The origins, course and distribution of the dorsal and intermediate acoustic striae in the rhesus monkey.

Abstract

AbstractAttempts were made to produce discrete stereotactic lesions in the dorsal cochlear nucleus (Dc) in a series of rhesus monkeys. Anterograde degeneration was studied using Nauta and Fink‐Heimer techniques. Following lesions confined to the caudal pole of Dc, a few degenerated fibers projected to the contralateral lateral superior olivary nucleus via the dorsal acoustic stria. Degeneration was distributed to the contralateral ventral and to a lesser extent dorsal nuclei of the lateral lemniscus. The contralateral central nucleus of the inferior colliculus was a major site of termination of second order auditory fibers; a small number of degenerated fibers ascended to this nucleus ipsilaterally, and a few crossed in its commissure. A few degenerated fibers also were present in the contralateral magnocellular division of the medial geniculate body.When Dc was damaged at levels which overlie the posteroventral cochlear nucleus (Pv), or after lesions involving both subdivisions, degeneration was seen in the intermediate as well as in the dorsal acoustic stria. Fibers arising in Pv coursed through Dc and were interrupted by lesions in the latter. In addition to degeneration described above, fibers projected to the ipsilateral lateral superior olivary nucleus, contralateral medial trapezoid nucleus, and bilaterally to dorsal retroolivary and to preolivary cell groups. No degeneration was seen in the trapezoid body. Lesions involving the posteroventral and anteroventral (Av) cochlear nuclei produced degeneration in the intermediate acoustic stria and in the trapezoid body, but not in the dorsal stria. Degeneration in the intermediate acoustic stria was similar to that present after lesions affecting Dc and Pv. Thus, since Av does not project crossed fibers to this structure, these findings indicate that Pv sends some fibers to the contralateral as well as ipsilateral lateral superior olivary nucleus.