixation in Early Infancy.

ERIC Educational Resources Information Center

Frick, Janet E.; Colombo, John; Saxon, Terrill F.

1999-01-01

Investigated whether individual and developmental differences in look duration were correlated with latency to disengage fixation from a visual stimulus for 3- and 4-month olds. Found that look duration was correlated with disengagement latency. Three-month olds showed slower latencies than 4-month olds. Long-looking infants showed greater…

Event-driven visual attention for the humanoid robot iCub

PubMed Central

Rea, Francesco; Metta, Giorgio; Bartolozzi, Chiara

2013-01-01

Fast reaction to sudden and potentially interesting stimuli is a crucial feature for safe and reliable interaction with the environment. Here we present a biologically inspired attention system developed for the humanoid robot iCub. It is based on input from unconventional event-driven vision sensors and an efficient computational method. The resulting system shows low-latency and fast determination of the location of the focus of attention. The performance is benchmarked against an instance of the state of the art in robotics artificial attention system used in robotics. Results show that the proposed system is two orders of magnitude faster that the benchmark in selecting a new stimulus to attend. PMID:24379753

Effects of strabismic amblyopia and strabismus without amblyopia on visuomotor behavior, I: saccadic eye movements.

PubMed

Niechwiej-Szwedo, Ewa; Chandrakumar, Manokaraananthan; Goltz, Herbert C; Wong, Agnes M F

2012-11-01

It has previously been shown that anisometropic amblyopia affects the programming and execution of saccades. The aim of the current study was to investigate the impact of strabismic amblyopia on saccade performance. Fourteen adults with strabismic amblyopia, 13 adults with strabismus without amblyopia, and 14 visually normal adults performed saccades and reach-to-touch movements to targets presented at ± 5° and ± 10° eccentricity during binocular and monocular viewing. Latency, amplitude, and peak velocity of primary and secondary saccades were measured. In contrast to visually normal participants who had shorter primary saccade latency during binocular viewing, no binocular advantage was found in patients with strabismus with or without amblyopia. Patients with amblyopia had longer saccade latency during amblyopic eye viewing (P < 0.0001); however, there were no significant differences in saccade amplitude precision among the three groups across viewing conditions. Further analysis showed that only patients with severe amblyopia and no stereopsis (n = 4) exhibited longer latency (which was more pronounced for more central targets; P < 0.0001), and they also had reduced amplitude precision during amblyopic eye viewing. In contrast, patients with mild amblyopia (n = 5) and no stereopsis had normal latency and reduced precision during amblyopic eye viewing (P < 0.001), whereas those with gross stereopsis (n = 5) had normal latency and precision. There were no differences in peak velocity among the groups. Distinct patterns of saccade performance according to different levels of visual acuity and stereoscopic losses in strabismic amblyopia were found. These findings were in contrast to those in anisometropic amblyopia in which the altered saccade performance was independent of the extent of visual acuity or stereoscopic deficits. These results were most likely due to different long-term sensory suppression mechanisms in strabismic versus anisometropic amblyopia.

The effect of monitor raster latency on VEPs, ERPs and Brain-Computer Interface performance.

PubMed

Nagel, Sebastian; Dreher, Werner; Rosenstiel, Wolfgang; Spüler, Martin

2018-02-01

Visual neuroscience experiments and Brain-Computer Interface (BCI) control often require strict timings in a millisecond scale. As most experiments are performed using a personal computer (PC), the latencies that are introduced by the setup should be taken into account and be corrected. As a standard computer monitor uses a rastering to update each line of the image sequentially, this causes a monitor raster latency which depends on the position, on the monitor and the refresh rate. We technically measured the raster latencies of different monitors and present the effects on visual evoked potentials (VEPs) and event-related potentials (ERPs). Additionally we present a method for correcting the monitor raster latency and analyzed the performance difference of a code-modulated VEP BCI speller by correcting the latency. There are currently no other methods validating the effects of monitor raster latency on VEPs and ERPs. The timings of VEPs and ERPs are directly affected by the raster latency. Furthermore, correcting the raster latency resulted in a significant reduction of the target prediction error from 7.98% to 4.61% and also in a more reliable classification of targets by significantly increasing the distance between the most probable and the second most probable target by 18.23%. The monitor raster latency affects the timings of VEPs and ERPs, and correcting resulted in a significant error reduction of 42.23%. It is recommend to correct the raster latency for an increased BCI performance and methodical correctness. Copyright © 2017 Elsevier B.V. All rights reserved.

Experiments in sensing transient rotational acceleration cues on a flight simulator

NASA Technical Reports Server (NTRS)

Parrish, R. V.

1979-01-01

Results are presented for two transient motion sensing experiments which were motivated by the identification of an anomalous roll cue (a 'jerk' attributed to an acceleration spike) in a prior investigation of realistic fighter motion simulation. The experimental results suggest the consideration of several issues for motion washout and challenge current sensory system modeling efforts. Although no sensory modeling effort is made it is argued that such models must incorporate the ability to handle transient inputs of short duration (some of which are less than the accepted latency times for sensing), and must represent separate channels for rotational acceleration and velocity sensing.

Effect of head circumference on parameters of pattern reversal visual evoked potential in healthy adults of central India.

PubMed

Kothari, R; Singh, R; Singh, S; Bokariya, P

2012-06-01

Visual evoked response testing has been one of the most exciting clinical tools to be developed from neurophysiologic research in recent years and has provided us with an objective method of identifying abnormalities of the afferent visual pathways. Investigation were carried out to see whether the head circumference influence the pattern reversal visual evoked potential (PRVEP) parameters. The study comprised of pattern reversal visual evoked potential (PRVEP) recordings in 400 eyes of 200 normal subjects. Two hundred fourty eight eyes were males and 152 eyes were from 76 female subjects recruited from the Central Indian population in the age range of 40-79 years. Visual evoked potential (VEP) recordings were performed in accordance to the standardized methodology of International Federation of Clinical Neurophysiology (IFCN) Committee Recommendations and International Society for Clinical Electrophysiology of Vision (ISCEV) Guidelines and montages were kept as per 10-20 International System of EEG Electrode placements. The stimulus configuration in this study consisted of the transient pattern reversal method in which a black and white checker board was generated (full field) and displayed on a VEP Monitor by an electronic pattern regenerator inbuilt in an Evoked Potential Recorder (RMS EMG EP MARK II). VEP latencies, duration and amplitude were measured in all subjects and the data were analyzed. The correlation of all the electrophysiological parameters with head circumference was evaluated by Pearson's correlation co-efficient (r) and its statistical significance was evaluated. The prediction equations for all the VEP parameters with respect to head circumference were derived. We found a positive correlation of P 100 latency and N 155 latency with mean head circumference, while a highly significant negative correlation were noted of P 100 amplitude with head circumference. N 70 latency was significantly correlated with head circumference. P 100 duration showed in negative correlation with head circumference. These findings suggest that VEP latencies, duration and amplitude are influenced by the head circumference of the individual in a sample of healthy subjects and head circumference can be a useful predictor of VEP peak latencies, amplitude and duration.

Earlier Visual N1 Latencies in Expert Video-Game Players: A Temporal Basis of Enhanced Visuospatial Performance?

PubMed Central

Latham, Andrew J.; Patston, Lucy L. M.; Westermann, Christine; Kirk, Ian J.; Tippett, Lynette J.

2013-01-01

Increasing behavioural evidence suggests that expert video game players (VGPs) show enhanced visual attention and visuospatial abilities, but what underlies these enhancements remains unclear. We administered the Poffenberger paradigm with concurrent electroencephalogram (EEG) recording to assess occipital N1 latencies and interhemispheric transfer time (IHTT) in expert VGPs. Participants comprised 15 right-handed male expert VGPs and 16 non-VGP controls matched for age, handedness, IQ and years of education. Expert VGPs began playing before age 10, had a minimum 8 years experience, and maintained playtime of at least 20 hours per week over the last 6 months. Non-VGPs had little-to-no game play experience (maximum 1.5 years). Participants responded to checkerboard stimuli presented to the left and right visual fields while 128-channel EEG was recorded. Expert VGPs responded significantly more quickly than non-VGPs. Expert VGPs also had significantly earlier occipital N1s in direct visual pathways (the hemisphere contralateral to the visual field in which the stimulus was presented). IHTT was calculated by comparing the latencies of occipital N1 components between hemispheres. No significant between-group differences in electrophysiological estimates of IHTT were found. Shorter N1 latencies may enable expert VGPs to discriminate attended visual stimuli significantly earlier than non-VGPs and contribute to faster responding in visual tasks. As successful video-game play requires precise, time pressured, bimanual motor movements in response to complex visual stimuli, which in this sample began during early childhood, these differences may reflect the experience and training involved during the development of video-game expertise, but training studies are needed to test this prediction. PMID:24058667

Earlier visual N1 latencies in expert video-game players: a temporal basis of enhanced visuospatial performance?

PubMed

Latham, Andrew J; Patston, Lucy L M; Westermann, Christine; Kirk, Ian J; Tippett, Lynette J

2013-01-01

Increasing behavioural evidence suggests that expert video game players (VGPs) show enhanced visual attention and visuospatial abilities, but what underlies these enhancements remains unclear. We administered the Poffenberger paradigm with concurrent electroencephalogram (EEG) recording to assess occipital N1 latencies and interhemispheric transfer time (IHTT) in expert VGPs. Participants comprised 15 right-handed male expert VGPs and 16 non-VGP controls matched for age, handedness, IQ and years of education. Expert VGPs began playing before age 10, had a minimum 8 years experience, and maintained playtime of at least 20 hours per week over the last 6 months. Non-VGPs had little-to-no game play experience (maximum 1.5 years). Participants responded to checkerboard stimuli presented to the left and right visual fields while 128-channel EEG was recorded. Expert VGPs responded significantly more quickly than non-VGPs. Expert VGPs also had significantly earlier occipital N1s in direct visual pathways (the hemisphere contralateral to the visual field in which the stimulus was presented). IHTT was calculated by comparing the latencies of occipital N1 components between hemispheres. No significant between-group differences in electrophysiological estimates of IHTT were found. Shorter N1 latencies may enable expert VGPs to discriminate attended visual stimuli significantly earlier than non-VGPs and contribute to faster responding in visual tasks. As successful video-game play requires precise, time pressured, bimanual motor movements in response to complex visual stimuli, which in this sample began during early childhood, these differences may reflect the experience and training involved during the development of video-game expertise, but training studies are needed to test this prediction.

Simultaneous selection by object-based attention in visual and frontal cortex

PubMed Central

Pooresmaeili, Arezoo; Poort, Jasper; Roelfsema, Pieter R.

2014-01-01

Models of visual attention hold that top-down signals from frontal cortex influence information processing in visual cortex. It is unknown whether situations exist in which visual cortex actively participates in attentional selection. To investigate this question, we simultaneously recorded neuronal activity in the frontal eye fields (FEF) and primary visual cortex (V1) during a curve-tracing task in which attention shifts are object-based. We found that accurate performance was associated with similar latencies of attentional selection in both areas and that the latency in both areas increased if the task was made more difficult. The amplitude of the attentional signals in V1 saturated early during a trial, whereas these selection signals kept increasing for a longer time in FEF, until the moment of an eye movement, as if FEF integrated attentional signals present in early visual cortex. In erroneous trials, we observed an interareal latency difference because FEF selected the wrong curve before V1 and imposed its erroneous decision onto visual cortex. The neuronal activity in visual and frontal cortices was correlated across trials, and this trial-to-trial coupling was strongest for the attended curve. These results imply that selective attention relies on reciprocal interactions within a large network of areas that includes V1 and FEF. PMID:24711379

Sex hormonal modulation of interhemispheric transfer time.

PubMed

Hausmann, M; Hamm, J P; Waldie, K E; Kirk, I J

2013-08-01

It is still a matter of debate whether functional cerebral asymmetries (FCA) of many cognitive processes are more pronounced in men than in women. Some evidence suggests that the apparent reduction in women's FCA is a result of the fluctuating levels of gonadal steroid hormones over the course of the menstrual cycle, making their FCA less static than for men. The degree of lateralization has been suggested to depend on interhemispheric communication that may be modulated by gonadal steroid hormones. Here, we employed visual-evoked EEG potentials to obtain a direct measure of interhemispheric communication during different phases of the menstrual cycle. The interhemispheric transfer time (IHTT) was estimated from the interhemispheric latency difference of the N170 component of the visual-evoked potential from either left or right visual field presentation. Nineteen right-handed women with regular menstrual cycles were tested twice, once during the menstrual phase, when progesterone and estradiol levels are low, and once during the luteal phase when progesterone and estradiol levels are high. Plasma steroid levels were determined by blood-based immunoassay at each session. It was found that IHTT, in particular from right-to-left, was generally longer during the luteal phase relative to the menstrual phase. This effect occurred as a consequence of a slowed absolute N170 latency of the indirect pathway (i.e. left hemispheric response after LVF stimulation) and, in particular, a shortened latency of the direct pathway (i.e. right hemispheric response after LVF stimulation) during the luteal phase. These results show that cycle-related effects are not restricted to modulation of processes between hemispheres but also apply to cortical interactions, especially within the right hemisphere. The findings support the view that plastic changes in the female brain occur during relatively short-term periods across the menstrual cycle. Copyright © 2013 Elsevier Ltd. All rights reserved.

Response sensitivity of barrel neuron subpopulations to simulated thalamic input.

PubMed

Pesavento, Michael J; Rittenhouse, Cynthia D; Pinto, David J

2010-06-01

Our goal is to examine the relationship between neuron- and network-level processing in the context of a well-studied cortical function, the processing of thalamic input by whisker-barrel circuits in rodent neocortex. Here we focus on neuron-level processing and investigate the responses of excitatory and inhibitory barrel neurons to simulated thalamic inputs applied using the dynamic clamp method in brain slices. Simulated inputs are modeled after real thalamic inputs recorded in vivo in response to brief whisker deflections. Our results suggest that inhibitory neurons require more input to reach firing threshold, but then fire earlier, with less variability, and respond to a broader range of inputs than do excitatory neurons. Differences in the responses of barrel neuron subtypes depend on their intrinsic membrane properties. Neurons with a low input resistance require more input to reach threshold but then fire earlier than neurons with a higher input resistance, regardless of the neuron's classification. Our results also suggest that the response properties of excitatory versus inhibitory barrel neurons are consistent with the response sensitivities of the ensemble barrel network. The short response latency of inhibitory neurons may serve to suppress ensemble barrel responses to asynchronous thalamic input. Correspondingly, whereas neurons acting as part of the barrel circuit in vivo are highly selective for temporally correlated thalamic input, excitatory barrel neurons acting alone in vitro are less so. These data suggest that network-level processing of thalamic input in barrel cortex depends on neuron-level processing of the same input by excitatory and inhibitory barrel neurons.

Abnormal functional connectivity density in children with anisometropic amblyopia at resting-state.

PubMed

Wang, Tianyue; Li, Qian; Guo, Mingxia; Peng, Yanmin; Li, Qingji; Qin, Wen; Yu, Chunshui

2014-05-14

Amblyopia is a developmental disorder resulting from anomalous binocular visual input in early life. Task-based neuroimaging studies have widely investigated cortical functional impairments in amblyopia, but changes in spontaneous neuronal functional activities in amblyopia remain largely unknown. In the present study, functional connectivity density (FCD) mapping, an ultrafast data-driven method based on fMRI, was applied for the first time to investigate changes in cortical functional connectivities in amblyopia during the resting-state. We quantified and compared both short- and long-range FCD in both the brains of children with anisometropic amblyopia (AAC) and normal sighted children (NSC). In contrast to the NSC, the AAC showed significantly decreased short-range FCD in the inferior temporal/fusiform gyri, parieto-occipital and rostrolateral prefrontal cortices, as well as decreased long-range FCD in the premotor cortex, dorsal inferior parietal lobule, frontal-insular and dorsal prefrontal cortices. Furthermore, most regions with reduced long-range FCD in the AAC showed decreased functional connectivity with occipital and posterior parietal cortices in the AAC. The results suggest that chronically poor visual input in amblyopia not only impairs the brain's short-range functional connections in visual pathways and in the frontal cortex, which is important for cognitive control, but also affects long-range functional connections among the visual areas, posterior parietal and frontal cortices that subserve visuomotor and visual-guided actions, visuospatial attention modulation and the integration of salient information. This study provides evidence for abnormal spontaneous brain activities in amblyopia. Copyright © 2014 Elsevier B.V. All rights reserved.

Chirp-modulated visual evoked potential as a generalization of steady state visual evoked potential

NASA Astrophysics Data System (ADS)

Tu, Tao; Xin, Yi; Gao, Xiaorong; Gao, Shangkai

2012-02-01

Visual evoked potentials (VEPs) are of great concern in cognitive and clinical neuroscience as well as in the recent research field of brain-computer interfaces (BCIs). In this study, a chirp-modulated stimulation was employed to serve as a novel type of visual stimulus. Based on our empirical study, the chirp stimuli visual evoked potential (Chirp-VEP) preserved frequency features of the chirp stimulus analogous to the steady state evoked potential (SSVEP), and therefore it can be regarded as a generalization of SSVEP. Specifically, we first investigated the characteristics of the Chirp-VEP in the time-frequency domain and the fractional domain via fractional Fourier transform. We also proposed a group delay technique to derive the apparent latency from Chirp-VEP. Results on EEG data showed that our approach outperformed the traditional SSVEP-based method in efficiency and ease of apparent latency estimation. For the recruited six subjects, the average apparent latencies ranged from 100 to 130 ms. Finally, we implemented a BCI system with six targets to validate the feasibility of Chirp-VEP as a potential candidate in the field of BCIs.

Minamata disease (organic mercury poisoning): neuroradiologic and electrophysiologic studies.

PubMed

Tokuomi, H; Uchino, M; Imamura, S; Yamanaga, H; Nakanishi, R; Ideta, T

1982-12-01

We studied 10 patients with Minamata disease (organic mercury poisoning) who have been followed for over 20 years. CT revealed a bilateral, symmetric, low-density area in the visual cortex and diffuse atrophy of the cerebellar hemispheres and vermis, especially the inferior vermis. Computerized quantitative analysis of the tremor of these patients showed a peculiar frequency of 7.075 Hz on postural tremor and 7.501 Hz on action tremor. On studies of short-latency somatosensory evoked potential, all patients showed a lack of the N20 component, the potential of the somatic sensory area.

A computational feedforward model predicts categorization of masked emotional body language for longer, but not for shorter, latencies.

PubMed

Stienen, Bernard M C; Schindler, Konrad; de Gelder, Beatrice

2012-07-01

Given the presence of massive feedback loops in brain networks, it is difficult to disentangle the contribution of feedforward and feedback processing to the recognition of visual stimuli, in this case, of emotional body expressions. The aim of the work presented in this letter is to shed light on how well feedforward processing explains rapid categorization of this important class of stimuli. By means of parametric masking, it may be possible to control the contribution of feedback activity in human participants. A close comparison is presented between human recognition performance and the performance of a computational neural model that exclusively modeled feedforward processing and was engineered to fulfill the computational requirements of recognition. Results show that the longer the stimulus onset asynchrony (SOA), the closer the performance of the human participants was to the values predicted by the model, with an optimum at an SOA of 100 ms. At short SOA latencies, human performance deteriorated, but the categorization of the emotional expressions was still above baseline. The data suggest that, although theoretically, feedback arising from inferotemporal cortex is likely to be blocked when the SOA is 100 ms, human participants still seem to rely on more local visual feedback processing to equal the model's performance.

Body sway adaptation to addition but not withdrawal of stabilizing visual information is delayed by a concurrent cognitive task.

PubMed

Honeine, Jean-Louis; Crisafulli, Oscar; Schieppati, Marco

2017-02-01

The aim of this study was to test the effects of a concurrent cognitive task on the promptness of the sensorimotor integration and reweighting processes following addition and withdrawal of vision. Fourteen subjects stood in tandem while vision was passively added and removed. Subjects performed a cognitive task, consisting of counting backward in steps of three, or were "mentally idle." We estimated the time intervals following addition and withdrawal of vision at which body sway began to change. We also estimated the time constant of the exponential change in body oscillation until the new level of sway was reached, consistent with the current visual state. Under the mentally idle condition, mean latency was 0.67 and 0.46 s and the mean time constant was 1.27 and 0.59 s for vision addition and withdrawal, respectively. Following addition of vision, counting backward delayed the latency by about 300 ms, without affecting the time constant. Following withdrawal, counting backward had no significant effect on either latency or time constant. The extension by counting backward of the time interval to stabilization onset on addition of vision suggests a competition for allocation of cortical resources. Conversely, the absence of cognitive task effect on the rapid onset of destabilization on vision withdrawal, and on the relevant reweighting time course, advocates the intervention of a subcortical process. Diverting attention from a challenging standing task discloses a cortical supervision on the process of sensorimotor integration of new balance-stabilizing information. A subcortical process would instead organize the response to removal of the stabilizing sensory input. NEW & NOTEWORTHY This study is the first to test the effect of an arithmetic task on the time course of balance readjustment following visual withdrawal or addition. Performing such a cognitive task increases the time delay following addition of vision but has no effect on withdrawal dynamics. This suggests that sensorimotor integration following addition of a stabilizing signal is performed at a cortical level, whereas the response to its withdrawal is "automatic" and accomplished at a subcortical level. Copyright © 2017 the American Physiological Society.

Primary display latency criteria based on flying qualities and performance data

NASA Technical Reports Server (NTRS)

Funk, John D., Jr.; Beck, Corin P.; Johns, John B.

1993-01-01

With a pilots' increasing use of visual cue augmentation, much requiring extensive pre-processing, there is a need to establish criteria for new avionics/display design. The timeliness and synchronization of the augmented cues is vital to ensure the performance quality required for precision mission task elements (MTEs) where augmented cues are the primary source of information to the pilot. Processing delays incurred while transforming sensor-supplied flight information into visual cues are unavoidable. Relationships between maximum control system delays and associated flying qualities levels are documented in MIL-F-83300 and MIL-F-8785. While cues representing aircraft status may be just as vital to the pilot as prompt control response for operations in instrument meteorological conditions, presently, there are no specification requirements on avionics system latency. To produce data relating avionics system latency to degradations in flying qualities, the Navy conducted two simulation investigations. During the investigations, flying qualities and performance data were recorded as simulated avionics system latency was varied. Correlated results of the investigation indicates that there is a detrimental impact of latency on flying qualities. Analysis of these results and consideration of key factors influencing their application indicate that: (1) Task performance degrades and pilot workload increases as latency is increased. Inconsistency in task performance increases as latency increases. (2) Latency reduces the probability of achieving Level 1 handling qualities with avionics system latency as low as 70 ms. (3) The data suggest that the achievement of desired performance will be ensured only at display latency values below 120 ms. (4) These data also suggest that avoidance of inadequate performance will be ensured only at display latency values below 150 ms.

Competition between color and luminance for target selection in smooth pursuit and saccadic eye movements.

PubMed

Spering, Miriam; Montagnini, Anna; Gegenfurtner, Karl R

2008-11-24

Visual processing of color and luminance for smooth pursuit and saccadic eye movements was investigated using a target selection paradigm. In two experiments, stimuli were varied along the dimensions color and luminance, and selection of the more salient target was compared in pursuit and saccades. Initial pursuit was biased in the direction of the luminance component whereas saccades showed a relative preference for color. An early pursuit response toward luminance was often reversed to color by a later saccade. Observers' perceptual judgments of stimulus salience, obtained in two control experiments, were clearly biased toward luminance. This choice bias in perceptual data implies that the initial short-latency pursuit response agrees with perceptual judgments. In contrast, saccades, which have a longer latency than pursuit, do not seem to follow the perceptual judgment of salience but instead show a stronger relative preference for color. These substantial differences in target selection imply that target selection processes for pursuit and saccadic eye movements use distinctly different weights for color and luminance stimuli.

Transcranial magnetic stimulation over the cerebellum delays predictive head movements in the coordination of gaze.

PubMed

Zangemeister, W H; Nagel, M

2001-01-01

We investigated coordinated saccadic eye and head movements following predictive horizontal visual targets at +/- 30 degrees by applying transcranial magnetic stimulation (TMS) over the cerebellum before the start of the gaze movement in 10 young subjects. We found three effects of TMS on eye-head movements: 1. Saccadic latency effect. When stimulation took place shortly before movements commenced (75-25 ms before), significantly shorter latencies were found between predictive target presentation and initiation of saccades. Eye latencies were significantly decreased by 45 ms on average, but head latencies were not. 2. Gaze amplitude effect. Without TMS, for the 60 degrees target amplitudes, head movements usually preceded eye movements, as expected (predictive gaze type 3). With TMS 5-75 ms before the gaze movement, the number of eye movements preceding head movements by 20-50 ms was significantly increased (p < 0.001) and the delay between eye and head movements was reversed (p < 0.001), i.e. we found eye-predictive gaze type 1. 3. Saccadic peak velocity effect. For TMS 5-25 s before the start of head movement, mean peak velocity of synkinetic eye saccades increased by 20-30% up to 600 degrees/s, compared to 350-400 degrees/s without TMS. We conclude that transient functional cerebellar deficits exerted by means of TMS can change the central synkinesis of eye-head coordination, including the preprogramming of the saccadic pulse and step of a coordinated gaze movement.

Low Latency Audio Video: Potentials for Collaborative Music Making through Distance Learning

ERIC Educational Resources Information Center

Riley, Holly; MacLeod, Rebecca B.; Libera, Matthew

2016-01-01

The primary purpose of this study was to examine the potential of LOw LAtency (LOLA), a low latency audio visual technology designed to allow simultaneous music performance, as a distance learning tool for musical styles in which synchronous playing is an integral aspect of the learning process (e.g., jazz, folk styles). The secondary purpose was…

Excitation of the corticospinal tract by electromagnetic and electrical stimulation of the scalp in the macaque monkey.

PubMed Central

Edgley, S A; Eyre, J A; Lemon, R N; Miller, S

1990-01-01

1. The responses evoked by non-invasive electromagnetic and surface anodal electrical stimulation of the scalp (scalp stimulation) have been studied in the monkey. Conventional recording and stimulating electrodes, placed in the corticospinal pathway in the hand area of the left motor cortex, left medullary pyramid and the right spinal dorsolateral funiculus (DLF), allowed comparison of the actions of non-invasive stimuli and conventional electrical stimulation. 2. Responses to electromagnetic stimulation (with the coil tangential to the skull) were studied in four anaesthetized monkeys. In each case short-latency descending volleys were recorded in the contralateral DLF at threshold. In two animals later responses were also seen at higher stimulus intensities. Both early and late responses were of corticospinal origin since they could be completely collided by appropriately timed stimulation of the pyramidal tract. The latency of the early response in the DLF indicated that it resulted from direct activation of corticospinal neurones: its latency was the same as the latency of the antidromic action potentials evoked in the motor cortex from the recording site in the DLF. 3. Scalp stimulation, which was also investigated in three of the monkeys, evoked short-latency volleys at threshold and at higher stimulus intensities these were followed by later waves. The short-latency volleys could be collided from the pyramid and, at threshold, had latencies compatible with direct activation of corticospinal neurones. The longer latency volleys were also identified as corticospinal in origin. 4. The latency of the early volley evoked by electromagnetic stimulation remained constant with increasing stimulus intensities. In contrast, with scalp stimulation above threshold the latency of the early volleys decreased considerably, indicating remote activation of the corticospinal pathway below the level of the motor cortex. In two monkeys both collision and latency data suggest activation of the corticospinal pathway as far caudal as the medulla. 5. The majority of fast corticospinal fibres could be excited by scalp stimulation with intensities of 20% of maximum stimulator output. Electromagnetic stimulation at maximum stimulator output elicited a volley of between 70 and 90% of the size of the maximal volley evoked from the pyramidal electrodes. 6. Electromagnetic stimulation was also investigated in one awake monkey during the performance of a precision grip task. Short-latency EMG responses were evoked in hand and forearm muscles. The onsets of these responses were approximately 0.8 ms longer than the responses evoked by electrical stimulation of the pyramid.(ABSTRACT TRUNCATED AT 400 WORDS) Images Fig. 1 PMID:2213581

Enhanced Fine-Form Perception Does Not Contribute to Gestalt Face Perception in Autism Spectrum Disorder

PubMed Central

Maekawa, Toshihiko; Miyanaga, Yuka; Takahashi, Kenji; Takamiya, Naomi; Ogata, Katsuya; Tobimatsu, Shozo

2017-01-01

Individuals with autism spectrum disorder (ASD) show superior performance in processing fine detail, but often exhibit impaired gestalt face perception. The ventral visual stream from the primary visual cortex (V1) to the fusiform gyrus (V4) plays an important role in form (including faces) and color perception. The aim of this study was to investigate how the ventral stream is functionally altered in ASD. Visual evoked potentials were recorded in high-functioning ASD adults (n = 14) and typically developing (TD) adults (n = 14). We used three types of visual stimuli as follows: isoluminant chromatic (red/green, RG) gratings, high-contrast achromatic (black/white, BW) gratings with high spatial frequency (HSF, 5.3 cycles/degree), and face (neutral, happy, and angry faces) stimuli. Compared with TD controls, ASD adults exhibited longer N1 latency for RG, shorter N1 latency for BW, and shorter P1 latency, but prolonged N170 latency, for face stimuli. Moreover, a greater difference in latency between P1 and N170, or between N1 for BW and N170 (i.e., the prolongation of cortico-cortical conduction time between V1 and V4) was observed in ASD adults. These findings indicate that ASD adults have enhanced fine-form (local HSF) processing, but impaired color processing at V1. In addition, they exhibit impaired gestalt face processing due to deficits in integration of multiple local HSF facial information at V4. Thus, altered ventral stream function may contribute to abnormal social processing in ASD. PMID:28146575

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.

Visual Evoked Potentials in Infants With Diffuse Periventricular Leukomalacia.

PubMed

Carbajal-Valenzuela, Cintli Carolina; Santiago-Rodríguez, Efraín; Harmony, Thalía; Fernández-Bouzas, Antonio

2014-10-01

Periventricular leukomalacia (PVL) is characterized by necrosis of the cerebral white matter in the dorsolateral portions of the lateral ventricles. PVL causes motor, sensory, and cognitive deficits. The aim of this study was to analyze the conduction characteristics of the visual pathway in infants with diffuse PVL using visual evoked potentials (VEPs). We studied 11 healthy infants (mean age 3.3 ± 1.3 months) and 17 with diffuse PVL (mean age 2.9 ± 0.8 months and mean gestational age 31.9 ± 3.1 weeks). The N75, P100, and N135 wave latencies; the interwave N75-P100 and P100-N135 latencies; and the N75-P100 and P100-N135 amplitudes were measured in the occipital leads. VEPs were recorded during binocular stimulation at an angle of 120' from the Fz-Oz lead. Healthy children had mean N75, P100, and N135 wave latencies of 84.4 ± 5.8, 143.4 ± 30.6 and 222.9 ± 40.4 ms, respectively. The mean interwave N75-P100 and P100-N135 latencies were 59.0 ± 28.6 and 79.5 ± 13.6 ms, respectively. Compared with the healthy group, infants with PVL had longer N75 and N135 latencies at 92.3 ± 15.3 (P = .05) and 265.0 ms ± 60.3 (P = .05), respectively. The interwave latency P100-N135 (105.5 ± 29.1 ms; P = .017) was longer in children with PVL than in healthy infants. Infants with diffuse PVL had mild alterations in their N75, P100 and, particularly, their N135 latencies. These increases in P100-N135 interwave latencies could be because of damage to the geniculocortical pathways and V2-V3 networks. © EEG and Clinical Neuroscience Society (ECNS) 2014.

Aircraft Fault Detection Using Real-Time Frequency Response Estimation

NASA Technical Reports Server (NTRS)

Grauer, Jared A.

2016-01-01

A real-time method for estimating time-varying aircraft frequency responses from input and output measurements was demonstrated. The Bat-4 subscale airplane was used with NASA Langley Research Center's AirSTAR unmanned aerial flight test facility to conduct flight tests and collect data for dynamic modeling. Orthogonal phase-optimized multisine inputs, summed with pilot stick and pedal inputs, were used to excite the responses. The aircraft was tested in its normal configuration and with emulated failures, which included a stuck left ruddervator and an increased command path latency. No prior knowledge of a dynamic model was used or available for the estimation. The longitudinal short period dynamics were investigated in this work. Time-varying frequency responses and stability margins were tracked well using a 20 second sliding window of data, as compared to a post-flight analysis using output error parameter estimation and a low-order equivalent system model. This method could be used in a real-time fault detection system, or for other applications of dynamic modeling such as real-time verification of stability margins during envelope expansion tests.

A Brief Period of Postnatal Visual Deprivation Alters the Balance between Auditory and Visual Attention.

PubMed

de Heering, Adélaïde; Dormal, Giulia; Pelland, Maxime; Lewis, Terri; Maurer, Daphne; Collignon, Olivier

2016-11-21

Is a short and transient period of visual deprivation early in life sufficient to induce lifelong changes in how we attend to, and integrate, simple visual and auditory information [1, 2]? This question is of crucial importance given the recent demonstration in both animals and humans that a period of blindness early in life permanently affects the brain networks dedicated to visual, auditory, and multisensory processing [1-16]. To address this issue, we compared a group of adults who had been treated for congenital bilateral cataracts during early infancy with a group of normally sighted controls on a task requiring simple detection of lateralized visual and auditory targets, presented alone or in combination. Redundancy gains obtained from the audiovisual conditions were similar between groups and surpassed the reaction time distribution predicted by Miller's race model. However, in comparison to controls, cataract-reversal patients were faster at processing simple auditory targets and showed differences in how they shifted attention across modalities. Specifically, they were faster at switching attention from visual to auditory inputs than in the reverse situation, while an opposite pattern was observed for controls. Overall, these results reveal that the absence of visual input during the first months of life does not prevent the development of audiovisual integration but enhances the salience of simple auditory inputs, leading to a different crossmodal distribution of attentional resources between auditory and visual stimuli. Copyright © 2016 Elsevier Ltd. All rights reserved.

Temporal parameters and time course of perceptual latency priming.

PubMed

Scharlau, Ingrid; Neumann, Odmar

2003-06-01

Visual stimuli (primes) reduce the perceptual latency of a target appearing at the same location (perceptual latency priming, PLP). Three experiments assessed the time course of PLP by masked and, in Experiment 3, unmasked primes. Experiments 1 and 2 investigated the temporal parameters that determine the size of priming. Stimulus onset asynchrony was found to exert the main influence accompanied by a small effect of prime duration. Experiment 3 used a large range of priming onset asynchronies. We suggest to explain PLP by the Asynchronous Updating Model which relates it to the asynchrony of 2 central coding processes, preattentive coding of basic visual features and attentional orienting as a prerequisite for perceptual judgments and conscious perception.

Aging effects on the binaural interaction component of the auditory brainstem response in the Mongolian gerbil: Effects of interaural time and level differences.

PubMed

Laumen, Geneviève; Tollin, Daniel J; Beutelmann, Rainer; Klump, Georg M

2016-07-01

The effect of interaural time difference (ITD) and interaural level difference (ILD) on wave 4 of the binaural and summed monaural auditory brainstem responses (ABRs) as well as on the DN1 component of the binaural interaction component (BIC) of the ABR in young and old Mongolian gerbils (Meriones unguiculatus) was investigated. Measurements were made at a fixed sound pressure level (SPL) and a fixed level above visually detected ABR threshold to compensate for individual hearing threshold differences. In both stimulation modes (fixed SPL and fixed level above visually detected ABR threshold) an effect of ITD on the latency and the amplitude of wave 4 as well as of the BIC was observed. With increasing absolute ITD values BIC latencies were increased and amplitudes were decreased. ILD had a much smaller effect on these measures. Old animals showed a reduced amplitude of the DN1 component. This difference was due to a smaller wave 4 in the summed monaural ABRs of old animals compared to young animals whereas wave 4 in the binaural-evoked ABR showed no age-related difference. In old animals the small amplitude of the DN1 component was correlated with small binaural-evoked wave 1 and wave 3 amplitudes. This suggests that the reduced peripheral input affects central binaural processing which is reflected in the BIC. Copyright © 2016 Elsevier B.V. All rights reserved.

Fast Coding of Orientation in Primary Visual Cortex

PubMed Central

Shriki, Oren; Kohn, Adam; Shamir, Maoz

2012-01-01

Understanding how populations of neurons encode sensory information is a major goal of systems neuroscience. Attempts to answer this question have focused on responses measured over several hundred milliseconds, a duration much longer than that frequently used by animals to make decisions about the environment. How reliably sensory information is encoded on briefer time scales, and how best to extract this information, is unknown. Although it has been proposed that neuronal response latency provides a major cue for fast decisions in the visual system, this hypothesis has not been tested systematically and in a quantitative manner. Here we use a simple ‘race to threshold’ readout mechanism to quantify the information content of spike time latency of primary visual (V1) cortical cells to stimulus orientation. We find that many V1 cells show pronounced tuning of their spike latency to stimulus orientation and that almost as much information can be extracted from spike latencies as from firing rates measured over much longer durations. To extract this information, stimulus onset must be estimated accurately. We show that the responses of cells with weak tuning of spike latency can provide a reliable onset detector. We find that spike latency information can be pooled from a large neuronal population, provided that the decision threshold is scaled linearly with the population size, yielding a processing time of the order of a few tens of milliseconds. Our results provide a novel mechanism for extracting information from neuronal populations over the very brief time scales in which behavioral judgments must sometimes be made. PMID:22719237

Theoretical implications of quantitative properties of interval timing and probability estimation in mouse and rat.

PubMed

Kheifets, Aaron; Freestone, David; Gallistel, C R

2017-07-01

In three experiments with mice ( Mus musculus ) and rats (Rattus norvigicus), we used a switch paradigm to measure quantitative properties of the interval-timing mechanism. We found that: 1) Rodents adjusted the precision of their timed switches in response to changes in the interval between the short and long feed latencies (the temporal goalposts). 2) The variability in the timing of the switch response was reduced or unchanged in the face of large trial-to-trial random variability in the short and long feed latencies. 3) The adjustment in the distribution of switch latencies in response to changes in the relative frequency of short and long trials was sensitive to the asymmetry in the Kullback-Leibler divergence. The three results suggest that durations are represented with adjustable precision, that they are timed by multiple timers, and that there is a trial-by-trial (episodic) record of feed latencies in memory. © 2017 Society for the Experimental Analysis of Behavior.

Auditory-Cortex Short-Term Plasticity Induced by Selective Attention

PubMed Central

Jääskeläinen, Iiro P.; Ahveninen, Jyrki

2014-01-01

The ability to concentrate on relevant sounds in the acoustic environment is crucial for everyday function and communication. Converging lines of evidence suggests that transient functional changes in auditory-cortex neurons, “short-term plasticity”, might explain this fundamental function. Under conditions of strongly focused attention, enhanced processing of attended sounds can take place at very early latencies (~50 ms from sound onset) in primary auditory cortex and possibly even at earlier latencies in subcortical structures. More robust selective-attention short-term plasticity is manifested as modulation of responses peaking at ~100 ms from sound onset in functionally specialized nonprimary auditory-cortical areas by way of stimulus-specific reshaping of neuronal receptive fields that supports filtering of selectively attended sound features from task-irrelevant ones. Such effects have been shown to take effect in ~seconds following shifting of attentional focus. There are findings suggesting that the reshaping of neuronal receptive fields is even stronger at longer auditory-cortex response latencies (~300 ms from sound onset). These longer-latency short-term plasticity effects seem to build up more gradually, within tens of seconds after shifting the focus of attention. Importantly, some of the auditory-cortical short-term plasticity effects observed during selective attention predict enhancements in behaviorally measured sound discrimination performance. PMID:24551458

Preserving information in neural transmission.

PubMed

Sincich, Lawrence C; Horton, Jonathan C; Sharpee, Tatyana O

2009-05-13

Along most neural pathways, the spike trains transmitted from one neuron to the next are altered. In the process, neurons can either achieve a more efficient stimulus representation, or extract some biologically important stimulus parameter, or succeed at both. We recorded the inputs from single retinal ganglion cells and the outputs from connected lateral geniculate neurons in the macaque to examine how visual signals are relayed from retina to cortex. We found that geniculate neurons re-encoded multiple temporal stimulus features to yield output spikes that carried more information about stimuli than was available in each input spike. The coding transformation of some relay neurons occurred with no decrement in information rate, despite output spike rates that averaged half the input spike rates. This preservation of transmitted information was achieved by the short-term summation of inputs that geniculate neurons require to spike. A reduced model of the retinal and geniculate visual responses, based on two stimulus features and their associated nonlinearities, could account for >85% of the total information available in the spike trains and the preserved information transmission. These results apply to neurons operating on a single time-varying input, suggesting that synaptic temporal integration can alter the temporal receptive field properties to create a more efficient representation of visual signals in the thalamus than the retina.

Quality metrics for sensor images

NASA Technical Reports Server (NTRS)

Ahumada, AL

1993-01-01

Methods are needed for evaluating the quality of augmented visual displays (AVID). Computational quality metrics will help summarize, interpolate, and extrapolate the results of human performance tests with displays. The FLM Vision group at NASA Ames has been developing computational models of visual processing and using them to develop computational metrics for similar problems. For example, display modeling systems use metrics for comparing proposed displays, halftoning optimizing methods use metrics to evaluate the difference between the halftone and the original, and image compression methods minimize the predicted visibility of compression artifacts. The visual discrimination models take as input two arbitrary images A and B and compute an estimate of the probability that a human observer will report that A is different from B. If A is an image that one desires to display and B is the actual displayed image, such an estimate can be regarded as an image quality metric reflecting how well B approximates A. There are additional complexities associated with the problem of evaluating the quality of radar and IR enhanced displays for AVID tasks. One important problem is the question of whether intruding obstacles are detectable in such displays. Although the discrimination model can handle detection situations by making B the original image A plus the intrusion, this detection model makes the inappropriate assumption that the observer knows where the intrusion will be. Effects of signal uncertainty need to be added to our models. A pilot needs to make decisions rapidly. The models need to predict not just the probability of a correct decision, but the probability of a correct decision by the time the decision needs to be made. That is, the models need to predict latency as well as accuracy. Luce and Green have generated models for auditory detection latencies. Similar models are needed for visual detection. Most image quality models are designed for static imagery. Watson has been developing a general spatial-temporal vision model to optimize video compression techniques. These models need to be adapted and calibrated for AVID applications.

Multifocal visual evoked potential and automated perimetry abnormalities in strabismic amblyopes.

PubMed

Greenstein, Vivienne C; Eggers, Howard M; Hood, Donald C

2008-02-01

To compare visual field abnormalities obtained with standard automated perimetry (SAP) to those obtained with the multifocal visual evoked potential (mfVEP) technique in strabismic amblyopes. Humphrey 24-2 visual fields (HVF) and mfVEPs were obtained from each eye of 12 strabismic amblyopes. For the mfVEP, amplitudes and latencies were analyzed and probability plots were derived. Multifocal VEP and HVF hemifields were abnormal if they had clusters of two or more contiguous points at p < 0.01, or three or more contiguous points at p < 0.05 with at least one at p < 0.01. An eye was abnormal if it had an abnormal hemifield. On SAP, amblyopic eyes had significantly higher foveal thresholds (p = 0.003) and lower mean deviation values (p = 0.005) than fellow eyes. For the mfVEP, 11 amblyopic and 6 fellow eyes were abnormal. Of the 11 amblyopic eyes, 6 were abnormal on SAP. The deficits extended from the center to mid periphery. Monocular mfVEP latencies were significantly decreased for amblyopic eyes compared with control eyes (p < 0.0002). Both techniques revealed deficits in visual function across the visual field in strabismic amblyopes, but the mfVEP revealed deficits in fellow eyes and in more amblyopic eyes. In addition, mfVEP response latencies for amblyopic eyes were shorter than normal.

Age-related slowing of response selection and production in a visual choice reaction time task

PubMed Central

Woods, David L.; Wyma, John M.; Yund, E. William; Herron, Timothy J.; Reed, Bruce

2015-01-01

Aging is associated with delayed processing in choice reaction time (CRT) tasks, but the processing stages most impacted by aging have not been clearly identified. Here, we analyzed CRT latencies in a computerized serial visual feature-conjunction task. Participants responded to a target letter (probability 40%) by pressing one mouse button, and responded to distractor letters differing either in color, shape, or both features from the target (probabilities 20% each) by pressing the other mouse button. Stimuli were presented randomly to the left and right visual fields and stimulus onset asynchronies (SOAs) were adaptively reduced following correct responses using a staircase procedure. In Experiment 1, we tested 1466 participants who ranged in age from 18 to 65 years. CRT latencies increased significantly with age (r = 0.47, 2.80 ms/year). Central processing time (CPT), isolated by subtracting simple reaction times (SRT) (obtained in a companion experiment performed on the same day) from CRT latencies, accounted for more than 80% of age-related CRT slowing, with most of the remaining increase in latency due to slowed motor responses. Participants were faster and more accurate when the stimulus location was spatially compatible with the mouse button used for responding, and this effect increased slightly with age. Participants took longer to respond to distractors with target color or shape than to distractors with no target features. However, the additional time needed to discriminate the more target-like distractors did not increase with age. In Experiment 2, we replicated the findings of Experiment 1 in a second population of 178 participants (ages 18–82 years). CRT latencies did not differ significantly in the two experiments, and similar effects of age, distractor similarity, and stimulus-response spatial compatibility were found. The results suggest that the age-related slowing in visual CRT latencies is largely due to delays in response selection and production. PMID:25954175

Fuzzy Logic based Handoff Latency Reduction Mechanism in Layer 2 of Heterogeneous Mobile IPv6 Networks

NASA Astrophysics Data System (ADS)

Anwar, Farhat; Masud, Mosharrof H.; Latif, Suhaimi A.

2013-12-01

Mobile IPv6 (MIPv6) is one of the pioneer standards that support mobility in IPv6 environment. It has been designed to support different types of technologies for providing seamless communications in next generation network. However, MIPv6 and subsequent standards have some limitations due to its handoff latency. In this paper, a fuzzy logic based mechanism is proposed to reduce the handoff latency of MIPv6 for Layer 2 (L2) by scanning the Access Points (APs) while the Mobile Node (MN) is moving among different APs. Handoff latency occurs when the MN switches from one AP to another in L2. Heterogeneous network is considered in this research in order to reduce the delays in L2. Received Signal Strength Indicator (RSSI) and velocity of the MN are considered as the input of fuzzy logic technique. This technique helps the MN to measure optimum signal quality from APs for the speedy mobile node based on fuzzy logic input rules and makes a list of interfaces. A suitable interface from the list of available interfaces can be selected like WiFi, WiMAX or GSM. Simulation results show 55% handoff latency reduction and 50% packet loss improvement in L2 compared to standard to MIPv6.

Immersive Molecular Visualization with Omnidirectional Stereoscopic Ray Tracing and Remote Rendering

PubMed Central

Stone, John E.; Sherman, William R.; Schulten, Klaus

2016-01-01

Immersive molecular visualization provides the viewer with intuitive perception of complex structures and spatial relationships that are of critical interest to structural biologists. The recent availability of commodity head mounted displays (HMDs) provides a compelling opportunity for widespread adoption of immersive visualization by molecular scientists, but HMDs pose additional challenges due to the need for low-latency, high-frame-rate rendering. State-of-the-art molecular dynamics simulations produce terabytes of data that can be impractical to transfer from remote supercomputers, necessitating routine use of remote visualization. Hardware-accelerated video encoding has profoundly increased frame rates and image resolution for remote visualization, however round-trip network latencies would cause simulator sickness when using HMDs. We present a novel two-phase rendering approach that overcomes network latencies with the combination of omnidirectional stereoscopic progressive ray tracing and high performance rasterization, and its implementation within VMD, a widely used molecular visualization and analysis tool. The new rendering approach enables immersive molecular visualization with rendering techniques such as shadows, ambient occlusion lighting, depth-of-field, and high quality transparency, that are particularly helpful for the study of large biomolecular complexes. We describe ray tracing algorithms that are used to optimize interactivity and quality, and we report key performance metrics of the system. The new techniques can also benefit many other application domains. PMID:27747138

Sensitivity of visual evoked potentials and spectral domain optical coherence tomography in early relapsing remitting multiple sclerosis.

PubMed

Behbehani, Raed; Ahmed, Samar; Al-Hashel, Jasem; Rousseff, Rossen T; Alroughani, Raed

2017-02-01

Visual evoked potentials and spectral-domain optical coherence tomography are common ancillary studies that assess the visual pathways from a functional and structural aspect, respectively. To compare prevalence of abnormalities of Visual evoked potentials (VEP) and spectral-domain optical coherence tomography (SDOCT) in patients with relapsing remitting multiple sclerosis (RRMS). A cross-sectional study of 100 eyes with disease duration of less than 5 years since the diagnosis. Correlation between retinal nerve fiber layer and ganglion-cell/inner plexiform layer with pattern-reversal visual evoked potentials amplitude and latency and contrast sensitivity was performed. The prevalence of abnormalities in pattern-reversal visual VEP was 56% while that of SOCT was 48% in all eyes. There was significant negative correlations between the average RNFL (r=-0.34, p=0.001) and GCIPL (r=-0.39, p<0.001) with VEP latency. In eyes with prior optic neuritis, a significant negative correlation was seen between average RNFL (r=-0.33, p=0.037) and GCIPL (r=-0.40, p=0.010) with VEP latency. We have found higher prevalence of VEP abnormalities than SCOCT in early relapsing-remitting multiple sclerosis. This suggests that VEP has a higher sensitivity for detecting lesions of the visual pathway in patients with early RRMS. Copyright © 2016 Elsevier B.V. All rights reserved.

Modelling Transposition Latencies: Constraints for Theories of Serial Order Memory

ERIC Educational Resources Information Center

Farrell, Simon; Lewandowsky, Stephan

2004-01-01

Several competing theories of short-term memory can explain serial recall performance at a quantitative level. However, most theories to date have not been applied to the accompanying pattern of response latencies, thus ignoring a rich and highly diagnostic aspect of performance. This article explores and tests the error latency predictions of…

Short-term Synaptic Depression in the Feedforward Inhibitory Circuit in the Dorsal Lateral Geniculate Nucleus.

PubMed

Augustinaite, Sigita; Heggelund, Paul

2018-05-24

Synaptic short-term plasticity (STP) regulates synaptic transmission in an activity-dependent manner and thereby has important roles in the signal processing in the brain. In some synapses, a presynaptic train of action potentials elicits post-synaptic potentials that gradually increase during the train (facilitation), but in other synapses, these potentials gradually decrease (depression). We studied STP in neurons in the visual thalamic relay, the dorsal lateral geniculate nucleus (dLGN). The dLGN contains two types of neurons: excitatory thalamocortical (TC) neurons, which transfer signals from retinal afferents to visual cortex, and local inhibitory interneurons, which form an inhibitory feedforward loop that regulates the thalamocortical signal transmission. The overall STP in the retino-thalamic relay is short-term depression, but the distinct kind and characteristics of the plasticity at the different types of synapses are unknown. We studied STP in the excitatory responses of interneurons to stimulation of retinal afferents, in the inhibitory responses of TC neurons to stimulation of afferents from interneurons, and in the disynaptic inhibitory responses of TC neurons to stimulation of retinal afferents. Moreover, we studied STP at the direct excitatory input to TC neurons from retinal afferents. The STP at all types of the synapses showed short-term depression. This depression can accentuate rapid changes in the stream of signals and thereby promote detectability of significant features in the sensory input. In vision, detection of edges and contours is essential for object perception, and the synaptic short-term depression in the early visual pathway provides important contributions to this detection process. Copyright © 2018 IBRO. Published by Elsevier Ltd. All rights reserved.

Shielding cognition from nociception with working memory.

PubMed

Legrain, Valéry; Crombez, Geert; Plaghki, Léon; Mouraux, André

2013-01-01

Because pain often signals the occurrence of potential tissue damage, nociceptive stimuli have the capacity to capture attention and interfere with ongoing cognitive activities. Working memory is known to guide the orientation of attention by maintaining goal priorities active during the achievement of a task. This study investigated whether the cortical processing of nociceptive stimuli and their ability to capture attention are under the control of working memory. Event-related brain potentials (ERPs) were recorded while participants performed primary tasks on visual targets that required or did not require rehearsal in working memory (1-back vs 0-back conditions). The visual targets were shortly preceded by task-irrelevant tactile stimuli. Occasionally, in order to distract the participants, the tactile stimuli were replaced by novel nociceptive stimuli. In the 0-back conditions, task performance was disrupted by the occurrence of the nociceptive distracters, as reflected by the increased reaction times in trials with novel nociceptive distracters as compared to trials with standard tactile distracters. In the 1-back conditions, such a difference disappeared suggesting that attentional capture and task disruption induced by nociceptive distracters were suppressed by working memory, regardless of task demands. Most importantly, in the conditions involving working memory, the magnitude of nociceptive ERPs, including ERP components at early latency, were significantly reduced. This indicates that working memory is able to modulate the cortical processing of nociceptive input already at its earliest stages, and could explain why working memory reduces consequently ability of nociceptive stimuli to capture attention and disrupt performance of the primary task. It is concluded that protecting cognitive processing against pain interference is best guaranteed by keeping out of working memory pain-related information. Copyright © 2012 Elsevier Ltd. All rights reserved.

Attentional gain and processing capacity limits predict the propensity to neglect unexpected visual stimuli.

PubMed

Papera, Massimiliano; Richards, Anne

2016-05-01

Exogenous allocation of attentional resources allows the visual system to encode and maintain representations of stimuli in visual working memory (VWM). However, limits in the processing capacity to allocate resources can prevent unexpected visual stimuli from gaining access to VWM and thereby to consciousness. Using a novel approach to create unbiased stimuli of increasing saliency, we investigated visual processing during a visual search task in individuals who show a high or low propensity to neglect unexpected stimuli. When propensity to inattention is high, ERP recordings show a diminished amplification concomitantly with a decrease in theta band power during the N1 latency, followed by a poor target enhancement during the N2 latency. Furthermore, a later modulation in the P3 latency was also found in individuals showing propensity to visual neglect, suggesting that more effort is required for conscious maintenance of visual information in VWM. Effects during early stages of processing (N80 and P1) were also observed suggesting that sensitivity to contrasts and medium-to-high spatial frequencies may be modulated by low-level saliency (albeit no statistical group differences were found). In accordance with the Global Workplace Model, our data indicate that a lack of resources in low-level processors and visual attention may be responsible for the failure to "ignite" a state of high-level activity spread across several brain areas that is necessary for stimuli to access awareness. These findings may aid in the development of diagnostic tests and intervention to detect/reduce inattention propensity to visual neglect of unexpected stimuli. © 2016 Society for Psychophysiological Research.

Crossmodal Connections of Primary Sensory Cortices Largely Vanish During Normal Aging

PubMed Central

Henschke, Julia U.; Ohl, Frank W.; Budinger, Eike

2018-01-01

During aging, human response times (RTs) to unisensory and crossmodal stimuli decrease. However, the elderly benefit more from crossmodal stimulus representations than younger people. The underlying short-latency multisensory integration process is mediated by direct crossmodal connections at the level of primary sensory cortices. We investigate the age-related changes of these connections using a rodent model (Mongolian gerbil), retrograde tracer injections into the primary auditory (A1), somatosensory (S1), and visual cortex (V1), and immunohistochemistry for markers of apoptosis (Caspase-3), axonal plasticity (Growth associated protein 43, GAP 43), and a calcium-binding protein (Parvalbumin, PV). In adult animals, primary sensory cortices receive a substantial number of direct thalamic inputs from nuclei of their matched, but also from nuclei of non-matched sensory modalities. There are also direct intracortical connections among primary sensory cortices and connections with secondary sensory cortices of other modalities. In very old animals, the crossmodal connections strongly decrease in number or vanish entirely. This is likely due to a retraction of the projection neuron axonal branches rather than ongoing programmed cell death. The loss of crossmodal connections is also accompanied by changes in anatomical correlates of inhibition and excitation in the sensory thalamus and cortex. Together, the loss and restructuring of crossmodal connections during aging suggest a shift of multisensory processing from primary cortices towards other sensory brain areas in elderly individuals. PMID:29551970

Crossmodal Connections of Primary Sensory Cortices Largely Vanish During Normal Aging.

PubMed

Henschke, Julia U; Ohl, Frank W; Budinger, Eike

2018-01-01

During aging, human response times (RTs) to unisensory and crossmodal stimuli decrease. However, the elderly benefit more from crossmodal stimulus representations than younger people. The underlying short-latency multisensory integration process is mediated by direct crossmodal connections at the level of primary sensory cortices. We investigate the age-related changes of these connections using a rodent model (Mongolian gerbil), retrograde tracer injections into the primary auditory (A1), somatosensory (S1), and visual cortex (V1), and immunohistochemistry for markers of apoptosis (Caspase-3), axonal plasticity (Growth associated protein 43, GAP 43), and a calcium-binding protein (Parvalbumin, PV). In adult animals, primary sensory cortices receive a substantial number of direct thalamic inputs from nuclei of their matched, but also from nuclei of non-matched sensory modalities. There are also direct intracortical connections among primary sensory cortices and connections with secondary sensory cortices of other modalities. In very old animals, the crossmodal connections strongly decrease in number or vanish entirely. This is likely due to a retraction of the projection neuron axonal branches rather than ongoing programmed cell death. The loss of crossmodal connections is also accompanied by changes in anatomical correlates of inhibition and excitation in the sensory thalamus and cortex. Together, the loss and restructuring of crossmodal connections during aging suggest a shift of multisensory processing from primary cortices towards other sensory brain areas in elderly individuals.

Index finger somatosensory evoked potentials in blind Braille readers.

PubMed

Giriyappa, Dayananda; Subrahmanyam, Roopakala Mysore; Rangashetty, Srinivasa; Sharma, Rajeev

2009-01-01

Traditionally, vision has been considered the dominant modality in our multi-sensory perception of the surrounding world. Sensory input via non-visual tracts becomes of greater behavioural relevance in totally blind individuals to enable effective interaction with the world around them. These include audition and tactile perceptions, leading to an augmentation in these perceptions when compared with normal sighted individuals. The objective of the present work was to study the index finger somatosensory evoked potentials (SEPs) in totally blind and normal sighted individuals. SEPs were recorded in 15 Braille reading totally blind females and compared with 15 age-matched normal sighted females. Latency and amplitudes of somatosensory evoked potential waveforms (N9, N13, and N20) were measured. Amplitude of N20 SEP (a cortical somatosensory evoked potential) was significantly larger in the totally blind than in normal sighted individuals (p < 0.05). The amplitudes of N9 and N13 SEP and the latencies of all recorded SEPs showed no significant differences. Blindness has a profound effect on the Braille reading right index finger. Totally blind Braille readers have larger N20 amplitude, suggestive of greater somatosensory cortical representation of the Braille reading index finger.

Development of visual evoked potentials in neonates. A study using light emitting diode goggles.

PubMed Central

Chin, K C; Taylor, M J; Menzies, R; Whyte, H

1985-01-01

We used a signal averager with light emitting diode goggles as the photostimulator to study the development of the visual evoked potentials in 40 normal neonates of between 23 and 42 weeks' gestation. All except two infants of less than 24 weeks' gestation had replicable visual evoked potentials. A negative peak of latency (mean (SD), 308 (21) msec) was present in all infants, but the development of the primary positive peak depended on maturity. Only infants of 37 weeks or more had a consistent positive peak of latency (mean (SD), 220 (22) msec). The practical simplicity and reliability of this technique has distinct advantages over previous conventional recording systems. Neonatal visual evoked potentials are shown to change with maturity. PMID:4091582

A Feedback Model of Attention Explains the Diverse Effects of Attention on Neural Firing Rates and Receptive Field Structure.

