GABA- and glycine-immunoreactive projections from the superior olivary complex to the cochlear nucleus in guinea pig

Ostapoff, E.-Michael; Benson, Christina G.; Marie, Richard L. Saint

doi:10.1002/(sici)1096-9861(19970519)381:4<500::aid-cne9>3.0.co;2-6

Cited by 95 publications

(75 citation statements)

References 75 publications

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“…The contralateral inhibition of cells in the L SO, which occurs via fast conducting axons and powerf ul synapses, has a minimum latency of ϳ4.3 msec [Joris and Yin (1998); group delay ϩ acoustic delay], and estimates based on first spike latency using tones with 2.5 msec rise time are longer, at values Ͼ6 msec (Tsuchitani, 1997). Considering (1) the extra distance to the DC N, (2) the longer rise time used here (4 msec), (3) the lack of evidence for any known fast-conducting inhibitory pathway from the superior olivary complex to the C N, and (4) the extensive projections from periolivary cell groups to the C N (Ostapoff et al, 1997) and the generally longer latencies that are recorded in periolivary regions (Tsuchitani, 1977), it is unlikely that the short-latency contralateral inhibition of DC N would be derived through a link in this complex.…”

Section: Response To Contralateral Stimulationmentioning

confidence: 93%

“…Various descending projections to the CN exist (Conlee and Kane, 1982;Brown et al, 1988;Weedman and Ryugo, 1996;Ostapoff et al, 1997), and an estimate of the latency and time course of the contralateral inhibition may narrow down the possible sources involved. We presented a contralateral stimulus during the sustained portion of the response to long ipsilateral CF tones in 10 type IIIϩIV cells.…”

Section: Response To Contralateral Stimulationmentioning

confidence: 99%

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Temporal and Binaural Properties in Dorsal Cochlear Nucleus and Its Output Tract

Joris

Smith

1998

J. Neurosci.

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The dorsal cochlear nucleus (DCN) is one of three nuclei at the terminal zone of the auditory nerve. Axons of its projection neurons course via the dorsal acoustic stria (DAS) to the inferior colliculus (IC), where their signals are integrated with inputs from various other sources. The DCN presumably conveys sensitivity to spectral features, and it has been hypothesized that it plays a role in sound localization based on pinna cues. To account for its remarkable spectral properties, a DCN circuit scheme was developed in which three inputs converge onto projection neurons: auditory nerve fibers, inhibitory interneurons, and wide-band inhibitors, which possibly consist of Onset-chopper (O c ) cells. We studied temporal and binaural properties in DCN and DAS and examined whether the temporal properties are consistent with the model circuit.Interneurons (type II) and projection (types III and IV) neurons differed from O c cells by their longer latencies and temporally nonlinear responses to amplitude-modulated tones. They also showed evidence of early inhibition to clicks. All projection neurons examined were inhibited by stimulation of the contralateral ear, particularly by broadband noise, and this inhibition also had short latency. Because O c cells had shortlatency responses and were well driven by broadband stimuli, we propose that they provide short-latency inhibition to DCN for both ipsilateral and contralateral stimuli. These results indicate more complex temporal behavior in DCN than has previously been emphasized, but they are consistent with the recently described nonlinear behavior to spectral manipulations and with the connectivity scheme deduced from such manipulations. Key words: audition; dorsal cochlear nucleus; dorsal acoustic stria; amplitude modulation; temporal; binaural; catThe dorsal cochlear nucleus (DC N) is one of three nuclei at the terminal zone of the auditory nerve. Axons of its projection cells leave the nucleus via the dorsal acoustic stria (DAS) and project to the inferior colliculus (IC) (Osen, 1972;Adams and Warr, 1976;Oliver, 1984). The DC N is the most complex subdivision of the cochlear nucleus, and its f unction remains unknown. Young and colleagues (1992) proposed that the DC N serves a role in the detection of spatial elevation of a sound source by virtue of its sensitivity to spectral features such as those resulting from the directionally dependent filtering properties of the pinna.One strategy for obtaining clues to the f unction of the DCN is to examine the effect of its very nonlinear spectral properties (Nelken et al., 1997) on the IC (Semple and Aitkin, 1980). For example, inputs from the DC N partly converge with inputs from the lateral superior olive (L SO) (Oliver et al., 1997). C ells in the LSO are sensitive to interaural level differences (ILDs) (Boudreau and Tsuchitani, 1968) and interaural time differences of amplitude-modulated (AM) tones , which are cues to the azimuthal position of a sound source. C ells in the IC with spatially restricted receptive fields...

