Acquisition of visuomotor behavior after neonatal tectal lesions in the hamster: the role of visual experience.

After neonatal damage to the midbrain tectum, hamsters exhibit as adults substantially reorganized retinal projections to the thalamus and midbrain. These experiments investigated the pattern of acquisition of a range of visuomotor capacities in hamsters with neonatal tectal damage, and the role of visual experience in this acquisition, by examining the time course of visuomotor development and the effects of dark-rearing on visuomotor behavior. These hamsters acquired visual orientation and pursuit at the same age as normal hamsters, but orientation and pursuit were impaired and exhibited no improvement over time. Photophobia and edge and depth sensitivity were relatively unaffected. Dark-rearing disrupted all visuomotor behavior in the midbrain-damage animals but had no effect on normal animals. These results are consistent with a dominant role of neocortex in the residual visuomotor capacities of animals with neonatal ablations of the midbrain tectum.