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Hear Res. 2016 Feb;332:87-94. doi: 10.1016/j.heares.2015.12.010. Epub 2015 Dec 17.

Low-frequency sound exposure causes reversible long-term changes of cochlear transfer characteristics.

Author information

1
German Center for Vertigo and Balance Disorders (IFB), Grosshadern Medical Centre, University of Munich, 81377, Munich, Germany; Department of Otorhinolaryngology, Head and Neck Surgery, Grosshadern Medical Centre, University of Munich, 81377, Munich, Germany. Electronic address: markus.drexl@med.uni-muenchen.de.
2
Division of Neurobiology, Department Biology II, University of Munich, 82152, Martinsried, Germany.
3
University College London, Ear Institute, 332 Gray's Inn Rd, London, WC1X 8EE, United Kingdom.
4
German Center for Vertigo and Balance Disorders (IFB), Grosshadern Medical Centre, University of Munich, 81377, Munich, Germany; Department of Otorhinolaryngology, Head and Neck Surgery, Grosshadern Medical Centre, University of Munich, 81377, Munich, Germany.

Abstract

Intense, low-frequency sound presented to the mammalian cochlea induces temporary changes of cochlear sensitivity, for which the term 'Bounce' phenomenon has been coined. Typical manifestations are slow oscillations of hearing thresholds or the level of otoacoustic emissions. It has been suggested that these alterations are caused by changes of the mechano-electrical transducer transfer function of outer hair cells (OHCs). Shape estimates of this transfer function can be derived from low-frequency-biased distortion product otoacoustic emissions (DPOAE). Here, we tracked the transfer function estimates before and after triggering a cochlear Bounce. Specifically, cubic DPOAEs, modulated by a low-frequency biasing tone, were followed over time before and after induction of the cochlear Bounce. Most subjects showed slow, biphasic changes of the transfer function estimates after low-frequency sound exposure relative to the preceding control period. Our data show that the operating point changes biphasically on the transfer function with an initial shift away from the inflection point followed by a shift towards the inflection point before returning to baseline values. Changes in transfer function and operating point lasted for about 180 s. Our results are consistent with the hypothesis that intense, low-frequency sound disturbs regulatory mechanisms in OHCs. The homeostatic readjustment of these mechanisms after low-frequency offset is reflected in slow oscillations of the estimated transfer functions.

KEYWORDS:

Cochlea; Distortion product otoacoustic emission; Low-frequency sounds; Mechano-electrical transducer; Outer hair cells

PMID:
26706707
DOI:
10.1016/j.heares.2015.12.010
[Indexed for MEDLINE]

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