Competitive Interactions of Attentional Resources in Early Visual Cortex during Sustained Visuospatial Attention within or between Visual Hemifields: Evidence for the Different-hemifield Advantage

2014 ◽  
Vol 26 (5) ◽  
pp. 938-954 ◽  
Author(s):  
Sabrina Walter ◽  
Cliodhna Quigley ◽  
Matthias M. Mueller
Keyword(s):  
Visual Cortex ◽  
Visuospatial Attention ◽  
Competitive Interactions ◽  
Attentional Processing ◽  
Light Emitting ◽  
Attentional Resources ◽  
Early Visual Cortex ◽  
Processing Resources ◽  
Left And Right ◽  
Visual Hemifields

Performing a task across the left and right visual hemifields results in better performance than in a within-hemifield version of the task, termed the different-hemifield advantage. Although recent studies used transient stimuli that were presented with long ISIs, here we used a continuous objective electrophysiological (EEG) measure of competitive interactions for attentional processing resources in early visual cortex, the steady-state visual evoked potential (SSVEP). We frequency-tagged locations in each visual quadrant and at central fixation by flickering light-emitting diodes (LEDs) at different frequencies to elicit distinguishable SSVEPs. Stimuli were presented for several seconds, and participants were cued to attend to two LEDs either in one (Within) or distributed across left and right visual hemifields (Across). In addition, we introduced two reference measures: one for suppressive interactions between the peripheral LEDs by using a task at fixation where attention was withdrawn from the periphery and another estimating the upper bound of SSVEP amplitude by cueing participants to attend to only one of the peripheral LEDs. We found significantly greater SSVEP amplitude modulations in Across compared with Within hemifield conditions. No differences were found between SSVEP amplitudes elicited by the peripheral LEDs when participants attended to the centrally located LEDs compared with when peripheral LEDs had to be ignored in Across and Within trials. Attending to only one LED elicited the same SSVEP amplitude as Across conditions. Although behavioral data displayed a more complex pattern, SSVEP amplitudes were well in line with the predictions of the different-hemifield advantage account during sustained visuospatial attention.

scholarly journals Defining the Units of Competition: Influences of Perceptual Organization on Competitive Interactions in Human Visual Cortex

2010 ◽  
Vol 22 (11) ◽  
pp. 2417-2426 ◽  
Author(s):  
Stephanie A. McMains ◽  
Sabine Kastner
Keyword(s):  
Visual Cortex ◽  
Perceptual Organization ◽  
Visual Processing ◽  
Perceptual Grouping ◽  
Neural Representation ◽  
Competitive Interactions ◽  
Illusory Figure ◽  
Processing Stream ◽  
Neural Processes ◽  
Early Visual Cortex

Multiple stimuli that are present simultaneously in the visual field compete for neural representation. At the same time, however, multiple stimuli in cluttered scenes also undergo perceptual organization according to certain rules originally defined by the Gestalt psychologists such as similarity or proximity, thereby segmenting scenes into candidate objects. How can these two seemingly orthogonal neural processes that occur early in the visual processing stream be reconciled? One possibility is that competition occurs among perceptual groups rather than at the level of elements within a group. We probed this idea using fMRI by assessing competitive interactions across visual cortex in displays containing varying degrees of perceptual organization or perceptual grouping (Grp). In strong Grp displays, elements were arranged such that either an illusory figure or a group of collinear elements were present, whereas in weak Grp displays the same elements were arranged randomly. Competitive interactions among stimuli were overcome throughout early visual cortex and V4, when elements were grouped regardless of Grp type. Our findings suggest that context-dependent grouping mechanisms and competitive interactions are linked to provide a bottom–up bias toward candidate objects in cluttered scenes.

scholarly journals Electrophysiological evidence for temporal dynamics associated with attentional processing in the zoom lens paradigm

