An animal model of age changes in short-term memory: the DRL schedule

Eight mature (6 month old) and seven aged (24 month old) male Sprague Dawley rats were trained for 20, 30-min sessions on a differential-reinforcement of-low-rate 6 sec schedule. Responses were recorded according to their interresponse times (0-2 sec, 2-4 sec, 4-6 sec, 6-8 sec, 8-10 sec, and greater than 10 sec). Results indicated that the aged rats initially had difficulty in inhibiting short IRT responses, but with extended training this performance deficit was overcome and both age groups exhibited characteristic and effective patterns of responding. These data suggest that aged rats suffer from a temporary response bias and not a deficit in STM.