Changes in Endolymphatic Potential and Crossed Olivocochlear Bundle Stimulation Alter Cochlear Mechanics

Mountain, David C.

doi:10.1126/science.7414321

Cited by 432 publications

(150 citation statements)

References 12 publications

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“…MOC influence on cochlear mechanics may be noninvasively, though indirectly, explored via measurement of otoacoustic emissions (OAEs) (Mountain 1980;Siegel and Kim 1982). OAEs are sounds recorded in the ear canal (Kemp 1978) that originate as a by-product of cochlear amplification and are sensitive indicators of OHC function.…”

Section: Introductionmentioning

confidence: 99%

Effects of Contralateral Acoustic Stimulation on Spontaneous Otoacoustic Emissions and Hearing Threshold Fine Structure

Dewey

Lee

Dhar

2014

JARO

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Medial olivocochlear (MOC) influence on cochlear mechanics can be noninvasively, albeit indirectly, explored via the effects of contralateral acoustic stimulation (CAS) on otoacoustic emissions. CASmediated effects are particularly pronounced for spontaneous otoacoustic emissions (SOAEs), which are typically reduced in amplitude and shifted upward in frequency by CAS. We investigated whether similar frequency shifts and magnitude reductions were observed behaviorally in the fine structure of puretone hearing thresholds, a phenomenon thought to share a common underlying mechanism with SOAEs. In normal-hearing listeners, fine-resolution thresholds were obtained over a narrow frequency range centered on the frequency of an SOAE, both in the absence and presence of 60-dB SPL broadband CAS. While CAS shifted threshold fine structure patterns and SOAEs upward in frequency by a comparable amount, little reduction in the presence or depth of fine structure was observed at frequencies near those of SOAEs. In fact, CAS typically improved thresholds, particularly at threshold minima, and increased fine structure depth when reductions in the amplitude of the associated SOAE were less than 10 dB. Additional measurements made at frequencies distant from SOAEs, or near SOAEs that were more dramatically reduced in amplitude by the CAS, revealed that CAS tended to elevate thresholds and reduce threshold fine structure depth. The results suggest that threshold fine structure is sensitive to MOC-mediated changes in cochlear gain, but that SOAEs complicate the interpretation of threshold measurements at nearby frequencies, perhaps due to masking or other interference effects. Both threshold fine structure and SOAEs may be significant sources of intersubject and intrasubject variability in psychoacoustic investigations of MOC function.

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Section: Introductionmentioning

confidence: 99%

Effects of Contralateral Acoustic Stimulation on Spontaneous Otoacoustic Emissions and Hearing Threshold Fine Structure

Dewey

Lee

Dhar

2014

JARO

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“…As MOC fibers directly innervate OHCs, their activity modifies the input impedance and membrane potential of OHCs (Housley and Ashmore 1991), affecting the mechanical feedback that they provide to basilar membrane motion (Mountain 1980;Siegel and Kim 1982;Murugasu and Russell 1996;Cooper and Guinan 2003). These changes reduce the cochlear-amplifier gain, producing a decrease in auditory-nerve compound action potentials (CAP) and an increase in cochlear microphonics (CM) amplitudes that reflects a higher voltage drop caused by the increase of current flow through OHCs and the cochlear circuit .…”

Section: Introductionmentioning

confidence: 99%

Effects of Electrical Stimulation of Olivocochlear Fibers in Cochlear Potentials in the Chinchilla

Elgueda

Délano

Robles

2011

JARO

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The mammalian cochlea has two types of sensory cells; inner hair cells, which receive auditory-nerve afferent innervation, and outer hair cells, innervated by efferent axons of the medial olivocochlear (MOC) system. The role of the MOC system in hearing is still controversial. Recently, by recording cochlear potentials in behaving chinchillas, we suggested that one of the possible functions of the efferent system is to reduce cochlear sensitivity during attention to other sensory modalities (Delano et al. in J Neurosci 27:4146-4153, 2007). However, in spite of these compelling results, the physiological effects of electrical MOC activation on cochlear potentials have not been described in detail in chinchillas. The main objective of the present work was to describe these efferent effects in the chinchilla, comparing them with those in other species and in behavioral experiments. We activated the MOC efferent axons in chinchillas with sectioned middle-ear muscles by applying current pulses at the fourth-ventricle floor. Auditory-nerve compound action potentials (CAP) and cochlear microphonics (CM) were acquired in response to clicks and tones of several frequencies, using a round-window electrode. Electrical efferent stimulation produced CAP amplitude suppressions reaching up to 11 dB. They were higher for low to moderate sound levels. Additionally, CM amplitude increments were found, the largest (≤ 2.5 dB) for low intensity tones. CAP suppression was present at all stimulus frequencies, but was greatest for 2 kHz. CM increments were highest for low-frequency tones, and almost absent at high frequencies. We conclude that the effect obtained in chinchilla is similar to but smaller than that observed in cats, and that the effects seen in awake chinchillas, albeit different in magnitude, are consistent with the activation of efferent fibers.

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“…These length changes are one likely source of acoustically evoked otoacoustic emissions (Kemp 1978;Kim 1980;Mountain 1980). Intracochlear AC stimulation produces sound in the ear canal as electrically evoked otoacoustic emissions (EEOAE) (Hubbard and Mountain 1983;Mountain and Hubbard 1989;Murata et al 1991;Ren and Nuttall 1995).…”

Section: Introductionmentioning

confidence: 99%

Long-Term Effects of Acoustic Trauma on Electrically Evoked Otoacoustic Emission

Hälsey

Fegelman

Raphael

et al. 2005

JARO

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Electrically evoked otoacoustic emissions (EEOAEs) are sounds measured in the ear canal when alternating current (AC) stimulation is passed into the cochlea. These sounds are attributed to the motile responses of outer hair cells (OHCs). The EEOAE has characteristic amplitude, phase, and fine structure. Multicomponent analysis of the EEOAE shows short (SDC) and long delay components (LDC) that are thought to originate from OHCs near the AC stimulating site and from OHCs at more remote locations, respectively. We measured the effects of various loud noise exposures on the EEOAE and the cochlear whole-nerve action potential (CAP) in animals chronically implanted with a scala tympani electrode. Noise exposures that produced permanent (PTS) or temporary threshold shifts (TTS) were associated with frequency-specific changes in CAP thresholds, EEOAE fine structure, and reductions in the amplitude of the LDC. A frequent observation in this study was an increase in the overall EEOAE amplitude after the noise exposure. The increase was correlated with increased SDC amplitude. The SDC was present in animals chemically treated with ototoxic drugs and mechanical damage to the cochlea. The SDC was eliminated after disarticulation of the ossicular chain. The presence of EEOAE fine structure in the postexposure response is an indicator of TTS in advance of CAP recovery. The results suggest that the EEOAE might be used to differentiate the mechanisms associated with TTS and PTS.

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Changes in Endolymphatic Potential and Crossed Olivocochlear Bundle Stimulation Alter Cochlear Mechanics

Cited by 432 publications

References 12 publications

Effects of Contralateral Acoustic Stimulation on Spontaneous Otoacoustic Emissions and Hearing Threshold Fine Structure

Effects of Contralateral Acoustic Stimulation on Spontaneous Otoacoustic Emissions and Hearing Threshold Fine Structure

Effects of Electrical Stimulation of Olivocochlear Fibers in Cochlear Potentials in the Chinchilla

Long-Term Effects of Acoustic Trauma on Electrically Evoked Otoacoustic Emission

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