Nonlinear amplification by active sensory hair bundles [Elektronische Ressource] / von Kai Dierkes

Nonlinear ampli cationby active sensory hair bundlesDissertationzur Erlangung des akademischen GradesDoctor rerum naturalium(Dr. rer. nat.)vorgelegtder Fakultat Mathematik undNaturwissenschaftender Technischen Universitat DresdenvonKai Dierkesgeboren am 21.2.1977 in EssenEingereicht am 10. Juni 2010Eingereicht am 10. Juni 2010Verteidigt am 12. August 20101. Gutachter: Prof. Dr. Frank Julic her2.hter: Prof. Dr. Alexander NeimanAbstractThe human sense of hearing is characterized by its exquisite sensitivity, sharp fre-quency selectivity, and wide dynamic range. These features depend on an activeprocess that in the inner ear boosts vibrations evoked by auditory stimuli. Sponta-neous otoacoustic emissions constitute a demonstrative manifestation of this phys-iologically vulnerable mechanism. In the cochlea, sensory hair bundles transducesound-induced vibrations into neural signals. Hair bundles can power mechanicalmovements of their tip, oscillate spontaneously, and operate as tuned nonlinear am-pli ers of weak periodic stimuli. Active hair-bundle motility constitutes a promisingcandidate with respect to the biophysical implementation of the active process un-derlying human hearing.The responsiveness of isolated hair bundles, however, is seriously hampered byintrinsic uctuations. In this thesis, we present theoretical and experimental resultsconcerning the noise-imposed limitations of nonlinear ampli cation by active sensoryhair bundles.