Cerebellar afferents from the trigeminal sensory nuclei in the cat.

The cerebellar afferent projection from the trigeminal sensory nuclei (TSN) was studied by means of retrograde axonal transport of horseradish peroxidase (HRP). The projection is almost exclusively ipsilateral. Three cortical regions, viz., the intermediate-lateral part of lobulus simplex with the adjacent area of lobule V, the rostralmost folia of the paramedian lobule with the surrounding parts of crus I and II, and lobule IX, especially its rostral two folia, are the main targets for the cerebellar afferent fibres. A few fibres reach also the other cerebellar regions, as shown in Fig. 3. Most of the cerebellar afferent fibres originate in the nucleus interpolaris with nucleus oralis as the second most important region. The projection from the principal nucleus is moderate and reaches primarily the area of the crura bordering on the paramedian lobule and lobule IX. The projections from the nucleus caudalis and nucleus mesencephalicus are scanty. The fibres from the latter reach only the vermal region. The findings are discussed in relation to previous anatomical and physiological observations.