The Insular Region. E, Frontal view. A coronal cut has been made at the anterior portion of the insula at the level of the optic nerves. In the anterior portion of the insula, the superolateral and the inferolateral facets, as well as the insular edge, are more evident. In the right hemisphere, the coronal cut includes the extension of the anterior short gyrus in the inferolateral facet, the transverse gyrus of Eberstaller, and its junction with the posteromedial orbital lobule (blue arrow). In the left hemisphere, a coronal cut has been made more anteriorly and included the posterior orbital gyrus. At this level, the head of the caudate is located immediately above the gray matter overlying the olfactory sulcus and is separated from the latter by a thin layer of white matter. The lentiform nucleus is located above the posteromedial orbital lobule and above the transverse gyrus of Eberstaller and is separated from the latter by a layer of white matter interposed by the claustrum. 1, head of the caudate nucleus; 2, superior limiting sulcus; 3, foramen of Monro (left); 4, lentiform nucleus and olfactory sulcus; 5, rectus gyrus; 6, optic nerve and olfactory tract; 7, posterior orbital gyrus; 8, posteromedial orbital lobule. The arrowheads indicate superior insular cleft and superolateral facet of insula. The white arrow indicates transverse gyrus of Eberstaller. The blue arrow indicates junction between the transverse gyrus and the posteromedial orbital lobule. IE, insular edge. Asterisk, paraolfactory gyrus. The red arrowhead indicates claustrum. The head and body of the caudate nucleus are located more superiorly than the superior limiting sulcus of the insula. F, Laterobasal view of the right insula. 0, accessory gyrus; 1’, transverse gyrus of Eberstaller; 1, anterior short gyrus; 2, middle short gyrus; 3, posterior short gyrus; 2 + 3, junction between the middle and the posterior short gyri; 4, anterior long gyrus; 5, posterior long gyrus; IA, insular apex; IP, insular pole; CS, central sulcus of insula. The dotted line indicates the location of the inferior limiting sulcus of insula. G, Coronal MRI scan of the posterior portion of the insula. H, Coronal MRI scan of the middle portion of the insula. I, Schematic drawing of the anterolateral aspect of the right insula. 0, accessory gyrus; 1’, transverse gyrus of Eberstaller; 1, anterior short gyrus; 2, middle short gyrus; 3, posterior short gyrus; 4, anterior long gyrus; 5, posterior long gyrus; IA, insular apex. J, Schematic drawing depicting a posterosuperomedial view of the walls of the insula. (Images courtesy of AL Rhoton, Jr.)