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 Increased contralateral suppression of otoacoustic emissions indicates a hyperresponsive medial olivocochlear system in humans with tinnitus and hyperacusis

2014 ◽  
Vol 112 (12) ◽  
pp. 3197-3208 ◽  
Author(s):  
Inge M. Knudson ◽  
Christopher A. Shera ◽  
Jennifer R. Melcher
Keyword(s):  
Brain Stem ◽  
Cochlear Nucleus ◽  
Otoacoustic Emissions ◽  
Sound Level ◽  
Broadband Noise ◽  
Neural Pathways ◽  
Distortion Product ◽  
Olivocochlear System ◽  
Contralateral Suppression ◽  
Medial Olivocochlear

Atypical medial olivocochlear (MOC) feedback from brain stem to cochlea has been proposed to play a role in tinnitus, but even well-constructed tests of this idea have yielded inconsistent results. In the present study, it was hypothesized that low sound tolerance (mild to moderate hyperacusis), which can accompany tinnitus or occur on its own, might contribute to the inconsistency. Sound-level tolerance (SLT) was assessed in subjects (all men) with clinically normal or near-normal thresholds to form threshold-, age-, and sex-matched groups: 1) no tinnitus/high SLT, 2) no tinnitus/low SLT, 3) tinnitus/high SLT, and 4) tinnitus/low SLT. MOC function was measured from the ear canal as the change in magnitude of distortion-product otoacoustic emissions (DPOAE) elicited by broadband noise presented to the contralateral ear. The noise reduced DPOAE magnitude in all groups (“contralateral suppression”), but significantly more reduction occurred in groups with tinnitus and/or low SLT, indicating hyperresponsiveness of the MOC system compared with the group with no tinnitus/high SLT. The results suggest hyperresponsiveness of the interneurons of the MOC system residing in the cochlear nucleus and/or MOC neurons themselves. The present data, combined with previous human and animal data, indicate that neural pathways involving every major division of the cochlear nucleus manifest hyperactivity and/or hyperresponsiveness in tinnitus and/or low SLT. The overactivation may develop in each pathway separately. However, a more parsimonious hypothesis is that top-down neuromodulation is the driving force behind ubiquitous overactivation of the auditory brain stem and may correspond to attentional spotlighting on the auditory domain in tinnitus and hyperacusis.

Contralateral Suppression of Otoacoustic Emissions: An Index of the Function of the Medial Olivocochlear System

1994 ◽  
Vol 110 (1) ◽  
pp. 3-21 ◽  
Author(s):  
Charles I. Berlin ◽  
Linda J. Hood ◽  
Annette Hurley ◽  
Han Wen
Keyword(s):  
Hair Cell ◽  
Middle Ear ◽  
Otoacoustic Emissions ◽  
Outer Hair Cell ◽  
Microstructural Analysis ◽  
Nerve Fibers ◽  
Speech Comprehension ◽  
Unique Type ◽  
Olivocochlear System ◽  
Contralateral Suppression

We can now distinguish, in part, between nerve deafness and hair cell deafness through the use of otoacoustic emissions. We can also assess the efferent system by carefully quantifying the effects of contralateral stimulation on these same otoacoustic emissions. The suppression of transient evoked emissions by continuous contralateral white noise is an ostensibly small effect of 2 or 3 dB when studied over a 20-msec window. However, when subjected to microstructural analysis, the effect can exceed 6 to 8 dB in the zones from 10 to 20 msec after the stimulus has subsided. Temporal and spectral analyses reveal robust effects of contralateral lateral stimulation, although in any given normal subject it may be difficult to separate middle ear effects from efferent effects. Evidence is strong that the efferent effect is mediated in part by cholinergic — primarily nicotinic — receptors in the outer hair cell. However, a unique type of patient, who shows nearly normal pure-tone audiograms and absent ABRs, shows virtually no contralateral suppression of transient evoked emissions. Some other patients, with symptoms of Charcot-Marie-Tooth disease, may paradoxically show extremely poor audiograms, but perfectly normal evoked emissions along with absent contralateral suppression. The ABR, along with middle ear muscle reflexes and masking level differences, are all absent in these patients; we therefore think they have a disorder that desynchronizes most of their primary auditory nerve fibers and thereby disconnects them from any efferent activity or masking cancellation. The existence of such an auditory disorder, characterized by severe dysfunction in speech comprehension — especially when listening in noise—suggests that what appears to be a “central auditory imperception” might stem instead from a systemic peripheral primary neuropathy.

Noise and Medial Olivocochlear System in Humans

1991 ◽  
Vol 111 (2) ◽  
pp. 231-233 ◽  
Author(s):  
L. Collet ◽  
A. Morgon ◽  
E. Veuillet ◽  
M. Gartner
Keyword(s):  
Olivocochlear System ◽  
Medial Olivocochlear System ◽  
Medial Olivocochlear

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.

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