The Auditory Cortex (eBook)

Preface 5
References 6
Acknowledgments 8
Contents 9
Contributors 11
1 The Historical Development of Ideas About the Auditory Cortex 15
1 Introduction: Early Theories of Brain and the Perception of Sound 15
2 First Experimental Studies in Monkeys: David Ferrier 16
3 The Clinical Experience: Localization of Human Auditory Cortex in the Superior Temporal Gyrus 18
4 Experimental Studies in Other Animals: Cats, Dogs, Rabbits 19
5 Anatomical Identification of Auditory Cortex 20
6 New Experimental Studies in Animals 25
7 Entering the Modern Era: Multiple Cortical Fields, Tonotopicity, and Thalamocortical Projections 29
8 Later Studies in Cats, Monkeys, and Other Species 31
9 Modern Studies of Chemoarchitecture and the Functional Parcellation of Auditory Cortex 40
10 Summary 50
References 50
2 A Profile of Auditory Forebrain Connections and Circuits 55
1 Profiling the Auditory Forebrain 57
2 Medial Geniculate Body Organization 57
2.1 Ventral Division 57
2.2 Dorsal Division 59
2.4 Medial Division 59
3 Auditory Thalamic Neurotransmitter Profile 60
3.1 Excitatory Amino Acids 60
3.2 Gamma-Aminobutyric Acid 60
4 Medial Geniculate Body Connections 60
4.1 Tectothalamic Pathway 61
4.2 Extracollicular Projections 63
4.3 Thalamocortical System 64
4.4 Thalamoamygdaloid System 64
4.5 Thalamotectal System 64
4.6 Corticothalamic System 64
5 Auditory Cortex 64
5.1 Supragranular Layers 64
5.2 Granular Layers 65
5.3 Infragranular Layers 66
6 Auditory Cortex Connectivity 66
6.1 Thalamic Areal and Laminar Input 69
6.2 Corticocortical System 72
6.3 Commissural System 72
6.4 Corticothalamic System 72
6.5 Corticocollicular System 73
6.6 Corticopontine System 77
6.7 Other Corticofugal Systems 78
7 Neurochemical Profile 78
7.1 Gamma-Aminobutyric Acid 78
7.2 Other Neurotransmitters 78
7.3 Aspects of Auditory Cortex Physiology 78
8 Toward a Theory of Auditory Forebrain Operations 81
8.1 Forebrain Auditory System 81
8.2 Multimodal Interactions 81
8.3 Auditory-Motor Relations 81
8.4 Auditory-Limbic Interactions 81
9 Directions for Future Research 83
References 83
3 Thalamocortical Relations 89
1 The Auditory Thalamus 89
1.1 Auditory Thalamic Subdivisions 90
1.1.1 Ventral Division 90
1.1.2 Dorsal Division 91
1.1.3 Medial Division 92
1.2 Extracellular Physiology 92
1.2.1 Ventral Division 92
1.2.2 Dorsal Division 93
1.2.3 Medial Division 93
1.3 Intracellular Physiology 93
1.4 Medial Geniculate Body Responses in Unanesthetized Animals 93
2 Thalamocortical Projections 94
2.1 Thalamic Projections to the Thalamic Reticular Nucleus 94
2.2 Thalamic Projections to the Cortex: The Core and Matrix Theory 95
2.3 Core, Belt, and Parabelt Cortical Regions 95
2.4 Medial Geniculate Body Cortical Projection: Ventral Division 96
2.5 Medial Geniculate Body Cortical Projection: Dorsal Division 96
2.6 Medial Geniculate Body Cortical Projection: Medial Division 97
3 Auditory Thalamocortical Physiology 98
3.1 Intrinsic Membrane Properties in Auditory Cortex 98
3.1.1 Intracellular Properties of Auditory Cortex Cells 98
3.2 Thalamocortical Synaptic Physiology 99
3.2.1 Thalamocortical Synapses in Slice Preparations 99
3.3 Intracortical Feedforward and Feedback Connections 100
3.3.1 Cortical Inhibitory Networks 100
3.3.2 Comparing Auditory Cortex with Other Cortical Areas 101
3.3.3 Cortical Interneurons and Thalamic Projections 101
3.4 Comparison of Thalamic and Cortical Response Properties In Vivo 101
3.5 Comparing Auditory Cortex and Midbrain Models of Information Processing 102
