Cerebellar corticonuclear and corticovestibular fibers of the anterior lobe vermis in a prosimian primate ( Galago senegalensis )

Abstract Efferent projections of the anterior vermis were studied in a prosimian primate ( Galago senegalensis ). Cerebellar corticonuclear and corticovestibular fibers of the anterior lobe vermis are, in toto, ipsilateral. Two additional main points emerge. First, evidence is given which suggests that the cortical area defined as vermis converges, in a rostral direction (from lobules V to I + II), as the hemispheres of these lobules become latero‐medially foreshortened. The anterior vermis is a cortical region reflected by its efferent projections and not an arbitrary median strip of cortex which is either constant in width or morphologically separated from adjacent paravermal areas. Secondly, two patterns of organization emerge concerning cortical efferents, one suggestive of longitudinal zones and a second which shows that individual lobules project mainly to specific areas of the ipsilateral NM and into portions of the vestibular complex. Three zones are recognized. A very narrow midline area which appears to project bilaterally to the NM, a wider intermediate area (homologous to zone A) related to the ipsilateral NM, and a lateral area (homologous to zone B) related mainly to the ipsilateral vestibular complex, primarily its lateral nucleus. Within this overall zonal organization individual lobules project to specific areas of the NM and vestibular complex. Lobules V and IV project to rostrodorsal and rostrocentral NM respectively and into the dorsal LVN. Lobules III and II + I project to rostroventral‐medial and rostroventral‐lateral NM respectively, throughout the LVN and minimally into the SVN and SpVN. The specificity of corticonuclear terminations in the NM from the anterior vermis, heretofore not described for any primate, are similar, in terms of a general pattern, to that recently reported for the cat (Courville and Diakiw, '76).