VISUAL MOVEMENT AND PATTERN ARE IMPORTANT FOR THE DEVELOPMENT OF A MAP OF AUDITORY SPACE IN THE GUINEA-PIG SUPERIOR COLLICULUS

Previous data have indicated that, if guinea pigs are deprived of all visual information during a crucial period early in development (26-30 days after birth), the map of auditory space in the superior collicul us (SC) is completely disrupted. In the experiments reported here, mul ti-unit auditory receptive fields were recorded in the SC of two group s of anaesthetised guinea pigs that had been exposed to different form s of visual deprivation. One group was reared in a movement-free envir onment (strobe-reared) and the other group was reared in a pattern-fre e environment (their eyes covered with light-diffusing masks). Both gr oups experienced visual restriction during the crucial period for audi tory space map development. In both experimental groups, the multi-uni t auditory receptive fields were broad and all spatial tuning paramete r values were significantly greater than the equivalent values from a control group of normal animals. In the pattern- and motion-deprived g roups, a significant correlation existed between the rostro-caudal pos ition of the recording electrode in the SC and the peak response angle of the receptive field, thus showing a degree of topographic organisa tion of the auditory receptive fields in the SC. However, the topograp hic order was less precise than that displayed by the control group of animals. These results indicate that, during development, both visual pattern and movement are important for the refinement of the SC audit ory space map in the guinea pig.