A, The falx, except for the inferior sagittal sinus, has been removed. The majority of the medial surface of the frontal lobe is formed by the cingulate and superior frontal gyri that are separated by the cingulate sulcus. The ascending ramus of the cingulate sulcus passes behind the paracentral lobule, the site of the extension of the pre- and postcentral gyri onto the medial surface of the hemi-sphere. The medial surface behind the paracentral lobule is formed by the precuneus, cuneus, and lingula and the posterior part of the cingulate sulcus. The precuneus is located between the paracentral lobule and parieto-occipital sulcus. The cuneus is located between the parieto-occipital and the calcarine sulci. The lingual gyrus (lingula) is located below the calcarine sulcus.B, Medial surface of another hemisphere. The paraterminal and paraolfactory gyri are located below the rostrum of the corpus callosum. The precuneus is located between the ascending ramus of the cingulate sulcus, the parieto-occipital sulcus, and the subparietal sulcus, a posterior extension of the cingulate sulcus. The cuneus is located between the parieto-occipital and calcarine sulci, and the lingula is located below the calcarine sulcus. The parieto-occipital and calcarine sulci join to create a Y-shaped configuration. The parahippocampal gyrus forms the majority of the medial surface of the temporal lobe. C, Another hemisphere. The medial surface is formed by the paraterminal, paraolfactory, superior frontal, and cingulate gyri and the paracentral lobule, precuneus, cuneus, lingula, and parahippocampal gyrus. The cingulate sulcus narrows behind the splenium to form the isthmus of the cingulate sulcus that blends along the medial surface of the temporal lobe into the parahippocampal gyrus. D, The section extends through the medial part of the right hemisphere and thalamus. It crosses the medial part of the head of the caudate nucleus anteriorly and the pulvinar of the thalamus posteriorly. The genu of the corpus callosum wraps around the frontal horn. The body of the corpus callosum forms the roof of the body of the lateral ventricle and the splenium is located adjacent to the atrium. The caudate nucleus is exposed in the lateral wall of the frontal horn and the body of the ventricle. The cingulum, a bundle of association fibers, wraps around the outer border of the corpus callosum in the depths of the cingulate gyrus. E, The cingulum and gray matter of the cingulate gyrus have been removed to expose the fibers radiating laterally out of the corpus callosum. The cross section of the corpus callosum is the part nearest the reader and the fibers radiate away from the cut edge around the margins of the lateral ventricle. Fibers passing through the genu of the corpus callosum form the forceps minor and the anterior wall of the frontal horn and the large bundle passing posteriorly from the splenium forms the forceps major creating a prominence, the bulb of the corpus callosum, in the medial wall of the atrium. The crus of the fornix wraps around the pulvinar in the anterior wall of the atrium. F, The brainstem has been removed to expose the uncus, which has anterior and posterior segments. The anterior segment faces the internal carotid artery. The posterior segment, facing posteromedially, is divided into an upper and lower part by the uncal notch. Removing the brainstem also exposes the parahippocampal and dentate gyri. The crus of the fornix and splenium have been removed to expose the caudate tail extending around the pulvinar. (Images courtesy of AL Rhoton, Jr.)