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DTSTART:20190331T030000
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DTSTART:20191027T020000
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BEGIN:VEVENT
DTSTAMP:20260405T190223Z
UID:5c98f4207b6ec382082647@ist.ac.at
DTSTART:20190411T140000
DTEND:20190411T150000
DESCRIPTION:Speaker: Gergo Orban\nhosted by Gasper Tkacik\nAbstract: Spike 
 count correlations (SCCs) are ubiquitous in sensory cortices\, are charact
 erized by rich structure\, and arise from structured internal dynamics. Ho
 wever\, most theories of visual perception treat contributions of neurons 
 to the representation of stimuli independently and focus on mean responses
 . Here\, we argue that\, in a functional model of visual perception\, feat
 uring probabilistic inference over a hierarchy of features\, inferences ab
 out high-level features modulate inferences about low-level features ultim
 ately introducing structured internal dynamics and patterns in SCCs. Speci
 fically\, high-level inferences for complex stimuli establish the local co
 ntext in which neurons in the primary visual cortex (V1) interpret stimuli
 . Since the local context differentially affects multiple neurons\, this c
 onjecture predicts specific modulations in the fine structure of SCCs as s
 timulus identity and\, more importantly\, stimulus complexity varies. We d
 esigned experiments with natural and synthetic stimuli to measure the fine
  structure of SCCs in V1 of awake behaving macaques and assessed their dep
 endence on stimulus identity and stimulus statistics. We show that the fin
 e structure of SCCs is specific to the identity of natural stimuli and cha
 nges in SCCs are independent of changes in response mean. Critically\, we 
 demonstrate that stimulus specificity of SCCs in V1 can be directly manipu
 lated by altering the amount of high-order structure in synthetic stimuli.
  Finally\, we show that simple phenomenological models of V1 activity cann
 ot account for the observed SCC patterns and conclude that the stimulus de
 pendence of SCCs is a natural consequence of structured internal dynamics 
 in a hierarchical probabilistic model of natural images.
LOCATION:Raiffeisen Lecture Hall\, Central Building\, ISTA
ORGANIZER:abonvent@ist.ac.at
SUMMARY:Gergo Orban: Stimulus complexity shapes response correlations in pr
 imary visual cortex
URL:https://talks-calendar.ista.ac.at/events/1879
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