The term rhinal sulcus refers to a groove in the cerebral cortex (CTX) of the human ( Carpenter-1983 ), macaque ( Martin-2000 ), rat ( Swanson-2004 ) and mouse ( Hof-2000 ). Defined topologically by dissection it is located in the human ( Economo-1927 ) and macaque ( Martin-2000 ) on the ventromedial surface of CTX where it separates the anterior parahippocampal gyrus (PHGa) of the limbic lobe (LLB) from the inferior temporal gyrus (ITG) of the temporal lobe (TLB). Some authors regard it to be an extension of the collateral sulcus in the human ( Mai-2004 ). One of only four grooves in the CTX of the rat ( Swanson-2004 ), it runs longitudinally almost the entire length of the ventrolateral surface. Rostrally it is more than a groove; it totally separates the olfactory system ventrally from the lateral orbital area dorsally. Progressing caudally, the dorsal and ventral structures join. It becomes a shallow groove separating the olfactory system from the medial orbital area dorsally. Further caudally it shortly disappears from the medial surface of the hemisphere but continues separating the olactory areas from the lateral orbital area and agranular insular area on the lateral surface of the hemisphere. runs as a groove within that area separating the entorhinal cortex ventrally from the ectorhinal area dorsally. More rostrally, the perirhinal cortex intervenes between those two areas, and the rhs runs within it. At about the anterior-posterior level of the hypothalamus, the ectorhinal area disappears and the sulcus separates the ENT and the perirhinal cortex ventrally from the agranular insula dorsally. Rostrally from there, it runs within the agranular insular area and most rostrally it separates the piriform cortex ventrally from the agranular insular area dorsally ( Swanson-2004 ). A similar but less prominent, interrupted sulcus is found in the mouse ( Hof-2000 ). Updated 18 Jul 2026.