The long range objective of the current project is to understand the contribution of the activity of neurons in visual cortex to the visual behavior of animals and men. Initial studies showed that, in the cat, while the neurons in striate cortex are not essential in the processing of many visual details, they are critical for the processing of certain classes of stimuli. Other behavioral studies of vision in the cat showed that some stimulus dimensions (e.g., movement) may not contribute as much to vision as their potency in activating cortical neurons has suggested. Experiments which will compare behavioral and electrophysiological estimates of contour orientation sensitivity in the cat are proposed as well as studies of the role of various visual cortical areas in vision.