Both dorsal and ventral hippocampus contribute to spatial learning in Long-Evans rats

The hippocampus (HPC) may be functionally heterogeneous in supporting spatial learning in rats. Thus, dorsal but not ventral HPC lesions have been reported to impair acquisition in the Morris water task which consists of finding a submerged platform in a pool filled with opaque water. To further investigate the functional differences between dorsal and ventral HPC regions, we used a one-trial matching to position water task in which the submerged platform occupied a different position during each session. This task is very sensitive to HPC damage. The results show that either dorsal or ventral HPC NMDA lesions disrupt the rapid acquisition of new place information. The acquisition deficit diminishes with training in both lesion groups. The data thus suggest that the entire HPC axis is involved in acquisition of spatial information.