PubMed

Miconi, Thomas; VanRullen, Rufin

2016-02-01

Visual attention has many effects on neural responses, producing complex changes in firing rates, as well as modifying the structure and size of receptive fields, both in topological and feature space. Several existing models of attention suggest that these effects arise from selective modulation of neural inputs. However, anatomical and physiological observations suggest that attentional modulation targets higher levels of the visual system (such as V4 or MT) rather than input areas (such as V1). Here we propose a simple mechanism that explains how a top-down attentional modulation, falling on higher visual areas, can produce the observed effects of attention on neural responses. Our model requires only the existence of modulatory feedback connections between areas, and short-range lateral inhibition within each area. Feedback connections redistribute the top-down modulation to lower areas, which in turn alters the inputs of other higher-area cells, including those that did not receive the initial modulation. This produces firing rate modulations and receptive field shifts. Simultaneously, short-range lateral inhibition between neighboring cells produce competitive effects that are automatically scaled to receptive field size in any given area. Our model reproduces the observed attentional effects on response rates (response gain, input gain, biased competition automatically scaled to receptive field size) and receptive field structure (shifts and resizing of receptive fields both spatially and in complex feature space), without modifying model parameters. Our model also makes the novel prediction that attentional effects on response curves should shift from response gain to contrast gain as the spatial focus of attention drifts away from the studied cell.

Influence of visual angle on pattern reversal visual evoked potentials

PubMed Central

Kothari, Ruchi; Singh, Smita; Singh, Ramji; Shukla, A. K.; Bokariya, Pradeep

2014-01-01

Purpose: The aim of this study was to find whether the visual evoked potential (VEP) latencies and amplitude are altered with different visual angles in healthy adult volunteers or not and to determine the visual angle which is the optimum and most appropriate among a wide range of check sizes for the reliable interpretation of pattern reversal VEPs (PRVEPs). Materials and Methods: The present study was conducted on 40 healthy volunteers. The subjects were divided into two groups. One group consisted of 20 individuals (nine males and 11 females) in the age range of 25-57 years and they were exposed to checks subtending a visual angle of 90, 120, and 180 minutes of arc. Another group comprised of 20 individuals (10 males and 10 females) in the age range of 36-60 years and they were subjected to checks subtending a visual angle of 15, 30, and 120 minutes of arc. The stimulus configuration comprised of the transient pattern reversal method in which a black and white checker board is generated (full field) on a VEP Monitor by an Evoked Potential Recorder (RMS EMG. EPMARK II). The statistical analysis was done by One Way Analysis of Variance (ANOVA) using EPI INFO 6. Results: In Group I, the maximum (max.) P100 latency of 98.8 ± 4.7 and the max. P100 amplitude of 10.05 ± 3.1 μV was obtained with checks of 90 minutes. In Group II, the max. P100 latency of 105.19 ± 4.75 msec as well as the max. P100 amplitude of 8.23 ± 3.30 μV was obtained with 15 minutes. The min. P100 latency in both the groups was obtained with checks of 120 minutes while the min. P100 amplitude was obtained with 180 minutes. A statistically significant difference was derived between means of P100 latency for 15 and 30 minutes with reference to its value for 120 minutes and between the mean value of P100 amplitude for 120 minutes and that of 90 and 180 minutes. Conclusion: Altering the size of stimulus (visual angle) has an effect on the PRVEP parameters. Our study found that the 120 is the appropriate (and optimal) check size that can be used for accurate interpretation of PRVEPs. This will help in better assessment of the optic nerve function and integrity of anterior visual pathways. PMID:25378875

[Visual input affects the expression of the early genes c-Fos and ZENK in auditory telencephalic centers of pied flycatcher nestlings during the acoustically-guided freezing].

PubMed

Korneeva, E V; Tiunova, A A; Aleksandrov, L I; Golubeva, T B; Anokhin, K V

2014-01-01

The present study analyzed expression of transcriptional factors c-Fos and ZENK in 9-day-old pied flycatcher nestlings' (Ficedula hypoleuca) telencephalic auditory centers (field L, caudomedial nidopallium and caudomedial mesopallium) involved in the acoustically-guided defense behavior. Species-typical alarm call was presented to the young in three groups: 1--intact group (sighted control), 2--nestlings visually deprived just before the experiment for a short time (unsighted control) 3--nestlings visually deprived right after hatching (experimental deprivation). Induction of c-Fos as well as ZENK in nestlings from the experimental deprivation group was decreased in both hemispheres as compared with intact group. In the group of unsighted control, only the decrease of c-Fos induction was observed exclusively in the right hemisphere. These findings suggest that limitation of visual input changes the population of neurons involved into the acoustically-guided behavior, the effect being dependant from the duration of deprivation.

Normalization of sensorimotor integration by repetitive transcranial magnetic stimulation in cervical dystonia.

PubMed

Zittel, S; Helmich, R C; Demiralay, C; Münchau, A; Bäumer, T

2015-08-01

Previous studies indicated that sensorimotor integration and plasticity of the sensorimotor system are impaired in dystonia patients. We investigated motor evoked potential amplitudes and short latency afferent inhibition to examine corticospinal excitability and cortical sensorimotor integration, before and after inhibitory 1 Hz repetitive transcranial magnetic stimulation over primary sensory and primary motor cortex in patients with cervical dystonia (n = 12). Motor evoked potentials were recorded from the right first dorsal interosseous muscle after application of unconditioned transcranial magnetic test stimuli and after previous conditioning electrical stimulation of the right index finger at short interstimulus intervals of 25, 30 and 40 ms. Results were compared to a group of healthy age-matched controls. At baseline, motor evoked potential amplitudes did not differ between groups. Short latency afferent inhibition was reduced in cervical dystonia patients compared to healthy controls. Inhibitory 1 Hz sensory cortex repetitive transcranial magnetic stimulation but not motor cortex repetitive transcranial magnetic stimulation increased motor evoked potential amplitudes in cervical dystonia patients. Additionally, both 1 Hz repetitive transcranial magnetic stimulation over primary sensory and primary motor cortex normalized short latency afferent inhibition in these patients. In healthy subjects, sensory repetitive transcranial magnetic stimulation had no influence on motor evoked potential amplitudes and short latency afferent inhibition. Plasticity of sensorimotor circuits is altered in cervical dystonia patients.

Persistent neurotoxicity from a battery fire: is cadmium the culprit?

PubMed

Kilburn, K H; McKinley, K L

1996-07-01

Two train conductors had chest tightness, painful breathing, muscle cramps, and nausea after fighting a fire in a battery box under a passenger coach. Shortly thereafter, they became anosmic and had excessive fatigue, persistent headaches, sleep disturbances, irritability, unstable moods, and hypertension. Urinary cadmium and nickel levels were elevated. Neurobehavioral testing showed, in comparison to referents, prolonged reaction times, abnormal balance, prolonged blink reflex latency, severely constricted visual fields, and decreased vibration sense. Test scores showed that immediate verbal and visual recall were normal but delayed recall was reduced. Scores on overlearned information were normal. Tests measuring dexterity, coordination, decision making, and peripheral sensation and discrimination revealed abnormalities. Repeat testing 6 and 12 months after exposure showed persistent abnormalities. Cadmium and vinyl chloride are the most plausible causes of the neurotoxicity, but fumes from the fire may have contained other neurotoxic chemicals.

The effect of transdermal nicotine patches on sleep and dreams.

PubMed

Page, F; Coleman, G; Conduit, R

2006-07-30

This study was undertaken to determine the effect of 24-h transdermal nicotine patches on sleep and dream mentation in 15 smokers aged 20 to 33. Utilising a repeated measures design, it was found that more time awake and more ASDA micro-arousals occurred while wearing the nicotine patch compared to placebo. Also, the percentage of REM sleep decreased, but REM latency and the proportion of time spent in NREM sleep stages did not change significantly. Dream reports containing visual imagery, visual imagery ratings and the number of visualizable nouns were significantly greater from REM compared to Stage 2 awakenings, regardless of patch condition. However, a general interaction effect was observed. Stage 2 dream variables remained equivalent across nicotine and placebo conditions. Within REM sleep, more dream reports containing visual imagery occurred while wearing the nicotine patch, and these were rated as more vivid. The greater frequency of visual imagery reports and higher imagery ratings specifically from REM sleep suggests that previously reported dreaming side effects from 24-h nicotine patches may be specific to REM sleep. Combined with previous animal studies showing that transdermally delivered nicotine blocks PGO activity in REM sleep, the current results do no appear consistent with PGO-based hypotheses of dreaming, such as the Activation-Synthesis (AS) or Activation, Input and Modulation (AIM) models.

Effects of Reduced Acuity and Stereo Acuity on Saccades and Reaching Movements in Adults With Amblyopia and Strabismus.

PubMed

Niechwiej-Szwedo, Ewa; Goltz, Herbert C; Colpa, Linda; Chandrakumar, Manokaraananthan; Wong, Agnes M F

2017-02-01

Our previous work has shown that amblyopia disrupts the planning and execution of visually-guided saccadic and reaching movements. We investigated the association between the clinical features of amblyopia and aspects of visuomotor behavior that are disrupted by amblyopia. A total of 55 adults with amblyopia (22 anisometropic, 18 strabismic, 15 mixed mechanism), 14 adults with strabismus without amblyopia, and 22 visually-normal control participants completed a visuomotor task while their eye and hand movements were recorded. Univariate and multivariate analyses were performed to assess the association between three clinical predictors of amblyopia (amblyopic eye [AE] acuity, stereo sensitivity, and eye deviation) and seven kinematic outcomes, including saccadic and reach latency, interocular saccadic and reach latency difference, saccadic and reach precision, and PA/We ratio (an index of reach control strategy efficacy using online feedback correction). Amblyopic eye acuity explained 28% of the variance in saccadic latency, and 48% of the variance in mean saccadic latency difference between the amblyopic and fellow eyes (i.e., interocular latency difference). In contrast, for reach latency, AE acuity explained only 10% of the variance. Amblyopic eye acuity was associated with reduced endpoint saccadic (23% of variance) and reach (22% of variance) precision in the amblyopic group. In the strabismus without amblyopia group, stereo sensitivity and eye deviation did not explain any significant variance in saccadic and reach latency or precision. Stereo sensitivity was the best clinical predictor of deficits in reach control strategy, explaining 23% of total variance of PA/We ratio in the amblyopic group and 12% of variance in the strabismus without amblyopia group when viewing with the amblyopic/nondominant eye. Deficits in eye and limb movement initiation (latency) and target localization (precision) were associated with amblyopic acuity deficit, whereas changes in the sensorimotor reach strategy were associated with deficits in stereopsis. Importantly, more than 50% of variance was not explained by the measured clinical features. Our findings suggest that other factors, including higher order visual processing and attention, may have an important role in explaining the kinematic deficits observed in amblyopia.

Improvement in conduction velocity after optic neuritis measured with the multifocal VEP.

PubMed

Yang, E Bo; Hood, Donald C; Rodarte, Chris; Zhang, Xian; Odel, Jeffrey G; Behrens, Myles M

2007-02-01

To test the efficacy of the multifocal visual evoked potential (mfVEP) technique after long-term latency changes in optic neuritis (ON)/multiple sclerosis (MS), mfVEPs were recorded in 12 patients with ON/MS. Sixty local VEP responses were recorded simultaneously. mfVEP was recorded from both eyes of 12 patients with ON/MS. Patients were tested twice after recovery from acute ON episodes, which occurred in 14 of the 24 eyes. After recovery, all eyes had 20/20 or better visual acuity and normal visual fields as measured with static automated perimetry (SAP). The time between the two postrecovery tests varied from 6 to 56 months. Between test days, the visual fields obtained with SAP remained normal. Ten of the 14 affected eyes showed improvement in median latency on the mfVEP. Six of these eyes fell at or below (improved latency) the 96% confidence interval for the control eyes. None of the 10 initially unaffected eyes fell below the 96% lower limit. Although the improvement was widespread across the field, it did not include all regions. For the six eyes showing clear improvement, on average, 78% of the points had latencies that were shorter on test 2 than on test 1. A substantial percentage of ON/MS patients show a long-term improvement in conduction velocity. Because this improvement can be local, the mfVEP should allow these improvements to be monitored in patients with ON/MS.

Short-Term Memory Trace in Rapidly Adapting Synapses of Inferior Temporal Cortex

PubMed Central

Sugase-Miyamoto, Yasuko; Liu, Zheng; Wiener, Matthew C.; Optican, Lance M.; Richmond, Barry J.

2008-01-01

Visual short-term memory tasks depend upon both the inferior temporal cortex (ITC) and the prefrontal cortex (PFC). Activity in some neurons persists after the first (sample) stimulus is shown. This delay-period activity has been proposed as an important mechanism for working memory. In ITC neurons, intervening (nonmatching) stimuli wipe out the delay-period activity; hence, the role of ITC in memory must depend upon a different mechanism. Here, we look for a possible mechanism by contrasting memory effects in two architectonically different parts of ITC: area TE and the perirhinal cortex. We found that a large proportion (80%) of stimulus-selective neurons in area TE of macaque ITCs exhibit a memory effect during the stimulus interval. During a sequential delayed matching-to-sample task (DMS), the noise in the neuronal response to the test image was correlated with the noise in the neuronal response to the sample image. Neurons in perirhinal cortex did not show this correlation. These results led us to hypothesize that area TE contributes to short-term memory by acting as a matched filter. When the sample image appears, each TE neuron captures a static copy of its inputs by rapidly adjusting its synaptic weights to match the strength of their individual inputs. Input signals from subsequent images are multiplied by those synaptic weights, thereby computing a measure of the correlation between the past and present inputs. The total activity in area TE is sufficient to quantify the similarity between the two images. This matched filter theory provides an explanation of what is remembered, where the trace is stored, and how comparison is done across time, all without requiring delay period activity. Simulations of a matched filter model match the experimental results, suggesting that area TE neurons store a synaptic memory trace during short-term visual memory. PMID:18464917

Auditory and audio-visual processing in patients with cochlear, auditory brainstem, and auditory midbrain implants: An EEG study.

PubMed

Schierholz, Irina; Finke, Mareike; Kral, Andrej; Büchner, Andreas; Rach, Stefan; Lenarz, Thomas; Dengler, Reinhard; Sandmann, Pascale

2017-04-01

There is substantial variability in speech recognition ability across patients with cochlear implants (CIs), auditory brainstem implants (ABIs), and auditory midbrain implants (AMIs). To better understand how this variability is related to central processing differences, the current electroencephalography (EEG) study compared hearing abilities and auditory-cortex activation in patients with electrical stimulation at different sites of the auditory pathway. Three different groups of patients with auditory implants (Hannover Medical School; ABI: n = 6, CI: n = 6; AMI: n = 2) performed a speeded response task and a speech recognition test with auditory, visual, and audio-visual stimuli. Behavioral performance and cortical processing of auditory and audio-visual stimuli were compared between groups. ABI and AMI patients showed prolonged response times on auditory and audio-visual stimuli compared with NH listeners and CI patients. This was confirmed by prolonged N1 latencies and reduced N1 amplitudes in ABI and AMI patients. However, patients with central auditory implants showed a remarkable gain in performance when visual and auditory input was combined, in both speech and non-speech conditions, which was reflected by a strong visual modulation of auditory-cortex activation in these individuals. In sum, the results suggest that the behavioral improvement for audio-visual conditions in central auditory implant patients is based on enhanced audio-visual interactions in the auditory cortex. Their findings may provide important implications for the optimization of electrical stimulation and rehabilitation strategies in patients with central auditory prostheses. Hum Brain Mapp 38:2206-2225, 2017. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Visual and brainstem auditory evoked potentials in children with obesity.

PubMed

Akın, Onur; Arslan, Mutluay; Akgün, Hakan; Yavuz, Süleyman Tolga; Sarı, Erkan; Taşçılar, Mehmet Emre; Ulaş, Ümit Hıdır; Yeşilkaya, Ediz; Ünay, Bülent

2016-03-01

The aim of our study is to investigate alterations in visual evoked potentials (VEP) and brainstem auditory evoked potentials (BAEP) in children with obesity. A total of 96 children, with a mean age of 12.1±2.0 years (range 9-17 years, 63 obese and 33 age and sex-matched control subjects) were included in the study. Laboratory tests were performed to detect insulin resistance (IR) and dyslipidemia. The latencies and amplitudes of VEP and BAEP were measured in healthy and obese subjects. The VEP P100, BAEP interpeak latency (IPL) I-III and IPL I-V averages of obese children were significantly longer than the control subjects. When the obese group was divided into two subgroups, those with IR and without IR, BAEP wave I, wave III and P100 wave latencies were found to be longer in the group with IR. A statistically significant correlation was observed between BAEP wave I latency, IPL I-V, IPL I-III and the homeostatic model assessment insulin resistance (HOMA IR) index and fasting insulin level. Our findings suggest that VEP and BAEP can be used to determine early subclinical on auditory and visual functions of obese children with insulin resistance. Copyright © 2015 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.

Effect of oculomotor vision rehabilitation on the visual-evoked potential and visual attention in mild traumatic brain injury.

PubMed

Yadav, Naveen K; Thiagarajan, Preethi; Ciuffreda, Kenneth J

2014-01-01

The purpose of the experiment was to investigate the effect of oculomotor vision rehabilitation (OVR) on the visual-evoked potential (VEP) and visual attention in the mTBI population. Subjects (n = 7) were adults with a history of mild traumatic brain injury (mTBI). Each received 9 hours of OVR over a 6-week period. The effects of OVR on VEP amplitude and latency, the attention-related alpha band (8-13 Hz) power (µV(2)) and the clinical Visual Search and Attention Test (VSAT) were assessed before and after the OVR. After the OVR, the VEP amplitude increased and its variability decreased. There was no change in VEP latency, which was normal. Alpha band power increased, as did the VSAT score, following the OVR. The significant changes in most test parameters suggest that OVR affects the visual system at early visuo-cortical levels, as well as other pathways which are involved in visual attention.

Input and output compensation for the cochlear traveling wave delay in wide-band ABR recordings: implications for small acoustic tumor detection.

PubMed

Don, Manuel; Elberling, Claus; Maloff, Erin

2009-02-01

The Stacked ABR (auditory brainstem response) attempts at the output of the auditory periphery to compensate for the temporal dispersion of neural activation caused by the cochlear traveling wave in response to click stimulation. Compensation can also be made at the input by using a chirp stimulus. It has been demonstrated that the Stacked ABR is sensitive to small tumors that are often missed by standard ABR latency measures. Because a chirp stimulus requires only a single data acquisition run whereas the Stacked ABR requires six, we try to evaluate some indirect evidence justifying the use of a chirp for small tumor detection. We compared the sensitivity and specificity of different Stacked ABRs formed by aligning the derived-band ABRs according to (1) the individual's peak latencies, (2) the group mean latencies, and (3) the modeled latencies used to develop a chirp. For tumor detection with a chosen sensitivity of 95%, a relatively high specificity of 85% may be achieved with a chirp. It appears worthwhile to explore the actual use of a chirp because significantly shorter test and analysis times might be possible.

Social cues at encoding affect memory in 4-month-old infants.

PubMed

Kopp, Franziska; Lindenberger, Ulman

2012-01-01

Available evidence suggests that infants use adults' social cues for learning by the second half of the first year of life. However, little is known about the short-term or long-term effects of joint attention interactions on learning and memory in younger infants. In the present study, 4-month-old infants were familiarized with visually presented objects in either of two conditions that differed in the degree of joint attention (high vs. low). Brain activity in response to familiar and novel objects was assessed immediately after the familiarization phase (immediate recognition), and following a 1-week delay (delayed recognition). The latency of the Nc component differentiated between recognition of old versus new objects. Pb amplitude and latency were affected by joint attention in delayed recognition. Moreover, the frequency of infant gaze to the experimenter during familiarization differed between the two experimental groups and modulated the Pb response. Results show that joint attention affects the mechanisms of long-term retention in 4-month-old infants. We conclude that joint attention helps children at this young age to recognize the relevance of learned items.

Neurophysiological Effects of Meditation Based on Evoked and Event Related Potential Recordings

PubMed Central

Singh, Nilkamal; Telles, Shirley

2015-01-01

Evoked potentials (EPs) are a relatively noninvasive method to assess the integrity of sensory pathways. As the neural generators for most of the components are relatively well worked out, EPs have been used to understand the changes occurring during meditation. Event-related potentials (ERPs) yield useful information about the response to tasks, usually assessing attention. A brief review of the literature yielded eleven studies on EPs and seventeen on ERPs from 1978 to 2014. The EP studies covered short, mid, and long latency EPs, using both auditory and visual modalities. ERP studies reported the effects of meditation on tasks such as the auditory oddball paradigm, the attentional blink task, mismatched negativity, and affective picture viewing among others. Both EP and ERPs were recorded in several meditations detailed in the review. Maximum changes occurred in mid latency (auditory) EPs suggesting that maximum changes occur in the corresponding neural generators in the thalamus, thalamic radiations, and primary auditory cortical areas. ERP studies showed meditation can increase attention and enhance efficiency of brain resource allocation with greater emotional control. PMID:26137479

Neurophysiological Effects of Meditation Based on Evoked and Event Related Potential Recordings.

PubMed

Singh, Nilkamal; Telles, Shirley

2015-01-01

Evoked potentials (EPs) are a relatively noninvasive method to assess the integrity of sensory pathways. As the neural generators for most of the components are relatively well worked out, EPs have been used to understand the changes occurring during meditation. Event-related potentials (ERPs) yield useful information about the response to tasks, usually assessing attention. A brief review of the literature yielded eleven studies on EPs and seventeen on ERPs from 1978 to 2014. The EP studies covered short, mid, and long latency EPs, using both auditory and visual modalities. ERP studies reported the effects of meditation on tasks such as the auditory oddball paradigm, the attentional blink task, mismatched negativity, and affective picture viewing among others. Both EP and ERPs were recorded in several meditations detailed in the review. Maximum changes occurred in mid latency (auditory) EPs suggesting that maximum changes occur in the corresponding neural generators in the thalamus, thalamic radiations, and primary auditory cortical areas. ERP studies showed meditation can increase attention and enhance efficiency of brain resource allocation with greater emotional control.

[Visual perception of Kanji characters and complicated figures. Part 3. Visual P300 event-related potentials in patients with attention deficit/hyperactivity disorders].

PubMed

Shirane, Seiko; Inagaki, Masumi; Sata, Yoshimi; Kaga, Makiko

2004-07-01

In order to evaluate visual perception, the P300 event-related potentials (ERPs) for visual oddball tasks were recorded in 11 patients with attention deficit/hyperactivity disorders (AD/HD), 12 with mental retardation (MR) and 14 age-matched healthy controls. With the aim of revealing trial-to-trial variabilities which are neglected by investigating averaged ERPs, single sweep P300s (ss-P300s) were assessed in addition to averaged P300. There were no significant differences of averaged P300 latency and amplitude between controls and AD/HD patients. AD/HD patients showed an increased variability in the amplitude of ss-P300s, while MR patient showed an increased variability in latency. These findings suggest that in AD/HD patients general attention is impaired to a larger extent than selective attention and visual perception.

Asynchronous inputs alter excitability, spike timing, and topography in primary auditory cortex

PubMed Central

Pandya, Pritesh K.; Moucha, Raluca; Engineer, Navzer D.; Rathbun, Daniel L.; Vazquez, Jessica; Kilgard, Michael P.

2010-01-01

Correlation-based synaptic plasticity provides a potential cellular mechanism for learning and memory. Studies in the visual and somatosensory systems have shown that behavioral and surgical manipulation of sensory inputs leads to changes in cortical organization that are consistent with the operation of these learning rules. In this study, we examine how the organization of primary auditory cortex (A1) is altered by tones designed to decrease the average input correlation across the frequency map. After one month of separately pairing nucleus basalis stimulation with 2 and 14 kHz tones, a greater proportion of A1 neurons responded to frequencies below 2 kHz and above 14 kHz. Despite the expanded representation of these tones, cortical excitability was specifically reduced in the high and low frequency regions of A1, as evidenced by increased neural thresholds and decreased response strength. In contrast, in the frequency region between the two paired tones, driven rates were unaffected and spontaneous firing rate was increased. Neural response latencies were increased across the frequency map when nucleus basalis stimulation was associated with asynchronous activation of the high and low frequency regions of A1. This set of changes did not occur when pulsed noise bursts were paired with nucleus basalis stimulation. These results are consistent with earlier observations that sensory input statistics can shape cortical map organization and spike timing. PMID:15855025

Thermal latency adds to lesion depth after application of high-power short-duration radiofrequency energy: Results of a computer-modeling study.

PubMed

Irastorza, Ramiro M; d'Avila, Andre; Berjano, Enrique

2018-02-01

The use of ultra-short RF pulses could achieve greater lesion depth immediately after the application of the pulse due to thermal latency. A computer model of irrigated-catheter RF ablation was built to study the impact of thermal latency on the lesion depth. The results showed that the shorter the RF pulse duration (keeping energy constant), the greater the lesion depth during the cooling phase. For instance, after a 10-second pulse, lesion depth grew from 2.05 mm at the end of the pulse to 2.39 mm (17%), while after an ultra-short RF pulse of only 1 second the extra growth was 37% (from 2.22 to 3.05 mm). Importantly, short applications resulted in deeper lesions than long applications (3.05 mm vs. 2.39 mm, for 1- and 10-second pulse, respectively). While shortening the pulse duration produced deeper lesions, the associated increase in applied voltage caused overheating in the tissue: temperatures around 100 °C were reached at a depth of 1 mm in the case of 1- and 5-second pulses. However, since the lesion depth increased during the cooling period, lower values of applied voltage could be applied in short durations in order to obtain lesion depths similar to those in longer durations while avoiding overheating. The thermal latency phenomenon seems to be the cause of significantly greater lesion depth after short-duration high-power RF pulses. Balancing the applied total energy when the voltage and duration are changed is not the optimal strategy since short pulses can also cause overheating. © 2017 Wiley Periodicals, Inc.

Audio-visual speech perception: a developmental ERP investigation

PubMed Central

Knowland, Victoria CP; Mercure, Evelyne; Karmiloff-Smith, Annette; Dick, Fred; Thomas, Michael SC

2014-01-01

Being able to see a talking face confers a considerable advantage for speech perception in adulthood. However, behavioural data currently suggest that children fail to make full use of these available visual speech cues until age 8 or 9. This is particularly surprising given the potential utility of multiple informational cues during language learning. We therefore explored this at the neural level. The event-related potential (ERP) technique has been used to assess the mechanisms of audio-visual speech perception in adults, with visual cues reliably modulating auditory ERP responses to speech. Previous work has shown congruence-dependent shortening of auditory N1/P2 latency and congruence-independent attenuation of amplitude in the presence of auditory and visual speech signals, compared to auditory alone. The aim of this study was to chart the development of these well-established modulatory effects over mid-to-late childhood. Experiment 1 employed an adult sample to validate a child-friendly stimulus set and paradigm by replicating previously observed effects of N1/P2 amplitude and latency modulation by visual speech cues; it also revealed greater attenuation of component amplitude given incongruent audio-visual stimuli, pointing to a new interpretation of the amplitude modulation effect. Experiment 2 used the same paradigm to map cross-sectional developmental change in these ERP responses between 6 and 11 years of age. The effect of amplitude modulation by visual cues emerged over development, while the effect of latency modulation was stable over the child sample. These data suggest that auditory ERP modulation by visual speech represents separable underlying cognitive processes, some of which show earlier maturation than others over the course of development. PMID:24176002

Effects of Differential Reinforcement of Short Latencies on Response Latency, Task Completion, and Accuracy of an Adolescent with Autism

ERIC Educational Resources Information Center

Donohue, Melanie M.; Casey, Laura Baylot; Bicard, David F.; Bicard, Sara E.

2012-01-01

Children with Autism Spectrum Disorder (ASD) are faced with many challenging behaviors that could impede their learning. One commonly reported problem behavior is noncompliance, which is often defined as a delay in response (latency), decrease in rate of responding (fluency), or failure to complete a task. This failure to comply in an appropriate…

Predictors of photo naming: Dutch norms for 327 photos.

PubMed

Shao, Zeshu; Stiegert, Julia

2016-06-01

In the present study, we report naming latencies and norms for 327 photos of objects in Dutch. We provide norms for eight psycholinguistic variables: age of acquisition, familiarity, imageability, image agreement, objective and subjective visual complexity, word frequency, word length in syllables and letters, and name agreement. Furthermore, multiple regression analyses revealed that the significant predictors of photo-naming latencies were name agreement, word frequency, imageability, and image agreement. The naming latencies, norms, and stimuli are provided as supplemental materials.

Enhanced audio-visual interactions in the auditory cortex of elderly cochlear-implant users.

PubMed

Schierholz, Irina; Finke, Mareike; Schulte, Svenja; Hauthal, Nadine; Kantzke, Christoph; Rach, Stefan; Büchner, Andreas; Dengler, Reinhard; Sandmann, Pascale

2015-10-01

Auditory deprivation and the restoration of hearing via a cochlear implant (CI) can induce functional plasticity in auditory cortical areas. How these plastic changes affect the ability to integrate combined auditory (A) and visual (V) information is not yet well understood. In the present study, we used electroencephalography (EEG) to examine whether age, temporary deafness and altered sensory experience with a CI can affect audio-visual (AV) interactions in post-lingually deafened CI users. Young and elderly CI users and age-matched NH listeners performed a speeded response task on basic auditory, visual and audio-visual stimuli. Regarding the behavioral results, a redundant signals effect, that is, faster response times to cross-modal (AV) than to both of the two modality-specific stimuli (A, V), was revealed for all groups of participants. Moreover, in all four groups, we found evidence for audio-visual integration. Regarding event-related responses (ERPs), we observed a more pronounced visual modulation of the cortical auditory response at N1 latency (approximately 100 ms after stimulus onset) in the elderly CI users when compared with young CI users and elderly NH listeners. Thus, elderly CI users showed enhanced audio-visual binding which may be a consequence of compensatory strategies developed due to temporary deafness and/or degraded sensory input after implantation. These results indicate that the combination of aging, sensory deprivation and CI facilitates the coupling between the auditory and the visual modality. We suggest that this enhancement in multisensory interactions could be used to optimize auditory rehabilitation, especially in elderly CI users, by the application of strong audio-visually based rehabilitation strategies after implant switch-on. Copyright © 2015 Elsevier B.V. All rights reserved.

Adaptation in human visual cortex as a mechanism for rapid discrimination of aversive stimuli.

PubMed

Keil, Andreas; Stolarova, Margarita; Moratti, Stephan; Ray, William J

2007-06-01

The ability to react rapidly and efficiently to adverse stimuli is crucial for survival. Neuroscience and behavioral studies have converged to show that visual information associated with aversive content is processed quickly and accurately and is associated with rapid amplification of the neural responses. In particular, unpleasant visual information has repeatedly been shown to evoke increased cortical activity during early visual processing between 60 and 120 ms following the onset of a stimulus. However, the nature of these early responses is not well understood. Using neutral versus unpleasant colored pictures, the current report examines the time course of short-term changes in the human visual cortex when a subject is repeatedly exposed to simple grating stimuli in a classical conditioning paradigm. We analyzed changes in amplitude and synchrony of large-scale oscillatory activity across 2 days of testing, which included baseline measurements, 2 conditioning sessions, and a final extinction session. We found a gradual increase in amplitude and synchrony of very early cortical oscillations in the 20-35 Hz range across conditioning sessions, specifically for conditioned stimuli predicting aversive visual events. This increase for conditioned stimuli affected stimulus-locked cortical oscillations at a latency of around 60-90 ms and disappeared during extinction. Our findings suggest that reorganization of neural connectivity on the level of the visual cortex acts to optimize early perception of specific features indicative of emotional relevance.

Basic multisensory functions can be acquired after congenital visual pattern deprivation in humans.

PubMed

Putzar, Lisa; Gondan, Matthias; Röder, Brigitte

2012-01-01

People treated for bilateral congenital cataracts offer a model to study the influence of visual deprivation in early infancy on visual and multisensory development. We investigated cross-modal integration capabilities in cataract patients using a simple detection task that provided redundant information to two different senses. In both patients and controls, redundancy gains were consistent with coactivation models, indicating an integrated processing of modality-specific information. This finding is in contrast with recent studies showing impaired higher-level multisensory interactions in cataract patients. The present results suggest that basic cross-modal integrative processes for simple short stimuli do not depend on visual and/or crossmodal input since birth.

Evaluation of multifocal visual evoked potentials in patients with Graves' orbitopathy and subclinical optic nerve involvement.

PubMed

Pérez-Rico, Consuelo; Rodríguez-González, Natividad; Arévalo-Serrano, Juan; Blanco, Román

2012-08-01

Dysthyroid optic neuropathy is the most serious, although infrequent (8-10 %) complication in Graves' orbitopathy (GO). It is known that early stages of compressive optic neuropathy may produce reversible visual field defects, suggesting axoplasmic stasis rather than ganglion cell death. This observational, cross-sectional, case-control study assessed 34 consecutive patients (65 eyes) with Graves' hyperthyroidism and longstanding GO and 31 age-matched control subjects. The patients' multifocal visual evoked potentials (mfVEP) were compared to their clinical and psychophysical (standard automated perimetry [SAP]) and structural (optic coherence tomography [OCT]) diagnostic test data. Abnormal cluster defects were found in 12.3 % and 3.1 % of eyes on the interocular and monocular amplitude analysis mfVEP probability plots, respectively. As well, mfVEP latencies delays were found in 13.8 and 20 % of eyes on the interocular and monocular analysis probability plots, respectively. Interestingly, 19 % of patients with GO had ocular hypertension, and a strong correlation between intraocular pressure measured at upgaze and mfVEP latency was found. MfVEP amplitudes and visual acuity were significantly related to each other (P < 0.05), but not with the latencies delays. However, relationships between the interocular or monocular mfVEP amplitudes and latencies analysis and SAP indices or OCT data were not statistically significant. One-third of our patients with GO showed changes in the mfVEP, indicating significant subclinical optic nerve dysfunction. In this sense, the mfVEP may be a useful diagnostic tool in the clinic for early diagnosis and monitoring of optic nerve function abnormalities in patients with GO.

Hiding the Disk and Network Latency of Out-of-Core Visualization

NASA Technical Reports Server (NTRS)

Ellsworth, David

2001-01-01

This paper describes an algorithm that improves the performance of application-controlled demand paging for out-of-core visualization by hiding the latency of reading data from both local disks or disks on remote servers. The performance improvements come from better overlapping the computation with the page reading process, and by performing multiple page reads in parallel. The paper includes measurements that show that the new multithreaded paging algorithm decreases the time needed to compute visualizations by one third when using one processor and reading data from local disk. The time needed when using one processor and reading data from remote disk decreased by two thirds. Visualization runs using data from remote disk actually ran faster than ones using data from local disk because the remote runs were able to make use of the remote server's high performance disk array.

Visual and auditory cue integration for the generation of saccadic eye movements in monkeys and lever pressing in humans.

PubMed

Schiller, Peter H; Kwak, Michelle C; Slocum, Warren M

2012-08-01

This study examined how effectively visual and auditory cues can be integrated in the brain for the generation of motor responses. The latencies with which saccadic eye movements are produced in humans and monkeys form, under certain conditions, a bimodal distribution, the first mode of which has been termed express saccades. In humans, a much higher percentage of express saccades is generated when both visual and auditory cues are provided compared with the single presentation of these cues [H. C. Hughes et al. (1994) J. Exp. Psychol. Hum. Percept. Perform., 20, 131-153]. In this study, we addressed two questions: first, do monkeys also integrate visual and auditory cues for express saccade generation as do humans and second, does such integration take place in humans when, instead of eye movements, the task is to press levers with fingers? Our results show that (i) in monkeys, as in humans, the combined visual and auditory cues generate a much higher percentage of express saccades than do singly presented cues and (ii) the latencies with which levers are pressed by humans are shorter when both visual and auditory cues are provided compared with the presentation of single cues, but the distribution in all cases is unimodal; response latencies in the express range seen in the execution of saccadic eye movements are not obtained with lever pressing. © 2012 The Authors. European Journal of Neuroscience © 2012 Federation of European Neuroscience Societies and Blackwell Publishing Ltd.

The case from animal studies for balanced binocular treatment strategies for human amblyopia.

PubMed

Mitchell, Donald E; Duffy, Kevin R

2014-03-01

Although amblyopia typically manifests itself as a monocular condition, its origin has long been linked to unbalanced neural signals from the two eyes during early postnatal development, a view confirmed by studies conducted on animal models in the last 50 years. Despite recognition of its binocular origin, treatment of amblyopia continues to be dominated by a period of patching of the non-amblyopic eye that necessarily hinders binocular co-operation. This review summarizes evidence from three lines of investigation conducted on an animal model of deprivation amblyopia to support the thesis that treatment of amblyopia should instead focus upon procedures that promote and enhance binocular co-operation. First, experiments with mixed daily visual experience in which episodes of abnormal visual input were pitted against normal binocular exposure revealed that short exposures of the latter offset much longer periods of abnormal input to allow normal development of visual acuity in both eyes. Second, experiments on the use of part-time patching revealed that purposeful introduction of episodes of binocular vision each day could be very beneficial. Periods of binocular exposure that represented 30-50% of the daily visual exposure included with daily occlusion of the non-amblyopic could allow recovery of normal vision in the amblyopic eye. Third, very recent experiments demonstrate that a short 10 day period of total darkness can promote very fast and complete recovery of visual acuity in the amblyopic eye of kittens and may represent an example of a class of artificial environments that have similar beneficial effects. Finally, an approach is described to allow timing of events in kitten and human visual system development to be scaled to optimize the ages for therapeutic interventions. © 2014 The Authors Ophthalmic & Physiological Optics © 2014 The College of Optometrists.

Posterior Inferotemporal Cortex Cells Use Multiple Input Pathways for Shape Encoding.

PubMed

Ponce, Carlos R; Lomber, Stephen G; Livingstone, Margaret S

2017-05-10

In the macaque monkey brain, posterior inferior temporal (PIT) cortex cells contribute to visual object recognition. They receive concurrent inputs from visual areas V4, V3, and V2. We asked how these different anatomical pathways shape PIT response properties by deactivating them while monitoring PIT activity in two male macaques. We found that cooling of V4 or V2|3 did not lead to consistent changes in population excitatory drive; however, population pattern analyses showed that V4-based pathways were more important than V2|3-based pathways. We did not find any image features that predicted decoding accuracy differences between both interventions. Using the HMAX hierarchical model of visual recognition, we found that different groups of simulated "PIT" units with different input histories (lacking "V2|3" or "V4" input) allowed for comparable levels of object-decoding performance and that removing a large fraction of "PIT" activity resulted in similar drops in performance as in the cooling experiments. We conclude that distinct input pathways to PIT relay similar types of shape information, with V1-dependent V4 cells providing more quantitatively useful information for overall encoding than cells in V2 projecting directly to PIT. SIGNIFICANCE STATEMENT Convolutional neural networks are the best models of the visual system, but most emphasize input transformations across a serial hierarchy akin to the primary "ventral stream" (V1 → V2 → V4 → IT). However, the ventral stream also comprises parallel "bypass" pathways: V1 also connects to V4, and V2 to IT. To explore the advantages of mixing long and short pathways in the macaque brain, we used cortical cooling to silence inputs to posterior IT and compared the findings with an HMAX model with parallel pathways. Copyright © 2017 the authors 0270-6474/17/375019-16$15.00/0.

Posterior Inferotemporal Cortex Cells Use Multiple Input Pathways for Shape Encoding

PubMed Central

2017-01-01

In the macaque monkey brain, posterior inferior temporal (PIT) cortex cells contribute to visual object recognition. They receive concurrent inputs from visual areas V4, V3, and V2. We asked how these different anatomical pathways shape PIT response properties by deactivating them while monitoring PIT activity in two male macaques. We found that cooling of V4 or V2|3 did not lead to consistent changes in population excitatory drive; however, population pattern analyses showed that V4-based pathways were more important than V2|3-based pathways. We did not find any image features that predicted decoding accuracy differences between both interventions. Using the HMAX hierarchical model of visual recognition, we found that different groups of simulated “PIT” units with different input histories (lacking “V2|3” or “V4” input) allowed for comparable levels of object-decoding performance and that removing a large fraction of “PIT” activity resulted in similar drops in performance as in the cooling experiments. We conclude that distinct input pathways to PIT relay similar types of shape information, with V1-dependent V4 cells providing more quantitatively useful information for overall encoding than cells in V2 projecting directly to PIT. SIGNIFICANCE STATEMENT Convolutional neural networks are the best models of the visual system, but most emphasize input transformations across a serial hierarchy akin to the primary “ventral stream” (V1 → V2 → V4 → IT). However, the ventral stream also comprises parallel “bypass” pathways: V1 also connects to V4, and V2 to IT. To explore the advantages of mixing long and short pathways in the macaque brain, we used cortical cooling to silence inputs to posterior IT and compared the findings with an HMAX model with parallel pathways. PMID:28416597

The Relationship between Parameters of Long-Latency Evoked Potentials in a Multisensory Design.

PubMed

Hernández, Oscar H; García-Martínez, Rolando; Monteón, Victor

2016-10-01

In previous papers, we have shown that parameters of the omitted stimulus potential (OSP), which occurs at the end of a train of sensory stimuli, strongly depend on the modality. A train of stimuli also produces long-latency evoked potentials (LLEP) at the beginning of the train. This study is an extension of the OSP research, and it tested the relationship between parameters (ie, rate of rise, amplitude, and peak latency) of the P2 waves when trains of auditory, visual, or somatosensory stimuli were applied. The dynamics of the first 3 potentials in the train, related to habituation, were also studied. Twenty healthy young college volunteers participated in the study. As in the OSP, the P2 was faster and higher for auditory than for visual or somatosensory stimuli. The first P2 was swifter and higher than the second and the third potentials. The strength of habituation depends on the sensory modality and the parameter used. All these findings support the view that many long-latency brain potentials could share neural mechanisms related to wave generation. © EEG and Clinical Neuroscience Society (ECNS) 2015.

Role of multisensory stimuli in vigilance enhancement- a single trial event related potential study.

PubMed

Abbasi, Nida Itrat; Bodala, Indu Prasad; Bezerianos, Anastasios; Yu Sun; Al-Nashash, Hasan; Thakor, Nitish V

2017-07-01

Development of interventions to prevent vigilance decrement has important applications in sensitive areas like transportation and defence. The objective of this work is to use multisensory (visual and haptic) stimuli for cognitive enhancement during mundane tasks. Two different epoch intervals representing sensory perception and motor response were analysed using minimum variance distortionless response (MVDR) based single trial ERP estimation to understand the performance dependency on both factors. Bereitschaftspotential (BP) latency L3 (r=0.6 in phase 1 (visual) and r=0.71 in phase 2 (visual and haptic)) was significantly correlated with reaction time as compared to that of sensory ERP latency L2 (r=0.1 in both phase 1 and phase 2). This implies that low performance in monotonous tasks is predominantly dependent on the prolonged neural interaction with the muscles to initiate movement. Further, negative relationship was found between the ERP latencies related to sensory perception and Bereitschaftspotential (BP) and occurrence of epochs when multisensory cues are provided. This means that vigilance decrement is reduced with the help of multisensory stimulus presentation in prolonged monotonous tasks.

Vividness of visual imagery and incidental recall of verbal cues, when phenomenological availability reflects long-term memory accessibility.

PubMed

D'Angiulli, Amedeo; Runge, Matthew; Faulkner, Andrew; Zakizadeh, Jila; Chan, Aldrich; Morcos, Selvana

2013-01-01

The relationship between vivid visual mental images and unexpected recall (incidental recall) was replicated, refined, and extended. In Experiment 1, participants were asked to generate mental images from imagery-evoking verbal cues (controlled on several verbal properties) and then, on a trial-by-trial basis, rate the vividness of their images; 30 min later, participants were surprised with a task requiring free recall of the cues. Higher vividness ratings predicted better incidental recall of the cues than individual differences (whose effect was modest). Distributional analysis of image latencies through ex-Gaussian modeling showed an inverse relation between vividness and latency. However, recall was unrelated to image latency. The follow-up Experiment 2 showed that the processes underlying trial-by-trial vividness ratings are unrelated to the Vividness of Visual Imagery Questionnaire (VVIQ), as further supported by a meta-analysis of a randomly selected sample of relevant literature. The present findings suggest that vividness may act as an index of availability of long-term sensory traces, playing a non-epiphenomenal role in facilitating the access of those memories.

Vividness of Visual Imagery and Incidental Recall of Verbal Cues, When Phenomenological Availability Reflects Long-Term Memory Accessibility

PubMed Central

D’Angiulli, Amedeo; Runge, Matthew; Faulkner, Andrew; Zakizadeh, Jila; Chan, Aldrich; Morcos, Selvana

2013-01-01

The relationship between vivid visual mental images and unexpected recall (incidental recall) was replicated, refined, and extended. In Experiment 1, participants were asked to generate mental images from imagery-evoking verbal cues (controlled on several verbal properties) and then, on a trial-by-trial basis, rate the vividness of their images; 30 min later, participants were surprised with a task requiring free recall of the cues. Higher vividness ratings predicted better incidental recall of the cues than individual differences (whose effect was modest). Distributional analysis of image latencies through ex-Gaussian modeling showed an inverse relation between vividness and latency. However, recall was unrelated to image latency. The follow-up Experiment 2 showed that the processes underlying trial-by-trial vividness ratings are unrelated to the Vividness of Visual Imagery Questionnaire (VVIQ), as further supported by a meta-analysis of a randomly selected sample of relevant literature. The present findings suggest that vividness may act as an index of availability of long-term sensory traces, playing a non-epiphenomenal role in facilitating the access of those memories. PMID:23382719

Vection: the contributions of absolute and relative visual motion.

PubMed

Howard, I P; Howard, A

1994-01-01

Inspection of a visual scene rotating about the vertical body axis induces a compelling sense of self rotation, or circular vection. Circular vection is suppressed by stationary objects seen beyond the moving display but not by stationary objects in the foreground. We hypothesised that stationary objects in the foreground facilitate vection because they introduce a relative-motion signal into what would otherwise be an absolute-motion signal. Vection latency and magnitude were measured with a full-field moving display and with stationary objects of various sizes and at various positions in the visual field. The results confirmed the hypothesis. Vection latency was longer when there were no stationary objects in view than when stationary objects were in view. The effect of stationary objects was particularly evident at low stimulus velocities. At low velocities a small stationary point significantly increased vection magnitude in spite of the fact that, at higher stimulus velocities and with other stationary objects in view, fixation on a stationary point, if anything, reduced vection. Changing the position of the stationary objects in the field of view did not affect vection latencies or magnitudes.

Perceptual latency priming by masked and unmasked stimuli: evidence for an attentional interpretation.

PubMed

Scharlau, Ingrid; Neumann, Odmar

2003-08-01

Four experiments investigated the influence of a metacontrast-masked prime on temporal order judgments. The main results were (1) that a masked prime reduced the latency of the mask's conscious perception (perceptual latency priming), (2) that this effect was independent of whether the prime suffered strong or weak masking, (3) that it was unaffected by the degree of visual similarity between the prime and the mask, and that (4) there was no difference between congruent and incongruent primes. Finding (1) suggests that location cueing affects not only response times but also the latency of conscious perception. (2) The finding that priming was unaffected by the prime's detectability argues against a response bias interpretation of this effect. (3) Since visual similarity had no effect on the prime's efficiency, it is unlikely that sensory priming was involved. (4) The lack of a divergence between the effects of congruent and incongruent primes implies a functional difference between the judgments in the temporal order judgment task and speeded responses that have demonstrated differential effects of congruent and incongruent primes (e.g., Klotz & Neumann, 1999). These results can best be interpreted by assuming that the prime affects perceptual latency by initiating a shift of attention, as suggested by the Asynchronous Updating Model (AUM; Neumann 1978, 1982).

High visual resolution matters in audiovisual speech perception, but only for some.

PubMed

Alsius, Agnès; Wayne, Rachel V; Paré, Martin; Munhall, Kevin G

2016-07-01

The basis for individual differences in the degree to which visual speech input enhances comprehension of acoustically degraded speech is largely unknown. Previous research indicates that fine facial detail is not critical for visual enhancement when auditory information is available; however, these studies did not examine individual differences in ability to make use of fine facial detail in relation to audiovisual speech perception ability. Here, we compare participants based on their ability to benefit from visual speech information in the presence of an auditory signal degraded with noise, modulating the resolution of the visual signal through low-pass spatial frequency filtering and monitoring gaze behavior. Participants who benefited most from the addition of visual information (high visual gain) were more adversely affected by the removal of high spatial frequency information, compared to participants with low visual gain, for materials with both poor and rich contextual cues (i.e., words and sentences, respectively). Differences as a function of gaze behavior between participants with the highest and lowest visual gains were observed only for words, with participants with the highest visual gain fixating longer on the mouth region. Our results indicate that the individual variance in audiovisual speech in noise performance can be accounted for, in part, by better use of fine facial detail information extracted from the visual signal and increased fixation on mouth regions for short stimuli. Thus, for some, audiovisual speech perception may suffer when the visual input (in addition to the auditory signal) is less than perfect.

Input-dependent frequency modulation of cortical gamma oscillations shapes spatial synchronization and enables phase coding.

PubMed

Lowet, Eric; Roberts, Mark; Hadjipapas, Avgis; Peter, Alina; van der Eerden, Jan; De Weerd, Peter

2015-02-01

Fine-scale temporal organization of cortical activity in the gamma range (∼25-80Hz) may play a significant role in information processing, for example by neural grouping ('binding') and phase coding. Recent experimental studies have shown that the precise frequency of gamma oscillations varies with input drive (e.g. visual contrast) and that it can differ among nearby cortical locations. This has challenged theories assuming widespread gamma synchronization at a fixed common frequency. In the present study, we investigated which principles govern gamma synchronization in the presence of input-dependent frequency modulations and whether they are detrimental for meaningful input-dependent gamma-mediated temporal organization. To this aim, we constructed a biophysically realistic excitatory-inhibitory network able to express different oscillation frequencies at nearby spatial locations. Similarly to cortical networks, the model was topographically organized with spatially local connectivity and spatially-varying input drive. We analyzed gamma synchronization with respect to phase-locking, phase-relations and frequency differences, and quantified the stimulus-related information represented by gamma phase and frequency. By stepwise simplification of our models, we found that the gamma-mediated temporal organization could be reduced to basic synchronization principles of weakly coupled oscillators, where input drive determines the intrinsic (natural) frequency of oscillators. The gamma phase-locking, the precise phase relation and the emergent (measurable) frequencies were determined by two principal factors: the detuning (intrinsic frequency difference, i.e. local input difference) and the coupling strength. In addition to frequency coding, gamma phase contained complementary stimulus information. Crucially, the phase code reflected input differences, but not the absolute input level. This property of relative input-to-phase conversion, contrasting with latency codes or slower oscillation phase codes, may resolve conflicting experimental observations on gamma phase coding. Our modeling results offer clear testable experimental predictions. We conclude that input-dependency of gamma frequencies could be essential rather than detrimental for meaningful gamma-mediated temporal organization of cortical activity.

Input-Dependent Frequency Modulation of Cortical Gamma Oscillations Shapes Spatial Synchronization and Enables Phase Coding

PubMed Central

Lowet, Eric; Roberts, Mark; Hadjipapas, Avgis; Peter, Alina; van der Eerden, Jan; De Weerd, Peter

2015-01-01

Fine-scale temporal organization of cortical activity in the gamma range (∼25–80Hz) may play a significant role in information processing, for example by neural grouping (‘binding’) and phase coding. Recent experimental studies have shown that the precise frequency of gamma oscillations varies with input drive (e.g. visual contrast) and that it can differ among nearby cortical locations. This has challenged theories assuming widespread gamma synchronization at a fixed common frequency. In the present study, we investigated which principles govern gamma synchronization in the presence of input-dependent frequency modulations and whether they are detrimental for meaningful input-dependent gamma-mediated temporal organization. To this aim, we constructed a biophysically realistic excitatory-inhibitory network able to express different oscillation frequencies at nearby spatial locations. Similarly to cortical networks, the model was topographically organized with spatially local connectivity and spatially-varying input drive. We analyzed gamma synchronization with respect to phase-locking, phase-relations and frequency differences, and quantified the stimulus-related information represented by gamma phase and frequency. By stepwise simplification of our models, we found that the gamma-mediated temporal organization could be reduced to basic synchronization principles of weakly coupled oscillators, where input drive determines the intrinsic (natural) frequency of oscillators. The gamma phase-locking, the precise phase relation and the emergent (measurable) frequencies were determined by two principal factors: the detuning (intrinsic frequency difference, i.e. local input difference) and the coupling strength. In addition to frequency coding, gamma phase contained complementary stimulus information. Crucially, the phase code reflected input differences, but not the absolute input level. This property of relative input-to-phase conversion, contrasting with latency codes or slower oscillation phase codes, may resolve conflicting experimental observations on gamma phase coding. Our modeling results offer clear testable experimental predictions. We conclude that input-dependency of gamma frequencies could be essential rather than detrimental for meaningful gamma-mediated temporal organization of cortical activity. PMID:25679780

Difference in Perseverative Errors during a Visual Attention Task with Auditory Distractors in Alpha-9 Nicotinic Receptor Subunit Wild Type and Knock-Out Mice.

PubMed

Jorratt, Pascal; Delano, Paul H; Delgado, Carolina; Dagnino-Subiabre, Alexies; Terreros, Gonzalo

2017-01-01

The auditory efferent system is a neural network that originates in the auditory cortex and projects to the cochlear receptor through olivocochlear (OC) neurons. Medial OC neurons make cholinergic synapses with outer hair cells (OHCs) through nicotinic receptors constituted by α9 and α10 subunits. One of the physiological functions of the α9 nicotinic receptor subunit (α9-nAChR) is the suppression of auditory distractors during selective attention to visual stimuli. In a recent study we demonstrated that the behavioral performance of alpha-9 nicotinic receptor knock-out (KO) mice is altered during selective attention to visual stimuli with auditory distractors since they made less correct responses and more omissions than wild type (WT) mice. As the inhibition of the behavioral responses to irrelevant stimuli is an important mechanism of the selective attention processes, behavioral errors are relevant measures that can reflect altered inhibitory control. Errors produced during a cued attention task can be classified as premature, target and perseverative errors. Perseverative responses can be considered as an inability to inhibit the repetition of an action already planned, while premature responses can be considered as an index of the ability to wait or retain an action. Here, we studied premature, target and perseverative errors during a visual attention task with auditory distractors in WT and KO mice. We found that α9-KO mice make fewer perseverative errors with longer latencies than WT mice in the presence of auditory distractors. In addition, although we found no significant difference in the number of target error between genotypes, KO mice made more short-latency target errors than WT mice during the presentation of auditory distractors. The fewer perseverative error made by α9-KO mice could be explained by a reduced motivation for reward and an increased impulsivity during decision making with auditory distraction in KO mice.

Multimodal communication, mismatched messages and the effects of turbidity on the antipredator behavior of the Barton Springs salamander, Eurycea sosorum.

PubMed

Zabierek, Kristina C; Gabor, Caitlin R

2016-09-01

Prey may use multiple sensory channels to detect predators, whose cues may differ in altered sensory environments, such as turbid conditions. Depending on the environment, prey may use cues in an additive/complementary manner or in a compensatory manner. First, to determine whether the purely aquatic Barton Springs salamander, Eurycea sosorum, show an antipredator response to visual cues, we examined their activity when exposed to either visual cues of a predatory fish (Lepomis cyanellus) or a non-predatory fish (Etheostoma lepidum). Salamanders decreased activity in response to predator visual cues only. Then, we examined the antipredator response of these salamanders to all matched and mismatched combinations of chemical and visual cues of the same predatory and non-predatory fish in clear and low turbidity conditions. Salamanders decreased activity in response to predator chemical cues matched with predator visual cues or mismatched with non-predator visual cues. Salamanders also increased latency to first move to predator chemical cues mismatched with non-predator visual cues. Salamanders decreased activity and increased latency to first move more in clear as opposed to turbid conditions in all treatment combinations. Our results indicate that salamanders under all conditions and treatments preferentially rely on chemical cues to determine antipredator behavior, although visual cues are potentially utilized in conjunction for latency to first move. Our results also have potential conservation implications, as decreased antipredator behavior was seen in turbid conditions. These results reveal complexity of antipredator behavior in response to multiple cues under different environmental conditions, which is especially important when considering endangered species. Copyright © 2016 Elsevier B.V. All rights reserved.

The amblyopic eye in subjects with anisometropia show increased saccadic latency in the delayed saccade task

PubMed Central

Perdziak, Maciej; Witkowska, Dagmara; Gryncewicz, Wojciech; Przekoracka-Krawczyk, Anna; Ober, Jan

2014-01-01

The term amblyopia is used to describe reduced visual function in one eye (or both eyes, though not so often) which cannot be fully improved by refractive correction and explained by the organic cause observed during regular eye examination. Amblyopia is associated with abnormal visual experience (e.g., anisometropia) during infancy or early childhood. Several studies have shown prolongation of saccadic latency time in amblyopic eye. In our opinion, study of saccadic latency in the context of central vision deficits assessment, should be based on central retina stimulation. For this reason, we proposed saccade delayed task. It requires inhibitory processing for maintaining fixation on the central target until it disappears—what constitutes the GO signal for saccade. The experiment consisted of 100 trials for each eye and was performed under two viewing conditions: monocular amblyopic/non-dominant eye and monocular dominant eye. We examined saccadic latency in 16 subjects (mean age 30 ± 11 years) with anisometropic amblyopia (two subjects had also microtropia) and in 17 control subjects (mean age 28 ± 8 years). Participants were instructed to look at central (fixation) target and when it disappears, to make the saccade toward the periphery (10°) as fast as possible, either left or the right target. The study results have proved the significant difference in saccadic latency between the amblyopic (mean 262 ± 48 ms) and dominant (mean 237 ± 45 ms) eye, in anisometropic group. In the control group, the saccadic latency for dominant (mean 226 ± 32 ms) and non-dominant (mean 230 ± 29 ms) eye was not significantly different. By the use of LATER (Linear Approach to the Threshold with Ergodic Rate) decision model we interpret our findings as a decrease in accumulation of visual information acquired by means of central retina in subjects with anisometropic amblyopia. PMID:25352790

Claustral single cell reactions to tooth pulp stimulation in cats.

PubMed

Jastreboff, P; Sikora, M; Frydrychowski, A; Słoniewski, P

1983-01-01

Single unit activity in the central region of the claustrum, evoked by electrical stimulation of tooth pulp or paws was studied on cats under chloralose anesthesia. The majority of cells responded in similar manner to stimulation of tooth pulp or paws, but there were cells with clear preference to a given type of stimulation. Latencies of reactions evoked by tooth pulp stimulation were significantly shorter than those for limb stimulation. In the former case latencies as short as 8 rns were observed. It is postulated that the central region of the claustrum receives a projection from the tooth pulp, and that in those cases with very short latency the projection is direct and does not involve the cerebral cortex.

Remote distractor effects and saccadic inhibition: spatial and temporal modulation.

PubMed

Walker, Robin; Benson, Valerie

2013-09-12

The onset of a visual distractor remote from a saccade target is known to increase saccade latency (the remote distractor effect [RDE]). In addition, distractors may also selectively inhibit saccades that would be initiated about 90 ms after distractor onset (termed saccadic inhibition [SI]). Recently, it has been proposed that the transitory inhibition of saccades (SI) may underlie the increase in mean latency (RDE). In a first experiment, the distractor eccentricity was manipulated, and a robust RDE that was strongly modulated by distractor eccentricity was observed. However, the underlying latency distributions did not reveal clear evidence of SI. A second experiment manipulated distractor spatial location and the timing of the distractor onset in relation to the target. An RDE was again observed with remote distractors away from the target axis and under conditions with early-onset distractors that would be unlikely to produce SI, whereas later distractor onsets produced an RDE along with some evidence of an SI effect. A third experiment using a mixed block of target-distractor stimulus-onset asynchronies (SOAs) revealed an RDE that varied with both distractor eccentricity and SOA and changes to latency distributions consistent with the timing of SI. We argue that the notion that SI underpins the RDE is similar to the earlier argument that express saccades underlie the fixation offset (gap) effect and that changes in mean latency and to the shape of the underlying latency distributions following a visual onset may involve more than one inhibitory process.

Development of face recognition: Dynamic causal modelling of MEG data.

