Detailed organization of cerebello-olivary projections in the cat. An autoradiographic study.

Several small injections of tritiated leucine were placed in regions of the cerebellar nuclei and sites of distribution in the olive were revealed by autoradiography. Different survival periods from a few hours to several days were utilized and high or low specific activity tracers were evaluated. A general pattern of distribution whereby the dentate, anterior and posterior interposed respectively project to principal, dorsal accessory and medial accessory olives was confirmed. Several new details of distributions from regions of the interposed and dentate nuclei to parts of the olivary subdivisions were demonstrated. The pattern of representations is complex and distributed in three dimensions. It is very precise and approximates a point to point representation. However, these projections which appear relatively dense do not represent the only link between the cerebellar nuclei and olive. With survival periods of a few hours, additional lighter projections distributed according to a different pattern can be revealed. A small ipsilateral projection was observed and it is suggested that it is made of collaterals of the crossed fibers.