Fig. 2. Summary of supranuclear control of eye movements. The central figure shows the supranuclearconnections from the frontal eye fields (FEF) and the parietal-occipital-temporal (POT) region to the superior colliculus (SC), rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF), and the paramedial pontine reticular formation (PPRF). The FEF and SC are involved in the production of saccades, while the POT is important in the production of pursuit eye movements. The left inset shows the brain-stem pathways for horizontal gaze. Axons from the cell bodies located in the PPRF travel to the ipsilateral abducens nucleus. In the nucleus, they establish a synapse with abducens neurons, whose axons travel to the ipsilateral lateral rectus (LR) muscle, and with abducens internuclear neurons, whose axons cross the midline and travel in the medial longitudinal fasciculus (MLF) to the subnucleus of the oculomotor nucleus (III) concerned with medial rectus (MR) function in the contralateral eye. Vestibular input for horizontal eye movements comes from the contralateral vestibular apparatus by way of the vestibular nuclei. An axon from the vestibular nucleus crosses to the opposite abducens nucleus, where it innervates a motor neuron and an internuclear neuron for horizontal gaze in the opposite direction. The right inset shows the brain-stem pathways for vertical gaze. The region of the riMLF appears to be most important for generating downgaze, whereas the posterior commissure region appears most important for generating upgaze. Vestibular input for vertical gaze arises in the contralateral vestibular nucleus, decussates, and ascends in the MLF to the oculomotor nucleus and the trochlear nucleus. (Miller NR: Walsh and Hoyt's Clinical Neuro-Ophthalmology. Vol 2, 4th ed. Baltimore:Williams & Wilkins, 1985:627.)