PubMed

He, Wei; Johnson, Blake W

2018-04-01

Electrophysiological studies of adults indicate that brain activity is enhanced during viewing of repeated faces, at a latency of about 250 ms after the onset of the face (M250/N250). The present study aimed to determine if this effect was also present in preschool-aged children, whose brain activity was measured in a custom-sized pediatric MEG system. The results showed that, unlike adults, face repetition did not show any significant modulation of M250 amplitude in children; however children's M250 latencies were significantly faster for repeated than non-repeated faces. Dynamic causal modelling (DCM) of the M250 in both age groups tested the effects of face repetition within the core face network including the occipital face area (OFA), the fusiform face area (FFA), and the superior temporal sulcus (STS). DCM revealed that repetition of identical faces altered both forward and backward connections in children and adults; however the modulations involved inputs to both FFA and OFA in adults but only to OFA in children. These findings suggest that the amplitude-insensitivity of the immature M250 may be due to a weaker connection between the FFA and lower visual areas. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Serotonin transporter polymorphism modifies the association between depressive symptoms and sleep onset latency complaint in elderly people: results from the 'InveCe.Ab' study.

PubMed

Polito, Letizia; Davin, Annalisa; Vaccaro, Roberta; Abbondanza, Simona; Govoni, Stefano; Racchi, Marco; Guaita, Antonio

2015-04-01

Previous studies have documented the involvement of the central nervous system serotonin in promoting wakefulness. There are few and conflicting results over whether there is an actual association between bearing the short allele of serotonin transporter promoter polymorphism (5-HTTLPR) and worse sleep quality. This study examined whether sleep onset latency complaint is associated with the 5-HTTLPR triallelic polymorphism in the SLC6A4 gene promoter and whether this polymorphism influences the relationship between sleep onset latency complaint and depressive symptoms in elderly people. A total of 1321 community-dwelling individuals aged 70-74 years were interviewed for sleep onset latency complaint and for sleep medication consumption. Participants' genomic DNA was typed for 5-HTTLPR and rs25531 polymorphisms. Depressive symptoms were evaluated with the Geriatric Depression Scale Short form and general medical comorbidity was assessed by the Cumulative Illness Rating Scale. The presence of a past history of depression was recorded. The S' allele of the 5-HTTLPR triallelic polymorphism was associated with sleep onset latency complaint. This association was maintained after adjusting for depressive symptoms, sex, age, history of depression and medical comorbidity. After stratification for 5-HTTLPR/rs25531, only in S'S' individuals high depressive symptoms were actually associated with sleep onset latency complaint. These data indicate that the low-expressing 5-HTTLPR triallelic polymorphism is an independent risk factor for sleep onset latency disturbance. Furthermore, the 5-HTTLPR genotype influences the association between depressive symptoms and sleep onset latency complaint. © 2014 European Sleep Research Society.

Throughput, latency and cost comparisons of microcontroller-based implementations of wireless sensor network (WSN) in high jump sports

NASA Astrophysics Data System (ADS)

Ahmad, Afandi; Roslan, Muhammad Faris; Amira, Abbes

2017-09-01

In high jump sports, approach take-off speed and force during the take-off are two (2) main important parts to gain maximum jump. To measure both parameters, wireless sensor network (WSN) that contains microcontroller and sensor are needed to describe the results of speed and force for jumpers. Most of the microcontroller exhibit transmission issues in terms of throughput, latency and cost. Thus, this study presents the comparison of wireless microcontrollers in terms of throughput, latency and cost, and the microcontroller that have best performances and cost will be implemented in high jump wearable device. In the experiments, three (3) parts have been integrated - input, process and output. Force (for ankle) and global positioning system (GPS) sensor (for body waist) acts as an input for data transmission. These data were then being processed by both microcontrollers, ESP8266 and Arduino Yun Mini to transmit the data from sensors to the server (host-PC) via message queuing telemetry transport (MQTT) protocol. The server acts as receiver and the results was calculated from the MQTT log files. At the end, results obtained have shown ESP8266 microcontroller had been chosen since it achieved high throughput, low latency and 11 times cheaper in term of prices compared to Arduino Yun Mini microcontroller.

Serial dependence promotes object stability during occlusion

PubMed Central

Liberman, Alina; Zhang, Kathy; Whitney, David

2016-01-01

Object identities somehow appear stable and continuous over time despite eye movements, disruptions in visibility, and constantly changing visual input. Recent results have demonstrated that the perception of orientation, numerosity, and facial identity is systematically biased (i.e., pulled) toward visual input from the recent past. The spatial region over which current orientations or face identities are pulled by previous orientations or identities, respectively, is known as the continuity field, which is temporally tuned over the past several seconds (Fischer & Whitney, 2014). This perceptual pull could contribute to the visual stability of objects over short time periods, but does it also address how perceptual stability occurs during visual discontinuities? Here, we tested whether the continuity field helps maintain perceived object identity during occlusion. Specifically, we found that the perception of an oriented Gabor that emerged from behind an occluder was significantly pulled toward the random (and unrelated) orientation of the Gabor that was seen entering the occluder. Importantly, this serial dependence was stronger for predictable, continuously moving trajectories, compared to unpredictable ones or static displacements. This result suggests that our visual system takes advantage of expectations about a stable world, helping to maintain perceived object continuity despite interrupted visibility. PMID:28006066

First-pass selectivity for semantic categories in human anteroventral temporal lobe

PubMed Central

Chan, Alexander M.; Baker, Janet M.; Eskandar, Emad; Schomer, Donald; Ulbert, Istvan; Marinkovic, Ksenija; Cash, Sydney S.; Halgren, Eric

2012-01-01

How the brain encodes the semantic concepts represented by words is a fundamental question in cognitive neuroscience. Hemodynamic neuroimaging studies have robustly shown that different areas of posteroventral temporal lobe are selectively activated by images of animals versus manmade objects. Selective responses in these areas to words representing animals versus objects are sometimes also seen, but they are task-dependent, suggesting that posteroventral temporal cortex may encode visual categories, while more anterior areas encode semantic categories. Here, using the spatiotemporal resolution provided by intracranial macroelectrode and microelectrode arrays, we report category-selective responses to words representing animals and objects in human anteroventral temporal areas including inferotemporal, perirhinal and entorhinal cortices. This selectivity generalizes across tasks and sensory modalities, suggesting that it represents abstract lexico-semantic categories. Significant category-specific responses are found in measures sensitive to synaptic activity (local field potentials, high gamma power, current sources and sinks) and unit-firing (multi- and single-unit activity). Category-selective responses can occur at short latency, as early as 130ms, in middle cortical layers and thus are extracted in the first-pass of activity through the anteroventral temporal lobe. This activation may provide input to posterior areas for iconic representations when required by the task, as well as to the hippocampal formation for categorical encoding and retrieval of memories, and to the amygdala for emotional associations. More generally, these results support models in which the anteroventral temporal lobe plays a primary role in the semantic representation of words. PMID:22159123

Simultaneous recording of multifocal VEP responses to short-wavelength and achromatic stimuli

PubMed Central

Wang, Min; Hood, Donald C.

2010-01-01

A paradigm is introduced that allows for simultaneous recording of the pattern-onset multifocal visual evoked potentials (mfVEP) to both short-wavelength (SW) and achromatic (A) stimuli. There were 5 sets of stimulus conditions, each of which is defined by two semi-concurrently presented stimuli, A64/SW (a 64% contrast achromatic stimulus and a short-wavelength stimulus), A64/A8 (64% achromatic/8% achromatic), A0/A8 (0% (gray) achromatic/8% achromatic), A64/A0 and A0/SW. When paired with A64 as part of A64/SW, the SW stimulus yielded mfVEP responses (SWmfVEP) with diminished amplitude in the fovea, consistent with the known sensitivity of the S-cone system. In addition, when A8, which is approximately equal to the L and M cone contribution of the SW stimulus, was recorded alone, the response to A8 was small, but significantly larger than noise. However, when A8 was paired with A64, the response to A8 was reduced to close to noise level, suggesting that the LM cone contribution of the SWmfVEP can be suppressed by A64. When A64 was recorded alone, the response to A64 was about 32% larger than the mfVEP for A64 when paired with the SW. Likewise, the presence of A64 stimulus also reduces the response of SWmfVEP by 35%. Finally, an intense narrow-band yellow background prolonged the latency of SW response for the A0/SW stimulus but not the latency of SW response for the A64/SW stimulus. These results indicate that it is possible to simultaneously record an SWmfVEP with little LM cone contribution along with an achromatic mfVEP. PMID:20499134

A Short Is Worth a Thousand Films!

ERIC Educational Resources Information Center

Massi, Maria Palmira; Blázquez, Bettiana Andrea

2012-01-01

The importance of visual input in the contemporary ELT classroom is such that it is commonplace to use audiovisual elements provided by pictures, films, clips and the like. The power of images is unquestionable, and as the old saying goes, an image is worth a thousand words. Following this line of reasoning, the objective of this article is to…

Down Syndrome and Short-Term Memory Impairment: A Storage or Retrieval Deficit?

ERIC Educational Resources Information Center

Adler, Sol; McDade, Hiram L.

1980-01-01

Three groups of eight Ss (Down's syndrome, CA control, and MA control) received a battery of tests to assess recall and recognition memory using either auditory or visual input with verbal and nonverbal responses. Results indicated that the Down's syndrome group possessed deficits in both storage and retrieval abilities, with storage of visually…

Nutritional correlates and mate acquisition role of multiple sexual traits in male collared flycatchers

NASA Astrophysics Data System (ADS)

Hegyi, Gergely; Szöllősi, Eszter; Jenni-Eiermann, Susanne; Török, János; Eens, Marcel; Garamszegi, László Zsolt

2010-06-01

The information content of a sexual signal may predict its importance in a multiple signal system. Many studies have correlated sexual signal expression with the absolute levels of nutrient reserves. In contrast, the changes of nutrient reserves associated with signal expression are largely unknown in the wild due to technical limitations although they are important determinants of signal information content. We compared two visual and eight acoustic sexual traits in male collared flycatchers to see whether the nutritional correlates of expression predict the role of the signal in sexual selection. We used single point assays of plasma lipid metabolites to estimate short-term changes in nutritional state in relation to sexual trait expression during courtship. As a measure of sexual selection, we estimated the relationship with pairing latency after arrival in a 4-year dataset. Males which found a mate rapidly were characterized by large wing and forehead patches, but small song strophe complexity and small figure repertoire size. Traits more strongly related to pairing latency were also more closely related to changes in nutrient reserves. This indicates a link between signal role and information content. Small wing patches and, surprisingly, complex songs seemed to indicate poor phenotypic quality and were apparently disfavoured at mate acquisition in our population. Future studies of the information content of sexual traits, especially dynamic traits such as song, may benefit from the use of plasma metabolite profiles as non-invasive indicators of short-term changes in body condition.

Receptive Field Vectors of Genetically-Identified Retinal Ganglion Cells Reveal Cell-Type-Dependent Visual Functions

PubMed Central

Katz, Matthew L.; Viney, Tim J.; Nikolic, Konstantin

2016-01-01

Sensory stimuli are encoded by diverse kinds of neurons but the identities of the recorded neurons that are studied are often unknown. We explored in detail the firing patterns of eight previously defined genetically-identified retinal ganglion cell (RGC) types from a single transgenic mouse line. We first introduce a new technique of deriving receptive field vectors (RFVs) which utilises a modified form of mutual information (“Quadratic Mutual Information”). We analysed the firing patterns of RGCs during presentation of short duration (~10 second) complex visual scenes (natural movies). We probed the high dimensional space formed by the visual input for a much smaller dimensional subspace of RFVs that give the most information about the response of each cell. The new technique is very efficient and fast and the derivation of novel types of RFVs formed by the natural scene visual input was possible even with limited numbers of spikes per cell. This approach enabled us to estimate the 'visual memory' of each cell type and the corresponding receptive field area by calculating Mutual Information as a function of the number of frames and radius. Finally, we made predictions of biologically relevant functions based on the RFVs of each cell type. RGC class analysis was complemented with results for the cells’ response to simple visual input in the form of black and white spot stimulation, and their classification on several key physiological metrics. Thus RFVs lead to predictions of biological roles based on limited data and facilitate analysis of sensory-evoked spiking data from defined cell types. PMID:26845435

Color vision in attention-deficit/hyperactivity disorder: a pilot visual evoked potential study.

PubMed

Kim, Soyeon; Banaschewski, Tobias; Tannock, Rosemary

2015-01-01

Individuals with attention-deficit/hyperactivity disorder (ADHD) are reported to manifest visual problems (including ophthalmological and color perception, particularly for blue-yellow stimuli), but findings are inconsistent. Accordingly, this study investigated visual function and color perception in adolescents with ADHD using color Visual Evoked Potentials (cVEP), which provides an objective measure of color perception. Thirty-one adolescents (aged 13-18), 16 with a confirmed diagnosis of ADHD, and 15 healthy peers, matched for age, gender, and IQ participated in the study. All underwent an ophthalmological exam, as well as electrophysiological testing color Visual Evoked Potentials (cVEP), which measured the latency and amplitude of the neural P1 response to chromatic (blue-yellow, red-green) and achromatic stimuli. No intergroup differences were found in the ophthalmological exam. However, significantly larger P1 amplitude was found for blue and yellow stimuli, but not red/green or achromatic stimuli, in the ADHD group (particularly in the medicated group) compared to controls. Larger amplitude in the P1 component for blue-yellow in the ADHD group compared to controls may account for the lack of difference in color perception tasks. We speculate that the larger amplitude for blue-yellow stimuli in early sensory processing (P1) might reflect a compensatory strategy for underlying problems including compromised retinal input of s-cones due to hypo-dopaminergic tone. Copyright © 2014 Spanish General Council of Optometry. Published by Elsevier Espana. All rights reserved.

Lateral geniculate body evoked potentials elicited by visual and electrical stimulation.

PubMed

Choi, Chang Wook; Kim, Pan Sang; Shin, Sun Ae; Yang, Ji Yeon; Yang, Yun Sik

2014-08-01

Blind individuals who have photoreceptor loss are known to perceive phosphenes with electrical stimulation of their remaining retinal ganglion cells. We proposed that implantable lateral geniculate body (LGB) stimulus electrode arrays could be used to generate phosphene vision. We attempted to refine the basic reference of the electrical evoked potentials (EEPs) elicited by microelectrical stimulations of the optic nerve, optic tract and LGB of a domestic pig, and then compared it to visual evoked potentials (VEPs) elicited by short-flash stimuli. For visual function measurement, VEPs in response to short-flash stimuli on the left eye of the domestic pig were assessed over the visual cortex at position Oz with the reference electrode at Fz. After anesthesia, linearly configured platinum wire electrodes were inserted into the optic nerve, optic track and LGB. To determine the optimal stimulus current, EEPs were recorded repeatedly with controlling the pulse and power. The threshold of current and charge density to elicit EEPs at 0.3 ms pulse duration was about ±10 µA. Our experimental results showed that visual cortex activity can be effectively evoked by stimulation of the optic nerve, optic tract and LGB using penetrating electrodes. The latency of P1 was more shortened as the electrical stimulation was closer to LGB. The EEPs of two-channel in the visual cortex demonstrated a similar pattern with stimulation of different spots of the stimulating electrodes. We found that the LGB-stimulated EEP pattern was very similar to the simultaneously generated VEP on the control side, although implicit time deferred. EEPs and VEPs derived from visual-system stimulation were compared. The LGB-stimulated EEP wave demonstrated a similar pattern to the VEP waveform except implicit time, indicating prosthetic-based electrical stimulation of the LGB could be utilized for the blind to perceive vision of phosphenes.

Whole-body vibration induces distinct reflex patterns in human soleus muscle.

PubMed

Karacan, Ilhan; Cidem, Muharrem; Cidem, Mehmet; Türker, Kemal S

2017-06-01

The neuronal mechanisms underlying whole body vibration (WBV)-induced muscular reflex (WBV-IMR) are not well understood. To define a possible pathway for WBV-IMR, this study investigated the effects of WBV amplitude on WBV-IMR latency by surface electromyography analysis of the soleus muscle in human adult volunteers. The tendon (T) reflex was also induced to evaluate the level of presynaptic Ia inhibition during WBV. WBV-IMR latency was shorter when induced by low- as compared to medium- or high-amplitude WBV (33.9±5.3msvs. 43.8±3.6 and 44.1±4.2ms, respectively). There was no difference in latencies between T-reflex elicited before WBV (33.8±2.4ms) and WBV-IMR induced by low-amplitude WBV. Presynaptic Ia inhibition was absent during low-amplitude WBV but was present during medium- and high-amplitude WBV. Consequently, WBV induces short- or long-latency reflexes depending on the vibration amplitude. During low-amplitude WBV, muscle spindle activation may induce the short- but not the long-latency WBV-IMR. Furthermore, unlike the higher amplitude WBV, low-amplitude WBV does not induce presynaptic inhibition at the Ia synaptic terminals. Copyright © 2017 Elsevier Ltd. All rights reserved.

Interference resolution in major depression.

PubMed

Joormann, Jutta; Nee, Derek Evan; Berman, Marc G; Jonides, John; Gotlib, Ian H

2010-03-01

In two experiments, we investigated individual differences in the ability to resolve interference in participants diagnosed with major depressive disorder (MDD). Participants were administered the "Ignore/Suppress" task, a short-term memory task composed of two steps. In Step 1 ("ignore"), participants were instructed to memorize a set of stimuli while ignoring simultaneously presented irrelevant material. In Step 2 ("suppress"), participants were instructed to forget a subset of the previously memorized material. The ability to resolve interference was indexed by response latencies on two recognition tasks in which participants decided whether a probe was a member of the target set. In Step 1, we compared response latencies to probes from the to-be-ignored list with response latencies to nonrecently presented items. In Step 2, we compared response latencies to probes from the to-be-suppressed list with response latencies to nonrecently presented items. The results indicate that, compared with control participants, depressed participants exhibited increased interference in the "suppress" but not in the "ignore" step of the task, when the stimuli were negative words. No group differences were obtained when we presented letters instead of emotional words. These findings indicate that depression is associated with difficulty in removing irrelevant negative material from short-term memory.

Multifocal visual evoked potential in optic neuritis, ischemic optic neuropathy and compressive optic neuropathy

PubMed Central

Jayaraman, Manju; Gandhi, Rashmin Anilkumar; Ravi, Priya; Sen, Parveen

2014-01-01

Purpose: To investigate the effect of optic neuritis (ON), ischemic optic neuropathy (ION) and compressive optic neuropathy (CON) on multifocal visual evoked potential (mfVEP) amplitudes and latencies, and to compare the parameters among three optic nerve disorders. Materials and Methods: mfVEP was recorded for 71 eyes of controls and 48 eyes of optic nerve disorders with subgroups of optic neuritis (ON, n = 21 eyes), ischemic optic neuropathy (ION, n = 14 eyes), and compressive optic neuropathy (CON, n = 13 eyes). The size of defect in mfVEP amplitude probability plots and relative latency plots were analyzed. The pattern of the defect in amplitude probability plot was classified according to the visual field profile of optic neuritis treatment trail (ONTT). Results: Median of mfVEP amplitude (log SNR) averaged across 60 sectors were reduced in ON (0.17 (0.13-0.33)), ION (0.14 (0.12-0.21)) and CON (0.21 (0.14-0.30)) when compared to controls. The median mfVEP relative latencies compared to controls were significantly prolonged in ON and CON group of 10.53 (2.62-15.50) ms and 5.73 (2.67-14.14) ms respectively compared to ION group (2.06 (-4.09-13.02)). The common mfVEP amplitude defects observed in probability plots were diffuse pattern in ON, inferior altitudinal defect in ION and temporal hemianopia in CON eyes. Conclusions: Optic nerve disorders cause reduction in mfVEP amplitudes. The extent of delayed latency noted in ischemic optic neuropathy was significantly lesser compared to subjects with optic neuritis and compressive optic neuropathy. mfVEP amplitudes can be used to objectively assess the topography of the visual field defect. PMID:24088641

Modality-specificity of sensory aging in vision and audition: evidence from event-related potentials.

PubMed

Ceponiene, R; Westerfield, M; Torki, M; Townsend, J

2008-06-18

Major accounts of aging implicate changes in processing external stimulus information. Little is known about differential effects of auditory and visual sensory aging, and the mechanisms of sensory aging are still poorly understood. Using event-related potentials (ERPs) elicited by unattended stimuli in younger (M=25.5 yrs) and older (M=71.3 yrs) subjects, this study examined mechanisms of sensory aging under minimized attention conditions. Auditory and visual modalities were examined to address modality-specificity vs. generality of sensory aging. Between-modality differences were robust. The earlier-latency responses (P1, N1) were unaffected in the auditory modality but were diminished in the visual modality. The auditory N2 and early visual N2 were diminished. Two similarities between the modalities were age-related enhancements in the late P2 range and positive behavior-early N2 correlation, the latter suggesting that N2 may reflect long-latency inhibition of irrelevant stimuli. Since there is no evidence for salient differences in neuro-biological aging between the two sensory regions, the observed between-modality differences are best explained by the differential reliance of auditory and visual systems on attention. Visual sensory processing relies on facilitation by visuo-spatial attention, withdrawal of which appears to be more disadvantageous in older populations. In contrast, auditory processing is equipped with powerful inhibitory capacities. However, when the whole auditory modality is unattended, thalamo-cortical gating deficits may not manifest in the elderly. In contrast, ERP indices of longer-latency, stimulus-level inhibitory modulation appear to diminish with age.

Neural cascade of conflict processing: Not just time-on-task.

PubMed

McKay, Cameron C; van den Berg, Berry; Woldorff, Marty G

2017-02-01

In visual conflict tasks (e.g., Stroop or flanker), response times (RTs) are generally longer on incongruent trials relative to congruent ones. Two event-related-potential (ERP) components classically associated with the processing of stimulus conflict are the fronto-central, incongruency-related negativity (N inc ) and the posterior late-positive complex (LPC), which are derived from the ERP difference waves for incongruent minus congruent trials. It has been questioned, however, whether these effects, or other neural measures of incongruency (e.g., fMRI responses in the anterior cingulate), reflect true conflict processing, or whether such effects derive mainly from differential time-on-task. To address this question, we leveraged high-temporal-resolution ERP measures of brain activity during two behavioral tasks. The first task, a modified Erikson flanker paradigm (with congruent and incongruent trials), was used to evoke the classic RT and ERP effects associated with conflict. The second was a non-conflict control task in which, participants visually discriminated a single stimulus (with easy and hard discrimination conditions). Behaviorally, the parameters were titrated to yield similar RT effects of conflict and difficulty (27ms). Neurally, both within-task contrasts showed an initial fronto-central negative-polarity wave (N2-latency effect), but they then diverged. In the difficulty difference wave, the initial negativity led directly into the posterior LPC, whereas in the incongruency contrast the initial negativity was followed a by a second fronto-central negative peak (N inc ), which was then followed by a considerably longer-latency LPC. These results provide clear evidence that the longer processing for incongruent stimulus inputs do not just reflect time-on-task or difficulty, but include a true conflict-processing component. Copyright © 2017 Elsevier Ltd. All rights reserved.

Neural cascade of conflict processing: not just time-on-task

PubMed Central

McKay, Cameron C.; van den Berg, Berry; Woldorff, Marty G.

2017-01-01

In visual conflict tasks (e.g., Stroop or flanker), response times (RTs) are generally longer on incongruent trials relative to congruent ones. Two event-related-potential (ERP) components classically associated with the processing of stimulus conflict are the fronto-central, incongruency-related negativity (Ninc) and the posterior late-positive complex (LPC), which are derived from the ERP difference waves for incongruent minus congruent trials. It has been questioned, however, whether these effects, or other neural measures of incongruency (e.g., fMRI responses in the anterior cingulate), reflect true conflict processing, or whether such effects derive mainly from differential time-on-task. To address this question, we leveraged high-temporal-resolution ERP measures of brain activity during two behavioral tasks. The first task, a modified Erikson flanker paradigm (with congruent and incongruent trials), was used to evoke the classic RT and ERP effects associated with conflict. In the second, a non-conflict comparison condition, participants visually discriminated a single stimulus (with easy and hard discrimination conditions). Behaviorally, the parameters were titrated to yield similar RT effects of conflict and difficulty (27 ms). Neurally, both within-task contrasts showed an initial fronto-central negative-polarity wave (N2-latency effect), but they then diverged. In the difficulty difference wave, the initial negativity led directly into the posterior LPC, whereas in the incongruency contrast the initial negativity was followed a by a second fronto-central negative peak (Ninc), which was then followed by a considerably longer-latency LPC. These results provide clear evidence that the longer processing for incongruent stimulus inputs do not just reflect time-on-task or difficulty, but include a true conflict-processing component. PMID:28017818

Postural and Spatial Orientation Driven by Virtual Reality

PubMed Central

Keshner, Emily A.; Kenyon, Robert V.

2009-01-01

Orientation in space is a perceptual variable intimately related to postural orientation that relies on visual and vestibular signals to correctly identify our position relative to vertical. We have combined a virtual environment with motion of a posture platform to produce visual-vestibular conditions that allow us to explore how motion of the visual environment may affect perception of vertical and, consequently, affect postural stabilizing responses. In order to involve a higher level perceptual process, we needed to create a visual environment that was immersive. We did this by developing visual scenes that possess contextual information using color, texture, and 3-dimensional structures. Update latency of the visual scene was close to physiological latencies of the vestibulo-ocular reflex. Using this system we found that even when healthy young adults stand and walk on a stable support surface, they are unable to ignore wide field of view visual motion and they adapt their postural orientation to the parameters of the visual motion. Balance training within our environment elicited measurable rehabilitation outcomes. Thus we believe that virtual environments can serve as a clinical tool for evaluation and training of movement in situations that closely reflect conditions found in the physical world. PMID:19592796

Quantification of mid and late evoked sinks in laminar current source density profiles of columns in the primary auditory cortex

PubMed Central

Schaefer, Markus K.; Hechavarría, Julio C.; Kössl, Manfred

2015-01-01

Current source density (CSD) analysis assesses spatiotemporal synaptic activations at somatic and/or dendritic levels in the form of depolarizing current sinks. Whereas many studies have focused on the short (<50 ms) latency sinks, associated with thalamocortical projections, sinks with longer latencies have received less attention. Here, we analyzed laminar CSD patterns for the first 600 ms after stimulus onset in the primary auditory cortex of Mongolian gerbils. By applying an algorithm for contour calculation, three distinct mid and four late evoked sinks were identified in layers I, III, Va, VIa, and VIb. Our results further showed that the patterns of intracortical information-flow remained qualitatively similar for low and for high sound pressure level stimuli at the characteristic frequency (CF) as well as for stimuli ± 1 octave from CF. There were, however, differences associated with the strength, vertical extent, onset latency, and duration of the sinks for the four stimulation paradigms used. Stimuli one octave above the most sensitive frequency evoked a new, and quite reliable, sink in layer Va whereas low level stimulation led to the disappearance of the layer VIb sink. These data indicate the presence of input sources specifically activated in response to level and/or frequency parameters. Furthermore, spectral integration above vs. below the CF of neurons is asymmetric as illustrated by CSD profiles. These results are important because synaptic feedback associated with mid and late sinks—beginning at 50 ms post stimulus latency—is likely crucial for response modulation resulting from higher order processes like memory, learning or cognitive control. PMID:26557058

Sequential dynamics in visual short-term memory.

PubMed

Kool, Wouter; Conway, Andrew R A; Turk-Browne, Nicholas B

2014-10-01

Visual short-term memory (VSTM) is thought to help bridge across changes in visual input, and yet many studies of VSTM employ static displays. Here we investigate how VSTM copes with sequential input. In particular, we characterize the temporal dynamics of several different components of VSTM performance, including: storage probability, precision, variability in precision, guessing, and swapping. We used a variant of the continuous-report VSTM task developed for static displays, quantifying the contribution of each component with statistical likelihood estimation, as a function of serial position and set size. In Experiments 1 and 2, storage probability did not vary by serial position for small set sizes, but showed a small primacy effect and a robust recency effect for larger set sizes; precision did not vary by serial position or set size. In Experiment 3, the recency effect was shown to reflect an increased likelihood of swapping out items from earlier serial positions and swapping in later items, rather than an increased rate of guessing for earlier items. Indeed, a model that incorporated responding to non-targets provided a better fit to these data than alternative models that did not allow for swapping or that tried to account for variable precision. These findings suggest that VSTM is updated in a first-in-first-out manner, and they bring VSTM research into closer alignment with classical working memory research that focuses on sequential behavior and interference effects.

Sequential dynamics in visual short-term memory

PubMed Central

Conway, Andrew R. A.; Turk-Browne, Nicholas B.

2014-01-01

Visual short-term memory (VSTM) is thought to help bridge across changes in visual input, and yet many studies of VSTM employ static displays. Here we investigate how VSTM copes with sequential input. In particular, we characterize the temporal dynamics of several different components of VSTM performance, including: storage probability, precision, variability in precision, guessing, and swapping. We used a variant of the continuous-report VSTM task developed for static displays, quantifying the contribution of each component with statistical likelihood estimation, as a function of serial position and set size. In Experiments 1 and 2, storage probability did not vary by serial position for small set sizes, but showed a small primacy effect and a robust recency effect for larger set sizes; precision did not vary by serial position or set size. In Experiment 3, the recency effect was shown to reflect an increased likelihood of swapping out items from earlier serial positions and swapping in later items, rather than an increased rate of guessing for earlier items. Indeed, a model that incorporated responding to non-targets provided a better fit to these data than alternative models that did not allow for swapping or that tried to account for variable precision. These findings suggest that VSTM is updated in a first-in-first-out manner, and they bring VSTM research into closer alignment with classical working memory research that focuses on sequential behavior and interference effects. PMID:25228092

Encoding of Target Detection during Visual Search by Single Neurons in the Human Brain.

PubMed

Wang, Shuo; Mamelak, Adam N; Adolphs, Ralph; Rutishauser, Ueli

2018-06-08

Neurons in the primate medial temporal lobe (MTL) respond selectively to visual categories such as faces, contributing to how the brain represents stimulus meaning. However, it remains unknown whether MTL neurons continue to encode stimulus meaning when it changes flexibly as a function of variable task demands imposed by goal-directed behavior. While classically associated with long-term memory, recent lesion and neuroimaging studies show that the MTL also contributes critically to the online guidance of goal-directed behaviors such as visual search. Do such tasks modulate responses of neurons in the MTL, and if so, do their responses mirror bottom-up input from visual cortices or do they reflect more abstract goal-directed properties? To answer these questions, we performed concurrent recordings of eye movements and single neurons in the MTL and medial frontal cortex (MFC) in human neurosurgical patients performing a memory-guided visual search task. We identified a distinct population of target-selective neurons in both the MTL and MFC whose response signaled whether the currently fixated stimulus was a target or distractor. This target-selective response was invariant to visual category and predicted whether a target was detected or missed behaviorally during a given fixation. The response latencies, relative to fixation onset, of MFC target-selective neurons preceded those in the MTL by ∼200 ms, suggesting a frontal origin for the target signal. The human MTL thus represents not only fixed stimulus identity, but also task-specified stimulus relevance due to top-down goal relevance. Copyright © 2018 Elsevier Ltd. All rights reserved.

Earlier saccades to task-relevant targets irrespective of relative gain between peripheral and foveal information.

PubMed

Wolf, Christian; Schütz, Alexander C

2017-06-01

Saccades bring objects of interest onto the fovea for high-acuity processing. Saccades to rewarded targets show shorter latencies that correlate negatively with expected motivational value. Shorter latencies are also observed when the saccade target is relevant for a perceptual discrimination task. Here we tested whether saccade preparation is equally influenced by informational value as it is by motivational value. We defined informational value as the probability that information is task-relevant times the ratio between postsaccadic foveal and presaccadic peripheral discriminability. Using a gaze-contingent display, we independently manipulated peripheral and foveal discriminability of the saccade target. Latencies of saccades with perceptual task were reduced by 36 ms in general, but they were not modulated by the information saccades provide (Experiments 1 and 2). However, latencies showed a clear negative linear correlation with the probability that the target is task-relevant (Experiment 3). We replicated that the facilitation by a perceptual task is spatially specific and not due to generally heightened arousal (Experiment 4). Finally, the facilitation only emerged when the perceptual task is in the visual but not in the auditory modality (Experiment 5). Taken together, these results suggest that saccade latencies are not equally modulated by informational value as by motivational value. The facilitation by a perceptual task only arises when task-relevant visual information is foveated, irrespective of whether the foveation is useful or not.

Optoelectronic-cache memory system architecture.

PubMed

Chiarulli, D M; Levitan, S P

1996-05-10

We present an investigation of the architecture of an optoelectronic cache that can integrate terabit optical memories with the electronic caches associated with high-performance uniprocessors and multiprocessors. The use of optoelectronic-cache memories enables these terabit technologies to provide transparently low-latency secondary memory with frame sizes comparable with disk pages but with latencies that approach those of electronic secondary-cache memories. This enables the implementation of terabit memories with effective access times comparable with the cycle times of current microprocessors. The cache design is based on the use of a smart-pixel array and combines parallel free-space optical input-output to-and-from optical memory with conventional electronic communication to the processor caches. This cache and the optical memory system to which it will interface provide a large random-access memory space that has a lower overall latency than that of magnetic disks and disk arrays. In addition, as a consequence of the high-bandwidth parallel input-output capabilities of optical memories, fault service times for the optoelectronic cache are substantially less than those currently achievable with any rotational media.

JPEG XS, a new standard for visually lossless low-latency lightweight image compression

NASA Astrophysics Data System (ADS)

Descampe, Antonin; Keinert, Joachim; Richter, Thomas; Fößel, Siegfried; Rouvroy, Gaël.

2017-09-01

JPEG XS is an upcoming standard from the JPEG Committee (formally known as ISO/IEC SC29 WG1). It aims to provide an interoperable visually lossless low-latency lightweight codec for a wide range of applications including mezzanine compression in broadcast and Pro-AV markets. This requires optimal support of a wide range of implementation technologies such as FPGAs, CPUs and GPUs. Targeted use cases are professional video links, IP transport, Ethernet transport, real-time video storage, video memory buffers, and omnidirectional video capture and rendering. In addition to the evaluation of the visual transparency of the selected technologies, a detailed analysis of the hardware and software complexity as well as the latency has been done to make sure that the new codec meets the requirements of the above-mentioned use cases. In particular, the end-to-end latency has been constrained to a maximum of 32 lines. Concerning the hardware complexity, neither encoder nor decoder should require more than 50% of an FPGA similar to Xilinx Artix 7 or 25% of an FPGA similar to Altera Cyclon 5. This process resulted in a coding scheme made of an optional color transform, a wavelet transform, the entropy coding of the highest magnitude level of groups of coefficients, and the raw inclusion of the truncated wavelet coefficients. This paper presents the details and status of the standardization process, a technical description of the future standard, and the latest performance evaluation results.

The timing of sequences of saccades in visual search.

PubMed Central

Van Loon, E M; Hooge, I Th C; Van den Berg, A V

2002-01-01

According to the LATER model (linear approach to thresholds with ergodic rate), the latency of a single saccade in response to target appearance can be understood as a decision process, which is subject to (i) variations in the rate of (visual) information processing; and (ii) the threshold for the decision. We tested whether the LATER model can also be applied to the sequences of saccades in a multiple fixation search, during which latencies of second and subsequent saccades are typically shorter than that of the initial saccade. We found that the distributions of the reciprocal latencies for later saccades, unlike those of the first saccade, are highly asymmetrical, much like a gamma distribution. This suggests that the normal distribution of the rate r, which the LATER model assumes, is not appropriate to describe the rate distributions of subsequent saccades in a scanning sequence. By contrast, the gamma distribution is also appropriate to describe the distribution of reciprocal latencies for the first saccade. The change of the gamma distribution parameters as a function of the ordinal number of the saccade suggests a lowering of the threshold for second and later saccades, as well as a reduction in the number of target elements analysed. PMID:12184827

An electrophysiological follow up of patients with n-hexane polyneuropathy.

PubMed Central

Chang, Y C

1991-01-01

Electroneurographic (ENeG) and evoked potential (EP) studies were regularly performed on 11 printing workers with n-hexane polyneuropathy after cessation of exposure. At the initial examination, the ENeG studies simulated a demyelinative process. Further slowing of nerve conduction velocity, or further decreasing of action potential amplitude, or both in the follow up ENeG study were found in about half the patients. The motor distal latency did not worsen. Nerve conduction returned to normal earlier in the sensory than in the motor nerves. After the patients had regained full motor capability, conduction velocities in motor nerves were still significantly slowed. These ENeG characteristics correlate with the pathological and pathophysiological changes in experimental hexa-carbon neuropathies. The initial findings from the EP studies indicated a conduction abnormality in the central nervous system (CNS). Delayed worsening occurred in the amplitude of visual EPs in three patients. On serial follow up, the interpeak latency and interpeak amplitude of visual EPs improved little. Residual abnormalities were also found in the interpeak latency of auditory EPs in the brainstem and in the absolute latency of scalp somatosensory EPs from the peroneal nerve. Astroglial proliferation in the CNS probably impedes recovery of the abnormalities in EP. PMID:1993154

Response time as a discriminator between true- and false-positive responses in suprathreshold perimetry.

PubMed

Artes, Paul H; McLeod, David; Henson, David B

2002-01-01

To report on differences between the latency distributions of responses to stimuli and to false-positive catch trials in suprathreshold perimetry. To describe an algorithm for defining response time windows and to report on its performance in discriminating between true- and false-positive responses on the basis of response time (RT). A sample of 435 largely inexperienced patients underwent suprathreshold visual field examination on a perimeter that was modified to record RTs. Data were analyzed from 60,500 responses to suprathreshold stimuli and from 523 false-positive responses to catch trials. False-positive responses had much more variable latencies than responses to suprathreshold stimuli. An algorithm defining RT windows on the basis of z-transformed individual latency samples correctly identified more than 70% of false-positive responses to catch trials, whereas fewer than 3% of responses to suprathreshold stimuli were classified as false-positive responses. Latency analysis can be used to detect a substantial proportion of false-positive responses in suprathreshold perimetry. Rejection of such responses may increase the reliability of visual field screening by reducing variability and bias in a small but clinically important proportion of patients.

Effects of refractive errors on visual evoked magnetic fields.

PubMed

Suzuki, Masaya; Nagae, Mizuki; Nagata, Yuko; Kumagai, Naoya; Inui, Koji; Kakigi, Ryusuke

2015-11-09

The latency and amplitude of visual evoked cortical responses are known to be affected by refractive states, suggesting that they may be used as an objective index of refractive errors. In order to establish an easy and reliable method for this purpose, we herein examined the effects of refractive errors on visual evoked magnetic fields (VEFs). Binocular VEFs following the presentation of a simple grating of 0.16 cd/m(2) in the lower visual field were recorded in 12 healthy volunteers and compared among four refractive states: 0D, +1D, +2D, and +4D, by using plus lenses. The low-luminance visual stimulus evoked a main MEG response at approximately 120 ms (M100) that reversed its polarity between the upper and lower visual field stimulations and originated from the occipital midline area. When refractive errors were induced by plus lenses, the latency of M100 increased, while its amplitude decreased with an increase in power of the lens. Differences from the control condition (+0D) were significant for all three lenses examined. The results of dipole analyses showed that evoked fields for the control (+0D) condition were explainable by one dipole in the primary visual cortex (V1), while other sources, presumably in V3 or V6, slightly contributed to shape M100 for the +2D or +4D condition. The present results showed that the latency and amplitude of M100 are both useful indicators for assessing refractive states. The contribution of neural sources other than V1 to M100 was modest under the 0D and +1D conditions. By considering the nature of the activity of M100 including its high sensitivity to a spatial frequency and lower visual field dominance, a simple low-luminance grating stimulus at an optimal spatial frequency in the lower visual field appears appropriate for obtaining data on high S/N ratios and reducing the load on subjects.

Simultaneous diffuse near-infrared imaging of hemodynamic and oxygenation changes and electroencephalographic measurements of neuronal activity in the human brain

NASA Astrophysics Data System (ADS)

Noponen, Tommi; Kicic, Dubravko; Kotilahti, Kalle; Kajava, Timo; Kahkonen, Seppo; Nissila, Ilkka; Merilainen, Pekka; Katila, Toivo

2005-04-01

Visually evoked hemodynamic responses and potentials were simultaneously measured using a 16-channel optical imaging instrument and a 60-channel electroencephalography instrument during normo-, hypo- and hypercapnia from three subjects. Flashing and pattern-reversed checkerboard stimuli were used. The study protocol included two counterbalanced measurements during both normo- and hypocapnia and normo- and hypercapnia. Hypocapnia was produced by controlled hyperventilation and hypercapnia by breathing carbon dioxide enriched air. Near-infrared imaging was also used to monitor the concentration changes of oxy- and deoxyhaemoglobin due to hypo- and hypercapnia. Hemodynamic responses and evoked potentials were successfully detected for each subject above the visual cortex. The latencies of the hemodynamic responses during hypocapnia were shorter whereas during hypercapnia they were longer when compared to the latencies during normocapnia. Hypocapnia tended to decrease the latencies of visually evoked potentials compared to those during normocapnia while hypercapnia did not show any consistent effect to the potentials. The developed measurement setup and the study protocol provide the opportunity to investigate the neurovascular coupling and the links between the baseline level of blood flow, electrical activity and hemodynamic responses in the human brain.

Phonological, visual, and semantic coding strategies and children's short-term picture memory span.

PubMed

Henry, Lucy A; Messer, David; Luger-Klein, Scarlett; Crane, Laura

2012-01-01

Three experiments addressed controversies in the previous literature on the development of phonological and other forms of short-term memory coding in children, using assessments of picture memory span that ruled out potentially confounding effects of verbal input and output. Picture materials were varied in terms of phonological similarity, visual similarity, semantic similarity, and word length. Older children (6/8-year-olds), but not younger children (4/5-year-olds), demonstrated robust and consistent phonological similarity and word length effects, indicating that they were using phonological coding strategies. This confirmed findings initially reported by Conrad (1971), but subsequently questioned by other authors. However, in contrast to some previous research, little evidence was found for a distinct visual coding stage at 4 years, casting doubt on assumptions that this is a developmental stage that consistently precedes phonological coding. There was some evidence for a dual visual and phonological coding stage prior to exclusive use of phonological coding at around 5-6 years. Evidence for semantic similarity effects was limited, suggesting that semantic coding is not a key method by which young children recall lists of pictures.

Dynamics of infant cortical auditory evoked potentials (CAEPs) for tone and speech tokens.

PubMed

Cone, Barbara; Whitaker, Richard

2013-07-01

Cortical auditory evoked potentials (CAEPs) to tones and speech sounds were obtained in infants to: (1) further knowledge of auditory development above the level of the brainstem during the first year of life; (2) establish CAEP input-output functions for tonal and speech stimuli as a function of stimulus level and (3) elaborate the data-base that establishes CAEP in infants tested while awake using clinically relevant stimuli, thus providing methodology that would have translation to pediatric audiological assessment. Hypotheses concerning CAEP development were that the latency and amplitude input-output functions would reflect immaturity in encoding stimulus level. In a second experiment, infants were tested with the same stimuli used to evoke the CAEPs. Thresholds for these stimuli were determined using observer-based psychophysical techniques. The hypothesis was that the behavioral thresholds would be correlated with CAEP input-output functions because of shared cortical response areas known to be active in sound detection. 36 infants, between the ages of 4 and 12 months (mean=8 months, s.d.=1.8 months) and 9 young adults (mean age 21 years) with normal hearing were tested. First, CAEPs amplitude and latency input-output functions were obtained for 4 tone bursts and 7 speech tokens. The tone bursts stimuli were 50 ms tokens of pure tones at 0.5, 1.0, 2.0 and 4.0 kHz. The speech sound tokens, /a/, /i/, /o/, /u/, /m/, /s/, and /∫/, were created from natural speech samples and were also 50 ms in duration. CAEPs were obtained for tone burst and speech token stimuli at 10 dB level decrements in descending order from 70 dB SPL. All CAEP tests were completed while the infants were awake and engaged in quiet play. For the second experiment, observer-based psychophysical methods were used to establish perceptual threshold for the same speech sound and tone tokens. Infant CAEP component latencies were prolonged by 100-150 ms in comparison to adults. CAEP latency-intensity input output functions were steeper in infants compared to adults. CAEP amplitude growth functions with respect to stimulus SPL are adult-like at this age, particularly for the earliest component, P1-N1. Infant perceptual thresholds were elevated with respect to those found in adults. Furthermore, perceptual thresholds were higher, on average, than levels at which CAEPs could be obtained. When CAEP amplitudes were plotted with respect to perceptual threshold (dB SL), the infant CAEP amplitude growth slopes were steeper than in adults. Although CAEP latencies indicate immaturity in neural transmission at the level of the cortex, amplitude growth with respect to stimulus SPL is adult-like at this age, particularly for the earliest component, P1-N1. The latency and amplitude input-output functions may provide additional information as to how infants perceive stimulus level. The reasons for the discrepancy between electrophysiologic and perceptual threshold may be due to immaturity in perceptual temporal resolution abilities and the broad-band listening strategy employed by infants. The findings from the current study can be translated to the clinical setting. It is possible to use tonal or speech sound tokens to evoke CAEPs in an awake, passively alert infant, and thus determine whether these sounds activate the auditory cortex. This could be beneficial in the verification of hearing aid or cochlear implant benefit. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

What triggers catch-up saccades during visual tracking?

PubMed

de Brouwer, Sophie; Yuksel, Demet; Blohm, Gunnar; Missal, Marcus; Lefèvre, Philippe

2002-03-01

When tracking moving visual stimuli, primates orient their visual axis by combining two kinds of eye movements, smooth pursuit and saccades, that have very different dynamics. Yet, the mechanisms that govern the decision to switch from one type of eye movement to the other are still poorly understood, even though they could bring a significant contribution to the understanding of how the CNS combines different kinds of control strategies to achieve a common motor and sensory goal. In this study, we investigated the oculomotor responses to a large range of different combinations of position error and velocity error during visual tracking of moving stimuli in humans. We found that the oculomotor system uses a prediction of the time at which the eye trajectory will cross the target, defined as the "eye crossing time" (T(XE)). The eye crossing time, which depends on both position error and velocity error, is the criterion used to switch between smooth and saccadic pursuit, i.e., to trigger catch-up saccades. On average, for T(XE) between 40 and 180 ms, no saccade is triggered and target tracking remains purely smooth. Conversely, when T(XE) becomes smaller than 40 ms or larger than 180 ms, a saccade is triggered after a short latency (around 125 ms).

Infant Visual Expectations: Advances and Issues.

ERIC Educational Resources Information Center

Haith, Marshall M.; Wass, Tara S.; Adler, Scott A.

1997-01-01

Speculates on underlying processes for the reaction time variance and age differences in anticipation latency using the Visual Expectation Paradigm. Discusses the dichotomization of reactive and anticipatory behavior, limitations of longitudinal designs, drawbacks in using standard procedures and materials, and inferences that can be made…

Setting and changing feature priorities in visual short-term memory.

PubMed

Kalogeropoulou, Zampeta; Jagadeesh, Akshay V; Ohl, Sven; Rolfs, Martin

2017-04-01

Many everyday tasks require prioritizing some visual features over competing ones, both during the selection from the rich sensory input and while maintaining information in visual short-term memory (VSTM). Here, we show that observers can change priorities in VSTM when, initially, they attended to a different feature. Observers reported from memory the orientation of one of two spatially interspersed groups of black and white gratings. Using colored pre-cues (presented before stimulus onset) and retro-cues (presented after stimulus offset) predicting the to-be-reported group, we manipulated observers' feature priorities independently during stimulus encoding and maintenance, respectively. Valid pre-cues reliably increased observers' performance (reduced guessing, increased report precision) as compared to neutral ones; invalid pre-cues had the opposite effect. Valid retro-cues also consistently improved performance (by reducing random guesses), even if the unexpected group suddenly became relevant (invalid-valid condition). Thus, feature-based attention can reshape priorities in VSTM protecting information that would otherwise be forgotten.

Electrophysiological evidence for early perceptual facilitation and efficient categorization of self-related stimuli during an Implicit Association Test measuring neuroticism.

PubMed

Fleischhauer, Monika; Strobel, Alexander; Diers, Kersten; Enge, Sören

2014-02-01

The Implicit Association Test (IAT) is a widely used latency-based categorization task that indirectly measures the strength of automatic associations between target and attribute concepts. So far, little is known about the perceptual and cognitive processes underlying personality IATs. Thus, the present study examined event-related potential indices during the execution of an IAT measuring neuroticism (N  =  70). The IAT effect was strongly modulated by the P1 component indicating early facilitation of relevant visual input and by a P3b-like late positive component reflecting the efficacy of stimulus categorization. Both components covaried, and larger amplitudes led to faster responses. The results suggest a relationship between early perceptual and semantic processes operating at a more automatic, implicit level and later decision-related categorization of self-relevant stimuli contributing to the IAT effect. Copyright © 2013 Society for Psychophysiological Research.

Primary Visual Cortex as a Saliency Map: A Parameter-Free Prediction and Its Test by Behavioral Data

PubMed Central

Zhaoping, Li; Zhe, Li

2015-01-01

It has been hypothesized that neural activities in the primary visual cortex (V1) represent a saliency map of the visual field to exogenously guide attention. This hypothesis has so far provided only qualitative predictions and their confirmations. We report this hypothesis’ first quantitative prediction, derived without free parameters, and its confirmation by human behavioral data. The hypothesis provides a direct link between V1 neural responses to a visual location and the saliency of that location to guide attention exogenously. In a visual input containing many bars, one of them saliently different from all the other bars which are identical to each other, saliency at the singleton’s location can be measured by the shortness of the reaction time in a visual search for singletons. The hypothesis predicts quantitatively the whole distribution of the reaction times to find a singleton unique in color, orientation, and motion direction from the reaction times to find other types of singletons. The prediction matches human reaction time data. A requirement for this successful prediction is a data-motivated assumption that V1 lacks neurons tuned simultaneously to color, orientation, and motion direction of visual inputs. Since evidence suggests that extrastriate cortices do have such neurons, we discuss the possibility that the extrastriate cortices play no role in guiding exogenous attention so that they can be devoted to other functions like visual decoding and endogenous attention. PMID:26441341

Preterm delivery at low gestational age: risk factors for short latency. A multivariated analysis

PubMed Central

Marzano, Sara; Padula, Francesco; Meloni, Paolo; Anceschi, Maurizio Marco

2008-01-01

Objective The aim of this study is to identify the risk factors for a short latency in preterm delivery at low gestational ages (GA). Study design A retrospective analysis involving, between January 2004 and May 2006, 204 singleton pregnancies with admission diagnosis of preterm labor and, in particular, 91 pregnant women admitted between 24+0 and 31+6 weeks’ gestation. Results In pregnant women with a diagnosis of preterm labor at 24-31+6 weeks’ gestation, at ROC curve, a value of considering WBC and cervical dilatation, combined in the following formula (75.237 - (2.290 * “WBC”) - (10.787 * “cervical dilatation”)) <=33.101 has a 74.2% Sensitivity and a 78.3% Specificity in predicting a latency =< 4 days (+LR 3.42 and -LR 0.33) and a 70% Sensitivity and a 84.3% Specificity in predicting GA at delivery at 24-31 weeks’ gestation (+LR 4.46 and -LR 0.36). Conclusion We suggest a more strictly monitoring and a more aggressive therapy in presence of prognostic parameters of shorter latency. PMID:22439021

Interval timing in genetically modified mice: a simple paradigm

PubMed Central

Balci, F.; Papachristos, E. B.; Gallistel, C. R.; Brunner, D.; Gibson, J.; Shumyatsky, G. P.

2009-01-01

We describe a behavioral screen for the quantitative study of interval timing and interval memory in mice. Mice learn to switch from a short-latency feeding station to a long-latency station when the short latency has passed without a feeding. The psychometric function is the cumulative distribution of switch latencies. Its median measures timing accuracy and its interquartile interval measures timing precision. Next, using this behavioral paradigm, we have examined mice with a gene knockout of the receptor for gastrin-releasing peptide that show enhanced (i.e. prolonged) freezing in fear conditioning. We have tested the hypothesis that the mutants freeze longer because they are more uncertain than wild types about when to expect the electric shock. The knockouts however show normal accuracy and precision in timing, so we have rejected this alternative hypothesis. Last, we conduct the pharmacological validation of our behavioral screen using D-amphetamine and methamphetamine. We suggest including the analysis of interval timing and temporal memory in tests of genetically modified mice for learning and memory and argue that our paradigm allows this to be done simply and efficiently. PMID:17696995

Interval timing in genetically modified mice: a simple paradigm.

PubMed

Balci, F; Papachristos, E B; Gallistel, C R; Brunner, D; Gibson, J; Shumyatsky, G P

2008-04-01

We describe a behavioral screen for the quantitative study of interval timing and interval memory in mice. Mice learn to switch from a short-latency feeding station to a long-latency station when the short latency has passed without a feeding. The psychometric function is the cumulative distribution of switch latencies. Its median measures timing accuracy and its interquartile interval measures timing precision. Next, using this behavioral paradigm, we have examined mice with a gene knockout of the receptor for gastrin-releasing peptide that show enhanced (i.e. prolonged) freezing in fear conditioning. We have tested the hypothesis that the mutants freeze longer because they are more uncertain than wild types about when to expect the electric shock. The knockouts however show normal accuracy and precision in timing, so we have rejected this alternative hypothesis. Last, we conduct the pharmacological validation of our behavioral screen using d-amphetamine and methamphetamine. We suggest including the analysis of interval timing and temporal memory in tests of genetically modified mice for learning and memory and argue that our paradigm allows this to be done simply and efficiently.

Normalization of auditory evoked potential and visual evoked potential in patients with idiot savant.

PubMed

Chen, X; Zhang, M; Wang, J; Lou, F; Liang, J

1999-03-01

To investigate the variations of auditory evoked potentials (AEP) and visual evoked potentials (VEP) of patients with idiot savant (IS) syndrome. Both AEP and VEP were recorded from 7 patients with IS syndrome, 21 mentally retarded (MR) children without the syndrome and 21 normally age-matched controls, using a Dantec concerto SEEG-16 BEAM instrument. Both AEP and VEP of MR group showed significantly longer latencies (P1 and P2 latencies of AEP, P < 0.01; N1 and N2 latencies of VEP, P < 0.01/0.05), lower P2 amplitudes (P < 0.01) and higher P3 amplitudes (P < 0.01), as compared with normal controls. But none of above-mentioned changes was found with IS group. Almost all MR patients (90.1%) presented P4 component in both AEP and VEP, which was also in sharp contrast with its incidence in other 2 groups (IS: 14.3%; normal controls: 9.5%). Patients with idiot savant syndrome presented normalized AEP and VEP.

ScreenMasker: An Open-source Gaze-contingent Screen Masking Environment.

PubMed

Orlov, Pavel A; Bednarik, Roman

2016-09-01

The moving-window paradigm, based on gazecontingent technic, traditionally used in a studies of the visual perceptual span. There is a strong demand for new environments that could be employed by non-technical researchers. We have developed an easy-to-use tool with a graphical user interface (GUI) allowing both execution and control of visual gaze-contingency studies. This work describes ScreenMasker, an environment that allows create gaze-contingent textured displays used together with stimuli presentation software. ScreenMasker has an architecture that meets the requirements of low-latency real-time eye-movement experiments. It also provides a variety of settings and functions. Effective rendering times and performance are ensured by means of GPU processing under CUDA technology. Performance tests show ScreenMasker's latency to be 67-74 ms on a typical office computer, and high-end 144-Hz screen latencies of about 25-28 ms. ScreenMasker is an open-source system distributed under the GNU Lesser General Public License and is available at https://github.com/PaulOrlov/ScreenMasker .

Perception, memory and aesthetics of indeterminate art.

PubMed

Ishai, Alumit; Fairhall, Scott L; Pepperell, Robert

2007-07-12

Indeterminate art, in which familiar objects are only suggestive, invokes a perceptual conundrum as apparently detailed and vivid images resist identification. We hypothesized that compared with paintings that depict meaningful content, object recognition in indeterminate images would be delayed, and tested whether aesthetic affect depends on meaningful content. Subjects performed object recognition and judgment of aesthetic affect tasks. Response latencies were significantly longer for indeterminate images and subjects perceived recognizable objects in 24% of these paintings. Although the aesthetic affect rating of all paintings was similar, judgement latencies for the indeterminate paintings were significantly longer. A surprise memory test revealed that more representational than indeterminate paintings were remembered and that affective strength increased the probability of subsequent recall. Our results suggest that perception and memory of art depend on semantic aspects, whereas, aesthetic affect depends on formal visual features. The longer latencies associated with indeterminate paintings reflect the underlying cognitive processes that mediate object resolution. Indeterminate art works therefore comprise a rich set of stimuli with which the neural correlates of visual perception can be investigated.

VISIDEP™: visual image depth enhancement by parallax induction

NASA Astrophysics Data System (ADS)

Jones, Edwin R.; McLaurin, A. P.; Cathey, LeConte

1984-05-01

The usual descriptions of depth perception have traditionally required the simultaneous presentation of disparate views presented to separate eyes with the concomitant demand that the resulting binocular parallax be horizontally aligned. Our work suggests that the visual input information is compared in a short-term memory buffer which permits the brain to compute depth as it is normally perceived. However, the mechanism utilized is also capable of receiving and processing the stereographic information even when it is received monocularly or when identical inputs are simultaneously fed to both eyes. We have also found that the restriction to horizontally displaced images is not a necessary requirement and that improvement in image acceptability is achieved by the use of vertical parallax. Use of these ideas permit the presentation of three-dimensional scenes on flat screens in full color without the encumbrance of glasses or other viewing aids.

Neonatal Restriction of Tactile Inputs Leads to Long-Lasting Impairments of Cross-Modal Processing

PubMed Central

Röder, Brigitte; Hanganu-Opatz, Ileana L.

2015-01-01

Optimal behavior relies on the combination of inputs from multiple senses through complex interactions within neocortical networks. The ontogeny of this multisensory interplay is still unknown. Here, we identify critical factors that control the development of visual-tactile processing by combining in vivo electrophysiology with anatomical/functional assessment of cortico-cortical communication and behavioral investigation of pigmented rats. We demonstrate that the transient reduction of unimodal (tactile) inputs during a short period of neonatal development prior to the first cross-modal experience affects feed-forward subcortico-cortical interactions by attenuating the cross-modal enhancement of evoked responses in the adult primary somatosensory cortex. Moreover, the neonatal manipulation alters cortico-cortical interactions by decreasing the cross-modal synchrony and directionality in line with the sparsification of direct projections between primary somatosensory and visual cortices. At the behavioral level, these functional and structural deficits resulted in lower cross-modal matching abilities. Thus, neonatal unimodal experience during defined developmental stages is necessary for setting up the neuronal networks of multisensory processing. PMID:26600123

Syllable Transposition Effects in Korean Word Recognition

ERIC Educational Resources Information Center

Lee, Chang H.; Kwon, Youan; Kim, Kyungil; Rastle, Kathleen

2015-01-01

Research on the impact of letter transpositions in visual word recognition has yielded important clues about the nature of orthographic representations. This study investigated the impact of syllable transpositions on the recognition of Korean multisyllabic words. Results showed that rejection latencies in visual lexical decision for…

Effects of aging and involuntary capture of attention on event-related potentials associated with the processing of and the response to a target stimulus

PubMed Central

Cid-Fernández, Susana; Lindín, Mónica; Díaz, Fernando

2014-01-01

The main aim of the present study was to assess whether aging modulates the effects of involuntary capture of attention by novel stimuli on performance, and on event-related potentials (ERPs) associated with target processing (N2b and P3b) and subsequent response processes (stimulus-locked Lateralized Readiness Potential -sLRP- and response-locked Lateralized Readiness Potential -rLRP-). An auditory-visual distraction-attention task was performed by 77 healthy participants, divided into three age groups (Young: 21–29, Middle-aged: 51–64, Old: 65–84 years old). Participants were asked to attend to visual stimuli and to ignore auditory stimuli. Aging was associated with slowed reaction times, target stimulus processing in working memory (WM, longer N2b and P3b latencies) and selection and preparation of the motor response (longer sLRP and earlier rLRP onset latencies). In the novel relative to the standard condition we observed, in the three age groups: (1) a distraction effect, reflected in a slowing of reaction times, of stimuli categorization in WM (longer P3b latency), and of motor response selection (longer sLRP onset latency); (2) a facilitation effect on response preparation (later rLRP onset latency), and (3) an increase in arousal (larger amplitudes of all ERPs evaluated, except for N2b amplitude in the Old group). A distraction effect on the stimulus evaluation processes (longer N2b latency) were also observed, but only in middle-aged and old participants, indicating that the attentional capture slows the stimulus evaluation in WM from early ages (from 50 years onwards, without differences between middle-age and older adults), but not in young adults. PMID:25294999

Pattern Electroretinography and Visual Evoked Potentials Provide Clinical Evidence of CNS Modulation of High- and Low-Contrast VEP Latency in Glaucoma

PubMed Central

Sponsel, William E.; Johnson, Susan L.; Trevino, Rick; Gonzalez, Alberto; Groth, Sylvia L.; Majcher, Carolyn; Fulton, Diane C.; Reilly, Matthew A.

