The ventral portion of the midbrain, composed of the red nuclei, the PAG, and the Substantia Nigra.
The part of the cerebral peduncles which lies between the aqueduct and the substantia nigra.
T. Midbrain: The part of the cerebral peduncle of the midbrain located between the basis pedunculi ventrally and the tectum dorsally. T. Pontine: Small dorsal part of the pons located above the basilar region that forms the floor of the fourth ventricle.