One of two nuclei of the oculomotor nerve. The main oculomotor nucleus is located in the anterior part of the gray matter surrounding the cerebral aqueduct of the midbrain at the level of the superior colliculus. It consists of a cluster neurons that supply all extrinsic muscles of the eye, with the exception of the superior oblique and lateral rectus. It receives fibers from both cerebral hemispheres, the superior colliculus (and from here the visual cortex), and has connections with cranial nerves IV, VI and VIII via the medial longitudinal fasciculus. This nucleus controls the inferior, medial and superior rectus muscles, the inferior oblique muscle and the levator palpebrae superioris, the latter controlling movements of the eyelid. The accessory parasympathetic (or Erdinger-Westphal) nucleus is situated just behind the main oculomotor nucleus and controls the ciliary ganglion, which innervates the sphincter pupillae that contracts the pupil in response to changes in light intensity and the ciliary muscle that changes the shape of the lens to allow visual accommodation. Damage to the oculomotor nerve (e.g., as a consequence of a stroke) results in oculomotor nerve palsy and associated strabismus that in turn leads to problems with binocular vision.
See Binocular vision, Cranial nerves, Deep cerebellar nuclei, Gray matter, Parasympathetic nervous system (PNS), Puplllometry, Superior colliculus, Visual accommodation, Visual cortex