Human MT/V5 activity on viewing eye gaze changes in others: A magnetoencephalographic study.

The present study used magnetoencephalography (MEG) to investigate human MT/V5 activity when observing changes in eye gaze. Subjects viewed a face in which the eyes changed to look either directly at (BACK) or away from (AWAY) the subject in a series of apparent motion conditions. BACK involved 2 directions, from left to center (LC) and from right to center (RC). Likewise, AWAY involved 2 directions, from center to left (CL) and from center to right (CR). A clear MEG component, 1M, was elicited with all eye gaze changes. Mean peak latency was 157 ms and was unaffected by stimulus condition. The equivalent current dipole (ECD) was localized to human MT/V5. Two main effects were noted: (1) ECD moment was significantly larger for BACK than for AWAY; and (2) 1M ECD locations were more posterior for AWAY than for BACK. Gaze direction, with LEFT involving CL and RC and RIGHT involving CR and LC, showed no significant effects. These data indicate that MT/V5 responds to gaze direction rather than eye position, and that eye movements directed at the viewer elicit the strongest effects. Processing of gaze change is NOT sensitive to eye direction per se but rather is modulated by eye gaze relative to the viewer.