Parahippocampal gyrus

The parahippocampal gyrus is the medial-most gyrus visible on the underside of the cerebral hemisphere. It plays an important role in memory encoding and retrieval. Towards the front, it folds inward to form a bulge known as the uncus. Towards the back, the parahippcampal gyrus becomes continuous with the lingual gyrus as it extends onto the medial surface of the occipital lobe. On the sides, the parahippcampal gyrus is separated from the fusiform or occipitotemporal gyrus by the collateral and rhinal sulci.

The parahippocampal gyrus is closely related to the subiculum in the superior direction. To better understand this, we must first consider the structures within the medial temporal lobe system, namely the parahippocampal gyrus and the hippocampal formation. The latter consists of the hippocampus, subiculum, and dentate gyrus. Secondly, it’s important to know that during the development of the embryo, the cortex of the medial temporal lobe folds over itself twice, forming an S-shape in a side-to-side plane. As a result, the subiculum (often seen as an extension of parahippocampal gyrus) comes lies above the parahippcampus. Moreover, the hippocampus sits above and lateral to the subiculum, with the dentate gyrus situated between the hippocampus and the subiculum.