Avoidance learning in rats devoid of the telencephalon plus thalamus.

Two experiments were undertaken to investigate whether learning of an inhibitory avoidance response is possible in rats devoid of the whole forebrain, except for the hypothalamus. In experiment I all telencephalic structures were surgically ablated. Twenty-four hours later the rats were given a learning trial in the up-hill avoidance task. When tested 2 h later, the animals given a tail-shock contingent on the up-hill response showed significant increases in step-up latencies in comparison with control groups that had received non-contingent shock or no shock. In experiment II the thalamus was removed in addition to the telencephalon. As in experiment I, the animals received either tail-shock contingent on the up-hill reaction, no tail-shock, or non-contingent shock. When tested 2 and 24 h after the training, the animals that had received response-contingent shock showed significant increases in latencies to ascend the platform. These results indicate that inhibitory avoidance conditioning is still possible in rats devoid of the telencephalon plus thalamus.