Diencephalon is the part of forebrain. During the third week of development of embryo, a neural tube is formed from the ectoderm. The neural tube forms three main vesicles namely, the prosencephalon, the mesencephalon and the rhombencephalon. The prosencephlon later divides into the telencephalon and the diencephalon. The diencephalon is present between the telencephalon and the midbrain. Sensory and motor impulses transmit from spinal cord and medulla oblongata to cerebrum via thalamus. Hypothalamus controls eye movement and hearing responses.