Recovery of vision with the deprived eye after the loss of the non-deprived eye in cats.

Closing one eye from birth to adulthood in kittens leads to well documented deficits in the visual system and has therefore frequently been used as an animal model for occlusion amblyopia. This study deals with the question whether vision through the deprived eye can be improved by appropriate postdeprivation manipulations and training. The performance of longterm monocularly deprived cats in a pattern discrimination task (bars of light had to be extracted from static two-dimensional visual noise) was measured quantitatively. The threshold in this test was three times higher than normal for the deprived eye when the non-deprived eye was closed by lid-suture, but only twice as high when the non-deprived eye was enucleated. This difference was statistically significant at the p less than 0.01 level in a t-test. The possible explanation for these behavioural findings is discussed on the basis of neurophysiological data from single cells in the visual cortex of the same animals obtained using a testing procedure similar to the behavioural tests. The better performance with the deprived eye after the non-deprived eye was lost may be related to an increase in the number of cortical cells driven from the deprived eye or to a reduction of "internal noise" after degeneration of the dominant pathway.