Vestibular afferents of the inferior olive and the vestibulo-olivo-cerebellar climbing fiber pathway to the flocculus in the cat

Abstract

The projection of the vestibular nuclei to the inferior olive was investigated by means of anterograde transport of tritiated leucine. Following injections in the medial and descending vestibular nuclei, terminal labeling was found ipsilaterally in the dorsomedial cell column, subnucleus β and the caudal medial accessory olive, while the latter also received afferents from the nucleus prepositus hypoglossi. At the contralateral side termination in the dorsomedial cell column and the medial accessory olive was found after injections in the nucleus vestibularis superior and group Y. The ventrolateral outgrowth and different parts of the principal olive also received afferents from these two nuclei and also from ventral parts of the lateral cerebellar nucleus. The dorsal cap was labeled exclusively from the contralateral nucleus prepositus hypoglossi. The termination in the inferior olive of the vestibular afferents is compared with the projection from a number of pretectal nuclei. Furthermore the consequences of the divergence and convergence of both types of projections at the level of the inferior olive is discussed in relation to the subsequent climbing fiber projection to the flocculus.