4 Auditory Thalamocortical Transformation 102
4.1 Models of the Thalamocortical Transformation 102
4.2 Phasic Responses 102
4.3 Amplitude Modulation 104
5 Common Features of Auditory Thalamic and Cortical Processing 104
5.1 Redundancy 104
6 Role of Inhibition and Synaptic Plasticity in Shaping Responses In Vivo 104
6.1 Thalamic-Evoked Cortical Inhibition 104
6.2 Sound-Evoked Cortical Inhibition 106
6.3 Transient Cortical Responses 106
6.4 Spectrotemporal Receptive Fields 107
References 107
4 Auditory Cortical Organization: Evidence for Functional Streams 112
1 Introduction 112
2 Anatomy of Nonprimary Auditory Cortex 113
2.1 Cytoarchitectonic Organization 113
2.2 Thalamocortical Projections of Nonprimary Auditory Cortex 113
2.3 Corticocortical Connections 113
3 Physiology of Nonprimary Auditory Cortex 116
3.1 Neurophysiology of Lateral Belt 116
3.1.1 Bandpass Tuning 116
3.1.2 Frequency-Modulated Tuning 117
3.1.3 Visual Analogies 117
3.2 Neurophysiology of Medial Belt 118
3.3 Neurophysiology of Rostral and Caudal Superior Temporal Gyrus 118
3.3.1 Responses to Species-Specific Communication Calls 118
3.3.2 Combination Sensitivity 118
3.4 Lateral Belt Versus Primary Auditory Cortex 119
3.5 Rostral Stream 119
3.6 Spatial Selectivity in the Caudal Belt 119
4 What and Where in Nonprimary Auditory Cortex 119
5 Beyond Classical Auditory Cortex 120
5.1 Auditory Processing in the Superior Temporal Sulcus 120
5.2 Auditory Processing in the Prefrontal Cortex 121
5.2.1 Prefrontal Auditory Object Processing: The Ventral Stream 121
5.2.2 Prefrontal Auditory Spatial Processing: The Dorsal Stream 123
5.3 Multisensory Processing in the Prefrontal Cortex 123
6 Neuroimaging Studies in Humans 123
6.1 Core and Belt Distinction in Human Auditory Cortex 123
6.2 Dual Streams in Human Auditory Cortical Processing 125
References 125
5 The Commissural Auditory System 130
1 Introduction 130
2 Structure of the Forebrain Auditory Callosal System 130
2.1 Callosal Organization Is Species Specific 130
2.2 Callosal Organization Is Modality Specific 131
2.3 Callosal Organization Varies by Cortical Area 131
2.4 Callosal Projections Are Discontinuous 133
2.5 Callosal Projections Are Layer Specific 134
2.6 Development of Callosal Projection Patterns Is Experience Dependent 135
3 Function of Auditory Callosal and Intrahemispheric Systems 135
3.1 Binaural and Spatial Responses of Auditory Cortical Neurons 135
3.2 Patterns of Binaural Input and Interaction in Auditory Cortex 136
3.3 Spatial Receptive Fields of Cortical Auditory Neurons 136
3.4 Binaural Organization of Primary Auditory Cortex 137
3.5 Binaural Responses and Patterns of Callosal and Intrahemispheric Connectivity 137
4 The Continuity of Sensation Across the Midline: The Midline Fusion Hypothesis 138
4.1 Three Sensory Systems 138
4.2 Sensory Saltation 139
5 Conclusions and Directions for Future Research 140
References 140
6 Intrinsic Connections of the Auditory Cortex 145
1 Introduction 145
2 Local Connections of Excitatory Interneurons 146
3 Local Connections of Inhibitory Interneurons 146
3.1 Interneurons Synapsing Near the Soma 147
3.2 Interneurons Synapsing on Distal Dendrites 148
3.3 Networks of Electrically Coupled Interneurons 148
4 Axon Collaterals of Pyramidal Cells 149
4.1 Layer II/III Pyramidal Cells 149
4.2 Layer V/VI Pyramidal Cells 150
5 Specificity of Interlaminar Connections 150
5.1 Layer IV Connections 150
5.2 Connections from Cells in Layers I--III 150
5.3 Connections Produced by Cells in Layers V/VI 150