2017-01-01

Purpose Both pattern electroretinography (PERG) and visual evoked potentials (VEP) can be performed using low- (15%; Lc) and high- (85%; Hc) contrast gratings that may preferentially stimulate the magno- and parvocellular pathways. We observed that among glaucomatous patients showing only one VEP latency deficit per eye, there appeared to be a very strong tendency for an Hc delay in one eye and an Lc delay in the other. Methods Diopsys NOVA-LX system was used to measure VEP Hc and Lc latency among a clinical glaucoma population to find all individuals with either a single Hc or Lc latency abnormality in each eye (group 1), or with greater than 0 and less than 4 Hc or Lc VEP latency abnormalities in the two eyes (group 2) to determine whether a significant inverse correlation existed for these values in either group. Hc and Lc PERG data were also evaluated to assess associated retinal ganglion cell responses. Results A strong inverse correlation (P = 0.0000003) was observed between the Hc and Lc VEP latency values among the 64 eyes in group 1. Group 2 provided a comparable result (n = 143; 286 eyes; P = 0.0005). PERG (n = 81; 162 eyes) also showed strong bilateral symmetry for magnitude values (P < 0.0001 for both Lc and Hc in groups 1 and 2). Conclusions Bilateral retention of both low-resolution/high-speed and high-resolution/low-speed function may persist with both eyes open despite symmetrically pathologic retinal ganglion cell PERG waveform asynchrony for Hc and Lc stimuli in the paired eyes. Translational Relevance Clinical electrophysiology strongly suggests binocular compensation for dynamic dysfunction operates under central nervous system (CNS) control in glaucoma. PMID:29134137

Fast and Famous: Looking for the Fastest Speed at Which a Face Can be Recognized

PubMed Central

Barragan-Jason, Gladys; Besson, Gabriel; Ceccaldi, Mathieu; Barbeau, Emmanuel J.

2012-01-01

Face recognition is supposed to be fast. However, the actual speed at which faces can be recognized remains unknown. To address this issue, we report two experiments run with speed constraints. In both experiments, famous faces had to be recognized among unknown ones using a large set of stimuli to prevent pre-activation of features which would speed up recognition. In the first experiment (31 participants), recognition of famous faces was investigated using a rapid go/no-go task. In the second experiment, 101 participants performed a highly time constrained recognition task using the Speed and Accuracy Boosting procedure. Results indicate that the fastest speed at which a face can be recognized is around 360–390 ms. Such latencies are about 100 ms longer than the latencies recorded in similar tasks in which subjects have to detect faces among other stimuli. We discuss which model of activation of the visual ventral stream could account for such latencies. These latencies are not consistent with a purely feed-forward pass of activity throughout the visual ventral stream. An alternative is that face recognition relies on the core network underlying face processing identified in fMRI studies (OFA, FFA, and pSTS) and reentrant loops to refine face representation. However, the model of activation favored is that of an activation of the whole visual ventral stream up to anterior areas, such as the perirhinal cortex, combined with parallel and feed-back processes. Further studies are needed to assess which of these three models of activation can best account for face recognition. PMID:23460051

Relationship between selected orientation rest frame, circular vection and space motion sickness

NASA Technical Reports Server (NTRS)

Harm, D. L.; Parker, D. E.; Reschke, M. F.; Skinner, N. C.

1998-01-01

Space motion sickness (SMS) and spatial orientation and motion perception disturbances occur in 70-80% of astronauts. People select "rest frames" to create the subjective sense of spatial orientation. In microgravity, the astronaut's rest frame may be based on visual scene polarity cues and on the internal head and body z axis (vertical body axis). The data reported here address the following question: Can an astronaut's orientation rest frame be related and described by other variables including circular vection response latencies and space motion sickness? The astronaut's microgravity spatial orientation rest frames were determined from inflight and postflight verbal reports. Circular vection responses were elicited by rotating a virtual room continuously at 35 degrees/s in pitch, roll and yaw with respect to the astronaut. Latency to the onset of vection was recorded from the time the crew member opened their eyes to the onset of vection. The astronauts who used visual cues exhibited significantly shorter vection latencies than those who used internal z axis cues. A negative binomial regression model was used to represent the observed total SMS symptom scores for each subject for each flight day. Orientation reference type had a significant effect, resulting in an estimated three-fold increase in the expected motion sickness score on flight day 1 for astronauts who used visual cues. The results demonstrate meaningful classification of astronauts' rest frames and their relationships to sensitivity to circular vection and SMS. Thus, it may be possible to use vection latencies to predict SMS severity and duration.

The segment as the minimal planning unit in speech production: evidence based on absolute response latencies.

PubMed

Kawamoto, Alan H; Liu, Qiang; Lee, Ria J; Grebe, Patricia R

2014-01-01

A minimal amount of information about a word must be phonologically and phonetically encoded before a person can begin to utter that word. Most researchers assume that the minimum is the complete word or possibly the initial syllable. However, there is some evidence that the initial segment is sufficient based on longer durations when the initial segment is primed. In two experiments in which the initial segment of a monosyllabic word is primed or not primed, we present additional evidence based on very short absolute response times determined on the basis of acoustic and articulatory onset relative to presentation of the complete target. We argue that the previous failures to find very short absolute response times when the initial segment is primed are due in part to the exclusive use of acoustic onset as a measure of response latency, the exclusion of responses with very short acoustic latencies, the manner of articulation of the initial segment (i.e., plosive vs. nonplosive), and individual differences. Theoretical implications of the segment as the minimal planning unit are considered.

Intelligence and information processing during a visual search task in children: an event-related potential study.

PubMed

Zhang, Qiong; Shi, Jiannong; Luo, Yuejia; Zhao, Daheng; Yang, Jie

2006-05-15

To investigate the differences in event-related potential parameters related to children's intelligence, we selected 15 individuals from an experimental class of intellectually gifted children and 13 intellectually average children as control to finish three types of visual search tasks (Chinese words, English letters and Arabic numbers). We recorded the electroencephalogram and calculated the peak latencies and amplitudes. Our results suggest comparatively increased P3 amplitudes and shorter P3 latencies in brighter individuals than in less intelligent individuals, but this expected neural efficiency effect interacted with task content. The differences were explained by a more spatially and temporally coordinated neural network for more intelligent children.

Visually evoked responses in extrastriate area MT after lesions of striate cortex in early life.

PubMed

Yu, Hsin-Hao; Chaplin, Tristan A; Egan, Gregory W; Reser, David H; Worthy, Katrina H; Rosa, Marcello G P

2013-07-24

Lesions of striate cortex [primary visual cortex (V1)] in adult primates result in blindness. In contrast, V1 lesions in neonates typically allow much greater preservation of vision, including, in many human patients, conscious perception. It is presently unknown how this marked functional difference is related to physiological changes in cortical areas that are spared by the lesions. Here we report a study of the middle temporal area (MT) of adult marmoset monkeys that received unilateral V1 lesions within 6 weeks of birth. In contrast with observations after similar lesions in adult monkeys, we found that virtually all neurons in the region of MT that was deprived of V1 inputs showed robust responses to visual stimulation. These responses were very similar to those recorded in neurons with receptive fields outside the lesion projection zones in terms of firing rate, signal-to-noise ratio, and latency. In addition, the normal retinotopic organization of MT was maintained. Nonetheless, we found evidence of a very specific functional deficit: direction selectivity, a key physiological characteristic of MT that is known to be preserved in many cells after adult V1 lesions, was absent. These results demonstrate that lesion-induced reorganization of afferent pathways is sufficient to develop robust visual function in primate extrastriate cortex, highlighting a likely mechanism for the sparing of vision after neonatal V1 lesions. However, they also suggest that interactions with V1 in early postnatal life are critical for establishing stimulus selectivity in MT.

The Nature and Process of Development in Averaged Visually Evoked Potentials: Discussion on Pattern Structure.

ERIC Educational Resources Information Center

Izawa, Shuji; Mizutani, Tohru

This paper examines the development of visually evoked EEG patterns in retarded and normal subjects. The paper focuses on the averaged visually evoked potentials (AVEP) in the central and occipital regions of the brain in eyes closed and eyes open conditions. Wave pattern, amplitude, and latency are examined. The first section of the paper reviews…

Development of Visual Selection in 3- to 9-Month-Olds: Evidence from Saccades to Previously Ignored Locations

ERIC Educational Resources Information Center

Amso, Dima; Johnson, Scott P.

2008-01-01

We examined changes in the efficiency of visual selection over the first postnatal year with an adapted version of a "spatial negative priming" paradigm. In this task, when a previously ignored location becomes the target to be selected, responses to it are impaired, providing a measure of visual selection. Oculomotor latencies to target selection…

Visual motion direction is represented in population-level neural response as measured by magnetoencephalography.

PubMed

Kaneoke, Y; Urakawa, T; Kakigi, R

2009-05-19

We investigated whether direction information is represented in the population-level neural response evoked by the visual motion stimulus, as measured by magnetoencephalography. Coherent motions with varied speed, varied direction, and different coherence level were presented using random dot kinematography. Peak latency of responses to motion onset was inversely related to speed in all directions, as previously reported, but no significant effect of direction on latency changes was identified. Mutual information entropy (IE) calculated using four-direction response data increased significantly (>2.14) after motion onset in 41.3% of response data and maximum IE was distributed at approximately 20 ms after peak response latency. When response waveforms showing significant differences (by multivariate discriminant analysis) in distribution of the three waveform parameters (peak amplitude, peak latency, and 75% waveform width) with stimulus directions were analyzed, 87 waveform stimulus directions (80.6%) were correctly estimated using these parameters. Correct estimation rate was unaffected by stimulus speed, but was affected by coherence level, even though both speed and coherence affected response amplitude similarly. Our results indicate that speed and direction of stimulus motion are represented in the distinct properties of a response waveform, suggesting that the human brain processes speed and direction separately, at least in part.

Short latency compound action potentials from mammalian gravity receptor organs

NASA Technical Reports Server (NTRS)

Jones, T. A.; Jones, S. M.

1999-01-01

Gravity receptor function was characterized in four mammalian species using far-field vestibular evoked potentials (VsEPs). VsEPs are compound action potentials of the vestibular nerve and central relays that are elicited by linear acceleration ramps applied to the cranium. Rats, mice, guinea pigs, and gerbils were studied. In all species, response onset occurred within 1.5 ms of the stimulus onset. Responses persisted during intense (116 dBSPL) wide-band (50 to 50 inverted question mark omitted inverted question mark000 Hz) forward masking, whereas auditory responses to intense clicks (112 dBpeSPL) were eliminated under the same conditions. VsEPs remained after cochlear extirpation but were eliminated following bilateral labyrinthectomy. Responses included a series of positive and negative peaks that occurred within 8 ms of stimulus onset (range of means at +6 dBre: 1.0 g/ms: P1=908 to 1062 micros, N1=1342 to 1475 micros, P2=1632 to 1952 micros, N2=2038 to 2387 micros). Mean response amplitudes at +6 dBre: 1.0 g/ms ranged from 0.14 to 0.99 microV. VsEP input/output functions revealed latency slopes that varied across peaks and species ranging from -19 to -51 micros/dB. Amplitude-intensity slopes also varied ranging from 0.04 to 0.08 microV/dB for rats and mice. Latency values were comparable to those of birds although amplitudes were substantially smaller in mammals. VsEP threshold values were considerably higher in mammals compared to birds and ranged from -8.1 to -10.5 dBre 1.0 g/ms across species. These results support the hypothesis that mammalian gravity receptors are less sensitive to dynamic stimuli than are those of birds.

Should I stay or should I go? Attentional disengagement from visually unique and unexpected items at fixation.

PubMed

Brockmole, James R; Boot, Walter R

2009-06-01

Distinctive aspects of a scene can capture attention even when they are irrelevant to one's goals. The authors address whether visually unique, unexpected, but task-irrelevant features also tend to hold attention. Observers searched through displays in which the color of each item was irrelevant. At the start of search, all objects changed color. Critically, the foveated item changed to an unexpected color (it was novel), became a color singleton (it was unique), or both. Saccade latency revealed the time required to disengage overt attention from this object. Singletons resulted in longer latencies, but only if they were unexpected. Conversely, unexpected items only delayed disengagement if they were singletons. Thus, the time spent overtly attending to an object is determined, at least in part, by task-irrelevant stimulus properties, but this depends on the confluence of expectation and visual salience. (c) 2009 APA, all rights reserved.

A steady state visually evoked potential investigation of memory and ageing.

PubMed

Macpherson, Helen; Pipingas, Andrew; Silberstein, Richard

2009-04-01

Old age is generally accompanied by a decline in memory performance. Specifically, neuroimaging and electrophysiological studies have revealed that there are age-related changes in the neural correlates of episodic and working memory. This study investigated age-associated changes in the steady state visually evoked potential (SSVEP) amplitude and latency associated with memory performance. Participants were 15 older (59-67 years) and 14 younger (20-30 years) adults who performed an object working memory (OWM) task and a contextual recognition memory (CRM) task, whilst the SSVEP was recorded from 64 electrode sites. Retention of a single object in the low demand OWM task was characterised by smaller frontal SSVEP amplitude and latency differences in older adults than in younger adults, indicative of an age-associated reduction in neural processes. Recognition of visual images in the more difficult CRM task was accompanied by larger, more sustained SSVEP amplitude and latency decreases over temporal parietal regions in older adults. In contrast, the more transient, frontally mediated pattern of activity demonstrated by younger adults suggests that younger and older adults utilize different neural resources to perform recognition judgements. The results provide support for compensatory processes in the aging brain; at lower task demands, older adults demonstrate reduced neural activity, whereas at greater task demands neural activity is increased.

Reliability of VEP Recordings Using Chronically Implanted Screw Electrodes in Mice

PubMed Central

Makowiecki, Kalina; Garrett, Andrew; Clark, Vince; Graham, Stuart L.; Rodger, Jennifer

2015-01-01

Purpose: Visual evoked potentials (VEPs) are widely used to objectively assess visual system function in animal models of ophthalmological diseases. Although use of chronically implanted electrodes is common in longitudinal VEP studies using rodent models, reliability of recordings over time has not been assessed. We compared VEPs 1 and 7 days after electrode implantation in the adult mouse. We also examined stimulus-independent changes over time, by assessing electroencephalogram (EEG) power and approximate entropy of the EEG signal. Methods: Stainless steel screws (600-μm diameter) were implanted into the skull overlying the right visual cortex and the orbitofrontal cortex of adult mice (C57Bl/6J, n = 7). Animals were reanesthetized 1 and 7 days after implantation to record VEP responses (flashed gratings) and EEG activity. Brain sections were stained for glial activation (GFAP) and cell death (TUNEL). Results: Reliability analysis, using intraclass correlation coefficients, showed VEP recordings had high reliability within the same session, regardless of time after electrode implantation and peak latencies and approximate entropy of the EEG did not change significantly with time. However, there was poorer reliability between recordings obtained on different days, and a significant decrease in VEP amplitudes and EEG power. This amplitude decrease could be normalized by scaling to EEG power (within-subjects). Furthermore, glial activation was present at both time points but there was no evidence of cell death. Conclusions: These results indicate that VEP responses can be reliably recorded even after a relatively short recovery period but decrease response peak amplitude over time. Although scaling the VEP trace to EEG power normalized this decrease, our results highlight that time-dependent cortical excitability changes are an important consideration in longitudinal VEP studies. Translational Relevance: This study shows changes in VEP characteristics over time in chronically implanted mice. Thus, future preclinical longitudinal studies should consider time in addition to amplitude and latency when designing and interpreting research. PMID:25938003

Speed of feedforward and recurrent processing in multilayer networks of integrate-and-fire neurons.

PubMed

Panzeri, S; Rolls, E T; Battaglia, F; Lavis, R

2001-11-01

The speed of processing in the visual cortical areas can be fast, with for example the latency of neuronal responses increasing by only approximately 10 ms per area in the ventral visual system sequence V1 to V2 to V4 to inferior temporal visual cortex. This has led to the suggestion that rapid visual processing can only be based on the feedforward connections between cortical areas. To test this idea, we investigated the dynamics of information retrieval in multiple layer networks using a four-stage feedforward network modelled with continuous dynamics with integrate-and-fire neurons, and associative synaptic connections between stages with a synaptic time constant of 10 ms. Through the implementation of continuous dynamics, we found latency differences in information retrieval of only 5 ms per layer when local excitation was absent and processing was purely feedforward. However, information latency differences increased significantly when non-associative local excitation was included. We also found that local recurrent excitation through associatively modified synapses can contribute significantly to processing in as little as 15 ms per layer, including the feedforward and local feedback processing. Moreover, and in contrast to purely feed-forward processing, the contribution of local recurrent feedback was useful and approximately this rapid even when retrieval was made difficult by noise. These findings suggest that cortical information processing can benefit from recurrent circuits when the allowed processing time per cortical area is at least 15 ms long.

Multifocal blue-on-yellow visual evoked potentials in early glaucoma.

PubMed

Klistorner, Alexander; Graham, Stuart L; Martins, Alessandra; Grigg, John R; Arvind, Hemamalini; Kumar, Rajesh S; James, Andrew C; Billson, Francis A

2007-09-01

To determine the sensitivity and specificity of blue-on-yellow multifocal visual evoked potentials (mfVEPs) in early glaucoma. Cross-sectional study. Fifty patients with a confirmed diagnosis of early glaucoma and 60 normal participants. Black-and-white mfVEPs and blue-on-yellow mfVEPs were recorded using the Accumap version 2.0 (ObjectiVision Pty. Ltd., Sydney, Australia). All patients also underwent achromatic standard automated perimetry (SAP). Multifocal VEP amplitude and latency values in glaucoma patients were analyzed and compared with those of the normal controls. Based on the definition of visual field defect, in the group of glaucomatous eyes with SAP defects, amplitude of blue-on-yellow mfVEP was abnormal in all 64 cases (100% sensitivity), whereas black-and-white mfVEP missed 5 cases (92.2% sensitivity). Generally, larger scotomata were noted on blue-on-yellow mfVEP compared with black-and-white mfVEP for the same eyes. There was high topographic correspondence between SAP and amplitude of blue-on-yellow mfVEP and significant (P<0.0001) correlation between them (correlation coefficient, 0.73). Abnormal amplitude was detected in 3 of 60 eyes of control subjects (95% specificity). There was, however, no correlation between visual field defect and latency delay in glaucoma patients. Although there was a significant difference between averaged latency of control and glaucoma eyes, values considerably overlapped. The blue-on-yellow mfVEP is a sensitive and specific tool for detecting early glaucoma based on amplitude analysis.

Optimization of visual evoked potential (VEP) recording systems.

PubMed

Karanjia, Rustum; Brunet, Donald G; ten Hove, Martin W

2009-01-01

To explore the influence of environmental conditions on pattern visual evoked potential (VEP) recordings. Fourteen subjects with no known ocular pathology were recruited for the study. In an attempt to optimize the recording conditions, VEP recordings were performed in both the seated and recumbent positions. Comparisons were made between recordings using either LCD or CRT displays and recordings obtained in silence or with quiet background music. Paired recordings (in which only one variable was changed) were analyzed for changes in P100 latency, RMS noise, and variability. Baseline RMS noise demonstrated a significant decrease in the variability during the first 50msec accompanied by a 73% decrease in recording time for recumbent position when compared to the seated position (p<0.05). Visual evoked potentials recorded using LCD monitors demonstrated a significant increase in the P100 latency when compared to CRT recordings in the same subjects. The addition of background music did not affect the amount of RMS noise during the first 50msec of the recordings. This study demonstrates that the use of the recumbent position increases patient comfort and improves the signal to noise ratio. In contrast, the addition of background music to relax the patient did not improve the recording signal. Furthermore, the study illustrates the importance of avoiding low-contrast visual stimulation patterns obtained with LCD as they lead to higher latencies resulting in false positive recordings. These findings are important when establishing or modifying a pattern VEP recording protocol.

Unconscious cues bias first saccades in a free-saccade task.

PubMed

Huang, Yu-Feng; Tan, Edlyn Gui Fang; Soon, Chun Siong; Hsieh, Po-Jang

2014-10-01

Visual-spatial attention can be biased towards salient visual information without visual awareness. It is unclear, however, whether such bias can further influence free-choices such as saccades in a free viewing task. In our experiment, we presented visual cues below awareness threshold immediately before people made free saccades. Our results showed that masked cues could influence the direction and latency of the first free saccade, suggesting that salient visual information can unconsciously influence free actions. Copyright © 2014 Elsevier Inc. All rights reserved.

Visual Attention and Perception in Three-Dimensional Space

DTIC Science & Technology

1992-01-01

Hughes & Zimba , 1987). Themarrows’ in the near-far condition (Fig. 1c) were actually wedges that pointed either toward or away from the subject, with their...1992). The increase in saccade latencies in the lower visual field. Perception and Psychophysics (in press). Hughes, H. C., & Zimba , L D. (1987

Intralimb and Interlimb Cutaneous Reflexes during Locomotion in the Intact Cat.

PubMed

Hurteau, Marie-France; Thibaudier, Yann; Dambreville, Charline; Danner, Simon M; Rybak, Ilya A; Frigon, Alain

2018-04-25

When the foot contacts an obstacle during locomotion, cutaneous inputs activate spinal circuits to ensure dynamic balance and forward progression. In quadrupeds, this requires coordinated reflex responses between the four limbs. Here, we investigated the patterns and phasic modulation of cutaneous reflexes in forelimb and hindlimb muscles evoked by inputs from all four limbs. Five female cats were implanted to record muscle activity and to stimulate the superficial peroneal and superficial radial nerves during locomotion. Stimulating these nerves evoked short-, mid-, and longer-latency excitatory and/or inhibitory responses in all four limbs that were phase-dependent. The largest responses were generally observed during the peak activity of the muscle. Cutaneous reflexes during mid-swing were consistent with flexion of the homonymous limb and accompanied by modification of the stance phases of the other three limbs, by coactivating flexors and extensors and/or by delaying push-off. Cutaneous reflexes during mid-stance were consistent with stabilizing the homonymous limb by delaying and then facilitating its push-off and modifying the support phases of the homolateral and diagonal limbs, characterized by coactivating flexors and extensors, reinforcing extensor activity and/or delaying push-off. The shortest latencies of homolateral and diagonal responses were consistent with fast-conducting disynaptic or trisynaptic pathways. Descending homolateral and diagonal pathways from the forelimbs to the hindlimbs had a higher probability of eliciting responses compared with ascending pathways from the hindlimbs to the forelimbs. Thus, in quadrupeds, intralimb and interlimb reflexes activated by cutaneous inputs ensure dynamic coordination of the four limbs, producing a whole-body response. SIGNIFICANCE STATEMENT The skin contains receptors that, when activated, send inputs to spinal circuits, signaling a perturbation. Rapid responses, or reflexes, in muscles of the contacted limb and opposite homologous limb help maintain balance and forward progression. Here, we investigated reflexes during quadrupedal locomotion in the cat by electrically stimulating cutaneous nerves in each of the four limbs. Functionally, responses appear to modify the trajectory or stabilize the movement of the stimulated limb while modifying the support phase of the other limbs. Reflexes between limbs are mediated by fast-conducting pathways that involve excitatory and inhibitory circuits controlling each limb. The comparatively stronger descending pathways from cervical to lumbar circuits controlling the forelimbs and hindlimbs, respectively, could serve a protective function. Copyright © 2018 the authors 0270-6474/18/384104-19$15.00/0.

Selective Defects of Visual Tracking in Progressive Supranuclear Palsy (PSP): Implications for mechanisms of motion vision

PubMed Central

Joshi, Anand C.; Riley, David E.; Mustari, Michael J.; Cohen, Mark L.; Leigh, R. John

2010-01-01

Smooth ocular tracking of a moving visual stimulus comprises a range of responses that encompass the ocular following response (OFR), a pre-attentive, short-latency mechanism, and smooth pursuit, which directs the retinal fovea at the moving stimulus. In order to determine how interdependent these two forms of ocular tracking are, we studied vertical OFR in progressive supranuclear palsy (PSP), a parkinsonian disorder in which vertical smooth pursuit is known to be impaired. We measured eye movements of 9 patients with PSP and 12 healthy control subjects. Subjects viewed vertically moving sine-wave gratings that had a temporal frequency of 16.7 Hz, contrast of 32%, and spatial frequencies of 0.17, 0.27 or 0.44 cycles/°. We measured OFR amplitude as change in eye position in the 70 – 150 ms, open-loop interval following stimulus onset. Vertical smooth pursuit was studied as subjects attempted to track a 0.27 cycles/° grating moving sinusoidally through several cycles at frequencies between 0.1 – 2.5 Hz. We found that OFR amplitude, and its dependence on spatial frequency, was similar in PSP patients (group mean 0.10°) and control subjects (0.11°), but the latency to onset of OFR was greater for PSP patients (group mean 99 ms) than control subjects (90 ms). When OFR amplitude was re-measured, taking into account the increased latency in PSP patients, there was still no difference from control subjects. We confirmed that smooth pursuit was consistently impaired in PSP; group mean tracking gain at 0.7 Hz was 0.29 for PSP patients and 0.63 for controls. Neither PSP patients nor control subjects showed any correlation between OFR amplitude and smooth-pursuit gain. We propose that OFR is spared because it is generated by low-level motion processing that is dependent on posterior cerebral cortex, which is less affected in PSP. Conversely, smooth pursuit depends more on projections from frontal cortex to the pontine nuclei, both of which are involved in PSP. The accessory optic pathway, which is heavily involved in PSP, seems unlikely to contribute to the OFR in humans. PMID:20123108

Industrial WSN Based on IR-UWB and a Low-Latency MAC Protocol

NASA Astrophysics Data System (ADS)

Reinhold, Rafael; Underberg, Lisa; Wulf, Armin; Kays, Ruediger

2016-07-01

Wireless sensor networks for industrial communication require high reliability and low latency. As current wireless sensor networks do not entirely meet these requirements, novel system approaches need to be developed. Since ultra wideband communication systems seem to be a promising approach, this paper evaluates the performance of the IEEE 802.15.4 impulse-radio ultra-wideband physical layer and the IEEE 802.15.4 Low Latency Deterministic Network (LLDN) MAC for industrial applications. Novel approaches and system adaptions are proposed to meet the application requirements. In this regard, a synchronization approach based on circular average magnitude difference functions (CAMDF) and on a clean template (CT) is presented for the correlation receiver. An adapted MAC protocol titled aggregated low latency (ALL) MAC is proposed to significantly reduce the resulting latency. Based on the system proposals, a hardware prototype has been developed, which proves the feasibility of the system and visualizes the real-time performance of the MAC protocol.

Human short-latency ocular vergence responses produced by interocular velocity differences

PubMed Central

Sheliga, B. M.; Quaia, C.; FitzGibbon, E. J.; Cumming, B. G.

2016-01-01

We studied human short-latency vergence eye movements to a novel stimulus that produces interocular velocity differences without a changing disparity signal. Sinusoidal luminance gratings moved in opposite directions (left vs. right; up vs. down) in the two eyes. The grating seen by each eye underwent ¼-wavelength shifts with each image update. This arrangement eliminated changing disparity cues, since the phase difference between the eyes alternated between 0° and 180°. We nevertheless observed robust short-latency vergence responses (VRs), whose sign was consistent with the interocular velocity differences (IOVDs), indicating that the IOVD cue in isolation can evoke short-latency VRs. The IOVD cue was effective only when the images seen by the two eyes overlapped in space. We observed equally robust VRs for opposite horizontal motions (left in one eye, right in the other) and opposite vertical motions (up in one eye, down in the other). Whereas the former are naturally generated by objects moving in depth, the latter are not part of our normal experience. To our knowledge, this is the first demonstration of a behavioral consequence of vertical IOVD. This may reflect the fact that some neurons in area MT are sensitive to these motion signals (Czuba, Huk, Cormack, & Kohn, 2014). VRs were the strongest for spatial frequencies in the range of 0.35–1 c/°, much higher than the optimal spatial frequencies for evoking ocular-following responses observed during frontoparallel motion. This suggests that the two motion signals are detected by different neuronal populations. We also produced IOVD using moving uncorrelated one-dimensional white-noise stimuli. In this case the most effective stimuli have low speed, as predicted if the drive originates in neurons tuned to high spatial frequencies (Sheliga, Quaia, FitzGibbon, & Cumming, 2016). PMID:27548089

The processing of images of biological threats in visual short-term memory.

PubMed

Quinlan, Philip T; Yue, Yue; Cohen, Dale J

2017-08-30

The idea that there is enhanced memory for negatively, emotionally charged pictures was examined. Performance was measured under rapid, serial visual presentation (RSVP) conditions in which, on every trial, a sequence of six photo-images was presented. Briefly after the offset of the sequence, two alternative images (a target and a foil) were presented and participants attempted to choose which image had occurred in the sequence. Images were of threatening and non-threatening cats and dogs. The target depicted either an animal expressing an emotion distinct from the other images, or the sequences contained only images depicting the same emotional valence. Enhanced memory was found for targets that differed in emotional valence from the other sequence images, compared to targets that expressed the same emotional valence. Further controls in stimulus selection were then introduced and the same emotional distinctiveness effect obtained. In ruling out possible visual and attentional accounts of the data, an informal dual route topic model is discussed. This places emphasis on how visual short-term memory reveals a sensitivity to the emotional content of the input as it unfolds over time. Items that present with a distinctive emotional content stand out in memory. © 2017 The Author(s).

Throwing out the rules: anticipatory alpha-band oscillatory attention mechanisms during task-set reconfigurations.

PubMed

Foxe, John J; Murphy, Jeremy W; De Sanctis, Pierfilippo

2014-06-01

We assessed the role of alpha-band oscillatory activity during a task-switching design that required participants to switch between an auditory and a visual task, while task-relevant audiovisual inputs were simultaneously presented. Instructional cues informed participants which task to perform on a given trial and we assessed alpha-band power in the short 1.35-s period intervening between the cue and the task-imperative stimuli, on the premise that attentional biasing mechanisms would be deployed to resolve competition between the auditory and visual inputs. Prior work had shown that alpha-band activity was differentially deployed depending on the modality of the cued task. Here, we asked whether this activity would, in turn, be differentially deployed depending on whether participants had just made a switch of task or were being asked to simply repeat the task. It is well established that performance speed and accuracy are poorer on switch than on repeat trials. Here, however, the use of instructional cues completely mitigated these classic switch-costs. Measures of alpha-band synchronisation and desynchronisation showed that there was indeed greater and earlier differential deployment of alpha-band activity on switch vs. repeat trials. Contrary to our hypothesis, this differential effect was entirely due to changes in the amount of desynchronisation observed during switch and repeat trials of the visual task, with more desynchronisation over both posterior and frontal scalp regions during switch-visual trials. These data imply that particularly vigorous, and essentially fully effective, anticipatory biasing mechanisms resolved the competition between competing auditory and visual inputs when a rapid switch of task was required. © 2014 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

Alview: Portable Software for Viewing Sequence Reads in BAM Formatted Files.

PubMed

Finney, Richard P; Chen, Qing-Rong; Nguyen, Cu V; Hsu, Chih Hao; Yan, Chunhua; Hu, Ying; Abawi, Massih; Bian, Xiaopeng; Meerzaman, Daoud M

2015-01-01

The name Alview is a contraction of the term Alignment Viewer. Alview is a compiled to native architecture software tool for visualizing the alignment of sequencing data. Inputs are files of short-read sequences aligned to a reference genome in the SAM/BAM format and files containing reference genome data. Outputs are visualizations of these aligned short reads. Alview is written in portable C with optional graphical user interface (GUI) code written in C, C++, and Objective-C. The application can run in three different ways: as a web server, as a command line tool, or as a native, GUI program. Alview is compatible with Microsoft Windows, Linux, and Apple OS X. It is available as a web demo at https://cgwb.nci.nih.gov/cgi-bin/alview. The source code and Windows/Mac/Linux executables are available via https://github.com/NCIP/alview.

Visual short-term memory load modulates the early attention and perception of task-irrelevant emotional faces

PubMed Central

Yang, Ping; Wang, Min; Jin, Zhenlan; Li, Ling

2015-01-01

The ability to focus on task-relevant information, while suppressing distraction, is critical for human cognition and behavior. Using a delayed-match-to-sample (DMS) task, we investigated the effects of emotional face distractors (positive, negative, and neutral faces) on early and late phases of visual short-term memory (VSTM) maintenance intervals, using low and high VSTM loads. Behavioral results showed decreased accuracy and delayed reaction times (RTs) for high vs. low VSTM load. Event-related potentials (ERPs) showed enhanced frontal N1 and occipital P1 amplitudes for negative faces vs. neutral or positive faces, implying rapid attentional alerting effects and early perceptual processing of negative distractors. However, high VSTM load appeared to inhibit face processing in general, showing decreased N1 amplitudes and delayed P1 latencies. An inverse correlation between the N1 activation difference (high-load minus low-load) and RT costs (high-load minus low-load) was found at left frontal areas when viewing negative distractors, suggesting that the greater the inhibition the lower the RT cost for negative faces. Emotional interference effect was not found in the late VSTM-related parietal P300, frontal positive slow wave (PSW) and occipital negative slow wave (NSW) components. In general, our findings suggest that the VSTM load modulates the early attention and perception of emotional distractors. PMID:26388763

Visual Working Memory Enhances the Neural Response to Matching Visual Input.

PubMed

Gayet, Surya; Guggenmos, Matthias; Christophel, Thomas B; Haynes, John-Dylan; Paffen, Chris L E; Van der Stigchel, Stefan; Sterzer, Philipp

2017-07-12

Visual working memory (VWM) is used to maintain visual information available for subsequent goal-directed behavior. The content of VWM has been shown to affect the behavioral response to concurrent visual input, suggesting that visual representations originating from VWM and from sensory input draw upon a shared neural substrate (i.e., a sensory recruitment stance on VWM storage). Here, we hypothesized that visual information maintained in VWM would enhance the neural response to concurrent visual input that matches the content of VWM. To test this hypothesis, we measured fMRI BOLD responses to task-irrelevant stimuli acquired from 15 human participants (three males) performing a concurrent delayed match-to-sample task. In this task, observers were sequentially presented with two shape stimuli and a retro-cue indicating which of the two shapes should be memorized for subsequent recognition. During the retention interval, a task-irrelevant shape (the probe) was briefly presented in the peripheral visual field, which could either match or mismatch the shape category of the memorized stimulus. We show that this probe stimulus elicited a stronger BOLD response, and allowed for increased shape-classification performance, when it matched rather than mismatched the concurrently memorized content, despite identical visual stimulation. Our results demonstrate that VWM enhances the neural response to concurrent visual input in a content-specific way. This finding is consistent with the view that neural populations involved in sensory processing are recruited for VWM storage, and it provides a common explanation for a plethora of behavioral studies in which VWM-matching visual input elicits a stronger behavioral and perceptual response. SIGNIFICANCE STATEMENT Humans heavily rely on visual information to interact with their environment and frequently must memorize such information for later use. Visual working memory allows for maintaining such visual information in the mind's eye after termination of its retinal input. It is hypothesized that information maintained in visual working memory relies on the same neural populations that process visual input. Accordingly, the content of visual working memory is known to affect our conscious perception of concurrent visual input. Here, we demonstrate for the first time that visual input elicits an enhanced neural response when it matches the content of visual working memory, both in terms of signal strength and information content. Copyright © 2017 the authors 0270-6474/17/376638-10$15.00/0.

Psychophysical scaling of circular vection (CV) produced by optokinetic (OKN) motion: individual differences and effects of practice.

PubMed

Kennedy, R S; Hettinger, L J; Harm, D L; Ordy, J M; Dunlap, W P

1996-01-01

Vection (V) refers to the compelling visual illusion of self-motion experienced by stationary individuals when viewing moving visual surrounds. The phenomenon is of theoretical interest because of its relevance for understanding the neural basis of ordinary self-motion perception, and of practical importance because it is the experience that makes simulation, virtual reality displays, and entertainment devices more vicarious. This experiment was performed to address whether an optokinetically induced vection illusion exhibits monotonic and stable psychometric properties and whether individuals differ reliably in these (V) perceptions. Subjects were exposed to varying velocities of the circular vection (CV) display in an optokinetic (OKN) drum 2 meters in diameter in 5 one-hour daily sessions extending over a 1 week period. For grouped data, psychophysical scalings of velocity estimates showed that exponents in a Stevens' type power function were essentially linear (slope = 0.95) and largely stable over sessions. Latencies were slightly longer for the slowest and fastest induction stimuli, and the trend over sessions for average latency was longer as a function of practice implying time course adaptation effects. Test-retest reliabilities for individual slope and intercept measures were moderately strong (r = 0.45) and showed no evidence of superdiagonal form. This implies stability of the individual circularvection (CV) sensitivities. Because the individual CV scores were stable, reliabilities were improved by averaging 4 sessions in order to provide a stronger retest reliability (r = 0.80). Individual latency responses were highly reliable (r = 0.80). Mean CV latency and motion sickness symptoms were greater in males than in females. These individual differences in CV could be predictive of other outcomes, such as susceptibility to disorientation or motion sickness, and for CNS localization of visual-vestibular interactions in the experience of self-motion.

Working-memory capacity predicts the executive control of visual search among distractors: the influences of sustained and selective attention.

PubMed

Poole, Bradley J; Kane, Michael J

2009-07-01

Variation in working-memory capacity (WMC) predicts individual differences in only some attention-control capabilities. Whereas higher WMC subjects outperform lower WMC subjects in tasks requiring the restraint of prepotent but inappropriate responses, and the constraint of attentional focus to target stimuli against distractors, they do not differ in prototypical visual-search tasks, even those that yield steep search slopes and engender top-down control. The present three experiments tested whether WMC, as measured by complex memory span tasks, would predict search latencies when the 1-8 target locations to be searched appeared alone, versus appearing among distractor locations to be ignored, with the latter requiring selective attentional focus. Subjects viewed target-location cues and then fixated on those locations over either long (1,500-1,550 ms) or short (300 ms) delays. Higher WMC subjects identified targets faster than did lower WMC subjects only in the presence of distractors and only over long fixation delays. WMC thus appears to affect subjects' ability to maintain a constrained attentional focus over time.

Time-based Reconstruction of Free-streaming Data in CBM

NASA Astrophysics Data System (ADS)

Akishina, Valentina; Kisel, Ivan; Vassiliev, Iouri; Zyzak, Maksym

2018-02-01

Traditional latency-limited trigger architectures typical for conventional experiments are inapplicable for the CBM experiment. Instead, CBM will ship and collect time-stamped data into a readout buffer in a form of a time-slice of a certain length and deliver it to a large computer farm, where online event reconstruction and selection will be performed. Grouping measurements into physical collisions must be performed in software and requires reconstruction not only in space, but also in time, the so-called 4-dimensional track reconstruction and event building. The tracks, reconstructed with 4D Cellular Automaton track finder, are combined into event-corresponding clusters according to the estimated time in the target position and the errors, obtained with the Kalman Filter method. The reconstructed events are given as inputs to the KF Particle Finder package for short-lived particle reconstruction. The results of time-based reconstruction of simulated collisions in CBM are presented and discussed in details.

Accommodation and vergence latencies in human infants

PubMed Central

Tondel, Grazyna M.; Candy, T. Rowan

2008-01-01

Purpose Achieving simultaneous single and clear visual experience during postnatal development depends on the temporal relationship between accommodation and vergence, in addition to their accuracies. This study was designed to examine one component of the dynamic relationship, the latencies of the responses. Methods Infants and adults were tested in three conditions i) Binocular viewing of a target moving in depth at 5cm/s (closed loop) ii) monocular viewing of the same target (vergence open loop) iii) binocular viewing of a low spatial frequency Difference of Gaussian target during a prism induced step change in retinal disparity (accommodation open loop). Results There was a significant correlation between accommodation and vergence latencies in binocular conditions for infants from 7 to 23 weeks of age. Some of the infants, as young as 7 or 8 weeks, generated adult-like latencies of less than 0.5 s. Latencies in the vergence open loop and accommodation open loop conditions tended to be shorter for the stimulated system than the open loop system in both cases, and all latencies were typically less than 2 seconds across the infant age range. Conclusions Many infants between 7 and 23 weeks of age were able to generate accommodation and vergence responses with latencies of less than a second in full binocular closed loop conditions. The correlation between the latencies in the two systems suggests that they are limited by related factors from the earliest ages tested. PMID:18199466

Accommodation and vergence latencies in human infants.

PubMed

Tondel, Grazyna M; Candy, T Rowan

2008-02-01

Achieving simultaneous single and clear visual experience during postnatal development depends on the temporal relationship between accommodation and vergence, in addition to their accuracies. This study was designed to examine one component of the dynamic relationship, the latencies of the responses. Infants and adults were tested in three conditions (i) binocular viewing of a target moving in depth at 5 cm/s (closed loop) (ii) monocular viewing of the same target (vergence open loop) (iii) binocular viewing of a low spatial frequency Difference of Gaussian target during a prism induced step change in retinal disparity (accommodation open loop). There was a significant correlation between accommodation and vergence latencies in binocular conditions for infants from 7 to 23 weeks of age. Some of the infants, as young as 7 or 8 weeks, generated adult-like latencies of less than 0.5 s. Latencies in the vergence open loop and accommodation open loop conditions tended to be shorter for the stimulated system than the open loop system in both cases, and all latencies were typically less than 2 s across the infant age range. Many infants between 7 and 23 weeks of age were able to generate accommodation and vergence responses with latencies of less than a second in full binocular closed loop conditions. The correlation between the latencies in the two systems suggests that they are limited by related factors from the earliest ages tested.

Ultra-fast ipsilateral DPOAE adaptation not modulated by attention?

NASA Astrophysics Data System (ADS)

Dalhoff, Ernst; Zelle, Dennis; Gummer, Anthony W.

2018-05-01

Efferent stimulation of outer hair cells is supposed to attenuate cochlear amplification of sound waves and is accompanied by reduced DPOAE amplitudes. Recently, a method using two subsequent f2 pulses during presentation of a longer f1 pulse was introduced to measure fast ipsilateral adaptation effects on separated DPOAE components. Compensating primary-tone onsets for their latencies at the f2-tonotopic place, the average adaptation measured in four normal-hearing subjects was 5.0 dB with a time constant below 5 ms. In the present study, two experiments were performed to determine the origin of this ultra-fast ipsilateral adaptation effect. The first experiment measured ultra-fast ipsilateral adaptation using a two-pulse paradigm at three frequencies in the four subjects, while controlling for visual attention of the subjects. The other experiment also controlled for visual attention, but utilized a sequence of f2 short pulses in the presence of a continuous f1 tone to sample ipsilateral adaptation effects with longer time constants in eight subjects. In the first experiment, no significant change in the ultra-fast adaptation between non-directed attention and visual attention could be detected. In contrast, the second experiment revealed significant changes in the magnitude of the slower ipsilateral adaptation in the visual-attention condition. In conclusion, the lack of an attentional influence indicates that the ultra-fast ipsilateral DPOAE adaptation is not solely mediated by the medial olivocochlear reflex.

A versatile stereoscopic visual display system for vestibular and oculomotor research.

PubMed

Kramer, P D; Roberts, D C; Shelhamer, M; Zee, D S

1998-01-01

Testing of the vestibular system requires a vestibular stimulus (motion) and/or a visual stimulus. We have developed a versatile, low cost, stereoscopic visual display system, using "virtual reality" (VR) technology. The display system can produce images for each eye that correspond to targets at any virtual distance relative to the subject, and so require the appropriate ocular vergence. We elicited smooth pursuit, "stare" optokinetic nystagmus (OKN) and after-nystagmus (OKAN), vergence for targets at various distances, and short-term adaptation of the vestibulo-ocular reflex (VOR), using both conventional methods and the stereoscopic display. Pursuit, OKN, and OKAN were comparable with both methods. When used with a vestibular stimulus, VR induced appropriate adaptive changes of the phase and gain of the angular VOR. In addition, using the VR display system and a human linear acceleration sled, we adapted the phase of the linear VOR. The VR-based stimulus system not only offers an alternative to more cumbersome means of stimulating the visual system in vestibular experiments, it also can produce visual stimuli that would otherwise be impractical or impossible. Our techniques provide images without the latencies encountered in most VR systems. Its inherent versatility allows it to be useful in several different types of experiments, and because it is software driven it can be quickly adapted to provide a new stimulus. These two factors allow VR to provide considerable savings in time and money, as well as flexibility in developing experimental paradigms.

Planning in sentence production: Evidence for the phrase as a default planning scope

PubMed Central

Martin, Randi C.; Crowther, Jason E.; Knight, Meredith; Tamborello, Franklin P.; Yang, Chin-Lung

2010-01-01

Controversy remains as to the scope of advanced planning in language production. Smith and Wheeldon (1999) found significantly longer onset latencies when subjects described moving picture displays by producing sentences beginning with a complex noun phrase than for matched sentences beginning with a simple noun phrase. While these findings are consistent with a phrasal scope of planning, they might also be explained on the basis of: 1) greater retrieval fluency for the second content word in the simple initial noun phrase sentences and 2) visual grouping factors. In Experiments 1 and 2, retrieval fluency for the second content word was equated for the complex and simple initial noun phrase conditions. Experiments 3 and 4 addressed the visual grouping hypothesis by using stationary displays and by comparing onset latencies for the same display for sentence and list productions. Longer onset latencies for the sentences beginning with a complex noun phrase were obtained in all experiments, supporting the phrasal scope of planning hypothesis. The results indicate that in speech, as in other motor production domains, planning occurs beyond the minimal production unit. PMID:20501338

Kinematic/Dynamic Characteristics for Visual and Kinesthetic Virtual Environments

NASA Technical Reports Server (NTRS)

Bortolussi, Michael R. (Compiler); Adelstein, B. D.; Gold, Miriam

1996-01-01

Work was carried out on two topics of principal importance to current progress in virtual environment research at NASA Ames and elsewhere. The first topic was directed at maximizing the temporal dynamic response of visually presented Virtual Environments (VEs) through reorganization and optimization of system hardware and software. The final results of this portion of the work was a VE system in the Advanced Display and Spatial Perception Laboratory at NASA Ames capable of updating at 60 Hz (the maximum hardware refresh rate) with latencies approaching 30 msec. In the course of achieving this system performance, specialized hardware and software tools for measurement of VE latency and analytic models correlating update rate and latency for different system configurations were developed. The second area of activity was the preliminary development and analysis of a novel kinematic architecture for three Degree Of Freedom (DOF) haptic interfaces--devices that provide force feedback for manipulative interaction with virtual and remote environments. An invention disclosure was filed on this work and a patent application is being pursued by NASA Ames. Activities in these two areas are expanded upon below.

Event-related potentials in impulsively aggressive juveniles: a retrospective chart-review study.

PubMed

Fisher, William; Ceballos, Natalie; Matthews, Dan; Fisher, Larry

2011-05-30

The assessment, treatment and management of aggressive youth represent a major clinical challenge facing pediatric mental health professionals today. Although a number of studies have examined physiological differences among aggressive patients vs. controls, the current literature lacks a comprehensive examination of the electroencephalographic activity of impulsively aggressive juveniles. The current study was designed to fill this void in the literature via a retrospective chart review of 80 male and female juveniles undergoing inpatient treatment for pathologically impulsive aggression. Clinical reports for mid- and late-latency event-related potentials (ERPs) were examined to determine their correlations with aggression characteristics, as well as any differential predictive utility of hemispheric differences and auditory vs. visual potentials. Results indicated that decrements of mid-latency potentials and ERPs evoked by auditory stimuli (vs. late-latency components and visual ERPs) were more highly predictive of aggressive behavior. No significant hemispheric differences were noted. Taken together, these results have theoretical significance for the etiology of impulsive aggression, and perhaps also clinical relevance for the treatment of this condition. Copyright © 2011 Elsevier Ltd. All rights reserved.

Fast counting electronics for neutron coincidence counting

DOEpatents

Swansen, James E.

1987-01-01

An amplifier-discriminator is tailored to output a very short pulse upon an above-threshold input from a detector which may be a .sup.3 He detector. The short pulse output is stretched and energizes a light emitting diode (LED) to provide a visual output of operation and pulse detection. The short pulse is further fed to a digital section for processing and possible ORing with other like generated pulses. Finally, the output (or ORed output ) is fed to a derandomizing buffer which converts the rapidly and randomly occurring pulses into synchronized and periodically spaced-apart pulses for the accurate counting thereof. Provision is also made for the internal and external disabling of each individual channel of amplifier-discriminators in an ORed plurality of same.

Fast counting electronics for neutron coincidence counting

DOEpatents

Swansen, J.E.

1985-03-05

An amplifier-discriminator is tailored to output a very short pulse upon an above-threshold input from a detector which may be a /sup 3/He detector. The short pulse output is stretched and energizes a light emitting diode (LED) to provide a visual output of operation and pulse detection. The short pulse is further fed to a digital section for processing and possible ORing with other like generated pulses. Finally, the output (or ORed output) is fed to a derandomizing buffer which converts the rapidly and randomly occurring pulses into synchronized and periodically spaced-apart pulses for the accurate counting thereof. Provision is also made for the internal and external disabling of each individual channel of amplifier-discriminators in an ORed plurality of same.

[Pattern-reversal electroretinogram (PERG): a normative study in adults].

PubMed

Alves, Letícia Dourado; Berezovsky, Adriana; Sacai, Paula Yuri; Pereira, Josenilson Martins; Salomão, Solange Rios

2010-01-01

To determine normative values for pattern-reversal electroretinogram (PERG) in healthy adult volunteers according to the standard protocol recommended by the International Society for Clinical Electrophysiology of Vision-ISCEV. Participants were 30 healthy volunteers (15 males) with ages from 18 to 61 years (mean= 30.8 +/- 8.7 yrs.; median= 29.5 yrs). Inclusion criteria were: visual acuity of 0.0 logMAR (20/20 Snellen) in each eye, absence of visual complaints, absence of media opacities, negative history for ocular or neurological diseases, negative family history for ocular and informed consent. PERG was recorded from each eye in a darkened room at 1 m from a high resolution display monitor. Stimuli were monochromatic checkerboards subtending 60, 15 e 7.5 minutes of visual angle reversing at 1.9 Hz. Responses were obtained from modified disposable fiber electrodes developed at UNIFESP. Latency (ms) for N35, P50 and N95 components as well as peak-to-peak amplitudes (microV) for N35-P50 and P50-N95 were determined. For normative values only one randomly chosen eye was included. Normal limits were calculated as 97.5% percentiles for latency and 2.5% percentile for amplitudes for each stimulus size. Normal limits for N35, P50 and N95 latencies for 60', 15' and 7.5' stimuli were respectively: N35 - 40.1; 39.9 and 41.3 ms; P50 - 60.5; 64.4 and 65.6 ms and N95 - 103.4; 104.6 and 104.6 ms. For amplitude the normative values for N35-P50 and P50-N95 for 60', 15' and 7.5' were respectively: N35-P50 - 1.7; 1.6 and 0.9 microV; P50-N95 - 3.8; 2.8 and 1.5 microV. No gender differences were found either for latency or for amplitude in the three stimulus sizes. There was no correlation between PERG latency and amplitude with age, except for P50 amplitude for stimulus 15'(r=0.39; P=0.035). Normative values were determined for PERG parameters of amplitude and latency for three stimulus sizes. These parameters are important for evaluating the normal functioning of retinal ganglion cells and the macula. The normative values obtained in this study are comparable to previous studies in the literature.

Neighborhood Effects on Nonword Visual Processing in a Language with Shallow Orthography

ERIC Educational Resources Information Center

Arduino, Lisa S.; Burani, Cristina

2004-01-01

Neighborhood size and neighborhood frequency were orthogonally varied in two experiments on Italian nonwords. In Experiment 1, an inhibitory effect of neighborhood frequency on visual lexical decision was found: The presence of one high-frequency neighbor increased response latencies and error rates to nonwords. By contrast, no effect of…

Properties and connections of cat fastigiospinal neurons.

PubMed

Wilson, V J; Uchino, Y; Maunz, R A; Susswein, A; Fukushima, K

1978-05-12

1. Neurons in the cat fastigial nucleus that project to the upper cervical spinal segments (fastigiospinal neurons) were fired by antidromic stimulation of the contralateral spinal cord. Dye ejection from the recording electrode was used to show that most neurons were in the rostral half of the fastigial nucleus. 2. Fastigiospinal neurons can be excited and/or inhibited by stimulation of forelimb and hindlimb nerves and by stimulation of the vestibular nerve. These inputs converge on many neurons. 3. Antidromic microstimulation was used to trace fastigiospinal axons to the vicinity of motor nuclei in in C2-C3. 4. The rostral fastigial nucleus was stimulated in preparations with the medial longitudinal fasciculus transected by a wide lesion that impinged on the medial reticular formation in the caudal medulla, to eliminate some potential axon reflexes. Short-latency EPSPs were recorded in some trapezius and biventer-cervicis motoneurons. In many cases there was little or no occlusion between these EPSPs and others evoked by stimulation of the vestibular nerve ipsilateral to the motoneurons. 5. Movement of the stimulating electrode and placement of this electrode lateral to the fastigial nucleus show that the zone from which low threshold EPSPs can be evoked is localized. 6. Latency measurements and lack of temporal facilitation with double shocks suggest that the EPSPs are monosynaptic. The evidence suggests that they are caused by fastigiospinal fibers terminating on motoneurons.

Simulation Based Studies of Low Latency Teleoperations for NASA Exploration Missions

NASA Technical Reports Server (NTRS)

Gernhardt, Michael L.; Crues, Edwin Z.; Bielski, Paul; Dexter, Dan; Litaker, Harry L.; Chappell, Steven P.; Beaton, Kara H.; Bekdash, Omar S.

2017-01-01

Human exploration of Mars will involve both crewed and robotic systems. Many mission concepts involve the deployment and assembly of mission support assets prior to crew arrival on the surface. Some of these deployment and assembly activities will be performed autonomously while others will be performed using teleoperations. However, significant communications latencies between the Earth and Mars make teleoperations challenging. Alternatively, low latency teleoperations are possible from locations in Mars orbit like Mars' moons Phobos and Deimos. To explore these latency opportunities, NASA is conducting a series of studies to investigate the effects of latency on telerobotic deployment and assembly activities. These studies are being conducted in laboratory environments at NASA's Johnson Space Center (JSC), the Human Exploration Research Analog (HERA) at JSC and the NASA Extreme Environment Mission Operations (NEEMO) underwater habitat off the coast of Florida. The studies involve two human-in-the-loop interactive simulations developed by the NASA Exploration Systems Simulations (NExSyS) team at JSC. The first simulation investigates manipulation related activities while the second simulation investigates mobility related activities. The first simulation provides a simple real-time operator interface with displays and controls for a simulated 6 degree of freedom end effector. The initial version of the simulation uses a simple control mode to decouple the robotic kinematic constraints and a communications delay to model latency effects. This provides the basis for early testing with more detailed manipulation simulations planned for the future. Subjects are tested using five operating latencies that represent teleoperation conditions from local surface operations to orbital operations at Phobos, Deimos and ultimately high Martian orbit. Subject performance is measured and correlated with three distance-to-target zones of interest. Each zone represents a target distance ranging from beyond 10m in Zone 1, through 1 cm to contact in Zone 5 with a step size factor of 10. Collected data consists of both objective simulation data (time, distance, hand controller inputs, velocity) and subjective questionnaire data. The second simulation provides a simple real-time operator interface with displays and control of a simulated surface rover. The rover traverses a synthetic Mars-like terrain and must be maneuvered to avoid obstacles while progressing to its destination. Like the manipulator simulation, subjects are tested using five operating latencies that represent teleoperation conditions from local surface operations to orbital operations at Phobos, Deimos and ultimately high Martian orbit. The rover is also operated at three different traverse speeds to assess the correlation between latency and speed. Collected data consisted of both objective simulation data (time, distance, hand controller inputs, braking) and subjective questionnaire data. These studies are exploring relationships between task complexity, operating speeds, operator efficiencies, and communications latencies for low latency teleoperations in support of human planetary exploration. This paper presents early results from these studies along with the current observations and conclusions. These and planned future studies will help to inform NASA on the potential for low latency teleoperations to support human exploration of Mars and inform the design of robotic systems and exploration missions.

Gum chewing improves swallow frequency and latency in Parkinson patients: a preliminary study.

PubMed

South, Angela R; Somers, Stephanie M; Jog, Mandar S

2010-04-13

Reduced swallowing frequency affects secretion management in Parkinson disease (PD). Gum chewing increases saliva flow and swallow frequency. This study uses chewing gum to modify swallow frequency and latency between swallows in patients with PD. 1) Assess the frequency and latency of swallow at baseline (BL), during gum chewing (GC), and post gum chewing (PGC) for participants with PD (stage 2-4) nonsymptomatic for prandial dysphagia; and 2) assess carryover after gum is expectorated. Twenty participants were studied across 3 tasks, each of 5 minutes in duration: BL, GC, and PGC. Respiratory and laryngeal signals were continuously recorded using PowerLab (version 5.5.5; ADI Instruments, Castle Hill, Australia). Frequency and latency of swallow events were calculated. Differences (analysis of variance) are reported for frequency (p < 0.000001) and latency (p < 0.000001). Swallow frequency (mean +/- SD) increased during GC (14.95 +/- 3.02) compared with BL (3.1 +/- 2.85) and PGC (7.0 +/- 2.57). Latency in seconds (mean +/- SD) decreased during GC (24.1 +/- 4.174) and increased with BL (131.8 +/- 59.52) and PGC (mean = 60.74 +/- 25.25). Intertask comparisons (t test) found differences in swallow frequency and latency between tasks: BL vs GC (p < 0.0001, p < 0.0001), BL vs PGC (p < 0.0011, p < 0.0009), and GC vs PGC (p < 0.0001, p < 0.0002), respectively. Post hoc analysis showed carryover to 5.317 minutes. Modifying sensorimotor input by chewing gum alters frequency and latency of swallowing and may be an effective strategy for secretion management in Parkinson disease. This study provides Class III evidence that chewing gum increases swallow frequency and decreases latency of swallowing in an experiment in patients with stage 2 to 4 Parkinson disease who are nonsymptomatic for significant prandial dysphagia.

Fully Self-Contained Vision-Aided Navigation and Landing of a Micro Air Vehicle Independent from External Sensor Inputs

NASA Technical Reports Server (NTRS)

Brockers, Roland; Susca, Sara; Zhu, David; Matthies, Larry

2012-01-01

Direct-lift micro air vehicles have important applications in reconnaissance. In order to conduct persistent surveillance in urban environments, it is essential that these systems can perform autonomous landing maneuvers on elevated surfaces that provide high vantage points without the help of any external sensor and with a fully contained on-board software solution. In this paper, we present a micro air vehicle that uses vision feedback from a single down looking camera to navigate autonomously and detect an elevated landing platform as a surrogate for a roof top. Our method requires no special preparation (labels or markers) of the landing location. Rather, leveraging the planar character of urban structure, the landing platform detection system uses a planar homography decomposition to detect landing targets and produce approach waypoints for autonomous landing. The vehicle control algorithm uses a Kalman filter based approach for pose estimation to fuse visual SLAM (PTAM) position estimates with IMU data to correct for high latency SLAM inputs and to increase the position estimate update rate in order to improve control stability. Scale recovery is achieved using inputs from a sonar altimeter. In experimental runs, we demonstrate a real-time implementation running on-board a micro aerial vehicle that is fully self-contained and independent from any external sensor information. With this method, the vehicle is able to search autonomously for a landing location and perform precision landing maneuvers on the detected targets.

