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The Semicircular Canal MicrophonicPresent experiments were designed to quantify the alternating current (AC) component of the semicircular canal microphonic for angular motion stimulation as a function of stimulus frequency and amplitude. The oyster toadfish, Opsanus tau, was used as the experimental model. Calibrated mechanical indentation of the horizontal canal duct was used as a stimulus to generate hair-cell and afferent responses reproducing those present during head rotation. Sensitivity to polarization of the endolymph DC voltage re: perilymph was also investigated. Modulation of endolymph voltage was recorded using conventional glass electrodes and lock-in amplification over the frequency range 0.2-80 Hz. Access to the endolymph for inserting voltage recording and current passing electrodes was obtained by sectioning the anterior canal at its apex and isolating the cut ends in air. For sinusoidal stimulation below approx.10 Hz, the horizontal semicircular canal AC microphonic was nearly independent of stimulus frequency and equal to approximately 4 microV per micron indent (equivalent to approx. 1 microV per deg/s). A saturating nonlinearity decreasing the microphonic gain was present for stimuli exceeding approx.3 micron indent (approx. 12 deg/s angular velocity). The phase was not sensitive to the saturating nonlinearity. The microphonic exhibited a resonance near 30Hz consistent with basolateral current hair cell resonance observed previously in voltage-clamp records from semicircular canal hair cells. The magnitude and phase of the microphonic exhibited sensitivity to endolymphatic polarization consistent with electro-chemical reversal of hair cell transduction currents.
Document ID
20020060743
Acquisition Source
Ames Research Center
Document Type
Preprint (Draft being sent to journal)
Authors
Rabbitt, R. D.
(NASA Ames Research Center Moffett Field, CA United States)
Boyle, R.
(NASA Ames Research Center Moffett Field, CA United States)
Highstein, S. M.
(NASA Ames Research Center Moffett Field, CA United States)
Dalton, Bonnie P.
Date Acquired
August 20, 2013
Publication Date
January 1, 2002
Subject Category
Aerospace Medicine
Meeting Information
Meeting: Association for Research in Otolaryngology
Country: Unknown
Start Date: January 1, 2002
Sponsors: Association for Research in Otolaryngology
Funding Number(s)
CONTRACT_GRANT: NIH-NIDCD-PO1-DC-01837
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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