scholarly journals Pre-Stimulus Alpha-Band Phase Gates Afferent Visual Cortex Responses

2021 ◽  
Author(s):  
Wei Dou ◽  
Audrey Morrow ◽  
Luca Iemi ◽  
Jason Samaha
Keyword(s):  
Visual Cortex ◽  
Visual Processing ◽  
Time Window ◽  
Event Related Potentials ◽  
Alpha Phase ◽  
Alpha Activity ◽  
Alpha Band ◽  
Visual Responses ◽  
Alpha Oscillations ◽  
Related Potentials

The neurogenesis of alpha-band (8-13 Hz) activity has been characterized across many different animal experiments. However, the functional role that alpha oscillations play in perception and behavior has largely been attributed to two contrasting hypotheses, with human evidence in favor of either (or both or neither) remaining sparse. On the one hand, alpha generators have been observed in relay sectors of the visual thalamus and are postulated to phasically inhibit afferent visual input in a feedforward manner 1-4. On the other hand, evidence also suggests that the direction of influence of alpha activity propagates backwards along the visual hierarchy, reflecting a feedback influence upon the visual cortex 5-9. The primary source of human evidence regarding the role of alpha phase in visual processing has been on perceptual reports 10-16, which could be modulated either by feedforward or feedback alpha activity. Thus, although these two hypotheses are not mutually exclusive, human evidence clearly supporting either one is lacking. Here, we present human subjects with large, high-contrast visual stimuli that elicit robust C1 event-related potentials (ERP), which peak between 70-80 milliseconds post-stimulus and are thought to reflect afferent primary visual cortex (V1) input 17-20. We find that the phase of ongoing alpha oscillations modulates the global field power (GFP) of the EEG during this first volley of stimulus processing (the C1 time-window). On the standard assumption 21-23 that this early activity reflects postsynaptic potentials being relayed to visual cortex from the thalamus, our results suggest that alpha phase gates visual responses during the first feed-forward sweep of processing.

scholarly journals Human posterior parietal cortex responds to visual stimuli as early as peristriate occipital cortex

2018 ◽  
Author(s):  
Tamar I. Regev ◽  
Jonathan Winawer ◽  
Edden M. Gerber ◽  
Robert T. Knight ◽  
Leon Y. Deouell
Keyword(s):  
Visual Processing ◽  
Posterior Parietal Cortex ◽  
Right Hemisphere ◽  
Intractable Epilepsy ◽  
Event Related Potentials ◽  
Visual Responses ◽  
Baseline Activity ◽  
Visual Areas ◽  
Related Potentials ◽  
Posterior Parietal

AbstractMuch of what is known about the timing of visual processing in the brain is inferred from intracranial studies in monkeys, with human data limited to mainly non-invasive methods with lower spatial resolution. Here, we estimated visual onset latencies from electrocorticographic (ECoG) recordings in a patient who was implanted with 112 sub-dural electrodes, distributed across the posterior cortex of the right hemisphere, for pre-surgical evaluation of intractable epilepsy. Functional MRI prior to surgery was used to determine boundaries of visual areas. The patient was presented with images of objects from several categories. Event Related Potentials (ERPs) were calculated across all categories excluding targets, and statistically reliable onset latencies were determined using a bootstrapping procedure over the single trial baseline activity in individual electrodes. The distribution of onset latencies broadly reflected the known hierarchy of visual areas, with the earliest cortical responses in primary visual cortex, and higher areas showing later responses. A clear exception to this pattern was robust, statistically reliable and spatially localized, very early responses on the bank of the posterior intra-parietal sulcus (IPS). The response in the IPS started nearly simultaneously with responses detected in peristriate visual areas, around 60 milliseconds post-stimulus onset. Our results support the notion of early visual processing in the posterior parietal lobe, not respecting traditional hierarchies, and give direct evidence for the upper limit of onset times of visual responses across the human cortex.

