Olivocochlear Efferents: Anatomy, Physiology, Function, and the Measurement of Efferent Effects in Humans

Guinan, John J.

doi:10.1097/01.aud.0000240507.83072.e7

Cited by 560 publications

(622 citation statements)

References 128 publications

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“…The main role of MOC efferents in everyday hearing is thought to be to reduce masking (Guinan 2006). The narrow MOC-fiber TCs and the MOC cochlear innervation pattern have suggested that the MOC reflex provides frequency-specific antimasking (Winslow and Sachs 1987).…”

Section: Implications Of the Results For The Role Of Moc Efferents Inmentioning

confidence: 99%

“…This tone completely suppressed the probefrequency SFOAE, with the result that only MEM contractions could produce a change in the sound pressure at the SFOAE probe frequency. Thus, the presence of an elicitor-induced change in the earcanal sound at the SFOAE frequency indicates there has been a MEM contraction, while responses within the noise floor are taken to mean there has been no significant MEM contraction (see Guinan 2006).…”

Section: Middle Ear Muscle Contraction Testmentioning

confidence: 99%

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

Lilaonitkul

Guinan

2009

JARO

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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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Section: Implications Of the Results For The Role Of Moc Efferents Inmentioning

confidence: 99%

Section: Middle Ear Muscle Contraction Testmentioning

confidence: 99%

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

Lilaonitkul

Guinan

2009

JARO

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111

100

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“…Few studies have used this approach, and they report greater effects in the tails than in the tips of the PTCs (Kawase et al 2000;Quaranta et al 2005;Vinay and Moore 2008). At first sight, this appears inconsistent with the wellestablished physiological evidence that efferent activation affects mostly the tip of basal BM tuning curves, that is, the stimulus frequencies subject to cochlear compression (Guinan 2006(Guinan , 2010. This inconsistency, however, is likely more apparent than real as, in contrast to BM tuning curves, two stimuli are required to measure a PTC (a probe tone and a masker sound) and so efferents may affect either or both of them.…”

Section: Introductionmentioning

confidence: 97%

“…Medial olivocochlear (MOC) efferent neurons innervate these cells and convey signals that are capable of controlling BM sensitivity and tuning (Murugasu and Russell 1996;Russell and Murugasu 1997;Cooper and Guinan 2006). MOC efferents may be activated in a reflexive manner by contralateral sounds (Guinan 2006(Guinan , 2010. Therefore, cochlear responses may change dynamically in binaural listening situations.…”

Section: Introductionmentioning

confidence: 99%

Contralateral Efferent Reflex Effects on Threshold and Suprathreshold Psychoacoustical Tuning Curves at Low and High Frequencies

Aguilar

Eustaquio-Martín

Lopez‐Poveda

2013

JARO

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Medial olivocochlear efferent neurons can control cochlear frequency selectivity and may be activated in a reflexive manner by contralateral sounds. The present study investigated the significance of the contralateral medial olivocochlear reflex (MOCR) on human psychoacoustical tuning curves (PTCs), a behavioral correlate of cochlear tuning curves. PTCs were measured using forward masking in the presence and in the absence of a contralateral white noise, assumed to elicit the MOCR. To assess MOCR effects on apical and basal cochlear regions over a wide range of sound levels, PTCs were measured for probe frequencies of 500 Hz and 4 kHz and for near-and suprathreshold conditions. Results show that the contralateral noise affected the PTCs predominantly at 500 Hz. At near-threshold levels, its effect was obvious only for frequencies in the tails of the PTCs; at suprathreshold levels, its effects were obvious for all frequencies. It was verified that the effects were not due to the contralateral noise activating the middleear muscle reflex or changing the postmechanical rate of recovery from forward masking. A phenomenological computer model of forward masking with efferent control was used to explain the data. The model supports the hypothesis that the behavioral results were due to the contralateral noise reducing apical cochlear gain in a frequency-and level-dependent manner consistent with physiological evidence. Altogether, this shows that the contralateral MOCR may be changing apical cochlear responses in natural, binaural listening situations.

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“…The apparent discrimination deficits in the dichotic s/n condition could, at least partly, be explained by the influence of the subcortical efferent central auditory system, more specifically the medial olivocochlear bundle (MOCB; see Guinan 2006 for an overview). The function of the MOCB can be investigated by measuring otoacoustic emissions (OAE).…”

Section: Discrimination Deficits and Possible Top-down Engagementmentioning

confidence: 99%

Auditory Processing Disorders with and without Central Auditory Discrimination Deficits

Ludwig

Fuchs

Kruse

et al. 2014

JARO

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Auditory processing disorder (APD) is defined as a processing deficit in the auditory modality and spans multiple processes. To date, APD diagnosis is mostly based on the utilization of speech material. Adequate nonspeech tests that allow differentiation between an actual central hearing disorder and related disorders such as specific language impairments are still not adequately available. In the present study, 84 children between 6 and 17 years of age (clinical group), referred to three audiological centers for APD diagnosis, were evaluated with standard audiological tests and additional auditory discrimination tests. Latter tests assessed the processing of basic acoustic features at two different stages of the ascending central auditory system: (1) auditory brainstem processing was evaluated by quantifying interaural frequency, level, and signal duration discrimination (interaural tests). (2) Diencephalic/telencephalic processing was assessed by varying the same acoustic parameters (plus signals with sinusoidal amplitude modulation), but presenting the test signals in conjunction with noise pulses to the contralateral ear (dichotic signal/ noise tests). Data of children in the clinical group were referenced to normative data obtained from more than 300 normally developing healthy school children. The results in the audiological and the discrimination tests diverged widely. Of the 39 children that were diagnosed with APD in the audiological clinic, 30 had deficits in auditory performance. Even more alarming was the fact that of the 45 children with a negative APD diagnosis, 32 showed clear signs of a central hearing deficit. Based on these results, we suggest revising current diagnostic procedure to evaluate APD in order to more clearly differentiate between central auditory processing deficits and higher-order (cognitive and/or language) processing deficits.

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Olivocochlear Efferents: Anatomy, Physiology, Function, and the Measurement of Efferent Effects in Humans

Cited by 560 publications

References 128 publications

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

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

Contralateral Efferent Reflex Effects on Threshold and Suprathreshold Psychoacoustical Tuning Curves at Low and High Frequencies

Auditory Processing Disorders with and without Central Auditory Discrimination Deficits

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