Ascending brain stem projections of the anteroventral cochlear nucleus in the rhesus monkey

Abstract

Abstract In a series of seventeen rhesus monkeys attempts were made to produce discrete stereotaxic lesions in the anteroventral cochlear nucleus (Av). Anterograde degeneration was described in detail in four cases with lesions confined within the cochlear complex to Av. Fibers decussating at pontine levels coursed exclusively in the trapezoid body. Degenerated fibers projected: ipsi‐laterally to the lateral superior olivary nucleus; bilaterally to the preolivary nuclei; to the lateral side of the ipsilateral medial superior olive and the medial side of the contralateral medial superior olive; and to the contralateral medial trapezoid nucleus. A topographic projection upon the medial superior olive was demonstrated. Projections were bilateral but mainly crossed to the nuclei of the lateral lemniscus and central nucleus of the inferior colliculus; the posterior end of the ipsilateral ventral nucleus of the lateral lemniscus contained an island of profuse degeneration. A few fibers crossed in the commissure of the inferior colliculus. Few if any fibers from Av projected to the contralateral magnocellular medial geniculate.