Stereotactic electroencephalography in humans reveals multisensory signal in early visual and auditory cortices

2019 ◽  
Author(s):  
Stefania Ferraro ◽  
Markus J. Van Ackeren ◽  
Roberto Mai ◽  
Laura Tassi ◽  
Francesco Cardinale ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Auditory Cortex ◽  
Auditory Processing ◽  
Multisensory Processing ◽  
Low Frequency ◽  
Event Related Potentials ◽  
Stimulus Onset ◽  
Oscillatory Activity ◽  
Visual Responses ◽  
Related Potentials

AbstractUnequivocally demonstrating the presence of multisensory signals at the earliest stages of cortical processing remains challenging in humans. In our study, we relied on the unique spatio-temporal resolution provided by intracranial stereotactic electroencephalographic (SEEG) recordings in patients with drug-resistant epilepsy to characterize the signal extracted from early visual (calcarine and pericalcarine) and auditory (Heschl’s gyrus and planum temporale) regions during a simple audio-visual oddball task. We provide evidences that both cross-modal responses (visual responses in auditory cortex or the reverse) and multisensory processing (alteration of the unimodal responses during bimodal stimulation) can be observed in intracranial event-related potentials (iERPs) and in power modulations of oscillatory activity at different temporal scales within the first 150 ms after stimulus onset. The temporal profiles of the iERPs are compatible with the hypothesis that MSI occurs by means of direct pathways linking early visual and auditory regions. Our data indicate, moreover, that MSI mainly relies on modulations of the low-frequency bands (foremost the theta band in the auditory cortex and the alpha band in the visual cortex), suggesting the involvement of feedback pathways between the two sensory regions. Remarkably, we also observed high-gamma power modulations by sounds in the early visual cortex, thus suggesting the presence of neuronal populations involved in auditory processing in the calcarine and pericalcarine region in humans.

scholarly journals Intermodal Auditory, Visual, and Tactile Attention Modulates Early Stages of Neural Processing

2009 ◽  
Vol 21 (4) ◽  
pp. 669-683 ◽  
Author(s):  
Christina M. Karns ◽  
Robert T. Knight
Keyword(s):  
Visual Cortex ◽  
Visual Processing ◽  
Auditory Processing ◽  
Event Related Potentials ◽  
Association Cortex ◽  
Neural Processing ◽  
Secondary Association ◽  
Tactile Attention ◽  
Related Potentials ◽  
Visual Onset

We used event-related potentials (ERPs) and gamma band oscillatory responses (GBRs) to examine whether intermodal attention operates early in the auditory, visual, and tactile modalities. To control for the effects of spatial attention, we spatially coregistered all stimuli and varied the attended modality across counterbalanced blocks in an intermodal selection task. In each block, participants selectively responded to either auditory, visual, or vibrotactile stimuli from the stream of intermodal events. Auditory and visual ERPs were modulated at the latencies of early cortical processing, but attention manifested later for tactile ERPs. For ERPs, auditory processing was modulated at the latency of the Na (29 msec), which indexes early cortical or thalamocortical processing and the subsequent P1 (90 msec) ERP components. Visual processing was modulated at the latency of the early phase of the C1 (62–72 msec) thought to be generated in the primary visual cortex and the subsequent P1 and N1 (176 msec). Tactile processing was modulated at the latency of the N160 (165 msec) likely generated in the secondary association cortex. Intermodal attention enhanced early sensory GBRs for all three modalities: auditory (onset 57 msec), visual (onset 47 msec), and tactile (onset 27 msec). Together, these results suggest that intermodal attention enhances neural processing relatively early in the sensory stream independent from differential effects of spatial and intramodal selective attention.

Power and Phase of Alpha Oscillations Reveal an Interaction between Spatial and Temporal Visual Attention

2017 ◽  
Vol 29 (3) ◽  
pp. 480-494 ◽  
Author(s):  
Sayeed A. D. Kizuk ◽  
Kyle E. Mathewson
Keyword(s):  
Visual Processing ◽  
Alpha Phase ◽  
Alpha Power ◽  
Alpha Band ◽  
Target Onset ◽  
Alpha Oscillations ◽  
Perceptual Performance ◽  
Neural Entrainment ◽  
Sensory Activity ◽  
Bias Attention

