Comparison of tactile discrimination ability of visually deprived and normal monkeys.

The tactile discrimination ability of visually deprived and normal monkeys was tested to study whether loss of vision would improve the utilization of the tactual sense. Three normally sighted monkeys and three monkeys that had been deprived of vision during the first year of their life were trained in two tactile discrimination tasks by using a reward system in which the animals received a raisin or half a peanut under a correctly chosen wooden block. Discrimination was based on the gradual roughness or size of various blocks. When the monkeys had learned the tasks to the criterion, discrimination thresholds were determined. All monkeys improved their performance in both tasks with time, but no statistically significant differences between the performance of the two groups of monkeys were obtained. These results suggest that although the representation of the tactual sense in the cortical association areas has been shown to increase as a result of visual deprivation during the early sensitive period of life, increased representation does not improve the tactual discrimination ability of simple tactual stimuli.