Contour from motion processing occurs in primary visual cortex.

Relative motion is one of the most salient cues for segmentation of a visual scene into separate objects. This is illustrated by the vivid contours that are perceived when random dot patterns move in different directions. Once motion is halted in such displays the segmentation contours disappear. This makes random dot patterns ideal for the study of contour from motion processing in isolation. Contour from motion processing obviously relies on direction-selective neurons, which are found in many visual cortical areas. It is, however, largely unknown at what level of processing their signals interact to serve the global process of motion-based image segmentation. To answer this question, we recorded visually evoked potentials, both in man and in awake monkey, to a stimulus specifically designed to signal the presence of neuronal activity related to contour from motion processing. We report here that response components specific to contour from motion were elicited only when the stimulus yielded a contour percept. In awake monkey, the sources of these components were located within the supra- and infra-granular layers of primary visual cortex. We conclude that V1 is involved in image segmentation processing.