STRESS-INDUCED MEMORY ENHANCEMENT FOR INHIBITORY FEAR CONDITIONING INRATS

The retroactive effects of stress on memory have not received a great deal of empirical attention; however, the research that has been condu cted has reported both positive and negative effects of stress on memo rial processes. The goal of this study was to examine the effects of a naturalistic stressor-an intense bout of exercise-on memory for inhib itory fear conditioning in rats. Experiment 1 investigated the retroac tive effect of a stressful swim treatment on memory for passive avoida nce (PA) training. Rats that received an immediate posttraining swim t reatment demonstrated a significant enhancement in performance when te sted for retention 24 h later. Furthermore, the enhancing effect of th e swim treatment was time dependent: Rats receiving the swim treatment 15 min after PA training no longer exhibited reliably better scores t han did rats not receiving the swim treatment. Experiment 2 used preex posures to control for the possibility that the swim treatment was enh ancing avoidance scores by acting as a punisher rather than a memory m odulator. Results indicate that both the group that was preexposed and the group that was not preexposed showed reliably higher scores than did a group of animals receiving only PA training, thus replicating Ex periment 1. Furthermore, the results of Experiment 2 suggest that swim ming was not simply acting as a punishing agent, since preexposures to the treatment did not attenuate its memory-enhancing properties. The possible role of stress-related hormones on memory processes is consid ered.