Effects of Anesthesia on Efferent-Mediated Adaptation of the DPOAE

Boyev, K. Paul; Liberman, M. Charles; Brown, M. Christian

doi:10.1007/s101620020044

Cited by 50 publications

(46 citation statements)

References 23 publications

(37 reference statements)

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“…The large amplitudes of the DPOAE changes we observed indicate that the combination of urethane/fentanyl anesthesia produced preinjection reflex strengths approximately as large as those seen in awake animals (Boyev et al, 2002), thus this anesthetic regimen apparently does not significantly diminish the MOC reflex.…”

Section: Dpoae Post-onset Effects As a Moc Reflex Metricmentioning

confidence: 58%

“…Test/retest measurements (see Materials and Methods section) suggested that the Ipsi reflex metric varied as much as 29% and the smaller Contra metric varied as much as 45%. Changes in metrics greater than these values will be thus be considered significant.The large amplitudes of the DPOAE changes we observed indicate that the combination of urethane/fentanyl anesthesia produced preinjection reflex strengths approximately as large as those seen in awake animals (Boyev et al, 2002), thus this anesthetic regimen apparently does not significantly diminish the MOC reflex. …”

mentioning

confidence: 58%

“…At each L 1 step, there were 14 or more L 2 steps that began at 60 dB and increased to L 1 (with L 1 ≤ L 2 ). Responses to two to four complete sets (or matrices) of all primary level combinations (Kujawa and Liberman, 2001;Boyev et al, 2002) were obtained at the beginning of the experiment before injection of KA. From each response matrix, the largest DPOAE change in amplitude (Fig.…”

Section: Methodsmentioning

confidence: 99%

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Medial olivocochlear reflex interneurons are located in the posteroventral cochlear nucleus: A kainic acid lesion study in guinea pigs

Venecia

Liberman

Guinan

et al. 2005

J of Comparative Neurology

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The medial olivocochlear (MOC) reflex arc is probably a three-neuron pathway consisting of type I spiral ganglion neurons, reflex interneurons in the cochlear nucleus, and MOC neurons that project to the outer hair cells of the cochlea. We investigated the identity of MOC reflex interneurons in the cochlear nucleus by assaying their regional distribution using focal injections of kainic acid. Our reflex metric was the amount of change in the distortion product otoacoustic emission (at 2f 1 -f 2 ) just after onset of the primary tones. This metric for MOC reflex strength has been shown to depend on an intact reflex pathway. Lesions involving the posteroventral cochlear nucleus (PVCN), but not the other subdivisions, produced long-term decreases in MOC reflex strength. The degree of cell loss within the dorsal part of the PVCN was a predictor of whether the lesion affected MOC reflex strength. We suggest that multipolar cells within the PVCN have the distribution and response characteristics appropriate to be the MOC reflex interneurons. Keywordshearing; outer hair cell; otoacoustic emission; superior oliveThe auditory system contains several descending pathways (Spangler and Warr, 1991), of which the best-studied is the olivocochlear (OC) efferents. OC neurons reside in the superior olivary complex and project to the cochlea (Fig. 1). The OC system is divided into two subsystems (reviewed by Warr, 1992;. Medial olivocochlear (MOC) neurons have cell bodies in the medial part of the superior olivary complex and project to outer hair cells. Lateral olivocochlear (LOC) neurons have cell bodies in or around the lateral superior olive and project to afferent fibers near inner hair cells (Warr and Guinan, 1979;Liberman, 1980;Liberman and Brown, 1986;Brown, 1987;Vetter and Mugnaini, 1992;Maison et al., 2003). Cholinergic MOC endings in the cochlea exert their effects by means of a nicotinic receptor (Vetter et al., 1999;Elgoyhen et al., 2001Elgoyhen et al., , 2003 that influences outer hair cell function and alters cochlear responses (Wiederhold and Kiang, 1970;Mountain, 1980;Siegel and Kim, 1982;Brown and Nuttall, 1984). For instance, activation of MOC neurons alters distortion product otoacoustic emissions (DPOAEs), causing rapid amplitude changes in the first several hundred milliseconds after primary-tone onset (Liberman et al., 1996;Kujawa and Liberman, 2001). The functional role of this sound-evoked feedback system may include adjusting *Correspondence to: M. Christian Brown, Eaton-Peabody Laboratory, Massachusetts Eye and Ear Infirmary, 243 Charles Street, Boston, MA 02114. E-mail: mcb@epl.meei.harvard.edu. Grant sponsor: National Institute on Deafness and Other Communication Disorders; Grant number: RO1 DC 01089; Grant number: RO1 DC 00188; Grant number: P30 DC05209; Grant number: T32 DC00020-11; Grant sponsor: Triological Society. NIH Public Access NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript cochlear gain, reducing effects of masking noise, and protecting the ear from acous...