Visually Evoked Potentials after Panretinal Photocoagulation in Omani Patients with Uncontrolled Diabetes Mellitus

PubMed Central

Shenoy, Radha; Al-Belushi, Habiba; Al-Ajmi, Sadiqa; Al-Nabhani, Susan Margaret; Ganguly, Shyam Sunder; Bialasiewicz, Alexander A.

2008-01-01

Aim: To report on the changes of latency and amplitudes of the pattern VEP in patients with uncontrolled diabetes mellitus II and I before and after panretinal laser treatment. Design: Single center hospital based comparative study. Methods: One hundred eyes of patients with proliferative diabetic vitreoretinopathy, and HbA1C ≥ 10 percent were subjected to Pattern Visually Evoked Potentials (Medtronic keyopint system, Nicolet) prior to and 4 weeks after PRP. Results were compared to age-matched non-diabetic controls. Chi-Square test, and paired ‘t’ test were used for statistical analysis. Results: Preoperative mean VEP amplitude was 8.35mV±3.71, and not significantly different to the control group (mean 10.51mV±3.34) (chi square test p=1). Mean preoperative P100 latency was 106.93±7.90ms and significantly different to the control group (103.21±7.65ms) (paired t-test p=0.001). After laser treatment, VEP amplitudes decreased in 48/100 eyes (mean total 5.11mV±2.4), and P100 latency increased in 75/100 eyes (mean total 110.47±7.35ms). Conclusion: In this study, PRP was followed by a significant decrease in VEP amplitudes in 48 percent and increase in latency in 75 percent of eyes. PMID:21346837

Characterizing the roles of alpha and theta oscillations in multisensory attention.

PubMed

Keller, Arielle S; Payne, Lisa; Sekuler, Robert

2017-05-01

Cortical alpha oscillations (8-13Hz) appear to play a role in suppressing distractions when just one sensory modality is being attended, but do they also contribute when attention is distributed over multiple sensory modalities? For an answer, we examined cortical oscillations in human subjects who were dividing attention between auditory and visual sequences. In Experiment 1, subjects performed an oddball task with auditory, visual, or simultaneous audiovisual sequences in separate blocks, while the electroencephalogram was recorded using high-density scalp electrodes. Alpha oscillations were present continuously over posterior regions while subjects were attending to auditory sequences. This supports the idea that the brain suppresses processing of visual input in order to advantage auditory processing. During a divided-attention audiovisual condition, an oddball (a rare, unusual stimulus) occurred in either the auditory or the visual domain, requiring that attention be divided between the two modalities. Fronto-central theta band (4-7Hz) activity was strongest in this audiovisual condition, when subjects monitored auditory and visual sequences simultaneously. Theta oscillations have been associated with both attention and with short-term memory. Experiment 2 sought to distinguish these possible roles of fronto-central theta activity during multisensory divided attention. Using a modified version of the oddball task from Experiment 1, Experiment 2 showed that differences in theta power among conditions were independent of short-term memory load. Ruling out theta's association with short-term memory, we conclude that fronto-central theta activity is likely a marker of multisensory divided attention. Copyright © 2017 Elsevier Ltd. All rights reserved.

Characterizing the roles of alpha and theta oscillations in multisensory attention

PubMed Central

Keller, Arielle S.; Payne, Lisa; Sekuler, Robert

2017-01-01

Cortical alpha oscillations (8–13 Hz) appear to play a role in suppressing distractions when just one sensory modality is being attended, but do they also contribute when attention is distributed over multiple sensory modalities? For an answer, we examined cortical oscillations in human subjects who were dividing attention between auditory and visual sequences. In Experiment 1, subjects performed an oddball task with auditory, visual, or simultaneous audiovisual sequences in separate blocks, while the electroencephalogram was recorded using high-density scalp electrodes. Alpha oscillations were present continuously over posterior regions while subjects were attending to auditory sequences. This supports the idea that the brain suppresses processing of visual input in order to advantage auditory processing. During a divided-attention audiovisual condition, an oddball (a rare, unusual stimulus) occurred in either the auditory or the visual domain, requiring that attention be divided between the two modalities. Fronto-central theta band (4–7 Hz) activity was strongest in this audiovisual condition, when subjects monitored auditory and visual sequences simultaneously. Theta oscillations have been associated with both attention and with short-term memory. Experiment 2 sought to distinguish these possible roles of fronto-central theta activity during multisensory divided attention. Using a modified version of the oddball task from Experiment 1, Experiment 2 showed that differences in theta power among conditions were independent of short-term memory load. Ruling out theta’s association with short-term memory, we conclude that fronto-central theta activity is likely a marker of multisensory divided attention. PMID:28259771

Flash visual evoked potentials in patients with periventricular leucomalacia in children less than 1 year of age.

PubMed

Jethani, Jitendra; Jethani, Monika

2013-11-01

Children with periventricular leucomalacia (PVL) are known to have visual impairment of various forms starting from reduced vision, field defects, congnitive problems, and problems with hand eye coordination. There is very scant data/literature on the visual evoked potentials (VEPs) at an early age in children with PVL. We did a study to evaluate the flash visual evoked potentials (fVEPs) in children with PVL less than 1 year of age. A total of nine children diagnosed as having PVL on magnetic resonance imaging were included in the study. The mean age was 9.7μ 3.5 months. All children underwent handheld fVEPs under sedation at two different flash frequencies 1.4 and 8 Hz. The mean latency of N1 and P1 on stimulation with 1.4 Hz was 47.9μ 15.2 and 77.7μ 26.0 ms, respectively. However, on stimulation with 8 Hz the mean latency of N1 and P1 was 189.8μ 25.6 and 238.4μ 33.6 ms, respectively. The mean amplitude with 1.4 Hz and 8 stimulation frequency was 5.6μ 4.5 and 5.59μ 3 mV, respectively. We have found for the first time that there is a change in the latency and the delay occurs at 8 Hz frequency but not at 1.4 Hz. We also conclude that amplitudes by fVEPs may be normal even in presence of periventricular changes. The amplitudes of fVEPs are not reliable in children with PVL.

Are evoked potentials in patients with adult-onset pompe disease indicative of clinically relevant central nervous system involvement?

PubMed

Wirsching, Andreas; Müller-Felber, Wolfgang; Schoser, Benedikt

2014-08-01

Pompe disease is a multisystem autosomal recessive glycogen storage disease. Autoptic findings in patients with classic infantile and late-onset Pompe disease have proven that accumulation of glycogen can also be found in the peripheral and central nervous system. To assess the functional role of these pathologic findings, multimodal sensory evoked potentials were analyzed. Serial recordings for brainstem auditory, visual, and somatosensory evoked potentials of 11 late-onset Pompe patients were reviewed. Data at the onset of the enzyme replacement therapy with alglucosidase alfa were compared with follow-up recordings at 12 and 24 months. Brainstem auditory evoked potentials showed a delayed peak I in 1/10 patients and an increased I-III and I-V interpeak latency in 1/10 patients, respectively. The III-V interpeak latencies were in the normal range. Visual evoked potentials were completely normal. Median somatosensory evoked potentials showed an extended interpeak latency in 3/9 patients. Wilcoxon tests comparing age-matched subgroups found significant differences in brainstem auditory evoked potentials and visual evoked potentials. We found that the majority of recordings for evoked potentials were within the ranges for standard values, therefore reflecting the lack of clinically relevant central nervous system involvement. Regular surveillance by means of evoked potentials does not seem to be appropriate in late-onset Pompe patients.

Temporal characteristics of audiovisual information processing.

PubMed

Fuhrmann Alpert, Galit; Hein, Grit; Tsai, Nancy; Naumer, Marcus J; Knight, Robert T

2008-05-14

In complex natural environments, auditory and visual information often have to be processed simultaneously. Previous functional magnetic resonance imaging (fMRI) studies focused on the spatial localization of brain areas involved in audiovisual (AV) information processing, but the temporal characteristics of AV information flow in these regions remained unclear. In this study, we used fMRI and a novel information-theoretic approach to study the flow of AV sensory information. Subjects passively perceived sounds and images of objects presented either alone or simultaneously. Applying the measure of mutual information, we computed for each voxel the latency in which the blood oxygenation level-dependent signal had the highest information content about the preceding stimulus. The results indicate that, after AV stimulation, the earliest informative activity occurs in right Heschl's gyrus, left primary visual cortex, and the posterior portion of the superior temporal gyrus, which is known as a region involved in object-related AV integration. Informative activity in the anterior portion of superior temporal gyrus, middle temporal gyrus, right occipital cortex, and inferior frontal cortex was found at a later latency. Moreover, AV presentation resulted in shorter latencies in multiple cortical areas compared with isolated auditory or visual presentation. The results provide evidence for bottom-up processing from primary sensory areas into higher association areas during AV integration in humans and suggest that AV presentation shortens processing time in early sensory cortices.

Unifying Terrain Awareness for the Visually Impaired through Real-Time Semantic Segmentation

PubMed Central

Yang, Kailun; Wang, Kaiwei; Romera, Eduardo; Hu, Weijian; Sun, Dongming; Sun, Junwei; Cheng, Ruiqi; Chen, Tianxue; López, Elena

2018-01-01

Navigational assistance aims to help visually-impaired people to ambulate the environment safely and independently. This topic becomes challenging as it requires detecting a wide variety of scenes to provide higher level assistive awareness. Vision-based technologies with monocular detectors or depth sensors have sprung up within several years of research. These separate approaches have achieved remarkable results with relatively low processing time and have improved the mobility of impaired people to a large extent. However, running all detectors jointly increases the latency and burdens the computational resources. In this paper, we put forward seizing pixel-wise semantic segmentation to cover navigation-related perception needs in a unified way. This is critical not only for the terrain awareness regarding traversable areas, sidewalks, stairs and water hazards, but also for the avoidance of short-range obstacles, fast-approaching pedestrians and vehicles. The core of our unification proposal is a deep architecture, aimed at attaining efficient semantic understanding. We have integrated the approach in a wearable navigation system by incorporating robust depth segmentation. A comprehensive set of experiments prove the qualified accuracy over state-of-the-art methods while maintaining real-time speed. We also present a closed-loop field test involving real visually-impaired users, demonstrating the effectivity and versatility of the assistive framework. PMID:29748508

Auditory and visual orienting responses in listeners with and without hearing-impairment

PubMed Central

Brimijoin, W. Owen; McShefferty, David; Akeroyd, Michael A.

2015-01-01

Head movements are intimately involved in sound localization and may provide information that could aid an impaired auditory system. Using an infrared camera system, head position and orientation was measured for 17 normal-hearing and 14 hearing-impaired listeners seated at the center of a ring of loudspeakers. Listeners were asked to orient their heads as quickly as was comfortable toward a sequence of visual targets, or were blindfolded and asked to orient toward a sequence of loudspeakers playing a short sentence. To attempt to elicit natural orienting responses, listeners were not asked to reorient their heads to the 0° loudspeaker between trials. The results demonstrate that hearing-impairment is associated with several changes in orienting responses. Hearing-impaired listeners showed a larger difference in auditory versus visual fixation position and a substantial increase in initial and fixation latency for auditory targets. Peak velocity reached roughly 140 degrees per second in both groups, corresponding to a rate of change of approximately 1 microsecond of interaural time difference per millisecond of time. Most notably, hearing-impairment was associated with a large change in the complexity of the movement, changing from smooth sigmoidal trajectories to ones characterized by abruptly-changing velocities, directional reversals, and frequent fixation angle corrections. PMID:20550266

Overstimulation of newborn mice leads to behavioral differences and deficits in cognitive performance

PubMed Central

Christakis, D. A.; Ramirez, J. S. B.; Ramirez, J. M.

2012-01-01

Observational studies in humans have found associations between overstimulation in infancy via excessive television viewing and subsequent deficits in cognition and attention. We developed and tested a mouse model of overstimulation whereby p10 mice were subjected to audio (70 db) and visual stimulation (flashing lights) for six hours per day for a total of 42 days. 10 days later cognition and behavior were tested using the following tests: Light Dark Latency, Elevated Plus Maze, Novel Object Recognition, and Barnes Maze. In all tests, overstimulated mice performed significantly worse compared to controls suggesting increased activity and risk taking, diminished short term memory, and decreased cognitive function. These findings suggest that excessive non-normative stimulation during critical periods of brain development can have demonstrable untoward effects on subsequent neurocognitive function. PMID:22855702

Paradoxical visuomotor adaptation to reversed visual input is predicted by BDNF Val66Met polymorphism

PubMed Central

Barton, Brian; Treister, Andrew; Humphrey, Melanie; Abedi, Garen; Cramer, Steven C.; Brewer, Alyssa A.

2014-01-01

Brain-derived neurotrophic factor (BDNF) is the most abundant neurotrophin in the brain, influencing neural development, plasticity, and repair (Chen et al., 2004; Thoenen, 1995). The BDNF gene contains a single-nucleotide polymorphism (SNP) called Val66Met. The Met allele interferes with intracellular BDNF-trafficking, decreases activity-dependent BDNF secretion, and consequently is often associated with a shift from plasticity to stability in neural circuits (Egan et al., 2003). We investigated the behavioral consequences of the presence of the Met allele by comparing how 40 heterozygous subjects with the Val/Met genotype and 35 homozygous subjects with the Val/Val genotype performed on visuomotor tasks (reaching and navigation) under two conditions: normal vision and completely left-right reversed vision. As expected, subjects did not differ in their short-term ability to learn the tasks with normal vision (p = 0.58). Intuitively, it would be expected that homozygous Val/Val subjects with a propensity for greater BDNF-induced activity-dependent plasticity would learn new tasks more quickly than heterozygous Val/Met subjects with decreased BDNF secretion (Gilbert, Li, & Piech, 2009). However, we found the opposite here. When short-term mechanisms of visuomotor adaptation were engaged to compensate for the misalignment of visual and somatomotor information created by the left-right reversal of vision, heterozygous Val/Met subjects learned significantly more quickly than their homozygous Val/Val counterparts (p = 0.027). Our results demonstrate the paradoxical finding that the presence of the Met allele, which is thought to promote cortical stability, here improves immediate visuomotor adaptation to left–right-reversed visual input. PMID:25104829

Brainstem auditory evoked responses in man. 1: Effect of stimulus rise-fall time and duration

NASA Technical Reports Server (NTRS)

Hecox, K.; Squires, N.; Galambos, R.

1975-01-01

Short latency (under 10 msec) responses elicited by bursts of white noise were recorded from the scalps of human subjects. Response alterations produced by changes in the noise burst duration (on-time), inter-burst interval (off-time), and onset and offset shapes were analyzed. The latency of the most prominent response component, wave V, was markedly delayed with increases in stimulus rise time but was unaffected by changes in fall time. Increases in stimulus duration, and therefore in loudness, resulted in a systematic increase in latency. This was probably due to response recovery processes, since the effect was eliminated with increases in stimulus off-time. The amplitude of wave V was insensitive to changes in signal rise and fall times, while increasing signal on-time produced smaller amplitude responses only for sufficiently short off-times. It was concluded that wave V of the human auditory brainstem evoked response is solely an onset response.

[Mushroom poisoning--the dark side of mycetism].

PubMed

Flammer, René; Schenk-Jäger, Katharina M

2009-05-01

Most mushroom intoxications become evident within 12 hours with vomiting and diarrhea. They can be divided into incidents with a short latency (less than four hours) and incidents with a long latency (longer than four hours). As a rule of thumb amatoxin poisonings must be considered in case of symptoms appearing with a long latency (8-12-18 h), especially after consumption of non-controlled wild mushrooms. Shorter latencies do not exclude amatoxin poisoning. Large meals of mushrooms, which are rich in chitin, mixed meals and individual factors, may shorten latency and disguise amatoxin poisoning. Any vomiting and diarrhea after mushroom consumption is suspicious. Unless the mushrooms are not to be identified within 30 minutes by an expert, specific treatment for amatoxin poisoning must be started. Identification shall be achieved by macroscopic or microscopic means; and urine analysis for amatoxins are crucial. By commencing treatment before analysis, mortality rates may be as low as 5%. Current standards in amatoxin poisoning treatment can be obtained at the Swiss Toxicological Information Centre (Phone 145), where contacts to mycologists are available as well. Emergency mycologists are listed on the website www.vapko.ch. Of the 18 different syndromes we present the most common and most important in Switzerland. In an overview all of them are listed. Early gastrointestinal syndrome with its short latency of less than 4 h and indigestion with a very variable latency are the most common. Psychotropic symptoms after consumptions of fly agaric and panther cap are rare, in case of psilocybin-containing mushrooms, symptoms are frequent, but hardly ever lead to medical treatment. In case of renal failure and rhabdomyolysis of unknown origin, completing a patient's history by questioning nutritional habits might reveal causal relationship with ingestion of orellanin-containing mushrooms or tricholoma equestre respectively. Mushrooms in the backyard are attractive for children. We discuss possible approaches.

Kappa Opioid Receptors Mediate Heterosynaptic Suppression of Hippocampal Inputs in the Rat Ventral Striatum

PubMed Central

2017-01-01

Kappa opioid receptors (KORs) are highly enriched within the ventral striatum (VS) and are thought to modulate striatal neurotransmission. This includes presynaptic inhibition of local glutamatergic release from excitatory inputs to the VS. However, it is not known which inputs drive this modulation and what impact they have on the local circuit dynamics within the VS. Individual medium spiny neurons (MSNs) within the VS serve as a site of convergence for glutamatergic inputs arising from the PFC and limbic regions, such as the hippocampus (HP). Recent data suggest that competition can arise between these inputs with robust cortical activation leading to a reduction in ongoing HP-evoked MSN responses. Here, we investigated the contribution of KOR signaling in PFC-driven heterosynaptic suppression of HP inputs onto MSNs using whole-cell patch-clamp recordings in slices from adult rats. Optogenetically evoked HP EPSPs were greatly attenuated after a short latency (50 ms) following burst-like PFC electrical stimulation, and the magnitude of this suppression was partially reversed following blockade of GABAARs (GABA Type A receptors), but not GABABRs (GABA Type B receptors). A similar reduction in suppression was observed in the presence of the KOR antagonist, norBNI. Combined blockade of local GABAARs and KORs resulted in complete blockade of PFC-induced heterosynaptic suppression of less salient HP inputs. These findings highlight a mechanism by which strong, transient PFC activity can take precedence over other excitatory inputs to the VS. SIGNIFICANCE STATEMENT Emerging evidence suggests that kappa opioid receptor (KOR) activation can selectively modulate striatal glutamatergic inputs onto medium spiny neurons (MSNs). In this study, we found that robust cortical stimulation leads to a reduction in ongoing hippocampal-evoked MSNs responses through the combined recruitment of local inhibitory mechanisms and activation of presynaptic KORs in the ventral striatum (VS). These processes are likely to facilitate the efficient transfer of cortical information through the VS during critical decision making by dampening competing information from less salient excitatory inputs. These data provide a novel mechanism through which VS information processing could influence decision making, a function thought to occur primarily in the PFC. PMID:28642282

Time course of discrimination between emotional facial expressions: the role of visual saliency.

PubMed

Calvo, Manuel G; Nummenmaa, Lauri

2011-08-01

Saccadic and manual responses were used to investigate the speed of discrimination between happy and non-happy facial expressions in two-alternative-forced-choice tasks. The minimum latencies of correct saccadic responses indicated that the earliest time point at which discrimination occurred ranged between 200 and 280ms, depending on type of expression. Corresponding minimum latencies for manual responses ranged between 440 and 500ms. For both response modalities, visual saliency of the mouth region was a critical factor in facilitating discrimination: The more salient the mouth was in happy face targets in comparison with non-happy distracters, the faster discrimination was. Global image characteristics (e.g., luminance) and semantic factors (i.e., categorical similarity and affective valence of expression) made minor or no contribution to discrimination efficiency. This suggests that visual saliency of distinctive facial features, rather than the significance of expression, is used to make both early and later expression discrimination decisions. Copyright © 2011 Elsevier Ltd. All rights reserved.

Area/latency optimized early output asynchronous full adders and relative-timed ripple carry adders.

PubMed

Balasubramanian, P; Yamashita, S

2016-01-01

This article presents two area/latency optimized gate level asynchronous full adder designs which correspond to early output logic. The proposed full adders are constructed using the delay-insensitive dual-rail code and adhere to the four-phase return-to-zero handshaking. For an asynchronous ripple carry adder (RCA) constructed using the proposed early output full adders, the relative-timing assumption becomes necessary and the inherent advantages of the relative-timed RCA are: (1) computation with valid inputs, i.e., forward latency is data-dependent, and (2) computation with spacer inputs involves a bare minimum constant reverse latency of just one full adder delay, thus resulting in the optimal cycle time. With respect to different 32-bit RCA implementations, and in comparison with the optimized strong-indication, weak-indication, and early output full adder designs, one of the proposed early output full adders achieves respective reductions in latency by 67.8, 12.3 and 6.1 %, while the other proposed early output full adder achieves corresponding reductions in area by 32.6, 24.6 and 6.9 %, with practically no power penalty. Further, the proposed early output full adders based asynchronous RCAs enable minimum reductions in cycle time by 83.4, 15, and 8.8 % when considering carry-propagation over the entire RCA width of 32-bits, and maximum reductions in cycle time by 97.5, 27.4, and 22.4 % for the consideration of a typical carry chain length of 4 full adder stages, when compared to the least of the cycle time estimates of various strong-indication, weak-indication, and early output asynchronous RCAs of similar size. All the asynchronous full adders and RCAs were realized using standard cells in a semi-custom design fashion based on a 32/28 nm CMOS process technology.

Stroboscopic visual training improves information encoding in short-term memory.

PubMed

Appelbaum, L Gregory; Cain, Matthew S; Schroeder, Julia E; Darling, Elise F; Mitroff, Stephen R

2012-11-01

The visual system has developed to transform an undifferentiated and continuous flow of information into discrete and manageable representations, and this ability rests primarily on the uninterrupted nature of the input. Here we explore the impact of altering how visual information is accumulated over time by assessing how intermittent vision influences memory retention. Previous work has shown that intermittent, or stroboscopic, visual training (i.e., practicing while only experiencing snapshots of vision) can enhance visual-motor control and visual cognition, yet many questions remain unanswered about the mechanisms that are altered. In the present study, we used a partial-report memory paradigm to assess the possible changes in visual memory following training under stroboscopic conditions. In Experiment 1, the memory task was completed before and immediately after a training phase, wherein participants engaged in physical activities (e.g., playing catch) while wearing either specialized stroboscopic eyewear or transparent control eyewear. In Experiment 2, an additional group of participants underwent the same stroboscopic protocol but were delayed 24 h between training and assessment, so as to measure retention. In comparison to the control group, both stroboscopic groups (immediate and delayed retest) revealed enhanced retention of information in short-term memory, leading to better recall at longer stimulus-to-cue delays (640-2,560 ms). These results demonstrate that training under stroboscopic conditions has the capacity to enhance some aspects of visual memory, that these faculties generalize beyond the specific tasks that were trained, and that trained improvements can be maintained for at least a day.

Non-singleton colors are not attended faster than categories, but they are encoded faster: A combined approach of behavior, modeling and ERPs.

PubMed

Callahan-Flintoft, Chloe; Wyble, Brad

2017-11-01

The visual system is able to detect targets according to a variety of criteria, such as by categorical (letter vs digit) or featural attributes (color). These criteria are often used interchangeably in rapid serial visual presentation (RSVP) studies but little is known about how rapidly they are processed. The aim of this work was to compare the time course of attentional selection and memory encoding for different types of target criteria. We conducted two experiments where participants reported one or two targets (T1, T2) presented in lateral RSVP streams. Targets were marked either by being a singleton color (red letter among black letters), being categorically distinct (digits among letters) or non-singleton color (target color letter among heterogeneously colored letters). Using event related potential (ERPs) associated with attention and memory encoding (the N2pc and the P3 respectively), we compared the relative latency of these two processing stages for these three kinds of targets. In addition to these ERP measures, we obtained convergent behavioral measures for attention and memory encoding by presenting two targets in immediate sequence and comparing their relative accuracy and proportion of temporal order errors. Both behavioral and EEG measures revealed that singleton color targets were attended much more quickly than either non-singleton color or categorical targets, and there was very little difference between attention latencies to non-singleton color and categorical targets. There was however a difference in the speed of memory encoding for non-singleton color and category latencies in both behavioral and EEG measures, which shows that encoding latency differences do not always mirror attention latency differences. Copyright © 2017 Elsevier Ltd. All rights reserved.

Situational Awareness During Mass-Casualty Events: Command and Control

PubMed Central

Demchak, Barry; Chan, Theordore C.; Griswold, William G.; Lenert, Leslie

2006-01-01

In existing Incident Command systems1, situational awareness is achieved manually through paper tracking systems. Such systems often produce high latencies and incomplete data, resulting in inefficient and ineffective resource deployment. The WIISARD2 system collects much more data than a paper-based system, dramatically reducing latency while increasing the kinds and quality of information available to Incident Commanders. The WIISARD Command Center solves the problem of data overload and uncertainty through the careful use of limited screen area and novel visualization techniques. PMID:17238524

Factors of Influence on the Performance of a Short-Latency Non-Invasive Brain Switch: Evidence in Healthy Individuals and Implication for Motor Function Rehabilitation

PubMed Central

Xu, Ren; Jiang, Ning; Mrachacz-Kersting, Natalie; Dremstrup, Kim; Farina, Dario

2016-01-01

Brain-computer interfacing (BCI) has recently been applied as a rehabilitation approach for patients with motor disorders, such as stroke. In these closed-loop applications, a brain switch detects the motor intention from brain signals, e.g., scalp EEG, and triggers a neuroprosthetic device, either to deliver sensory feedback or to mimic real movements, thus re-establishing the compromised sensory-motor control loop and promoting neural plasticity. In this context, single trial detection of motor intention with short latency is a prerequisite. The performance of the event detection from EEG recordings is mainly determined by three factors: the type of motor imagery (e.g., repetitive, ballistic), the frequency band (or signal modality) used for discrimination (e.g., alpha, beta, gamma, and MRCP, i.e., movement-related cortical potential), and the processing technique (e.g., time-series analysis, sub-band power estimation). In this study, we investigated single trial EEG traces during movement imagination on healthy individuals, and provided a comprehensive analysis of the performance of a short-latency brain switch when varying these three factors. The morphological investigation showed a cross-subject consistency of a prolonged negative phase in MRCP, and a delayed beta rebound in sensory-motor rhythms during repetitive tasks. The detection performance had the greatest accuracy when using ballistic MRCP with time-series analysis. In this case, the true positive rate (TPR) was ~70% for a detection latency of ~200 ms. The results presented here are of practical relevance for designing BCI systems for motor function rehabilitation. PMID:26834551

Supramodal processing optimizes visual perceptual learning and plasticity.

PubMed

Zilber, Nicolas; Ciuciu, Philippe; Gramfort, Alexandre; Azizi, Leila; van Wassenhove, Virginie

2014-06-01

Multisensory interactions are ubiquitous in cortex and it has been suggested that sensory cortices may be supramodal i.e. capable of functional selectivity irrespective of the sensory modality of inputs (Pascual-Leone and Hamilton, 2001; Renier et al., 2013; Ricciardi and Pietrini, 2011; Voss and Zatorre, 2012). Here, we asked whether learning to discriminate visual coherence could benefit from supramodal processing. To this end, three groups of participants were briefly trained to discriminate which of a red or green intermixed population of random-dot-kinematograms (RDKs) was most coherent in a visual display while being recorded with magnetoencephalography (MEG). During training, participants heard no sound (V), congruent acoustic textures (AV) or auditory noise (AVn); importantly, congruent acoustic textures shared the temporal statistics - i.e. coherence - of visual RDKs. After training, the AV group significantly outperformed participants trained in V and AVn although they were not aware of their progress. In pre- and post-training blocks, all participants were tested without sound and with the same set of RDKs. When contrasting MEG data collected in these experimental blocks, selective differences were observed in the dynamic pattern and the cortical loci responsive to visual RDKs. First and common to all three groups, vlPFC showed selectivity to the learned coherence levels whereas selectivity in visual motion area hMT+ was only seen for the AV group. Second and solely for the AV group, activity in multisensory cortices (mSTS, pSTS) correlated with post-training performances; additionally, the latencies of these effects suggested feedback from vlPFC to hMT+ possibly mediated by temporal cortices in AV and AVn groups. Altogether, we interpret our results in the context of the Reverse Hierarchy Theory of learning (Ahissar and Hochstein, 2004) in which supramodal processing optimizes visual perceptual learning by capitalizing on sensory-invariant representations - here, global coherence levels across sensory modalities. Copyright © 2014 Elsevier Inc. All rights reserved.

Developmental dyslexia and vision

PubMed Central

Quercia, Patrick; Feiss, Léonard; Michel, Carine

2013-01-01

Developmental dyslexia affects almost 10% of school-aged children and represents a significant public health problem. Its etiology is unknown. The consistent presence of phonological difficulties combined with an inability to manipulate language sounds and the grapheme–phoneme conversion is widely acknowledged. Numerous scientific studies have also documented the presence of eye movement anomalies and deficits of perception of low contrast, low spatial frequency, and high frequency temporal visual information in dyslexics. Anomalies of visual attention with short visual attention spans have also been demonstrated in a large number of cases. Spatial orientation is also affected in dyslexics who manifest a preference for spatial attention to the right. This asymmetry may be so pronounced that it leads to a veritable neglect of space on the left side. The evaluation of treatments proposed to dyslexics whether speech or oriented towards the visual anomalies remains fragmentary. The advent of new explanatory theories, notably cerebellar, magnocellular, or proprioceptive, is an incentive for ophthalmologists to enter the world of multimodal cognition given the importance of the eye’s visual input. PMID:23690677

Simulation studies of vestibular macular afferent-discharge patterns using a new, quasi-3-D finite volume method

NASA Technical Reports Server (NTRS)

Ross, M. D.; Linton, S. W.; Parnas, B. R.

2000-01-01

A quasi-three-dimensional finite-volume numerical simulator was developed to study passive voltage spread in vestibular macular afferents. The method, borrowed from computational fluid dynamics, discretizes events transpiring in small volumes over time. The afferent simulated had three calyces with processes. The number of processes and synapses, and direction and timing of synapse activation, were varied. Simultaneous synapse activation resulted in shortest latency, while directional activation (proximal to distal and distal to proximal) yielded most regular discharges. Color-coded visualizations showed that the simulator discretized events and demonstrated that discharge produced a distal spread of voltage from the spike initiator into the ending. The simulations indicate that directional input, morphology, and timing of synapse activation can affect discharge properties, as must also distal spread of voltage from the spike initiator. The finite volume method has generality and can be applied to more complex neurons to explore discrete synaptic effects in four dimensions.

Age-related visual signal changes induced by hypoxemic hypoxia: a study on aircraft pilots of different ages.

PubMed

Pescosolido, Nicola; Buomprisco, Giuseppe; Di Blasio, Dario

2014-10-01

Exposure to high altitude leads to a series of alterations of higher nervous functions because of hypobaric hypoxia. Sensory systems, mainly the visual one, seem to be particularly involved. This study aimed to assess the effects of hypoxemic hypoxia on the transmission of the visual stimulus simulating a condition of breathing at an altitude of 18,000 feet (5,486 m) through the administration of an air mixture with 10% O2. The subjects involved in the study were 98 pilots of military aircraft (male, acclimated, healthy, 20/20 Uncorrected Visual Acuity (UCVA)/Best Corrected Visual Acuity (BCVA), and aged between 26 and 49 years) divided into 2 groups according to age (A: 26-36 years; B: 37-49 years). The visual evoked potentials were initially recorded at sea level (760 mm Hg) and subsequently at a simulated altitude of 18,000 feet (5,486 m) through the administration of an air mixture with 10% O2 that induced a blood saturation of 80% O2 after 15 minutes. The analysis was carried out using two different kinds of stimulus (15' and 60' of arc). The latency and the amplitude of N-75 (N1) and P-100 (P1) waves have been evaluated. Results obtained from visual evoked potentials were analyzed with Student t-test. In the first group (pilots aged 26-36 years), an increase in both latency and amplitude of P-100 wave was observed and in the second group (pilots aged 37-49 years), an increase was found in latency and a significant reduction in amplitude. The study suggests the existence of a mechanism or a particular anatomic and physiologic condition (probably the neurovascular coupling) that connects the local neuronal activity and the resulting changes in cerebral perfusion. This complex series of events binds together different structures and cell types, and it seems that younger people have a better resistance against the hypoxic insult to the central nervous system because of more efficient compensatory mechanisms.

Electrophysiological study of supraspinal input and spinal output of cat's subnucleus reticularis dorsalis (SRD) neurons.

PubMed

Velo, Patricia; Leiras, Roberto; Canedo, Antonio

2013-01-01

This work addressed the study of subnucleus reticularis dorsalis (SRD) neurons in relation to their supraspinal input and the spinal terminating sites of their descending axons. SRD extracellular unitary recordings from anesthetized cats aimed to specifically test, 1) the rostrocaudal segmental level reached by axons of spinally projecting (SPr) neurons collateralizing or not to or through the ipsilateral nucleus reticularis gigantocellularis (NRGc), 2) whether SPr fibers bifurcate to the thalamus, and 3) the effects exerted on SRD cells by electrically stimulating the locus coeruleus, the periaqueductal grey, the nucleus raphe magnus, and the mesencephalic locomotor region. From a total of 191 SPr fibers tested to cervical 2 (Ce2), thoracic 5 (Th5) and lumbar5 (Lu5) stimulation, 81 ended between Ce2 and Th5 with 39 of them branching to or through the NRGc; 21/49 terminating between Th5 and Lu5 collateralized to or through the same nucleus, as did 34/61 reaching Lu5. The mean antidromic conduction velocity of SPr fibers slowed in the more proximal segments and increased with terminating distance along the cord. None of the 110 axons tested sent collaterals to the thalamus; instead thalamic stimulation induced long-latency polysynaptic responses in most cells but also short-latency, presumed monosynaptic, in 7.9% of the tested neurons (18/227). Antidromic and orthodromic spikes were elicited from the locus coeruleus and nucleus raphe magnus, but exclusively orthodromic responses were observed following stimulation of the periaqueductal gray or mesencephalic locomotor region. The results suggest that information from pain-and-motor-related supraspinal structures converge on SRD cells that through SPr axons having conduction velocities tuned to their length may affect rostral and caudal spinal cord neurons at fixed delays, both directly and in parallel through different descending systems. The SRD will thus play a dual functional role by simultaneously regulating dorsal horn ascending noxious information and pain-related motor responses.

Electrophysiological Study of Supraspinal Input and Spinal Output of Cat's Subnucleus Reticularis Dorsalis (SRD) Neurons

PubMed Central

Canedo, Antonio

2013-01-01

This work addressed the study of subnucleus reticularis dorsalis (SRD) neurons in relation to their supraspinal input and the spinal terminating sites of their descending axons. SRD extracellular unitary recordings from anesthetized cats aimed to specifically test, 1) the rostrocaudal segmental level reached by axons of spinally projecting (SPr) neurons collateralizing or not to or through the ipsilateral nucleus reticularis gigantocellularis (NRGc), 2) whether SPr fibers bifurcate to the thalamus, and 3) the effects exerted on SRD cells by electrically stimulating the locus coeruleus, the periaqueductal grey, the nucleus raphe magnus, and the mesencephalic locomotor region. From a total of 191 SPr fibers tested to cervical 2 (Ce2), thoracic 5 (Th5) and lumbar5 (Lu5) stimulation, 81 ended between Ce2 and Th5 with 39 of them branching to or through the NRGc; 21/49 terminating between Th5 and Lu5 collateralized to or through the same nucleus, as did 34/61 reaching Lu5. The mean antidromic conduction velocity of SPr fibers slowed in the more proximal segments and increased with terminating distance along the cord. None of the 110 axons tested sent collaterals to the thalamus; instead thalamic stimulation induced long-latency polysynaptic responses in most cells but also short-latency, presumed monosynaptic, in 7.9% of the tested neurons (18/227). Antidromic and orthodromic spikes were elicited from the locus coeruleus and nucleus raphe magnus, but exclusively orthodromic responses were observed following stimulation of the periaqueductal gray or mesencephalic locomotor region. The results suggest that information from pain-and-motor-related supraspinal structures converge on SRD cells that through SPr axons having conduction velocities tuned to their length may affect rostral and caudal spinal cord neurons at fixed delays, both directly and in parallel through different descending systems. The SRD will thus play a dual functional role by simultaneously regulating dorsal horn ascending noxious information and pain-related motor responses. PMID:23544161

The Comparison of Visual Working Memory Representations with Perceptual Inputs

ERIC Educational Resources Information Center

Hyun, Joo-seok; Woodman, Geoffrey F.; Vogel, Edward K.; Hollingworth, Andrew; Luck, Steven J.

2009-01-01

The human visual system can notice differences between memories of previous visual inputs and perceptions of new visual inputs, but the comparison process that detects these differences has not been well characterized. In this study, the authors tested the hypothesis that differences between the memory of a stimulus array and the perception of a…

Electrophysiological Evidence for Ventral Stream Deficits in Schizophrenia Patients

PubMed Central

Plomp, Gijs; Roinishvili, Maya; Chkonia, Eka; Kapanadze, George; Kereselidze, Maia; Brand, Andreas; Herzog, Michael H.

2013-01-01

Schizophrenic patients suffer from many deficits including visual, attentional, and cognitive ones. Visual deficits are of particular interest because they are at the fore-end of information processing and can provide clear examples of interactions between sensory, perceptual, and higher cognitive functions. Visual deficits in schizophrenic patients are often attributed to impairments in the dorsal (where) rather than the ventral (what) stream of visual processing. We used a visual-masking paradigm in which patients and matched controls discriminated small vernier offsets. We analyzed the evoked electroencephalography (EEG) responses and applied distributed electrical source imaging techniques to estimate activity differences between conditions and groups throughout the brain. Compared with controls, patients showed strongly reduced discrimination accuracy, confirming previous work. The behavioral deficits corresponded to pronounced decreases in the evoked EEG response at around 200 ms after stimulus onset. At this latency, patients showed decreased activity for targets in left parietal cortex (dorsal stream), but the decrease was most pronounced in lateral occipital cortex (in the ventral stream). These deficiencies occurred at latencies that reflect object processing and fine shape discriminations. We relate the reduced ventral stream activity to deficient top-down processing of target stimuli and provide a framework for relating the commonly observed dorsal stream deficiencies with the currently observed ventral stream deficiencies. PMID:22258884

Electrophysiological evidence for ventral stream deficits in schizophrenia patients.

PubMed

Plomp, Gijs; Roinishvili, Maya; Chkonia, Eka; Kapanadze, George; Kereselidze, Maia; Brand, Andreas; Herzog, Michael H

2013-05-01

Schizophrenic patients suffer from many deficits including visual, attentional, and cognitive ones. Visual deficits are of particular interest because they are at the fore-end of information processing and can provide clear examples of interactions between sensory, perceptual, and higher cognitive functions. Visual deficits in schizophrenic patients are often attributed to impairments in the dorsal (where) rather than the ventral (what) stream of visual processing. We used a visual-masking paradigm in which patients and matched controls discriminated small vernier offsets. We analyzed the evoked electroencephalography (EEG) responses and applied distributed electrical source imaging techniques to estimate activity differences between conditions and groups throughout the brain. Compared with controls, patients showed strongly reduced discrimination accuracy, confirming previous work. The behavioral deficits corresponded to pronounced decreases in the evoked EEG response at around 200 ms after stimulus onset. At this latency, patients showed decreased activity for targets in left parietal cortex (dorsal stream), but the decrease was most pronounced in lateral occipital cortex (in the ventral stream). These deficiencies occurred at latencies that reflect object processing and fine shape discriminations. We relate the reduced ventral stream activity to deficient top-down processing of target stimuli and provide a framework for relating the commonly observed dorsal stream deficiencies with the currently observed ventral stream deficiencies.

Achilles Tendon Reflex (ATR) in response to short exposures of microgravity and hypergravity

NASA Technical Reports Server (NTRS)

Fujii, M.; Jaweed, M.

1992-01-01

Previous studies indicate that latency and amplitude of the Achilles tendon reflex (ATR) are reduced after exposure to microgravity for 28 days. The objective of this study was to quantitatively measure the latency of ATR during brief (20 sec) exposure to microgravity in KC-135 parabolic flights. Methods: The ATR was elicited in ten men during parabolic flight with the ankle held neutrally, planarflexed, and dorsiflexed. During flight, the ATR was elicited during the zero G and 1.8 G phases. Postflight testing was performed flying back to the airfield. Latencies to onset of the ATR were calculated and analyses of variance were performed to determine the effect of gravity and ankle position on latency. Result: The mean latencies for zero-G, 1.8-G and postflight with the ankle in the neutral position were 32.7 plus or minus 0.5 ms, and 33.1 plus or minus 0.7 ms respectively, which were not significantly different. There was a trend toward prolongation of latencies postflight. The mean latency for those who were motion sick was 32.1 plus or minus 0.1 ms compared to 34.0 plus or minus 0.3 ms for those who were not sick. Conclusions: These studies indicate that neither the level of gravity nor ankle position significantly affected the latency of the ATR.

Post-encoding control of working memory enhances processing of relevant information in rhesus monkeys (Macaca mulatta).

PubMed

Brady, Ryan J; Hampton, Robert R

2018-06-01

Working memory is a system by which a limited amount of information can be kept available for processing after the cessation of sensory input. Because working memory resources are limited, it is adaptive to focus processing on the most relevant information. We used a retro-cue paradigm to determine the extent to which monkey working memory possesses control mechanisms that focus processing on the most relevant representations. Monkeys saw a sample array of images, and shortly after the array disappeared, they were visually cued to a location that had been occupied by one of the sample images. The cue indicated which image should be remembered for the upcoming recognition test. By determining whether the monkeys were more accurate and quicker to respond to cued images compared to un-cued images, we tested the hypothesis that monkey working memory focuses processing on relevant information. We found a memory benefit for the cued image in terms of accuracy and retrieval speed with a memory load of two images. With a memory load of three images, we found a benefit in retrieval speed but only after shortening the onset latency of the retro-cue. Our results demonstrate previously unknown flexibility in the cognitive control of memory in monkeys, suggesting that control mechanisms in working memory likely evolved in a common ancestor of humans and monkeys more than 32 million years ago. Future work should be aimed at understanding the interaction between memory load and the ability to control memory resources, and the role of working memory control in generating differences in cognitive capacity among primates. Copyright © 2018 Elsevier B.V. All rights reserved.

Visual and proprioceptive interaction in patients with bilateral vestibular loss☆

PubMed Central

Cutfield, Nicholas J.; Scott, Gregory; Waldman, Adam D.; Sharp, David J.; Bronstein, Adolfo M.

2014-01-01

Following bilateral vestibular loss (BVL) patients gradually adapt to the loss of vestibular input and rely more on other sensory inputs. Here we examine changes in the way proprioceptive and visual inputs interact. We used functional magnetic resonance imaging (fMRI) to investigate visual responses in the context of varying levels of proprioceptive input in 12 BVL subjects and 15 normal controls. A novel metal-free vibrator was developed to allow vibrotactile neck proprioceptive input to be delivered in the MRI system. A high level (100 Hz) and low level (30 Hz) control stimulus was applied over the left splenius capitis; only the high frequency stimulus generates a significant proprioceptive stimulus. The neck stimulus was applied in combination with static and moving (optokinetic) visual stimuli, in a factorial fMRI experimental design. We found that high level neck proprioceptive input had more cortical effect on brain activity in the BVL patients. This included a reduction in visual motion responses during high levels of proprioceptive input and differential activation in the midline cerebellum. In early visual cortical areas, the effect of high proprioceptive input was present for both visual conditions but in lateral visual areas, including V5/MT, the effect was only seen in the context of visual motion stimulation. The finding of a cortical visuo-proprioceptive interaction in BVL patients is consistent with behavioural data indicating that, in BVL patients, neck afferents partly replace vestibular input during the CNS-mediated compensatory process. An fMRI cervico-visual interaction may thus substitute the known visuo-vestibular interaction reported in normal subject fMRI studies. The results provide evidence for a cortical mechanism of adaptation to vestibular failure, in the form of an enhanced proprioceptive influence on visual processing. The results may provide the basis for a cortical mechanism involved in proprioceptive substitution of vestibular function in BVL patients. PMID:25061564

Visual and proprioceptive interaction in patients with bilateral vestibular loss.

PubMed

Cutfield, Nicholas J; Scott, Gregory; Waldman, Adam D; Sharp, David J; Bronstein, Adolfo M

2014-01-01

Following bilateral vestibular loss (BVL) patients gradually adapt to the loss of vestibular input and rely more on other sensory inputs. Here we examine changes in the way proprioceptive and visual inputs interact. We used functional magnetic resonance imaging (fMRI) to investigate visual responses in the context of varying levels of proprioceptive input in 12 BVL subjects and 15 normal controls. A novel metal-free vibrator was developed to allow vibrotactile neck proprioceptive input to be delivered in the MRI system. A high level (100 Hz) and low level (30 Hz) control stimulus was applied over the left splenius capitis; only the high frequency stimulus generates a significant proprioceptive stimulus. The neck stimulus was applied in combination with static and moving (optokinetic) visual stimuli, in a factorial fMRI experimental design. We found that high level neck proprioceptive input had more cortical effect on brain activity in the BVL patients. This included a reduction in visual motion responses during high levels of proprioceptive input and differential activation in the midline cerebellum. In early visual cortical areas, the effect of high proprioceptive input was present for both visual conditions but in lateral visual areas, including V5/MT, the effect was only seen in the context of visual motion stimulation. The finding of a cortical visuo-proprioceptive interaction in BVL patients is consistent with behavioural data indicating that, in BVL patients, neck afferents partly replace vestibular input during the CNS-mediated compensatory process. An fMRI cervico-visual interaction may thus substitute the known visuo-vestibular interaction reported in normal subject fMRI studies. The results provide evidence for a cortical mechanism of adaptation to vestibular failure, in the form of an enhanced proprioceptive influence on visual processing. The results may provide the basis for a cortical mechanism involved in proprioceptive substitution of vestibular function in BVL patients.

Load-Dependent Increases in Delay-Period Alpha-Band Power Track the Gating of Task-Irrelevant Inputs to Working Memory.

PubMed

Heinz, Andrew J; Johnson, Jeffrey S

2017-01-01

Studies exploring the role of neural oscillations in cognition have revealed sustained increases in alpha-band power (ABP) during the delay period of verbal and visual working memory (VWM) tasks. There have been various proposals regarding the functional significance of such increases, including the inhibition of task-irrelevant cortical areas as well as the active retention of information in VWM. The present study examines the role of delay-period ABP in mediating the effects of interference arising from on-going visual processing during a concurrent VWM task. Specifically, we reasoned that, if set-size dependent increases in ABP represent the gating out of on-going task-irrelevant visual inputs, they should be predictive with respect to some modulation in visual evoked potentials resulting from a task-irrelevant delay period probe stimulus. In order to investigate this possibility, we recorded the electroencephalogram while subjects performed a change detection task requiring the retention of two or four novel shapes. On a portion of trials, a novel, task-irrelevant bilateral checkerboard probe was presented mid-way through the delay. Analyses focused on examining correlations between set-size dependent increases in ABP and changes in the magnitude of the P1, N1 and P3a components of the probe-evoked response and how such increases might be related to behavior. Results revealed that increased delay-period ABP was associated with changes in the amplitude of the N1 and P3a event-related potential (ERP) components, and with load-dependent changes in capacity when the probe was presented during the delay. We conclude that load-dependent increases in ABP likely play a role in supporting short-term retention by gating task-irrelevant sensory inputs and suppressing potential sources of disruptive interference.

Load-Dependent Increases in Delay-Period Alpha-Band Power Track the Gating of Task-Irrelevant Inputs to Working Memory

PubMed Central

Heinz, Andrew J.; Johnson, Jeffrey S.

2017-01-01

Studies exploring the role of neural oscillations in cognition have revealed sustained increases in alpha-band power (ABP) during the delay period of verbal and visual working memory (VWM) tasks. There have been various proposals regarding the functional significance of such increases, including the inhibition of task-irrelevant cortical areas as well as the active retention of information in VWM. The present study examines the role of delay-period ABP in mediating the effects of interference arising from on-going visual processing during a concurrent VWM task. Specifically, we reasoned that, if set-size dependent increases in ABP represent the gating out of on-going task-irrelevant visual inputs, they should be predictive with respect to some modulation in visual evoked potentials resulting from a task-irrelevant delay period probe stimulus. In order to investigate this possibility, we recorded the electroencephalogram while subjects performed a change detection task requiring the retention of two or four novel shapes. On a portion of trials, a novel, task-irrelevant bilateral checkerboard probe was presented mid-way through the delay. Analyses focused on examining correlations between set-size dependent increases in ABP and changes in the magnitude of the P1, N1 and P3a components of the probe-evoked response and how such increases might be related to behavior. Results revealed that increased delay-period ABP was associated with changes in the amplitude of the N1 and P3a event-related potential (ERP) components, and with load-dependent changes in capacity when the probe was presented during the delay. We conclude that load-dependent increases in ABP likely play a role in supporting short-term retention by gating task-irrelevant sensory inputs and suppressing potential sources of disruptive interference. PMID:28555099

The effect of spectral filters on VEP and alpha-wave responses.

PubMed

Willeford, Kevin T; Fimreite, Vanessa; Ciuffreda, Kenneth J

2016-01-01

Spectral filters are used to treat light sensitivity in individuals with traumatic brain injury (TBI); however, the effect of these filters on normal visual function has not been elucidated. Thus, the current study aimed to determine the effect of spectral filters on objectively-measured visual-evoked potential (VEP) and alpha-wave responses in the visually-normal population. The full-field (15°H×17°V), pattern-reversal VEP (20' check size, mean luminance 52cd/m(2)) was administered to 20 visually-normal individuals. They were tested with four Intuitive-Colorimeter-derived, broad-band, spectral filters (i.e., gray/neutral density, blue, yellow, and red), which produced similar luminance values for the test stimulus. The VEP N75 and P100 latencies, and VEP amplitude, were recorded. Power spectrum analysis was used to derive the respective powers at each frequency, and peak frequency, for the selected 9-11Hz components of the alpha band. Both N75 and P100 latencies increased with the addition of each filter when compared to baseline. Additionally, each filter numerically reduced intra-session amplitude variability relative to baseline. There were no significant effects on either the mean VEP amplitude or alpha wave parameters. The Intuitive Colorimeter filters significantly increased both N75 and P100 latencies, an effect which is primarily attributable (∼75%) to luminance, and in some cases, specific spectral effects (e.g., blue and red). VEP amplitude and alpha power were not significantly affected. These findings provide an important reference to which either amplitude or power changes in light-sensitive, younger clinical groups can be compared. Copyright © 2015 Spanish General Council of Optometry. Published by Elsevier Espana. All rights reserved.

The effect of spectral filters on VEP and alpha-wave responses

PubMed Central

Willeford, Kevin T.; Fimreite, Vanessa; Ciuffreda, Kenneth J.

2015-01-01

Purpose Spectral filters are used to treat light sensitivity in individuals with traumatic brain injury (TBI); however, the effect of these filters on normal visual function has not been elucidated. Thus, the current study aimed to determine the effect of spectral filters on objectively-measured visual-evoked potential (VEP) and alpha-wave responses in the visually-normal population. Methods The full-field (15°H × 17°V), pattern-reversal VEP (20′ check size, mean luminance 52 cd/m2) was administered to 20 visually-normal individuals. They were tested with four Intuitive-Colorimeter-derived, broad-band, spectral filters (i.e., gray/neutral density, blue, yellow, and red), which produced similar luminance values for the test stimulus. The VEP N75 and P100 latencies, and VEP amplitude, were recorded. Power spectrum analysis was used to derive the respective powers at each frequency, and peak frequency, for the selected 9–11 Hz components of the alpha band. Results Both N75 and P100 latencies increased with the addition of each filter when compared to baseline. Additionally, each filter numerically reduced intra-session amplitude variability relative to baseline. There were no significant effects on either the mean VEP amplitude or alpha wave parameters. Conclusions The Intuitive Colorimeter filters significantly increased both N75 and P100 latencies, an effect which is primarily attributable (∼75%) to luminance, and in some cases, specific spectral effects (e.g., blue and red). VEP amplitude and alpha power were not significantly affected. These findings provide an important reference to which either amplitude or power changes in light-sensitive, younger clinical groups can be compared. PMID:26293969

A comparative study of the usefulness of color vision, photostress recovery time, and visual evoked potential tests in early detection of ocular toxicity from hydroxychloroquine.

PubMed

Heravian, Javad; Saghafi, Massoud; Shoeibi, Naser; Hassanzadeh, Samira; Shakeri, Mohammad Taghi; Sharepoor, Maria

2011-08-01

Ocular toxicity from hydroxychloroquine (HCQ) is rare, but its potential permanence and severity makes it imperative to employ measures and screening protocols to minimize its occurrence. This study was performed to assess the usefulness of color vision, photo stress recovery time (PSRT), and visual evoked potentials (VEP) in early detection of ocular toxicity of HCQ, in patients with rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). 86 patients were included in the study and divided into three groups: (1) with history of HCQ use: interventional 1 (Int.1) without fundoscopic changes and Int.2 with fundoscopic changes; and (2) without history of HCQ use, as control. Visual field, color vision, PSRT and VEP results were recorded for all patients and the effect of age, disease duration, treatment duration and cumulative dose of HCQ on each test was assessed in each group. There was a significant relationship among PSRT and age, treatment duration, cumulative dose of HCQ and disease duration (P<0.001 for all). Color vision was normal in all the cases. P100 amplitude was not different between the three groups (P=0.846), but P100 latency was significantly different (P=0.025) and for Int.2 it was greater than the others. The percentage of abnormal visual fields for Int.2 was more than Int.1 and control groups (P=0.002 and P=0.005 respectively), but Int.1 and control groups were not significantly different (P>0.50). In the early stages of maculopathy, P100 latencies of VEP and PSRT are useful predictors of HCQ ocular toxicity. In patients without ocular symptoms and fundoscopic changes, the P100 latency of VEP predicts more precisely than the others.

Does the reading of different orthographies produce distinct brain activity patterns? An ERP study.

PubMed

Bar-Kochva, Irit; Breznitz, Zvia

2012-01-01

Orthographies vary in the degree of transparency of spelling-sound correspondence. These range from shallow orthographies with transparent grapheme-phoneme relations, to deep orthographies, in which these relations are opaque. Only a few studies have examined whether orthographic depth is reflected in brain activity. In these studies a between-language design was applied, making it difficult to isolate the aspect of orthographic depth. In the present work this question was examined using a within-subject-and-language investigation. The participants were speakers of Hebrew, as they are skilled in reading two forms of script transcribing the same oral language. One form is the shallow pointed script (with diacritics), and the other is the deep unpointed script (without diacritics). Event-related potentials (ERPs) were recorded while skilled readers carried out a lexical decision task in the two forms of script. A visual non-orthographic task controlled for the visual difference between the scripts (resulting from the addition of diacritics to the pointed script only). At an early visual-perceptual stage of processing (~165 ms after target onset), the pointed script evoked larger amplitudes with longer latencies than the unpointed script at occipital-temporal sites. However, these effects were not restricted to orthographic processing, and may therefore have reflected, at least in part, the visual load imposed by the diacritics. Nevertheless, the results implied that distinct orthographic processing may have also contributed to these effects. At later stages (~340 ms after target onset) the unpointed script elicited larger amplitudes than the pointed one with earlier latencies. As this latency has been linked to orthographic-linguistic processing and to the classification of stimuli, it is suggested that these differences are associated with distinct lexical processing of a shallow and a deep orthography.

Flash visual evoked potentials in patients with periventricular leucomalacia in children less than 1 year of age

PubMed Central

Jethani, Jitendra; Jethani, Monika

2013-01-01

Background and Aim: Children with periventricular leucomalacia (PVL) are known to have visual impairment of various forms starting from reduced vision, field defects, congnitive problems, and problems with hand eye coordination. There is very scant data/literature on the visual evoked potentials (VEPs) at an early age in children with PVL. We did a study to evaluate the flash visual evoked potentials (fVEPs) in children with PVL less than 1 year of age. Materials and Methods: A total of nine children diagnosed as having PVL on magnetic resonance imaging were included in the study. The mean age was 9.7± 3.5 months. All children underwent handheld fVEPs under sedation at two different flash frequencies 1.4 and 8 Hz. Results: The mean latency of N1 and P1 on stimulation with 1.4 Hz was 47.9± 15.2 and 77.7± 26.0 ms, respectively. However, on stimulation with 8 Hz the mean latency of N1 and P1 was 189.8± 25.6 and 238.4± 33.6 ms, respectively. The mean amplitude with 1.4 Hz and 8 stimulation frequency was 5.6± 4.5 and 5.59± 3 mV, respectively. Conclusion: We have found for the first time that there is a change in the latency and the delay occurs at 8 Hz frequency but not at 1.4 Hz. We also conclude that amplitudes by fVEPs may be normal even in presence of periventricular changes. The amplitudes of fVEPs are not reliable in children with PVL. PMID:24343595

Planning in sentence production: evidence for the phrase as a default planning scope.

PubMed

Martin, Randi C; Crowther, Jason E; Knight, Meredith; Tamborello, Franklin P; Yang, Chin-Lung

2010-08-01

Controversy remains as to the scope of advanced planning in language production. Smith and Wheeldon (1999) found significantly longer onset latencies when subjects described moving-picture displays by producing sentences beginning with a complex noun phrase than for matched sentences beginning with a simple noun phrase. While these findings are consistent with a phrasal scope of planning, they might also be explained on the basis of: (1) greater retrieval fluency for the second content word in the simple initial noun phrase sentences and (2) visual grouping factors. In Experiments 1 and 2, retrieval fluency for the second content word was equated for the complex and simple initial noun phrase conditions. Experiments 3 and 4 addressed the visual grouping hypothesis by using stationary displays and by comparing onset latencies for the same display for sentence and list productions. Longer onset latencies for the sentences beginning with a complex noun phrase were obtained in all experiments, supporting the phrasal scope of planning hypothesis. The results indicate that in speech, as in other motor production domains, planning occurs beyond the minimal production unit. Copyright (c) 2010 Elsevier B.V. All rights reserved.

Selectivity of N170 for visual words in the right hemisphere: Evidence from single-trial analysis.

PubMed

Yang, Hang; Zhao, Jing; Gaspar, Carl M; Chen, Wei; Tan, Yufei; Weng, Xuchu

2017-08-01

Neuroimaging and neuropsychological studies have identified the involvement of the right posterior region in the processing of visual words. Interestingly, in contrast, ERP studies of the N170 typically demonstrate selectivity for words more strikingly over the left hemisphere. Why is right hemisphere selectivity for words during the N170 epoch typically not observed, despite the clear involvement of this region in word processing? One possibility is that amplitude differences measured on averaged ERPs in previous studies may have been obscured by variation in peak latency across trials. This study examined this possibility by using single-trial analysis. Results show that words evoked greater single-trial N170s than control stimuli in the right hemisphere. Additionally, we observed larger trial-to-trial variability on N170 peak latency for words as compared to control stimuli over the right hemisphere. Results demonstrate that, in contrast to much of the prior literature, the N170 can be selective to words over the right hemisphere. This discrepancy is explained in terms of variability in trial-to-trial peak latency for responses to words over the right hemisphere. © 2017 Society for Psychophysiological Research.

