Trigeminal projections to cerebellar tactile areas in the rat-origin mainly from n. interpolaris and n. principalis.

Four new tactile areas in the cerebellar cortex (crus I, crus II, paramedian lobule and uvula) have recently been described in the rat. Ipsilateral orofacial regions are chiefly represented in these areas. Our study of trigeminocerebellar afferents to these areas using the HRP retrograde tracing technique shows that they almost all arise in the interpolar and principal trigeminal nuclei mostly from the ipsilateral side. No labelled cells were found in the mesencephalic or caudal trigeminal nuclei after large cerebellar injections and the few labelled cells in n. oralis were found in the dorsomedial tip of that nucleus.