Structural Evidence for Functional Domains in the Rat Hippocampus

The hippocampus has two major outputs: multisynaptic pathways to the cerebral cortex and a massive descending projection directly to the lateral septal part of the basal ganglia. Here it is shown that the descending output is organized in such a way that different hippocampal regions map in an orderly way onto hypothalamic systems mediating the expression of different classes of goal-oriented behavior. This mapping is characterized by a unidirectional hippocampo-lateral septal projection and then by bidirectional lateral septo-hypothalamic projections, all topographically organized. The connectional evidence predicts that information processing in different regions of the hippocampus selectively influences the expression of different classes of behavior.