Oscillatory brain rhythms can bias attention via phase and amplitude changes, which modulate sensory activity, biasing information to be processed or ignored. Alpha band (7–14 Hz) oscillations lateralize with spatial attention and rhythmically inhibit visual activity and awareness through pulses of inhibition. Here we show that human observers' awareness of spatially unattended targets is dependent on both alpha power and alpha phase at target onset. Following a predictive directional cue, alpha oscillations were entrained bilaterally using repetitive visual stimuli. Subsequently, we presented either spatially cued or uncued targets at SOAs either validly or invalidly predicted in time by the entrainers. Temporal validity maximally modulated perceptual performance outside the spatial focus of attention and was associated with both increased alpha power and increased neural entrainment of phase in the hemisphere processing spatially unattended information. The results demonstrate that alpha oscillations represent a pulsating inhibition, which impedes visual processing for unattended space.

scholarly journals Hemispheric Asymmetry in Visual Processing: An Erp Study on Spatial Frequency Gratings

2021 ◽  
Author(s):  
Alice Mado Proverbio ◽  
and Alberto Zani
Keyword(s):  
Spatial Frequency ◽  
Visual Processing ◽  
Visual Information ◽  
Hemispheric Asymmetry ◽  
High Spatial Frequency ◽  
Event Related Potentials ◽  
Repeated Measure ◽  
Sensory Response ◽  
Visual Responses ◽  
Related Potentials

A hemispheric asymmetry is known for the processing of global vs. local visual information. In this study, we investigated the existence of a hemispheric asymmetry for visual processing of low vs. high spatial frequency gratings. Event-related potentials were recorded in a group of healthy right-handed volunteers from 30 scalp sites. Six types of stimuli (1.5, 3 and 6 c/deg gratings) were randomly flashed 180 times in the left and right upper hemi-fields. Stimulus duration was 80 ms and ISI ranged between 850-1000 ms. Participants had to pay attention and respond to targets based on their spatial frequency and location, or to passively look at the stimuli. C1 and P1 visual responses, as well as a later Selection negativity and a P300 components of ERPs were quantified and subjected to repeated-measure ANOVAs. Overall, performance was faster for the RVF, thus suggesting a left hemispheric advantage for attentional selection of local elements. Similarly, the analysis of mean area amplitude of C1 (60-110 ms) sensory response showed a stronger attentional effect (F+L+ vs. F-L+) at left occipital areas, thus suggesting the sensory nature of this hemispheric asymmetry.

scholarly journals Hemispheric Asymmetry in Visual Processing: An ERP Study on Spatial Frequency Gratings

Symmetry ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 180
Author(s):  
Alice Mado Proverbio ◽  
Alberto Zani
Keyword(s):  
Spatial Frequency ◽  
Visual Processing ◽  
Hemispheric Asymmetry ◽  
High Spatial Frequency ◽  
Event Related Potentials ◽  
Repeated Measure ◽  
Right Visual Field ◽  
Sensory Response ◽  
Visual Responses ◽  
Related Potentials

A hemispheric asymmetry for the processing of global versus local visual information is known. In this study, we investigated the existence of a hemispheric asymmetry for the visual processing of low versus high spatial frequency gratings. The event-related potentials were recorded in a group of healthy right-handed volunteers from 30 scalp sites. Six types of stimuli (1.5, 3 and 6 c/deg gratings) were randomly flashed 180 times in the left and right upper hemifields. The stimulus duration was 80 ms, and the interstimulus interval (ISI) ranged between 850 and 1000 ms. Participants paid attention and responded to targets based on their spatial frequency and location. The C1 and P1 visual responses, as well as a later selection negativity and a P300 component of event-related potentials (ERPs), were quantified and subjected to repeated-measure analyses of variance (ANOVAs). Overall, the performance was faster for the right visual field (RVF), thus suggesting a left hemispheric advantage for the attentional selection of local elements. Similarly, the analysis of the mean area amplitude of the C1 (60–110 ms) sensory response showed a stronger attentional effect (F+L+ vs. F−L+) at the left occipital areas, thus suggesting the sensory nature of this hemispheric asymmetry.

