Reversal of the physiological effects of brief periods of monocular deprivation in the kitten.

1. Five normally reared kittens were monocularly deprived from day 32 to day 42 and then subjected to varying periods (from 6 to 14 days) of deprivation reversal using the technique of reverse suturing. Data obtained from single unit recordings in striate cortex of these kittens were compared to control data from seven normal kittens (aged 32 days to 22.5 weeks) and three normally reared kittens given monocular deprivation from day 32 to day 42. 2. Analysis of cortical ocular dominance patterns in these reverse-sutured kittens revealed a progressively greater shift of influence away from the originally experienced eye and toward the originally deprived eye as the duration of the period of deprivation reversal increased. Most cortical cells were monocularly driven in these animals, but at each stage of the reversal process some binocular neurones were found. 3. The distribution of interocular differences in preferred orientation for binocular cells from these kittens was not significantly different from that for normal kittens, indicating that the pattern of connexions established by the originally deprived eye during reinnervation of striate cortex was very similar to that present before deprivation. 4. Previous studies on reversal of the effects of longer periods of monocular deprivation have indicated that during reinnervation of cortex by fibres representing the originally deprived eye an entirely new and different pattern of connexions is formed. On the basis of these results, it is hypothesized that short-term monocular deprivation causes a reversible silencing of otherwise intact synapses, while terminals are physically disrupted when deprivation is prolonged. 5. This hypothesis is supported by the results of an additional set of experiments in which receptive fields, many of which were highly specific, could be demonstrated for about one-half of the cells studied after removal of the non-deprived eye in two normally reared kittens given 10 days of monocular deprivation beginning on day 32. Similar experiments in two kittens deprived from eye opening to day 42 revealed functional input to less than 20% of the cells studied and no evidence of response specificity.