Munich Neuroscience Calendar

Event:

14.12.2017, 17:00 TUM Institute for Medical Engineering

Event Type: Talk
Speaker: Markus Drexl
Institute: Deutsches Schwindel- und Gleichgewichtszentrum des Klinikums der Universität München, Großhadern

Title: The Impact of Low-Frequency Sound on the Human Inner Ear

Location:
Hörzentrum München - Klinikum rechts der Isar
Ismaninger Straße 33
81675 München

Host: HöReN Research Network
Host Email: miguel.obando@tum.de
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. These findings clearly demonstrate that the origin of the Bounce lies in the modulation of cochlear amplifier gain. Air-conducted sound is not only detected by the cochlea, but also, at higher intensities, by the vestibular system. Here we show that vestibular evoked myogenic potentials, which are muscle contractions as part of a vestibular reflex chain, can be evoked with frequencies as low as 40 Hz. In the light of these findings, the effects of long-duration, anthropogenic LF sound on the human inner ear require further research.