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 tuberomammillary (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.