A magnetoencephalographic study on the components of event-related fields in an apparent motion illusion with changing stimulus shape and color A Imai1, H Takase1, K Tanaka2, Y Uchikawa2 |
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1Department of Psychology, Shinshu University, Japan |
| We explored an apparent motion illusion (beta movement) by obtaining neuromagnetic responses from event-related fields (ERFs). Two stimuli, presented horizontally 10 degrees apart, were used. The first stimulus (S1, a white circle), presented for 16.7 ms, was followed by the second stimulus (S2, a white triangle in Experiment 1, shape-changing condition; and a red circle in Experiment 2, color-changing condition) with three conditions of stimulus-onset asynchrony: (a) at 16.7 ms, the two stimuli were almost simultaneously seen; (b) at 83.3 ms, the motion illusion was optimally perceived; and (c) at 550.0 ms, the stimuli appeared isolated. We applied minimum current estimates (MCEs) to obtain the source activity of ERFs for beta movement, and calculated the average amplitude of five 100-ms epochs after S2 onset. The optimal condition showed MCE amplitudes larger than those in the simultaneous condition at the second 100-ms epoch in both central and parietal areas in Experiment 2, but not in Experiment 1, thereby suggesting that the motion components of MCEs clearly emerged from this epoch for the color-changing condition. Thus, the neuromagnetic activity of beta movement may be evoked for the color-changing condition more easily than for the shape-changing condition and may originate in centro-parietal areas. |
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