The effect of the home cage environment on retention of an active avoidance response in previsual rats

Abstract

Ten-day-old rats trained on multidirectional active avoidance response in a shock well showed no evidence of retention of the response 30 min after training if they were returned to the home cage during the retention interval. In contrast, rat pups that were maintained in a temperaturecontrolled chamber showed some retention ofthe response. Potential differences in arousal level may account for the differential effects of the retention interval manipulations.There is ample evidence that rats younger than 2 weeks of age have difficulty retaining· an active avoidance response (AR) even at short time intervals. Spear and Smith (1978), for example, found no 24-h retention in 7-12-day-old rats whose memories were not reactivated during the retention interval. Similarly, Goldman and Tobach (1967), who were the first to examine retention of avoidance behavior in previsual rats, provide no convincing evidence of 24-h retention. Ten-and 13-day-old rats were given 3 successive days of training on an active AR, and the lO-day-olds made fewer ARs on their 3rd day of training than the 13-day-olds on their 1st day of training, suggesting that day-to-day improvements were maturational rather than memorial in nature. More recently, Misanin, Turns, and Hinderliter (in press) found that, although the retentive memory capacity of 10000y-old rats was sufficient to sustain memory beyond the training session, a retention deficit was evident as soon as 5 min after training. There was no evidence of retention 30 min after training. That the retention deficit in previsual rats is due to the inaccessibility, rather than the unavailability, of the memory for the AR is indicated in the work of Spear and Smith (1978). These investigators were able to get 24-h retention of an active AR in 9-and 12-dayold rats if the rats' memories were reactivated during the retention interval.

The effect of home cage stimuli on acquisition and retention of an active avoidance response in previsual rats

“…Because young organisms differ from adults in the duration of this vulnerable period, they also appear to differ in the extent of the vulnerability. A young animal's memory appears to be disrupted by such simple events as being returned to the home cage (Misanin et al, 1985b) or a change in an irrelevant contextual odor (Solheim et al, 1980), whereas an adult animal's memory does not (Solheim et al, 1980). Yet this vulnerability so apparent in young organisms, has not been given serious empirical or theoretical consideration in interpretations of infantile amnesia (Campbell & Spear, 1972;Spear & Campbell, 1979).…”

“…In contrast, for animals trained with shavings, there was no similar change in context. In a previous study (Misanin et al, 1985b), we found that when there was no change in context from training to the retention interval for animals that were trained without shavings-when animals trained without shavings were not returned to the nest-there was a significant amount of retention. Thus, it may be that a contextual change from training to the retention interval is a determinant of retention loss in preweanling rats.…”

“…If the pup had not escaped shock in 90 sec, its forepaws were placed on the platform and the shock was terminated. During the 30-sec intertrial interval, the rat was held in the experimenter's closed hand, a procedure that is effective in maintaining normal body temperature (Misanin et al, 1985b).…”