Source localization of visually evoked magnetic fields to stimuli in apparent motion

When at least two spatially separated visual stimuli are delivered sequentially under appropriate temporal conditions, a continuous moving sensation, which is called apparent motion, can be perceived. To investigate the cortical activation associated with visual apparent motion, brain evoked magnetic fields in response to visual half field apparent motion stimuli were measured using a whole-head magnetometer. Peak magnetic fields were observed in the latency range of 170-190 msec after the stimulus onset. The neural sources in this epoch were estimated to lie in the border between occipital and temporal areas in the contralateral hemisphere, which corresponds to the extrastriate visual cortex, including the middle temporal area. The results suggest that the activities in the extrastriate cortex reflect apparent motion perception.