6 Columnar Arrangement of Intrinsic Connections 151
6.1 Columnar Arrangement of Somata and Dendrites 151
6.2 Columnar Arrangement of Axonal Connections 152
7 Interspecies Comparisons of Connections in AI 152
7.1 Comparison of Metabolic Activity Bands in Primate Species 152
7.2 Comparison of Primate and Non-primate Species 152
8 Comparison of Connections in Core and Belt Areas 153
9 Comparison with Connections in Other Cortical Areas 153
10 Development of Intrinsic Connections 153
10.1 Molecular Mechanisms Specifying Intrinsic Connections 153
10.2 Role of Functional Activity in Specifying Intrinsic Connections 154
11 Intrinsic Connections and Functional Plasticity 154
12 Functional Role of Intrinsic Connections 154
12.1 Connections Within the Isofrequency Domain 154
12.2 Purposes of Intrinsic Connections 154
13 Future Directions 155
References 155
7 A Synthesis of Auditory Cortical Connections: Thalamocortical, Commissural and Corticocortical Systems 158
1 Introduction 159
2 Connectional Models 160
3 Comparative Framework 160
4 Distributed Organization 161
5 Auditory Cortex Connections 161
5.1 Intrinsic Projections 161
5.2 Extrinsic Input 165
5.3 Thalamocortical Projections 167
5.4 Corticocortical Inputs 168
5.5 Commissural Projections 170
6 Organizational Features 171
6.1 Modularity 171
6.2 Topography 171
6.3 Divergent Projections 173
7 Comparative Organization of Auditory Cortex 174
8 Synthesis of Auditory Cortical Connections 174
8.1 Hierarchical Models 174
9 Distributed Cortical Organization 177
9.1 Beyond Hierarchy 177
9.2 Areal Ensembles 177
9.3 Laminar Ensembles 177
10 Future Directions 178
References 178
8 Auditory Cortical Projections to the Medial Geniculate Body 182
1 General Features of the Corticothalamic System 182
2 Quantitative Comparison of Corticofugal and Afferent Input 183
3 Organization of the Medial Geniculate Complex 184
3.1 Medial Geniculate Body Parcellation 184
3.2 Descending Projections to the Auditory Thalamus 184
4 Dual Termination Patterns 184
5 Dual Cortical Origins 185
5.1 Laminar Corticothalamic Origins 185
5.2 Morphology of Auditory Corticothalamic Cells 185
6 Corticothalamic Collaterals in the Thalamic Reticular Nucleus 186
6.1 Reticular Thalamic Sensory Subdivisions 186
6.2 Laminar Origin of Corticoreticular Projections 186
7 Corticothalamic Axon Terminal Morphology 186
8 Spatial Distribution of Corticothalamic Axon Terminals 187
8.1 Nuclear Distribution 187
8.2 Corticothalamic and Thalamocortical Reciprocity 187
8.3 Layer 6 Corticothalamic Topography 188
8.4 Layer 5 Corticothalamic Projection 188
9 Comparison with Other Modalities 188
10 Ultrastructure of Corticothalamic Terminals 190
10.1 Layer 6 Corticothalamic Terminal Ultrastructure 190
10.2 Layer 5 Corticothalamic Terminal Ultrastructure 191
11 Corticothalamic Neurotransmitter Receptors 191
12 Corticothalamic Modulations in Slice Preparations 191
12.1 Thalamic Responses Following Corticothalamic Activation In Vitro 192
12.2 Indirect Corticofugal Circuitry 192
12.3 Transthalamic Control of Higher Order Areas 192
13 Corticofugal Modulation of Medial Geniculate Body Neurons 192
13.1 Auditory Cortex Activation 192
13.2 Auditory Cortex Inactivation and Thalamic Response Properties 193
14 Concluding Remarks 193
References 194
9 Descending Connections of Auditory Cortex to the Midbrain and Brain Stem 200
1 Introduction 200
2 The Corticocollicular System 203
3 The Corticobulbar System 210
3.1 Auditory Cortex Projections to the Lateral Lemniscal Nuclei 210
