The effects of brief periods of eye closure on the visual system of kittens were examined in animals monocularly deprived by eyelid suture for between 6 h and 8 days, starting on the 29th day of life. Before that time, the kittens had normal visual experience. At the end of the deprivation period, the kittens were permitted 2 days consolidation with both eyes closed before physiological recordings were undertaken in the visual cortex, area 17. After the brief recording sessions, the kittens were sacrificed and prepared for histology. Measurements were made of the distributions of cell areas in the layers of the lateral geniculate nuclei (LGNs) innervated by the two eyes. Perceptible shifts in cortical binocularity were seen following as little as 1 day of eye closure, and these effects were increasingly marked in kittens deprived for longer periods. A period of 4 or 8 days of deprivation was sufficient to cause cortical changes comparable to those seen following much longer periods of deprivation. Neuronal receptive fields activated through the deprived eye appeared to lose much or all of their stimulus selectivity before disappearing altogether. Many neurons in the kittens deprived for 1,2, or 4 days possessed normal orientation selective receptive fields in the eye that had been open and nonoriented or poorlyselective receptive fields in the eye that had been closed. The changes in cortical binocularity were accompanied by changes in the distribution of physiologically revealed ocular-dominance collumns. In kittens that showed marked deprivation effects, the neurons that were dominated by the deprived eye tended to be culustered together in small groups and flanked by larger areas strongly dominated by the experienced eye. Significant differences in cell size between layers of the lateral geniculate nuclei driven by the two eyes were apparent in all kittens deprived for longer than 12 h. These effects were larger in kittens deprived for longer periods: the areas of cells in layers driven from the deprived eye were smaller, on average, than those in layers driven from the experienced eye by about 10% after 1 or 2 days of deprivation, by about 20% after 4 days of deprivation, and by nearly 30% after 8 days of deprivation. The close correlation between the changes in cortical binocularity and the changes in geniculate cell size observed in these animals lends support to the hypothesis that these effects share a common origin, perhaps related to the competition for terminal space in the cortex reflected in physiological and morphological changes in the relative extent of the cortical regions dominated by the two eyes in deprived animals.
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