RT Journal Article
SR Electronic
T1 Category knowledge biases sensory representations in human visual cortex
JF bioRxiv
FD Cold Spring Harbor Laboratory
SP 170845
DO 10.1101/170845
A1 Edward F. Ester
A1 Thomas C. Sprague
A1 John T. Serences
YR 2019
UL http://biorxiv.org/content/early/2019/01/17/170845.abstract
AB Categorization refers to the process of mapping continuous sensory inputs onto discrete concepts. Humans and other animals can readily learn arbitrary categories defined by low-level visual features such as hue and orientation, and behavioral studies indicate that such learning distorts perceptual sensitivity for category-defining features such that discrimination performance for physically similar exemplars from different categories is enhanced and discrimination performance for equally similar exemplars from the same category is reduced. These distortions could result from systematic biases in neural representations that begin at the earlies stages of visual processing We tested this hypothesis in two experiments where human observers learned to classify a set of oriented stimuli into two discrete groups. After behavioral training, we used an inverted encoding model to visualize and quantify population-level neural representations of stimulus orientation from noninvasive measurements of human brain activity (fMRI and EEG) in early visual cortical areas. Reconstructed representations in several of these areas (V1-V3) were systematically biased by category membership, as indicated by shifts in the representation away from the physical stimulus’ orientation and towards the center of the appropriate category. These shifts were strongest for orientations near the category boundary where they would be most beneficial for behavioral performance, predicted participants’ overt category judgments, and emerged rapidly after stimulus onset. Collectively, these results indicate that category information can alter information processing at very early stages of the visual stream.