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Section: Response To Contralateral Stimulationmentioning

confidence: 93%

Section: Response To Contralateral Stimulationmentioning

confidence: 99%

Temporal and Binaural Properties in Dorsal Cochlear Nucleus and Its Output Tract

Joris

Smith

1998

J. Neurosci.

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“…Of course, the DCN receives inhibitory inputs from a variety of loci in the superior olive (Ostapoff et al, 1997) and inferior colliculus (Shore et al, 1991;Malmierca et al, 1996), which could provide the additional inhibitory input. At present, nothing is known about the notch noise responses of these neurons, except for the type O units in the inferior colliculus, which show responses to rising band edges (Davis et al, 2003) and could provide the additional inhibitory input, either directly or indirectly.…”

Section: The Additional Inhibitory Inputmentioning

confidence: 99%

Spectral Edge Sensitivity in Neural Circuits of the Dorsal Cochlear Nucleus

Reiss¹,

Young²

2005

J. Neurosci.

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One possible function of the dorsal cochlear nucleus (DCN) is discrimination of head-related transfer functions (HRTFs), spectral cues used for vertical sound localization. Recent psychophysical and physiological studies suggest that steep, rising spectral edges may be the features used to identify HRTFs. Here we showed, using notch noise and noise band stimuli presented over a range of frequencies, that a subclass of DCN type IV neurons responded with a response peak when the rising spectral edge of a notch or band was aligned near best frequency (BF). This edge sensitivity was correlated with weak or inhibited responses to broadband noise and inhibition in receptive fields at frequencies below BF. Some aspects of the inhibition shaping the response peak, namely inhibition to rising edges below BF and to falling edges at BF, could be explained by the properties of type II interneurons with BFs below those of the type IV neurons. However, many type IV neurons also showed inhibitory responses with the rising spectral edge just above BF, and these responses could not be reproduced by current models of DCN circuitry. Therefore, a new component of the DCN circuit is needed to fully explain the responses to rising spectral edges. This shaping of edge sensitivity by inhibition to rising spectral edges both below and above BF suggests the specialization of DCN for spectral edge coding along the tonotopic gradient.

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“…Transmission electron microscopic studies corroborated these findings by showing that these small terminals enclose flattened vesicles, which are thought to contain inhibitory transmitters (Cant 1991;Osen and Ottersen 1996). The GABAergic terminals may originate from neurons in the ventral nucleus of the trapezoid body (Ostapoff et al 1997), which themselves receive excitatory input from axon collaterals of globular bushy cells . The superior paraolivary nucleus, in which most neurons label for GABA, might provide another source of GABAergic input to the MNTB (Helfert et al 1989).…”

Section: Introductionmentioning

confidence: 99%

The Medial Nucleus of the Trapezoid Body in the Gerbil Is More Than a Relay: Comparison of Pre- and Postsynaptic Activity

Kopp-Scheinpflug

Lippe

Dörrscheidt

et al. 2003

JARO - Journal of the Association for Research in Otolaryngolog

114

158

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The medial nucleus of the trapezoid body (MNTB) plays an important role in the processing of interaural intensity differences, a feature that is critical for the localization of sound sources. It is generally believed that the MNTB functions primarily as a passive relay in converting excitatory input originating from the contralateral cochlear nucleus (CN) into an inhibitory input to the ipsilateral lateral superior olive. However, studies showing that the MNTB itself is also the target of inhibitory input suggest that the MNTB may serve more than a sign-converting function. To examine the fidelity of signal transmission at the CN-MNTB synapse, presynaptic calyceal potentials (''prepotentials''), reflecting the excitatory input to the MNTB neuron, and postsynaptic action potentials were simultaneously monitored with the same electrode during in vivo extracellular recordings from the gerbil's MNTB. Presynaptic activity differed from postsynaptic activity in several respects: (1) Spontaneous and sound-evoked discharge rates were greater presynaptically than postsynaptically. (2) Frequency tuning was sharper postsynaptically than presynaptically. (3) Calyceal terminals and MNTB neurons both showed phasic-tonic response patterns to tonal stimulation, but the duration of the onset response and the level of the tonic component were reduced postsynaptically. (4) Phase-locking to sound frequencies up to 1 kHz was greater postsynaptically than presynaptically. (5) The rate-intensity characteristics of pre-and postsynaptic activities differed significantly from each other in half of the MNTB neurons. To test the hypothesis that acoustically evoked inhibition of MNTB neurons contributed to the relatively lower levels of postsynaptic discharge, two-tone stimulation was applied, wherein the response to one tone-burst, set at the neuron's characteristic frequency, can be reduced by addition of a second ''inhibitory'' tone. The inhibitory tone caused a much larger reduction in post-than in presynaptic activity, indicating an acoustically evoked inhibitory influence directly on MNTB units. These findings show that transmission at the CN-MNTB synapse does not occur in a fixed one-to-one manner and that the response of MNTB neurons reflects the integration of their excitatory and inhibitory inputs.

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GABA- and glycine-immunoreactive projections from the superior olivary complex to the cochlear nucleus in guinea pig

Cited by 95 publications

References 75 publications

Temporal and Binaural Properties in Dorsal Cochlear Nucleus and Its Output Tract

Temporal and Binaural Properties in Dorsal Cochlear Nucleus and Its Output Tract

Spectral Edge Sensitivity in Neural Circuits of the Dorsal Cochlear Nucleus

The Medial Nucleus of the Trapezoid Body in the Gerbil Is More Than a Relay: Comparison of Pre- and Postsynaptic Activity

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