The term limiting sulcus refers to the boundary between the cortex of the insula and that of surrounding gyri of the frontal lobe, the parietal lobe and the temporal lobe. Equally well known as the 'circular sulcus', it is identified by dissection in higher primates. In the human it has three parts: the anterior limiting sulcus, which separates the anterior insula from the basal operculum of the orbital gyri; the superior limiting sulcus, which separates the dorsal part of the insula from the frontal operculum and the parietal operculum; and the inferior limiting sulcus, which separates the insula ventrally from the superior temporal gyrus ( Ture-1999 ). The limiting sulcus of the macaque is similar except that it has no anterior component ( Mufson-1997 ). Equivalent structures are not found in the smooth cerebral cortex of the rat and mouse ( NeuroNames ).