Neuroanatomy of the oculomotor system. The reticular formation.

The afferent and efferent connections of specific subdivisions of the reticular formation involved in the control of gaze are reviewed. Three regions of the medial brainstem reticular formation: the paramedian pontine reticular formation (PPRF), the dorsomedial rostral medullary reticular formation and the rostral interstitial nucleus of the MLF (riMLF) have direct projections to the extraocular motor nuclei, and play a well-defined role in the generation of saccadic eye movements only. The interstitial nucleus of Cajal (iC) also has direct premotor control of vertical extraocular motoneurons and is probably involved in the maintenance of vertical eye position. Reticulospinal neurons, which modulate the activity of neck and postural musculature, originate from all these regions. The neuroanatomy of other cell groups associated with the reticular formation are also described: the central mesencephalic reticular formation (cMRF), the posterior commissure nuclear complex (nPC), nucleus reticularis tegmenti pontis (nrtp), nucleus intercalatus (nic), nucleus of Roller (Ro) and nucleus interfascicularis hypoglossi (ifh), nucleus supragenualis (sg) and finally the cell groups lying within the paramedian tracts (pmt) of the pons and medulla. These have diverse and generally less well understood roles in the control of gaze.