PLACE LEARNING BY FIMBRIA-FORNIX TRANSECTED RATS IN A MODIFIED WATER MAZE

The acquisition of a place learning task in a water maze modified from the ''standard'' setup by restriction of distal cues was tested in two groups of rats: (1) animals subjected to bilateral transection of the fimbria-fornx-a manipulation that renders the hippocampus dysfunctional-and (2) a sham operated control group. The fimbria-fornix transected animals acquired the task as quickly and to the same level of proficiency as the control group. Upon reaching criterion level performance all animals were tested on ''rotation'' sessions on which the distal cues were displaced. The outcome of such ''rotations'' demonstrated that both groups relied upon the distal cues for navigational purposes. Finally, the performance of all animals was ''challenged'' on two sessions by administration of d-amphetamine and scopolamine, respectively. The outcome of the pharmacological challenges demonstrated that the normal proficiency of place learning by the fimbria-fornix transected rats had been accomplished due to compensatory processes mediated at least partly by the catecholaminergic systems.