Cerebellar afferents from the lateral reticular nucleus in the rat

The projection from the lateral reticular nucleus to the cerebellum was examined using the retrograde fluorescent double labelling method in the rat. A quantitative analysis of the extent of axonal branching and of nucleotopic (topographic) organization in this projection was carried out. It was shown that lateral reticular nucleus neurons show axonal branching both within and between parasagittal zones of the cerebellar cortex, but that branching within zones is more common. Neurons projecting to different zones were found to be significantly spatially separated, but those projecting to different sites within the same zone were intermingled. Thus a limited degree of nucleotopic organization was found. The results are discussed in relation to the parasagittal zonation in the olivocerebellar projection.