scholarly journals Temporal Dynamics of Attention during Encoding versus Maintenance of Working Memory: Complementary Views from Event-related Potentials and Alpha-band Oscillations

2015 ◽  
Vol 27 (3) ◽  
pp. 492-508 ◽  
Author(s):  
Nicholas E. Myers ◽  
Lena Walther ◽  
George Wallis ◽  
Mark G. Stokes ◽  
Anna C. Nobre
Keyword(s):  
Working Memory ◽  
Visual Information ◽  
Temporal Dynamics ◽  
Recall Performance ◽  
Event Related Potentials ◽  
Alpha Band ◽  
Related Potentials ◽  
Frontoparietal Control Network ◽  
Anticipatory Attention ◽  
Processing Differences

Working memory (WM) is strongly influenced by attention. In visual WM tasks, recall performance can be improved by an attention-guiding cue presented before encoding (precue) or during maintenance (retrocue). Although precues and retrocues recruit a similar frontoparietal control network, the two are likely to exhibit some processing differences, because precues invite anticipation of upcoming information whereas retrocues may guide prioritization, protection, and selection of information already in mind. Here we explored the behavioral and electrophysiological differences between precueing and retrocueing in a new visual WM task designed to permit a direct comparison between cueing conditions. We found marked differences in ERP profiles between the precue and retrocue conditions. In line with precues primarily generating an anticipatory shift of attention toward the location of an upcoming item, we found a robust lateralization in late cue-evoked potentials associated with target anticipation. Retrocues elicited a different pattern of ERPs that was compatible with an early selection mechanism, but not with stimulus anticipation. In contrast to the distinct ERP patterns, alpha-band (8–14 Hz) lateralization was indistinguishable between cue types (reflecting, in both conditions, the location of the cued item). We speculate that, whereas alpha-band lateralization after a precue is likely to enable anticipatory attention, lateralization after a retrocue may instead enable the controlled spatiotopic access to recently encoded visual information.

ASSESSING THE IMPACT OF CONGRUENT AND INCONGRUENT STIMULUS IN STROOP TASK, USING EVENT-RELATED POTENTIALS (ERP) IN PATIENTS WITH DEPRESSION

2018 ◽  
Vol 30 (05) ◽  
pp. 1850034
Author(s):  
Yeganeh Shahsavar ◽  
Majid Ghoshuni
Keyword(s):  
Stroop Task ◽  
Time Window ◽  
Event Related Potentials ◽  
Peak Time ◽  
Eeg Signals ◽  
Incongruent Stimulus ◽  
Related Potentials ◽  
Recording Channel ◽  
The Mean ◽  
The Impact

The main goal of this event-related potentials (ERPs) study was to assess the effects of stimulations in Stroop task in brain activities of patients with different degrees of depression. Eighteen patients (10 males, with the mean age [Formula: see text]) were asked to fill out Beck’s depression questionnaire. Electroencephalographic (EEG) signals of subjects were recorded in three channels (Pz, Cz, and Fz) during Stroop test. This test entailed 360 stimulations, which included 120 congruent, 120 incongruent, and 120 neutral stimulations. To analyze the data, 18 time features in each type of stimulus were extracted from the ERP components and the optimal features were selected. The correlation between the subjects’ scores in Beck’s depression questionnaires and the extracted time features in each recording channel was calculated in order to select the best features. Total area, and peak-to-peak time window in the Cz channel in both the congruent and incongruent stimulus showed significant correlation with Beck scores, with [Formula: see text], [Formula: see text] and [Formula: see text], [Formula: see text], respectively. Consequently, given the correlation between time features and the subjects’ Beck scores with different degrees of depression, it can be interpreted that in case of growth in degrees of depression, stimulations involving congruent images would produce more challenging interferences for the patients compared to incongruent stimulations which can be more effective in diagnosing the level of disorder.

scholarly journals Lexical processing deficits in children with developmental language disorder: An event-related potentials study

