Contents Series Preface Preface Acknowledgments Abbreviations vii ix xiii xxv Introduction xxxi Definition...xxxi Normal Hearing...xxxi Deafness...xxxi Overall Concept of the Bionic Ear...xxxii Training in the Use of the Bionic Ear...xxxiii Fundamental Objections and Questions...xxxiii Answers to the Fundamental Objections...xxxiv 1. A History 1 Pre-science...1 Eighteenth Century...1 Nineteenth Century...3 Twentieth Century...3 1900 to 1930s: Early Hearing Aids...3 1930s to 1940s: Initial Indirect Electrical Stimulation in the Human... 4 1950s to 1960s: Initial Direct Electrical Stimulation in the Human...6 1960s: Fundamental Research in the Experimental Animal...9 1970s: Fundamental Research in the Experimental Animal and Human... 12 1980s: Fundamental Research, Industrial Development, and Clinical Trials... 23 xv
xvi Contents 1990s: Continuing Fundamental Research and Industrial Development... 45 References... 46 2. Surgical Anatomy 58 Overview... 58 Temporal Bone... 59 Components... 59 Embryology... 60 Mastoid Air Cell System and Variations... 61 Blood Supply and Innervation... 61 Infant and Young Child... 62 External Ear... 64 Pinna... 64 External Auditory Meatus... 65 Middle Ear... 65 Ossicles... 65 Muscles... 66 Relationships... 67 Posterior Tympanotomy... 70 Round Window and Niche... 71 Inner Ear... 73 Osseous... 73 Membranous... 77 Histology of the Cochlea... 79 Embryology... 82 Central auditory system... 83 Overview... 83 Auditory Nerve... 86 Cochlear Nucleus... 87 Superior Olivary Complex... 89 Lateral Lemniscus... 91 Inferior Colliculus... 91 Superior Colliculus... 92 Medial Geniculate Body... 92 Auditory Cortex... 93 References... 93 3. Surgical Pathology 100 Inflammation...100 Classification...101 Etiology...101 Pathophysiology...101 Insertion Trauma...104 Tissue Responses in the Cochlea of the Experimental Animal...104
Contents xvii Tissue Responses in the Human...109 Bio-compatibility of Materials...112 Methods of Investigation...112 Tissue Response...113 Infection...116 Otitis Media...116 Labyrinthitis and Meningitis...117 Experimental Animal Studies...122 Host Factors and Foreign Bodies...136 Clinical Protocol...139 Deafness and the Central Auditory Pathways...140 Spiral Ganglion...140 Cochlear Nucleus...141 Pons and Midbrain...142 Human Brainstem...143 Prenatal (Congenital) and Postnatal Hearing Loss...144 Genetic and Chromosomal...144 Acquired...148 References...151 4. Neurobiology 160 Overview...160 Definition of Terms...160 Current and Charge...160 Voltage...161 Resistance...161 Capacitance...161 Impedance...161 Electrode/Tissue Interface...162 Polarization...162 Charge Transfer...162 Charge Density...163 Equivalent Circuits...163 Impedance...165 Corrosion-Stimulus Parameters...168 Mechanisms...168 Stimulus Parameters...169 Scanning Electron Microscope Evaluation of Electrodes...171 Electrical Parameters and Neural Stimulation...172 Electrochemically Safe Stimulus Parameters...172 Charge Density and Charge per Phase...173 Biochemical Effects...173 Neural Preservation...174 Electrical Stimulation of the Cochlear Nerve...175 Acute studies on the Effects of Low Rates of Stimulation...175
xviii Contents Chronic Studies on the Effects of Low Rates of Stimulation...176 Acute Studies on the Effects of High Rates of Stimulation...183 Chronic Studies on the Effects of High Rates of Stimulation...187 Electrical Stimulation of the Cochlear Nucleus...189 Acute Studies on the Effects of Low Rates of Stimulation...189 Chronic Studies on the Effects of Low Rates of Stimulation...189 References...190 5. Electrophysiology 199 General Neurophysiology...199 Action Potentials...199 Strength-Duration Curves...202 Electrical Models of the Nerve Membrane...203 Convergence and Divergence...204 Auditory Physiology...205 Physics of