This program involves electrophysiological and behavioral studies of vision in species which have either highly cone-dominated or highly rod-dominated visual systems. These visual systems offer a number of special advantages in studying visual mechanisms, and the relationships between visual physiology and visual behavior. The specific research projects proposed include the following: (1) a determination of single cell responses in the ground squirrel to spatially and temporally defined luminance patterns and an inquiry into how such responses relate to discrimination behavior; (2) studies of the electrophysiology of the spectral mechanisms found in the ground squirrel visual system; (3) an examination of the receptive field organization of the lateral geniculate nucleus and visual cortex of the ground squirrel; (4) a study of spectral mechanisms and color vision in laboratory rats; (5) an investigation into the unusual properties which appear to be characteristic of the small number of rod photoreceptors found in the ground squirrel retina and (6) an investigation of the effects of spectrally restricted environments on the development and subsequent adult organization of the visual system.