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Megumi Fukuda: “Prior expectation shapes dynamics of ambiguous stimulus perception”

 

April 7, 2015  14:00 〜 15:30

1F Conference Rm. A
Megumi Fukuda

PhD student at the University College of London

Abstract:

Our visual system forms conscious visual percepts by resolving ambiguity in visual stimuli. Perception is affected by information derived from its previous history, particularly when making perceptual decisions. Furthermore, predictive coding theory proposes that the brain makes inferences by combining sensory information with expectation (priors) for the world and these priors are subsequently updated based on incoming sensory information (Hohwy et al, 2008). Here, using structure-from- motion bistable perception stimuli, we investigated whether prior expectation for perception biased interpretation of such ambiguous visual information and explored which brain areas coded this expectation. Participants viewed stereoscopic bistable perception stimuli presented intermittently while the perceived direction of the sphereʼs rotation (right or left). To manipulate their expectation, structure-from-motion with depth structure-from-motion and we found Having verified a behavioural effect of prior expectation, we then participantʼs expectation trajectory and explored which regions represent the expectation signal.We found that aSPL and pSPL, areas involving in bistable perception, showed expectation-related signals during pre-stimulus period and late stimulus-presentation period. Collectively, these results suggestthat the combination of stimulus and subjective percept forms expectations that are coded and updated in parietal cortex, and this subsequently shapes interpretation of ambiguous sensory input.