3.2 Auditory Cortex Projections to Superior Olivary Complex 211
3.3 Auditory Cortex Projections to Cochlear Nuclear Complex 211
4 Auditory Corticopontine System 211
5 Neuronal Source of the Descending Connections to the Midbrain and Brain Stem: Collateral Projections 211
6 Functional Significance of the Descending Connections to the Midbrain and Brain Stem 212
7 Interpretative Constraints and the Corticofugal System 214
8 Possible Functional Significance 214
9 Physiological Effects of Auditory Cortex Stimulation on the Brain Stem 215
10 Summary and General Principles Governing Auditory Corticofugal Projections 215
References 216
10 Neurochemical Organization of the Medial Geniculate Body and Auditory Cortex 220
1 Chemical Neuroanatomy of the Auditory System 221
2 Tectothalamic System 221
2.1 Glutamate and Calcium Binding Proteins: Differential Distribution 221
2.2 Gamma-Aminobutyric Acid: Local Circuitry and Extrinsic Influences 222
2.3 Cholinergic and Other Subsystems 222
3 Thalamotectal System 222
4 Thalamocortical System 222
4.1 Gamma-Aminobutyric Acid in the Auditory Thalamus 223
4.2 Auditory Thalamocortical Relations 226
5 Thalamic Reticular Nucleus 226
6 Thalamoamygdaloid System 229
7 Auditory Cortex 229
7.1 Neurochemical Convergence in Auditory Cortex 229
7.2 Layer I: Intrinsic Matrix 229
7.3 Layer II: Intracortical Refinement 232
7.4 Layer III: Thalamic to Corticocortical Transformation 235
7.5 Layer IV: Thalamic to Intrinsic Cortical Transformation 235
7.6 Layer V: Corticocortical to Corticofugal Transformation 236
7.7 Layer VI: Corticocortical to Corticothalamic Transformation 237
7.8 Nucleus Basalis and the Cholinergic Forebrain 237
7.9 Other Chemically Specific Cortical Subsystems 237
8 Intralaminar System 238
9 Corticocortical System 239
10 Commissural System 239
11 Corticofugal Systems 239
12 Dissecting Cortical Circuitry 239
13 Concluding Comments 239
14 Future Questions 240
References 240
11 Synaptic Integration in Auditory Cortex 246
1 Introduction: What Can We Learn from Synaptic Mechanisms? 246
2 Spectral Processing 246
2.1 Extent of Spectral Integration for AI Neurons 247
2.2 Mechanisms of Spectral Integration: Role of Thalamocortical Input 248
2.3 Spectral Processing by Intracortical Pathways 249
2.4 Spectral Integration: Possible Mechanisms and Functions 249
3 Temporal Processing 250
4 Intensity Processing 252
5 Spectrotemporal Interactions 253
6 Neuromodulation of Cortical Processing 254
7 Future Directions 256
References 257
12 Physiological Properties of Neurons in the Medial Geniculate Body 261
1 Introduction 261
2 Cellular Bases of Auditory Thalamic Functions 262
2.1 Connectivity of the Lemniscal and Non-lemniscal Auditory Thalamus 262
2.2 Cell Types in Medial Geniculate Body Divisions 263
2.3 Intrinsic Electrophysiological Properties of Medial Geniculate Body Cells 264
2.4 Synaptic Properties of Medial Geniculate Body Cells 265
2.5 Pharmacological and Biochemical Markers of Parallel Pathways in Medial Geniculate Body 265
3 Functional Aspects of Auditory Thalamic Sensory Processing 266
3.1 Frequency Tuning and Tonotopic Organization 266
3.1.1 Frequency Tuning 266
3.1.2 Tonotopic Organization 266
3.1.3 Intensity Tuning 267
3.1.4 Comparing Awake and Anesthetized Conditions 267
3.2 Temporal Aspects of Neuronal Responses 267
3.2.1 Discharge Pattern 267
3.2.2 Evoked Oscillations 268
3.3 Sensitivity to Directional Cues 268
3.3.1 Initial Classification of Binaural Interactions 268
3.3.2 Sensitivity to Interaural Intensity Differences 268