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Section: Dpoae Post-onset Effects As a Moc Reflex Metricmentioning

confidence: 58%

mentioning

confidence: 58%

Section: Methodsmentioning

confidence: 99%

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Medial olivocochlear reflex interneurons are located in the posteroventral cochlear nucleus: A kainic acid lesion study in guinea pigs

Venecia

Liberman

Guinan

et al. 2005

J of Comparative Neurology

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“…In the first study (Young and Barta 1986), responses to tones in background noise were measured for cats anesthetized with sodium pentobarbital. The dose of the anesthetic was adjusted to maintain the animals in an areflexive state, so the MOCR was greatly reduced in these animals (Boyev et al 2002). Tone bursts with a duration of 200 ms were presented at the AN fiber's characteristic frequency (CF), in quiet and in three levels of background noise.…”

Section: Comparing Physiological and Modeling Estimates Of Mocr Gain mentioning

confidence: 99%

Modeling the Anti-masking Effects of the Olivocochlear Reflex in Auditory Nerve Responses to Tones in Sustained Noise

Chintanpalli

Jennings

Heinz

et al. 2012

JARO

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The medial olivocochlear reflex (MOCR) has been hypothesized to provide benefit for listening in noise. Strong physiological support for an anti-masking role for the MOCR has come from the observation that auditory nerve (AN) fibers exhibit reduced firing to sustained noise and increased sensitivity to tones when the MOCR is elicited. The present study extended a well-established computational model for normal-hearing and hearing-impaired AN responses to demonstrate that these anti-masking effects can be accounted for by reducing outer hair cell (OHC) gain, which is a primary effect of the MOCR. Tone responses in noise were examined systematically as a function of tone level, noise level, and OHC gain. Signal detection theory was used to predict detection and discrimination for different spontaneous rate fiber groups. Decreasing OHC gain decreased the sustained noise response and increased maximum discharge rate to the tone, thus modeling the ability of the MOCR to decompress AN fiber rate-level functions. Comparing the present modeling results with previous data from AN fibers in decerebrate cats suggests that the ipsilateral masking noise used in the physiological study may have elicited up to 20 dB of OHC gain reduction in addition to that inferred from the contralateral noise effects. Reducing OHC gain in the model also extended the dynamic range for discrimination over a wide range of background noise levels. For each masker level, an optimal OHC gain reduction was predicted (i.e., where maximum discrimination was achieved without increased detection threshold). These optimal gain reductions increased with masker level and were physiologically realistic. Thus, reducing OHC gain can improve tone-in-noise discrimination even though it may produce a "hearing loss" in quiet. Combining MOCR effects with the sensorineural hearing loss effects already captured by this computational AN model will be beneficial for exploring the implications of their interaction for the difficulties hearing-impaired listeners have in noisy situations.

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“…Furthermore, broadband noise typically evoked higher MOC firing rates than tones (Liberman 1988;Brown et al 1998), which is consistent with the MOC neurons integrating afferent activity broadly across frequency. Another factor is that all of the recordings from single MOC fibers were from anesthetized animals but MOC activation is stronger in awake animals (Boyev et al 2002). Overall, it seems likely that (1) the narrow tone TCs from MOC fibers are not good indicators of brainstem across-frequency convergence of MOC activation, (2) both humans and animals have MOC systems that integrate incoming activation widely across cochlear regions, and (3) the frequency integration of MOC effects in awake humans shown by both Figs.…”

Section: How Does the Observed Inhibition Of Sfoaes Correspond To Neumentioning

confidence: 99%

Human Medial Olivocochlear Reflex: Effects as Functions of Contralateral, Ipsilateral, and Bilateral Elicitor Bandwidths

Lilaonitkul

Guinan

2009

JARO

111

100

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Animal studies have led to the view that the acoustic medial olivocochlear (MOC) efferent reflex provides sharply tuned frequency-specific feedback that inhibits cochlear amplification. To determine if MOC activation is indeed narrow band, we measured the MOC effects in humans elicited by 60-dB sound pressure level (SPL) contralateral, ipsilateral, and bilateral noise bands as a function of noise bandwidth from 1/2 to 6.7 octaves. MOC effects were quantified by the change in stimulus frequency otoacoustic emissions from 40 dB SPL probe tones near 0.5, 1, and 4 kHz. In a second experiment, the noise bands were centered 2 octaves below probe frequencies near 1 and 4 kHz. In all cases, the MOC effects increased as elicitor bandwidth increased, with the effect saturating at about 4 octaves. Generally, the MOC effects increased as the probe frequency decreased, opposite expectations based on MOC innervation density in the cochlea. Bilateral-elicitor effects were always the largest. The ratio of ipsilateral/contralateral effects depended on elicitor bandwidth; the ratio was large for narrow-band probe-centered elicitors and approximately unity for wide-band elicitors. In another experiment, the MOC effects from increasing elicitor bandwidths were calculated from measurements of the MOC effects from adjacent half-octave noise bands. The predicted bandwidth function agreed well with the measured bandwidth function for contralateral elicitors, but overestimated it for ipsilateral and bilateral elicitors. Overall, the results indicate that (1) the MOC reflexes integrate excitation from almost the entire cochlear length, (2) as elicitor bandwidth is increased, the excitation from newly stimulated cochlear regions more than overcomes the reduced excitation at frequencies in the center of the elicitor band, and (3) contralateral, ipsilateral, and bilateral elicitors show MOC reflex spatial summation over most of the cochlea, but ipsilateral spatial summation is less additive than contralateral.

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Effects of Anesthesia on Efferent-Mediated Adaptation of the DPOAE

Cited by 50 publications

References 23 publications

Medial olivocochlear reflex interneurons are located in the posteroventral cochlear nucleus: A kainic acid lesion study in guinea pigs

Medial olivocochlear reflex interneurons are located in the posteroventral cochlear nucleus: A kainic acid lesion study in guinea pigs

Modeling the Anti-masking Effects of the Olivocochlear Reflex in Auditory Nerve Responses to Tones in Sustained Noise

Human Medial Olivocochlear Reflex: Effects as Functions of Contralateral, Ipsilateral, and Bilateral Elicitor Bandwidths

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