The Aging Auditory System (eBook)

1.pdf 13
Chapter 1 13
Introduction and Overview 13
1.1 Introduction 13
1.2 Overview 14
1.3 Future Research 19
References 20
2.pdf 21
Chapter 2 21
The Physiology of Cochlear Presbycusis 21
2.1 Introduction 21
2.2 Overview of Normal Mammalian Auditory Physiology 22
2.2.1 Cochlear Amplifier 22
2.2.2 Cochlear Power Supply 25
2.2.3 Cochlear Transduction 25
2.3 Schuknecht’s Four Types of Presbycusis 26
2.4 Sensory Presbycusis 27
2.5 Metabolic Presbycusis 29
2.5.1 Audiometric Data 29
2.5.2 Suprathreshold Data 35
2.5.2.1 Single Tones 35
2.5.2.2 Multiple Tones 37
2.6 Neural Presbycusis 37
2.7 Future Directions 40
2.7.1 Regeneration of Hair Cells 40
2.7.2 Current Injection for Metabolic Presbycusis 41
2.7.3 Cell Regeneration 41
2.8 Relating Animal Models to the Human Condition 43
2.9 Summary 46
References 46
3.pdf 51
Chapter 3 51
Cell Biology and Physiology of the Aging Central Auditory Pathway 51
3.1 Introduction 51
3.2 Cochlear Nucleus 51
3.2.1 Ion Channels 53
3.2.2 Glycine Receptors 54
3.2.3 Gaba 54
3.2.4 Glutamate Receptors 55
3.2.5 Calcium-Binding Proteins 55
3.2.6 Growth Factors 58
3.2.7 Growth-Associated Proteins 59
3.2.8 Mitochondrial DNA Mutations 59
3.2.9 Cochlear Nucleus Physiology 61
3.3 Superior Olivary Complex 64
3.3.1 Lso 64
3.3.2 Mntb 65
3.3.3 Olivocochlear Efferent Systems 66
3.3.4 SOC Physiology 69
3.4 Inferior Colliculus 69
3.4.1 Glutamate 70
3.4.2 Gaba 70
3.4.3 Metabolism 72
3.4.4 Inferior Colliculus Physiology 73
3.5 Auditory Cortex 77
3.5.1 Neurochemistry 79
3.5.2 Auditory Thalamus and Cortex Physiology 80
3.6 Summary and Conclusions 81
References 82
4.pdf 87
Chapter 4 87
Closing the Gap Between Neurobiology and Human Presbycusis: Behavioral and Evoked Potential Studies of Age-Related Hearing Lo 87
4.1 Introduction 87
4.1.1 Contributions of Animal Models to Understanding Human Presbycusis 87
4.1.2 Distinctions Between the Simple and the Complex in Signals and in Listening Environments 88
4.1.3 Chronological versus Biological Aging and Individual Differences in ARHL 90
4.2 Are There Different Types of Hearing Loss, Different in Origin and in their Effects? 92
4.2.1 The Psychophysical Question: Is ARHL Simply a Loss of Absolute Sensitivity? 92
4.2.2 Neurobiology: Might the Type of ARHL Differ According to the Site of the Pathology? 93
4.2.3 Peripheral Hearing Loss Can Alter Both the CANS and Central Auditory Processing 94
4.2.4 Experimental Manipulations at Different Sites Can Produce Different Types of Hearing Loss 95
4.2.4.1 Manipulating the Integrity of the Cochlea 95
4.2.4.2 Manipulating the Central Auditory Nervous System 96
4.3 Noninvasive Objective Methods for Studying ARHL in Animals and Humans 97
4.3.1 Introduction to the Methods 97
4.3.2 The Application of These Methods to the Study of ARHL 99
4.4 Peripheral Degeneration: A Major Source of ARHL in These Rodent Models 102
4.4.1 Cochlea Pathology and Its Relationship to Threshold Measures of ARHL 102
4.4.2 Suprathreshold Measures of ARHL 104
4.5 Central Processing Deficits: Temporal, Spectral, and Spatial Dimensions 106
4.5.1 Neurobiological Measures of Complex Processing 106
