The course and termination of the stria of Monakow and stria of Held were studied with Nauta-Gygax technique following a localized lesion of the dorsal cochlear nucleus i n the cat. A dense preterminal degeneration within all homolateral primary cochlear nuclei and a tract of degenerated fibers crossing the restiform body dorsally were found. This tract divides i n two branches forming the stria of Held and stria of Monakow.The stria of Held followed the course described by classical anatomists. In the homolateral side, the stria gave terminals to the medial and lateral preolivary nuclei, lateral superior olive nucleus and retro-olivary groups. In the contralateral side, preterminal degeneration was found in the medial preolivary nucleus and medial retro-olivary group.The stria of Monakow is essentially crossed pathway given numerous terminals to the contralateral dorsal retro-olivary group, rostra1 part of the lateral preolivary nucleus, the ventral and dorsal nuclei of the lateral lemniscus, and nucleus of the inferior colliculus.The primary cochlear nuclei as described by Lorente de N6 ('33) in Golgi preparations was divided in 13 regions of specific cellular structure. The regions were grouped in six nuclei : tuberculum acousticum ( 4 regions), nucleus centralis ( a specialized region of the tuberculum acousticum), nucleus interstitialis, nucleus posterioris ( 3 regions), nucleus lateralis (a specialized region of the nucleus posterioris), and ganglion ventrale (3 regions). In Nissl's preparations the borderline between one region and another cannot be clearly differentiated. For this reason and for convenience in the analysis of functional data, the classification of Lorente de N6 has been simplified into four major groups (Ross, Galambos and Hughes, '59; Kiang, Pfeiffer, Warr and Backus, '65). The terminology is as follows : The tuberculum acousticum and nucleus centralis is called the dorsal cochlear nucleus; the nucleus posterioris and nucleus lateralis are grouped as the posteroventral nucleus or posterior ventral cochlear nucleus; the ganglion ventrale is called the anteroventral or anterior ventral cochlear nucleus; and the nucleus interstitialis. The latter is here called the interstitial cochlear nucleus in order to clearly differentiate it from the interstitial nucleus of the vestibular nerve and the interstitial nucleus of the medial longitudinal fasciculus.3. COMP. NEUR., 131: 371-386.As described by classical anatomists (von Monakow, 1891; Held, 1893; van Gehuchten, '02; Ram6n y Cajal, '09; Lorente de N6, '33; and others), the auditory second order neurons formed three bundles, the stria of Monakow or dorsal acoustic stria, the stria of Held or intermediate stria, and the trapezoid body. There are excellent anatomical accounts of these ascending auditory pathways. Yet the opinions regarding the details about origin, course and termination of the three striae are controversial. For instance, according
The inferior colliculus is a nucleus of obligatory synapse in the ascending brain stem auditory pathways. Projections from the inferior colliculus in primates and insectivores are similar to that demonstrated in other mammals, with short direct projections to the external nucleus of the colliculus and adjacent regions of the central gray and superior colliculus ipsilaterally, and fibers crossing in the commissure of the colliculus to innervate the contralateral central and external nuclei. Long projection fibers enter the brachium of the inferior colliculus bilaterally, but the projection is markedly heavier on the side ipsilateral to the lesion. Brachial fibers supply terminals to two regions of the rostral midbrain tegmentum, the parabrachial area and the interstitial nucleus of the inferior brachium. On reaching the thalamus, brachial fibers bypass the caudal tip of the medial geniculate, but arborize to form a dense plexus of axons and terminals throughout the remainder of the principal nucleus of the geniculate and the entire internal division on the ipsilateral side. A lighter and more restricted projection to the opposite medial geniculate is seen in all primates, and particularly in the hedgehog. The small size of the contralateral tectothalamic pathway in the hedgehog is the only significant species difference noted in this study.
The inferior colliculus is a nucleus of obligatory synapse in the ascending brain stem auditory pathways. Projections from the inferior colliculus in primates and insectivores are similar to that demonstrated in other mammals, with short direct projections to the external nucleus of the colliculus and adjacent regions of the central gray and superior colliculus ipsilaterally, and fibers crossing in the commissure of the colliculus to innervate the contralateral central and external nuclei. Long projection fibers enter the brachium of the inferior colliculus bilaterally, but the projection is markedly heavier on the side ipsilateral to the lesion. Brachial fibers supply terminals to two regions of the rostral midbrain tegmentum, the parabrachial area and the interstitial nucleus of the inferior brachium. On reaching the thalamus, brachial fibers bypass the caudal tip of the medial geniculate, but arborize to form a dense plexus of axons and terminals throughout the remainder of the principal nucleus of the geniculate and the entire internal division on the ipsilateral side. A lighter and more restricted projection to the opposite medial geniculate is seen in all primates, and particularly in the hedgehog. The small size of the contralateral tectothalamic pathway in the hedgehog is the only significant species difference noted in this study.
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