Utricular Sensitivity during Hydrodynamic Displacements of the Macula
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JARO (2020) DOI: 10.1007/s10162-020-00769-w D 2020 Association for Research in Otolaryngology
Research Article
Journal of the Association for Research in Otolaryngology
Utricular Sensitivity during Hydrodynamic Displacements of the Macula CHRISTOPHER JOHN PASTRAS,1 DANIEL JOHN BROWN3
SEBASTIAN PAOLO STEFANI,1 IAN S CURTHOYS,2 AARON JAMES CAMP,1 AND
1
The Meniere’s Laboratory, School of Medical Sciences, The University of Sydney, Medical Foundation Building, 92-94 Parramatta Road, Camperdown, Sydney, New South Wales 2050, Australia
2
Vestibular Research Laboratory, School of Psychology, The University of Sydney, Sydney, New South Wales 2050, Australia School of Pharmacy and Biomedical Sciences, Curtin University, Bentley, Western Australia 6102, Australia
3
Received: 29 March 2020; Accepted: 31 July 2020
ABSTRACT To explore the effects of cochlear hair cell displacement, researchers have previously monitored functional and mechanical responses during lowfrequency (LF) acoustic stimulation of the cochlea. The induced changes are believed to result from modulation of the conductance of mechano-electrical transduction (MET) channels on cochlear hair cells, along with receptor potential modulation. It is less clear how, or if, vestibular hair cell displacement affects vestibular function. Here, we have used LF (G20 Hz) hydrodynamic modulation of the utricular macula position, whilst recording functional and mechanical responses, to investigate the effects of utricular macula displacement. Measured responses included the Utricular Microphonic (UM), the vestibular short-latency evoked potential (VsEP), and laser Doppler vibrometry recordings of macular position. Over 1 cycle of the LF bias, the UM amplitude and waveform were cyclically modulated, with Boltzmann analysis suggesting a cyclic modulation of the vestibular MET gating. The VsEP amplitude was cyclically modulated throughout the LF bias, demonstrating a relative increase (~20–50 %; re baseline) and decrease (~10–20 %; re baseline), which is believed to be related to the MET conductance and vestibular hair cell sensitivity. The relationship between macular Correspondence to: Christopher John Pastras & The Meniere’s Laboratory, School of Medical Sciences & The University of Sydney & Medical Foundation Building, 92-94 Parramatta Road, Camperdown, Sydney, New South Wales 2050, Australia. email: [email protected]
displacement and changes in UM and VsEP responses was consistent within and across animals. These results suggest that the sensory structures underlying the VsEP, often thought to be a cranial jerk-sensitive response, are at least partially sensitive to LF (and possibly static) pressures or motion. Furthermore, these results highlight the possibility that some of the vestibular dysfunction related to endolymphatic hydrops may be due to altered vestibular transduction following mechanical (or morphological) changes in the labyrinth. Keywords: Utricle, Low-frequency biasing, Operating point, Endolymphatic hydrops, Meniere’s
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