Sound...206 External and Middle Ear Function...207 Cochlea...208 Auditory Neurophysiology...211 Electrophonic Hearing (Electrical Stimulation of the Cochlea)...233 Mechanisms...233 Electrophonic Hearing and Cochlear Implantation...235 Electrical Stimulation of the Cochlear Nerve...236 Temporal Coding...237 Place Coding...262 Intensity Coding...272 References...274 6. Psychophysics 296 Acoustic Stimulation...296 Pitch and Timbre...297 Loudness...302 Critical Band and Ratio...305 Musical Acoustics...308 Bilateral Hearing...311 Electrical Stimulation...315 Temporal Information...315 Temporal Information: Prelinguistically Deaf...323 Place Information...326 Place Information: Prelinguistically Deaf...338 Loudness...341 Intensity Information: Prelinguistically Deaf...352 Musical Perception...353 Bimodal Stimulation...356 Bilateral Stimulation...358
Contents xix References...365 7. Speech (Sound) Processing 381 Acoustic...381 Articulators and Vocal Tract Shape...382 Speech Analysis...382 Speech Perception and Production...385 Binaural Hearing...395 Acoustic Models of Cochlear Implant Speech-Processing Strategies...395 Channel Vocoders and Fixed Filters...395 Formant Vocoders...397 Acoustic Representation of Electrical Stimulation...398 Speech Cues...401 Channel Numbers...402 Speech in Noise...404 Channel Selection...404 Electrical Stimulation: Principles...405 Channel Numbers...406 Channel Selection...407 Speech in Noise...408 Speech Processing Strategies...409 Multiple-Channel Strategies: Fixed Filter Schemes...411 Multiple-Electrode Strategies: Formant and Spectral Cue Extraction...415 Adaptive Dynamic Range Optimization (ADRO)...432 Dual Microphones...433 Bimodal Speech Processing...435 Bilateral Speech Processing...438 References...442 8. Engineering 454 Electronic and Communications Engineering...456 Principles...456 Speech Processors...465 Receiver-Stimulators...484 Bioengineering...502 Design Principles...502 Design Realization...518 Conclusion...536 References...537 9. Preoperative Selection 550 Aims...550 Adults...550 Children...551
xx Contents Clinical Protocol...552 Medical History and Examination...553 Aims...553 History...553 Physical Examination...554 Diagnosis-Etiology...554 Adults...554 Children...555 Audiology...559 Pure Tone Thresholds...559 Impedance Audiometry...562 Hearing Aid Evaluation...563 Cochlear Microphonics and ABR Tests for Neuropathy...564 Communication...566 Speech Perception...566 Speech Production...568 Language...568 Special Investigations...569 Radiology...569 Electrical Stimulation of the Promontory...572 Vestibular Assessment...574 Management...575 Hearing and Speech Perception...575 Predictive Factors...576 Preoperative Counseling...586 References...586 10. Surgery 595 Overview...595 Brief History...596 Aims...596 Position Multiple Electrodes Close to the Auditory Nerves...596 Implant Electrode with Minimal Trauma to the Inner Ear...597 Locate the Receiver-Stimulator to Allow Optimal Use of a Microphone, Speech Processor and Transmitting Coil...597 Implant Receiver-Stimulator to be Unaffected by Growth Changes...597 Implant Operation Performed Safely...597 Fundamentals and Clinical Practice...597 Preoperative Measures...598 Incision...599 First Stage Mastoid Cell Removal...603 Creation of a Bed for the Receiver-Stimulator...603 Creation of Gutter for the Lead Wire Assembly...606 Exposure of the Round Window via a Posterior Tympanotomy...607
