The diencephalon divides into the thalamus, the hypothalamus, and several related regions. The thalamus is involved with sensation. It is the relay station between the sense organs and their corresponding cortical regions. Olfaction (smell) is the only sense modality that does not run through the thalamus as it is processed directly by the olfactory bulb. The hypothalamus links the brain to the autonomic nervous system and serves a critical role in emotion, connecting the mental aspects of emotion with the body’s physical response.