Cerebellar and olivary projections of the external and rostral internal cuneate nuclei in the cat.

The cerebellar projection of the external cuneate nucleus and the adjoining rostral part of the internal cuneate nucleus were investigated by means of anterograde transport of tritiated leucine. The cuneocerebellar tract terminates as mossy fiber rosettes in the granular layer. The termination area has a more or less spherical form with its centre at the ipsilateral side. It comprises the anterior and posterior vermes bilaterally and the ipsilateral hemispheral parts of the anterior and simple lobules, the medial aspect of the ansiform lobule and the paramedian lobule. Within this area the mossy fiber terminals are arranged in continuous sagittal strips, some of them clearly separated from one another. The strips were found in the cerebellar modules A-D. Concomitant bilateral projections to several subdivisions of the inferior olive were found. Some of these provide the anatomical substrate for the simultaneous activation of a number of mossy and climbing fiber zones observed in the anterior lobe following stimulation of different forelimb nerves. No evidence was found for a termination of mossy fiber collaterals in the central cerebellar nuclei.