The midbrain or mesencephalon is the uppermost portion of the brainstem connecting the diencephalon and cerebrum with the pons. [2] It consists of the cerebral peduncles, tegmentum, and tectum.. It is functionally associated with vision, hearing, motor control, sleep and wakefulness, arousal (), and temperature regulation.[3]The name mesencephalon comes from the Greek mesos, "middle", and ...