“The midbrain is divided into a top part, called the tectum, which means ‘roof,’ and a bottom part, called the tegmentum, which means ‘floor covering.’ The two structures of the tectum are the superior and inferior colliculi (colliculus means ‘little hill’). As you can probably guess, these structures look like little hills on top of the midbrain. The superior colliculus controls certain visual reflex functions, such as the visual following of an object moving across your visual field. The inferior colliculus is a major relay station in the auditory system, sending information from the hindbrain to the forebrain.

“In the tegmentum, we see the continuation of the ascending sensory pathways and the descending motor pathways we told you about in the hindbrain. Also, the reticular formation passes through the midbrain, where it's called, appropriately enough, the midbrain reticular formation.”

“The substantia nigra is another important structure in the midbrain's tegmentum. Damage to the substantia nigra is associated with Parkinson's disease, which we mentioned when we discussed the functions of the neurotransmitter dopamine. Cells in the substantia nigra manufacture dopamine, and damage to the structure produces such motor symptoms as tremor of the hands, particularly at rest, and slowed movements.”