What human brain regions like about moving faces?

Visual perception of moving faces activates parts of the human superior temporal sulcus (STS) whereas static facial information is mainly processed in areas of ventral temporal and lateral occipital cortex. However, recent findings show that the latter regions also respond more to moving faces than to static faces. Here, we investigated the origin of this activation increase, considering the following causes: (i) facial motion per se, (ii) increased static information due to the higher number of frames constituting the movie stimuli, and/or (iii) increased attention towards moving faces. We presented non-rigidly moving faces to subjects in an fMRI scanner. We manipulated static face information and motion fluidity by presenting ordered and scrambled sequences of frames at the original or reduced temporal resolutions. Subjects performed a detection task unrelated to the face stimuli in order to equate attentional influences. Results confirm the increased response due to facial motion in the face-sensitive temporal regions. Activation generally increased with the number of frames but decreased when frames were scrambled. These results indicate that the activation increase induced by moving faces is due to smooth, natural motion and not only to increased static information or attentional modulation