THE DIRECTION OF RETINAL MOTION FACILITATES BINOCULAR STEREOPSIS

Visual information from binocular disparity and from relative motion p rovide information about three-dimensional structure and layout of the world. Although the mechanisms that process these cues have typically been studied independently there is now a substantial body of evidenc e that suggests that they interact in the visual pathway. This paper i nvestigates one advantage of such an interaction: whether retinal moti on can be used as a matching constraint in the binocular correspondenc e process. Stimuli that contained identical disparity and motion signa ls but which differed in their fine-scale correlation were created to establish whether the direction, or the speed, of motion could enhance performance in a psychophysical task in which binocular matching is a limiting factor. The results of these experiments provide clear evide nce that different directions of motion, but not different speeds, are processed separately in stereopsis. The results fit well with propert ies of neurons early in the cortical visual pathway which are thought to be involved in determining local matches between features in the tw o eyes' images.