Responsivity of normal kitten striate cortex deteriorates after brief binocular deprivation.

Abstract

Dark rearing of cats produces severe disruption of normal behavioral and physiological visual functions. The changes observed could be caused by impairment of developmental processes or degeneration of normal pathways, or both. To investigate the possible role of atrophic changes that might occur during brief periods of light deprivation, kittens were reared normally until 4 wk postnatal. Single units in visual cortex were assessed quantitatively in 1 group after they spent a period of from 3-6 days in a darkroom. Another group, normal controls, was studied using the same technique. Optimal values were determined for velocity and orientation of a bar stimulus with interleaved procedures. Using these parameters, an extended series of sweeps was run to obtain peak response levels. Associated measures of variability and maintained discharge levels were determined. Around twice as many cells from the deprived, compared to normal, kittens were classified as visually unresponsive. Of the responsive cells, the mean peak frequency for optimal stimuli was about half as high for optimal from deprived, as compared to control animals and the difference was significant. Variability as estimated by the ratio of standard deviation/mean (SD/.hivin.x) was also significantly higher for the deprived but maintained discharge levels were similar. No differences were found in the pattern of velocity tuning but orientation tuning was significantly broader for cells from the deprived, compared with nondeprived cats. Several days of darkness imposed on a normal 4 wk old kitten can measurably diminish certain aspects of cortical responsivity.