Roles of the Contralateral Efferent Reflex in Hearing Demonstrated with Cochlear Implants

Lopez‐Poveda, Enrique A.; Eustaquio-Martín, Almudena; Stohl, Joshua S.; Wolford, Robert D.; Schatzer, Reinhold; Wilson, Blake S.

doi:10.1007/978-3-319-25474-6_12

Cited by 13 publications

(12 citation statements)

References 18 publications

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“…Some of these benefits are admittedly most obvious for this particular spatial configuration (SLNR) but still hold for other spatial configurations (not shown). Furthermore, we have shown elsewhere that similar effects occur for a speech source presented in competition with another speech source ( Lopez-Poveda 2015 ; Lopez-Poveda et al 2016 ).…”

Section: Resultssupporting

confidence: 67%

“…We have shown that for different input signals at the two ears, the MOC strategy enhances the interaural current difference in a frequency specific manner (Fig. 3 F; see also Lopez-Poveda et al 2016 ). Therefore, one might wonder whether the better intelligibility with the MOC strategy is the result of enhanced interaural current differences rather than or in combination with the other previously mentioned positive effects, particularly with the enhanced SNR in the better ear.…”

Section: Discussionmentioning

confidence: 74%

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A Binaural Cochlear Implant Sound Coding Strategy Inspired by the Contralateral Medial Olivocochlear Reflex

et al. 2016

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Objectives:In natural hearing, cochlear mechanical compression is dynamically adjusted via the efferent medial olivocochlear reflex (MOCR). These adjustments probably help understanding speech in noisy environments and are not available to the users of current cochlear implants (CIs). The aims of the present study are to: (1) present a binaural CI sound processing strategy inspired by the control of cochlear compression provided by the contralateral MOCR in natural hearing; and (2) assess the benefits of the new strategy for understanding speech presented in competition with steady noise with a speech-like spectrum in various spatial configurations of the speech and noise sources.Design: Pairs of CI sound processors (one per ear) were constructed to mimic or not mimic the effects of the contralateral MOCR on compression. For the nonmimicking condition (standard strategy or STD), the two processors in a pair functioned similarly to standard clinical processors (i.e., with fixed back-end compression and independently of each other). When configured to mimic the effects of the MOCR (MOC strategy), the two processors communicated with each other and the amount of backend compression in a given frequency channel of each processor in the pair decreased/increased dynamically (so that output levels dropped/ increased) with increases/decreases in the output energy from the corresponding frequency channel in the contralateral processor. Speech reception thresholds in speech-shaped noise were measured for 3 bilateral CI users and 2 single-sided deaf unilateral CI users. Thresholds were compared for the STD and MOC strategies in unilateral and bilateral listening conditions and for three spatial configurations of the speech and noise sources in simulated free-field conditions: speech and noise sources colocated in front of the listener, speech on the left ear with noise in front of the listener, and speech on the left ear with noise on the right ear. In both bilateral and unilateral listening, the electrical stimulus delivered to the test ear(s) was always calculated as if the listeners were wearing bilateral processors. Results:In both unilateral and bilateral listening conditions, mean speech reception thresholds were comparable with the two strategies for colocated speech and noise sources, but were at least 2 dB lower (better) with the MOC than with the STD strategy for spatially separated speech and noise sources. In unilateral listening conditions, mean thresholds improved with increasing the spatial separation between the speech and noise sources regardless of the strategy but the improvement was significantly greater with the MOC strategy. In bilateral listening conditions, thresholds improved significantly with increasing the speech-noise spatial separation only with the MOC strategy. Conclusions:The MOC strategy (1) significantly improved the intelligibility of speech presented in competition with a spatially separated noise source, both in unilateral and bilateral listening conditions; (2) produced significant sp...

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Section: Resultssupporting

confidence: 67%

Section: Discussionmentioning

confidence: 74%

A Binaural Cochlear Implant Sound Coding Strategy Inspired by the Contralateral Medial Olivocochlear Reflex

et al. 2016

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“…Since the comparison of interaural signals is essential to accurate sound localization (Seebacher et al, 2019;Zirn et al, 2019), a delicate calibration between the signals received from the two ears must be maintained. Moreover, the efferent architecture has been shown to have a significant function in the "cocktail party effect," which refers to the ability to parse one particular auditory stream from a complex acoustic environment (Giraud et al, 1997;Kumar and Vanaja, 2004;Kim et al, 2006;Andéol et al, 2011;Smith and Keil, 2015;Lopez-Poveda et al, 2016).…”

Section: Significance Statementmentioning

confidence: 99%

Effects of Efferent Activity on Hair Bundle Mechanics

Lin

Bozovic

2020

J. Neurosci.

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Hair cells in both the auditory and vestibular systems receive efferent innervation. A number of prior studies have indicated that efferent regulation serves to diminish the overall sensitivity of the auditory system. The efferent pathway is believed to affect the sensitivity and frequency selectivity of the hair cell by modulating its membrane potential. However, its effect on the mechanical response of the hair cell has not been established. We explored how stimulation of the efferent neurons affects the mechanical responsiveness of an individual hair bundle. We tested this effect on in vitro preparations of hair cells in the sacculi of American bullfrogs of both genders. Efferent stimulation routinely resulted in an immediate increase of the frequency of hair bundle spontaneous oscillations for the duration of the stimulus. Enlarging the stimulus amplitude and pulse length, or conversely, decreasing the interpulse interval led to oscillation suppression. Additionally, we tested the effects of efference on the hair bundle response to mechanical stimulation. The receptive field maps of hair cells undergoing efferent actuation demonstrated an overall desensitization with respect to those of unstimulated cells.

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“…As a result, the users of cochlear implants lack MOC efferent effects but may have the effects of LOC efferents. Therefore, insights into the roles of olivocochlear efferents in hearing may be gained by comparing auditory performance by normal-hearing individuals with that of cochlear implant users ( 199 ). In addition, cochlear implants allow unique control over the electrical stimulation used to evoke auditory sensations.…”

Section: Open Issues and Outlookmentioning

confidence: 99%

Olivocochlear Efferents in Animals and Humans: From Anatomy to Clinical Relevance

Lopez‐Poveda

2018

Front. Neurol.

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103

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Olivocochlear efferents allow the central auditory system to adjust the functioning of the inner ear during active and passive listening. While many aspects of efferent anatomy, physiology and function are well established, others remain controversial. This article reviews the current knowledge on olivocochlear efferents, with emphasis on human medial efferents. The review covers (1) the anatomy and physiology of olivocochlear efferents in animals; (2) the methods used for investigating this auditory feedback system in humans, their limitations and best practices; (3) the characteristics of medial-olivocochlear efferents in humans, with a critical analysis of some discrepancies across human studies and between animal and human studies; (4) the possible roles of olivocochlear efferents in hearing, discussing the evidence in favor and against their role in facilitating the detection of signals in noise and in protecting the auditory system from excessive acoustic stimulation; and (5) the emerging association between abnormal olivocochlear efferent function and several health conditions. Finally, we summarize some open issues and introduce promising approaches for investigating the roles of efferents in human hearing using cochlear implants.

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Roles of the Contralateral Efferent Reflex in Hearing Demonstrated with Cochlear Implants

Cited by 13 publications

References 18 publications

A Binaural Cochlear Implant Sound Coding Strategy Inspired by the Contralateral Medial Olivocochlear Reflex

A Binaural Cochlear Implant Sound Coding Strategy Inspired by the Contralateral Medial Olivocochlear Reflex

Effects of Efferent Activity on Hair Bundle Mechanics

Olivocochlear Efferents in Animals and Humans: From Anatomy to Clinical Relevance

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