Frequency-band signatures of visual responses to naturalistic input in ferret primary visual cortex during free viewing.

PubMed

Sellers, Kristin K; Bennett, Davis V; Fröhlich, Flavio

2015-02-19

Neuronal firing responses in visual cortex reflect the statistics of visual input and emerge from the interaction with endogenous network dynamics. Artificial visual stimuli presented to animals in which the network dynamics were constrained by anesthetic agents or trained behavioral tasks have provided fundamental understanding of how individual neurons in primary visual cortex respond to input. In contrast, very little is known about the mesoscale network dynamics and their relationship to microscopic spiking activity in the awake animal during free viewing of naturalistic visual input. To address this gap in knowledge, we recorded local field potential (LFP) and multiunit activity (MUA) simultaneously in all layers of primary visual cortex (V1) of awake, freely viewing ferrets presented with naturalistic visual input (nature movie clips). We found that naturalistic visual stimuli modulated the entire oscillation spectrum; low frequency oscillations were mostly suppressed whereas higher frequency oscillations were enhanced. In average across all cortical layers, stimulus-induced change in delta and alpha power negatively correlated with the MUA responses, whereas sensory-evoked increases in gamma power positively correlated with MUA responses. The time-course of the band-limited power in these frequency bands provided evidence for a model in which naturalistic visual input switched V1 between two distinct, endogenously present activity states defined by the power of low (delta, alpha) and high (gamma) frequency oscillatory activity. Therefore, the two mesoscale activity states delineated in this study may define the degree of engagement of the circuit with the processing of sensory input. Copyright © 2014 Elsevier B.V. All rights reserved.

Estimation of the Horizon in Photographed Outdoor Scenes by Human and Machine

PubMed Central

Herdtweck, Christian; Wallraven, Christian

2013-01-01

We present three experiments on horizon estimation. In Experiment 1 we verify the human ability to estimate the horizon in static images from only visual input. Estimates are given without time constraints with emphasis on precision. The resulting estimates are used as baseline to evaluate horizon estimates from early visual processes. Stimuli are presented for only ms and then masked to purge visual short-term memory and enforcing estimates to rely on early processes, only. The high agreement between estimates and the lack of a training effect shows that enough information about viewpoint is extracted in the first few hundred milliseconds to make accurate horizon estimation possible. In Experiment 3 we investigate several strategies to estimate the horizon in the computer and compare human with machine “behavior” for different image manipulations and image scene types. PMID:24349073

Modeling the Length Effect: Specifying the Relation with Visual and Phonological Correlates of Reading

ERIC Educational Resources Information Center

van den Boer, Madelon; de Jong, Peter F.; Haentjens-van Meeteren, Marleen M.

2013-01-01

Beginning readers' reading latencies increase as words become longer. This length effect is believed to be a marker of a serial reading process. We examined the effects of visual and phonological skills on the length effect. Participants were 184 second-grade children who read 3- to 5-letter words and nonwords. Results indicated that reading…

[Cortical potentials evoked to response to a signal to make a memory-guided saccade].

PubMed

Slavutskaia, M V; Moiseeva, V V; Shul'govskiĭ, V V

2010-01-01

The difference in parameters of visually guided and memory-guided saccades was shown. Increase in the memory-guided saccade latency as compared to that of the visually guided saccades may indicate the deceleration of saccadic programming on the basis of information extraction from the memory. The comparison of parameters and topography of evoked components N1 and P1 of the evoked potential on the signal to make a memory- or visually guided saccade suggests that the early stage of the saccade programming associated with the space information processing is performed predominantly with top-down attention mechanism before the memory-guided saccade and bottom-up mechanism before the visually guided saccade. The findings show that the increase in the latency of the memory-guided saccades is connected with decision making at the central stage of the saccade programming. We proposed that wave N2, which develops in the middle of the latent period of the memory-guided saccades, is correlated with this process. Topography and spatial dynamics of components N1, P1 and N2 testify that the memory-guided saccade programming is controlled by the frontal mediothalamic system of selective attention and left-hemispheric brain mechanisms of motor attention.

Comparison of visual evoked potential monitoring during spine surgeries under total intravenous anesthesia versus balanced general anesthesia.

PubMed

Uribe, Alberto A; Mendel, Ehud; Peters, Zoe A; Shneker, Bassel F; Abdel-Rasoul, Mahmoud; Bergese, Sergio D

2017-10-01

To determine the comparison of its clinical utility and safety profile for visual evoked potential (VEP) monitoring during prone spine surgeries under total intravenous anesthesia (TIVA) versus balanced general anesthesia using the SightSaver™ visual stimulator. The protocol was designed asa pilot, single center, prospective, randomized, and double-arm study. Subjects were randomized to receive either TIVA or balanced general anesthesia. Following induction and intubation, 8 electrodes were placed subcutaneously to collect VEP recordings. The SightSaver™ visual stimulator was placed on the subject's scalp before prone positioning. VEP waveforms were recorded every 30min and assessed by a neurophysiologist throughout the length of surgery. A total of 19 subjects were evaluated and VEP waveforms were successfully collected. TIVA group showed higher amplitude and lower latency than balanced anesthesia. Our data suggested that TIVA is associated with higher VEP amplitude and shorter latencies than balanced general anesthesia; therefore, TIVA could be the most efficient anesthesia regimen for VEP monitoring. The findings help to better understand the effect of different anesthesia regimens on intra-operative VEP monitoring. Copyright © 2017 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.

Improving Precipitation Forcings for the National Water Model

NASA Astrophysics Data System (ADS)

Fall, G. M.; Zhang, Z.; Miller, D.; Kitzmiller, D.; Patrick, N.; Sparrow, K.; Olheiser, C.; Szeliga, T.

2017-12-01

The National Weather Service's Office of Water Prediction (NWS/OWP) produces operational hydrologic products, many of which are generated by the National Water Model (NWM). NWM analysis cycles (also known as "near-real-time" or "update" cycles) are of key importance, since the land surface states and fluxes they produce are used to initialize all forecast cycles. Among all forcing fields (which include precipitation, temperature, humidity, radiation, and wind), precipitation is particularly important. Currently, NWM precipitation forcings for analysis cycles are generated by combining hourly radar-derived precipitation products from the Multi-Radar, Multi-Sensor (MRMS) system with short-term quantitative precipitation forecasts (QPF) from the Rapid Refresh (RAP) and High Resolution Rapid Refresh (HRRR) systems. Short term QPF is used in analysis cycles to fill coverage gaps in MRMS products, and its inclusion is necessary due to the short latency associated with NWM analysis cycles relative to the availability of other operational precipitation analyses. This presentation will describe the methodology used to remove QPF bias and to spatially merge MRMS, HRRR, and RAP into hourly forcing inputs for NWM version 2.0, expected to enter into operations in late 2018. The accuracy of version 2.0 precipitation forcings relative to reference data sources, and the degree to which these forcings will represent an improvement over those used to drive the previous NWM version (1.2), will be described.

ERP Go/NoGo condition effects are better detected with separate PCAs.

PubMed

Barry, Robert J; De Blasio, Frances M; Fogarty, Jack S; Karamacoska, Diana

2016-08-01

We explored the separation of Go and NoGo effects in the ERP components elicited in an equiprobable Go/NoGo task, using different forms of temporal Principal Components Analysis (PCA). Following exploratory simulation studies assessing the PCA impact of latency jitter and between-condition latency differences in the P3 latency range, an empirical study compared results of a Combined PCA carried out using both Go and NoGo ERPs together as input, with those from two Separate PCAs carried out on the Go and NoGo ERPs separately. The simulation studies indicated that Separate PCAs provide adequate component recovery in the presence of P3 latency jitter, and that Combined PCAs provide good separation of components only when systematic condition-related latency differences are sufficiently large (here ~110ms). In the empirical data, broadly-similar components were obtained from the Combined and Separate PCAs, supporting previous findings from Combined PCA investigations, and the consequent interpretations of the sequential processing involved. However, the Separate PCAs generated latency differences for components in the Go and NoGo processing chains that better matched the late Go/NoGo ERP peaks, and produced better-defined and larger components that fitted the stages in a hypothetical processing schema developed for this paradigm. Overall, the Separate PCAs yielded a better partitioning of the ERP variance associated with the Go and NoGo conditions, and should be considered as the first choice in future investigations if systematic component or subcomponent latency differences are present or suspected. Copyright © 2016 Elsevier B.V. All rights reserved.

Rank Order Coding: a Retinal Information Decoding Strategy Revealed by Large-Scale Multielectrode Array Retinal Recordings.

PubMed

Portelli, Geoffrey; Barrett, John M; Hilgen, Gerrit; Masquelier, Timothée; Maccione, Alessandro; Di Marco, Stefano; Berdondini, Luca; Kornprobst, Pierre; Sernagor, Evelyne

2016-01-01

How a population of retinal ganglion cells (RGCs) encodes the visual scene remains an open question. Going beyond individual RGC coding strategies, results in salamander suggest that the relative latencies of a RGC pair encode spatial information. Thus, a population code based on this concerted spiking could be a powerful mechanism to transmit visual information rapidly and efficiently. Here, we tested this hypothesis in mouse by recording simultaneous light-evoked responses from hundreds of RGCs, at pan-retinal level, using a new generation of large-scale, high-density multielectrode array consisting of 4096 electrodes. Interestingly, we did not find any RGCs exhibiting a clear latency tuning to the stimuli, suggesting that in mouse, individual RGC pairs may not provide sufficient information. We show that a significant amount of information is encoded synergistically in the concerted spiking of large RGC populations. Thus, the RGC population response described with relative activities, or ranks, provides more relevant information than classical independent spike count- or latency- based codes. In particular, we report for the first time that when considering the relative activities across the whole population, the wave of first stimulus-evoked spikes is an accurate indicator of stimulus content. We show that this coding strategy coexists with classical neural codes, and that it is more efficient and faster. Overall, these novel observations suggest that already at the level of the retina, concerted spiking provides a reliable and fast strategy to rapidly transmit new visual scenes.

Short latency vestibular evoked potentials in the Japanese quail (Coturnix coturnix japonica)

NASA Technical Reports Server (NTRS)

Jones, S. M.; Jones, T. A.; Shukla, R.

1997-01-01

Short-latency vestibular-evoked potentials to pulsed linear acceleration were characterized in the quail. Responses occurred within 8 ms following the onset of stimuli and were composed of a series of positive and negative peaks. The latencies and amplitudes of the first four peaks were quantitatively characterized. Mean latencies at 1.0 g ms-1 ranged from 1265 +/- 208 microseconds (P1, N = 18) to 4802 +/- 441 microseconds (N4, N = 13). Amplitudes ranged from 3.72 +/- 1.51 microV (P1/N1, N = 18) to 1.49 +/- 0.77 microV (P3/N3, N = 16). Latency-intensity (LI) slopes ranged from -38.7 +/- 7.3 microseconds dB-1 (P1, N = 18) to -71.6 +/- 21.9 microseconds dB-1 (N3, N = 15) and amplitude-intensity (AI) slopes ranged from 0.20 +/- 0.08 microV dB-1 (P1/N1, N = 18) to 0.07 +/- 0.04 microV dB-1 (P3/N3, N = 11). The mean response threshold across all animals was -21.83 +/- 3.34 dB re: 1.0 g ms-1 (N = 18). Responses remained after cochlear extirpation showing that they could not depend critically on cochlear activity. Responses were eliminated by destruction of the vestibular end organs, thus showing that responses depended critically and specifically on the vestibular system. The results demonstrate that the responses are vestibular and the findings provide a scientific basis for using vestibular responses to evaluate vestibular function through ontogeny and senescence in the quail.

Diagnostic value of conventional visual evoked potentials applied to patients with multiple sclerosis.

PubMed

Balnytė, Renata; Ulozienė, Ingrida; Rastenytė, Daiva; Vaitkus, Antanas; Malcienė, Lina; Laučkaitė, Kristina

2011-01-01

The aim of this study was to determine the sensitivity and specificity of this classical technique employed at the Hospital of Lithuanian University of Health Sciences for the patients with multiple sclerosis and to assess its possible correlations with affected neurological systems. Pattern shift visual evoked potentials were recorded in 63 patients with multiple sclerosis, 17 (27%) of whom had a history of optic neuritis, and in 63 control patients with other neurological diseases. The latencies and amplitudes of P100 were measured. In total, 126 patients were referred to the inpatient department of neurology for differential diagnosis of demyelinating disorders between January and December of 2007. Abnormalities of visual evoked potentials were observed by 73% more frequently in patients with multiple sclerosis than in control patients (α=0.05, β<0.01). The combined monocular/interocular test showed a specificity of 90.5% and a sensitivity of 82.5%. The probability of an affection of the pyramidal system was 5 times greater (95% CI, 2.2-11.0; P<0.01) and the probability of the optic pathways involvement was 4.8 times greater (95% CI, 1.9-11.9; P<0.01) in patients with multiple sclerosis than in controls. Conventional visual evoked potentials must be reappraised in light of their diagnostic value in multiple sclerosis given their high diagnostic efficiency, relatively easy, short, and cheap implementation, and easy availability in everyday clinical practice.

Neural time course of visually enhanced echo suppression.

PubMed

Bishop, Christopher W; London, Sam; Miller, Lee M

2012-10-01

Auditory spatial perception plays a critical role in day-to-day communication. For instance, listeners utilize acoustic spatial information to segregate individual talkers into distinct auditory "streams" to improve speech intelligibility. However, spatial localization is an exceedingly difficult task in everyday listening environments with numerous distracting echoes from nearby surfaces, such as walls. Listeners' brains overcome this unique challenge by relying on acoustic timing and, quite surprisingly, visual spatial information to suppress short-latency (1-10 ms) echoes through a process known as "the precedence effect" or "echo suppression." In the present study, we employed electroencephalography (EEG) to investigate the neural time course of echo suppression both with and without the aid of coincident visual stimulation in human listeners. We find that echo suppression is a multistage process initialized during the auditory N1 (70-100 ms) and followed by space-specific suppression mechanisms from 150 to 250 ms. Additionally, we find a robust correlate of listeners' spatial perception (i.e., suppressing or not suppressing the echo) over central electrode sites from 300 to 500 ms. Contrary to our hypothesis, vision's powerful contribution to echo suppression occurs late in processing (250-400 ms), suggesting that vision contributes primarily during late sensory or decision making processes. Together, our findings support growing evidence that echo suppression is a slow, progressive mechanism modifiable by visual influences during late sensory and decision making stages. Furthermore, our findings suggest that audiovisual interactions are not limited to early, sensory-level modulations but extend well into late stages of cortical processing.

Resilience to the contralateral visual field bias as a window into object representations

PubMed Central

Garcea, Frank E.; Kristensen, Stephanie; Almeida, Jorge; Mahon, Bradford Z.

2016-01-01

Viewing images of manipulable objects elicits differential blood oxygen level-dependent (BOLD) contrast across parietal and dorsal occipital areas of the human brain that support object-directed reaching, grasping, and complex object manipulation. However, it is unknown which object-selective regions of parietal cortex receive their principal inputs from the ventral object-processing pathway and which receive their inputs from the dorsal object-processing pathway. Parietal areas that receive their inputs from the ventral visual pathway, rather than from the dorsal stream, will have inputs that are already filtered through object categorization and identification processes. This predicts that parietal regions that receive inputs from the ventral visual pathway should exhibit object-selective responses that are resilient to contralateral visual field biases. To test this hypothesis, adult participants viewed images of tools and animals that were presented to the left or right visual fields during functional magnetic resonance imaging (fMRI). We found that the left inferior parietal lobule showed robust tool preferences independently of the visual field in which tool stimuli were presented. In contrast, a region in posterior parietal/dorsal occipital cortex in the right hemisphere exhibited an interaction between visual field and category: tool-preferences were strongest contralateral to the stimulus. These findings suggest that action knowledge accessed in the left inferior parietal lobule operates over inputs that are abstracted from the visual input and contingent on analysis by the ventral visual pathway, consistent with its putative role in supporting object manipulation knowledge. PMID:27160998

Nimodipine-induced hypotension but not nitroglycerin-induced hypotension preserves long- and short-term memory in adult mice.

PubMed

Haile, Michael; Galoyan, Samuel; Li, Yong-Sheng; Cohen, Barry H; Quartermain, David; Blanck, Thomas; Bekker, Alex

2012-05-01

Acute hypotension may be implicated in cognitive dysfunction. L-type calcium channel blockers in the setting of hypoxia are protective of learning and memory. We tested the hypothesis that hypotension induced by nimodipine (NIMO) and nicardipine (NICA) would be protective of long- and short-term memory compared to hypotension induced by nitroglycerin (NTG). Forty Swiss-Webster mice (30 to 35 g, 6 to 8 weeks) were randomized into 4 groups for i.p. injection immediately after passive avoidance (PA) learning on day 0: (1) NTG (30 mg/kg); (2) NICA (40 mg/kg); (3) NIMO (40 mg/kg); and (4) saline. PA training latencies (seconds) were recorded for entry from a suspended platform into a Plexiglas tube where a shock (0.3 mA; 2-second duration) was automatically delivered. On day 2 latencies were recorded during a testing trial during which no shock was delivered. Latencies >900 seconds were assigned this value. Lower testing latency is indicative of an impairment of long-term associative memory. Forty-nine additional mice were randomized into similar groups for object recognition testing (ORT) and given i.p. injections on day 0. ORT measures short-term memory by exploiting the tendency of mice to prefer novel objects where a familiar object is present. On day 5 during training, 2 identical objects were placed in a circular arena and mice explored both for 15 minutes. A testing trial was conducted 1 hour later for 3 minutes after a novel object replaced a familiar one. Mice with intact memory spend about 65% of the time exploring the novel object. Mice with impaired memory devote equal time to each object. Recognition index (RI) is defined as the ratio of time spent exploring the novel object to time spent exploring both objects was the measure of memory. Mean arterial blood pressure (MAP), cerebral bloodflow, and body and brain oxygenation (PO(2)) studies were done in separate groups of mice to determine the dosages for matched degrees of hypotension and the physiological profile of each treatment. The median PA latencies for the different conditions were as follows: NTG (219.5 ± 93.5 second semi-interquartile range [SIQR]), NICA (372.5 ± 75.5 second SIQR), NIMO (540 ± 200 second SIQR) and saline (804 ± 257.5 second SIQR). Rank methods were used to analyze the PA latencies for significant differences. NTG latency was significantly shorter than NIMO latency (P = 0.012) and saline latency (P = 0.006), but not NICA latency (P = 0.126). ORT RI values showed a similar pattern. We found that NTG RI (47.2 ± 5.9% SEM) was different from NIMO RI (60.2 ± 4.6% SEM, P = 0.031) and different from saline RI (66.9 + 3.7% SEM, P = 0.006). Physiological experiments showed that MAP decreased to 45 to 50 mm Hg in all animals who became minimally responsive to external stimuli within 10 to 15 minutes of injection. Intergroup differences for MAP, body and brain oxygenation, and cerebral bloodflow were not statistically significant. Acute hypotension induced by NIMO was protective of 2 categories of memory formation relevant to the clinical posttreatment period. Both immediate long-term associative memory consolidation as measured by the PA learning paradigm and delayed short-term working memory function as measured by the ORT paradigm were significantly improved compared to matched levels of hypotension induced by NTG. These results indicate the utility of further investigation of l-type calcium channel blockers as a potential means of preserving cognition in the setting of hypotensive and low flow states.

Passive adaptation to stress in adulthood after short-term social instability stress during adolescence in mice.

PubMed

de Lima, A P N; Massoco, C O

2017-05-01

This study reports that short-term social instability stress (SIS) in adolescence increases passive-coping in adulthood in male mice. Short-term SIS decreased the latency of immobility and increased the frequency and time of immobility in tail suspension test. These findings support the hypothesis that adolescent stress can induce a passive adaptation to stress in adulthood, even if it is a short period of stress.

The adequate stimulus for avian short latency vestibular responses to linear translation

NASA Technical Reports Server (NTRS)

Jones, T. A.; Jones, S. M.; Colbert, S.

1998-01-01

Transient linear acceleration stimuli have been shown to elicit eighth nerve vestibular compound action potentials in birds and mammals. The present study was undertaken to better define the nature of the adequate stimulus for neurons generating the response in the chicken (Gallus domesticus). In particular, the study evaluated the question of whether the neurons studied are most sensitive to the maximum level of linear acceleration achieved or to the rate of change in acceleration (da/dt, or jerk). To do this, vestibular response thresholds were measured as a function of stimulus onset slope. Traditional computer signal averaging was used to record responses to pulsed linear acceleration stimuli. Stimulus onset slope was systematically varied. Acceleration thresholds decreased with increasing stimulus onset slope (decreasing stimulus rise time). When stimuli were expressed in units of jerk (g/ms), thresholds were virtually constant for all stimulus rise times. Moreover, stimuli having identical jerk magnitudes but widely varying peak acceleration levels produced virtually identical responses. Vestibular response thresholds, latencies and amplitudes appear to be determined strictly by stimulus jerk magnitudes. Stimulus attributes such as peak acceleration or rise time alone do not provide sufficient information to predict response parameter quantities. Indeed, the major response parameters were shown to be virtually independent of peak acceleration levels or rise time when these stimulus features were isolated and considered separately. It is concluded that the neurons generating short latency vestibular evoked potentials do so as "jerk encoders" in the chicken. Primary afferents classified as "irregular", and which traditionally fall into the broad category of "dynamic" or "phasic" neurons, would seem to be the most likely candidates for the neural generators of short latency vestibular compound action potentials.

Parameters of semantic multisensory integration depend on timing and modality order among people on the autism spectrum: evidence from event-related potentials.

PubMed

Russo, N; Mottron, L; Burack, J A; Jemel, B

2012-07-01

Individuals with autism spectrum disorders (ASD) report difficulty integrating simultaneously presented visual and auditory stimuli (Iarocci & McDonald, 2006), albeit showing enhanced perceptual processing of unisensory stimuli, as well as an enhanced role of perception in higher-order cognitive tasks (Enhanced Perceptual Functioning (EPF) model; Mottron, Dawson, Soulières, Hubert, & Burack, 2006). Individuals with an ASD also integrate auditory-visual inputs over longer periods of time than matched typically developing (TD) peers (Kwakye, Foss-Feig, Cascio, Stone & Wallace, 2011). To tease apart the dichotomy of both extended multisensory processing and enhanced perceptual processing, we used behavioral and electrophysiological measurements of audio-visual integration among persons with ASD. 13 TD and 14 autistics matched on IQ completed a forced choice multisensory semantic congruence task requiring speeded responses regarding the congruence or incongruence of animal sounds and pictures. Stimuli were presented simultaneously or sequentially at various stimulus onset asynchronies in both auditory first and visual first presentations. No group differences were noted in reaction time (RT) or accuracy. The latency at which congruent and incongruent waveforms diverged was the component of interest. In simultaneous presentations, congruent and incongruent waveforms diverged earlier (circa 150 ms) among persons with ASD than among TD individuals (around 350 ms). In sequential presentations, asymmetries in the timing of neuronal processing were noted in ASD which depended on stimulus order, but these were consistent with the nature of specific perceptual strengths in this group. These findings extend the Enhanced Perceptual Functioning Model to the multisensory domain, and provide a more nuanced context for interpreting ERP findings of impaired semantic processing in ASD. Copyright © 2012 Elsevier Ltd. All rights reserved.

Adaptation of the cortical somatosensory evoked potential following pulsed pneumatic stimulation of the lower face in adults.

PubMed

Custead, Rebecca; Oh, Hyuntaek; Rosner, Austin Oder; Barlow, Steven

2015-10-05

Cortical adaptation to sustained sensory input is a pervasive form of short-term plasticity in neurological systems. Its role in sensory perception in health and disease, or predicting long-term plastic changes resulting from sensory training offers insight into the mechanisms of somatosensory and sensorimotor processing. A 4-channel electroencephalography (EEG) recording montage was placed bilaterally (C3-P3, C4-P4, F7-P3, F8-P4) to characterize the short-term effects of pulsed pneumatic orofacial stimulation on the cortical somatosensory evoked potential (cSEP) in twenty neurotypical adults (mean age=21±2.88 years). A servo-controlled pneumatic amplifier was used to deliver a repetitive series of pneumatic pulse trains (six 50-ms pulses, 5-second intertrain interval) through a linked pair of custom acetal homopolymer probes (aka TAC-Cells) adhered to the nonglabrous skin of the lower face proximal to the right oral angle to synchronously activate mechanoreceptive afferents in the trigeminal nerve. Blocks of pulse trains were counterbalanced among participants and delivered at two rates, 2 and 4Hz. TAC-Cell stimulation of the lower face consistently evoked a series of cSEPs at P7, N20, P28, N38, P75, N85, and P115. The spatial organization and adaptation of the evoked cSEP was dependent on stimulus pulse index (1-6 within the pulse train, p=.012), frequency of stimulus presentation (2 vs 4Hz, p<.001), component (P7-P115, p<.001), and recording montage (channels 1-4, p<.001). Early component latencies (P7-N20) were highly stable in polarity (sign) and latency, and consistent with putative far-field generators (e.g., trigeminal brainstem, ventroposteromedial thalamus). Copyright © 2015 Elsevier B.V. All rights reserved.

Hierarchical neural network model of the visual system determining figure/ground relation

NASA Astrophysics Data System (ADS)

Kikuchi, Masayuki

2017-07-01

One of the most important functions of the visual perception in the brain is figure/ground interpretation from input images. Figural region in 2D image corresponding to object in 3D space are distinguished from background region extended behind the object. Previously the author proposed a neural network model of figure/ground separation constructed on the standpoint that local geometric features such as curvatures and outer angles at corners are extracted and propagated along input contour in a single layer network (Kikuchi & Akashi, 2001). However, such a processing principle has the defect that signal propagation requires manyiterations despite the fact that actual visual system determines figure/ground relation within the short period (Zhou et al., 2000). In order to attain speed-up for determining figure/ground, this study incorporates hierarchical architecture into the previous model. This study confirmed the effect of the hierarchization as for the computation time by simulation. As the number of layers increased, the required computation time reduced. However, such speed-up effect was saturatedas the layers increased to some extent. This study attempted to explain this saturation effect by the notion of average distance between vertices in the area of complex network, and succeeded to mimic the saturation effect by computer simulation.

Influence of education level on design-induced N170 and P300 components of event related potentials in the human brain.

PubMed

Begum, Tahamina; Reza, Faruque; Ahmed, Izmer; Abdullah, Jafri Malin

2014-03-01

Simple geometric and organic shapes and their arrangement are being used in different neuropsychology tests for the assessment of cognitive function, special memory and also for the therapy purpose in different patient groups. Until now there is no electrophysiological evidence of cognitive function determination for simple geometric, organic shapes and their arrangement. Then the main objective of this study is to know the cortical processing and amplitude, latency of visual induced N170 and P300 event related potential components on different geometric, organic shapes and their arrangement and different educational influence on it, which is worthwhile to know for the early and better treatment for those patient groups. While education influenced on cognitive function by using auditory oddball task, little is known about the influence of education on cognitive function induced by visual attention task in case of the choice of geometric, organic shapes and their arrangements. Using a 128-electrode sensor net, we studied the responses of the choice of the different geometric and organic shapes randomly in experiment 1 and their arrangements in experiment 2 in the high, medium and low education groups. In both experiments, subjects push the button "1" or "2" if like or dislike, respectively. Total 45 healthy subjects (15 in each group) were recruited. ERPs were measured from 11 electrode sites and analyzed to see the evoked N170/N240 and P300 ERP components. There were no differences between like and dislike in amplitudes even in latencies in every stimulus in both experiments. We fixed geometric shapes and organic shapes stimuli only, not like and dislike. Upon the stimulus types, N170 ERP component was found instead of N240, in occipito-temporal (T5, T6, O1 and O2) locations where the amplitude is the highest at O2 location and P300 was distributed in the central (Cz and Pz) locations in both experiments in all groups. In experiment 1, significant low amplitude and non-significant larger latency of the N170 component are found out at O1 location for both stimuli in low education group comparing medium education groups, but in experiment 2, there is no significant difference between stimuli among groups in amplitude and latency. In both experiments, P300 component was found in Cz and Pz locations though the amplitudes are higher at Cz than Pz areas. In experiment 1, medium education group evoked significantly (geometric shape stimuli, P = 0.05; organic shape stimuli, P = 0.02) higher amplitude of P300 component comparing low education group at Cz location. Whereas, there is no significant difference of amplitudes among groups across stimuli in Cz and Pz locations in experiment 2. Latencies have no significant differences in both experiments among groups also, but longer latency are found in low education group at Cz location comparing medium education group, though not significant. We conclude that simple geometric shapes, organic shapes and their arrangements evoked visual N170 component at temporo-occipital areas with right lateralization and P300 ERP component at centro-parietal areas. Significant low amplitude of N170 and P300 ERP components and longer latencies during different shape stimuli in low education group prove that, low education significantly influence on visual cognitive functions in low education group.

A comparative study on long-term evoked auditory and visual potential responses between Schizophrenic patients and normal subjects

PubMed Central

2011-01-01

Background The electrical signals measuring method is recommended to examine the relationship between neuronal activities and measure with the event related potentials (ERPs) during an auditory and a visual oddball paradigm between schizophrenic patients and normal subjects. The aim of this study is to discriminate the activation changes of different stimulations evoked by auditory and visual ERPs between schizophrenic patients and normal subjects. Methods Forty-three schizophrenic patients were selected as experimental group patients, and 40 healthy subjects with no medical history of any kind of psychiatric diseases, neurological diseases, or drug abuse, were recruited as a control group. Auditory and visual ERPs were studied with an oddball paradigm. All the data were analyzed by SPSS statistical software version 10.0. Results In the comparative study of auditory and visual ERPs between the schizophrenic and healthy patients, P300 amplitude at Fz, Cz, and Pz and N100, N200, and P200 latencies at Fz, Cz, and Pz were shown significantly different. The cognitive processing reflected by the auditory and the visual P300 latency to rare target stimuli was probably an indicator of the cognitive function in schizophrenic patients. Conclusions This study shows the methodology of application of auditory and visual oddball paradigm identifies task-relevant sources of activity and allows separation of regions that have different response properties. Our study indicates that there may be slowness of automatic cognitive processing and controlled cognitive processing of visual ERPs compared to auditory ERPs in schizophrenic patients. The activation changes of visual evoked potentials are more regionally specific than auditory evoked potentials. PMID:21542917

[Effect of acupuncture on pattern-visual evoked potential in rats with monocular visual deprivation].

PubMed

Yan, Xing-Ke; Dong, Li-Li; Liu, An-Guo; Wang, Jun-Yan; Ma, Chong-Bing; Zhu, Tian-Tian

2013-08-01

To explore electrophysiology mechanism of acupuncture for treatment and prevention of visual deprivation effect. Eighteen healthy 15-day Evans rats were randomly divided into a normal group, a model group and an acupuncture group, 6 rats in each one. Deprivation amblyopia model was established by monocular eyelid suture in the model group and acupuncture group. Acupuncture was applied at "Jingming" (BL 1), "Chengqi" (ST 1), "Qiuhou" (EX-HN 7) and "Cuanzhu" (BL 2) in the acupuncture group. The bilateral acupoints were selected alternately, one side for a day, and totally 14 days were required. The effect of acupuncture on visual evoked potential in different spatial frequencies was observed. Under three different kinds of spatial frequencies of 2 X 2, 4 X 4 and 8 X 8, compared with normal group, there was obvious visual deprivation effect in the model group where P1 peak latency was delayed (P<0.01) while N1 -P1 amplitude value was decreased (P<0.01). Compared with model group, P1 peak latency was obviously ahead of time (P<0.01) while N1-P1 amplitude value was increased (P<0.01) in the acupuncture group, there was no statistical significance compared with normal group (P>0.05). Under spatial frequency of 4 X 4, N1-P1 amplitude value was maximum in the normal group and acupuncture group. With this spatial frequency the rat's eye had best resolving ability, indicating it could be the best spatial frequency for rat visual system. The visual system has obvious electrophysiology plasticity in sensitive period. Acupuncture treatment could adjust visual deprivation-induced suppression and slow of visual response in order to antagonism deprivation effect.

The behaviour of the long-latency stretch reflex in patients with Parkinson's disease

PubMed Central

Rothwell, Jc; Obeso, Ja; Traub, Mm; Marsden, Cd

1983-01-01

The size of the long-latency stretch reflex was measured in a proximal (triceps) and distal (flexor pollicis longus) muscle in 47 patients with Parkinson's disease, and was compared with that seen in a group of 12 age-matched normal control subjects. The patients were classified clinically into four groups according to the degree of rigidity at the elbow or tremor. Stretch reflexes were evaluated while the subject was exerting a small force against a constant preload supplied by a torque motor, and the size of the reflex response was measured as fractional increase over basal levels of activity. When stretches were given at random intervals by increasing the force exerted by the motor by a factor of 2 or 3, there was a clear trend for the more severely affected patients to have larger long latency responses in the triceps muscle, although there was no change in the size of the short-latency, spinal component of the response. In contrast, there was no change in the size of the long-latency response of the flexor pollicis longus in any group of patients with Parkinson's disease. Despite any differences in reflex size, the inherent muscle stiffness of both muscles appeared to be normal in all groups of patients with Parkinson's disease, since the displacement trajectory of the limb following the force increase was the same as control values in the short (25 ms) period before reflex compensation could intervene. In 20 of the patients and in seven of the control subjects, servo-controlled, ramp positional disturbances were given to the thumb. Up to a velocity of 300°/s, the size of the long-latency stretch reflex was proportional to the log velocity of stretch. This technique revealed, in both moderately and severely rigid patients, increases in the reflex sensitivity of the flexor pollicis longus, which had not been clear using step torque stretches alone. However, whether using ramp or step displacements, long latency stretch reflex gain was not closely related to rigidity; reflex size was within the normal range in many patients with severe rigidity. Enhanced long latency stretch reflexes thus contribute to, but may not be solely responsible for, rigidity in Parkinson's disease. PMID:6842198

VTK-m: Accelerating the Visualization Toolkit for Massively Threaded Architectures

DOE PAGES

Moreland, Kenneth; Sewell, Christopher; Usher, William; ...

2016-05-09

Here, one of the most critical challenges for high-performance computing (HPC) scientific visualization is execution on massively threaded processors. Of the many fundamental changes we are seeing in HPC systems, one of the most profound is a reliance on new processor types optimized for execution bandwidth over latency hiding. Our current production scientific visualization software is not designed for these new types of architectures. To address this issue, the VTK-m framework serves as a container for algorithms, provides flexible data representation, and simplifies the design of visualization algorithms on new and future computer architecture.

VTK-m: Accelerating the Visualization Toolkit for Massively Threaded Architectures

DOE PAGES

Moreland, Kenneth; Sewell, Christopher; Usher, William; ...

2016-05-09

Execution on massively threaded processors is one of the most critical challenges for high-performance computing (HPC) scientific visualization. Of the many fundamental changes we are seeing in HPC systems, one of the most profound is a reliance on new processor types optimized for execution bandwidth over latency hiding. Moreover, our current production scientific visualization software is not designed for these new types of architectures. In order to address this issue, the VTK-m framework serves as a container for algorithms, provides flexible data representation, and simplifies the design of visualization algorithms on new and future computer architecture.

Invariant visual object recognition: a model, with lighting invariance.

PubMed

Rolls, Edmund T; Stringer, Simon M

2006-01-01

How are invariant representations of objects formed in the visual cortex? We describe a neurophysiological and computational approach which focusses on a feature hierarchy model in which invariant representations can be built by self-organizing learning based on the statistics of the visual input. The model can use temporal continuity in an associative synaptic learning rule with a short term memory trace, and/or it can use spatial continuity in Continuous Transformation learning. The model of visual processing in the ventral cortical stream can build representations of objects that are invariant with respect to translation, view, size, and in this paper we show also lighting. The model has been extended to provide an account of invariant representations in the dorsal visual system of the global motion produced by objects such as looming, rotation, and object-based movement. The model has been extended to incorporate top-down feedback connections to model the control of attention by biased competition in for example spatial and object search tasks. The model has also been extended to account for how the visual system can select single objects in complex visual scenes, and how multiple objects can be represented in a scene.

Approximate entropy analysis of event-related potentials in patients with early vascular dementia.

PubMed

Xu, Jin; Sheng, Hengsong; Lou, Wutao; Zhao, Songzhen

2012-06-01

This study investigated differences in event-related potential (ERP) parameters among early vascular dementia (VD) patients, healthy elder controls (ECs), and young controls (YCs). A visual "oddball" color identification task was performed while individuals' electroencephalograms (EEGs) were recorded. Approximate entropy (ApEn), a nonlinear measure, along with P300 latencies and amplitudes were used to analyze ERP data and compare these three groups. The patients with VD showed more complex ERP waveforms and higher ApEn values than did ECs while performing the visual task. It was further found that patients with VD showed reduced P300 amplitudes and increased latencies. The results indicate that patients with VD have fewer attention resources to devote to processing stimuli, lower speed of stimulus classification, and lower synchrony in their cortical activity during the response period. We suggest that ApEn, as a measure of ERP complexity, is a promising marker for early diagnosis of VD.

Evaluating the decision accuracy and speed of clinical data visualizations.

PubMed

Pieczkiewicz, David S; Finkelstein, Stanley M

2010-01-01

Clinicians face an increasing volume of biomedical data. Assessing the efficacy of systems that enable accurate and timely clinical decision making merits corresponding attention. This paper discusses the multiple-reader multiple-case (MRMC) experimental design and linear mixed models as means of assessing and comparing decision accuracy and latency (time) for decision tasks in which clinician readers must interpret visual displays of data. These tools can assess and compare decision accuracy and latency (time). These experimental and statistical techniques, used extensively in radiology imaging studies, offer a number of practical and analytic advantages over more traditional quantitative methods such as percent-correct measurements and ANOVAs, and are recommended for their statistical efficiency and generalizability. An example analysis using readily available, free, and commercial statistical software is provided as an appendix. While these techniques are not appropriate for all evaluation questions, they can provide a valuable addition to the evaluative toolkit of medical informatics research.

Visual hallucinations and pontine demyelination in a child: possible REM dissociation?

PubMed

Vita, Maria Gabriella; Batocchi, Anna Paola; Dittoni, Serena; Losurdo, Anna; Cianfoni, Alessandro; Stefanini, Maria Chiara; Vollono, Catello; Della Marca, Giacomo; Mariotti, Paolo

2008-12-15

An 11 year-old-boy acutely developed complex visual and acoustic hallucinations. Hallucinations, consisting of visions of a threatening, evil character of the Harry Potter saga, persisted for 3 days. Neurological and psychiatric examinations were normal. Ictal EEG was negative. MRI documented 3 small areas of hyperintense signal in the brainstem, along the paramedian and lateral portions of pontine tegmentum, one of which showed post-contrast enhancement. These lesions were likely of inflammatory origin, and treatment with immunoglobulins was started. Polysomnography was normal, multiple sleep latency test showed a mean sleep latency of 8 minutes, with one sleep-onset REM period. The pontine tegmentum is responsible for REM sleep regulation, and contains definite "REM-on" and "REM-off" regions. The anatomical distribution of the lesions permits us to hypothesize that hallucinations in this boy were consequent to a transient impairment of REM sleep inhibitory mechanisms, with the appearance of dream-like hallucinations during wake.

Event-related potentials to visual, auditory, and bimodal (combined auditory-visual) stimuli.

PubMed

Isoğlu-Alkaç, Ummühan; Kedzior, Karina; Keskindemirci, Gonca; Ermutlu, Numan; Karamursel, Sacit

2007-02-01

The purpose of this study was to investigate the response properties of event related potentials to unimodal and bimodal stimulations. The amplitudes of N1 and P2 were larger during bimodal evoked potentials (BEPs) than auditory evoked potentials (AEPs) in the anterior sites and the amplitudes of P1 were larger during BEPs than VEPs especially at the parieto-occipital locations. Responses to bimodal stimulation had longer latencies than responses to unimodal stimulation. The N1 and P2 components were larger in amplitude and longer in latency during the bimodal paradigm and predominantly occurred at the anterior sites. Therefore, the current bimodal paradigm can be used to investigate the involvement and location of specific neural generators that contribute to higher processing of sensory information. Moreover, this paradigm may be a useful tool to investigate the level of sensory dysfunctions in clinical samples.

Asymmetric temporal integration of layer 4 and layer 2/3 inputs in visual cortex.

PubMed

Hang, Giao B; Dan, Yang

2011-01-01

Neocortical neurons in vivo receive concurrent synaptic inputs from multiple sources, including feedforward, horizontal, and feedback pathways. Layer 2/3 of the visual cortex receives feedforward input from layer 4 and horizontal input from layer 2/3. Firing of the pyramidal neurons, which carries the output to higher cortical areas, depends critically on the interaction of these pathways. Here we examined synaptic integration of inputs from layer 4 and layer 2/3 in rat visual cortical slices. We found that the integration is sublinear and temporally asymmetric, with larger responses if layer 2/3 input preceded layer 4 input. The sublinearity depended on inhibition, and the asymmetry was largely attributable to the difference between the two inhibitory inputs. Interestingly, the asymmetric integration was specific to pyramidal neurons, and it strongly affected their spiking output. Thus via cortical inhibition, the temporal order of activation of layer 2/3 and layer 4 pathways can exert powerful control of cortical output during visual processing.

Two-Stage Processing of Sounds Explains Behavioral Performance Variations due to Changes in Stimulus Contrast and Selective Attention: An MEG Study

PubMed Central

Kauramäki, Jaakko; Jääskeläinen, Iiro P.; Hänninen, Jarno L.; Auranen, Toni; Nummenmaa, Aapo; Lampinen, Jouko; Sams, Mikko

2012-01-01

Selectively attending to task-relevant sounds whilst ignoring background noise is one of the most amazing feats performed by the human brain. Here, we studied the underlying neural mechanisms by recording magnetoencephalographic (MEG) responses of 14 healthy human subjects while they performed a near-threshold auditory discrimination task vs. a visual control task of similar difficulty. The auditory stimuli consisted of notch-filtered continuous noise masker sounds, and of 1020-Hz target tones occasionally () replacing 1000-Hz standard tones of 300-ms duration that were embedded at the center of the notches, the widths of which were parametrically varied. As a control for masker effects, tone-evoked responses were additionally recorded without masker sound. Selective attention to tones significantly increased the amplitude of the onset M100 response at 100 ms to the standard tones during presence of the masker sounds especially with notches narrower than the critical band. Further, attention modulated sustained response most clearly at 300–400 ms time range from sound onset, with narrower notches than in case of the M100, thus selectively reducing the masker-induced suppression of the tone-evoked response. Our results show evidence of a multiple-stage filtering mechanism of sensory input in the human auditory cortex: 1) one at early (100 ms) latencies bilaterally in posterior parts of the secondary auditory areas, and 2) adaptive filtering of attended sounds from task-irrelevant background masker at longer latency (300 ms) in more medial auditory cortical regions, predominantly in the left hemisphere, enhancing processing of near-threshold sounds. PMID:23071654

Latency of modality-specific reactivation of auditory and visual information during episodic memory retrieval.

PubMed

Ueno, Daisuke; Masumoto, Kouhei; Sutani, Kouichi; Iwaki, Sunao

2015-04-15

This study used magnetoencephalography (MEG) to examine the latency of modality-specific reactivation in the visual and auditory cortices during a recognition task to determine the effects of reactivation on episodic memory retrieval. Nine right-handed healthy young adults participated in the experiment. The experiment consisted of a word-encoding phase and two recognition phases. Three encoding conditions were included: encoding words alone (word-only) and encoding words presented with either related pictures (visual) or related sounds (auditory). The recognition task was conducted in the MEG scanner 15 min after the completion of the encoding phase. After the recognition test, a source-recognition task was given, in which participants were required to choose whether each recognition word was not presented or was presented with which information during the encoding phase. Word recognition in the auditory condition was higher than that in the word-only condition. Confidence-of-recognition scores (d') and the source-recognition test showed superior performance in both the visual and the auditory conditions compared with the word-only condition. An equivalent current dipoles analysis of MEG data indicated that higher equivalent current dipole amplitudes in the right fusiform gyrus occurred during the visual condition and in the superior temporal auditory cortices during the auditory condition, both 450-550 ms after onset of the recognition stimuli. Results suggest that reactivation of visual and auditory brain regions during recognition binds language with modality-specific information and that reactivation enhances confidence in one's recognition performance.

A multi-pathway hypothesis for human visual fear signaling

PubMed Central

Silverstein, David N.; Ingvar, Martin

2015-01-01

A hypothesis is proposed for five visual fear signaling pathways in humans, based on an analysis of anatomical connectivity from primate studies and human functional connectvity and tractography from brain imaging studies. Earlier work has identified possible subcortical and cortical fear pathways known as the “low road” and “high road,” which arrive at the amygdala independently. In addition to a subcortical pathway, we propose four cortical signaling pathways in humans along the visual ventral stream. All four of these traverse through the LGN to the visual cortex (VC) and branching off at the inferior temporal area, with one projection directly to the amygdala; another traversing the orbitofrontal cortex; and two others passing through the parietal and then prefrontal cortex, one excitatory pathway via the ventral-medial area and one regulatory pathway via the ventral-lateral area. These pathways have progressively longer propagation latencies and may have progressively evolved with brain development to take advantage of higher-level processing. Using the anatomical path lengths and latency estimates for each of these five pathways, predictions are made for the relative processing times at selective ROIs and arrival at the amygdala, based on the presentation of a fear-relevant visual stimulus. Partial verification of the temporal dynamics of this hypothesis might be accomplished using experimental MEG analysis. Possible experimental protocols are suggested. PMID:26379513

Reward-Based Learning Drives Rapid Sensory Signals in Medial Prefrontal Cortex and Dorsal Hippocampus Necessary for Goal-Directed Behavior.

PubMed

Le Merre, Pierre; Esmaeili, Vahid; Charrière, Eloïse; Galan, Katia; Salin, Paul-A; Petersen, Carl C H; Crochet, Sylvain

2018-01-03

The neural circuits underlying learning and execution of goal-directed behaviors remain to be determined. Here, through electrophysiological recordings, we investigated fast sensory processing across multiple cortical areas as mice learned to lick a reward spout in response to a brief deflection of a single whisker. Sensory-evoked signals were absent from medial prefrontal cortex and dorsal hippocampus in naive mice, but developed with task learning and correlated with behavioral performance in mice trained in the detection task. The sensory responses in medial prefrontal cortex and dorsal hippocampus occurred with short latencies of less than 50 ms after whisker deflection. Pharmacological and optogenetic inactivation of medial prefrontal cortex or dorsal hippocampus impaired behavioral performance. Neuronal activity in medial prefrontal cortex and dorsal hippocampus thus appears to contribute directly to task performance, perhaps providing top-down control of learned, context-dependent transformation of sensory input into goal-directed motor output. Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.

Auditory stimuli elicit hippocampal neuronal responses during sleep

PubMed Central

Vinnik, Ekaterina; Antopolskiy, Sergey; Itskov, Pavel M.; Diamond, Mathew E.

2012-01-01

To investigate how hippocampal neurons code behaviorally salient stimuli, we recorded from neurons in the CA1 region of hippocampus in rats while they learned to associate the presence of sound with water reward. Rats learned to alternate between two reward ports at which, in 50% of the trials, sound stimuli were presented followed by water reward after a 3-s delay. Sound at the water port predicted subsequent reward delivery in 100% of the trials and the absence of sound predicted reward omission. During this task, 40% of recorded neurons fired differently according to which of the two reward ports the rat was visiting. A smaller fraction of neurons demonstrated onset response to sound/nosepoke (19%) and reward delivery (24%). When the sounds were played during passive wakefulness, 8% of neurons responded with short latency onset responses; 25% of neurons responded to sounds when they were played during sleep. During sleep the short-latency responses in hippocampus are intermingled with long lasting responses which in the current experiment could last for 1–2 s. Based on the current findings and the results of previous experiments we described the existence of two types of hippocampal neuronal responses to sounds: sound-onset responses with very short latency and longer-lasting sound-specific responses that are likely to be present when the animal is actively engaged in the task. PMID:22754507

Predicting Naming Latencies with an Analogical Model

ERIC Educational Resources Information Center

Chandler, Steve

2008-01-01

Skousen's (1989, Analogical modeling of language, Kluwer Academic Publishers, Dordrecht) Analogical Model (AM) predicts behavior such as spelling pronunciation by comparing the characteristics of a test item (a given input word) to those of individual exemplars in a data set of previously encountered items. While AM and other exemplar-based models…

Robotic goalie with 3 ms reaction time at 4% CPU load using event-based dynamic vision sensor

PubMed Central

Delbruck, Tobi; Lang, Manuel

2013-01-01

Conventional vision-based robotic systems that must operate quickly require high video frame rates and consequently high computational costs. Visual response latencies are lower-bound by the frame period, e.g., 20 ms for 50 Hz frame rate. This paper shows how an asynchronous neuromorphic dynamic vision sensor (DVS) silicon retina is used to build a fast self-calibrating robotic goalie, which offers high update rates and low latency at low CPU load. Independent and asynchronous per pixel illumination change events from the DVS signify moving objects and are used in software to track multiple balls. Motor actions to block the most “threatening” ball are based on measured ball positions and velocities. The goalie also sees its single-axis goalie arm and calibrates the motor output map during idle periods so that it can plan open-loop arm movements to desired visual locations. Blocking capability is about 80% for balls shot from 1 m from the goal even with the fastest-shots, and approaches 100% accuracy when the ball does not beat the limits of the servo motor to move the arm to the necessary position in time. Running with standard USB buses under a standard preemptive multitasking operating system (Windows), the goalie robot achieves median update rates of 550 Hz, with latencies of 2.2 ± 2 ms from ball movement to motor command at a peak CPU load of less than 4%. Practical observations and measurements of USB device latency are provided1. PMID:24311999

Visually Evoked Potential Markers of Concussion History in Patients with Convergence Insufficiency

PubMed Central

Poltavski, Dmitri; Lederer, Paul; Cox, Laurie Kopko

2017-01-01

ABSTRACT Purpose We investigated whether differences in the pattern visual evoked potentials exist between patients with convergence insufficiency and those with convergence insufficiency and a history of concussion using stimuli designed to differentiate between magnocellular (transient) and parvocellular (sustained) neural pathways. Methods Sustained stimuli included 2-rev/s, 85% contrast checkerboard patterns of 1- and 2-degree check sizes, whereas transient stimuli comprised 4-rev/s, 10% contrast vertical sinusoidal gratings with column width of 0.25 and 0.50 cycles/degree. We tested two models: an a priori clinical model based on an assumption of at least a minimal (beyond instrumentation’s margin of error) 2-millisecond lag of transient response latencies behind sustained response latencies in concussed patients and a statistical model derived from the sample data. Results Both models discriminated between concussed and nonconcussed groups significantly above chance (with 76% and 86% accuracy, respectively). In the statistical model, patients with mean vertical sinusoidal grating response latencies greater than 119 milliseconds to 0.25-cycle/degree stimuli (or mean vertical sinusoidal latencies >113 milliseconds to 0.50-cycle/degree stimuli) and mean vertical sinusoidal grating amplitudes of less than 14.75 mV to 0.50-cycle/degree stimuli were classified as having had a history of concussion. The resultant receiver operating characteristic curve for this model had excellent discrimination between the concussed and nonconcussed (area under the curve = 0.857; P < .01) groups with sensitivity of 0.92 and specificity of 0.80. Conclusions The results suggest a promising electrophysiological approach to identifying individuals with convergence insufficiency and a history of concussion. PMID:28609417

Occlusion therapy improves phase-alignment of the cortical response in amblyopia.

PubMed

Kelly, John P; Tarczy-Hornoch, Kristina; Herlihy, Erin; Weiss, Avery H

2015-09-01

The visual evoked potential (VEP) generated by the amblyopic visual system demonstrates reduced amplitude, prolonged latency, and increased variation in response timing (phase-misalignment). This study examined VEPs before and after occlusion therapy (OT) and whether phase-misalignment can account for the amblyopic VEP deficits. VEPs were recorded to 0.5-4cycles/degree gratings in 10 amblyopic children (2-6years age) before and after OT. Phase-misalignment was measured by Fourier analysis across a limited bandwidth. Signal-to-noise ratios (SNRs) were estimated from amplitude and phase synchrony in the Fourier domain. Responses were compared to VEPs corrected for phase-misalignment (individual epochs shifted in time to correct for the misalignment). Before OT, amblyopic eyes (AE) had significantly more phase-misalignment, latency prolongation, and lower SNR relative to the fellow eye. Phase-misalignment contributed significantly to low SNR but less so to latency delay in the AE. After OT, phase-alignment improved, SNR improved and latency shortened in the AE. Raw averaged waveforms from the AE improved after OT, primarily at higher spatial frequencies. Correcting for phase-misalignment in the AE sharpened VEP peak responses primarily at low spatial frequencies, but could not account for VEP waveform improvements in the AE after OT at higher spatial frequencies. In summary, VEP abnormalities from the AE are associated with phase-misalignment and reduced SNR possibly related to desynchronization of neuronal activity. The effect of OT on VEP responses is greater than that accounted for by phase-misalignment and SNR alone. Copyright © 2014 Elsevier Ltd. All rights reserved.

Electrical stimulation to the trigeminal proprioceptive fibres that innervate the mechanoreceptors in Müller's muscle induces involuntary reflex contraction of the frontalis muscles.

PubMed

Matsuo, Kiyoshi; Osada, Yoshiro; Ban, Ryokuya

2013-02-01

The levator and frontalis muscles lack interior muscle spindles, despite consisting of slow-twitch fibres that involuntarily sustain eyelid-opening and eyebrow-raising against gravity. To compensate for this anatomical defect, this study hypothetically proposes that initial voluntary contraction of the levator fast-twitch muscle fibres stretches the mechanoreceptors in Müller's muscle and evokes proprioception, which continuously induces reflex contraction of slow-twitch fibres of the levator and frontalis muscles. This study sought to determine whether unilateral transcutaneous electrical stimulation to the trigeminal proprioceptive fibres that innervate the mechanoreceptors in Müller's muscle could induce electromyographic responses in the frontalis muscles, with monitoring responses in the orbicularis oculi muscles. The study population included 27 normal subjects and 23 subjects with aponeurotic blepharoptosis, who displayed persistently raised eyebrows on primary gaze and light eyelid closure. The stimulation induced a short-latency response in the ipsilateral frontalis muscle of all subjects and long-latency responses in the bilateral frontalis muscles of normal subjects. However, it did not induce long-latency responses in the bilateral frontalis muscles of subjects with aponeurotic blepharoptosis. The orbicularis oculi muscles showed R1 and/or R2 responses. The stimulation might reach not only the proprioceptive fibres, but also other sensory fibres related to the blink or corneal reflex. The experimental system can provoke a monosynaptic short-latency response in the ipsilateral frontalis muscle, probably through the mesencephalic trigeminal proprioceptive neuron and the frontalis motor neuron, and polysynaptic long-latency responses in the bilateral frontalis muscles through an unknown pathway. The latter neural circuit appeared to be engaged by the circumstances of aponeurotic blepharoptosis.

Encoding of sound envelope transients in the auditory cortex of juvenile rats and adult rats.

PubMed

Lu, Qi; Jiang, Cuiping; Zhang, Jiping

2016-02-01

Accurate neural processing of time-varying sound amplitude and spectral information is vital for species-specific communication. During postnatal development, cortical processing of sound frequency undergoes progressive refinement; however, it is not clear whether cortical processing of sound envelope transients also undergoes age-related changes. We determined the dependence of neural response strength and first-spike latency on sound rise-fall time across sound levels in the primary auditory cortex (A1) of juvenile (P20-P30) rats and adult (8-10 weeks) rats. A1 neurons were categorized as "all-pass", "short-pass", or "mixed" ("all-pass" at high sound levels to "short-pass" at lower sound levels) based on the normalized response strength vs. rise-fall time functions across sound levels. The proportions of A1 neurons within each of the three categories in juvenile rats were similar to that in adult rats. In general, with increasing rise-fall time, the average response strength decreased and the average first-spike latency increased in A1 neurons of both groups. At a given sound level and rise-fall time, the average normalized neural response strength did not differ significantly between the two age groups. However, the A1 neurons in juvenile rats showed greater absolute response strength, longer first-spike latency compared to those in adult rats. In addition, at a constant sound level, the average first-spike latency of juvenile A1 neurons was more sensitive to changes in rise-fall time. Our results demonstrate the dependence of the responses of rat A1 neurons on sound rise-fall time, and suggest that the response latency exhibit some age-related changes in cortical representation of sound envelope rise time. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effect of Power Point Enhanced Teaching (Visual Input) on Iranian Intermediate EFL Learners' Listening Comprehension Ability

ERIC Educational Resources Information Center

Sehati, Samira; Khodabandehlou, Morteza

2017-01-01

The present investigation was an attempt to study on the effect of power point enhanced teaching (visual input) on Iranian Intermediate EFL learners' listening comprehension ability. To that end, a null hypothesis was formulated as power point enhanced teaching (visual input) has no effect on Iranian Intermediate EFL learners' listening…

Auditory event-related potentials in subcortical vascular cognitive impairment and in Alzheimer's disease.

PubMed

Muscoso, E G; Costanzo, E; Daniele, O; Maugeri, D; Natale, E; Caravaglios, G

2006-11-01

Few studies exist on ERPs and patients with subcortical vascular cognitive impairment (SVCI). This latter is a quite homogeneous subtype of vascular dementia whose cognitive profile is quite different from that of Alzheimer disease (AD). The present study aims at comparing the ERPs profile both in patients with SVCI and in patients with AD. ERPs and psychometric tests were collected from 39 healthy elderly controls, 51 patients with SVCI and 43 patients with AD. Subjects mentally count high pitched target tones that were randomly intermixed with low pitched frequent tones. We measured ERPs latencies (N1, P2, N2 and P3), and interpeak latencies (N1-P3, N1-P2, N1-N2). Grand averaged potentials in SVCI showed a significant increase of P3 latency. AD patients showed a prolongation of N1, P2, N2, P3 latencies. As far as interpeak latencies are concerned, SVCI patients showed a significant prolongation of N1-P3, AD patients had a significant increase of N1-N2, and N1-P3 intervals. When all patients were considered as a single group, correlation of neuropsychological tests scores showed a significant negative relationship between P300 latency and, respectively, Mini Mental Status Examination, auditive and visual span forward. In both groups, ERPs latency sensitivity, was low, whilst specificity values were quite high. Our finding suggest that these two dementing diseases have different electrophysiologic features that may be related to their specific underlying pathogenetic mechanism; in particular, we hypothesise that, differently from AD, P300 latency prolongation characterizes the early stage of SVCI. So, this ERPs approach could be helpful to detect early alterations of the attentional/working-memory functions in patients with subcortical ischaemic vascular disease.

Improved UT1 Predictions through Low-Latency VLBI Observations

DTIC Science & Technology

2010-03-14

J Geod (2010) 84:399–402 DOI 10.1007/s00190-010-0372-8 SHORT NOTE Improved UT1 predictions through low-latency VLBI observations Brian Luzum · Axel...polar motion and nutation on UT1 determinations from VLBI Intensive obser- vations. J Geod 82(12):863. doi:10.1007/s00190-008-0212-2 Ray JR, Carter WE...Behrend D (2007) The International VLBI Service for Geodesy and Astrometry (IVS): current capabilities and future prospects. J Geod 81(6–8):479. doi

The involvement of central attention in visual search is determined by task demands.

PubMed

Han, Suk Won

2017-04-01

Attention, the mechanism by which a subset of sensory inputs is prioritized over others, operates at multiple processing stages. Specifically, attention enhances weak sensory signal at the perceptual stage, while it serves to select appropriate responses or consolidate sensory representations into short-term memory at the central stage. This study investigated the independence and interaction between perceptual and central attention. To do so, I used a dual-task paradigm, pairing a four-alternative choice task with a visual search task. The results showed that central attention for response selection was engaged in perceptual processing for visual search when the number of search items increased, thereby increasing the demand for serial allocation of focal attention. By contrast, central attention and perceptual attention remained independent as far as the demand for serial shifting of focal attention remained constant; decreasing stimulus contrast or increasing the set size of a parallel search did not evoke the involvement of central attention in visual search. These results suggest that the nature of concurrent visual search process plays a crucial role in the functional interaction between two different types of attention.

