Effect of auditory neocortex ablation on identification of click rates in cats

Six experimental and 3 unoperated cats were trained with a go, no-go shock avoidance procedure to discriminate increases from decreases in the rate of presentation of all auditory cortex between the suprasylvian sulcus and rhinal fissure while 3 cats had bilateral auditory cortex lesions plus ablation of the cortex of the anterior lateral and anterior and middle suprasylvian gyri. A sixth 'naive' experimental cat received the present tests only after recovery from a bilateral auditory cortex ablation. After bilateral lesions, 5 of the experimental cats unexpectedly made no errors on no-go trials during retraining. This contrasts with their preoperative performance, as well as the performance of the 3 unoperated and the 'naive' operated cat, in which training was required for the successful discrimination of the two types of trials. This suggests that the neocortex may be more critical for mediating active 'go' responses to auditory stimuli than in preserving a memory for the difference between go and no-go stimuli. Further testing revealed that the thresholds of the operated cats did not differ from normal cats. All cats discriminated rates of 4/sec versus 6/sec clicks both with and without a neutral 5/sec background at levels significantly above chance.