2015 ◽  
Vol 27 (2) ◽  
pp. 459-476 ◽  
Author(s):  
Sergey A. Kornilov ◽  
James S. Magnuson ◽  
Natalia Rakhlin ◽  
Nicole Landi ◽  
Elena L. Grigorenko
Keyword(s):  
Lexical Processing ◽  
Time Window ◽  
Language Disorder ◽  
Event Related Potentials ◽  
Functional Independence ◽  
Event Related Potential ◽  
Developmental Language Disorder ◽  
Compensatory Mechanisms ◽  
Related Potentials ◽  
Processing Deficits

AbstractLexical processing deficits in children with developmental language disorder (DLD) have been postulated to arise as sequelae of their grammatical deficits (either directly or via compensatory mechanisms) and vice versa. We examined event-related potential indices of lexical processing in children with DLD (n= 23) and their typically developing peers (n= 16) using a picture–word matching paradigm. We found that children with DLD showed markedly reduced N400 amplitudes in response both to auditorily presented words that had initial phonological overlap with the name of the pictured object and to words that were not semantically or phonologically related to the pictured object. Moreover, this reduction was related to behavioral indices of phonological and lexical but not grammatical development. We also found that children with DLD showed a depressed phonological mapping negativity component in the early time window, suggesting deficits in phonological processing or early lexical access. The results are partially consistent with the overactivation account of lexical processing deficits in DLD and point to the relative functional independence of lexical/phonological and grammatical deficits in DLD, supporting a multidimensional view of the disorder. The results also, although indirectly, support the neuroplasticity account of DLD, according to which language impairment affects brain development and shapes the specific patterns of brain responses to language stimuli.

scholarly journals A P300 Brain-Computer Interface With a Reduced Visual Field

2020 ◽  
Vol 14 ◽  
Author(s):  
Luiza Kirasirova ◽  
Vladimir Bulanov ◽  
Alexei Ossadtchi ◽  
Alexander Kolsanov ◽  
Vasily Pyatin ◽  
...  
Keyword(s):  
Visual Field ◽  
Visual Processing ◽  
Classification Accuracy ◽  
Peripheral Vision ◽  
Brain Computer Interface ◽  
Event Related Potentials ◽  
Computer Interface ◽  
Central Visual Field ◽  
P300 Speller ◽  
Related Potentials

A P300 brain-computer interface (BCI) is a paradigm, where text characters are decoded from event-related potentials (ERPs). In a popular implementation, called P300 speller, a subject looks at a display where characters are flashing and selects one character by attending to it. The selection is recognized as the item with the strongest ERP. The speller performs well when cortical responses to target and non-target stimuli are sufficiently different. Although many strategies have been proposed for improving the BCI spelling, a relatively simple one received insufficient attention in the literature: reduction of the visual field to diminish the contribution from non-target stimuli. Previously, this idea was implemented in a single-stimulus switch that issued an urgent command like stopping a robot. To tackle this approach further, we ran a pilot experiment where ten subjects operated a traditional P300 speller or wore a binocular aperture that confined their sight to the central visual field. As intended, visual field restriction resulted in a replacement of non-target ERPs with EEG rhythms asynchronous to stimulus periodicity. Changes in target ERPs were found in half of the subjects and were individually variable. While classification accuracy was slightly better for the aperture condition (84.3 ± 2.9%, mean ± standard error) than the no-aperture condition (81.0 ± 2.6%), this difference was not statistically significant for the entire sample of subjects (N = 10). For both the aperture and no-aperture conditions, classification accuracy improved over 4 days of training, more so for the aperture condition (from 72.0 ± 6.3% to 87.0 ± 3.9% and from 72.0 ± 5.6% to 97.0 ± 2.2% for the no-aperture and aperture conditions, respectively). Although in this study BCI performance was not substantially altered, we suggest that with further refinement this approach could speed up BCI operations and reduce user fatigue. Additionally, instead of wearing an aperture, non-targets could be removed algorithmically or with a hybrid interface that utilizes an eye tracker. We further discuss how a P300 speller could be improved by taking advantage of the different physiological properties of the central and peripheral vision. Finally, we suggest that the proposed experimental approach could be used in basic research on the mechanisms of visual processing.

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