Impedance and electromechanical vibration measured in the organ of Corti up to 50 kHz [Elektronische Ressource] : new insights for cochlear amplification / vorgelegt von Marc Philippe Scherer

Description

Impedance and Electromechanical VibrationMeasured in the Organ of Corti up to 50 kHz:New Insights for Cochlear AmplificationDissertationzur Erlangung des Grades eines Doktorsder Naturwissenschaftender Fakultät für Mathematik und Physikder Eberhard-Karls-Universität zu Tübingenvorgelegt vonMarc Philippe Schereraus Tettnang2005Tag der mündlichen Prüfung: 4. Oktober 2005Dekan: Prof. Dr. P. Schmid1. Berichterstatter: Prof. Dr. A.W. Gummer/Prof. Dr. H. Ruder2. Berichterstatter: Prof. Dr. D. Kern3. Berichterstatter: Prof. Dr. Ch. SteeleContentsList of abbreviations 1Summary 31 Introduction 51.1 Motivation ................................... 51.2 Signal processing capabilities of the ear . . . . . . . . . . . . . . . . . . . 51.2.1 Sensitivity................................ 61.2.2 Frequencyresolution.......................... 61.2.3 Intensityresolution........................... 71.2.4 Temporalresolution.......................... 71.3 Anatomyoftheinnerear–thecochlea.................... 71.3.1 GeneralAnatomy............................ 81.3.2 Cochlearpartition........................... 101.4 Stateoftheart................................. 111.5 Purposeofthisstudy.............................. 142Methods 172.1 Animalpreparation............................... 172.2 Signalprocesing................................ 172.3 Velocitymeasurement............................. 202.4 Theoryofatomicforcecantileversinfluid.................. 202.4.

Sujets

• Gesundheit

Informations

• Publié par: eberhard_karls_universitat_tubingen
• Publié le: 01 janvier 2005
• Nombre de lectures: 22
• Langue: English
• Poids de l'ouvrage: 15 Mo

Extrait

Impedance and Electromechanical Vibration Measured in the Organ of Corti up to 50 kHz: New Insights for Cochlear Amplification

Dissertation zur Erlangung des Grades eines Doktors der Naturwissenschaften der Fakultät für Mathematik und Physik der EberhardKarlsUniversität zu Tübingen

vorgelegt von

Marc Philippe Scherer aus Tettnang

2005

Tag der mündlichen Prüfung: Dekan: 1. Berichterstatter: 2. Berichterstatter: 3. Berichterstatter:

4. Oktober 2005 Prof. Dr. P. Schmid Prof. Dr. A.W. Gummer/Prof. Dr. H. Ruder Prof. Dr. D. Kern Prof. Dr. Ch. Steele

Contents

List of abbreviations

Summary

1

2

Introduction 1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 Signal processing capabilities of the ear . . . . . . . . . . . . . . . . . . . 1.2.1 Sensitivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2.2 Frequency resolution . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2.3 Intensity resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2.4 Temporal resolution . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 Anatomy of the inner ear – the cochlea . . . . . . . . . . . . . . . . . . . . 1.3.1 General Anatomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.2 Cochlear partition . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 State of the art . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5 Purpose of this study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Methods 2.1 Animal preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Signal processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 Velocity measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4 Theory of atomic force cantilevers in fluid . . . . . . . . . . . . . . . . . . 2.4.1 General theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4.2 Harmonic driving force . . . . . . . . . . . . . . . . . . . . . . . . . 2.5 Experimental validation of the cantilever theory . . . . . . . . . . . . . . . 2.5.1 Generation of a point force . . . . . . . . . . . . . . . . . . . . . . 2.5.2 Alignment of cantilever and electrode . . . . . . . . . . . . . . . . 2.5.3 Electrical contact to the cantilever . . . . . . . . . . . . . . . . . . 2.5.4 Coulomb force stimulus generation . . . . . . . . . . . . . . . . . . 2.5.5 Estimation of the mechanical driving point impedance . . . . . . . 2.5.6 Embedding of the electrode in a flat surface . . . . . . . . . . . . . 2.6 Impedance of the organ of Corti . . . . . . . . . . . . . . . . . . . . . . . 2.6.1 Measurement principle . . . . . . . . . . . . . . . . . . . . . . . . . 2.6.2 Magnetic cantilevers . . . . . . . . . . . . . . . . . . . . . . . . . . 2.6.3 Magnetic stimulus generation . . . . . . . . . . . . . . . . . . . . . 2.6.4 Determination of contact . . . . . . . . . . . . . . . . . . . . . . . 2.6.5 Equivalent impedance and force calibration . . . . . . . . . . . . .

