The trigemino-olivary projection in the cat: contributions of individual subnuclei.

Anterograde autoradiographic methods were used to determine the projection of the principal sensory trigeminal nucleus and of each of the three spinal trigeminal subnuclei to the inferior olivary complex in the cat. Our data reveal that the principal sensory trigeminal nucleus does not contribute to the trigemino-olivary pathway. Each spinal trigeminal subnucleus has a unique contribution to this pathway: pars oralis projects sparsely to the border between the dorsal accessory and principal olives (DAO-PO), pars interpolaris projects mostly to the rostral medial DAO, and pars caudalis projects mostly to the rostral medial part of the ventral leaf of PO and slightly to the caudal medial accessory olive. In the light of recent physiological and anatomical findings, our data indicate that information from each spinal trigeminal subnucleus reaches a different segment of the contralateral inferior olivary complex, which in turn distributes differentially to the cerebellar cortex.