4.5.2 AEP Studies of Complex Auditory Processing 107
4.5.3 Behavioral Studies of Complex Auditory Processing 110
4.6 A Summary of Past Research and Its Implications for Moving Forward 114
References 117
5.pdf 123
Chapter 5 123
Behavioral Studies With Aging Humans: Hearing Sensitivity and Psychoacoustics 123
5.1 Introduction 123
5.1.1 Methodology 124
5.2 Basic Hearing Sensitivity 125
5.2.1 Cross-Sectional Epidemiologic Studies 125
5.2.2 Longitudinal Data 127
5.3 Frequency/Intensity Discrimination 130
5.4 Frequency Selectivity 132
5.4.1 Auditory Filtering 132
5.4.2 Suppression 133
5.5 Temporal Sensitivity: Simple Stimuli 135
5.5.1 Temporal Resolution 135
5.5.2 Duration Discrimination 138
5.6 Temporal Sensitivity: Complex Stimuli 140
5.7 Temporal Order Perception 141
5.8 Summary 142
References 143
6.pdf 147
Chapter 6 147
Binaural Processing and Auditory Asymmetries 147
6.1 Introduction 147
6.2 Perception of Auditory Space in the Free Field 149
6.2.1 Duplex Theory 149
6.2.2 Spectral Cues in Sound Localization 150
6.2.3 Effects of Age and Hearing Loss on Sound Localization 151
6.2.3.1 Horizontal Sound Localization 151
6.2.3.2 Vertical Sound Localization 153
6.2.4 Minimum Audible Angles 155
6.2.5 Distance Perception 156
6.3 Binaural Processing Under Headphones 156
6.3.1 ITDs 156
6.3.2 IIDs 158
6.3.3 Binaural Masking-Level Difference 159
6.4 Additional Temporal Aspects of Binaural Perception 161
6.4.1 Effects of Reverberation 161
6.4.2 Precedence Effect 164
6.4.3 Binaural Perception of Dynamic Stimuli 166
6.5 Perception of Masked Speech in the Free Field 167
6.6 Effects of Laterality 169
6.7 Practical Considerations 170
References 171
7.pdf 178
Chapter 7 178
Effects of Senescent Changes in Audition and Cognition on Spoken Language Comprehension 178
7.1 Introduction 178
7.2 An Integrated Approach to Investigating Spoken Language Comprehension 179
7.2.1 Levels of Processing 180
7.2.2 Executive Control 180
7.2.3 Limited Working Memory Resources 181
7.2.4 Speed of Processing 182
7.2.5 Evaluating How Age Affects the Comprehension of Spoken Language 182
7.3 The Effects of Age-Related Changes in Sensory Processes on the Comprehension of Spoken Language 183
7.3.1 Listening in Quiet 183
7.3.2 Listening in Noise 184
7.4 Effects of Age-Related Changes in More Central Auditory Processes on the Comprehension of Spoken Language 185
7.4.1 Effects of Age on Processing Capacity and Executive Control Over Auditory Processes 186
7.4.1.1 Age Differences in Channel Capacity 187
7.4.1.2 Age-Related Differences in Top-Down Control Over Auditory Gain 187
7.4.1.3 Age-Related Changes in Automatic Versus Controlled Processing 188
7.4.2 Effects of Age on Source Segregation 189
7.4.2.1 Source Segregation Based on Harmonic Structure 193
7.4.2.2 Source Segregation Based on Attentional Focus 193
7.4.2.3 Source Segregation Based on Spatial Separation 194
7.4.2.4 Source Segregation Based on Prior Knowledge 195
7.4.2.5 Source Segregation Based on Other Aspects of the Acoustic Scene 196
7.4.3 Effects of Age on Informational Masking 197
7.4.4 Tentative Conclusions Concerning Age-Related Changes in More Central Auditory Processes 199
