Parallel behavioral and electrophysiological studies of the visual process of the cat will be made to assess effects of restrictions in the visual environment during early development. Animals will be reared under stroboscopic illumination, in appropriate control conditions, or under normal laboratory conditions. Preliminary microelectrode recordings from the visual cortex of strobe-reared cats have shown reduction in orientation and directional selectivity. These studies will be extended to examine the velocity tuning, spatial and temporal contrast sensitivity, binocularity and receptive field size in cortical neurons. Quantitative behavioral measurements will be made of low velocity movement thresholds, sensitivity to the direction of motion, difference thresholds for the orientation of gratings and temporal and spatial contrast sensitivity. Behavioral and electrophysiological studies will be parallel in several respects: rearing conditions of the cats will be identical in both, the same visual stimuli will be used in both, and often both behavioral and electrophysiological measures will be carried out in the same animal.