Roles of movement and temporal factors in spatial learning

Previous experiments suggested that rats can learn to discriminate between adjacent arms of an eight-arm radial maze if they have an intact hippocampal system and are allowed to move around on the maze. These requirements are consistent with the hypothesis that this discrimination involves hippocampus-based spatial learning. We examined the importance of self-generated movement in this form of learning by moving rats manually ("passive movement") between two adjacent maze arms within a single training trial. Rats moved passively between arms (only one of which contained food) within trials learned to discriminate between the arms, as measured by a conditioned preference for the food arm when both arms were empty. This form of learning was impaired by lesions of fimbria-fornix, but was unaffected by lesions of the lateral nucleus of the amygdala. Normal rats that were picked up and replaced on the same arm within trials and experienced their food and no food arms on different daily trials failed to learn the same discrimination. These findings suggest that self-generated movement is not required for spatial learning that may be mediated by a hippocampal system; rather, movement may simply serve to provide information from different locations about the cues in an environment.