NCIt definition : The uppermost portion of the brainstem located between the pons and the diencephalon.
The midbrain contains the cerebral peduncles, oculomotor, trochlear and red nuclei,
substantia nigra and various other nuclei and tracts.;
Alternative definition : CDISC: The portion of the brainstem between the pons and diencephalon.; UBERON: The midbrain is the middle division of the three primary divisions of the
developing chordate brain or the corresponding part of the adult brain (in vertebrates,
includes a ventral part containing the cerebral peduncles and a dorsal tectum containing
the corpora quadrigemina and that surrounds the aqueduct of Sylvius connecting the
third and fourth ventricles)[GO].;