Acoustic sensitivity of the vestibular system and mechanical analysis of the tectorial membrane in mammals

Jones, Gareth Paul (2012) Acoustic sensitivity of the vestibular system and mechanical analysis of the tectorial membrane in mammals. Doctoral thesis (DPhil), University of Sussex.

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Abstract

This thesis cover two separate topics related to the function of the mammalian inner ear.

Acoustic sensitivity of the vestibular system.

Data are presented showing facilitation of the auditory startle response by tones outside the range of the mouse cochlea. The sensation of these low frequency tones is demonstrated to be mediated via the acoustically sensitive sacculus of the vestibular system by data collected from Nox3-/- mice. These mice lack the otoconia of the vestibular system and, unlike the wild-type mice, only show facilitation to tones within the range of the mouse cochlea, and not in response to tones <4 kHz.

The mechanical properties of the tectorial membrane (TM).

The mechanical properties of the TM are investigated using a laser interferometer-based method for tracking the longitudinal propagation of a radially shearing travelling wave in segments of TM isolated from the basal and apical regions of the wild-type cochlea. The properties of these travelling waves (wave propagation velocity and wave amplitude decay) are tracked over a range of stimulus frequencies (1-20 kHz). The viscoelastic properties, shear storage modulus (G’) and shear viscosity (η), are estimated over this frequency range and are found to be lower in the apical TM segments compared to the basal TM segments, indicating the apical region of the TM is less stiff than the basal region. These data are compared to data collected from TM segments isolated from the basal cochlear region of three mutant groups, each lacking expression of TM-specific proteins; α-tectorin (TectaY1870C/+), β-tectorin (Tectb-/-) and otoancorin (OtoaEGFP/EGFP), using the same laser interferometer-based method. The viscoelastic properties are estimated for each of the mutants and indicate varying degrees of loss of structural integrity in their respective TM segments. Reflective difference between the wild-types and mutants are also observed and compared.

Item Type: Thesis (Doctoral)
Schools and Departments: School of Life Sciences > Biology and Environmental Science
Subjects: Q Science > QP Physiology > QP0351 Neurophysiology and neuropsychology > QP0431 Senses > QP0448 Special senses > QP0471 Equilibrium. Labyrinths of the ear. General works
Depositing User: Library Cataloguing
Date Deposited: 18 May 2012 09:34
Last Modified: 25 Aug 2015 14:00
URI: http://sro.sussex.ac.uk/id/eprint/38740

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