THE PROJECTIONS OF THE COCHLEAR NUCLEI IN THE CENTRAL AUDITORY PATHWAY IN ALBINO RATS

The dorsal cochlear nucleus, the anterior or the posterior portion of the ventral cochlear nucleus was selectively destroyed unilaterally on 13 albino rats and their efferent projections in the central auditory pathway were studied by the Nauta technique. Fibers from all the 3 parts of the cochlear nuclei project as far as the inferior colli- culus, but none was found to reach the medial geniculate body. It is concluded, there- fore, that the central auditory pathway consists at least of 4 orders of neurons. The emerging fibers from the dorsal cochlear nucleus run in the dorsal acoustic stria and project chiefly into the contralateral nucleus of inferior colliculus and ventral nucleus of lateral lemniscus. Besides, a few fibers terminate in the contralateral dorsal trapezoid nucleus and dorsal nucleus of lateral lemniscus. The projections of the anterior and posterior portions of the ventral cochlear nucleus are essentially the same. Both project via the trapezoid body, the dorsal and the inter- mediate acoustic striae. They terminate in the lateral half of the ipsilateral superior olivary complex and, contralaterally, in the medial half of the superior olivary complex, the ventral and dorsal (a few) nuclei of the lateral lemnicus and the nucleus of inferior colliculus. The anterior portion of the ventral cochlear nucleus, furthermore, has a weak connection with the ipsilateral nuclei of lateral lemniscus and nucleus of inferior colliculus. There is a suggestive topological localization in the lateral superior olivary nucleus and the medial trapezoid nucleus.