The olivocerebellar projection in the cat as studied with the method of retrograde axonal transport of horseradish peroxidase. II. The projection to the uvula.

Following injections of small quantities of horseradish peroxidase (HRP) suspension in the uvula of the cat, the distribution of labeled cells in the inferior olive has been mapped. The findings confirm the conclusion made on the basis of studies of retrograde cell loss in the olive following ablations of the uvula (Brodal, '40b) that two small olivary subdivisions, the nucleus beta and the dorsomedial cell column project heavily to the uvula. In addition the HRP-study shows that the uvula receives a smaller number of fibers from two circumscribed areas of the contralateral medial accessory olive. These areas appear to project to the lateralmost parts of the uvula (fig. 4). The findings thus support the presence of a longitudinal zonal subdivision in the uvula. Labeled cells are found in the nucleus beta and the dorsomedial cell column also following injections of the fastigial nucleus and to a lesser degree of lobulus VII of the vermis (Hoddevik et al. 76). This may be due to collateral branching of olivary efferents. There is some evidence for a topographical correlation between dorsal and ventral parts of the uvula and rostral and caudal parts, respectively, of the nucleus beta and the dorsomedial cell column. This may be related to functional differences between the two parts of the uvula.