Is it necessary the hippocampus for spatial learning?

Objective. A variety or findings, mainly based on lesion studies, have led to the proposal that the hippocampus is a necessary component of the neural system supporting spatial learning. However, recent research is challenging this classic view. The goal of this review is to discuss and integrate these new data with previous findings. Development. Several studies performed in our lab have shown that hippocampal lesions do not affect the acquisition of a place response if a special training procedure is used. Nevertheless, the way how this special training method overcome the learning deficit is not well known. In this review we propose that hippocampal damage produces several non-spatial deficit, being one of them a deficit in behavioral flexibility. Thus, it is possible that our special training procedure encourage behavioral flexibility and variability in response in lesioned subjects, which would allow a significant improvement in the learning of the spatial task. Conclusion. The data discussed in this review suggest that the hippocampus is not completely necessary for the learning of a place. It would he the sum of spatial and non-spatial deficit ('hippocampal syndrome) which would produce the acquisition deficit typically seen in hippocampal rats when a traditional training method is used.