Yan, Y.; Zhan, J.; Garrod, O.; Chen, C.; Ince, R. A. A.; Jack, R.; Schyns, P. G.

Recent theories suggest a new brain pathway dedicated to processing social movement is involved in understanding emotions from biological motion, beyond the well-known ventral and dorsal pathways. However, how this social pathway functions as a network that computes dynamic biological motion signals for perceptual behavior is unchartered. Here, we used a generative model of important facial movements that participants (N = 10) categorized as \"happy,\" \"surprise,\" \"fear,\" \"anger,\" \"disgust,\" \"sad\" while we recorded their MEG brain responses. Using new representational interaction measures (between facial features, MEGt source, and behavioral responses), we reveal per participant a functional social pathway extending from occipital cortex to superior temporal gyrus. Its MEG sources selectively represent, communicate and compose facial movements to disambiguate emotion categorization behavior, while occipital cortex swiftly filters out task-irrelevant identity-defining face shape features. Our findings reveal how social pathway selectively computes complex dynamic social signals to categorize emotions in individual participants.