Consist of gaze centers relayed to motor nuclei via Medial longitudinal fasciculus
Gaze centers:
Horizontal gaze center: controls gaze to ipsilateral side; located in paramedian pontine reticular formation (PPRF) at level of CN 6 nucleus; projects to ipsilateral CN 6 nucleus and (via medial longitudinal fasciculus [MLF]) to contralateral CN 3 nucleus;
Vertical gaze center: originates in frontal eye fields or in superior colliculus; requires bilateral cortical input; projections travel to rostral interstitial nucleus of the MLF (riMLF) located behind red nucleus in midbrain; fibers travel to nuclei of CN 3 and 4;
Medial longitudinal fasciculus: extends from anterior horn cells of the spinal cord to the thalamus; connects CN 3 nuclei and gaze centers (ipsilateral CN 3 and contralateral CN 6);
Three cranial nerves innervate the muscles of the eyes:
the oculomotor nerve (CN III) - nuclei in midbrain tegmentum;
the trochlear nerve (CN IV) - nuclei in midbrain tegmentum;
the abducens nerve (CN VI) - nuclei in pontine tegmentum underlying the floor of the fourth ventricle.