Perception of apparent motion in depth: a high-density electrical mapping study in humans.

We evaluated brain activity using 64-channel visual evoked potentials (VEPs) while subjects perceived apparent motion in depth. Checkerboard patterns (CBPs) within small and large circles were presented in turn as experimental conditions. Motion in depth was perceived when the CBP in the large circle was coarser than in the small circle; when coarseness did not change, no motion in depth was perceived. As control conditions only fine or coarse CBPs were presented. We used ANOVA to compare VEPs associated with experimental vs. control conditions and with coarse vs. fine CBPs. Negative potentials at a latency near 190 ms showed statistically significant interactions between these comparisons in the right lateral occipital and posterior parietal areas when apparent motion in depth was perceived. This suggests that higher tiers of the dorsal stream mediate this motion perception.