ABSTRACT
The hippocampal formation represents phylogenetically the oldest part of the cortex (archipallium) and includes the hippocampal gyrus (cornu ammonis), fornix, dentate gyrus, subicular complex (subiculum, presubiculum, parasubiculum), and the entorhinal cortex. The hippocampal gyrus (cornu ammonis) develops as an enfolding of the cerebral cortex into the inferior horn of the lateral ventricle (Figures 17.1, 17.2, and 17.3). It is one of the simplest and most primitive structures of the human brain that stretches from the foramen of Monro to the tip of the inferior horn of the lateral ventricle. It lies superior to the parahippocampal gyrus, expanding anteriorly to form the pes hippocampi, which is crossed by several shallow grooves. The parahippocampal gyrus lies medial to the collateral sulcus and continues with the subiculum, a juxtallocortex. The subiculum extends with the inferior surface of the dentate gyrus and further laterally with the cornu ammonis, thus forming a curve that points toward the middle of the dentate gyrus.