1

3

5 5 5 6 6 7 7 7 8 10 11 14

17 17 17 20 20 20 23 24 24 24 25 25 26 26 27 27 28 28 29 29

3

4

2.7

Electrically evoked deformation of the organ of Corti . . . . . . . . . . . . 2.7.1 Electrical stimulus generation . . . . . . . . . . . . . . . . . . . . . 2.7.2 Drug administration . . . . . . . . . . . . . . . . . . . . . . . . . .

Results 3.1 Validation of the cantilever theory . . . . . . . . . . . . . . . . . . . . . . 3.1.1 Determination ofTandβ. . . . . . . . . . . . . . . . . . . . . . . 3.1.2 Comparison between model and data . . . . . . . . . . . . . . . . . 3.2 Impedance of the organ of Corti . . . . . . . . . . . . . . . . . . . . . . . 3.2.1 A Voigt-Kelvin viscoelastic description of impedance . . . . . . . . 3.2.2 Dominance of the real component near the characteristic frequency 3.2.3 Absence of an inertial component . . . . . . . . . . . . . . . . . . . 3.2.4 Spatial dependence of the mechanical parameters . . . . . . . . . . 3.2.5 Qualitative observations . . . . . . . . . . . . . . . . . . . . . . . . 3.3 Electrically evoked vibration of the organ of Corti . . . . . . . . . . . . . 3.3.1 First and second row OHC . . . . . . . . . . . . . . . . . . . . . . 3.3.2 Third row OHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.3 IHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.4 Tunnel of Corti . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.5 Outer tunnel and Hensen’s cells . . . . . . . . . . . . . . . . . . . . 3.3.6 Effect of drugs on displacement . . . . . . . . . . . . . . . . . . . . 3.3.6.1 Blockers of electromechanical transduction . . . . . . . . 3.3.6.2 Blockers of channels in the stereocilia . . . . . . . . . . . 3.3.6.3 Blockers of channels in the basolateral cell membrane . . 3.4 Force generation in the organ of Corti . . . . . . . . . . . . . . . . . . . . 3.4.1 First and second row OHC . . . . . . . . . . . . . . . . . . . . . . 3.4.2 Third row OHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.3 IHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.4 Outer tunnel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.5 Hensen’s cells . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Discussion 4.1 Validation of the cantilever theory . . . . . . . . . . . . . . . . . . . . . . 4.2 Impedance of the organ of Corti . . . . . . . . . . . . . . . . . . . . . . . 4.2.1 Stiffness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.2 Contact versus non-contact impedance measurements . . . . . . . 4.2.3 Biophysical significance for cochlear amplification . . . . . . . . . . 4.3 Force generation in the organ of Corti . . . . . . . . . . . . . . . . . . . . 4.3.1 Driving force for the force . . . . . . . . . . . . . . . . . . . . . . . 4.3.2 Properties of the force . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 Electrically evoked deformation of the organ of Corti . . . . . . . . . . . . 4.4.1 Reticular-lamina displacement . . . . . . . . . . . . . . . . . . . . 4.4.2 Implications for cochlear amplification . . . . . . . . . . . . . . . . 4.5 Future experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

References

30 30 31

33 33 33 33 35 36 37 38 38 39 41 41 43 43 43 43 45 46 47 47 47 48 49 50 50 50

53 53 54 54 55 56 58 58 59 60 60 61 63 63

65

Abbreviations

BM CF HeC IHC IPC ISC OC OHC OPC OT RL TM ToC

Basilar membrane Characteristic frequency Hensen’s cell Inner hair cell Inner pillar cell Inner sulcus cell Organ of Corti Outer hair cell Outer pillar cell Outer tunnel Reticular lamina Tectorial membrane Tunnel of Corti

1