抄録
We examined underlying mechanisms of apparent motion illusion of beta movement by obtaining neuromagnetic responses of event-related fields (ERFs). A simple setting for visual stimulation of two circles, presented 10 degrees apart each other horizontally, was used in experiment 1. The first circle of a duration of 16.7 msec was followed by the second with three conditions of stimulus-onset-asynchrony: (a) 16.7 msec almost the two circles seen simultaneously, (b) 83.3 msec perceived optimally as beta movement, and (c) 549.8 msec occurred isolatedly. In experiment 2, three conditions of real motion for visual stimulation were set as: (a) six circles presented successively for one animation, (b) fourteen circles for one animation, and (c) thirty-four circles for one animation. We applied minimum current estimates (MCEs) to obtain the source activity of the ERFs for beta movement, and then calculated an average amplitude for each five 100 msec epoch after second stimulus onset in experiment 1, and after first stimulus onset in experiment 2. As the results, the optimal condition showed maximum activities at the first 100 msec epoch at parietal region in experiment 1, suggesting that the motion components of MCEs were emerging from this epoch. In experiment 2, three conditions of real motion evoked prolonged MCE activities for the temporal and central areas, suggesting these components being changed with the “speed” of motion perception. The neuromagnetic activities of beta movement and motion perception may originate from parietal areas within the 100 msec after the percept of the movement.