3.3.3 Sensitivity Revealed by Free-Field Stimulation 269
3.3.4 Sensitivity of Interaural Phase Differences 270
3.4 Corticofugal Influence 270
3.4.1 Inactivation of Auditory Cortex 270
3.4.2 Auditory Cortex Stimulation 270
3.5 Responses to Natural Stimuli 271
4 Auditory Thalamus and Integrative Function 271
4.1 State Dependent Changes 271
4.2 Post-injury Plasticity 272
4.3 Learning-Induced Plasticity 273
4.3.1 Findings Obtained During Behavioral Training 273
4.3.2 Modification of Medial Geniculate Body Frequency Tuning: A Bottom-Up Process for Cortical Plasticity? 273
4.3.3 Plasticity of Medial Geniculate Body Neurons in Fear Conditioning: Relation with Limbic Plasticity 274
5 Conclusions and Future Directions 275
5.1 Special Features of Medial Geniculate Body Compared with the Visual and Somatic Sensory Thalamus 275
5.1.1 Unique Features of Medial Geniculate Body Inhibition 275
5.1.2 Temporal Constraints 275
5.2 Future Directions: Toward Understanding Medial Geniculate Body Function 275
5.2.1 Neuromodulators 275
5.2.2 Studying the Thalamocortical System as a Whole 275
5.2.3 Using Biologically Relevant Stimuli and Natural Conditions 275
5.2.4 Studying the Waking Brain 278
5.2.5 Mapping Subcortical Structures with Non-invasive Techniques 278
References 278
13 Spectral Processing in Auditory Cortex 285
1 Introduction 285
2 Spectral Analysis of Tonal Stimuli 286
2.1 Frequency Specificity 286
2.2 Frequency Selectivity 291
2.3 Shape of Frequency Response Areas 293
2.4 Temporal Dependence of Pure-Tone Tuning 294
2.5 Inhibitory Response Areas 295
3 Cortical Frequency Channels 295
4 Static Spectral Profile Analysis 296
5 Dynamic Spectro-Temporal Profile Analysis 298
5.1 Spectro-Temporal Receptive Fields 298
5.2 STRF Differences Between Cell Classes 301
5.3 Multi-filter Spectral Analysis 302
5.4 Receptive Fields: Constancy Versus Malleability 304
5.4.1 Short-Term Changes of Receptive Fields 304
5.4.2 Long-Term Plasticity of Spectral Modulation Filters 305
6 Synaptic Mechanisms of Spectral Processing 306
6.1 Synaptic Frequency Tuning 306
6.2 Development of Synaptic Frequency Tuning 307
6.3 Plasticity of Frequency Tuning in the Adult Cortex 308
7 Conclusions and Future Directions 310
References 311
14 Temporal Coding in Auditory Cortex 319
1 Introduction 319
1.1 Temporal Structure of Sound 320
1.1.1 Human Speech and Species-Specific Animal Vocalizations 320
1.1.2 Music 320
1.2 Perception: Rhythm, Roughness, and Pitch 321
2 Coding of Stimulus Periodicity and Envelope by Single Neurons 321
2.1 Phase-Locked Responses 321
2.1.1 Quantitative Measurement of Phase-Locked Responses 322
2.1.2 Phase Locking to Carrier 323
2.1.3 Phase Locking to Stimulus Envelope 324
2.1.4 Gap Detection and Voice Onset Time Representation 325
2.2 Tonic (Sustained) Responses 326
2.3 Temporal Envelope Asymmetry 327
3 Population Coding of Temporal Sound Structures 328
3.1 Comparison Between Single-Unit, Multi-Unit, and Field Potential Measurements 328
3.2 Inter-spike-Interval Coding 329
3.3 Place Coding 329
4 Stimulus Dependence/Invariance of Temporal Coding 329
5 Temporal Coding in Different Cortical Areas 330
6 Temporal Processing in Human Auditory Cortex 331
6.1 Representation of Amplitude and Frequency Modulations 331
6.2 Voice Onset Time 331
6.3 Pitch and Melody 331
7 Synaptic Mechanisms and Modifiability of Temporal Coding 332
7.1 Role of Synaptic Depression, Integration and Inhibition 332
7.2 Modeling Temporal Processing 332
7.3 Effects of Basal Forebrain Stimulation and Learning 333
