MIDBRAIN. forms a transition (and fiber conduit) to the cerebrum also contains a number of important cell groups, including several cranial nerve nuclei.
The base of the midbrain contains the cruscerebri, a massive fiber bundle that includes corticospinal, corticobulbar, and corticopontine pathways
The external aspect of the basis of the midbrain is called the cerebral peduncle.
The fibers of the oculomotor (III) nerve exit between the cerebral peduncles in the interpeduncular fossa.
Two contiguous somatic efferent nuclear groups lie in the upper tegmentum
The inferior colliculi receive input from both ears, and they project to the medial geniculate nucleus of the thalamus by way of the inferiorbrachium.
The colliculi contribute to the formation of the crossed tectospinal tracts