Ventral part of the midbrain, separated from the hindbrain by the isthmus. The tegmentum lie anterior to the tectum and posterior to the substantia nigra and cerebral peduncles. It extends from the substantia nigra to the cerebral aqueduct, forming the floor of the midbrain that surrounds the cerebral aqueduct. Functionally, the tegmentum is important for alertness. More specifically, the iron-rich red nucleus helps coordinate movement and the periaqueductal grey helps suppress pain.