Extent of recovery from neonatal damage to the cortical visual system in cats.

Cats that received either marginal or marginal plus extramarginal lesions as 3-day-old kittens were assessed on a series of tests of visually guided behavior. These cats were not conspicuously different from normal controls in avoiding obstacles or in activity level. Yet these same operated cats were severely impaired in performance on the visual cliff and in visual discrimination learning, even when the lesions were limited to the geniculocortical portion of the visual system. However, maximum losses in pattern and form discrimination learning were observed only in cats with severe retrograde degeneration in both the lateral geniculate nucleus and the complex of the pulvinar and nucleus lateralis posterior. Photically evoked potentials were recorded in the lateral regions of the neocortex more reliably from operated cats that had made fewer errors in discrimination learning than from more severely debilitated cases; this relation was present even among cases with nearly equivalent amounts of retrograde degeneration in the visual thalamus. These findings suggest that in the cat (a) recovery of vision is incomplete after neonatal lesions of the visual cortex and (b) a cortical system lateral to the geniculocortical projections may be involved in pattern vision.