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e4538 ◽  
Author(s):  
Qing Zhang ◽  
Tengfei Liang ◽  
Jiafeng Zhang ◽  
Xueying Fu ◽  
Jianlin Wu
Keyword(s):  
Search Task ◽  
Attentional Focus ◽  
Visuospatial Attention ◽  
Zoom Lens ◽  
Lens Model ◽  
Attentional Processing ◽  
Attentional Resources ◽  
Electrophysiological Evidence ◽  
Attentional Scope ◽  
Concentric Circles

BackgroundVisuospatial processing requires wide distribution or narrow focusing of attention to certain regions in space. This mechanism is described by the zoom lens model and predicts an inverse correlation between the efficiency of processing and the size of the attentional scope. Little is known, however, about the exact timing of the effects of attentional scaling on visual searching and whether or not additional processing phases are involved in this process.MethodElectroencephalographic recordings were made while participants performed a visual search task under different attentional scaling conditions. Two concentric circles of different sizes, presented to the participants at the center of a screen modulated the attentional scopes, and search arrays were distributed in the space areas indicated by these concentric circles. To ensure consistent eccentricity of the search arrays across different conditions, we limited our studies to the neural responses evoked by the search arrays distributed in the overlapping region of different attentional scopes.ResultsConsistent with the prediction of the zoom lens model, our behavioral data showed that reaction times for target discrimination of search arrays decreased and the associated error rates also significantly decreased, with narrowing the attentional scope. Results of the event-related potential analysis showed that the target-elicited amplitude of lateral occipital N1, rather than posterior P1, which reflects the earliest visuospatial attentional processing, was sensitive to changes in the scaling of visuospatial attention, indicating that the modulation of the effect of changes in the spatial scale of attention on visual processing occurred after the delay period of P1. The N1 generator exhibited higher activity as the attentional scope narrowed, reflecting more intensive processing resources within the attentional focus. In contrast to N1, the amplitude of N2pc increased with the expansion of the attentional focus, suggesting that observers might further redistribute attentional resources according to the increased task difficulty.ConclusionThese findings provide electrophysiological evidence that the neural activity of the N1 generator is the earliest marker of the zoom lens effect of visual spatial attention. Furthermore, evidence from N2pc shows that there is also a redistribution of attentional resources after the action of the zoom lens mechanism, which allows for better perform of the search task in the context of low attentional resolution. On the basis of the timing of P1, N1, and N2pc, our findings provide compelling evidence that visuospatial attention processing in the zoom lens paradigm involves multi-stage dynamic processing.

scholarly journals Affective Bias without Hemispheric Competition: Evidence for Independent Processing Resources in Each Cortical Hemisphere

2020 ◽  
Vol 32 (5) ◽  
pp. 963-976
Author(s):  
Valeria Bekhtereva ◽  
Matt Craddock ◽  
Matthias M. Müller
Keyword(s):  
Visual Cortex ◽  
Steady State ◽  
Visual Field ◽  
Visual Evoked Potential ◽  
Evoked Potential ◽  
Low Level ◽  
Visual Hemifield ◽  
Early Visual Cortex ◽  
Processing Resources ◽  
Visual Evoked

We assessed the extent of neural competition for attentional processing resources in early visual cortex between foveally presented task stimuli and peripheral emotional distracter images. Task-relevant and distracting stimuli were shown in rapid serial visual presentation (RSVP) streams to elicit the steady-state visual evoked potential, which serves as an electrophysiological marker of attentional resource allocation in early visual cortex. A task-related RSVP stream of symbolic letters was presented centrally at 15 Hz while distracting RSVP streams were displayed at 4 or 6 Hz in the left and right visual hemifields. These image streams always had neutral content in one visual field and would unpredictably switch from neutral to unpleasant content in the opposite visual field. We found that the steady-state visual evoked potential amplitude was consistently modulated as a function of change in emotional valence in peripheral RSVPs, indicating sensory gain in response to distracting affective content. Importantly, the facilitated processing for emotional content shown in one visual hemifield was not paralleled by any perceptual costs in response to the task-related processing in the center or the neutral image stream in the other visual hemifield. Together, our data provide further evidence for sustained sensory facilitation in favor of emotional distracters. Furthermore, these results are in line with previous reports of a “different hemifield advantage” with low-level visual stimuli and are suggestive of independent processing resources in each cortical hemisphere that operate beyond low-level visual cues, that is, with complex images that impact early stages of visual processing via reentrant feedback loops from higher order processing areas.

