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Nicola van Rijsbergen, Robin Ince, Philippe Schyns; Emotion-specific categorization-relevant information reconstructed from Right and Left Fusiform Gyri. Journal of Vision 2018;18(10):914. doi: 10.1167/18.10.914.
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© ARVO (1962-2015); The Authors (2016-present)
An observer's behavior in categorization tasks depends both on information encoded from their visual field, and task constraints. Where, when and how does the brain's dynamic encoding of visual information interact with task demands to generate a task-relevant representation? Eight observers categorized emotions in a 7AFC task, on "Bubbled" face stimuli while we recorded MEG responses. Using mutual information, we measured the spatio-temporal course of categorical response information in each observer, locating spatio-temporal regions where MEG activity is predictive of observer response. Response information (p< 0.05, corrected), also representing sensitivity to stimulus category, develops in occipital cortex during the early M170, and shows additional spatio-temporal loci common across observers in the rFG (n=7) and lFG (n=8). We then measured the spatio-temporal course of stimulus feature information. During the encoding window of the M170 (up to 250ms), only on average 55% [range 49-95%] of features encoded in occipital cortex reach the lFG and rFG), suggesting selective transmission, with differing feature information on left and right. The proportion of feature information encoded in FG was greater for 'happy', with no other differences between other expressions. To examine how observer response interacts with stimulus feature coding within category, we quantified the representational overlap between response information (computed as correct category decision versus incorrect), and stimulus feature coding, using behavioral redundancy. Redundancy quantifies how much of the trial-by-trial stimulus variation commonly affects both MEG signal and the observer's behavioral response. The proportion of significantly behaviorally relevant features with redundancy in the FG varied with expression, with Happy, Disgust, and Angry showing more redundancy consistently across observers. These results suggest redundancy is tapping an expression dependent process in the Fusiform Gyrus over and above an initial feature selection.
Meeting abstract presented at VSS 2018
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