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Poster Session C: Friday, August 15, 2:00 – 5:00 pm, de Brug & E‑Hall

Deep layers of primary visual cortex encode postdictive perception

Pieter Barkema¹, Christoph Koenig, Joost Haarsma, Peter Kok; ¹University College London, University of London

Presenter: Pieter Barkema

Neural representations in primary visual cortex (V1) are not solely determined by bottom-up retinal inputs, but also reflect top-down modulations, where bottom-up and top-down signals are reflected in different cortical layers. Subjective perception is thought to reflect the integration of these signals. Here, we investigated whether this mechanism generalizes to postdictive perception, when later information affects the perception of earlier sensory input. A feedback hypothesis predicts this temporal integration reaches early sensory cortex, while a feedforward hypothesis predicts that this sensory input is integrated downstream. We induced a postdictive visual illusion with sound and hypothesized that multisensory regions would feed back postdictive information into V1. We tested this hypothesis using layer-specific 7T fMRI (N=24), retinotopic mapping and a postdictive illusion paradigm. We validated the illusion and retinal effects and found no evidence for univariate BOLD increase. Using multivariate analysis, however, we found that activity patterns in the deep, but not the middle, layers of V1 reflected the contents of illusory percepts, in line with the feedback hypothesis. Informational connectivity analyses revealed that this information was shared with the Superior Temporal Gyrus, a multisensory hub. These results reveal that perceptual inference in primary visual cortex can be modulated by top-down information arriving after the fact.

Topic Area: Visual Processing & Computational Vision

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