G, Another hemisphere. The choroid plexus has been removed to expose the choroidal fissure located between the thalamus and fornix. The lateral part of the body of the fornix has been removed to expose the internal cerebral veins in the roof of the third ventricle. The nuclear mass, formed by the caudate and lentiform nuclei, extends above the middle cerebral artery and the roof of the stem of the sylvian fissure, formed by the anterior perforated substance and posterior part of the orbital surface of the frontal lobe. The amygdala is positioned behind and below the middle cerebral artery. H, The incision has been extended forward from the inferior choroidal point through the amygdala. The amygdala occupies the anterior segment of the uncus and is crossed on its upper anterior surface by the middle cerebral artery. The head of the hippocampus blends into the posterior uncal segment. The middle cerebral artery courses above the anterior uncal segment and the posterior cerebral artery and basal vein course medial to the posterior segment. I, Much of the thalamus has been removed to expose the body, crus, and fimbria of the fornix forming the outer margin of the choroidal fissure. The axial section extends through the area below the anterior limb of the internal capsule and anterior commissure where the caudate and lentiform nuclei and the nucleus accumbens and basalis blend together to form a massive collection of gray matter above the posterior part of the orbital surface of the frontal lobe and anterior perforated substance. J, Axial sections through the temporal lobe and the anterior and posterior segments of the uncus. The amygdala fills the anterior segment and the head of the hippocampus fills the upper part of the posterior segment. The fimbria arises on the surface of the hippocampus. The parahippocampal gyrus extends medially below the hippocampus. The collateral eminence overlies the deep end of the collateral sulcus that runs along the basal surface on the lateral side of the parahippocampal gyrus. The hippocampus meets the calcar avis in the anterior part of the atrium. K, Anterosuperior view. The axial section of the left hemisphere extends through the sylvian fissure, lateral geniculate body, amygdala, and the thin layer of white matter in the temporal stem below the lower edge of the circular sulcus. L, The cross sections extend along the optic tract and through the lower margin of the thalamus. The optic tract passes lateral to the lower margin of the thalamus to reach the lateral geniculate body. M, The optic tract and the thin layer of gray and white matter at the lower margin of the insula and circular sulcus that forms the stem of the temporal lobe have been removed to expose the temporal horn and the cisterns between the midbrain and parahippocampal gyrus. The anterior segment of the uncus faces the carotid and middle cerebral arteries. The apex faces the oculomotor nerve. The posterior segment faces the cerebral peduncle, crural cistern, posterior cerebral artery, and basal vein. (Images courtesy of AL Rhoton, Jr.)