The effects of pretraining and reminder treatments on retrograde amnesia in rats: comparison of lesions to the fornix or perirhinal and entorhinal cortices.

The present experiment examined the effects of pretraining and reminder treatments on the retention of a nonrelational odor-guided digging task following lesions to the hippocampal formation (i.e., fornix) or parahippocampal region (i.e., perirhinal and entorhinal cortices). The results showed that fornix-lesioned rats and control rats had good retention of the task and did not differ from each other; however, perirhinal- and entorhinal-lesioned rats were severely impaired and differed from fornix and control rats. The present experiment found no attenuation of amnesia following pretraining, which may be due to the lesion technique employed and the size of the resulting lesions. However, the experiment found a significant difference in performance following a reminder treatment, even in the severely impaired perirhinal- and entorhinal-lesioned group.