Interaction of critical periods in the visual cortex of kittens.
The critical period for modifying the preferred direction in cat cortical units occurs earlier than that for monocular deprivation. The independence of the effects of these two types of deprivation from each other was tested by rearing six kittens with both reverse suture and reversed directional deprivation. The kittens were placed in a drum rotating in one direction with one eye open at ages 2 1/2 to 5 weeks; the drum rotation was reversed and the other eye opened when they were 5 to 12 weeks old. Recordings were then made in the visual cortex. The results were the sum of the effects of reverse suture and reversal of directional deprivation: most cells were driven by the eye that was open second, and most unidirectional cells preferred the direction to which the animals were exposed first. Consequently, many unidirectional cells preferred the first direction but were driven by the eye open second--a combination that the animal never saw during rearing. There was also an effect of ocular deprivation on directional properties and vice versa: reverse suture reduced the overall percentage of unidirectional cells, just as directional deprivation has been shown to affect the ocular dominance histogram. This result suggests that the same cells may be affected by both forms of deprivation.