Midbrain

The midbrain, or mesencephalon, is the uppermost and smallest region of the brainstem. It serves as a relay center for visual and auditory information, containing the superior and inferior colliculi. It plays a key role in motor control, reward, and arousal via structures like the substantia nigra (dopamine production) and the ventral tegmental area. It also contains nuclei for the oculomotor and trochlear cranial nerves.