Abstract
SummaryWithdrawal of attention from a visual scene as a result of perceptual load modulates overall levels of activity in human visual cortex [1], but its effects on cortical spatial tuning properties are unknown. Here we show attentional load at fixation affects the spatial tuning of population receptive fields (pRFs) in early visual cortex (V1–3) using functional magnetic resonance imaging (fMRI). We found that, compared to low perceptual load, high perceptual load yielded a ‘blurrier’ representation of the visual field surrounding the attended location and a centrifugal ‘repulsion’ of pRFs. Additional data and control analyses confirmed that these effects were neither due to changes in overall activity levels nor to eye movements. These findings suggest neural ‘tunnel vision’ as a form of distractor suppression under high perceptual load.
Highlights
Perceptual load affects spatial tuning of neuronal populations in human V1–3 under high versus low perceptual load conditions
Effect on population receptive fields (pRFs) was strongest from human early visual cortex
We found that high perceptual load in the central task significantly affected the spatial tuning of early visual cortex for the surrounding visual field (Figure 1B–D)
Summary
= 4.35%, t16 = –3.23, PFWE < 0.01; note that we could map IPS only for a subsample and pRF size in IPS did not change significantly; see Supplemental Figure S1J–L for details) This suggests that perceptual load at fixation induces a repulsion effect on the smaller pRFs of early visual cortex, while attracting the bigger pRFs of higher areas. Fields causing pRF changes whether perceptual load affects other We calculated shifts of pRF centre similar to those we observed (c.f. fundamental properties of neuronal positions (comparing high versus low Supplemental Results for a detailed processing, such as the spatial load) and expressed them relative discussion and control analyses preference of neuronal populations in to the respective pRF sizes.
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