7.5 Effects of Age-Related Changes in Cognitive Processes on Comprehension of Spoken Language 200
7.5.1 Working Memory 200
7.5.2 Inhibitory Control 200
7.5.3 Processing Speed 201
7.5.4 Tentative Conclusions Concerning Cognitive Mediators of Age-Related Changes in Spoken Language Comprehension 202
7.6 Auditory-Cognitive Interactions 202
7.7 Auditory-Cognitive Interactions in Different Populations 206
7.7.1 Interaction of Auditory and Cognitive Factors in Older Listeners With Hearing Loss 208
7.7.2 Interventions 208
7.7.2.1 Hearing Aids 209
7.7.2.2 The need for Comprehensive Rehabilitation 211
7.7.3 Interaction of Auditory and Cognitive Factors in Older Listeners with Cognitive Loss 211
7.7.3.1 Prevalence 211
7.7.3.2 Correlations Between Sensory and Cognitive Impairment in Population Studies 212
7.7.3.3 Intervention 213
7.8 Summary and Recommendations for Future Research 213
7.8.1 Summary 213
7.8.2 Recommendations for Future Research 214
References 214
8.pdf 222
Chapter 8 222
Factors Affecting Speech Understanding in Older Adults 222
8.1 Introduction 222
8.2 Peripheral, Central-Auditory, and Cognitive Factors 224
8.2.1 Peripheral Factors 225
8.2.1.1 Articulation Index Framework 225
8.2.1.2 Plomp’s Speech-Recognition Threshold Model 236
8.2.1.3 Simulated Hearing Loss 241
8.2.1.4 Factorial Combinations of Age and Hearing Status 242
8.2.1.5 Longitudinal Studies 244
8.2.1.6 Limitations of the Peripheral Explanation 246
8.2.2 Beyond Peripheral Factors 247
8.3 Amplification and Speech Understanding 251
8.4 Improving the SNR 258
8.5 Summary 261
References 261
9.pdf 269
Chapter 9 269
Epidemiology of Age-Related Hearing Impairment 269
9.1 Introduction 269
9.2 Classification/Definition of ARHL 270
9.3 Evaluating the Evidence for Causal Associations: Identifying Risk Factors 271
9.4 Descriptive Epidemiology 273
9.4.1 Prevalence 273
9.4.2 Incidence 273
9.4.3 Age, Gender, Ethnicity/Race, Geographic Location, and Temporal Trends 274
9.5 Risk Factors 276
9.5.1 Genetic Factors 276
9.5.2 Cardiovascular Disease and Cardiovascular Disease Risk Factors 277
9.5.3 Noise 278
9.5.4 Solvents and Other Environmental Chemical Exposures 278
9.5.5 Radiation and Medications 279
9.5.6 Vitamins B12 and D and Folate 280
9.6 Summary 280
References 281
10.pdf 285
Chapter 10 285
Interventions and Future Therapies: Lessons from Animal Models 285
10.1 Introduction 285
10.2 Contributions of Animal Models 287
10.3 Oxidative Imbalance: Target for Interventions 288
10.3.1 Oxidative Stress 288
10.3.2 Pharmacological Interventions 289
10.4 Dietary Restriction 291
10.5 Manipulation of Hearing-Loss Induced Central Plasticity 292
10.5.1 Functional Consequences 292
10.5.2 Diminished Inhibition 293
10.6 Treatment with an Augmented Acoustic Environment 294
10.6.1 Importance of Tonotopic Organization 294
10.6.2 Ameliorative Effects of AAE Treatment 295
10.6.3 Deleterious Effects of AAE Treatment 295
10.6.4 Summary of AAE Treatment 296
10.7 Gonadal Hormones 297
10.7.1 Estrogen 297
10.7.2 Androgen 297
10.7.3 Sex Hormones and Noise-Induced Hearing Loss 298
10.8 Summary and Outlook 298
References 299