Medial view of the hippocampal region. The parahippocampal gyrus has been partially removed to reveal the hippocampus in the floor of the lateral ventricle within the temporal lobe. The fornix is composed of efferent fibers that arise from the hippocampus. The fornix begins as a bundle of fibers called fimbria. Posteriorly the fimbria forms the crus of the fornix. The dentate gyrus of the hippocampus lies along the outer curvature of the fimbria of the fornix. The amygdala lies anterior to the hippocampus within the temporal lobe. The uncus is the anteromedial part of the parahippocampal gyrus located on the medial aspect of the temporal lobe and is divided into anterior and posterior segments. The choroidal fissure is located immediately above the hippocampus and forms the medial wall of the lateral ventricle.  The collateral sulcus separates the parahippocampal gyrus from the fusiform gyrus, also called the medial occipitotemporal gyrus. (Image courtesy of AL Rhoton, Jr.)