Functional brain development in growth-restricted and constitutionally small fetuses: a fetal magnetoencephalography case-control study.

PubMed

Morin, E C; Schleger, F; Preissl, H; Braendle, J; Eswaran, H; Abele, H; Brucker, S; Kiefer-Schmidt, I

2015-08-01

Fetal magnetoencephalography records fetal brain activity non-invasively. Delayed brain responses were reported for fetuses weighing below the tenth percentile. To investigate whether this delay indicates delayed brain maturation resulting from placental insufficiency, this study distinguished two groups of fetuses below the tenth percentile: growth-restricted fetuses with abnormal umbilical artery Doppler velocity (IUGR) and constitutionally small-for-gestational-age fetuses with normal umbilical artery Doppler findings (SGA) were compared with fetuses of adequate weight for gestational age (AGA), matched for age and behavioural state. A case-control study of matched pairs. Fetal magnetoencephalography-Center at the University Hospital of Tuebingen. Fourteen IUGR fetuses and 23 SGA fetuses were matched for gestational age and fetal behavioural state with 37 healthy, normal-sized fetuses. A 156-channel fetal magentoencephalography system was used to record fetal brain activity. Light flashes as visual stimulation were applied to the fetus. The Student's t-test for paired groups was performed. Latency of fetal visual evoked magnetic responses (VER). The IUGR fetuses showed delayed VERs compared with controls (IUGR, 233.1 ms; controls, 184.6 ms; P = 0.032). SGA fetuses had similar evoked response latencies compared with controls (SGA, 216.1 ms; controls, 219.9 ms; P = 0.828). Behavioural states were similarly distributed. Visual evoked responses are delayed in IUGR fetuses, but not in SGA. Fetal behavioural state as an influencing factor of brain response latency was accounted for in the comparison. This reinforces that delayed brain maturation is the result of placental insufficiency. © 2015 Royal College of Obstetricians and Gynaecologists.

Changes to online control and eye-hand coordination with healthy ageing.

PubMed

O'Rielly, Jessica L; Ma-Wyatt, Anna

2018-06-01

Goal directed movements are typically accompanied by a saccade to the target location. Online control plays an important part in correction of a reach, especially if the target or goal of the reach moves during the reach. While there are notable changes to visual processing and motor control with healthy ageing, there is limited evidence about how eye-hand coordination during online updating changes with healthy ageing. We sought to quantify differences between older and younger people for eye-hand coordination during online updating. Participants completed a double step reaching task implemented under time pressure. The target perturbation could occur 200, 400 and 600 ms into a reach. We measured eye position and hand position throughout the trials to investigate changes to saccade latency, movement latency, movement time, reach characteristics and eye-hand latency and accuracy. Both groups were able to update their reach in response to a target perturbation that occurred at 200 or 400 ms into the reach. All participants demonstrated incomplete online updating for the 600 ms perturbation time. Saccade latencies, measured from the first target presentation, were generally longer for older participants. Older participants had significantly increased movement times but there was no significant difference between groups for touch accuracy. We speculate that the longer movement times enable the use of new visual information about the target location for online updating towards the end of the movement. Interestingly, older participants also produced a greater proportion of secondary saccades within the target perturbation condition and had generally shorter eye-hand latencies. This is perhaps a compensatory mechanism as there was no significant group effect on final saccade accuracy. Overall, the pattern of results suggests that online control of movements may be qualitatively different in older participants. Crown Copyright © 2018. Published by Elsevier B.V. All rights reserved.

Directional asymmetries in human smooth pursuit eye movements.

PubMed

Ke, Sally R; Lam, Jessica; Pai, Dinesh K; Spering, Miriam

2013-06-27

Humans make smooth pursuit eye movements to bring the image of a moving object onto the fovea. Although pursuit accuracy is critical to prevent motion blur, the eye often falls behind the target. Previous studies suggest that pursuit accuracy differs between motion directions. Here, we systematically assess asymmetries in smooth pursuit. In experiment 1, binocular eye movements were recorded while observers (n = 20) tracked a small spot of light moving along one of four cardinal or diagonal axes across a featureless background. We analyzed pursuit latency, acceleration, peak velocity, gain, and catch-up saccade latency, number, and amplitude. In experiment 2 (n = 22), we examined the effects of spatial location and constrained stimulus motion within the upper or lower visual field. Pursuit was significantly faster (higher acceleration, peak velocity, and gain) and smoother (fewer and later catch-up saccades) in response to downward versus upward motion in both the upper and the lower visual fields. Pursuit was also more accurate and smoother in response to horizontal versus vertical motion. CONCLUSIONS. Our study is the first to report a consistent up-down asymmetry in human adults, regardless of visual field. Our findings suggest that pursuit asymmetries are adaptive responses to the requirements of the visual context: preferred motion directions (horizontal and downward) are more critical to our survival than nonpreferred ones.

Automated single-trial assessment of laser-evoked potentials as an objective functional diagnostic tool for the nociceptive system.

PubMed

Hatem, S M; Hu, L; Ragé, M; Gierasimowicz, A; Plaghki, L; Bouhassira, D; Attal, N; Iannetti, G D; Mouraux, A

2012-12-01

To assess the clinical usefulness of an automated analysis of event-related potentials (ERPs). Nociceptive laser-evoked potentials (LEPs) and non-nociceptive somatosensory electrically-evoked potentials (SEPs) were recorded in 37 patients with syringomyelia and 21 controls. LEP and SEP peak amplitudes and latencies were estimated using a single-trial automated approach based on time-frequency wavelet filtering and multiple linear regression, as well as a conventional approach based on visual inspection. The amplitudes and latencies of normal and abnormal LEP and SEP peaks were identified reliably using both approaches, with similar sensitivity and specificity. Because the automated approach provided an unbiased solution to account for average waveforms where no ERP could be identified visually, it revealed significant differences between patients and controls that were not revealed using the visual approach. The automated analysis of ERPs characterized reliably and objectively LEP and SEP waveforms in patients. The automated single-trial analysis can be used to characterize normal and abnormal ERPs with a similar sensitivity and specificity as visual inspection. While this does not justify its use in a routine clinical setting, the technique could be useful to avoid observer-dependent biases in clinical research. Copyright © 2012 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Real-Time Motion Tracking for Mobile Augmented/Virtual Reality Using Adaptive Visual-Inertial Fusion

PubMed Central

Fang, Wei; Zheng, Lianyu; Deng, Huanjun; Zhang, Hongbo

2017-01-01

In mobile augmented/virtual reality (AR/VR), real-time 6-Degree of Freedom (DoF) motion tracking is essential for the registration between virtual scenes and the real world. However, due to the limited computational capacity of mobile terminals today, the latency between consecutive arriving poses would damage the user experience in mobile AR/VR. Thus, a visual-inertial based real-time motion tracking for mobile AR/VR is proposed in this paper. By means of high frequency and passive outputs from the inertial sensor, the real-time performance of arriving poses for mobile AR/VR is achieved. In addition, to alleviate the jitter phenomenon during the visual-inertial fusion, an adaptive filter framework is established to cope with different motion situations automatically, enabling the real-time 6-DoF motion tracking by balancing the jitter and latency. Besides, the robustness of the traditional visual-only based motion tracking is enhanced, giving rise to a better mobile AR/VR performance when motion blur is encountered. Finally, experiments are carried out to demonstrate the proposed method, and the results show that this work is capable of providing a smooth and robust 6-DoF motion tracking for mobile AR/VR in real-time. PMID:28475145

Real-Time Motion Tracking for Mobile Augmented/Virtual Reality Using Adaptive Visual-Inertial Fusion.

PubMed

Fang, Wei; Zheng, Lianyu; Deng, Huanjun; Zhang, Hongbo

2017-05-05

In mobile augmented/virtual reality (AR/VR), real-time 6-Degree of Freedom (DoF) motion tracking is essential for the registration between virtual scenes and the real world. However, due to the limited computational capacity of mobile terminals today, the latency between consecutive arriving poses would damage the user experience in mobile AR/VR. Thus, a visual-inertial based real-time motion tracking for mobile AR/VR is proposed in this paper. By means of high frequency and passive outputs from the inertial sensor, the real-time performance of arriving poses for mobile AR/VR is achieved. In addition, to alleviate the jitter phenomenon during the visual-inertial fusion, an adaptive filter framework is established to cope with different motion situations automatically, enabling the real-time 6-DoF motion tracking by balancing the jitter and latency. Besides, the robustness of the traditional visual-only based motion tracking is enhanced, giving rise to a better mobile AR/VR performance when motion blur is encountered. Finally, experiments are carried out to demonstrate the proposed method, and the results show that this work is capable of providing a smooth and robust 6-DoF motion tracking for mobile AR/VR in real-time.

Brainstem auditory evoked responses in man. 1: Effect of stimulus rise-fall time and duration

NASA Technical Reports Server (NTRS)

Hecox, K.; Squires, N.; Galambos, R.

1975-01-01

Short latency (under 10 msec) evoked responses elicited by bursts of white noise were recorded from the scalp of human subjects. Response alterations produced by changes in the noise burst duration (on-time) inter-burst interval (off-time), and onset and offset shapes are reported and evaluated. The latency of the most prominent response component, wave V, was markedly delayed with increases in stimulus rise-time but was unaffected by changes in fall-time. The amplitude of wave V was insensitive to changes in signal rise-and-fall times, while increasing signal on-time produced smaller amplitude responses only for sufficiently short off-times. It is concluded that wave V of the human auditory brainstem evoked response is solely an onset response.

DOPAMINE DEPLETION SLOWS RETINAL TRANSMISSION

EPA Science Inventory

In male hooded rats, depletion of norepinephrine and dopamine by a-methyl-paratyrosine (AMT) significantly increased the latencies of early peaks in flash-evoked potentials recorded from the visual cortex, lateral geniculate nucleus, and optic tract. These effects were not produc...

Electrical stimulation reveals relatively ineffective sural nerve projections to dorsal horn neurons in the cat.

PubMed

Pubols, L M; Foglesong, M E; Vahle-Hinz, C

1986-04-16

Electrical stimulation of the sural nerve (SN) revealed input from sural nerve afferents to L6 and L7 dorsal horn neurons that were not apparent using natural mechanical stimuli, especially in cells with variable latency responses to SN stimulation. Nearly all (31/32) cells that had reliable, fixed latency responses to SN stimulation also had an excitatory receptive field (RF) in the region of skin innervated by the sural nerve (SN region). About one-third (20/57) of the cells with variable latency responses to SN stimulation, however, had an RF outside the SN region. Most (130/146) cells with no response to SN stimulation had RFs outside the SN region. There were no obvious differences between variable latency cells with RFs in the SN region vs those with RFs outside it in latency of response to SN stimulation, recording depth, RF sizes or modality properties. In a subsample of 31 postsynaptic dorsal column neurons all cells responding to SN stimulation also had an RF in the SN region. Strengthening of relatively ineffective projections from the sural nerve by lesions might be expected to lead to an increase in the proportion of cells responding with impulses to natural stimulation of the skin innervated by the sural nerve, and, hence, to an increase in average RF size.

Comparison of Text-Based and Visual-Based Programming Input Methods for First-Time Learners

ERIC Educational Resources Information Center

Saito, Daisuke; Washizaki, Hironori; Fukazawa, Yoshiaki

2017-01-01

Aim/Purpose: When learning to program, both text-based and visual-based input methods are common. However, it is unclear which method is more appropriate for first-time learners (first learners). Background: The differences in the learning effect between text-based and visual-based input methods for first learners are compared the using a…

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

Moreland, Kenneth; Sewell, Christopher; Usher, William

Here, one of the most critical challenges for high-performance computing (HPC) scientific visualization is execution on massively threaded processors. Of the many fundamental changes we are seeing in HPC systems, one of the most profound is a reliance on new processor types optimized for execution bandwidth over latency hiding. Our current production scientific visualization software is not designed for these new types of architectures. To address this issue, the VTK-m framework serves as a container for algorithms, provides flexible data representation, and simplifies the design of visualization algorithms on new and future computer architecture.

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

Moreland, Kenneth; Sewell, Christopher; Usher, William

Execution on massively threaded processors is one of the most critical challenges for high-performance computing (HPC) scientific visualization. Of the many fundamental changes we are seeing in HPC systems, one of the most profound is a reliance on new processor types optimized for execution bandwidth over latency hiding. Moreover, our current production scientific visualization software is not designed for these new types of architectures. In order to address this issue, the VTK-m framework serves as a container for algorithms, provides flexible data representation, and simplifies the design of visualization algorithms on new and future computer architecture.

Influence of visual control, conduction, and central integration on static and dynamic balance in healthy older adults.

PubMed

Perrin, P P; Jeandel, C; Perrin, C A; Béné, M C

1997-01-01

Aging is associated with decreased balance abilities, resulting in an increased risk of fall. In order to appreciate the visual, somatosensory, and central signals involved in balance control, sophisticated methods of posturography assessment have been developed, using static and dynamic tests, eventually associated with electromyographic measurements. We applied such methods to a population of healthy older adults in order to appreciate the respective importance of each of these sensorial inputs in aging individuals. Posture control parameters were recorded on a force-measuring platform in 41 healthy young (age 28.5 +/- 5.9 years) and 50 older (age 69.8 +/- 5.9 years) adults, using a static test and two dynamic tests performed by all individuals first with eyes open, then with eyes closed. The distance covered by the center of foot pressure, sway area, and anteroposterior oscillations were significantly higher, with eyes open or closed, in older people than in young subjects. Significant differences were noted in dynamic tests with longer latency responses in the group of old people. Dynamic recordings in a sinusoidal test had a more regular pattern when performed eyes open in both groups and evidenced significantly greater instability in old people. These data suggest that vision remains important in maintaining postural control while conduction and central integration become less efficient with age.

Visual search in a forced-choice paradigm

NASA Technical Reports Server (NTRS)

Holmgren, J. E.

1974-01-01

The processing of visual information was investigated in the context of two visual search tasks. The first was a forced-choice task in which one of two alternative letters appeared in a visual display of from one to five letters. The second task included trials on which neither of the two alternatives was present in the display. Search rates were estimated from the slopes of best linear fits to response latencies plotted as a function of the number of items in the visual display. These rates were found to be much slower than those estimated in yes-no search tasks. This result was interpreted as indicating that the processes underlying visual search in yes-no and forced-choice tasks are not the same.

Familiarity Speeds Up Visual Short-term Memory Consolidation: Electrophysiological Evidence from Contralateral Delay Activities.

PubMed

Xie, Weizhen; Zhang, Weiwei

2018-01-01

To test how preexisting long-term memory influences visual STM, this study takes advantage of individual differences in participants' prior familiarity with Pokémon characters and uses an ERP component, the contralateral delay activity (CDA), to assess whether observers' prior stimulus familiarity affects STM consolidation and storage capacity. In two change detection experiments, consolidation speed, as indexed by CDA fractional area latency and/or early-window (500-800 msec) amplitude, was significantly associated with individual differences in Pokémon familiarity. In contrast, the number of remembered Pokémon stimuli, as indexed by Cowan's K and late-window (1500-2000 msec) CDA amplitude, was significantly associated with individual differences in Pokémon familiarity when STM consolidation was incomplete because of a short presentation of Pokémon stimuli (500 msec, Experiment 2), but not when STM consolidation was allowed to complete given sufficient encoding time (1000 msec, Experiment 1). Similar findings were obtained in between-group analyses when participants were separated into high-familiarity and low-familiarity groups based on their Pokémon familiarity ratings. Together, these results suggest that stimulus familiarity, as a proxy for the strength of preexisting long-term memory, primarily speeds up STM consolidation, which may subsequently lead to an increase in the number of remembered stimuli if consolidation is incomplete. These findings thus highlight the importance of research assessing how effects on representations (e.g., STM capacity) are in general related to (or even caused by) effects on processes (e.g., STM consolidation) in cognition.

Does modafinil enhance cognitive performance in young volunteers who are not sleep-deprived?

PubMed

Randall, Delia C; Viswanath, Aparna; Bharania, Punam; Elsabagh, Sarah M; Hartley, David E; Shneerson, John M; File, Sandra E

2005-04-01

In a double-blind, parallel groups study, 60 healthy student volunteers (29 men and 31 women, aged 19-22 years) were randomly allocated to receive placebo, 100 or 200 mg modafinil. Two hours later, in the early evening, they completed an extensive cognitive battery. The 3 groups did not differ in self-ratings of sleepiness or tiredness before the testing session, and there were no treatment-associated changes in these or in mood ratings during the tests. Modafinil was without effect in several tests of reaction time and attention, but the 200-mg group was faster at simple color naming of dots and performed better than placebo in the Rapid Visual Information Processing test of sustained attention. Modafinil was without effect on spatial working memory, but the 100-mg group performed better in the backward part of the digit span test. Modafinil was without effect on verbal short-term memory (story recall), but 100 mg improved digit span forward, and both doses improved pattern recognition, although this was accompanied by a slowing of response latency in the 200-mg group. There were no significant effects of modafinil compared with placebo in tests of long-term memory, executive function, visuospatial and constructional ability, or category fluency. These results suggest that the benefits of modafinil are not clearly dose-related, and those from 100 mg are limited to the span of immediate verbal recall and short-term visual recognition memory, which is insufficient for it to be considered as a cognitive enhancer in non-sleep-deprived individuals.

Neurotoxic effects of n-hexane on the human central nervous system: evoked potential abnormalities in n-hexane polyneuropathy.

PubMed Central

Chang, Y C

1987-01-01

An outbreak of n-hexane polyneuropathy as a result of industrial exposure occurred in printing factories in Taipei area from December 1983 to February 1985. Multimodality evoked potentials study was performed on 22 of the polyneuropathy cases, five of the subclinical cases, and seven of the unaffected workers. The absolute and interpeak latencies of patterned visual evoked potential (pVEP) in both the polyneuropathy and subclinical groups were longer than in the normal controls. The pVEP interpeak amplitude was also decreased in the polyneuropathy cases. Brainstem auditory evoked potentials (BAEP), showed no difference of wave I latency between factory workers and normal controls, but prolongation of the wave I-V interpeak latencies was noted, corresponding with the severity of the polyneuropathy. In somatosensory evoked potentials (SEPs), both the absolute latencies and central conduction time (CCT) were longer in subclinical and polyneuropathy cases than in the unaffected workers and normal controls. From this evoked potentials study, chronic toxic effects of n-hexane on the central nervous system were shown. PMID:3031221

Saccade latency reveals episodic representation of object color.

PubMed

Gordon, Robert D

2014-08-01

While previous studies suggest that identity, but not color, plays a role in episodic object representation, such studies have typically used tasks in which only identity is relevant, raising the possibility that the results reflect task demands, rather than the general principles that underlie object representation. In the present study, participants viewed a preview display containing one (Experiments 1 and 2) or two (Experiment 3) letters, then viewed a target display containing a single letter, in either the same or a different location. Participants executed an immediate saccade to fixate the target; saccade latency served as the dependent variable. In all experiments, saccade latencies were longer to fixate a target appearing in its previewed location, consistent with a bias to attend to new objects rather than to objects for which episodic representations are being maintained in visual working memory. The results of Experiment 3 further demonstrate, however, that changing target color eliminates these latency differences. The results suggest that color and identity are part of episodic representation even when not task relevant and that examining biases in saccade execution may be a useful approach to studying episodic representation.

Visual neglect following stroke: current concepts and future focus.

PubMed

Ting, Darren S J; Pollock, Alex; Dutton, Gordon N; Doubal, Fergus N; Ting, Daniel S W; Thompson, Michelle; Dhillon, Baljean

2011-01-01

Visual neglect is a common, yet frequently overlooked, neurological disorder following stroke characterized by a deficit in attention and appreciation of stimuli on the contralesional side of the body. It has a profound functional impact on affected individuals. A assessment and management of this condition are hindered, however, by the lack of professional awareness and clinical guidelines. Recent evidence suggests that the underlying deficit in visual attention is due to a disrupted internalized representation of the outer world rather than a disorder of sensory inputs. Dysfunction of the cortical domains and white-matter tracts, as well as inter-hemispheric imbalance, have been implicated in the various manifestations of visual neglect. Optimal diagnosis requires careful history-taking from the patient, family, and friends, in addition to clinical assessment with the line bisection test, the star cancellation test, and the Catherine Bergego Scale. Early recognition and prompt rehabilitation employing a multidisciplinary approach is desirable. Although no treatment has been definitively shown to be of benefit, those with promise include prism adaptation, visual scanning therapy, and virtual reality-based techniques. Further high quality research to seek optimum short- and long-term rehabilitative strategies for visual neglect is required. Copyright © 2011 Elsevier Inc. All rights reserved.

Sleep patterns and insomnia among adolescents: a population-based study.

PubMed

Hysing, Mari; Pallesen, Ståle; Stormark, Kjell M; Lundervold, Astri J; Sivertsen, Børge

2013-10-01

The aim of the current study was to examine sleep patterns and rates of insomnia in a population-based study of adolescents aged 16-19 years. Gender differences in sleep patterns and insomnia, as well as a comparison of insomnia rates according to DSM-IV, DSM-V and quantitative criteria for insomnia (Behav. Res. Ther., 41, 2003, 427), were explored. We used a large population-based study in Hordaland county in Norway, conducted in 2012. The sample included 10,220 adolescents aged 16-18 years (54% girls). Self-reported sleep measurements included bedtime, rise time, time in bed, sleep duration, sleep efficiency, sleep onset latency, wake after sleep onset, rate and frequency and duration of difficulties initiating and maintaining sleep and rate and frequency of tiredness and sleepiness. The adolescents reported short sleep duration on weekdays (mean 6:25 hours), resulting in a sleep deficiency of about 2 h. A majority of the adolescents (65%) reported sleep onset latency exceeding 30 min. Girls reported longer sleep onset latency and a higher rate of insomnia than boys, while boys reported later bedtimes and a larger weekday-weekend discrepancy on several sleep parameters. Insomnia prevalence rates ranged from a total prevalence of 23.8 (DSM-IV criteria), 18.5 (DSM-V criteria) and 13.6% (quantitative criteria for insomnia). We conclude that short sleep duration, long sleep onset latency and insomnia were prevalent in adolescents. This warrants attention as a public health concern in this age group. © 2013 European Sleep Research Society.

Vestibular short latency responses to pulsed linear acceleration in unanesthetized animals

NASA Technical Reports Server (NTRS)

Jones, T. A.

1992-01-01

Linear acceleration transients were used to elicit vestibular compound action potentials in non-invasively prepared, unanesthetized animals for the first time (chicks, Gallus domesticus, n = 33). Responses were composed of a series of up to 8 dominant peaks occurring within 8 msec of the stimulus. Response amplitudes for 1.0 g stimulus ranged from 1 to 10 microV. A late, slow, triphasic, anesthesia-labile component was identified as a dominant response feature in unanesthetized animals. Amplitudes increased and latencies decreased as stimulus intensity was increased (MANOVA P less than 0.05). Linear regression slope ranges were: amplitudes = 1.0-5.0 microV/g; latencies = -300 to -1100 microseconds/g. Thresholds for single polarity stimuli (0.035 +/- 0.022 g, n = 11) were significantly lower than those of alternating polarity (0.074 +/- 0.028 g, n = 18, P less than 0.001). Bilateral labyrinthectomy eliminated responses whereas bilateral extirpation of cochleae did not significantly change response thresholds. Intense acoustic masking (100/104 dB SL) produced no effect in 2 animals, but did produce small to moderate effects on response amplitudes in 7 others. Changes were attributed to effects on vestibular end organs. Results of unilateral labyrinth blockade (tetrodotoxin) suggest that P1 and N1 preferentially reflect ipsilateral eighth nerve compound action potentials whereas components beyond approximately 2 msec reflect activity from vestibular neurons that depend on both labyrinths. The results demonstrate that short latency vestibular compound action potentials can be measured in unanesthetized, non-invasively prepared animals.

Effects of diphenhydramine on human eye movements.

PubMed

Hopfenbeck, J R; Cowley, D S; Radant, A; Greenblatt, D J; Roy-Byrne, P P

1995-04-01

Peak saccadic eye movement velocity (SEV) and average smooth pursuit gain (SP) are reduced in a dose-dependent manner by diazepam and provide reliable, quantitative measures of benzodiazepine agonist effects. To evaluate the specificity of these eye movement effects for agents acting at the central GABA-benzodiazepine receptor complex and the role of sedation in benzodiazepine effects, we studied eye movement effects of diphenhydramine, a sedating drug which does not act at the GABA-benzodiazepine receptor complex. Ten healthy males, aged 19-28 years, with no history of axis I psychiatric disorders or substance abuse, received 50 mg/70 kg intravenous diphenhydramine or a similar volume of saline on separate days 1 week apart. SEV, saccade latency and accuracy, SP, self-rated sedation, and short-term memory were assessed at baseline and at 5, 15, 30, 45, 60, 90 and 120 min after drug administration. Compared with placebo, diphenhydramine produced significant SEV slowing, and increases in saccade latency and self-rated sedation. There was no significant effect of diphenhydramine on smooth pursuit gain, saccade accuracy, or short-term memory. These results suggest that, like diazepam, diphenhydramine causes sedation, SEV slowing, and an increase in saccade latency. Since the degree of diphenhydramine-induced sedation was not correlated with changes in SEV or saccade latency, slowing of saccadic eye movements is unlikely to be attributable to sedation alone. Unlike diazepam, diphenhydramine does not impair smooth pursuit gain, saccadic accuracy, or memory. Different neurotransmitter systems may influence the neural pathways involved in SEV and smooth pursuit again.

Dynamics of the spatial scale of visual attention revealed by brain event-related potentials

NASA Technical Reports Server (NTRS)

Luo, Y. J.; Greenwood, P. M.; Parasuraman, R.

2001-01-01

The temporal dynamics of the spatial scaling of attention during visual search were examined by recording event-related potentials (ERPs). A total of 16 young participants performed a search task in which the search array was preceded by valid cues that varied in size and hence in precision of target localization. The effects of cue size on short-latency (P1 and N1) ERP components, and the time course of these effects with variation in cue-target stimulus onset asynchrony (SOA), were examined. Reaction time (RT) to discriminate a target was prolonged as cue size increased. The amplitudes of the posterior P1 and N1 components of the ERP evoked by the search array were affected in opposite ways by the size of the precue: P1 amplitude increased whereas N1 amplitude decreased as cue size increased, particularly following the shortest SOA. The results show that when top-down information about the region to be searched is less precise (larger cues), RT is slowed and the neural generators of P1 become more active, reflecting the additional computations required in changing the spatial scale of attention to the appropriate element size to facilitate target discrimination. In contrast, the decrease in N1 amplitude with cue size may reflect a broadening of the spatial gradient of attention. The results provide electrophysiological evidence that changes in the spatial scale of attention modulate neural activity in early visual cortical areas and activate at least two temporally overlapping component processes during visual search.

Spatial working memory for locations specified by vision and audition: testing the amodality hypothesis.

PubMed

Loomis, Jack M; Klatzky, Roberta L; McHugh, Brendan; Giudice, Nicholas A

2012-08-01

Spatial working memory can maintain representations from vision, hearing, and touch, representations referred to here as spatial images. The present experiment addressed whether spatial images from vision and hearing that are simultaneously present within working memory retain modality-specific tags or are amodal. Observers were presented with short sequences of targets varying in angular direction, with the targets in a given sequence being all auditory, all visual, or a sequential mixture of the two. On two thirds of the trials, one of the locations was repeated, and observers had to respond as quickly as possible when detecting this repetition. Ancillary detection and localization tasks confirmed that the visual and auditory targets were perceptually comparable. Response latencies in the working memory task showed small but reliable costs in performance on trials involving a sequential mixture of auditory and visual targets, as compared with trials of pure vision or pure audition. These deficits were statistically reliable only for trials on which the modalities of the matching location switched from the penultimate to the final target in the sequence, indicating a switching cost. The switching cost for the pair in immediate succession means that the spatial images representing the target locations retain features of the visual or auditory representations from which they were derived. However, there was no reliable evidence of a performance cost for mixed modalities in the matching pair when the second of the two did not immediately follow the first, suggesting that more enduring spatial images in working memory may be amodal.

Spatiotemporal Filter for Visual Motion Integration from Pursuit Eye Movements in Humans and Monkeys

PubMed Central

Liu, Bing

2017-01-01

Despite the enduring interest in motion integration, a direct measure of the space–time filter that the brain imposes on a visual scene has been elusive. This is perhaps because of the challenge of estimating a 3D function from perceptual reports in psychophysical tasks. We take a different approach. We exploit the close connection between visual motion estimates and smooth pursuit eye movements to measure stimulus–response correlations across space and time, computing the linear space–time filter for global motion direction in humans and monkeys. Although derived from eye movements, we find that the filter predicts perceptual motion estimates quite well. To distinguish visual from motor contributions to the temporal duration of the pursuit motion filter, we recorded single-unit responses in the monkey middle temporal cortical area (MT). We find that pursuit response delays are consistent with the distribution of cortical neuron latencies and that temporal motion integration for pursuit is consistent with a short integration MT subpopulation. Remarkably, the visual system appears to preferentially weight motion signals across a narrow range of foveal eccentricities rather than uniformly over the whole visual field, with a transiently enhanced contribution from locations along the direction of motion. We find that the visual system is most sensitive to motion falling at approximately one-third the radius of the stimulus aperture. Hypothesizing that the visual drive for pursuit is related to the filtered motion energy in a motion stimulus, we compare measured and predicted eye acceleration across several other target forms. SIGNIFICANCE STATEMENT A compact model of the spatial and temporal processing underlying global motion perception has been elusive. We used visually driven smooth eye movements to find the 3D space–time function that best predicts both eye movements and perception of translating dot patterns. We found that the visual system does not appear to use all available motion signals uniformly, but rather weights motion preferentially in a narrow band at approximately one-third the radius of the stimulus. Although not universal, the filter predicts responses to other types of stimuli, demonstrating a remarkable degree of generalization that may lead to a deeper understanding of visual motion processing. PMID:28003348

Sensory experience modifies feature map relationships in visual cortex

PubMed Central

Cloherty, Shaun L; Hughes, Nicholas J; Hietanen, Markus A; Bhagavatula, Partha S

2016-01-01

The extent to which brain structure is influenced by sensory input during development is a critical but controversial question. A paradigmatic system for studying this is the mammalian visual cortex. Maps of orientation preference (OP) and ocular dominance (OD) in the primary visual cortex of ferrets, cats and monkeys can be individually changed by altered visual input. However, the spatial relationship between OP and OD maps has appeared immutable. Using a computational model we predicted that biasing the visual input to orthogonal orientation in the two eyes should cause a shift of OP pinwheels towards the border of OD columns. We then confirmed this prediction by rearing cats wearing orthogonally oriented cylindrical lenses over each eye. Thus, the spatial relationship between OP and OD maps can be modified by visual experience, revealing a previously unknown degree of brain plasticity in response to sensory input. DOI: http://dx.doi.org/10.7554/eLife.13911.001 PMID:27310531

Coordinate Transformations in Object Recognition

ERIC Educational Resources Information Center

Graf, Markus

2006-01-01

A basic problem of visual perception is how human beings recognize objects after spatial transformations. Three central classes of findings have to be accounted for: (a) Recognition performance varies systematically with orientation, size, and position; (b) recognition latencies are sequentially additive, suggesting analogue transformation…

Striate cortical contribution to the transcorneal electrically evoked response of the visual system.

PubMed

Shimazu, K; Miyake, Y; Fukatsu, Y; Watanabe, S

1996-01-01

Analyses of current-source-density (CSD) and multiple unit activity (MUA) in area 17 of the cat were performed to determine the sources of the cortical transcorneal electrically evoked response. Cortical field potential, CSD and MUA profiles were obtained with multi-electrodes. CSD findings include: current sinks (inward cell membrane current) within 20 ms latency, in layers 4 and 6 of the striate cortex; current sinks corresponding to N3 (negative component of the EER; latency, 35 ms) in layer 4 and lower layer 3 with current sources (outward cell membrane current) for N3 in the supragranular layers; current sinks with latency over 40 ms in the supragranular layers. In the layers 4 and 6, simultaneous MUA was seen. When the stimulus frequency was increased or with dual stimulation, the N3 current sinks were decreased. This indicates that N1 (latency, 9 ms) and N2 (latency, 20 ms) reflect near-field potentials in layers 4 and 6, generated by geniculocortical afferents, and that N3 is a post- and polysynaptic component. It is also suggested that dipoles composed of cell bodies and the apical dendrites of pyramidal cells of layer 3, generated by satellite cells in layer 4, play a major role in generating N3.

Visual Occlusion Decreases Motion Sickness in a Flight Simulator.

PubMed

Ishak, Shaziela; Bubka, Andrea; Bonato, Frederick

2018-05-01

Sensory conflict theories of motion sickness (MS) assert that symptoms may result when incoming sensory inputs (e.g., visual and vestibular) contradict each other. Logic suggests that attenuating input from one sense may reduce conflict and hence lessen MS symptoms. In the current study, it was hypothesized that attenuating visual input by blocking light entering the eye would reduce MS symptoms in a motion provocative environment. Participants sat inside an aircraft cockpit mounted onto a motion platform that simultaneously pitched, rolled, and heaved in two conditions. In the occluded condition, participants wore "blackout" goggles and closed their eyes to block light. In the control condition, participants opened their eyes and had full view of the cockpit's interior. Participants completed separate Simulator Sickness Questionnaires before and after each condition. The posttreatment total Simulator Sickness Questionnaires and subscores for nausea, oculomotor, and disorientation in the control condition were significantly higher than those in the occluded condition. These results suggest that under some conditions attenuating visual input may delay the onset of MS or weaken the severity of symptoms. Eliminating visual input may reduce visual/nonvisual sensory conflict by weakening the influence of the visual channel, which is consistent with the sensory conflict theory of MS.

The effects of click and tone-burst stimulus parameters on the vestibular evoked myogenic potential (VEMP).

PubMed

Akin, Faith Wurm; Murnane, Owen D; Proffitt, Tina M

2003-11-01

Vestibular evoked myogenic potentials (VEMP) are short latency electromyograms (EMG) evoked by high-level acoustic stimuli and recorded from surface electrodes over the tonically contracted sternocleidomastoid (SCM) muscle and are presumed to originate in the saccule. The present experiments examined the effects of click and tone-burst level and stimulus frequency on the latency, amplitude, and threshold of the VEMP in subjects with normal hearing sensitivity and no history of vestibular disease. VEMPs were recorded in all subjects using 100 dB nHL click stimuli. Most subjects had VEMPs present at 500, 750, and 1000 Hz, and few subjects had VEMPs present at 2000 Hz. The response amplitude of the VEMP increased with click and tone-burst level, whereas VEMP latency was not influenced by the stimulus level. The largest tone-burst-evoked VEMPs and lowest thresholds were obtained at 500 and 750 Hz. VEMP latency was independent of stimulus frequency when tone-burst duration was held constant.

Stream-related preferences of inputs to the superior colliculus from areas of dorsal and ventral streams of mouse visual cortex.

PubMed

Wang, Quanxin; Burkhalter, Andreas

2013-01-23

Previous studies of intracortical connections in mouse visual cortex have revealed two subnetworks that resemble the dorsal and ventral streams in primates. Although calcium imaging studies have shown that many areas of the ventral stream have high spatial acuity whereas areas of the dorsal stream are highly sensitive for transient visual stimuli, there are some functional inconsistencies that challenge a simple grouping into "what/perception" and "where/action" streams known in primates. The superior colliculus (SC) is a major center for processing of multimodal sensory information and the motor control of orienting the eyes, head, and body. Visual processing is performed in superficial layers, whereas premotor activity is generated in deep layers of the SC. Because the SC is known to receive input from visual cortex, we asked whether the projections from 10 visual areas of the dorsal and ventral streams terminate in differential depth profiles within the SC. We found that inputs from primary visual cortex are by far the strongest. Projections from the ventral stream were substantially weaker, whereas the sparsest input originated from areas of the dorsal stream. Importantly, we found that ventral stream inputs terminated in superficial layers, whereas dorsal stream inputs tended to be patchy and either projected equally to superficial and deep layers or strongly preferred deep layers. The results suggest that the anatomically defined ventral and dorsal streams contain areas that belong to distinct functional systems, specialized for the processing of visual information and visually guided action, respectively.

Diagnosis of Normal and Abnormal Color Vision with Cone-Specific VEPs.

PubMed

Rabin, Jeff C; Kryder, Andrew C; Lam, Dan

2016-05-01

Normal color vision depends on normal long wavelength (L), middle wavelength (M), and short wavelength sensitive (S) cones. Hereditary "red-green" color vision deficiency (CVD) is due to a shift in peak sensitivity or lack of L or M cones. Hereditary S cone CVD is rare but can be acquired as an early sign of disease. Current tests detect CVD but few diagnose type or severity, critical for linking performance to real-world demands. The anomaloscope and newer subjective tests quantify CVD but are not applicable to infants or cognitively impaired patients. Our purpose was to develop an objective test of CVD with sensitivity and specificity comparable to current tests. A calibrated visual-evoked potential (VEP) display and Food and Drug Administration-approved system was used to record L, M, and S cone-specific pattern-onset VEPs from 18 color vision normals (CVNs) and 13 hereditary CVDs. VEP amplitudes and latencies were compared between groups to establish VEP sensitivity and specificity. Cone VEPs show 100% sensitivity for diagnosis of CVD and 94% specificity for confirming CVN. L cone (protan) CVDs showed a significant increase in L cone latency (53.1 msec, P < 0.003) and decreased amplitude (10.8 uV, P < 0.0000005) but normal M and S cone VEPs ( P > 0.31). M cone (deutan) CVDs showed a significant increase in M cone latency (31.0 msec, P < 0.000004) and decreased amplitude (8.4 uV, P < 0.006) but normal L and S cone VEPs ( P > 0.29). Cone-specific VEPs offer a rapid, objective test to diagnose hereditary CVD and show potential for detecting acquired CVD in various diseases. This paper describes the efficacy of cone-specific color VEPs for quantification of normal and abnormal color vision. The rapid, objective nature of this approach makes it suitable for detecting color sensitivity loss in infants and the cognitively impaired.

Electronic Sleep Stage Classifiers: A Survey and VLSI Design Methodology.

PubMed

Kassiri, Hossein; Chemparathy, Aditi; Salam, M Tariqus; Boyce, Richard; Adamantidis, Antoine; Genov, Roman

2017-02-01

First, existing sleep stage classifier sensors and algorithms are reviewed and compared in terms of classification accuracy, level of automation, implementation complexity, invasiveness, and targeted application. Next, the implementation of a miniature microsystem for low-latency automatic sleep stage classification in rodents is presented. The classification algorithm uses one EMG (electromyogram) and two EEG (electroencephalogram) signals as inputs in order to detect REM (rapid eye movement) sleep, and is optimized for low complexity and low power consumption. It is implemented in an on-board low-power FPGA connected to a multi-channel neural recording IC, to achieve low-latency (order of 1 ms or less) classification. Off-line experimental results using pre-recorded signals from nine mice show REM detection sensitivity and specificity of 81.69% and 93.86%, respectively, with the maximum latency of 39 [Formula: see text]. The device is designed to be used in a non-disruptive closed-loop REM sleep suppression microsystem, for future studies of the effects of REM sleep deprivation on memory consolidation.

Conditioned allophony in speech perception: an ERP study.

PubMed

Miglietta, Sandra; Grimaldi, Mirko; Calabrese, Andrea

2013-09-01

A Mismatch Negativity (MMN) study was performed to investigate whether pre-attentive vowel perception is influenced by phonological status. We compared the MMN response to the acoustic distinction between the allophonic variation [ε-e] and phonemic contrast [e-i] present in a Southern-Italian variety (Tricase dialect). Clear MMNs were elicited for both the phonemic and allophonic conditions. Interestingly, a shorter latency was observed for the phonemic pair, but no significant amplitude difference was observed between the two conditions. Together, these results suggest that for isolated vowels, the phonological status of a vowel category is reflected in the latency of the MMN peak. The earlier latency of the phonemic condition argues for an easier parsing and encoding of phonemic contrasts in memory representations. Thus, neural computations mapping auditory inputs into higher perceptual representations seem 'sensitive' to the contrastive/non-contrastive status of the sounds as determined by the listeners' knowledge of the own phonological system. Copyright © 2013 Elsevier Inc. All rights reserved.

Differences between Dyslexic and Non-Dyslexic Children in the Performance of Phonological Visual-Auditory Recognition Tasks: An Eye-Tracking Study

PubMed Central

Tiadi, Aimé; Seassau, Magali; Gerard, Christophe-Loïc; Bucci, Maria Pia

2016-01-01

The object of this study was to explore further phonological visual-auditory recognition tasks in a group of fifty-six healthy children (mean age: 9.9 ± 0.3) and to compare these data to those recorded in twenty-six age-matched dyslexic children (mean age: 9.8 ± 0.2). Eye movements from both eyes were recorded using an infrared video-oculography system (MobileEBT® e(y)e BRAIN). The recognition task was performed under four conditions in which the target object was displayed either with phonologically unrelated objects (baseline condition), or with cohort or rhyme objects (cohort and rhyme conditions, respectively), or both together (rhyme + cohort condition). The percentage of the total time spent on the targets and the latency of the first saccade on the target were measured. Results in healthy children showed that the percentage of the total time spent in the baseline condition was significantly longer than in the other conditions, and that the latency of the first saccade in the cohort condition was significantly longer than in the other conditions; interestingly, the latency decreased significantly with the increasing age of the children. The developmental trend of phonological awareness was also observed in healthy children only. In contrast, we observed that for dyslexic children the total time spent on the target was similar in all four conditions tested, and also that they had similar latency values in both cohort and rhyme conditions. These findings suggest a different sensitivity to the phonological competitors between dyslexic and non-dyslexic children. Also, the eye-tracking technique provides online information about phonological awareness capabilities in children. PMID:27438352

Continuous recognition of spatial and nonspatial stimuli in hippocampal-lesioned rats.

PubMed

Jackson-Smith, P; Kesner, R P; Chiba, A A

1993-03-01

The present experiments compared the performance of hippocampal-lesioned rats to control rats on a spatial continuous recognition task and an analogous nonspatial task with similar processing demands. Daily sessions for Experiment 1 involved sequential presentation of individual arms on a 12-arm radial maze. Each arm contained a Froot Loop reinforcement the first time it was presented, and latency to traverse the arm was measured. A subset of the arms were repeated, but did not contain reinforcement. Repeated arms were presented with lags ranging from 0 to 6 (0 to 6 different arm presentations occurred between the first and the repeated presentation). Difference scores were computed by subtracting the latency on first presentations from the latency on repeated presentations, and these scores were high in all rats prior to surgery, with a decreasing function across lag. There were no differences in performance following cortical control or sham surgery. However, there was a total deficit in performance following large electrolytic lesions of the hippocampus. The second experiment employed the same continuous recognition memory procedure, but used three-dimensional visual objects (toys, junk items, etc., in various shapes, sizes, and textures) as stimuli on a flat runway. As in Experiment 1, the stimuli were presented successively and latency to run to and move the object was measured. Objects were repeated with lags ranging from 0 to 4. Performance on this task following surgery did not differ from performance prior to surgery for either the control group or the hippocampal lesion group. These results provide support for Kesner's attribute model of hippocampal function in that the hippocampus is assumed to mediate data-based memory for spatial locations, but not three-dimensional visual objects.

Sound effects: Multimodal input helps infants find displaced objects.

PubMed

Shinskey, Jeanne L

2017-09-01

Before 9 months, infants use sound to retrieve a stationary object hidden by darkness but not one hidden by occlusion, suggesting auditory input is more salient in the absence of visual input. This article addresses how audiovisual input affects 10-month-olds' search for displaced objects. In AB tasks, infants who previously retrieved an object at A subsequently fail to find it after it is displaced to B, especially following a delay between hiding and retrieval. Experiment 1 manipulated auditory input by keeping the hidden object audible versus silent, and visual input by presenting the delay in the light versus dark. Infants succeeded more at B with audible than silent objects and, unexpectedly, more after delays in the light than dark. Experiment 2 presented both the delay and search phases in darkness. The unexpected light-dark difference disappeared. Across experiments, the presence of auditory input helped infants find displaced objects, whereas the absence of visual input did not. Sound might help by strengthening object representation, reducing memory load, or focusing attention. This work provides new evidence on when bimodal input aids object processing, corroborates claims that audiovisual processing improves over the first year of life, and contributes to multisensory approaches to studying cognition. Statement of contribution What is already known on this subject Before 9 months, infants use sound to retrieve a stationary object hidden by darkness but not one hidden by occlusion. This suggests they find auditory input more salient in the absence of visual input in simple search tasks. After 9 months, infants' object processing appears more sensitive to multimodal (e.g., audiovisual) input. What does this study add? This study tested how audiovisual input affects 10-month-olds' search for an object displaced in an AB task. Sound helped infants find displaced objects in both the presence and absence of visual input. Object processing becomes more sensitive to bimodal input as multisensory functions develop across the first year. © 2016 The British Psychological Society.

Latencies in BOLD response during visual attention processes.

PubMed

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

2011-04-22

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

Rebalancing Spatial Attention: Endogenous Orienting May Partially Overcome the Left Visual Field Bias in Rapid Serial Visual Presentation.

PubMed

Śmigasiewicz, Kamila; Hasan, Gabriel Sami; Verleger, Rolf

2017-01-01

In dynamically changing environments, spatial attention is not equally distributed across the visual field. For instance, when two streams of stimuli are presented left and right, the second target (T2) is better identified in the left visual field (LVF) than in the right visual field (RVF). Recently, it has been shown that this bias is related to weaker stimulus-driven orienting of attention toward the RVF: The RVF disadvantage was reduced with salient task-irrelevant valid cues and increased with invalid cues. Here we studied if also endogenous orienting of attention may compensate for this unequal distribution of stimulus-driven attention. Explicit information was provided about the location of T1 and T2. Effectiveness of the cue manipulation was confirmed by EEG measures: decreasing alpha power before stream onset with informative cues, earlier latencies of potentials evoked by T1-preceding distractors at the right than at the left hemisphere when T1 was cued left, and decreasing T1- and T2-evoked N2pc amplitudes with informative cues. Importantly, informative cues reduced (though did not completely abolish) the LVF advantage, indicated by improved identification of right T2, and reflected by earlier N2pc latency evoked by right T2 and larger decrease in alpha power after cues indicating right T2. Overall, these results suggest that endogenously driven attention facilitates stimulus-driven orienting of attention toward the RVF, thereby partially overcoming the basic LVF bias in spatial attention.

Visual Hallucinations and Pontine Demyelination in a Child: Possible REM Dissociation?

PubMed Central

Vita, Maria Gabriella; Batocchi, Anna Paola; Dittoni, Serena; Losurdo, Anna; Cianfoni, Alessandro; Stefanini, Maria Chiara; Vollono, Catello; Marca, Giacomo Della; Mariotti, Paolo

2008-01-01

An 11 year-old-boy acutely developed complex visual and acoustic hallucinations. Hallucinations, consisting of visions of a threatening, evil character of the Harry Potter saga, persisted for 3 days. Neurological and psychiatric examinations were normal. Ictal EEG was negative. MRI documented 3 small areas of hyperintense signal in the brainstem, along the paramedian and lateral portions of pontine tegmentum, one of which showed post-contrast enhancement. These lesions were likely of inflammatory origin, and treatment with immunoglobulins was started. Polysomnography was normal, multiple sleep latency test showed a mean sleep latency of 8 minutes, with one sleep-onset REM period. The pontine tegmentum is responsible for REM sleep regulation, and contains definite “REM-on” and “REM-off” regions. The anatomical distribution of the lesions permits us to hypothesize that hallucinations in this boy were consequent to a transient impairment of REM sleep inhibitory mechanisms, with the appearance of dream-like hallucinations during wake. Citation: Vita MG; Batocchi AP; Dittoni S; Losurdo A; Cianfoni A; Stefanini MC; Vollono C; Della Marca G; Mariotti P. Visual hallucinations and pontine demyelination in a child: possible REM dissociation? J Clin Sleep Med 2008;4(6):588–590. PMID:19110890

Comparison of the efficacies of patching and penalization therapies for the treatment of amblyopia patients

PubMed Central

Cabi, Cemalettin; Sayman Muslubas, Isil Bahar; Aydin Oral, Ayse Yesim; Dastan, Metin

2014-01-01

AIM To compare the efficacies of patching and penalization therapies for the treatment of amblyopia patients. METHODS The records of 64 eyes of 50 patients 7 to 16y of age who had presented to our clinics with a diagnosis of amblyopia, were evaluated retrospectively. Forty eyes of 26 patients who had received patching therapy and 24 eyes of 24 patients who had received penalization therapy included in this study. The latencies and amplitudes of visual evoked potential (VEP) records and best corrected visual acuities (BCVA) of these two groups were compared before and six months after the treatment. RESULTS In both patching and the penalization groups, the visual acuities increased significantly following the treatments (P<0.05). The latency measurements of the P100 wave obtained at 1.0°, 15 arc min. Patterns of both groups significantly decreased following the 6-months-treatment. However, the amplitude measurements increased (P<0.05). CONCLUSION The patching and the penalization methods, which are the main methods used in the treatment of amblyopia, were also effective over the age of 7y, which has been accepted as the critical age for the treatment of amblyopia. PMID:24967195

Effects of symbol type and numerical distance on the human event-related potential.

PubMed

Jiang, Ting; Qiao, Sibing; Li, Jin; Cao, Zhongyu; Gao, Xuefei; Song, Yan; Xue, Gui; Dong, Qi; Chen, Chuansheng

2010-01-01

This study investigated the influence of the symbol type and numerical distance of numbers on the amplitudes and peak latencies of event-related potentials (ERPs). Our aim was to (1) determine the point in time of magnitude information access in visual number processing; and (2) identify at what stage the advantage of Arabic digits over Chinese verbal numbers occur. ERPs were recorded from 64 scalp sites while subjects (n=26) performed a classification task. Results showed that larger ERP amplitudes were elicited by numbers with distance-close condition in comparison to distance-far condition in the VPP component over centro-frontal sites. Furthermore, the VPP latency varied as a function of the symbol type, but the N170 did not. Such results demonstrate that magnitude information access takes place as early as 150 ms after onset of visual number stimuli and the advantage of Arabic digits over verbal numbers should be localized to the VPP component. We establish the VPP component as a critical ERP component to report in studies of numerical cognition and our results call into question the N170/VPP association hypothesis and the serial-stage model of visual number comparison processing.

A unified selection signal for attention and reward in primary visual cortex.

PubMed

Stănişor, Liviu; van der Togt, Chris; Pennartz, Cyriel M A; Roelfsema, Pieter R

2013-05-28

Stimuli associated with high rewards evoke stronger neuronal activity than stimuli associated with lower rewards in many brain regions. It is not well understood how these reward effects influence activity in sensory cortices that represent low-level stimulus features. Here, we investigated the effects of reward information in the primary visual cortex (area V1) of monkeys. We found that the reward value of a stimulus relative to the value of other stimuli is a good predictor of V1 activity. Relative value biases the competition between stimuli, just as has been shown for selective attention. The neuronal latency of this reward value effect in V1 was similar to the latency of attentional influences. Moreover, V1 neurons with a strong value effect also exhibited a strong attention effect, which implies that relative value and top-down attention engage overlapping, if not identical, neuronal selection mechanisms. Our findings demonstrate that the effects of reward value reach down to the earliest sensory processing levels of the cerebral cortex and imply that theories about the effects of reward coding and top-down attention on visual representations should be unified.

[Factorial division of the visual N1 wave and functional significance].

PubMed

Munoz-Ruata, J; Caro-Martinez, E

2011-05-16

It has been argued if the frontal, N1a, is the early part of the occipito-temporal, N1b, or there are two different waves. It is also not clear whether the N1 of distractor is equivalent to the target N1, neither to distinguish these four waves has some functional value. We performed a principal component analysis of latencies and amplitudes of N1 derived from an oddball visual paradigm in a sample of 82 persons with intellectual disability, and factor scores were correlated with measures of intellectual performance on the Wechsler Intelligence Scale for Children-Fourth Edition. There is not significant dependency between N1a and N1b waves. The N1 from the target stimulus is functionally different to the N1 from the distractor. The N1a 'target' is related to the perceptual reasoning while the N1a 'distractor' is related to the working memory. The correlation between latencies and amplitudes of the target stimuli in posterior locations suggests that, similar to as observed in auditory areas, there is a visual synchronization with the prefrontal cortex; its dysfunction may explain some of the perceptual problems of people with intellectual disabilities.

Visual Processing Recruits the Auditory Cortices in Prelingually Deaf Children and Influences Cochlear Implant Outcomes.

PubMed

Liang, Maojin; Chen, Yuebo; Zhao, Fei; Zhang, Junpeng; Liu, Jiahao; Zhang, Xueyuan; Cai, Yuexin; Chen, Suijun; Li, Xianghui; Chen, Ling; Zheng, Yiqing

2017-09-01

Although visual processing recruitment of the auditory cortices has been reported previously in prelingually deaf children who have a rapidly developing brain and no auditory processing, the visual processing recruitment of auditory cortices might be different in processing different visual stimuli and may affect cochlear implant (CI) outcomes. Ten prelingually deaf children, 4 to 6 years old, were recruited for the study. Twenty prelingually deaf subjects, 4 to 6 years old with CIs for 1 year, were also recruited; 10 with well-performing CIs, 10 with poorly performing CIs. Ten age and sex-matched normal-hearing children were recruited as controls. Visual ("sound" photo [photograph with imaginative sound] and "nonsound" photo [photograph without imaginative sound]) evoked potentials were measured in all subjects. P1 at Oz and N1 at the bilateral temporal-frontal areas (FC3 and FC4) were compared. N1 amplitudes were strongest in the deaf children, followed by those with poorly performing CIs, controls and those with well-performing CIs. There was no significant difference between controls and those with well-performing CIs. "Sound" photo stimuli evoked a stronger N1 than "nonsound" photo stimuli. Further analysis showed that only at FC4 in deaf subjects and those with poorly performing CIs were the N1 responses to "sound" photo stimuli stronger than those to "nonsound" photo stimuli. No significant difference was found for the FC3 and FC4 areas. No significant difference was found in N1 latencies and P1 amplitudes or latencies. The results indicate enhanced visual recruitment of the auditory cortices in prelingually deaf children. Additionally, the decrement in visual recruitment of auditory cortices was related to good CI outcomes.

The primary visual cortex in the neural circuit for visual orienting

NASA Astrophysics Data System (ADS)

Zhaoping, Li

The primary visual cortex (V1) is traditionally viewed as remote from influencing brain's motor outputs. However, V1 provides the most abundant cortical inputs directly to the sensory layers of superior colliculus (SC), a midbrain structure to command visual orienting such as shifting gaze and turning heads. I will show physiological, anatomical, and behavioral data suggesting that V1 transforms visual input into a saliency map to guide a class of visual orienting that is reflexive or involuntary. In particular, V1 receives a retinotopic map of visual features, such as orientation, color, and motion direction of local visual inputs; local interactions between V1 neurons perform a local-to-global computation to arrive at a saliency map that highlights conspicuous visual locations by higher V1 responses. The conspicuous location are usually, but not always, where visual input statistics changes. The population V1 outputs to SC, which is also retinotopic, enables SC to locate, by lateral inhibition between SC neurons, the most salient location as the saccadic target. Experimental tests of this hypothesis will be shown. Variations of the neural circuit for visual orienting across animal species, with more or less V1 involvement, will be discussed. Supported by the Gatsby Charitable Foundation.

Novel Models of Visual Topographic Map Alignment in the Superior Colliculus

PubMed Central

El-Ghazawi, Tarek A.; Triplett, Jason W.

2016-01-01

The establishment of precise neuronal connectivity during development is critical for sensing the external environment and informing appropriate behavioral responses. In the visual system, many connections are organized topographically, which preserves the spatial order of the visual scene. The superior colliculus (SC) is a midbrain nucleus that integrates visual inputs from the retina and primary visual cortex (V1) to regulate goal-directed eye movements. In the SC, topographically organized inputs from the retina and V1 must be aligned to facilitate integration. Previously, we showed that retinal input instructs the alignment of V1 inputs in the SC in a manner dependent on spontaneous neuronal activity; however, the mechanism of activity-dependent instruction remains unclear. To begin to address this gap, we developed two novel computational models of visual map alignment in the SC that incorporate distinct activity-dependent components. First, a Correlational Model assumes that V1 inputs achieve alignment with established retinal inputs through simple correlative firing mechanisms. A second Integrational Model assumes that V1 inputs contribute to the firing of SC neurons during alignment. Both models accurately replicate in vivo findings in wild type, transgenic and combination mutant mouse models, suggesting either activity-dependent mechanism is plausible. In silico experiments reveal distinct behaviors in response to weakening retinal drive, providing insight into the nature of the system governing map alignment depending on the activity-dependent strategy utilized. Overall, we describe novel computational frameworks of visual map alignment that accurately model many aspects of the in vivo process and propose experiments to test them. PMID:28027309

Influence of Visual Prism Adaptation on Auditory Space Representation.

PubMed

Pochopien, Klaudia; Fahle, Manfred

2017-01-01

Prisms shifting the visual input sideways produce a mismatch between the visual versus felt position of one's hand. Prism adaptation eliminates this mismatch, realigning hand proprioception with visual input. Whether this realignment concerns exclusively the visuo-(hand)motor system or it generalizes to acoustic inputs is controversial. We here show that there is indeed a slight influence of visual adaptation on the perceived direction of acoustic sources. However, this shift in perceived auditory direction can be fully explained by a subconscious head rotation during prism exposure and by changes in arm proprioception. Hence, prism adaptation does only indirectly generalize to auditory space perception.

Effects of spatial congruency on saccade and visual discrimination performance in a dual-task paradigm.

PubMed

Moehler, Tobias; Fiehler, Katja

2014-12-01

The present study investigated the coupling of selection-for-perception and selection-for-action during saccadic eye movement planning in three dual-task experiments. We focused on the effects of spatial congruency of saccade target (ST) location and discrimination target (DT) location and the time between ST-cue and Go-signal (SOA) on saccadic eye movement performance. In two experiments, participants performed a visual discrimination task at a cued location while programming a saccadic eye movement to a cued location. In the third experiment, the discrimination task was not cued and appeared at a random location. Spatial congruency of ST-location and DT-location resulted in enhanced perceptual performance irrespective of SOA. Perceptual performance in spatially incongruent trials was above chance, but only when the DT-location was cued. Saccade accuracy and precision were also affected by spatial congruency showing superior performance when the ST- and DT-location coincided. Saccade latency was only affected by spatial congruency when the DT-cue was predictive of the ST-location. Moreover, saccades consistently curved away from the incongruent DT-locations. Importantly, the effects of spatial congruency on saccade parameters only occurred when the DT-location was cued; therefore, results from experiments 1 and 2 are due to the endogenous allocation of attention to the DT-location and not caused by the salience of the probe. The SOA affected saccade latency showing decreasing latencies with increasing SOA. In conclusion, our results demonstrate that visuospatial attention can be voluntarily distributed upon spatially distinct perceptual and motor goals in dual-task situations, resulting in a decline of visual discrimination and saccade performance.

Goal-Directed and Habit-Like Modulations of Stimulus Processing during Reinforcement Learning.

