The ability to assess depth depends on many cues, one of which is stereopsis--the determination of the distance of a object from differences in the images in the two eyes. Like color vision, stereoscopic depth perception is frequently defective in humans, but unlike most forms of color blindness, defects in stereopsis must be caused by abnormal wiring in the central nervous system. To understand these defects will thus require an understanding of the normal central- nervous mechanisms for stereopsis. Furthermore, an understanding of how one particular well-defined calculation is done by the central nervous system should shed light on how, in general, the brain performs complex calculations. Cells selective for differences in the images in the two eyes have been described and characterized in primates, but the receptive-field mechanisms underlying stereopsis have only been addressed in anesthetized cats, and not at all in monkeys. The goal of this study is to fill in this large gap in our understanding of binocular interactions and depth perception. A recently developed technique for mapping receptive-fields in alert fixating macaques will be used to determine the receptive-field organization of a large series of neurons in V1. Stereoscopic depth selectivity in each cell will be compared with its receptive-field organization in the two eyes. This should provide an understanding of how binocular interactions are used to generate depth selectivity.
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