Primary trigeminal afferents to the vestibular nuclei in the rat: existence of a collateral projection to the vestibulo-cerebellum.

Projections from the mesencephalic trigeminal nucleus to the vestibular nuclei were analyzed using retrograde and anterograde tracing methods. The results show that neurons in the caudal part of the trigeminal mesencephalic nucleus project mainly to the medial, inferior and lateral vestibular nuclei and moderately to the peripheral part of the superior vestibular nucleus. Using the double-labeling technique we demonstrate that individual neurons of the mesencephalic nucleus send collaterals to the vestibular nuclei and the vestibulo-cerebellum. These results suggest that these anatomical connections are involved in mechanisms of eye-head coordination.