Recovery from the effects of monocular deprivation in kittens

TLDR: Behavioral and electrophysiological measurements suggest considerable recovery of function even in cases where kittens were merely given binocular vision during recovery, and conclude that the two eyes' effectiveness is not solely determined by competitive interaction.

Abstract: Significant recovery from the effects of early unilateral eye closure has been found following a period of reversed deprivation involving forced usage of the deprived eye. A simple period of binocular vision, however, has been reported to be ineffective. We have compared these two recovery conditions (reversed deprivation and binocular vision) in kittens initially deprived to the age of 45 or 60 days, and given seven to eight weeks of recovery. We estimated behavioral recovery by measuring visual acuity through the deprived eye. Kittens deprived to day 45 attained nearly normal grating resolution in their deprived eyes (5–6 cycles/degree), while those deprived to day 60 showed enduring partial acuity deficits (4–5 cycles/degree). Surprisingly, the deprived eye's acuity in kittens given binocular vision during recovery was nearly the same as that possessed by the deprived eyes of reverse-deprived kittens. We estimated physiological recovery from the visual response properties and eye dominance of 359 cortical neurons; all kittens showed shifts in eye dominance from the situation that obtains after a period of deprivation. Reverse-deprived kittens, in agreement with previous reports, showed more pronounced shifts of cortical eye dominance than did binocularly recovered kittens. Nevertheless, significant recovery of both the deprived eye's influence and of the selectivity of its receptive fields was seen in kittens given binocular vision. In no case was there significant recovery of cortical binocular interaction: most neurons were monocularly driven, and were aggregated into ocular dominance columns strongly dominated by one eye or the other. Since both behavioral and electrophysiological measurements suggest considerable recovery of function even in cases where kittens were merely given binocular vision during recovery, we conclude that the two eyes'effectiveness is not solely determined by competitive interaction – significant changes can occur when neither eye has a competitive advantage over the other.