Role of visual experience in postcritical‐period reversal of effects of monocular deprivation in cat striate cortex

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Abstract
We reported previously that the effects of monocular deprivation on cat striate cortex cells can be partially reversed after the critical period by enucleation of the experienced eye (Kratz et al., '76). The enucleation resulted in a rapid (less than 12 hours) increase in the percent of cells which responded to the deprived eye; however, the receptive field properties of the responsive cells were abnormal. There was no change in this result if the animals were allowed to survive 3 to 16 months after the enucleation, during which the deprived eye remained closed. The present study investigated whether enucleation of the experienced eye extends the period of sensitivity during which connections from the deprived eye can be modified by visual experience. That is, we asked whether opening the deprived eye and allowing it normal visual experience after enucleation of the experienced eye would lead to a further increase in the percentage of responsive cells or produce a modification of receptive field properties.Using single‐cell recording in striate cortex, comparisons were made between monocularly deprived control kittens (MD), kittens which had the experienced eye enucleated at four months of age while the deprived eye remained closed (MD‐DE) or was opened (MD‐DE‐O) for an additional three to four months, and kittens which received reverse‐suture at the same age and for the same duration (MD‐RS). Kittens in both the MD‐DE and MD‐DE‐O groups showed an increase in the percent of cells responsive to the deprived eye compared to MD control kittens, replicating our previous findings. However, there were no differences between the MD‐DE and MD‐DE‐O groups either in terms of percent responsive cells or in the receptive field properties of those which responded. Reverse‐suture also produced a significant, although variable, increase in the percent of cells responding to the initially deprived eye. However, this increase was significantly less than that produced by enucleation of the experienced eye in MD‐DE and MD‐DE‐O animals. Among the cells responsive to the initially deprived eye in the reverse‐suture animals, the receptive field properties remained abnormal.These results suggest that binocular interactions continue to play an active role in the effects of monocular deprivation after the previously defined critical period. However, reversal procedures such as suture or enucleation of the experienced eye do not extend the period in development during which cells in striate cortex can be modified by visual experience. Rather, they may simply release those cells already receiving anatomical connections from the deprived eye from a tonic inhibition mediated by the experienced eye.