Distributed representations of face expression and gaze perception in human temporal cortex

Abstract

The perception of facial expression and gaze-direction are important aspects of non-verbal communication. Expressions communicate the internal emotional state of others while gaze-direction offers clues to their attentional focus and intentions. Previous neuroimaging studies have independently shown that the superior temporal sulcus (STS) is more strongly activated by faces displaying expression than by neutral faces and by attending to the gaze-direction rather than the identity of a face. The distinctiveness of the neural representations of these two classes of facial gesture in the human STS has not been investigated. We used functional magnetic resonance imaging and multi-voxel pattern analysis to assess the distinctiveness of the BOLD response evoked in the STS while subjects viewed blocks of faces with differing expressions and directions of gaze. Each block comprises different individuals displaying a single facial expression (Anger, Disgust, Fear, Surprise), a single gaze direction (partial left or right, full left or right), or a neutral expression with direct gaze. Each of 8 time series contained one block of each condition. Distinct regions of activity within the STS and surrounding cortex are seen when the activity evoked by viewing expressions is directly contrasted with the activity evoked by viewing averted-gaze. In an effort to corroborate this effect we performed pattern classification on the voxels in our region of interest using a neural-net classifier. The classifier performance was significantly better than chance indicating that the neural activity in this region carries information that distinguishes these two facial gestures.