Motion integration over space: interaction of the center and surround motion.

Motion integration occurs over a restricted range of visual space. However, there have been studies suggesting interactions among motion detectors operating on widely separated spatial regions. To understand these lateral spatial interactions beyond motion pooling regions, we examined the effect of surrounding motion on the direction of the center stimulus under several stimulus conditions. We have found that there is a motion direction shift of the center stimulus caused by surrounding motion depending on its motion direction, spatial proximity to the center stimulus, contrast, speed, and the extent of motion area. This effect was observed both for monocular and dichoptic presentations of the pattern. However, the perceived direction shift decreased when the spatial frequency ratio of the center and surround stimuli varied, or a non-Fourier motion pattern was used for both center and surround stimuli. We present a model consisting of lateral inhibitory interactions between pattern motion unit networks to explain the direction shift observed in the experiments.