The nucleus reticularis tegmenti pontis and the adjacent rostral paramedian reticular formation: differential projections to the cerebellum and the caudal brain stem.

The projection of the nucleus reticularis tegmenti pontis and the adjacent tegmental area, to the caudal brain stem and the cerebellum were investigated by means of anterograde transport of tritiated leucine. The nucleus reticularis tegmenti pontis was found to be exclusively connected with the cerebellum. Mossy fiber terminals were absent only from lobule X and most abundant in lobule VII and the hemispheres with a slight contralateral predominance. The paramedian pontine reticular formation projects with bilateral symmetry to the cerebellar lobules VI, VII and the crura I and II, and heavily to the medial aspect of predominantly the ipsilateral reticular formation in the lower brain stem including specific targets as the nucleus reticularis paramedianus, the nucleus prepositus hypoglossi, the nucleus intercalatus, the nucleus of Roller, the nucleus supragenualis and the dorsal cap of the inferior olive. The nucleus vestibularis medialis receives a very weak projection. The connections are discussed in the light of their possible involvement in pathways for the execution of voluntary and reflex eye movements.