Medial occipitotemporal gyrus

Medial occipitotemporal gyrus is a cerebral gyrus situated on the inferior surface of the cerebral hemisphere, between the occipital pole and the temporal pole. Medially, it is separated from the parahippocampal gyrus by the collateral sulcus; anteriorly, the collateral sulcus continues as the rhinal sulcus, which separates the medial occipitotemporal gyrus from the anterior part of the parahippocampal gyrus and the uncus. Laterally, the medial occipitotemporal gyrus is separated from the lateral occipitotemporal gyrus by the occipitotemporal sulcus.

It is important not to confuse the medial occipitotemporal gyrus with the fusiform gyrus. The fusiform gyrus is an established synonym for the lateral occipitotemporal gyrus, not the medial one; it is bounded medially by the collateral sulcus and laterally by the occipitotemporal sulcus, and lies lateral to the medial occipitotemporal gyrus.

A separate source of confusion in the literature involves the mid-fusiform sulcus (MFS), a shallow sulcus first described by Retzius (1896). The MFS is not the same structure as the occipitotemporal sulcus; rather, it runs within the fusiform gyrus (lateral occipitotemporal gyrus) itself, dividing it into medial and lateral fusiform partitions (sometimes labeled FG1 and FG2), which have distinct cytoarchitectonic and functional properties, including a role in delineating the anterior portion of the fusiform face area.

Note on nomenclature variation: Some sources (e.g., Duvernoy's The Human Brain) use "medial occipitotemporal gyrus" as a collective term for the parahippocampal gyrus plus the lingual gyrus, treating it as lying medial to the collateral sulcus, with the fusiform (lateral occipitotemporal) gyrus lying lateral to that sulcus. This differs from the convention used here (consistent with TA2 and most current reference sources ) in which the medial occipitotemporal gyrus is a distinct gyrus separated from the parahippocampal gyrus by the collateral sulcus, and separated from the lateral occipitotemporal (fusiform) gyrus by the occipitotemporal sulcus. Readers cross-referencing Duvernoy's atlas should be aware the collateral sulcus plays a different structural role in that scheme.