Dissociable contribution of somatosensory and superior lateral temporal cortices in social face recognition
Résumé
Faces are multi-dimensional stimuli bearing many important social communicative signals, such as gaze direction and emotion expression. To test whether perception of these two facial dimensions relies on different cortical areas within the right hemisphere, we used single-pulse TMS in healthy participants while they performed two distinct tasks on the same face stimuli. TMS was applied over either the right somatosensory cortex or right superior lateral temporal cortex, 100 or 200 ms after the presentation of a face that had various eye gaze directions and emotional expressions. Participants performed a speeded sequential matching task on the faces across the two task conditions. Our results indicate a significant task x stimulation site interaction, showing a selective TMS-related interference following stimulations of the somatosensory cortex during the emotional expression task. Conversely, TMS of the superior lateral temporal cortex interfered with the gaze direction task. We also found that the interference effect was specific to the stimulus content in each condition, affecting the speed of judging gaze shifts (not static eye positions) with TMS over the right superior temporal cortex, and the speed of judging fearful expressions (not happy expressions) with TMS over the right somatosensory cortex. These results provide for the first time a double-dissociation in normal viewers for social face recognition during transient disruption of non-overlapping brain regions, supporting a critical role for somatosensory and superior lateral temporal regions in the perception of fear expression and gaze shift in seen faces, respectively.