The basal cell mass of the paired posterior or caudal parts of the forebrain or prosencephalon that contain the thalamus (dorsal thalamus, epithalamus, sub-thalamus or ventral thalamus) and hypothalamus. The dorsal part consists of the epithalamus and dorsal thalamus, and the ventral part the sub-thalamus and hypothalamus. It connects the mesencephalon (midbrain) of the brain stem with the cerebral hemispheres, and covers and encloses the third ventricle. Its functions are associated with sensory integration in that it relays sensory information between the brain stem and other brain regions. It is also an area of the brain associated with the signs of Korsakoff’s syndrome, which is a memory disorder due to a deficiency of vitamin B1 or thiamine arising from alcoholism. Sometimes the diencephalon is classified as part of the brain stem, but in general is treated as being an area of the cerebrum, namely, the forebrain consisting of the diencephalon and the telencephalon. The other two major divisions of the brain are the hindbrain (medulla oblongata, metencephalon) and the mesencephalon.
See Brain (or encephalon), Brain stem, Epithalmus, Medulla oblongata, Mesencephalon, Metencephalon, Optic nerve, Prosencephalon, Rhobencephalon, Telencephalon, Thalamus, Ventricle