Working memory and the aged rat: deficient two-choice win-stay water-escape acquisition and retention.

Twelve aged (22 months), 12 adult (12 months) and 12 young (3 months) male Fisher 344 rats were compared on acquisition of a two-choice win-stay (spatial delayed matching-to-sample) water-escape working memory task. The 7 aged, 10 adult and 10 young animals that attained criterion were then compared on performance of the task when the retention interval (RI) was 5, 15, 30, 60 and 120 min. They were also compared on retention after being forced to perform an unsolvable water-escape task in a second maze during the first 5 minutes of a 30-minute RI. The aged animals had longer escape latencies, and required more trials and made more errors in attaining a criterion of 9 correct choices over 10 test trials than did the adult and young animals, who did not differ from one another. Also, comparisons of the animals that attained the acquisition criterion revealed that the aged animals had longer escape latencies and made more errors across all RIs and during trials including an interpolated distraction task than did the adult and young animals. The aged animals failed to perform above chance level on tests at any of the RIs or following the distraction task, while the young animals performed above chance level on tests at all intervals and following distraction. The adult animals failed to perform above chance on tests with the 120-minute RI or following distraction. The aged rats were clearly deficient on acquisition and retention of a two-choice water-escape working memory task.