7.4 Cortical versus Subcortical Contributions 334
8 Future Perspectives 334
References 334
15 Cortical Representation of Auditory Space 339
1 Introduction 339
2 Inactivation of Auditory Cortex Induces Sound Localization Deficits 340
3 Representation of Auditory Space in the Cortex 341
3.1 Spatial Receptive Fields in Primary Auditory Cortex 341
3.2 Variations in Spatial Sensitivity Across Different Cortical Areas 344
3.3 Encoding Sound-Source Location by Single Neurons and by Neuronal Populations 346
4 Representation of Multiple Sound Sources 346
5 Dynamic Coding of Auditory Space 347
6 Concluding Remarks and Future Directions 348
References 348
16 Communication Sounds and their Cortical Representation 352
1 Introduction 352
1.1 Audiovocal Communication and the Structure of Communication Sounds 352
1.2 Methods for Characterizing the Auditory Cortex 354
1.2.1 In Vivo Electrophysiology 354
1.2.2 Metabolic Activity Mapping and the Blood Oxygen Level Signal 354
1.2.3 Optical Imaging 355
2 Auditory Cortical Fields in Representative Species 355
2.1 Mustached Bat 356
2.2 House Mouse 356
2.3 Monkeys 357
2.4 Other Mammals 357
3 Complex Sound Representation and Processing 357
3.1 Representation Within Primary Auditory Cortex 357
3.2 Representation outside Primary Auditory Cortex 360
3.2.1 Fields Anterior and Ventral to Primary Auditory Cortex 360
3.2.2 Fields Posterior to AI 360
3.3 Representation of Communication Sounds: Beyond Tonotopy 361
3.3.1 Motivation-Structure Hypothesis 361
3.3.2 Rules for Call Perception 361
3.4 Plasticity in Representation 362
4 Presumptive Information-Bearing Elements within Communication Sounds 362
4.1 Harmonic Complexity and Timbre 362
4.2 Amplitude Modulation 362
4.2.1 Rhythm 363
4.2.2 Roughness 363
4.2.3 Pitch 363
4.3 Sound Duration 363
4.4 Silent Intervals 364
4.5 Frequency-Modulated Slope and Direction 364
4.5.1 Transitions and Glides 364
4.5.2 Pitch or Tonal Contours 365
4.6 Higher Order Constructs: Syntax 365
5 Functional Specializations 365
5.1 Distributed Representations and the Number of Auditory Cortex Fields 365
5.2 Lateralization of Processing and Representations 367
5.3 Auditory Objects: Extraction of Meaning 368
6 Conclusions 368
7 Future Directions 369
References 369
17 A Semantic Concept of Auditory Cortex Function and Learning 377
1 Introduction 377
2 The Nature of Sounds 378
2.1 Sounds vs. Sound-Generating Objects and Events 378
2.2 Source Identification in Auditory Scenes 378
2.3 Statistics of Sound Properties 379
2.4 Categorization of Sound-Generating Objects and Events 379
2.5 Memory-Dependence of Sound Interpretation 379
2.6 Natural vs. Laboratory Situations 380
2.7 ''Sound Objects'' Revisited 380
2.8 Adequacy of Visual Metaphors for Audition 380
3 Representation of Sounds in Auditory Cortex 381
3.1 Sensitivities and Selectivities of Auditory Cortical Representations 381
3.2 Maps in Auditory Cortical Representations 381
4 Contrasts and Stimulus Representations 382
5 Discrimination Learning Through Local Contrast Enhancement 383
6 Problems of the Map Concept for Understanding Category Formation 385
7 The Role of Feedback in Category Formation 385
8 Polymodal and Cognitive Contingencies in Categorization 387
9 Potential Influences of Category Formation on Stimulus Representation 388
10 Conclusions 391
References 392
18 Functional Specialization in Primary and Non-primary Auditory Cortex 396
1 Introduction 396
2 Reversible Cooling Deactivation 398
3 Behavioral Double Dissociation in Auditory Cortex 399
