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 colliculus (SC) is completely disrupted. In the experiments reported here, multi-unit auditory receptive fields were recorded in the SC of two groups of anaesthetised guinea pigs that had been exposed to different forms of visual deprivation. One group was reared in a movement-free environment (strobe-reared) and the other group was reared in a pattern-free environment (their eyes covered with light-diffusing masks). Both groups experienced visual restriction during the crucial period for auditory space map development. In both experimental groups, the multi-unit auditory receptive fields were broad and all spatial tuning parameter values were significantly greater than the equivalent values from a control group of normal animals. In the pattern- and motion-deprived groups, a significant correlation existed between the rostro-caudal position of the recording electrode in the SC and the peak response angle of the receptive field, thus showing a degree of topographic organisation of the auditory receptive fields in the SC. However, the topographic 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 auditory space map in the guinea pig.