Comparison of the critical periods for monocular and directional deprivation in cats.

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Abstract
Earlier experiments rearing kittens with 1 eye closed and reversing the closure after a certain age, or rearing kittens in a rotating drum and reversing the direction after a certain age, suggested that the critical periods for ocular dominance and directional sensitivity may differ. A direct comparison of the 2 types of visual deprivation was made. Four pairs of litter-mate kittens (matched in weight) were reared. One animal in each pair was monocularly deprived with subsequent eye reversal; the other animal was directionally deprived with reversal of drum direction. All reversals took place at age 5 wk. Both kittens in a given pair were either left first (left eye open first or left direction first) or both were right first. One died prematurely. Recordings were made from the visual cortex at some age after 4 mo. Some recordings were made in the left cortex and some in the right. In all cases of monocular deprivation, the majority of cells were driven by the eye that was open last (i.e., open after 5 wk of age). In all cases of directional deprivation, the majority of the cells preferred movement in the 1st direction of exposure (i.e., the direction before 5 wk of age). Apparently the critical period for directional deprivation terminates earlier than the critical period for monocular deprivation.