FACILITATION OF LEARNING IN ADULT AND AGED RATS FOLLOWING BILATERAL LESIONS OF THE TUBEROMAMMILLARY NUCLEUS REGION

In the present experiment, adult (3-month-old) and aged (31-month-old) rats received bilateral DC or sham-lesions in the region of the tuber omammillary (TM) nucleus before they were trained and tested on a one- trial step-through inhibitory avoidance task. Bilateral lesions of the TM nucleus led to significantly longer latencies in the step-through response during retention test in both adult and aged rats, indicative of superior learning of the task. Thus, lesions of the TM nucleus may have a facilitatory effect on learning and mnemonic functioning which is possibly related to a lesion-induced disinhibition or facilitation of reinforcement processes (''stamping-in'') as revealed in previous studies.