CONCUSSION-INDUCED RETROGRADE-AMNESIA IN RATS

Three experiments were conducted to investigate the characteristics of retrograde amnesia (RA) induced by concussion in rats. In Experiment 1, rats receiving experimental concussion shortly after training in a single punishment trial exhibited severe forgetting on a retention tes t 48 h later. In the second experiment, rats receiving a concussion wi thin 6 h after training showed severe RA, while those receiving concus sion one day to five days after training exhibited progressively weake r amnesia. In Experiment 3, amnesic animals in one group received pret est noncontingent foot shock as a reminder treatment. This pretest cue significantly increased the cross-through latency, thus indicating a reduction in the memory deficit resulting from concussion. These resul ts suggest that experimental concussion can be an effective method to induce retrograde memory loss in rats; that the RA caused by concussio n is time-dependent; and that concussion-induced RA can be alleviated by a pretest cue,indicating that the underlying mechanism of concussio n-induced RA is more likely to be a retrieval deficit than a consolida tion failure.