Inhibitory interaction in a split/fusion apparent motion: lack of spatial-frequency selectivity.

Spatial-frequency selectivity of apparent motion (AM) between isolated Gabor patches was examined under two- and three-patch conditions. In the two-patch condition, the likelihood of seeing AM between two Gabor patches was measured with varying frequency difference between the patches. In the three-patch (split/fusion) condition, the likelihood of AM between target patches of the same frequency was measured as a function of the frequency of the inhibiting patch. AM perception in the two-patch condition deteriorated with increasing frequency difference, showing symmetrical spatial-frequency selectivity. On the other hand, the inhibition of AM in the three-patch condition was frequency asymmetric; when the frequency of the inhibiting patch was higher than that of the target patches, the magnitude of inhibition decreased with increasing the frequency of the inhibiting patch. When the frequency of the inhibiting patch was lower, the magnitude of inhibition remained almost constant regardless of the frequency difference between the inhibiting and target patches.