Cerebellar corticovestibular fibers of the posterior lobe in a prosimian primate, the lesser Bushbaby (Galago senegalensis)

Abstract

The organization of cerebellar corticovestibular fibers was studied in a prosimian primate (Galago senegalensis) using the Fink and Heimer (1967) method. The vestibular complex of Galago is larger than in other mammals and some higher primates. Vermis lobule IX contributes the largest number of fibers to the ipsilateral vestibular complex. Lobules VI and VIII give rise to lesser, but similar, numbers of fibers which also pass into the ipsilateral vestibular nuclei. Vermis lobule VII and the paravermal and lateral cortices contribute extremely sparse numbers of fibers to the dorsal area of the ipsilateral vestibular complex. All degenerated fibers enter the vestibular nuclei through a large diffusely organized juxtarestiform body. Fibers from vermis lobule VII and the paravermal and lateral cortices terminate in dorsal areas of the ipsilateral vestibular nuclei. Vermis lobule VI projects into dorsal and lateral regions of the ipsilateral SVN, LVN and SpVN. Vermis lobules VIII and IX project into the dorsal and into progressively more central and medial regions of the ipsilateral SVN, LVN and SpVN. This gives the clear impression of a rostro-caudal origin of fibers from the posterior lobe vermis which terminate in an overlapping lateral to medial sequence in the vestibular nuclei, lesions of vermis lobule IX also elicit degeneration in dorsal areas of the ipsilateral medullary reticular formation and in the ipsilateral parabrachial nuclei.