title: Responses of the Human Inner Ear to Low-Frequency Sound.
abstract: The perceptual insensitivity to low frequency (LF) sound in humans has led to an underestimation of the physiological impact of LF exposure on the inner ear. It is known, however, that intense, LF sound causes cyclic changes of indicators of inner ear function after LF stimulus offset, for which the term "Bounce" phenomenon has been coined.Here, we show that the mechanical amplification of hair cells (OHCs) is significantly affected after the presentation of LF sound. First, we show the Bounce phenomenon in slow level changes of quadratic, but not cubic, distortion product otoacoustic emissions (DPOAEs). Second, Bouncing in response to LF sound is seen in slow, oscillating frequency and correlated level changes of spontaneous otoacoustic emissions (SOAEs). Surprisingly, LF sound can induce new SOAEs which can persist for tens of seconds. Further, we show that the Bounce persists under free-field conditions, i.e. without an in-ear probe occluding the auditory meatus. Finally, we show that the Bounce is affected by contralateral acoustic stimulation synchronised to the ipsilateral LF sound. These findings clearly demonstrate that the origin of the Bounce lies in the modulation of cochlear amplifier gain. We conclude that activity changes of OHCs are the source of the Bounce, most likely caused by a temporary disturbance of OHC calcium homeostasis. In the light of these findings, the effects of long-duration, anthropogenic LF sound on the human inner ear require further research.
authors.affiliation: German Center for Vertigo and Balance Disorders (IFB), Department of Otorhinolaryngology, Head and Neck Surgery, Grosshadern Medical Centre, University of Munich, 81377, Munich, Germany. markus.drexl@med.uni-muenchen.de.
authors.forename: Markus
authors.initials: M
authors.lastname: Drexl
authors.affiliation: German Center for Vertigo and Balance Disorders (IFB), Department of Otorhinolaryngology, Head and Neck Surgery, Grosshadern Medical Centre, University of Munich, 81377, Munich, Germany.
authors.forename: Eike
authors.initials: E
authors.lastname: Krause
authors.affiliation: German Center for Vertigo and Balance Disorders (IFB), Department of Otorhinolaryngology, Head and Neck Surgery, Grosshadern Medical Centre, University of Munich, 81377, Munich, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Gürkov
authors.affiliation: Division of Neurobiology, Dept. Biology II, University of Munich, 82152, Martinsried, Germany.
authors.forename: Lutz
authors.initials: L
authors.lastname: Wiegrebe
mesh_terms: D000161:Acoustic Stimulation; D000328:Adult; D002118:Calcium / Q000378:metabolism; D007758:Ear, Inner / Q000502:physiology*; D018072:Hair Cells, Auditory, Outer / Q000502:physiology*; D006706:Homeostasis; D006801:Humans; D017084:Otoacoustic Emissions, Spontaneous; D055815:Young Adult
chemical_list: D002118:Calcium
keywords: Bounce phenomenon; Calcium homeostasis; Cochlea; Cochlear amplifier; Inner hair cells; Otoacoustic emissions; Outer hair cells