4 Deactivation of Individual Regions in Cat Auditory Cortex 403
4.1 Tonotopically Organized Regions 403
4.2 Non-tonotopically Organized Regions 404
5 Contributions of Auditory Cortex to Sound Localization 404
6 Task-Specific Sound Localization Deficits with Cortical Deactivations 406
6.1 Left Versus Right Discriminations 407
6.2 Orienting Tasks 407
6.3 Unconditioned Orienting Tasks 407
6.4 Conditioned Avoidance Tasks 408
7 Field-Specific Contributions to Sound Localization 408
References 409
19 The Evolution of Auditory Cortex: The Core Areas 413
1 Introduction 413
2 Cortical Areas Are the Larger Subdivisions of the Cortical Sheet 414
3 The Origin of Auditory Cortex 414
4 Auditory Cortex Organization in Cats and Other Carnivores 414
5 Primate Auditory Cortex 418
6 Auditory Cortex in Rodents and Lagomorphs 421
7 Auditory Cortex Organization in Tree Shrews (Scandentia) 426
8 Auditory Cortex in Bats 426
9 Auditory Cortex in Other Mammals 428
10 Summary and Conclusions 429
10.1 Defining the Auditory Cortex 429
10..2 Core Fields of Auditory Cortex 429
10.3 Common and Unique Features in Defining Auditory Cortex 429
10.4 Bats and Other Species 429
10.5 The Future of Comparative Studies of Auditory Cortex 429
References 430
20 The Avian Auditory Pallium 434
1 Introduction 434
2 Phylogeny of the Avian and Mammalian Auditory Systems 435
3 Auditory Behavior 435
3.1 Psychophysical Studies in the Laboratory 435
3.2 Natural Auditory Behaviors 435
4 The Auditory Pallium: Culmination of the Central Auditory System 436
4.1 Ascending Auditory Pathways to the Primary Auditory Pallium 436
4.2 Subregion Connectivity: Afferent Inputs and Projections 436
4.2.1 Afferent Inputs to Pallium 436
4.2.2 Projections from Pallium 436
4.2.3 Internal Organization and Cell Types in Field L, NCM, and CM 438
4.2.4 Comparison to Mammalian Anatomy 438
4.3 Response Properties of Pallial Auditory Neurons 438
4.3.1 Tonotopy 438
4.3.2 Spectrotemporal Tuning 439
4.3.3 Songbird Selectivity for Communication Signals 439
4.3.4 Development and Plasticity 441
4.3.5 Auditory Scene Analysis 441
4.3.6 Functional Comparison to Mammalian Physiology 442
5 Interaction Between Vocal and Auditory Systems 443
6 Conclusions 444
References 444
21 Development of the Auditory Cortex 448
1 The Ontogenetic Framework 448
2 Early Cortical Development 449
2.1 Terminal Phase of Early Development: Arrival of Thalamic Afferents 450
3 Late Cortical Development 451
3.1 Cell Death in the Neocortex 451
3.2 Structural Development of the Brain and Neocortex 452
3.3 Formation of Cortical Circuits: Synaptogenesis 454
3.3.1 Synaptic Selection in the Neocortex 454
3.4 Synaptic Properties of Developing Cortical Cells 456
3.5 Functional Development in the Auditory Cortex 457
3.6 Human Functional Development 458
4 Developmental Plasticity and Sensitive Periods 459
5 Cross-modal Developmental Reorganization 460
References 461
22 Reconceptualizing the Primary Auditory Cortex: Learning, Memory and Specific Plasticity 469
1 Introduction 469
2 Scope and Approach 470
3 Levels of Analysis and Codes in the Auditory Cortex 470
3.1 Levels 470
3.2 Sensory Codes and Memory Codes 471
4 Learning, Memory, Plasticity, and the Auditory Cortex: The Foundational Period 472
4.1 Introduction 472
4.2 Is Auditory Learning Actually Perceptual Learning? 472
4.3 Learning and Plasticity in Primary Auditory Cortex 473
4.3.1 Habituation 473
4.3.2 Conditioning 473
4.4 Disinterest in Learning-Induced Auditory Cortical Plasticity 474
4.5 Limitations of Auditory Cortical Plasticity Obtained During Training Trials 474
