Neuronal Mechanisms of Motion Perception

An enduring problem for sensory neurophysiology is to understand how neural circuits in the cerebral cortex mediate our perception of the visual world. In part, the problem endures because it is difficult; the circuits in visual cortex are formidable both in their number and in their complexity. Of equal importance, however, is that investigation of the visual system has yielded a stream of fascinating insights into the nature of cortical information processing. Perhaps foremost among these insights is that individual cortical neurons, in contrast to retinal photoreceptors, respond selectively to perceptually salient features of the visual scene. For example, neurons in striate cortex (or V1) respond selectively to the orientation of local contours, to the direction of motion of a visual stimulus, or to visual contours that fall on disparate locations in the two retinae (for review, see Hubel 1988).