scholarly journals Frequency tuning of the contralateral medial olivocochlear reflex in humans

2012 ◽  
Vol 108 (1) ◽  
pp. 25-30 ◽  
Author(s):  
Wei Zhao ◽  
Sumitrajit Dhar
Keyword(s):  
Otoacoustic Emissions ◽  
Frequency Tuning ◽  
Acoustic Trauma ◽  
Fixed Frequency ◽  
Sound Perception ◽  
Spontaneous Otoacoustic Emissions ◽  
Functional Roles ◽  
Cochlear Gain ◽  
Medial Olivocochlear

Activation of the medial olivocochlear (MOC) efferents attenuates cochlear gain and reduces the amplitudes of mechanical, electrical, and neural cochlear outputs. The functional roles of the MOC efferents are not fully understood, especially in humans, despite postulations that they are involved in protection against acoustic trauma, facilitation of transient-sound perception, etc. Delineating the frequency tuning properties of the MOC efferents would provide critical evidence to support or refute these postulated functional roles. By utilizing spontaneous otoacoustic emissions (SOAEs), a cochlear measure sensitive to MOC modulation, we systematically demonstrate in humans that the contralateral MOC reflex is tuned to a fixed frequency band between 500 and 1,000 Hz independent of SOAE frequency. Our results question the role of the MOC reflex in protection against acoustic trauma or facilitation of transient-sound perception.

The Role of the Medial Olivocochlear Reflex in Psychophysical Masking and Intensity Resolution in Humans: A Review

2021 ◽  
Author(s):  
Skyler G. Jennings
Keyword(s):  
Otoacoustic Emissions ◽  
Acoustic Stimulation ◽  
Forward Masking ◽  
Frequency Resolution ◽  
Vestibular Neurectomy ◽  
Contralateral Acoustic Stimulation ◽  
Cochlear Gain ◽  
Medial Olivocochlear ◽  
Intensity Resolution

This review addresses the putative role of the medial olivocochlear (MOC) reflex on psychophysical masking and intensity resolution in humans. A framework for interpreting psychophysical results in terms of the expected influenced of the MOC reflex is introduced. This framework is used to review the effects of a precursor or contralateral acoustic stimulation on 1) simultaneous masking of brief tones, 2) behavioral estimates of cochlear gain and frequency resolution in forward masking, 3) the build-up and decay of forward masking, and 4) measures of intensity resolution. Support, or lack thereof, for a role of the MOC reflex in psychophysical perception is discussed in terms of studies on estimates of MOC strength from otoacoustic emissions and the effects of resection of the olivocochlear bundle in patients with vestibular neurectomy. Novel, innovative approaches are needed to resolve the dissatisfying conclusion that current results are unable to definitively confirm or refute the role of the MOC reflex in masking and intensity resolution.

scholarly journals Reflex Control of the Human Inner Ear: A Half-Octave Offset in Medial Efferent Feedback That Is Consistent With an Efferent Role in the Control of Masking

2009 ◽  
Vol 101 (3) ◽  
pp. 1394-1406 ◽  
Author(s):  
Watjana Lilaonitkul ◽  
John J. Guinan
Keyword(s):  
Otoacoustic Emissions ◽  
High Sensitivity ◽  
Outer Hair Cells ◽  
Tuning Curves ◽  
Cochlear Amplification ◽  
Inhibitory Feedback ◽  
Probe Frequency ◽  
Medial Olivocochlear ◽  
Human Inner Ear

The high sensitivity and frequency selectivity of the mammalian cochlea is due to amplification produced by outer hair cells (OHCs) and controlled by medial olivocochlear (MOC) efferents. Data from animals led to the view that MOC fibers provide frequency-specific inhibitory feedback; however, these studies did not measure intact MOC reflexes. To test whether MOC inhibition is primarily at the frequency that elicits the MOC activity, acoustically elicited MOC effects were quantified in humans by the change in otoacoustic emissions produced by 60-dB SPL tone and half-octave-band noise elicitors at different frequencies relative to a 40-dB SPL, 1-kHz probe tone. On average, all elicitors produced MOC effects that were skewed (elicitor frequencies -1 octave below the probe produced larger effects than those -1 octave above). The largest MOC effects were from elicitors below the probe frequency for contra- and bilateral elicitors but were from elicitors centered at the probe frequency for ipsilateral elicitors. Typically, ipsilateral elicitors produced larger effects than contralateral elicitors and bilateral elicitors produced effects near the ipsi+contra sum. Elicitors at levels down to 30-dB SPL produced similar patterns. Tuning curves (TCs) interpolated from these data were V-shaped with Q10s ∼2. These are sharper than MOC-fiber TCs found near 1 kHz in cats and guinea pigs. Because cochlear amplification is skewed (more below the best frequency of a cochlear region), these data are consistent with an anti-masking role of MOC efferents that reduces masking by reducing the cochlear amplification seen at 1 kHz.

scholarly journals Frequency tuning of medial-olivocochlear-efferent acoustic reflexes in humans as functions of probe frequency

2012 ◽  
Vol 107 (6) ◽  
pp. 1598-1611 ◽  
Author(s):  
Watjana Lilaonitkul ◽  
John J. Guinan
Keyword(s):  
Otoacoustic Emissions ◽  
Frequency Tuning ◽  
Stimulus Frequency ◽  
Phase Changes ◽  
Acoustic Reflex ◽  
Wide Range ◽  
Acoustic Reflexes ◽  
Specific Feedback ◽  
Stimulus Frequency Otoacoustic Emissions ◽  
Medial Olivocochlear

