The Insular Region. A, Lateral view of the right insula. In this specimen, the short insular sulcus that separates the anterior and the middle short gyri traverses the insular apex and extends to the limen insulae. 1, anterior short gyrus; 2, middle short gyrus; 3, posterior short gyrus; 4, anterior long gyrus; 5, posterior long gyrus. The central sulcus of the insula is located between the posterior short gyrus and the anterior long gyrus of the insula. The dotted line indicates the inferior limiting sulcus of the insula. B, Basal view of the right insula to display the inferolateral facet. In this specimen, the short insular sulcus that runs between the anterior and middle short gyri also traverses the insular apex and extends to the limen insulae. 0, accessory gyrus; 1’, transverse gyrus of Eberstaller; 1, anterior short gyrus; 2, middle short gyrus; 3, posterior short gyrus; 2 + 3, fusion of the middle and posterior short gyri; 4, anterior long gyrus; 5, posterior long gyrus; IP, insular pole; RI, rhinal incisura; APS, anterior perforated substance; TS, temporal stem; OT, optic tract; AM, amygdala; CP, insertion of the choroid plexus at the inferior choroidal point. Double asterisk, short insular sulcus. The dotted line indicates the inferior limiting sulcus of the insula. Asterisk, medial nucleus of amygdala. The medial nucleus of the amygdala is located anterior and slightly superior to the inferior choroidal point, and it is in close proximity to the optic tract and the upper part of the crus cerebri. The posteromedial orbital lobule is composed of the medial portion of the posterior orbital gyrus and by the posterior portion of the medial orbital gyrus. C, Frontal view of the right insula. 0, accessory gyrus; 1’, transverse gyrus of Eberstaller; 1, anterior short gyrus; 2, middle short gyrus; Caudate N, head of the caudate nucleus. The dotted line indicates the anterior limiting sulcus of the insula. The insular edge and the superolateral and inferolateral facets of the insula are more evident at the anterior portion of the insula as shown in this figure. D, Laterobasal view of the cerebrum. The posterior orbital gyrus has been removed to display the overall view of the anterior surface and the inferolateral facet of the insula. 0, accessory gyrus; 1’, transverse gyrus of Eberstaller; 1, anterior short gyrus; 2, middle short gyrus and the insular apex; 3, posterior short gyrus; 4, insular pole; 5, anterior long gyrus; 6, posterior long gyrus; 7, horizontal ramus of the sylvian fissure; 8, pars triangularis. Asterisk, posteromedial orbital lobule. The anterior zone of the insula (anterior surface and the short gyri) forms a pyramidal structure with its apex pointing laterally and inferiorly. The insular pole and the limen insulae are located more medially and posteriorly in relation to pars triangularis. (Images courtesy of AL Rhoton, Jr.)