Effect of prior visual experience on cortical recovery from the effects of unilateral eyelid suture in kittens.

The reversibility of monocular deprivation was tested physiologically in twelve kittens which had received varying amounts of normal visual experience prior to unilateral eye closure. Recordings obtained from cells in cortical area 17 indicated that the effects of monocular deprivation are reversible in cats as old as 8 weeks if the animals have been allowed normal visual experience before eye closure.1. Four kittens had their right eyes closed at 3, 4, and 5 weeks of age. All animals were reverse sutured at about 8 weeks of age, and after 2 weeks forced usage of the deprived eye, each animal was tested physiologically for recovery. Single unit recordings revealed a consistent relation between the extent to which the effects of initial deprivation could reverse and the age of the animal at the time of this deprivation. Recordings from a fifth, 8 week old kitten, which had been monocularly deprived for 3 weeks, ensured that our shortest period of deprivation induces a severe deficit.2. Two kittens which were reared in the dark for 4 and 5 weeks before unilateral eye closure, failed to show substantial (greater than 20%) reversal when reverse lid-sutured at 8 weeks of age. This failure suggests that kittens having their eyes closed after normal experience show enhanced reversibility, at least in part, on account of their early experience and not necessarily because of shorter deprivation. A litter-mate of one of these kittens was allowed 9 days of normal vision after dark rearing and before lid suture. Recordings which were performed both before and after 6 days of reverse suture demonstrated a near total (85%) reversal in ocular dominance.3. Three animals, monocularly deprived after some normal experience, recovered substantial numbers of binocular cells after both eyes had been allowed to remain open. In one of these cats the effectiveness of monocular deprivation was confirmed physiologically before eye opening. These findings contrast with those of other workers who have failed to find many binocular cells in kittens that had been allowed to recover, with eye opening, from monocular deprivation which had lasted since birth.4. One kitten was reared for 2 weeks (3-5 weeks of age) with alternating monocular deprivation. Single unit recordings from this cat, which were made after four additional weeks of unilateral eye closure, revealed some cells which had resisted monocular deprivation and which responded strongly to stimulation of the deprived eye. Reverse suture in the same animal led to the recovery of many cells (36%), dominated by the initially deprived eye, but did not result in a reversal in ocular dominance.