Flexible coding for categorical decisions in the human brain.

Despite the importance of visual categorization for interpreting sensory experiences, little is known about the neural representations that mediate categorical decisions in the human brain. Here, we used psychophysics and pattern classification for the analysis of functional magnetic resonance imaging data to predict the features critical for categorical decisions from brain activity when observers categorized the same stimuli using different rules. Although a large network of cortical and subcortical areas contain information about visual categories, we show that only a subset of these areas shape their selectivity to reflect the behaviorally relevant features rather than simply physical similarity between stimuli. Specifically, temporal and parietal areas show selectivity for the perceived form and motion similarity, respectively. In contrast, frontal areas and the striatum represent the conjunction of spatiotemporal features critical for complex and adaptive categorization tasks and potentially modulate selectivity in temporal and parietal areas. These findings provide novel evidence for flexible neural coding in the human brain that translates sensory experiences to categorical decisions by shaping neural representations across a network of areas with dissociable functional roles in visual categorization.