A large number of investigations have shown that postnatal visual experience plays a crucial role in determining the functional organization of the mature visual system. Physiological, behavioral, and anatomical effects have been described as a result of visual deprivation or limited visual exposure early in life. These studies are directly applicable to the clinical diagnosis and treatment of visual disorders. The goal of the proposed project is to investigate mechanisms underlying normal and abnormal visual development in cats and humans. Neurophysiological, behavioral, and optical studies of the cat are planned along with human psychophysical experiments. Topics for investigation include amblyopia, strabismus, anisometropia, monocular and binocular deprivation, and quantitative studies of response properties of cells in immature, mature, and deprived visual cortex.