Anatomical organization of the spinocerebellar system, as studied by the HRP method.

Using the HRP method we have identified eleven groups of spinocerebellar tract (SCT) neurons in the cat, and determined their projection areas in the anterior and the posterior lobes. Neuronal groups projecting to lobule VIII are located in the central cervical nucleus (CCN), Clarke's column and the medial part of lamina VII of L6 to the caudal segments while those projecting to the paramedian lobule are lamina V neurons of C8 to L4, marginal neurons of Clarke's column and spinal border cells. In the anterior lobe the CCN projects to lobules I to V, most abundantly to lobules I and II. The medial lamina VII group of L6 to the caudal segments projects mainly to lobules I and II. Spinal border cells project to lobules II to V, but predominantly to lobules III and IV. Clarke column neurons project to lobules I to V. The medial lamina VI group and the central lamina VII group of the cervical segments project to lobules III and IV. Marginal neurons of Clarke's column and lamina V neurons of the lower cervical to the lumbar segments project to lobules III to V. The present study suggests that the SCT neurons project to different sagittal zones of the cerebellar cortex, with various quantities in the rostrocaudal direction.