M, The glomus of the choroid plexus has been reflected forward to expose the medial wall of the atrium. The lingula that forms the lower bank of the calcarine sulcus has been preserved. The calcar avis overlies the deep end of the calcarine sulcus. N, The falx has been removed to expose the medial part of the right hemisphere. The ascending ramus of the cingulate sulcus reaches the superior border of the hemisphere behind the paracentral lobule. O, The pre- and postcentral gyri have been removed while preserving the superior temporal gyrus. The choroidal fissure, the cleft between the thalamus and fornix, extends from the foramen of Monro through the body, atrium, and temporal horn to the inferior choroidal point located just behind the head of the hippocampus. P, Superolateral view of the cross section of the central area of the hemisphere, positioned between the insula laterally and the ventricles medially. The central core of the hemi-sphere, the area between the insula laterally and the ventricles in the midline, includes the caudate and lentiform nucleus, thalamus, and anterior and posterior limbs and genu of the internal capsule. The claustrum is positioned between the insular cortex and the lentiform nucleus. Q, The superior temporal gyrus has been removed while preserving the long gyri of the insula. The ascending ramus of the cingulate sulcus marks the posterior edge of the paracentral lobule, the extension of the pre- and postcentral gyri onto the medial surface of the hemisphere. R, Enlarged view of the choroidal fissure. The choroidal fissure extends from the foramen of Monro to the inferior choroidal point located behind the head of the hippocampus. The choroid plexus, which attaches along the choroidal fissure, has been removed. The outer edge of the choroidal fissure is formed by the body of the fornix in the body of the ventricle, the crus of the fornix in the atrium, and the fimbria of the fornix in the temporal horn. (Images courtesy of AL Rhoton, Jr.)