Topographical organization of the tecto-olivo-cerebellar projection in the cat.

The superior colliculus sends a climbing fiber output to cerebellar vermal lobules VI-VII through the inferior olive. The present study in cats morphologically clarified the existence of a topographical organization in the tecto-olivo-cerebellar projection. A horseradish peroxidase study on the tecto-olivary projection showed that the rostral and caudal superior colliculus projected mostly contralaterally to the caudal and rostral areas of the caudomedial part of the medial accessory olive, respectively. The lateral superior colliculus was found to project more laterally than was the medial superior colliculus. Investigation on the olivocerebellar projection demonstrated that the rostral and caudal areas of the caudomedial part of the medial accessory olive sent climbing fiber terminals contralaterally to the lateral and medial parts of vermal lobules VI-VII, respectively. Thus, it was revealed that the rostral superior colliculus projected mostly to the medial part of ipsilateral vermal lobules VI-VII while the caudal superior colliculus projected mostly to the lateral part of ipsilateral vermal lobules VI-VII.