Amplitude modulation of DPOAEs by acoustic stimulation of the contralateral ear

Harrison, Robert V.; Sharma, Anu; Brown, Thomas; Jiwani, Salima; James, Adrian L.

doi:10.1080/00016480701784965

Cited by 18 publications

(18 citation statements)

References 14 publications

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“…The functional status of MOC efferents has been noninvasively assayed in many other mammals through measurement of the MOC reflexes in which the amplitude of otoacoustic emissions are modulated upon sound presentation to the contralateral or ipsilateral ear (Boyev et al 2002;Harrison et al 2008;Henin et al 2011;Moulin et al 1993). However, reduced otoacoustic emission amplitudes following contralateral acoustic stimulation (CAS) in mice have only been reported by one group Zhu et al 2007), and the role of the MOC system rather than other feedback systems such as the middle ear muscle reflex has not been directly demonstrated.…”

Section: Introductionmentioning

confidence: 99%

Sound-Evoked Olivocochlear Activation in Unanesthetized Mice

Chambers

Hancock

Maison

et al. 2011

JARO

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Genetic tools available for the mouse make it a powerful model to study the modulation of cochlear function by descending control systems. Suppression of distortion product otoacoustic emission (DPOAE) amplitude by contralateral acoustic stimulation (CAS) provides a robust tool for noninvasively monitoring the strength of descending modulation, yet investigations in mice have been performed infrequently and only under anesthesia, a condition likely to reduce olivocochlear activation. Here, we characterize the contralateral olivocochlear reflex in the alert, unanesthetized mouse. Head-fixed mice were restrained between two closed acoustic systems, while an artifact rejection protocol minimized contamination from self-generated sounds and movements. In mice anesthetized with pentobarbital, ketamine or urethane, CAS at 80 dB SPL evoked, on average, a G1-dB change in DPOAE amplitude. In contrast, the mean CASinduced DPOAE suppression in unanesthetized mice was nearly 8 dB. Experiments in mice with targeted deletion of the α9 subunit of the nicotinic acetylcholine receptor confirmed the contribution of the medial olivocochlear efferents to this phenomenon. These findings demonstrate the utility of the CAS assay in the unanesthetized mouse and highlight the adverse effects of anesthesia when probing the functional status of descending control pathways within the auditory system.

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Section: Introductionmentioning

confidence: 99%

Sound-Evoked Olivocochlear Activation in Unanesthetized Mice

Chambers

Hancock

Maison

et al. 2011

JARO

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“…A note on terminology: the modulation of DPOAE by the MOCS is commonly referred to as 'suppression' when it results in a reduction in DPOAE level [Abdala, 2001;James et al, 2002;Jacobson et al, 2003;James et al, 2005;James, 2011]. Considering that the MOCS can both suppress and enhance DPOAE, the effects are sometimes referred to as 'modulations' [Harrison et al, 2008]. However, Guinan [2010] recommended that as these reductions are due to medial olivocochlear synaptic effects rather than two-tone suppression, the reductions are more aptly referred to as 'inhibitions'.…”

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confidence: 99%

Separating the Contributions of Olivocochlear and Middle Ear Muscle Reflexes in Modulation of Distortion Product Otoacoustic Emission Levels

2013

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Objectives: Mediated by the medial olivocochlear system (MOCS), distortion product otoacoustic emission (DPOAE) levels are reduced by presentation of contralateral acoustic stimuli. Such acoustic signals can also evoke a middle ear muscle reflex (MEMR) that also attenuates recorded DPOAE levels. Our aim is to clearly differentiate these two inhibitory mechanisms and to analyze each separately, perhaps allowing the development of novel tests of hearing function. Methods: DPOAE were recorded in real time from chinchillas with normal auditory brainstem response thresholds and middle ear function. Amplitude reduction and its onset latency caused by contralateral presentation of intermittent narrow-band noise (NBN) were measured. Stapedius and tensor tympani muscle tendons were divided without disturbing the ossicular chain, and DPOAE testing was repeated. Results: Peak reduction of (2f₁ - f₂) DPOAE levels occurred when the center frequency of contralateral NBN approximated the primary tone f₂, indicating an f₂-frequency-specific response. For a 4.5-kHz centered NBN, DPOAE (f₂ = 4.4 kHz) inhibition was 0.1 dB (p < 0.001). This response remained present after tendon division, consistent with an MOCS origin. Low-frequency NBN (center frequency: 0.5 kHz) reduced otoacoustic emission levels (0.1 dB, p < 0.001) across a wide range of DPOAE frequencies. This low-frequency response was abolished by division of the middle ear muscle tendons, clearly indicating MEMR involvement. Conclusions: Following middle ear muscle tendon division, DPOAE inhibition by contralateral stimuli approximating the primary tone f₂ persists, whereas responses evoked by lower contralateral frequencies are abolished. This distinguishes the different roles of the MOCS (f₂ frequency specific) and MEMR (low frequency only) in contralateral modulation of DPOAE. This analysis helps clarify the pathways involved in an objective test that might have clinical benefit in the testing of neonates.

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“…However, efferent reflex is intrinsically slow with time constants more than 0.15 s (Backus and Guinan, 2006). Measuring DPOAE amplitude fluctuations induced by randomly varying the noise amplitude presented in the contra-lateral ear, the highest modulation rate in the DPOAE is found to be less than 10 Hz (Harrison et al, 2008). The present study shows that the CDT amplitude can follow the envelope of a 32-Hz AM tone.…”

Section: Reduction In Cdt Magnitudementioning

confidence: 84%

Behaviors of cubic distortion product otoacoustic emissions evoked by amplitude modulated tones

Bian

Chen

2011

The Journal of the Acoustical Society of America

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Distortion product otoacoustic emissions (DPOAEs) were measured using sinusoidal amplitude modulation (AM) tones. When one of the primary stimuli (f(1) or f(2), f(1) < f(2)) was amplitude modulated, a series of changes in the cubic difference tone (CDT) were observed. In the frequency domain, multiple sidebands were present around the CDT and their sizes grew with the modulation depth of the AM stimulus. In the time domain, the CDT showed different modulation patterns between two major signal conditions: the AM tone was used as the f(1) or the f(2). The CDT amplitude followed the AM tone when the f(1) was amplitude modulated. However, when the AM tone acted as the f(2), the CDT showed a more complex modulation pattern with a notch present at the AM tone peak. The relatively linear dependence of CDT on f(1) and the nonlinear relation with f(2) can be explained with a variable gain-control model representing hair cell functions at the DPOAE generation site. It is likely that processing of AM signals at a particular cochlear location depends on whether the hair cells are tuned to the frequency of the carrier. Nonlinear modulation is related to on-frequency carriers and off-frequency carriers are processed relatively linearly.

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Amplitude modulation of DPOAEs by acoustic stimulation of the contralateral ear

Cited by 18 publications

References 14 publications

Sound-Evoked Olivocochlear Activation in Unanesthetized Mice

Sound-Evoked Olivocochlear Activation in Unanesthetized Mice

Separating the Contributions of Olivocochlear and Middle Ear Muscle Reflexes in Modulation of Distortion Product Otoacoustic Emission Levels

Behaviors of cubic distortion product otoacoustic emissions evoked by amplitude modulated tones

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