[TA] the region of the cerebral hemisphere that stretches as a thin sheet of brain tissue between the fornix bundle and the ventral surface of the corpus callosum, forming the medial wall of the lateral ventricle's frontal horn; it extends ventrally through the narrow interval between the anterior commissure and the rostrum of corpus collosum as the precommissural septum or subcallosal gyrus, which is continuous caudally with the preoptic area and hypothalamus, as well as more laterally with the innominate substance; its major functional connections are with the hippocampus and hypothalamus. It is composed of a dorsal septal nucleus [TA], lateral septal nucleus [TA], medial septal nucleus [TA], septofimbrial nucleus [TA], and triangular nucleus of septum [TA]. The subformical organ [TA] is also found in this area.