scholarly journals Faded visual afterimages reappear after TMS over early visual cortex

2018 ◽  
Author(s):  
Engelen T. ◽  
Rademaker R.L. ◽  
Sack A.T
Keyword(s):  
Visual Cortex ◽  
Brain Regions ◽  
Visual Signals ◽  
Visual Inputs ◽  
Before And After ◽  
Inhibitory Feedback ◽  
Integration Sites ◽  
Early Visual Cortex ◽  
Left And Right

AbstractIn the complete absence of small transients in visual inputs (e.g. by experimentally stabilizing an image on the retina, or in everyday life during intent staring), information perceived by the eyes will fade from the perceptual experience. While the mechanisms of visual fading remain poorly understood, one possibility is that higher-level brain regions actively suppress the stable visual signals via targeted inhibitory feedback onto Early Visual Cortex (EVC). Here, we used positive afterimages and multisensory conflict to induce gestaltlike fading of participants’ own hands. In two separate experiments, participants rated the perceived quality of their hands both before and after Transcranial Magnetic Stimulation (TMS) was applied over EVC. In a first experiment, triple pulse TMS was able to make a faded hand appear less faded after the pulses were applied, compared to placebo pulses. A second experiment demonstrated that this was because triple pulse TMS inoculated the removed hand from fading over time. Interestingly, TMS similarly affected the left and right hand, despite being applied only over right EVC. Together, our results suggest that TMS can lift inhibitory processes in EVC and reverse the effects of visual fading. And it might do so by crossing transcollosal connections, or via multimodal integration sites in which both hands are represented.

scholarly journals Population receptive field and connectivity properties of the early visual cortex in human albinism

2019 ◽  
Author(s):  
Khazar Ahmadi ◽  
Anne Herbik ◽  
Markus Wagner ◽  
Martin Kanowski ◽  
Hagen Thieme ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Receptive Field ◽  
Optic Chiasm ◽  
List Type ◽  
Cortical Connectivity ◽  
Cortical Connections ◽  
Visual Hemifield ◽  
Early Visual Cortex ◽  
Visual Hemifields ◽  
Retinal Afferents

AbstractIn albinism, the pathological decussation of the temporal retinal afferents at the optic chiasm leads to superimposed representations of opposing hemifields in the visual cortex. Here, we assessed the equivalence of the two representations and the cortico-cortical connectivity of the early visual areas. Applying fMRI-based population receptive field (pRF)-mapping (both hemifield and bilateral mapping) and connective field (CF)-modeling, we investigated the early visual cortex in 6 albinotic participants and 4 controls. In albinism, superimposed retinotopic representations of the contra- and ipsilateral visual hemifield were observed on the hemisphere contralateral to the stimulated eye. This was confirmed by the observation of bilateral pRFs during bilateral mapping. Hemifield mapping revealed similar pRF-sizes for both hemifield representations throughout V1 to V3. The typical increase of V1-sampling extent for V3 compared to V2 was not found for the albinotic participants. The similarity of the pRF-sizes for opposing visual hemifield representations highlights the equivalence of the two maps in the early visual cortex. The altered V1-sampling extent in V3 indicates the adaptation of cortico-cortical connections to the abnormal input of the visual cortex. These findings thus suggest that conservative developmental mechanisms are complemented by alterations of the extrastriate cortico-cortical connectivity.HighlightspRF mapping confirms cortical overlay of opposing visual hemifields in albinism.Equivalent information processing of both hemifields is indicated by similar pRF sizes.CF modeling indicates changes to the cortico-cortical connections at the level of V3.

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