Abstract
Faces convey substantial information, some of which is stable – like identity and gender, and some transient – like expression and head orientation. Face-selective regions in the brain may respond differently to these distinct types of information. To test this, we used a fMRI-adaptation paradigm in rhesus macaques to determine the role of face-selective patches in the processing of facial expressions and head orientation of a monkey avatar. Three subjects (Macaca mulatta) were scanned in a 4.7T Bruker scanner while fixating on blocks of images that varied either in: (1) the expression and head orientation of the avatar; (2) the expression but not head orientation; (3) the head orientation but not expression; or (4) both were held constant. The results showed that face patches in the fundus (AF and MF) of the superior temporal sulcus (STS), as well as in the amygdala, were more sensitive to changes in expression than to changes in head orientation, whereas the anterior lateral (AL) face patch responded more to changes in the avatar’s head orientation and less to expression. This dissociation reinforces existing theories claiming that the fundus of the STS is involved in processing expression, while also providing a new framework for understanding how the visual system simultaneously extracts independent, transient signals from a face. Similar ongoing studies in humans will examine if a parallel dissociation exists in that species, such that STS and ventral temporal cortex are more sensitive to changes in facial expression and head orientation, respectively.