An HRP study of the afferents to the inferior olive in cat. I. -- Cervical spinal and dorsal column nuclei projections.

Localization of the cell bodies of the fibers of the direct spino-olivary pathways as well as those laying in the dorsal column nuclei and the nucleus cervicalis lateralis as the indirect pathway, have been studied using horseradish peroxidase injected in the inferior olive. The injection sites were both large, involving no less than one third of the antero-posterior extent of the inferior olive, and small, involving less than one third. Labeling of the spinal cord was never found beyond the TI segment even after a seven day survival time. Significant positive reaction was found only in the upper cervical levels contralaterally in the lamina VI and bilaterally in the border regions of laminae VII, VIII and IX. Few marked neurons were found in the contralateral nucleus cervicalis lateralis. More numerous labelled cells were found in the dorsal column nuclei, gracilis and cuneatus. Although positive reactions were observed bilaterally, it was far more important in the contralateral side. The topographical relationship between the dorsal column nuclei and the inferior olive is also described.