Effects of auditory cortical lesions on sound localization by the rat.

1. Studies with cats, dogs, and monkeys have shown that bilateral ablation of auditory cortex can result in severe deficits in the ability to localize sounds in space. In the present series of studies we sought to extend this observation to include the laboratory rat. 2. Rats were tested in a two-choice sound-localization task, which required a spatial response to a distant goal box. Although the test conditions were very similar to those employed with cat, dog, and monkey, deficits following cortical ablation were minimal. Indeed, following bilateral ablation of both primary and secondary auditory projection areas, rats were still capable of localization at small angles. 3. Several possibilities were considered to explain the apparent species difference in the effect of cortical ablations. It seemed unlikely that the difference was due simply to testing procedures or details of stimulus presentation. Central nervous system factors were discussed, including the possibility that the degree of impairment was related to the extent of cortical development in different species. It was concluded that the effects of auditory cortical ablation are not the same for all mammals and that for some species auditory cortex is not essential for sound localization.