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 temperature­ controlled 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 con­ vincing 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 re­ cently, 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 af­ ter 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 unavailabil­ ity, 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-day­ old rats if the rats' memories were reactivated during the retention interval. Retroactive interference often has been suggested as the prime determinant of memory inaccessibility (e.g., Miller & Berk, 1979). Since previsual rats are typically returned to the home cage during the retention interval, home cage environmental stimuli may be the primary source of