Posterior Ventral Cochlear Nucleus Research Articles

The projection of the acoustic nerve to the ventral cochlear nucleus of the rat. A Golgi study.

AbstractAcoustic nerve fibers, stained by the rapid Golgi method, were observed to bifurcate, after entering the ventral cochlear nucleus, into an ascending and a descending branch. Each branch was composed of fibers running parallel to each other with very little overlap. Prior to bifurcating, the acoustic nerve fibers gave rise to collaterals which ramified in the region of the bifurcations. Ascending branch fibers terminated in bulbs of Held and bore from zero to five additional collateral endings, including bulbs of Held. Descending, branch fibers gave rise within the posterior ventral cochlear nucleus to from zero to five collateral endings. These included large endings identified as bulbs of Held. Ascending and descending branch collaterals did not extend beyond 40–50 μ from their paret axons. Descending branch fibers projected into the dorsal cochlear nucleus. The area of the ventral cochlear nucleus dorsal to the region of bifurcations was innervated in a unique manner. This innervation occurred via long dorsally running collaterals arising from the most dorsal fibers of the ascending and descending branch projections.The data suggest morphological correlates of certain neurophysiological and behavioral findings in the areas of auditory localization and discrimination.

Ascending projections of the primary cochlear nuclei and nucleus laminaris in the pigeon.

AbstractAuditory projections were studied, by the Nauta method, from medullary to mesencephalic levels following lesions in nuclei magnocellularis, angularis and laminaris and transection of the dorsal cochlear decussation and trapezoid body in the midline of the medulla.Fragmented axons project bilaterally to nucleus laminaris from the medial part of nucleus magnocellularis. Degenerated fibers from the lateral part of nucleus magnocellularis, medial part of nucleus angularis. and nucleus laminaris projects to the homolateral superior olivary nucleus. cross the raphé in the trapezoid body, ascend in the contralateral lateral lemniscus, distribute to the ventral and lateroventral nuclei of the lateral lemniscus and, at least third order axons from nucleus laminaris. terminate in nucleus mesencephali lateralis pars dorsalis. No ascending auditory neurons project, even following midventral section of the trapezoid body, to nucleus isthmi, nucleus semilunaris nor. with certainty, to the dorsal nucleus of the lateral lemniscus.This study supports the homology of the avian nucleus mesencephali lateralis pars dorsalis and nucleus laminaris with the mammalian central nucleus of the inferior colliculus and medial superior olivary nucleus respectively. Furthermore, on the basis of fiber projections and cellular organization. nucleus magnocellularis of the pigeon appears to correspond to the anterior ventral cochlear of higher mammals and the medial parts of nucleus angularis to the posterior ventral cochlear nucleus.

The organization of the posterior ventral cochlear nucleus in the rat.

AbstractThe ventral cochlear nucleus was examined in 31 rats' brains prepared according to the protargol method of Bodian. The following regions were delimited on the basis of synaptic, cellular and axonal criteria.Region II, which occupies the central part of the nucleus, consists principally of cells (type g)which receive modified bulbs of Held from the acoustic nerve and which send large axons to the trapezoid body. The cells were graded in size, the smallest (high frequency) being located dorsally and the larges (low frequency) being located ventrally. Associated with region II are the cells (type b) of the acoustic nerve nucleus. These cells receive boutons from the acoustic nerve and send very large axons to the trapezoid body.Region IV is located in the posterior part of the ventral cochlear nucleus and is composed of large multipolar cells (type k). The dendrites of these cells are specifically organized with respect to the fibers of the acoustic nerve. Synaptic endings, from the descending branch of the acoustic nerve, consist of boutons on cell body and dendrites. The axons of these cells compose the stria of Held.Region V is located in the posterior part of the ventral cochlear nucleus and appeared to have only intrinsic connections.All regions received synaptic endings in addition to those which arose from the acoustic nerve.

NUCLEUS OF THE TRAPEZOID BODY: DUAL AFFERENT INNERVATION.

Lesions of the anterior ventral cochlear nucleus caused degeneration of synaptic endings in the anterior half of the nucleus of the trapezoid body. Lesions of the posterior ventral cochlear nucleus caused similar degeneration in the posterior half of the nucleus of the trapezoid body. Thus, the cochlea projects twice upon the nucleus of the trapezoid body.