The term inferior rhinal sulcus (irhs) refers to a shallow groove in the entorhinal cortex (ENT) of the anterior parhippocampal gyrus (PHGa) of the human. Defining the ventral border of the ambient gyrus, it is, In some individuals attributed to indentation of ENT by the tentorium ( Insausti-2012 ). it is not found in the macaque or the smooth cerebral cortex of the rat or mouse (NeuroNames ). Entered 18 Jul 2026.