Contents xxi Cochleostomy (Opening into the Inner Ear)...608 Insertion of Arrays...612 Sealing the Opening...617 Perilymph Gusher...618 Fixing the Electrode Array and Receiver-Stimulator...619 Flap and Wound Closure...620 Radiology...620 Postoperative Care...621 Complications and Management...621 Intraoperative Complications...621 Postoperative Complications...623 Special Cases...639 Ossified Cochlea...639 Secretory (Serous) Otitis Media...642 Tympanic Membrane Perforation and Chronic Suppurative Otitis Media...642 Open Mastoid...642 Congenital or Genetic Malformation of the Cochlea...643 Transmastoid Labyrinthectomy and Acoustic Neuroma...643 Insertion and Reinsertion...644 Pedestal (Plug and socket)...644 Magnetic Resonance Imaging (MRI)...645 References...645 11. Rehabilitation 654 Aims...654 Principles...655 Plasticity in the Experimental Animal...655 Plasticity Psychophysics...656 Plasticity Cross-Modality in Humans...661 Analytic Versus Synthetic Training...661 Mapping and Fitting Procedures in Adults and Children...663 Physiological and Psychophysical Principles...663 Producing a MAP...665 Signal Gain...668 Loudness Summation...670 Patient Preference...670 Training in Adults and Children...670 General...671 Predictive Factors...672 Strategy and Time Course for Learning...674 Analytic...676 Synthetic...676 Environmental Sounds...677 Background Noise...677
xxii Contents Music...678 Telephone...678 Television...679 Mapping and Fitting Children...679 Preprogramming Training...680 Conditioning...680 Initial Setting...681 Follow-up Device Settings....682 Neural Response Telemetry...683 Training in Children...684 General...684 Personnel...684 Pragmatics...686 Speech Perception...686 Perception of Environmental Sounds...688 Speech Production...689 Language...690 Education of Children...693 Acoustic Environment...693 Strategies...694 Program for Implanted Children...695 Counseling of Adults and Children...696 References...697 12. Results 707 Aims...707 Development of Tests...707 Speech and Sound Perception: Test Principles...708 Variability of Materials and Responses...708 Prerecorded Versus Live Voice...709 Training Effects and Experience...710 Closed-Set Tests...710 Speech Features (Consonants and Vowels)...712 Open-Set Tests...713 Speech Reading...714 Speech Tracking...715 Speech in Noise...716 Environmental Sounds...717 Test Batteries...717 Questionnaires...718 Bimodal and Bilateral Speech Processing...718 Speech Production: Test Principles...720 Imitative and Spontaneous Speech...720 Computer Aided Speech and Language Assessment procedure (CASALA)...721
Contents xxiii Language: Test Principles...721 Receptive Language...722 Expressive Language...722 Pragmatics...724 Speech perception with Cochlear Implants...724 Predictive Factors...724 Speech-Processing Strategies for Postlinguistically Deaf Adults...726 Speech-Processing Strategies for Pre- and Postlinguistically Deaf Children...738 Speech production with Cochlear Implants...744 Single-Channel System (3M/House)...744 Nucleus Multiple-Channel (F0/F1/F2) and Multipeak Strategies...744 Language Development for Pre- and Postlinguistically Deaf Children...747 Receptive Language...747 Expressive Language...750 Cognition...751 References...752 13. Socioeconomics and Ethics 767 Speech and Language Benefits...767 Biological Safety...767 Social Benefits...768 Personal...768 Family...768 School...769 Economic Benefits...769 Economic Measures...769 Cost-Effectiveness...770 Cost-Benefit Analysis...770 Quality of Life...771 Ethics...773 Human Experimentation...773 Rights of Children...779 Attitudes of Hearing-Impaired People...782 References...783 14. Research Directions 787 Improved Sound Fidelity and Speech Processing...787 Selection of Information...788 Optimal Rate Stimulation...788 Improved Coding...789 Improved Speech Perception in Noise...795 Bimodal Speech Processing...795 Bilateral Speech Processing...797 Dual Microphones...797 Improved Speech and Language in Children...797 Totally Implantable Cochlear Prosthesis...801 Auditory Nerve Preservation and Regeneration...802 References...809 Index 813
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