Axial section of the brain at the level of the foramina of Monro. The anterior horns of the C-shaped lateral ventricles connect via the interventricular foramina of Monro to the midline third ventricle. From medial to lateral, starting at the third ventricle, are the thalamus, posterior limb of the internal capsule, lentiform nucleus (globus pallidus and putamen), external capsule, claustrum, extreme capsule, and insula. The head of the caudate nucleus forms the inferolateral wall of the anterior horn of the lateral ventricle, while the hippocampus forms the ventromedial floor of the interior horn. (Image courtesy of AL Rhoton, Jr.)