Non-invasive evaluation of face and motion perception in humans.

The neural mechanisms for the perception of face and motion were studied using psychophysical threshold measurements, event-related potentials (ERPs), and functional magnetic resonance imaging (fMRI). A face-specific ERP component, N170, was recorded over the posterior temporal cortex. Removal of the high-spatial-frequency components of the face altered the perception of familiar faces significantly, and familiarity can facilitate the cortico-cortical processing of facial perceptions. Similarly, the high-spatial-frequency components of the face seemed to be crucial for the recognition of facial expressions. Aging and visuospatial impairments affected motion perception significantly. Two distinct components of motion ERPs, N170 and P200, were recorded over the parietal region. The former was related to horizontal motion perception while the latter reflected the perception of radial optic flow motion. The results of fMRI showed that horizontal movements of objects and radial optic flow motion were perceived differently in the V5/MT and superior parietal lobe. We conclude that an integrated approach can provide useful information on spatial and temporal processing of face and motion non-invasively.