Changes in amplitude and phase of distortion-product otoacoustic emission fine-structure and separated components during efferent activation

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The Journal of the Acoustical Society of America (Impact Factor: 1.5). 04/2011; 129(4):2068-79. DOI: 10.1121/1.3543945
Source: PubMed


Medial olivocochlear (MOC) efferent fibers synapse directly on the outer hair cells (OHCs). Efferent activation evoked by contralateral acoustic stimulation (CAS) will affect OHC amplification and subsequent measures of distortion-product otoacoustic emissions (DPOAEs). The aim of this study was to investigate measures of total and separated DPOAEs during efferent activation. Efferent activation produces both suppression and enhancement of the total DPOAE level. Level enhancements occurred near fine-structure minima and were associated with consistent MOC evoked upward shifts in DPOAE fine-structure frequency. Examination of the phase of the separated components revealed that frequency shifts stemmed from increasing phase leads of the reflection component during CAS, while the generator component phase was nearly invariant. Separation of the two DPOAE components responsible for the fine-structure revealed more consistent reduction of the levels of both components. Using vector subtraction (which takes into account both level and phase) to estimate the changes in the unseparated DPOAE provided consistent evidence of DPOAE suppression. Including phase information provided a more sensitive, valid and consistent estimate of CAS function even if one does not know the position of the DPOAE in the fine-structure.

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Available from: Glenis Raewyn Long, Oct 07, 2015
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    • "The LSF minimization routine steps through the recording, creating a band-pass filter that changes center frequency as a function of DPOAE (see Long et al., 2008; for additional details). The composite DPOAE is estimated in a separate LSF analysis than the separated components, with the bandwidth of the filter used for the LSF analyses varied depending on the DPOAE component being estimated (cf, Long and Talmadge, 1997; Long et al., 2008; Henin et al., 2011b, 2014). Based on the sampling rate of 44,100 samples/s, estimates of composite DPOAE were obtained using a wideband analysis (n ¼ 2756, nstep ¼ 275, 16 Hz for 1 s/octave; n ¼ 5512, nstep ¼ 551, 8 Hz for 2 s/octave). "
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    ABSTRACT: Distortion product otoacoustic emissions (DPOAE) in newborns and adults were evoked by sweeping primaries up and down in frequency at 1 s/octave. Sweeping up and down in frequency resulted in changes in the amplitude vs. frequency functions of the composite DPOAE and its two major components. In addition, DPOAE component phases differed slightly between the up- and down-swept conditions. The changes in amplitude vs. frequency functions were quantified using a covariate correlation technique, yielding single-valued estimates of the magnitude of the frequency changes. Separate analyses were performed for the entire DPOAE frequency range and split into low and high frequency ranges. There were consistent changes in newborn and adult composite DPOAEs and reflection components, but not generator components. Adults had significant frequency changes in the composite DPOAE for all frequency ranges and in the reflection component for the entire frequency range. Newborns had significant frequency change in the reflection component for all frequency ranges. Differences in frequency change between adults and newborns may stem from developmental changes in cochlear processing. Alignment of the component phase differences between the up- and down-swept conditions resulted in elimination of frequency-change in reconstructed composite DPOAEs. Copyright © 2015 Elsevier B.V. All rights reserved.
    Hearing research 08/2015; DOI:10.1016/j.heares.2015.08.012 · 2.97 Impact Factor
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    • "This implementation is basically limited by the necessity of applying many discrete primary frequencies to get reliable DPOAE data. In literature (Sun, 2008; Henin et al., 2011), however, there are some suggestions for how to improve the DPOAE contralateral suppression measurement for clinical purposes to evaluate the MOC reflex effect. Also, the temporal recording of the f DP suppression may have made a contribution to the final data. "
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    ABSTRACT: The main purpose of this investigation was to measure the effect of contralateral acoustic stimulation (CAS) on distortion product otoacoustic emission (DPOAE) in twenty human ears, for a ratio of primary tones f(2)/f(1) = 1.22 and a wide frequency range of f(2) (1.4-9 kHz), for two intensity levels of primary tones (L-1 = 60 dB SPL; L-2 = 50 dB SPL and L-1 = 70 dB SPL; L-2 = 60 dB SPL) and two intensity levels of CAS (50 and 60 dB SPL). It was found that in the presence of CAS, in the majority of cases the DPOAE level decreased (suppression), but it might also increase (enhancement) or remain unchanged depending on the frequency. The mean suppression level of the component of the frequency f(DP) = 2f(1) - f(2) might be approximated by a linearly decreasing function of the f(2) frequency of primary tones. The slope of this function was negative and increased with an increase of the contralateral stimulation level. The higher was the contralateral noise level the greater was the suppression. For the f(DP) level below about 15 dB SPL, suppression was observed in a substantial number of measurement cases (in about 85% of all measured cases on average). When the f(DP) level was higher than 15 dB SPL, only suppression (not enhancement) was observed.
    Archives of Acoustics 01/2014; 39(1):125-138. DOI:10.2478/aoa-2014-0013 · 0.57 Impact Factor
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    • "The complication of the DPOAE comprising a mixture of distortion-and reflection-source components may also have a bearing on the results (Abdala et al, 2010; Maison & Liberman, 2000; Muller et al, 2005; Sun, 2008). Henin et al (2011) "
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    ABSTRACT: Objective: To study whether a change in cochlear tuning, measured using OAEs, could be detected due to contralateral activation of the efferent system using broadband noise. Design: Cochlear tuning measures based on SFOAE phase gradients and SFOAE-2TS ܁Q܀ were used to test this hypothesis. SFOAE magnitude and phase gradient were measured using a pure-tone sweep from 1248 to 2496 Hz at 50 dB SPL. 2TS curves of SFOAE were recorded with a suppressor frequency swept from 1120 to 2080 Hz at 50 dB SPL. DPOAE f2-sweep phase gradient was also obtained to allow comparisons with the literature. All three assays were performed across with- and no-CAS conditions. Study sample: Twenty-two young, normal-hearing adults. Results: CAS did not produce a statistically significant change in the tuning metric in any of the OAE methods used, despite producing significant reductions in the OAE magnitude. Conclusion: It is unknown whether this insensitivity to CAS is due to an insensitivity of these three measures to cochlear mechanical tuning. The results suggest that any changes in tuning induced by CAS that may occur are small and difficult to detect using the OAE measurement paradigms used here.
    International journal of audiology 08/2012; 51(12). DOI:10.3109/14992027.2012.709641 · 1.84 Impact Factor
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