Left Cerebral Hemisphere With Dural and Arachnoidal Layers Removed. A, The left cerebral hemisphere, once the dural and arachnoidal layers have been removed. 1, Pars orbitalis; 2, pars triangularis; 3, pars opercularis; 4, precentral gyrus; 5, postcentral gyrus; 6, supramarginal gyrus; 7, superior temporal gyrus; 8, middle temporal gyrus; 9, central sulcus; arrows, cortical rami of the M4 segment of the middle cerebral artery. B, The right cerebral hemisphere, once the dural and arachnoidal layers have been removed as well as the blood vessels. 1, Pars orbitalis; 2, pars triangularis; 3, pars opercularis; 4, precentral gyrus; 5, postcentral gyrus; 6, supramarginal gyrus; 7, superior temporal gyrus; 8, middle temporal gyrus; 9, central sulcus; 10, anterior ascending ramus of the sylvian fissure; 11, horizontal segment of the sylvian fissure; 12, precentral sulcus intersecting the pars opercularis; 13, posterior ascending ramus of the sylvian fissure. C, Right hemisphere after removal of the frontoparietal operculum. 1, Central sulcus of Rolando, which correlates to central sulcus of the insula; 2, central sulcus of the insula; 3, superior limiting sulcus of the insula; 4, inferior limiting sulcus of the insula; 5, sylvian point, which correlates with the medial border of the Heschl transverse gyrus; 6, anterior transverse gyrus of Heschl and planum temporale; 7, supramarginal gyrus partially removed; arrows, insular rami of the M2 segment of the middle cerebral artery (MCA). D, Insular enlarged view. 1, Central sulcus of Rolando, which correlates to central sulcus of the insula; 2, central sulcus of the insula; 3, superior limiting sulcus of the insula; 4, inferior limiting sulcus of the insula; 5, sylvian point, which correlates with the medial border of the Heschl transverse gyrus; 6, anterior transverse gyrus of Heschl and planum temporale; 7, supramarginal gyrus partially removed; 8, middle temporal transverse gyrus; 9, apex of the insula; 10, anterior short gyri of the insula with vertical direction; 11, posterior long gyri of the insula with perpendicular direction to the former; arrows, Insular rami of the M2 segment of the MCA. (Images courtesy of E de Oliveira)