G, The temporal lobe has been removed and the optic radiations preserved. The lower margin of the insula is located superficially at approximately the deep level of the lateral geniculate body. The fibers of the optic radiation pass through the stem of the temporal lobe on their way back to the calcarine sulcus. H, Inferomedial view of the basal frontal and medial temporal lobes. The white dots outline the fibers descending to form the cerebral peduncle. Black pins outline the deep position of the caudate and lentiform nuclei above the anterior perforated substance and basal surface of the frontal lobe. The yellow pins outline the anterior margin of the head of the hippocampus. The posterior part of the head of the hippocampus has been exposed by removing the medial part of the parahippocampal gyrus. I, Superior view of the upper surface of the temporal lobe that forms the floor of the sylvian fissure. The transverse temporal gyri, the most anterior of which is Heschl’s auditory projection area, form the posterior part of the upper surface of the temporal lobe, called the planum temporale. The anterior part of the upper surface, called the planum polare, is free of gyri and has a shallow trough to accommodate the course of the middle cerebral artery. The lateral edge of the planum polare is formed by the superior temporal gyrus. The stem of the temporal lobe, the relatively thin layer of white and gray matter that connects the temporal lobe to the lower insula, is positioned above the lateral and anterior edge of the temporal horn. J, Inferior view of the frontoparietal operculum. The gyri on the lateral surface extend around the lower border of the frontal and parietal lobes to form the upper lip of the sylvian fissure. The optic radiations pass laterally from the lateral geniculate body and course in the roof of the temporal horn along the temporal stem and lateral to the atrium to reach the calcarine sulcus on the medial aspect of the occipital lobe. (Images courtesy of AL Rhoton, Jr.)