The medial-olivocochlear (MOC) acoustic reflex is thought to provide frequency-specific feedback that adjusts the gain of cochlear amplification, but little is known about how frequency specific the reflex actually is. We measured human MOC tuning through changes in stimulus frequency otoacoustic emissions (SFOAEs) from 40-dB-SPL tones at probe frequencies ( fps) near 0.5, 1.0, and 4.0 kHz. MOC activity was elicited by 60-dB-SPL ipsilateral, contralateral, or bilateral tones or half-octave noise bands, with elicitor frequency ( fe) varied in half-octave steps. Tone and noise elicitors produced similar results. At all probe frequencies, SFOAE changes were produced by a wide range of elicitor frequencies with elicitor frequencies near 0.7–2.0 kHz being particularly effective. MOC-induced changes in SFOAE magnitude and SFOAE phase were surprisingly different functions of fe: magnitude inhibition largest for fe close to fp, phase change largest for fe remote from fp. The metric ΔSFOAE, which combines both magnitude and phase changes, provided the best match to reported (cat) MOC neural inhibition. Ipsilateral and contralateral MOC reflexes often showed dramatic differences in plots of MOC effect vs. elicitor frequency, indicating that the contralateral reflex does not give an accurate picture of ipsilateral-reflex properties. These differences in MOC effects appear to imply that ipsilateral and contralateral reflexes have different actions in the cochlea. The implication of these results for MOC function, cochlear mechanics, and the production of SFOAEs are discussed.

scholarly journals A Critique of the Critical Cochlea: Hopf—a Bifurcation—Is Better Than None

2010 ◽  
Vol 104 (3) ◽  
pp. 1219-1229 ◽  
Author(s):  
A. J. Hudspeth ◽  
Frank Jülicher ◽  
Pascal Martin
Keyword(s):  
Otoacoustic Emissions ◽  
Dynamic Range ◽  
Dynamic Instability ◽  
Frequency Tuning ◽  
Active Process ◽  
Cochlear Function ◽  
Spontaneous Otoacoustic Emissions ◽  
Distortion Products ◽  
Highly Nonlinear ◽  
Critical Oscillation

The sense of hearing achieves its striking sensitivity, frequency selectivity, and dynamic range through an active process mediated by the inner ear's mechanoreceptive hair cells. Although the active process renders hearing highly nonlinear and produces a wealth of complex behaviors, these various characteristics may be understood as consequences of a simple phenomenon: the Hopf bifurcation. Any critical oscillator operating near this dynamic instability manifests the properties demonstrated for hearing: amplification with a specific form of compressive nonlinearity and frequency tuning whose sharpness depends on the degree of amplification. Critical oscillation also explains spontaneous otoacoustic emissions as well as the spectrum and level dependence of the ear's distortion products. Although this has not been realized, several valuable theories of cochlear function have achieved their success by incorporating critical oscillators.

scholarly journals What is the role of the medial olivocochlear system in speech-in-noise processing?

2012 ◽  
Vol 107 (5) ◽  
pp. 1301-1312 ◽  
Author(s):  
Jessica de Boer ◽  
A. Roger D. Thornton ◽  
Katrin Krumbholz
Keyword(s):  
Otoacoustic Emissions ◽  
Noise Masking ◽  
Speech In Noise ◽  
Olivocochlear System ◽  
Contralateral Suppression ◽  
Auditory Brain Stem ◽  
Medial Olivocochlear System ◽  
Masking Noise ◽  
Cochlear Gain ◽  
Medial Olivocochlear

The medial olivocochlear (MOC) bundle reduces the gain of the cochlear amplifier through reflexive activation by sound. Physiological results indicate that MOC-induced reduction in cochlear gain can enhance the response to signals when presented in masking noise. Some previous studies suggest that this “antimasking” effect of the MOC system plays a role in speech-in-noise perception. The present study set out to reinvestigate this hypothesis by correlating measures of MOC activity and speech-in-noise processing across a group of normal-hearing participants. MOC activity was measured using contralateral suppression of otoacoustic emissions (OAEs), and speech-in-noise processing was measured by measuring the effect of noise masking on performance in a consonant-vowel (CV) discrimination task and on auditory brain stem responses evoked by a CV syllable. Whereas there was a significant correlation between OAE suppression and both measures of speech-in-noise processing, the direction of this correlation was opposite to that predicted by the antimasking hypothesis, in that individuals with stronger OAE suppression tended to show greater noise-masking effects on CV processing. The current results indicate that reflexive MOC activation is not always beneficial to speech-in-noise processing. We propose an alternative to the antimasking hypothesis, whereby the MOC system benefits speech-in-noise processing through dynamic (e.g., attention- and experience-dependent), rather than reflexive, control of cochlear gain.

scholarly journals Supra-threshold psychoacoustics and envelope-following response relations: normal-hearing, synaptopathy and cochlear gain loss

2018 ◽  
Author(s):  
Sarah Verhulst ◽  
Frauke Ernst ◽  
Markus Garrett ◽  
Viacheslav Vasilkov
Keyword(s):  
Minor Role ◽  
Sound Perception ◽  
Proxy Measure ◽  
Envelope Following Response ◽  
Cochlear Gain ◽  
Human Hearing ◽  
Gain Loss ◽  
A Minor ◽  
Direct Quantification

AbstractThe perceptual consequences of cochlear synaptopathy are presently not well understood as a direct quantification of synaptopathy is not possible in humans. To study its role for human hearing, recent studies have instead correlated changes in basic supra-threshold psychoacoustic tasks with individual differences in subcortical EEG responses, as a proxy measure for synaptopathy. It is not clear whether the reported missing relationships between the psychoacoustic quantities and the EEG are due to the adopted methods, or to a minor role of synaptopathy for sound perception. We address this topic by studying the theoretical relationship between subcortical EEG and psychoacoustic methods for different sensorineural hearing deficits.

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