Cytoarchitecture of the cochlear nuclei in the cat

Osen, Kirsten K.

doi:10.1002/cne.901360407

Cited by 660 publications

(411 citation statements)

References 14 publications

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“…OC neurons and their collateral branches were visualized using stains for acetylcholinesterase (Schuknecht and Nomura 1965;Osen 1969;Brown and Howlett 1972;Warr 1975;Martin 1981;White and Warr 1983;Osen et al 1984;Brown and Levine 2008). Available data suggest that this stain is a specific marker for OC neurons in the mouse superior olivary complex because it yields essentially the same spatial distribution and number as retrograde labeling of OC neurons (Brown and Levine 2008).…”

Section: Oc Somatamentioning

confidence: 99%

Olivocochlear Neuron Central Anatomy Is Normal in α9 Knockout Mice

Brown

Vetter

2008

JARO

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Olivocochlear (OC) neurons were studied in a transgenic mouse with deletion of the α9 nicotinic acetylcholine receptor subunit. In this α9 knockout mouse, the peripheral effects of OC stimulation are lacking and the peripheral terminals of OC neurons under outer hair cells have abnormal morphology. To account for this mouse's apparently normal hearing, it has been proposed to have central compensation via collateral branches to the cochlear nucleus. We tested this idea by staining OC neurons for acetylcholinesterase and examining their morphology in knockout mice, wild-type mice of the same background strain, and CBA/CaJ mice. Knockout mice had normal OC systems in terms of numbers of OC neurons, dendritic patterns, and numbers of branches to the cochlear nucleus. The branch terminations were mainly to edge regions and to a lesser extent the core of the cochlear nucleus, and were similar among the strains in terms of the distribution and staining density. These data demonstrate that there are no obvious changes in the central morphology of the OC neurons in α9 knockout mice and make less attractive the idea that there is central compensation for deletion of the peripheral receptor in these mice.

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Section: Oc Somatamentioning

confidence: 99%

Olivocochlear Neuron Central Anatomy Is Normal in α9 Knockout Mice

Brown

Vetter

2008

JARO

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“…The two somata of origin giving rise to the small dendrites were both cochlear-nucleus ''small cells '' (Osen 1969;Hackney and Osen 1985). One of these small cells and nearby granule cells are shown in Figure 4, and silhouettes of both small cells are shown in Figure 5.…”

Section: Small Dendrites Were the Most Common Targetsmentioning

confidence: 99%

“…Type I fibers have an excitatory influence on their postsynaptic targets, leading to discharge of cochlear-nucleus neurons (Pfeiffer 1966;Golding et al 1995;Kopp-Scheinpflug et al 2002). Type I targets in the cochlear nucleus are a variety of types of neurons (Brawer and Morest 1975;Rouiller et al 1986), which have been classified by their morphology using different stains (Osen 1969;Brawer et al 1974). The postsynaptic targets of type II fibers in the cochlear nucleus are almost entirely unknown.…”

Section: Introductionmentioning

confidence: 99%

Postsynaptic Targets of Type II Auditory Nerve Fibers in the Cochlear Nucleus.