PubMed

Luque, David; Beesley, Tom; Morris, Richard W; Jack, Bradley N; Griffiths, Oren; Whitford, Thomas J; Le Pelley, Mike E

2017-03-15

Recent research has shown that perceptual processing of stimuli previously associated with high-value rewards is automatically prioritized even when rewards are no longer available. It has been hypothesized that such reward-related modulation of stimulus salience is conceptually similar to an "attentional habit." Recording event-related potentials in humans during a reinforcement learning task, we show strong evidence in favor of this hypothesis. Resistance to outcome devaluation (the defining feature of a habit) was shown by the stimulus-locked P1 component, reflecting activity in the extrastriate visual cortex. Analysis at longer latencies revealed a positive component (corresponding to the P3b, from 550-700 ms) sensitive to outcome devaluation. Therefore, distinct spatiotemporal patterns of brain activity were observed corresponding to habitual and goal-directed processes. These results demonstrate that reinforcement learning engages both attentional habits and goal-directed processes in parallel. Consequences for brain and computational models of reinforcement learning are discussed. SIGNIFICANCE STATEMENT The human attentional network adapts to detect stimuli that predict important rewards. A recent hypothesis suggests that the visual cortex automatically prioritizes reward-related stimuli, driven by cached representations of reward value; that is, stimulus-response habits. Alternatively, the neural system may track the current value of the predicted outcome. Our results demonstrate for the first time that visual cortex activity is increased for reward-related stimuli even when the rewarding event is temporarily devalued. In contrast, longer-latency brain activity was specifically sensitive to transient changes in reward value. Therefore, we show that both habit-like attention and goal-directed processes occur in the same learning episode at different latencies. This result has important consequences for computational models of reinforcement learning. Copyright © 2017 the authors 0270-6474/17/373009-09$15.00/0.

Saccade Generation by the Frontal Eye Fields in Rhesus Monkeys Is Separable from Visual Detection and Bottom-Up Attention Shift

PubMed Central

Lee, Kyoung-Min; Ahn, Kyung-Ha; Keller, Edward L.

2012-01-01

The frontal eye fields (FEF), originally identified as an oculomotor cortex, have also been implicated in perceptual functions, such as constructing a visual saliency map and shifting visual attention. Further dissecting the area’s role in the transformation from visual input to oculomotor command has been difficult because of spatial confounding between stimuli and responses and consequently between intermediate cognitive processes, such as attention shift and saccade preparation. Here we developed two tasks in which the visual stimulus and the saccade response were dissociated in space (the extended memory-guided saccade task), and bottom-up attention shift and saccade target selection were independent (the four-alternative delayed saccade task). Reversible inactivation of the FEF in rhesus monkeys disrupted, as expected, contralateral memory-guided saccades, but visual detection was demonstrated to be intact at the same field. Moreover, saccade behavior was impaired when a bottom-up shift of attention was not a prerequisite for saccade target selection, indicating that the inactivation effect was independent of the previously reported dysfunctions in bottom-up attention control. These findings underscore the motor aspect of the area’s functions, especially in situations where saccades are generated by internal cognitive processes, including visual short-term memory and long-term associative memory. PMID:22761923

Saccade generation by the frontal eye fields in rhesus monkeys is separable from visual detection and bottom-up attention shift.

PubMed

Lee, Kyoung-Min; Ahn, Kyung-Ha; Keller, Edward L

2012-01-01

The frontal eye fields (FEF), originally identified as an oculomotor cortex, have also been implicated in perceptual functions, such as constructing a visual saliency map and shifting visual attention. Further dissecting the area's role in the transformation from visual input to oculomotor command has been difficult because of spatial confounding between stimuli and responses and consequently between intermediate cognitive processes, such as attention shift and saccade preparation. Here we developed two tasks in which the visual stimulus and the saccade response were dissociated in space (the extended memory-guided saccade task), and bottom-up attention shift and saccade target selection were independent (the four-alternative delayed saccade task). Reversible inactivation of the FEF in rhesus monkeys disrupted, as expected, contralateral memory-guided saccades, but visual detection was demonstrated to be intact at the same field. Moreover, saccade behavior was impaired when a bottom-up shift of attention was not a prerequisite for saccade target selection, indicating that the inactivation effect was independent of the previously reported dysfunctions in bottom-up attention control. These findings underscore the motor aspect of the area's functions, especially in situations where saccades are generated by internal cognitive processes, including visual short-term memory and long-term associative memory.

Monitoring Global Food Security with New Remote Sensing Products and Tools

NASA Astrophysics Data System (ADS)

Budde, M. E.; Rowland, J.; Senay, G. B.; Funk, C. C.; Husak, G. J.; Magadzire, T.; Verdin, J. P.

2012-12-01

Global agriculture monitoring is a crucial aspect of monitoring food security in the developing world. The Famine Early Warning Systems Network (FEWS NET) has a long history of using remote sensing and crop modeling to address food security threats in the form of drought, floods, pests, and climate change. In recent years, it has become apparent that FEWS NET requires the ability to apply monitoring and modeling frameworks at a global scale to assess potential impacts of foreign production and markets on food security at regional, national, and local levels. Scientists at the U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center and the University of California Santa Barbara (UCSB) Climate Hazards Group have provided new and improved data products as well as visualization and analysis tools in support of the increased mandate for remote monitoring. We present our monitoring products for measuring actual evapotranspiration (ETa), normalized difference vegetation index (NDVI) in a near-real-time mode, and satellite-based rainfall estimates and derivatives. USGS FEWS NET has implemented a Simplified Surface Energy Balance (SSEB) model to produce operational ETa anomalies for Africa and Central Asia. During the growing season, ETa anomalies express surplus or deficit crop water use, which is directly related to crop condition and biomass. We present current operational products and provide supporting validation of the SSEB model. The expedited Moderate Resolution Imaging Spectroradiometer (eMODIS) production system provides FEWS NET with an improved NDVI dataset for crop and rangeland monitoring. eMODIS NDVI provides a reliable data stream with a relatively high spatial resolution (250-m) and short latency period (less than 12 hours) which allows for better operational vegetation monitoring. We provide an overview of these data and cite specific applications for crop monitoring. FEWS NET uses satellite rainfall estimates as inputs for monitoring agricultural food production and driving crop water balance models. We present a series of derived rainfall products and provide an update on efforts to improve satellite-based estimates. We also present advancements in monitoring tools, namely, the Early Warning eXplorer (EWX) and interactive rainfall and NDVI time series viewers. The EWX is a data analysis and visualization tool that allows users to rapidly visualize multiple remote sensing datasets and compare standardized anomaly maps and time series. The interactive time series viewers allow users to analyze rainfall and NDVI time series over multiple spatial domains. New and improved data products and more targeted analysis tools are a necessity as food security monitoring requirements expand and resources become limited.

Ultra-high contrast retinal display system for single photoreceptor psychophysics

PubMed Central

Domdei, Niklas; Domdei, Lennart; Reiniger, Jenny L.; Linden, Michael; Holz, Frank G.; Roorda, Austin; Harmening, Wolf M.

2017-01-01

Due to the enormous dynamic range of human photoreceptors in response to light, studying their visual function in the intact retina challenges the stimulation hardware, specifically with regard to the displayable luminance contrast. The adaptive optics scanning laser ophthalmoscope (AOSLO) is an optical platform that focuses light to extremely small retinal extents, approaching the size of single photoreceptor cells. However, the current light modulation techniques produce spurious visible backgrounds which fundamentally limit experimental options. To remove unwanted background light and to improve contrast for high dynamic range visual stimulation in an AOSLO, we cascaded two commercial fiber-coupled acousto-optic modulators (AOMs) and measured their combined optical contrast. By compensating for zero-point differences in the individual AOMs, we demonstrate a multiplicative extinction ratio in the cascade that was in accordance with the extinction ratios of both single AOMs. When latency differences in the AOM response functions were individually corrected, single switch events as short as 50 ns with radiant power contrasts up to 1:1010 were achieved. This is the highest visual contrast reported for any display system so far. We show psychophysically that this contrast ratio is sufficient to stimulate single foveal photoreceptor cells with small and bright enough visible targets that do not contain a detectable background. Background-free stimulation will enable photoreceptor testing with custom adaptation lights. Furthermore, a larger dynamic range in displayable light levels can drive photoreceptor responses in cones as well as in rods. PMID:29359094

Multiple sleep latency measures in narcolepsy and behaviourally induced insufficient sleep syndrome.

PubMed

Marti, Isabelle; Valko, Philipp O; Khatami, Ramin; Bassetti, Claudio L; Baumann, Christian R

2009-12-01

Short mean latencies to the first epoch of non-rapid eye movement sleep stage 1 (NREM1) and the presence of >or= 2 sleep onset REM (SOREM) periods on multiple sleep latency test (MSLT) occur in both narcolepsy-cataplexy (NC) and behaviourally induced insufficient sleep syndrome (BIISS). It is not known whether specific MSLT findings help differentiate the two disorders. We analyzed MSLT data including sleep latencies to and between different sleep stages of 60 age-, gender- and body mass index (BMI)-matched subjects (hypocretin-deficient NC, actigraphy-confirmed BIISS, healthy controls: each 20). Mean latency (in minutes) to NREM1 sleep was significantly shorter in NC (1.8+/-1.5) than in BIISS (4.7+/-2.1, p<0.001) and controls (11.4+/-3.3, p<0.001). Mean latency to NREM2 sleep was similar in NC (8.6+/-4.7) and BIISS (8.1+/-2.7, p=0.64); latency to either NREM2 or rapid eye movement (REM) sleep (i.e., the sum of the sleep latency to NREM1 and the duration of the first NREM1 sleep sequence), however, was shorter in NC (4.4+/-2.9) than in BIISS (7.9+/-3.5, p<0.001). Referring to all naps with SOREM periods, the sequence NREM1-REM-NREM2 was more common (71%) in NC than in BIISS (15%, p<0.001), reflecting the shorter latency from NREM1 to NREM2 in BIISS (3.7+/-2.5) than in NC (6.1+/-5.9, p<0.001). Our findings show that both sleepiness (as measured by NREM1 sleep latency) and REM sleep propensity are higher in NC than in BIISS. Furthermore, our finding of frequent REM sleep prior to NREM2 sleep in NC is in line with the recent assumption of an insufficient NREM sleep intensity in NC. Together with detailed clinical interviews, sleep logs, actigraphy, and nocturnal polysomnography, mean sleep latencies to NREM1

Figure-ground activity in primary visual cortex (V1) of the monkey matches the speed of behavioral response.

PubMed

Supèr, Hans; Spekreijse, Henk; Lamme, Victor A F

2003-06-26

To look at an object its position in the visual scene has to be localized and subsequently appropriate oculo-motor behavior needs to be initiated. This kind of behavior is largely controlled by the cortical executive system, such as the frontal eye field. In this report, we analyzed neural activity in the visual cortex in relation to oculo-motor behavior. We show that in a figure-ground detection task, the strength of late modulated activity in the primary visual cortex correlates with the saccade latency. We propose that this may indicate that the variability of reaction times in the detection of a visual stimulus is reflected in low-level visual areas as well as in high-level areas.

Contribution of color signals to ocular following responses.

PubMed

Matsuura, Kiyoto; Kawano, Kenji; Inaba, Naoko; Miura, Kenichiro

2016-10-01

Ocular following responses (OFRs) are elicited at ultra-short latencies (< 60 ms) by sudden movements of the visual scene. In this study, we investigated the roles of color signals in OFRs in monkeys. To make physiologically isoluminant sinusoidal color gratings, we estimated the physiologically isoluminant points using OFRs and found that the physiologically isoluminant points were nearly independent of the spatiotemporal frequency of the gratings. We recorded OFRs induced by the motion of physiologically isoluminant color gratings and found that OFRs elicited by the motion of color gratings had different spatiotemporal frequency tuning from those elicited by the motion of luminance gratings. Additionally, OFRs to isoluminant color gratings had smaller peak responses, suggesting that color signals weakly contribute to OFRs compared with luminance signals. OFRs to the motion of stimuli composed of luminance and color signals were also examined. We found that color signals largely contributed to OFRs under low luminance signals regardless of whether color signals moved in the same or opposite direction to luminance signals. These results provide evidence of the multichannel visual computations underlying motor responses. We conclude that, in everyday situations, color information contributes cooperatively with luminance information to the generation of ocular tracking behaviors. © 2016 Federation of European Neuroscience Societies and John Wiley & Sons Ltd.

Morphology of the Vestibular Utricule in Toadfish, Opsanus Tau

NASA Technical Reports Server (NTRS)

Bass, L.; Smith, J.; Twombly, A.; Boyle, Richard; Varelas, Ehsanian J.; Johanson, C.

2003-01-01

The uticle is an otolith organ in the vertebrate inner ear that provides gravitoinertial acceleration information into the vestibular reflex pathways. The aim of the present study was to provide an anatomical description of this structure in the adult oyster toadfish, and establish a morphological basis for interpretation of subsequent functional studies. Light, scanning electron and transmission electron microscopy were applied to visualize the sensory epithelium and its neural innervation. Electrophysiological techniques were used to identify utricular afferents by their response to translation stimuli. Similar to nerve afferents supplying the semicircular canals and lagena, utricular afferents commonly exhibit a short-latency increase of firing rate in response to electrical activation of the central efferent pathway. Afferents were labeled with biocytin either intraaxonally or with extracellular bulk deposits. Light microscope images of serial thick sections were used to make three-dimensional reconstructions of individual labeled afferents to identify the dendritic morphology with respect to epithelial location. Scanning electron microscopy was used to visualize the surface of the otolith mass facing the otolith membrane, and the hair cell polarization patterns of strioler and extrastriolar regions. Transmission electron micrographs of serial thin sections were compiled to create a three-dimensional reconstruction of the labeled afferent over a segment of its dendritic field and to examine the hair cell-afferent synaptic contacts.

An evil face? Verbal evaluative multi-CS conditioning enhances face-evoked mid-latency magnetoencephalographic responses

PubMed Central

Junghöfer, Markus; Rehbein, Maimu Alissa; Maitzen, Julius; Schindler, Sebastian

2017-01-01

Abstract Humans have a remarkable capacity for rapid affective learning. For instance, using first-order US such as odors or electric shocks, magnetoencephalography (MEG) studies of multi-CS conditioning demonstrate enhanced early (<150 ms) and mid-latency (150–300 ms) visual evoked responses to affectively conditioned faces, together with changes in stimulus evaluation. However, particularly in social contexts, human affective learning is often mediated by language, a class of complex higher-order US. To elucidate mechanisms of this type of learning, we investigate how face processing changes following verbal evaluative multi-CS conditioning. Sixty neutral expression male faces were paired with phrases about aversive crimes (30) or neutral occupations (30). Post conditioning, aversively associated faces evoked stronger magnetic fields in a mid-latency interval between 220 and 320 ms, localized primarily in left visual cortex. Aversively paired faces were also rated as more arousing and more unpleasant, evaluative changes occurring both with and without contingency awareness. However, no early MEG effects were found, implying that verbal evaluative conditioning may require conceptual processing and does not engage rapid, possibly sub-cortical, pathways. Results demonstrate the efficacy of verbal evaluative multi-CS conditioning and indicate both common and distinct neural mechanisms of first- and higher-order multi-CS conditioning, thereby informing theories of associative learning. PMID:28008078

An evil face? Verbal evaluative multi-CS conditioning enhances face-evoked mid-latency magnetoencephalographic responses.

PubMed

Junghöfer, Markus; Rehbein, Maimu Alissa; Maitzen, Julius; Schindler, Sebastian; Kissler, Johanna

2017-04-01

Humans have a remarkable capacity for rapid affective learning. For instance, using first-order US such as odors or electric shocks, magnetoencephalography (MEG) studies of multi-CS conditioning demonstrate enhanced early (<150 ms) and mid-latency (150-300 ms) visual evoked responses to affectively conditioned faces, together with changes in stimulus evaluation. However, particularly in social contexts, human affective learning is often mediated by language, a class of complex higher-order US. To elucidate mechanisms of this type of learning, we investigate how face processing changes following verbal evaluative multi-CS conditioning. Sixty neutral expression male faces were paired with phrases about aversive crimes (30) or neutral occupations (30). Post conditioning, aversively associated faces evoked stronger magnetic fields in a mid-latency interval between 220 and 320 ms, localized primarily in left visual cortex. Aversively paired faces were also rated as more arousing and more unpleasant, evaluative changes occurring both with and without contingency awareness. However, no early MEG effects were found, implying that verbal evaluative conditioning may require conceptual processing and does not engage rapid, possibly sub-cortical, pathways. Results demonstrate the efficacy of verbal evaluative multi-CS conditioning and indicate both common and distinct neural mechanisms of first- and higher-order multi-CS conditioning, thereby informing theories of associative learning. © The Author (2016). Published by Oxford University Press.

Impaired Oculomotor Behavior of Children with Developmental Dyslexia in Antisaccades and Predictive Saccades Tasks

PubMed Central

Lukasova, Katerina; Silva, Isadora P.; Macedo, Elizeu C.

2016-01-01

Analysis of eye movement patterns during tracking tasks represents a potential way to identify differences in the cognitive processing and motor mechanisms underlying reading in dyslexic children before the occurrence of school failure. The current study aimed to evaluate the pattern of eye movements in antisaccades, predictive saccades and visually guided saccades in typical readers and readers with developmental dyslexia. The study included 30 children (age M = 11; SD = 1.67), 15 diagnosed with developmental dyslexia (DG) and 15 regular readers (CG), matched by age, gender and school grade. Cognitive assessment was performed prior to the eye-tracking task during which both eyes were registered using the Tobii® 1750 eye-tracking device. The results demonstrated a lower correct antisaccades rate in dyslexic children compared to the controls (p < 0.001, DG = 25%, CC = 37%). Dyslexic children also made fewer saccades in predictive latency (p < 0.001, DG = 34%, CG = 46%, predictive latency within −300–120 ms with target as 0 point). No between-group difference was found for visually guided saccades. In this task, both groups showed shorter latency for right-side targets. The results indicated altered oculomotor behavior in dyslexic children, which has been reported in previous studies. We extend these findings by demonstrating impaired implicit learning of target's time/position patterns in dyslexic children. PMID:27445945

Effect of attentional load on audiovisual speech perception: evidence from ERPs.

PubMed

Alsius, Agnès; Möttönen, Riikka; Sams, Mikko E; Soto-Faraco, Salvador; Tiippana, Kaisa

2014-01-01

Seeing articulatory movements influences perception of auditory speech. This is often reflected in a shortened latency of auditory event-related potentials (ERPs) generated in the auditory cortex. The present study addressed whether this early neural correlate of audiovisual interaction is modulated by attention. We recorded ERPs in 15 subjects while they were presented with auditory, visual, and audiovisual spoken syllables. Audiovisual stimuli consisted of incongruent auditory and visual components known to elicit a McGurk effect, i.e., a visually driven alteration in the auditory speech percept. In a Dual task condition, participants were asked to identify spoken syllables whilst monitoring a rapid visual stream of pictures for targets, i.e., they had to divide their attention. In a Single task condition, participants identified the syllables without any other tasks, i.e., they were asked to ignore the pictures and focus their attention fully on the spoken syllables. The McGurk effect was weaker in the Dual task than in the Single task condition, indicating an effect of attentional load on audiovisual speech perception. Early auditory ERP components, N1 and P2, peaked earlier to audiovisual stimuli than to auditory stimuli when attention was fully focused on syllables, indicating neurophysiological audiovisual interaction. This latency decrement was reduced when attention was loaded, suggesting that attention influences early neural processing of audiovisual speech. We conclude that reduced attention weakens the interaction between vision and audition in speech.

Cortical Neural Synchronization Underlies Primary Visual Consciousness of Qualia: Evidence from Event-Related Potentials

PubMed Central

Babiloni, Claudio; Marzano, Nicola; Soricelli, Andrea; Cordone, Susanna; Millán-Calenti, José Carlos; Del Percio, Claudio; Buján, Ana

2016-01-01

This article reviews three experiments on event-related potentials (ERPs) testing the hypothesis that primary visual consciousness (stimulus self-report) is related to enhanced cortical neural synchronization as a function of stimulus features. ERP peak latency and sources were compared between “seen” trials and “not seen” trials, respectively related and unrelated to the primary visual consciousness. Three salient features of visual stimuli were considered (visuospatial, emotional face expression, and written words). Results showed the typical visual ERP components in both “seen” and “not seen” trials. There was no statistical difference in the ERP peak latencies between the “seen” and “not seen” trials, suggesting a similar timing of the cortical neural synchronization regardless the primary visual consciousness. In contrast, ERP sources showed differences between “seen” and “not seen” trials. For the visuospatial stimuli, the primary consciousness was related to higher activity in dorsal occipital and parietal sources at about 400 ms post-stimulus. For the emotional face expressions, there was greater activity in parietal and frontal sources at about 180 ms post-stimulus. For the written letters, there was higher activity in occipital, parietal and temporal sources at about 230 ms post-stimulus. These results hint that primary visual consciousness is associated with an enhanced cortical neural synchronization having entirely different spatiotemporal characteristics as a function of the features of the visual stimuli and possibly, the relative qualia (i.e., visuospatial, face expression, and words). In this framework, the dorsal visual stream may be synchronized in association with the primary consciousness of visuospatial and emotional face contents. Analogously, both dorsal and ventral visual streams may be synchronized in association with the primary consciousness of linguistic contents. In this line of reasoning, the ensemble of the cortical neural networks underpinning the single visual features would constitute a sort of multi-dimensional palette of colors, shapes, regions of the visual field, movements, emotional face expressions, and words. The synchronization of one or more of these cortical neural networks, each with its peculiar timing, would produce the primary consciousness of one or more of the visual features of the scene. PMID:27445750

A low-latency high-port count optical switch with optical delay line buffering for disaggregated data centers

NASA Astrophysics Data System (ADS)

Moralis-Pegios, M.; Terzenidis, N.; Mourgias-Alexandris, G.; Vyrsokinos, K.; Pleros, N.

2018-02-01

Disaggregated Data Centers (DCs) have emerged as a powerful architectural framework towards increasing resource utilization and system power efficiency, requiring, however, a networking infrastructure that can ensure low-latency and high-bandwidth connectivity between a high-number of interconnected nodes. This reality has been the driving force towards high-port count and low-latency optical switching platforms, with recent efforts concluding that the use of distributed control architectures as offered by Broadcast-and-Select (BS) layouts can lead to sub-μsec latencies. However, almost all high-port count optical switch designs proposed so far rely either on electronic buffering and associated SerDes circuitry for resolving contention or on buffer-less designs with packet drop and re-transmit procedures, unavoidably increasing latency or limiting throughput. In this article, we demonstrate a 256x256 optical switch architecture for disaggregated DCs that employs small-size optical delay line buffering in a distributed control scheme, exploiting FPGA-based header processing over a hybrid BS/Wavelength routing topology that is implemented by a 16x16 BS design and a 16x16 AWGR. Simulation-based performance analysis reveals that even the use of a 2- packet optical buffer can yield <620nsec latency with >85% throughput for up to 100% loads. The switch has been experimentally validated with 10Gb/s optical data packets using 1:16 optical splitting and a SOA-MZI wavelength converter (WC) along with fiber delay lines for the 2-packet buffer implementation at every BS outgoing port, followed by an additional SOA-MZI tunable WC and the 16x16 AWGR. Error-free performance in all different switch input/output combinations has been obtained with a power penalty of <2.5dB.

Influence of limb temperature on cutaneous silent periods.

PubMed

Kofler, Markus; Valls-Solé, Josep; Vasko, Peter; Boček, Václav; Štetkárová, Ivana

2014-09-01

The cutaneous silent period (CSP) is a spinal inhibitory reflex mediated by small-diameter afferents (A-delta fibers) and large-diameter efferents (alpha motoneurons). The effect of limb temperature on CSPs has so far not been assessed. In 27 healthy volunteers (11 males; age 22-58 years) we recorded median nerve motor and sensory action potentials, median nerve F-wave and CSPs induced by noxious digit II stimulation in thenar muscles in a baseline condition at room temperature, and after randomly submersing the forearm in 42 °C warm or 15 °C cold water for 20 min each. In cold limbs, distal and proximal motor and sensory latencies as well as F-wave latencies were prolonged. Motor and sensory nerve conduction velocities were reduced. Compound motor and sensory nerve action potential amplitudes did not differ significantly from baseline. CSP onset and end latencies were more delayed than distal and proximal median nerve motor and sensory latencies, whereas CSP duration was not affected. In warm limbs, opposite but smaller changes were seen in nerve conduction studies and CSPs. The observed CSP shift "en bloc" towards longer latencies without affecting CSP duration during limb cooling concurs with slower conduction velocity in both afferent and efferent fibers. Disparate conduction slowing in afferents and efferents, however, suggests that nociceptive EMG suppression is mediated by fibers of different size in the afferent than in the efferent arm, indirectly supporting the contribution of A-delta fibers as the main afferent input. Limb temperature should be taken into account when testing CSPs in the clinical setting, as different limb temperatures affect CSP latencies more than large-diameter fiber conduction function. Copyright © 2014 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.

Oculomotor Anomalies in Attention-Deficit/Hyperactivity Disorder: Evidence for Deficits in Response Preparation and Inhibition

ERIC Educational Resources Information Center

Mahone, E. Mark; Mostofsky, Stewart H.; Lasker, Adrian G.; Zee, David; Denckla, Martha B.

2009-01-01

Girls, but not boys, with attention deficit hyperactivity disorder (ADHD) have significantly longer visually guided saccades latencies. It is found that sex differences in children with ADHD extend beyond symptom presentation to the development of oculomotor control.

Visual search and spatial attention: ERPs in focussed and divided attention conditions.

PubMed

Wijers, A A; Okita, T; Mulder, G; Mulder, L J; Lorist, M M; Poiesz, R; Scheffers, M K

1987-08-01

ERPs and performance were measured in divided and focussed attention visual search tasks. In focussed attention tasks, to-be-attended and to-be-ignored letters were presented simultaneously. We varied display load, mapping conditions and display size. RT, P3b-latency and negativity in the ERP associated with controlled search all increased with display load. Each of these measures showed selectivity of controlled search, in that they decreased with focussing of attention. An occipital N230, on the other hand, was not sensitive to focussing of attention, but was primarily affected by display load. ERPs to both attended and unattended targets in focussed attention conditions showed and N2 compared to nontargets, suggesting that both automatic and controlled letter classifications are possible. These effects were not affected by display size. Consistent mapping resulted in shorter RT and P3b-latency in divided attention conditions, compared to varied mapping conditions, but had no effect in focussed attention conditions.

When mental fatigue maybe characterized by Event Related Potential (P300) during virtual wheelchair navigation.

PubMed

Lamti, Hachem A; Gorce, Philippe; Ben Khelifa, Mohamed Moncef; Alimi, Adel M

2016-12-01

The goal of this study is to investigate the influence of mental fatigue on the event related potential P300 features (maximum pick, minimum amplitude, latency and period) during virtual wheelchair navigation. For this purpose, an experimental environment was set up based on customizable environmental parameters (luminosity, number of obstacles and obstacles velocities). A correlation study between P300 and fatigue ratings was conducted. Finally, the best correlated features supplied three classification algorithms which are MLP (Multi Layer Perceptron), Linear Discriminate Analysis and Support Vector Machine. The results showed that the maximum feature over visual and temporal regions as well as period feature over frontal, fronto-central and visual regions were correlated with mental fatigue levels. In the other hand, minimum amplitude and latency features didn't show any correlation. Among classification techniques, MLP showed the best performance although the differences between classification techniques are minimal. Those findings can help us in order to design suitable mental fatigue based wheelchair control.

Indomethacin treatment prior to pentylenetetrazole-induced seizures downregulates the expression of il1b and cox2 and decreases seizure-like behavior in zebrafish larvae.

PubMed

Barbalho, Patrícia Gonçalves; Lopes-Cendes, Iscia; Maurer-Morelli, Claudia Vianna

2016-03-09

It has been demonstrated that the zebrafish model of pentylenetetrazole (PTZ)-evoked seizures and the well-established rodent models of epilepsy are similar pertaining to behavior, electrographic features, and c-fos expression. Although this zebrafish model is suitable for studying seizures, to date, inflammatory response after seizures has not been investigated using this model. Because a relationship between epilepsy and inflammation has been established, in the present study we investigated the transcript levels of the proinflammatory cytokines interleukin-1 beta (il1b) and cyclooxygenase-2 (cox2a and cox2b) after PTZ-induced seizures in the brain of zebrafish 7 days post fertilization. Furthermore, we exposed the fish to the nonsteroidal anti-inflammatory drug indomethacin prior to PTZ, and we measured its effect on seizure latency, number of seizure behaviors, and mRNA expression of il1b, cox2b, and c-fos. We used quantitative real-time PCR to assess the mRNA expression of il1b, cox2a, cox2b, and c-fos, and visual inspection was used to monitor seizure latency and the number of seizure-like behaviors. We found a short-term upregulation of il1b, and we revealed that cox2b, but not cox2a, was induced after seizures. Indomethacin treatment prior to PTZ-induced seizures downregulated the mRNA expression of il1b, cox2b, and c-fos. Moreover, we observed that in larvae exposed to indomethacin, seizure latency increased and the number of seizure-like behaviors decreased. This is the first study showing that il1b and cox-2 transcripts are upregulated following PTZ-induced seizures in zebrafish. In addition, we demonstrated the anticonvulsant effect of indomethacin based on (1) the inhibition of PTZ-induced c-fos transcription, (2) increase in seizure latency, and (3) decrease in the number of seizure-like behaviors. Furthermore, anti-inflammatory effect of indomethacin is clearly demonstrated by the downregulation of the mRNA expression of il1b and cox2b. Our results are supported by previous evidences suggesting that zebrafish is a suitable alternative for studying inflammation, seizures, and the effect of anti-inflammatory compounds on seizure suppression.

The development of cortico-motoneuronal projections investigated using magnetic brain stimulation in the infant macaque.

PubMed

Flament, D; Hall, E J; Lemon, R N

1992-02-01

1. The effects of magnetic brain stimulation on electromyographic (EMG) activity recorded from arm and hand muscles have been investigated in five infant and six adult macaque monkeys under ketamine sedation. 2. In the adults, brief, short-latency EMG responses could be readily evoked with magnetic stimuli of 40-50% of the maximum stimulator output (1.5 T). 3. In a cross-sectional study of five infant macaques, it was difficult to evoke EMG responses in young infants (less than 5 months old). Clear short-latency responses were first evoked in an animal 5.75 months old. This change was accompanied by an increase in the probability of occurrence of the responses. 4. In a longitudinal study of two infant monkeys over a period ranging from 2.5 to 14.5 months of age we found that clear short-latency responses were first evoked at 4 and at 5.5 months, respectively. In both animals there was a steady fall in response threshold which reached the adult range at 6.5 and 8 months, respectively. EMG responses in animals older than 8 months were indistinguishable from those in adults. 5. In the longitudinal study we also noted that the latency of EMG responses to magnetic brain stimulation declined with age. Since there were no comparable changes in the peripheral conduction time in these animals, we attribute this result to a decrease in central conduction time. 6. Parallel behavioural observations of the natural behaviour of the same animals within a colony indicated that mature precision movements of the fingers were not used until 5-6 months of age. 7. In two adult monkeys, the latency of EMG responses evoked in the extensor digitorum and first dorsal interosseous muscles by direct stimulation of the corticospinal tract, via electrodes implanted in the medullary pyramids, was found to be 0.7-1.7 ms shorter than that of responses evoked by magnetic stimuli. It is argued that at least the earliest component of these latter responses is conducted over the cortico-motoneuronal pathway. 8. The mechanisms likely to contribute to the late appearance of EMG responses to brain stimulation are discussed. One of these is probably the establishment of mature cortico-motoneuronal connections, which are not present at birth.

Comprehensive Oculomotor Behavioral Response Assessment (COBRA)

NASA Technical Reports Server (NTRS)

Stone, Leland S. (Inventor); Liston, Dorion B. (Inventor)

2017-01-01

An eye movement-based methodology and assessment tool may be used to quantify many aspects of human dynamic visual processing using a relatively simple and short oculomotor task, noninvasive video-based eye tracking, and validated oculometric analysis techniques. By examining the eye movement responses to a task including a radially-organized appropriately randomized sequence of Rashbass-like step-ramp pursuit-tracking trials, distinct performance measurements may be generated that may be associated with, for example, pursuit initiation (e.g., latency and open-loop pursuit acceleration), steady-state tracking (e.g., gain, catch-up saccade amplitude, and the proportion of the steady-state response consisting of smooth movement), direction tuning (e.g., oblique effect amplitude, horizontal-vertical asymmetry, and direction noise), and speed tuning (e.g., speed responsiveness and noise). This quantitative approach may provide fast and results (e.g., a multi-dimensional set of oculometrics and a single scalar impairment index) that can be interpreted by one without a high degree of scientific sophistication or extensive training.

Neurologic features of chronic Minamata disease (organic mercury poisoning) certified at autopsy.

PubMed

Uchino, M; Okajima, T; Eto, K; Kumamoto, T; Mishima, I; Ando, M

1995-08-01

To better understand the neurologic events related to chronic Minamata disease (organic mercury poisoning), we studied data from 77 patients with Minamata disease as certified at autopsies performed from 1976 to 1994 (mean age: 72.3 years). Major neurologic findings included: sensory impairment in 80.5% of the patients which was limited to the extremities in 42.9%. Impairment of lower extremity coordination was present in 35.8% of the patients, constriction of the visual fields in 28.8%, and retrocochlear hearing loss in 15.3%. There was no correlation between the degree of cerebellar incoordination and the methylmercury concentration in the cerebellum. Compared with the classic type of Minamata disease, the incidence of major neurologic findings was markedly decreased. In light of these findings, supplemental examinations including brain computed tomography (CT), magnetic resonance imaging (MRI), short latency somatosensory evoked potential (SSEP), or tremogram may be necessary to clinically diagnose Minamata disease, especially in atypical or mild cases.

Recovery cycle times of inferior colliculus neurons in the awake bat measured with spike counts and latencies

PubMed Central

Sayegh, Riziq; Aubie, Brandon; Fazel-Pour, Siavosh; Faure, Paul A.

2012-01-01

Neural responses in the mammalian auditory midbrain (inferior colliculus; IC) arise from complex interactions of synaptic excitation, inhibition, and intrinsic properties of the cell. Temporally selective duration-tuned neurons (DTNs) in the IC are hypothesized to arise through the convergence of excitatory and inhibitory synaptic inputs offset in time. Synaptic inhibition can be inferred from extracellular recordings by presenting pairs of pulses (paired tone stimulation) and comparing the evoked responses of the cell to each pulse. We obtained single unit recordings from the IC of the awake big brown bat (Eptesicus fuscus) and used paired tone stimulation to measure the recovery cycle times of DTNs and non-temporally selective auditory neurons. By systematically varying the interpulse interval (IPI) of the paired tone stimulus, we determined the minimum IPI required for a neuron's spike count or its spike latency (first- or last-spike latency) in response to the second tone to recover to within ≥50% of the cell's baseline count or to within 1 SD of it's baseline latency in response to the first tone. Recovery times of shortpass DTNs were significantly shorter than those of bandpass DTNs, and recovery times of bandpass DTNs were longer than allpass neurons not selective for stimulus duration. Recovery times measured with spike counts were positively correlated with those measured with spike latencies. Recovery times were also correlated with first-spike latency (FSL). These findings, combined with previous studies on duration tuning in the IC, suggest that persistent inhibition is a defining characteristic of DTNs. Herein, we discuss measuring recovery times of neurons with spike counts and latencies. We also highlight how persistent inhibition could determine neural recovery times and serve as a potential mechanism underlying the precedence effect in humans. Finally, we explore implications of recovery times for DTNs in the context of bat hearing and echolocation. PMID:22933992

Learning Complex Grammar in the Virtual Classroom: A Comparison of Processing Instruction, Structured Input, Computerized Visual Input Enhancement, and Traditional Instruction

ERIC Educational Resources Information Center

Russell, Victoria

2012-01-01

This study investigated the effects of processing instruction (PI) and structured input (SI) on the acquisition of the subjunctive in adjectival clauses by 92 second-semester distance learners of Spanish. Computerized visual input enhancement (VIE) was combined with PI and SI in an attempt to increase the salience of the targeted grammatical form…

Effects of low-frequency repetitive transcranial magnetic stimulation on event-related potential P300

NASA Astrophysics Data System (ADS)

Torii, Tetsuya; Sato, Aya; Iwahashi, Masakuni; Iramina, Keiji

2012-04-01

The present study analyzed the effects of repetitive transcranial magnetic stimulation (rTMS) on brain activity. P300 latency of event-related potential (ERP) was used to evaluate the effects of low-frequency and short-term rTMS by stimulating the supramarginal gyrus (SMG), which is considered to be the related area of P300 origin. In addition, the prolonged stimulation effects on P300 latency were analyzed after applying rTMS. A figure-eight coil was used to stimulate left-right SMG, and intensity of magnetic stimulation was 80% of motor threshold. A total of 100 magnetic pulses were applied for rTMS. The effects of stimulus frequency at 0.5 or 1 Hz were determined. Following rTMS, an odd-ball task was performed and P300 latency of ERP was measured. The odd-ball task was performed at 5, 10, and 15 min post-rTMS. ERP was measured prior to magnetic stimulation as a control. Electroencephalograph (EEG) was measured at Fz, Cz, and Pz that were indicated by the international 10-20 electrode system. Results demonstrated that different effects on P300 latency occurred between 0.5-1 Hz rTMS. With 1 Hz low-frequency magnetic stimulation to the left SMG, P300 latency decreased. Compared to the control, the latency time difference was approximately 15 ms at Cz. This decrease continued for approximately 10 min post-rTMS. In contrast, 0.5 Hz rTMS resulted in delayed P300 latency. Compared to the control, the latency time difference was approximately 20 ms at Fz, and this delayed effect continued for approximately 15 min post-rTMS. Results demonstrated that P300 latency varied according to rTMS frequency. Furthermore, the duration of the effect was not similar for stimulus frequency of low-frequency rTMS.

Migratory and resident blue tits Cyanistes caeruleus differ in their reaction to a novel object

NASA Astrophysics Data System (ADS)

Nilsson, Anna L. K.; Nilsson, Jan-Åke; Alerstam, Thomas; Bäckman, Johan

2010-11-01

Individuals differ consistently in their behavioural reactions towards novel objects and new situations. Reaction to novelty is one part of a suit of individually consistent behaviours called coping strategies or personalities and is often summarised as bold or shy behaviour. Coping strategies could be particularly important for migrating birds exposed to novel environments on their journeys. We compared the average approach latencies to a novel object among migrants and residents in partially migratory blue tits Cyanistes caeruleus. In this test, we found migrating blue tits to have shorter approach latencies than had resident ones. Behavioural reactions to novelty can affect the readiness to migrate and short approach latency may have an adaptive value during migration. Individual behaviour towards novelty might be incorporated among the factors associated with migratory or resident behaviour in a partially migratory population.

DNA Methyltransferase Activity is Required for Memory- Related Neural Plasticity in the Lateral Amygdala

PubMed Central

Maddox, Stephanie A.; Watts, Casey S.; Schafe, Glenn E.

2014-01-01

We have previously shown that auditory Pavlovian fear conditioning is associated with an increase in DNA methyltransferase (DNMT) expression in the lateral amygdala (LA) and that intra-LA infusion or bath application of an inhibitor of DNMT activity impairs the consolidation of an auditory fear memory and long-term potentiation (LTP) at thalamic and cortical inputs to the LA, in vitro. In the present study, we use awake behaving neurophysiological techniques to examine the role of DNMT activity in memory-related neurophysiological changes accompanying fear memory consolidation and reconsolidation in the LA, in vivo. We show that auditory fear conditioning results in a training-related enhancement in the amplitude of short-latency auditory-evoked field potentials (AEFPs) in the LA. Intra-LA infusion of a DNMT inhibitor impairs both fear memory consolidation and, in parallel, the consolidation of training-related neural plasticity in the LA; that is, short-term memory (STM) and short-term training-related increases in AEFP amplitude in the LA are intact, while long-term memory (LTM) and long-term retention of training-related increases in AEFP amplitudes are impaired. In separate experiments, we show that intra-LA infusion of a DNMT inhibitor following retrieval of an auditory fear memory has no effect on post-retrieval STM or short-term retention of training-related changes in AEFP amplitude in the LA, but significantly impairs both post-retrieval LTM and long-term retention of AEFP amplitude changes in the LA. These findings are the first to demonstrate the necessity of DNMT activity in the consolidation and reconsolidation of memory-associated neural plasticity, in vivo. PMID:24291571

The Sound of Vision Project: On the Feasibility of an Audio-Haptic Representation of the Environment, for the Visually Impaired

PubMed Central

Jóhannesson, Ómar I.; Balan, Oana; Unnthorsson, Runar; Moldoveanu, Alin; Kristjánsson, Árni

2016-01-01

The Sound of Vision project involves developing a sensory substitution device that is aimed at creating and conveying a rich auditory representation of the surrounding environment to the visually impaired. However, the feasibility of such an approach is strongly constrained by neural flexibility, possibilities of sensory substitution and adaptation to changed sensory input. We review evidence for such flexibility from various perspectives. We discuss neuroplasticity of the adult brain with an emphasis on functional changes in the visually impaired compared to sighted people. We discuss effects of adaptation on brain activity, in particular short-term and long-term effects of repeated exposure to particular stimuli. We then discuss evidence for sensory substitution such as Sound of Vision involves, while finally discussing evidence for adaptation to changes in the auditory environment. We conclude that sensory substitution enterprises such as Sound of Vision are quite feasible in light of the available evidence, which is encouraging regarding such projects. PMID:27355966

The role of middle latency evoked potentials in early prediction of favorable outcomes among patients with severe ischemic brain injuries.

PubMed

Zhang, Yan; Wang, Miao; Su, Ying Ying

2014-10-15

To explore the role of middle latency evoked potentials (EPs) as predictors for favorable outcome in patients with severe ischemic brain injuries by comparing the prognostic ability of short latency somatosensory and auditory evoked potentials (SLSEP and BAEP) with middle latency somatosensory and auditory evoked potentials (MLSEP and MLAEP). MLSEP, MLAEP, SLSEP and BAEP were recorded in 112 patients with severe ischemic brain injuries (Glasgow Coma Scale ≤ 8). Among them, 83 patients suffered from cerebral ischemic stroke and 29 suffered from anoxic-ischemic encephalopathy after cardiopulmonary resuscitation between 1 and 7 days after the onset of stroke. Outcomes were reviewed 6 months later using the Glasgow Outcome Scale (GOS). A GOS score of 4-5 was considered as a good outcome while a score of 1-3 was considered as poor. By using the prognostic authenticity analysis of predictors for good outcome, at least unilateral N20 of the SLSEP exit and at least unilateral N60 of the MLSEP exit showed the highest sensitivity which was 100% (95% CI: 86.7%-100%). The bilateral normal N60 showed a high specificity of 97.5% (95% CI: 90.4%-99.6%). It also showed the highest positive likelihood ratio of 6.25% (95% CI: 1.28%-30.59%), which was superior to N20 of SLSEP, V of BAEP, and Pa of MLAEP. The analysis demonstrated that the area under the curve for MLSEP grading was the highest (0.838) compared to that of SLSEP grading (0.784), MLAEP grading (0.659) and BAEP grading (0.621). Compared with using N20 of SLSEP analysis alone, adding MLSEP improves the outcome prediction in patients with severe ischemic brain injuries. When an outcome is uncertain after initial evaluation using short-latency EPs, MLSEP is valuable to be used from the first week to further improve prognostication in these patients. Copyright © 2014 Elsevier B.V. All rights reserved.

Processing of Unattended Emotional Visual Scenes

ERIC Educational Resources Information Center

Calvo, Manuel G.; Nummenmaa, Lauri

2007-01-01

Prime pictures of emotional scenes appeared in parafoveal vision, followed by probe pictures either congruent or incongruent in affective valence. Participants responded whether the probe was pleasant or unpleasant (or whether it portrayed people or animals). Shorter latencies for congruent than for incongruent prime-probe pairs revealed affective…

Applications of pain-related evoked potentials and short-latency somatosensory evoked potentials in acupuncture research: a narrative review.

PubMed

Lin, Chi; Ma, Liangxiao; Zhu, Shipeng; Hu, Nijuan; Wang, Pei; Zhang, Peng; Qi, Dandan; Hao, Jie; Li, Jing; Xin, Siyuan; Zhu, Jiang

2015-10-01

To review and discuss the Chinese and English literature on the use of pain-related evoked potentials (PREP) and short-latency somatosensory EP (SLSEP) in acupuncture research. China National Knowledge Infrastructure Database and MEDLINE were searched for the following key words: acupuncture and PREP or SLSEP. Thirty-seven articles were included in the review. Researchers usually use PREPs to study the analgesic effect of acupuncture, observe influential factors, or for mechanistic exploration. In the SLSEP studies, researchers focused on response characteristics of acupuncture, acupoint specificity, and influential factors of the treatment. There were some problems with the study design and conclusions. Researchers could use PREP and SLSEP to objectively validate the effects of acupuncture and explore its mechanisms using nerve electrophysiology. Further studies can benefit from observing more acupoints' effects using PREPs or SLSEPs and investigating the placebo effect of acupuncture.

Dynamical Adaptation in Photoreceptors

PubMed Central

Clark, Damon A.; Benichou, Raphael; Meister, Markus; Azeredo da Silveira, Rava

2013-01-01

Adaptation is at the heart of sensation and nowhere is it more salient than in early visual processing. Light adaptation in photoreceptors is doubly dynamical: it depends upon the temporal structure of the input and it affects the temporal structure of the response. We introduce a non-linear dynamical adaptation model of photoreceptors. It is simple enough that it can be solved exactly and simulated with ease; analytical and numerical approaches combined provide both intuition on the behavior of dynamical adaptation and quantitative results to be compared with data. Yet the model is rich enough to capture intricate phenomenology. First, we show that it reproduces the known phenomenology of light response and short-term adaptation. Second, we present new recordings and demonstrate that the model reproduces cone response with great precision. Third, we derive a number of predictions on the response of photoreceptors to sophisticated stimuli such as periodic inputs, various forms of flickering inputs, and natural inputs. In particular, we demonstrate that photoreceptors undergo rapid adaptation of response gain and time scale, over ∼ 300 ms—i. e., over the time scale of the response itself—and we confirm this prediction with data. For natural inputs, this fast adaptation can modulate the response gain more than tenfold and is hence physiologically relevant. PMID:24244119

Insensitivity of visual short-term memory to irrelevant visual information.

PubMed

Andrade, Jackie; Kemps, Eva; Werniers, Yves; May, Jon; Szmalec, Arnaud

2002-07-01

Several authors have hypothesized that visuo-spatial working memory is functionally analogous to verbal working memory. Irrelevant background speech impairs verbal short-term memory. We investigated whether irrelevant visual information has an analogous effect on visual short-term memory, using a dynamic visual noise (DVN) technique known to disrupt visual imagery (Quinn & McConnell, 1996b). Experiment I replicated the effect of DVN on pegword imagery. Experiments 2 and 3 showed no effect of DVN on recall of static matrix patterns, despite a significant effect of a concurrent spatial tapping task. Experiment 4 showed no effect of DVN on encoding or maintenance of arrays of matrix patterns, despite testing memory by a recognition procedure to encourage visual rather than spatial processing. Serial position curves showed a one-item recency effect typical of visual short-term memory. Experiment 5 showed no effect of DVN on short-term recognition of Chinese characters, despite effects of visual similarity and a concurrent colour memory task that confirmed visual processing of the characters. We conclude that irrelevant visual noise does not impair visual short-term memory. Visual working memory may not be functionally analogous to verbal working memory, and different cognitive processes may underlie visual short-term memory and visual imagery.

Multisensory processing of naturalistic objects in motion: a high-density electrical mapping and source estimation study.

PubMed

Senkowski, Daniel; Saint-Amour, Dave; Kelly, Simon P; Foxe, John J

2007-07-01

In everyday life, we continuously and effortlessly integrate the multiple sensory inputs from objects in motion. For instance, the sound and the visual percept of vehicles in traffic provide us with complementary information about the location and motion of vehicles. Here, we used high-density electrical mapping and local auto-regressive average (LAURA) source estimation to study the integration of multisensory objects in motion as reflected in event-related potentials (ERPs). A randomized stream of naturalistic multisensory-audiovisual (AV), unisensory-auditory (A), and unisensory-visual (V) "splash" clips (i.e., a drop falling and hitting a water surface) was presented among non-naturalistic abstract motion stimuli. The visual clip onset preceded the "splash" onset by 100 ms for multisensory stimuli. For naturalistic objects early multisensory integration effects beginning 120-140 ms after sound onset were observed over posterior scalp, with distributed sources localized to occipital cortex, temporal lobule, insular, and medial frontal gyrus (MFG). These effects, together with longer latency interactions (210-250 and 300-350 ms) found in a widespread network of occipital, temporal, and frontal areas, suggest that naturalistic objects in motion are processed at multiple stages of multisensory integration. The pattern of integration effects differed considerably for non-naturalistic stimuli. Unlike naturalistic objects, no early interactions were found for non-naturalistic objects. The earliest integration effects for non-naturalistic stimuli were observed 210-250 ms after sound onset including large portions of the inferior parietal cortex (IPC). As such, there were clear differences in the cortical networks activated by multisensory motion stimuli as a consequence of the semantic relatedness (or lack thereof) of the constituent sensory elements.

Neural Correlates of Expert Visuomotor Performance in Badminton Players.

PubMed

Hülsdünker, Thorben; Strüder, Heiko K; Mierau, Andreas

2016-11-01

Elite/skilled athletes participating in sports that require the initiation of targeted movements in response to visual cues under critical time pressure typically outperform nonathletes in a visuomotor reaction task. However, the exact physiological mechanisms of this advantage remain unclear. Therefore, this study aimed to determine the neurophysiological processes contributing to superior visuomotor performance in athletes using visual evoked potential (VEP). Central and peripheral determinants of visuomotor reaction time were investigated in 15 skilled badminton players and 28 age-matched nonathletic controls. To determine the speed of visual signal perception in the cortex, chromatic and achromatic pattern reversal stimuli were presented, and VEP values were recorded with a 64-channel EEG system. Further, a simple visuomotor reaction task was performed to investigate the transformation of the visual into a motor signal in the brain as well as the timing of muscular activation. Amplitude and latency of VEP (N75, P100, and N145) revealed that the athletes did not significantly differ from the nonathletes. However, visuomotor reaction time was significantly reduced in the athletes compared with nonathletes (athletes = 234.9 ms, nonathletes = 260.3 ms, P = 0.015). This was accompanied by an earlier activation of the premotor and supplementary motor areas (athletes = 163.9 ms, nonathletes = 199.1 ms, P = 0.015) as well as an earlier EMG onset (athletes = 167.5 ms, nonathletes = 206.5 ms, P < 0.001). The latency of premotor and supplementary motor area activation was correlated with EMG onset (r = 0.41) and visuomotor reaction time (r = 0.43). The results of this study indicate that superior visuomotor performance in athletes originates from faster visuomotor transformation in the premotor and supplementary motor cortical regions rather than from earlier perception of visual signals in the visual cortex.

Steroids versus No Steroids in Nonarteritic Anterior Ischemic Optic Neuropathy: A Randomized Controlled Trial.

PubMed

Saxena, Rohit; Singh, Digvijay; Sharma, Medha; James, Mathew; Sharma, Pradeep; Menon, Vimla

2018-04-25

To examine the role of oral steroid therapy in the treatment of nondiabetic cases of acute nonarteritic anterior ischemic optic neuropathy (NAAION). Randomized double-blind clinical trial. Thirty-eight patients with acute nondiabetic NAAION divided into 2 arms of 19 patients each. One arm constituted the cases and the other constituted the controls. Cases received oral steroid therapy and were designated the steroid group, whereas controls received placebo and were designated the nonsteroid group. Best-corrected visual acuity (BCVA), visual evoked response (VER), and OCT were performed at baseline, 1 month, 3 months, and 6 months after recruitment into the trial. Best-corrected visual acuity, VER, and retinal nerve fiber layer changes on OCT. Both groups showed significant improvement in BCVA, VER latency, and resolution of disc edema on OCT parameters over 6 months. Final outcome showed no statistically significant difference with regard to visual acuity, although VER was better in the steroid group (P = 0.011). Best-corrected visual acuity, VER amplitude, and VER latency (P = 0.02, P = 0.02, and P = 0.04, respectively) showed a greater percentage improvement in the steroid group, which also saw a faster resolution of disc edema on OCT (1-month follow-up). Oral steroids in acute NAAION did not improve the visual acuity significantly at 6 months. However, they improved resolution of disc edema significantly and enabled a greater improvement in VER parameters. This subtle benefit of oral steroids in NAAION is clinically unimportant and does not provide support for its use. Copyright © 2018 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

Impact of visual and somatosensory deprivation on dynamic balance in adolescent idiopathic scoliosis.

PubMed

Kuo, Fang-Chuan; Wang, Nai-Hwei; Hong, Chang-Zern

2010-11-01

A cross-sectional study of balance control in adolescents with idiopathic scoliosis (AIS). To investigate the impact of visual and somatosensory deprivation on the dynamic balance in AIS patients and to discuss electromyographic (EMG) and posture sway findings. Most studies focus on posture sway in quiet standing controls with little effort on examining muscle-activated patterns in dynamic standing controls. Twenty-two AIS patients and 22 age-matched normal subjects were studied. To understand how visual and somatosensory information could modulate standing balance, balance tests with the Biodex stability system were performed on a moving platform under 3 conditions: visual feedback provided (VF), eyes closed (EC), and standing on a sponge pad with visual feedback provided (SV). Muscular activities of bilateral lumbar multifidi, gluteus medii, and gastrocnemii muscles were recorded with a telemetry EMG system. AIS patients had normal balance index and amplitude and duration of EMG similar to those of normal subjects in the balance test. However, the onset latency of right gastrocnemius was earlier in AIS patients than in normal subjects. In addition, body-side asymmetry was noted on muscle strength and onset latency in AIS subjects. Under EC condition, lumbar multifidi, and gluteus medii activities were higher than those under SV and VF conditions (P < 0.05). Under SV condition, the medial-lateral tilting angle was less than that under VF and EC conditions. In addition, the active duration of right gluteus medius was shorter under SV condition (P < 0.05). The dynamic balance control is particularly disruptive under visual deprivation with increasing lumbar multifidi and gluteus medii activities for compensation. Sponge pad can cause decrease in frontal plane tilting and gluteus medii effort. The asymmetric muscle strength and onset timing are attributed to anatomic deformation as opposed to neurologic etiological factors.

Effect of nicardipine on somatosensory evoked potentials in patients with acute cerebral infarction.

PubMed Central

Yao, L P; Ding, D Y

1990-01-01

We evaluated the effect of nicardipine, a calcium channel blocker, on somatosensory evoked potentials (SEP) in 26 patients with acute cerebral infarction. Post treatment, 58% (15/26) of the N20 and P25 latencies were prolonged in the affected hemispheres; 8% (2/26) were shortened; and 35% (9/26) did not change. The mean N20 and P25 latencies were significantly prolonged two hours post treatment in the affected hemisphere (N20, P less than 0.01, P25 P less than 0.01). Nicardipine (Ni) had no effect on SEP components in the intact hemispheres. Seventy five per cent of the 12 patients with hypertension had a decrease in blood pressure (BP) after taking nicardipine, but there were no undesirable side effects or worsening of neurological signs. Our study demonstrates that nicardipine prolongs the latencies of short-latency components of SEP in the affected hemisphere after acute ischaemic stroke and also decreases BP. These observations suggest that nicardipine therapy might impair neuronal function in the ischaemic zone. PMID:2266363

Overview and Evaluation of Bluetooth Low Energy: An Emerging Low-Power Wireless Technology

PubMed Central

Gomez, Carles; Oller, Joaquim; Paradells, Josep

2012-01-01

Bluetooth Low Energy (BLE) is an emerging low-power wireless technology developed for short-range control and monitoring applications that is expected to be incorporated into billions of devices in the next few years. This paper describes the main features of BLE, explores its potential applications, and investigates the impact of various critical parameters on its performance. BLE represents a trade-off between energy consumption, latency, piconet size, and throughput that mainly depends on parameters such as connInterval and connSlaveLatency. According to theoretical results, the lifetime of a BLE device powered by a coin cell battery ranges between 2.0 days and 14.1 years. The number of simultaneous slaves per master ranges between 2 and 5,917. The minimum latency for a master to obtain a sensor reading is 676 μs, although simulation results show that, under high bit error rate, average latency increases by up to three orders of magnitude. The paper provides experimental results that complement the theoretical and simulation findings, and indicates implementation constraints that may reduce BLE performance.

Reduced Performance of Prey Targeting in Pit Vipers with Contralaterally Occluded Infrared and Visual Senses

PubMed Central

Chen, Qin; Deng, Huanhuan; Brauth, Steven E.; Ding, Li; Tang, Yezhong

2012-01-01

Both visual and infrared (IR) senses are utilized in prey targeting by pit vipers. Visual and IR inputs project to the contralateral optic tectum where they activate both multimodal and bimodal neurons. A series of ocular and pit organ occlusion experiments using the short-tailed pit viper (Gloydius brevicaudus) were conducted to investigate the role of visual and IR information during prey targeting. Compared with unoccluded controls, snakes with either both eyes or pit organs occluded performed more poorly in hunting prey although such subjects still captured prey on 75% of trials. Subjects with one eye and one pit occluded on the same side of the face performed as well as those with bilateral occlusion although these subjects showed a significant targeting angle bias toward the unoccluded side. Performance was significantly poorer when only a single eye or pit was available. Interestingly, when one eye and one pit organ were occluded on opposite sides of the face, performance was poorest, the snakes striking prey on no more than half the trials. These results indicate that, visual and infrared information are both effective in prey targeting in this species, although interference between the two modalities occurs if visual and IR information is restricted to opposite sides of the brain. PMID:22606229

Specificity and timescales of cortical adaptation as inferences about natural movie statistics.

PubMed

Snow, Michoel; Coen-Cagli, Ruben; Schwartz, Odelia

2016-10-01

Adaptation is a phenomenological umbrella term under which a variety of temporal contextual effects are grouped. Previous models have shown that some aspects of visual adaptation reflect optimal processing of dynamic visual inputs, suggesting that adaptation should be tuned to the properties of natural visual inputs. However, the link between natural dynamic inputs and adaptation is poorly understood. Here, we extend a previously developed Bayesian modeling framework for spatial contextual effects to the temporal domain. The model learns temporal statistical regularities of natural movies and links these statistics to adaptation in primary visual cortex via divisive normalization, a ubiquitous neural computation. In particular, the model divisively normalizes the present visual input by the past visual inputs only to the degree that these are inferred to be statistically dependent. We show that this flexible form of normalization reproduces classical findings on how brief adaptation affects neuronal selectivity. Furthermore, prior knowledge acquired by the Bayesian model from natural movies can be modified by prolonged exposure to novel visual stimuli. We show that this updating can explain classical results on contrast adaptation. We also simulate the recent finding that adaptation maintains population homeostasis, namely, a balanced level of activity across a population of neurons with different orientation preferences. Consistent with previous disparate observations, our work further clarifies the influence of stimulus-specific and neuronal-specific normalization signals in adaptation.

Specificity and timescales of cortical adaptation as inferences about natural movie statistics

PubMed Central

Snow, Michoel; Coen-Cagli, Ruben; Schwartz, Odelia

2016-01-01

Adaptation is a phenomenological umbrella term under which a variety of temporal contextual effects are grouped. Previous models have shown that some aspects of visual adaptation reflect optimal processing of dynamic visual inputs, suggesting that adaptation should be tuned to the properties of natural visual inputs. However, the link between natural dynamic inputs and adaptation is poorly understood. Here, we extend a previously developed Bayesian modeling framework for spatial contextual effects to the temporal domain. The model learns temporal statistical regularities of natural movies and links these statistics to adaptation in primary visual cortex via divisive normalization, a ubiquitous neural computation. In particular, the model divisively normalizes the present visual input by the past visual inputs only to the degree that these are inferred to be statistically dependent. We show that this flexible form of normalization reproduces classical findings on how brief adaptation affects neuronal selectivity. Furthermore, prior knowledge acquired by the Bayesian model from natural movies can be modified by prolonged exposure to novel visual stimuli. We show that this updating can explain classical results on contrast adaptation. We also simulate the recent finding that adaptation maintains population homeostasis, namely, a balanced level of activity across a population of neurons with different orientation preferences. Consistent with previous disparate observations, our work further clarifies the influence of stimulus-specific and neuronal-specific normalization signals in adaptation. PMID:27699416