Distribution of cerebellar fiber terminals in the midbrain visuomotor areas: an autoradiographic study in the cat

Abstract

Cerebellar fibers to the midbrain visuomotor areas were traced in the cat auto-radiographically after injections of tritiated amino acids into individual cerebellar nuclei. Fibers from the dentate (DN), anterior interpositus (AIN) and posterior interpositus (PIN) nuclei were distributed contralaterally, while those from the fastigial nucleus (FN) bilaterally. The FN fibers appeared to arise mainly from the caudal half of the FN. In the superior colliculus (SC), the FN or DN fibers were more numerous than the PIN fibers, and the areas of termination of the FN fibers were located more medially than those of the DN and PIN fibers. These cerebellotectal fiber terminals were in the intermediate and deep SC layers; clustering of terminal silver grains was noted in the FN and DN fibers-recipient areas in the intermediate gray layer. In the pretectum, the DN fibers terminated ventrally in the reticular part of the anterior pretectal nucleus and the posterior pretectal nucleus. THe AIN fibers terminated ventrally in the compact part of the anterior pretectal nucleus and the posterior pretectal nucleus. The nucleus of the posterior commissure received cerebellar fibers chiefly from the DN, and additionally from the FN. The nucleus of Darkschewitsch and the interstitial nucleus of Cajal received fibers from all cerebellar nuclei. No cerebellar fibers terminated in the extraocular motor nuclei and the Edinger-Westphal and anteromedian nuclei.