cerebrospinal fibers cerebrospinal fibers the cerebrospinal fibers, derived from the cells of the motor area of the cerebral cortex, occupy the middle three-fifths of the base; they are continued partly to the nuclei of the motor cranial nerves, but mainly into the pyramids of the medulla oblongata. cerebrospinal fiberscoronal section through mid-brain. corpora quadrigemina.cerebral aqueduct.central gray stratum.interpeduncular space.sulcus lateralis.substantia nigra.red nucleus of tegmentum.oculomotor nerve, with 8’, its nucleus of originlemniscus (in blue) with a’ the medial lemniscus and a" the lateral lemniscusmedial longitudinal fasciculusraphétemporopontine fibersportion of medial lemniscus, which runs to the lentiform nucleus and insulacerebrospinal fibersfrontopontine fibersdetailsidentifierslatinfibrae cerebrospinalesanatomical terms of neuroanatomy