Divergent collaterals from deep cerebellar neurons to thalamus and tectum, and to medulla oblongata and spinal cord: retrograde fluorescent and electrophysiological studies.

In cat the existence of collaterals from deep cerebellar neurons, which project to mesencephalon and thalamus has been investigated anatomically by means of the multiple retrograde fluorescent tracer technique as well as electrophysiologically by means of conventional antidromic techniques. Both sets of data indicate that several neurons in the medial nucleus, which project to mesencephalon and thalamus, also distribute collaterals to medulla oblongata and spinal cord. These branching neurons were principally located in the caudal and intermediate portions of the medial nucleus. The electrophysiological data in addition indicate that the branching point of the neurons in the medial nucleus is located relatively close to the cell soma. The anatomical findings show a further group of branching neurons in the lateral nucleus at the border with the interpositus nuclei. The majority of these latter neurons distribute collaterals to medulla oblongata but some distribute collaterals to spinal cord. However, it could not be decided as yet whether the collaterals to the medulla oblongata terminate either in medullary medial reticular formation or in inferior olive or in both.