Hippocampo-Hypothalamic Connections: Origin in Subicular Cortex, Not Ammon's Horn

Abstract

An autoradiographic study of the subcortical projections of the rat hippocampal formation shows that the efferent fibers of the hippocampus proper (fields CA1-4 of Ammon's horn) do not project to the hypothalamus but are confined to the precommissural fornix, ending primarily in the septum. The fibers that are distributed by way of the fornix system to the hypothalamus (principally the arcuate-ventromedial region and the mammillary nuclei) and the anterior thalamus arise from the subicular region of the cerebral cortex (that is, the subiculum, presubiculum, and parasubiculum).