The hippocampal formation is located in the medial ventral temporal lobe (eFig. 9.102). It consists of the hippocampus, dentate gyrus, and subiculum (eFig. 9.103A and B). The hippocampal formation plays a role in memory processes such as episodic memory, short-term memory, working memory, and consolidation of memories. Input to the hippocampal formation is primarily received by the entorhinal cortex from association cortices. Because of this, it is believed that the “storage” of memories is in the association and primary cortices, not in the medial temporal lobe. Neurons from the entorhinal cortex project to the hippocampal formation by two pathways: the perforant pathway and alvear pathway. The perforant courses directly through the hippocampal sulcus to reach the dentate gyrus (eFig. 9.104B). As the hippocampus resembles the appearance of a ram’s horn, early on it was named cornu ammonis (horn of Ammon). Based on its cytoarchitecture, it was subdivided into four regions termed the cornu ammonis 1 to 4 (eFig. 9.104A). From the dentate gyrus, axons project to CA3 of the hippocampus. Axons from the hippocampus leave via the fornix or as Shaffer collaterals to reach CA1. Axons from CA1 may enter the fornix or project to the subiculum. Finally, axons from the subiculum enter the fornix or go back to the entorhinal cortex.