Retained elements of early avoidance training and relearning of forgotten operants

In a series of 7 experiments we investigated the possibility that juvenile rats show long-term retention for aspects of early avoidance training and that these retained elements serve to reinforce relearning of the forgotten operants. Rats trained in active or passive avoidance at 23-25 days of age demonstrated the typical juvenile forgetting effect relative to adults after a 28-day interval. However, both juveniles and adults demonstrated marked reductions in locomotor activity prior to retraining which were specific to the apparatus and not dependent on the opportunity to perform an operant during initial training. Juvenile animals given a reminder exposure plus footshock 27 days after training, then single daily nonshock trials (Days 28-30), showed decreasing crossover latencies across days if trained in active avoidance and increasing latencies if trained in passive avoidance. This reappearance of task-appropriate crossover latencies was evident in previously trained juveniles only. Finally, young animals' demonstrated change in crossover latency is associated with subsequent superior acquisition performance, and this change depends upon the presentation of the test trials for its appearance. We suggest that the amelioration of "infantile amnesia asociated with the present procedures is a learning process motivated by Pavlovian components of training which are retained well, by juveniles and adults alike, over intervals typical of ontogeny of memory research.