Organization of the olivocerebellar projection to the uvula in the rat.

The present study was undertaken in order to determine the subnuclear origin of olivary parasagittal zones in the uvula of the rat cerebellum. Microinjections of horseradish peroxidase were made in different sublobules of the uvula ( sublobules IXa, b, and c of Larsell , 1952) and in different mediolateral positions within these sublobules . The results suggest that different specific regions of the contralateral inferior olive project to each of the parasagittal zones found within the uvula. Injections in the region of the most medial parasagittal zone result in the retrograde labeling of cells in 'subnucleus c' and nucleus beta subdivisions of the medial accessory olive (MAO). Injections in the intermediate region of the uvula result in the labeling of cells in the dorsomedial cell column. Finally, injections in the lateral part of the uvula result in the labeling of cells in the ventral lamella of the principal olive ( vPO ) or the rostral part of the MAO or both. There is some suggestion that the more rostral sublobules receive their input from the rostral MAO while the more caudal sublobule receives its input primarily from the vPO . These results agree fairly well with similar analyses of this projection system in the cat by Brodal in 1976.