Benson

Brown

2004

JARO

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Type II auditory nerve fibers, which provide the primary afferent innervation of outer hair cells of the cochlea, project thin fibers centrally and form synapses in the cochlear nucleus. We investigated the postsynaptic targets of these synapses, which are unknown. Using serial-section electron microscopy of fibers labeled with horseradish peroxidase, we examined the border of the granule-cell lamina in mice, an area of type II termination that receives branches having swellings with complex shapes. About 70% of the swellings examined with the electron microscope formed morphological synapses, which is a much higher value than found in previous studies of type II swellings in other parts of the cochlear nucleus. The high percentage of synapses enabled a number of postsynaptic targets to be identified. Most of the targets were small dendrites. Two of these dendrites were traced to their somata of origin, which were cochlear-nucleus ''small cells'' situated at the border of the granule-cell lamina. These cells did not appear to receive any terminals containing synaptic vesicles that were large and round, indicating a lack of input from type I auditory nerve fibers. Nor did type II swellings or targets participate in the synaptic glomeruli formed by mossy terminals and the dendrites of granule cells. Other type II synapses were axosomatic and their targets were large cells, which were presumed multipolar cells and one cell with characteristics of a globular bushy cell. These large cells almost certainly receive additional input from type I auditory nerve fibers, which provide the afferent innervation of the cochlear inner hair cells. A few type II postsynaptic targets-the two small cells as well as a large dendrite-received synapses that had accompanying postsynaptic bodies, a likely marker for synapses of medial olivocochlear branches. These targets thus probably receive convergent input from type II fibers and medial olivocochlear branches. The diverse nature of the type II targets and the examples of segregated convergence of other inputs illustrates the synaptic complexity of type II input to the cochlear nucleus.

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“…The nomenclature used here for the cytoarchitectonic subdivisions and cell types of the cochlear nucleus follows that of Osen (1969Osen ( , 1970 because smaller subdivisions defined in Golgi material (Brawer et al 1974;Cant and Morest 1984;Tolbert and Morest 1982) are difficult to distinguish in our unstained sections reacted for demonstration of NB labeling. For descriptions of labeled fiber and synaptic terminal morphology, the terminology of Rouiller et al (1986) is adopted.…”

Section: Measurements Of Cn Projection Laminaementioning

confidence: 99%

Topography of Auditory Nerve Projections to the Cochlear Nucleus in Cats after Neonatal Deafness and Electrical Stimulation by a Cochlear Implant

Leake

Hradek

Bonham

et al. 2008

JARO

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We previously reported that auditory nerve projections from the cochlear spiral ganglion (SG) to the cochlear nucleus (CN) exhibit clear cochleotopic organization in adult cats deafened as neonates before hearing onset. However, the topographic specificity of these CN projections in deafened animals is proportionately broader than normal (less precise relative to the CN frequency gradient). This study examined SG-to-CN projections in adult cats that were deafened as neonates and received a unilateral cochlear implant at ∼7 weeks of age. Following several months of electrical stimulation, SG projections from the stimulated cochleae were compared to projections from contralateral, non-implanted ears. The fundamental organization of SG projections into frequency band laminae was clearly evident, and discrete projections were always observed following double SG injections in deafened cochleae, despite severe auditory deprivation and/or broad electrical activation of the SG. However, when normalized for the smaller CN size after deafness, AVCN, PVCN, and DCN projections on the stimulated side were broader by 32%, 34%, and 53%, respectively, than projections in normal animals (although absolute projection widths were comparable to normal). Further, there was no significant difference between projections from stimulated and contralateral non-implanted cochleae. These findings suggest that early normal auditory experience may be essential for normal development and/or maintenance of the topographic precision of SG-to-CN projections. After early deafness, the CN is smaller than normal, the topographic distribution of these neural projections that underlie frequency resolution in the central auditory system is proportionately broader, and projections from adjacent SG sectors are more overlapping. Several months of stimulation by a cochlear implant (beginning at ∼7 weeks of age) did not lessen or exacerbate these degenerative changes observed in adulthood. One clinical implication of these findings is that congenitally deaf cochlear implant recipients may have central auditory system alterations that limit their ability to achieve spectral selectivity equivalent to postlingually deafened subjects.

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Cytoarchitecture of the cochlear nuclei in the cat

Cited by 660 publications

References 14 publications

Olivocochlear Neuron Central Anatomy Is Normal in α9 Knockout Mice

Olivocochlear Neuron Central Anatomy Is Normal in α9 Knockout Mice

Postsynaptic Targets of Type II Auditory Nerve Fibers in the Cochlear Nucleus.

Topography of Auditory Nerve Projections to the Cochlear Nucleus in Cats after Neonatal Deafness and Electrical Stimulation by a Cochlear Implant

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