Topographic organization of the cerebellar nucleocortical projection in the albino rat: an autoradiographic orthograde study.

The topography of the cerebellar nucleocortical projection was investigated in the albino rat by experiments employing an autoradiographic orthograde tracing method. The present results indicate that neurons in the deep cerebellar nuclei project to the granule cell layer of cerebellar cortex as mossy fiber terminals in an orderly way. Thus, the medial cerebellar nucleus projects mainly to the bilateral vermis with ipsilateral dominance. The interpositus and lateral cerebellar nuclei project mainly to the intermediate and lateral zones of the anterior and posterior lobes of the cortex, respectively. The paraflocculus and flocculus receive the nucleocortical projection from the caudal and ventral parts of the interpositus nuclei and the dentate nucleus. A mediolateral topography within each subdivision of the cerebellar nuclear complex was observed; the medial and lateral parts of the subdivision project to the more medial and lateral portions of the primary cortical targets of the subdivision, respectively.