Topographical organization of ascending cerebellar projections from the dentate and interposed nuclei in Macaca mulatta: an anterograde degeneration study.

Discrete electrolytic lesions were placed in the dentate and interpositus cerebellar nuclei in th monkey Macaca mulatta and anterograde degeneration was traced in the ascending limb of the brachium conjunctivum using the Wiitanen technique. The dentate and interpositus anterior (IA) nuclei project topographically onto the two somatotopically organized divisions of the red nucleus and the ventrolateral-ventral intermediate nuclei of the thalamus (VL-Vim). Caudal parts of the dentate project to face areas in medial parts of the parvocellular red nucleus (RNpc) and VL-Vim, rostrolateral parts to central arm areas in these nuclei. There is a small projection from the rostroventral dentate to lateral hindlimb areas in RNpc and VL. Dorsal parts of the dentate project to ventral parts of RNpc and VLc-Vim (distal limb musculature area) exclusively, whereas ventral parts of the dentate project to dorsal parts of RNpc with some overlap ventrally dorsomedial VLc (proximal limb musculature and premotor areas). Caudal parts of IA project to medial forelimb and rostral parts to lateral hindlimb areas in the magnocellular red nucleus (RNmc) and VL-Vim. Projections from IA are greatest to distal musculature areas in VL-Vim. No projections from the interpositus posterior nucleus (IP) to the red nucleus could be identified positively, but projections to VL-Vim are to proximal hindlimb musculature and premotor areas.