Both behavioral and neuroanatomical changes which occur after brain damage in the visual system are being analyzed with special attention to relationships between structural and functional changes. A multidisciplinary approach is employed, with techniques of experimental neuroanatomy and neurophysiology and behavioral testing. The finding of correlated anatomical and behavioral abnormalities in hamsters with lesions suffered in the early postnatal period has led to special interest in development and brain plasticity. Major current goals are threefold: (1) to describe the early development of the optic tract and of the projections of the visual cortex to the superior colliculus and other structures, at the level of fiber populations and at the level of single nerve fibers, in normal hamsters and in hamsters with neonatal brain lesions; (2) to obtain new evidence on the rules affecting the growth of abnormal trajectories and terminations of visual-system axons after neonatal lesions; (3) to describe effects of selective lesions in adulthood on visually guided behavior of hamster, including animals with abnormal neuronal connections, using new tests of visuomotor function.