The effects of short-term occlusion therapy on reversal of the anatomical and physiological effects of monocular deprivation in the lateral geniculate nucleus and visual cortex of kittens

Summary The relative efficacy of distributed versus massed reverse occlusion therapy in promoting recovery from the anatomical and physiological effects of monocular deprivation was studied in two experiments performed on kittens raised with one eye occluded from eye-opening until 5 weeks of age. The first experiment explored the effects of different periods (ranging from 0.5 to 4 h) of reverse occlusion imposed daily for 20 days. The second, involving a fixed period of reverse occlusion (20 h), examined recovery with respect to the distribution of that period over a varied number of brief daily sessions. Recovery was assessed in terms of changes in cortical ocular dominance and lateral geniculate cell morphology. Although recovery of both cortical ocular dominance and geniculate cell morphology showed the same overall progression with increasing periods of reverse occlusion, changes were apparent in the lateral geniculate nucleus before changes were evident in cortical ocular dominance. A given period of reverse occlusion was found to be far more effective in promoting recovery when distributed over a number of different exposure sessions than when massed together in just one or two sessions. The data suggest that there is a maximal rate of cortical recovery which is achieved with surprisingly brief daily periods of forced visual exposure of the initially deprived eye.Supported by a grant (78/3589) to D.E.M. and S.G.C. from the National Health and Medical Research Council of Australia