4.5.1 State Factors 475
4.5.2 Specificity of Plasticity 475
5 Contemporary Approaches: A Synthesis of Two Disciplines 475
5.1 Auditory Neurophysiology and Learning 475
5.2 Contextual Importance: Reduction of State Factors and Extinction 476
5.3 Habituation 476
5.4 Conditioning: Initial Studies and Controls for Reactive State Confounds 477
5.5 Does the Primary Auditory Cortex Hold Memory Traces? 479
5.5.1 Introducing Memory Traces 479
5.5.2 Specificity of Frequency Plasticity 479
5.5.3 Arguments to the Contrary 480
5.5.4 Specificity of Plasticity for Other Acoustic Parameters 481
5.5.5 Working and Reference Memory 481
5.6 Auditory Imagery 482
5.7 Interim Summary: Specific Memory Traces in AI 482
5.8 Primary Auditory Cortex Lesions: Rationale, Assumptions, and Limitations 483
6 Is There an Auditory Memory Code for the Acquired Importance of Sound? 483
7 Reconceptualizing the Primary Auditory Cortex 484
7.1 Is AI only an Acoustic Analyzer with Adaptive Properties? 484
7.2 Conceptual Problem: Conflation of Analytic and Interpretative Processes 485
7.3 Empirical Problem: Beyond Learning and Memory in AI 485
7.3.1 Selective Attention 485
7.3.2 Expectancy 485
7.3.3 Concept Formation 485
7.3.4 Cross-Modality Effects 485
7.3.5 Learning Strategy 485
7.3.6 Pre-motor Processes 486
7.4 Thematic Summary 487
7.5 A Brief Note on Cerebral Cortex Functional Organization 488
7.6 Toward a New Conception of the Primary Auditory Cortex 488
7.6.1 Some Boundary Conditions 489
7.6.2 The Primary Auditory Cortex as an Auditory Problem Solver 489
8 Some Future Directions 489
8.1 Beyond the Documentation of Plasticity 490
8.2 The Contents of Auditory Perception and Memory 490
8.3 Factors that Determine Plasticity 490
8.3.1 Stimulus Factors 490
8.3.2 Training Factors 490
8.3.3 Learning Strategy 490
8.4 Functions of Plasticity 491
9 Concluding Comments 491
References 491
23 Cortical Effects of Aging and Hearing Loss 496
1 Introduction 496
2 Aging in Human Psychophysics and Physiology 496
2.1 Temporal Processing 497
2.2 Sound Localization 498
2.3 Signal Segregation 498
2.4 Interhemispheric Differences 499
2.5 Human Anatomical and Morphological Changes 499
3 Aging in Animal Behavior and Physiology 499
3.1 Anatomical and Neurotransmitter Changes with Aging 500
3.2 Comparison with Aging Effects in Subcortical Structures 501
3.3 Neural Mechanisms 502
3.4 Interventions 502
4 The Consequences of Non-ageing Hearing Losses for Auditory Cortex 503
4.1 Preservation of Cortical Response Properties in the Absence of Auditory Experience 503
4.2 Reinstating ''Auditory'' Input After Development Without Auditory Experience 504
5 Cortical Changes Following NAHL in Adult Animals with Auditory Experience 505
5.1 Changes in AI After Mild-to-Moderate NAHL 505
5.2 Changes in AI After High-Moderate and Moderate-to-Severe NAHL 506
5.3 Changes in AI After Severe and Profound NAHL 507
6 Changes in AI After NAHL in Younger Animals with Auditory Experience 508
6.1 Changes in AI After Mild-to-Moderate NAHL 508
6.2 Changes in AI After Severe and Profound NAHL 508
7 Effects of Hearing Losses on Human Cortical Responses 509
7.1 Effects in Users of Cochlear Implants 509
7.2 Hearing Loss in Adults with Auditory Experience 510
References 510
24 Corticofugal Modulation and Plasticity for Auditory Signal Processing 515
1 Introduction 515
2 Corticofugal Projections 515
3 Principles of Corticofugal Modulation 516
3.1 Corticofugal Modulation in the Frequency Domain in Bats and Rodents 517
3.1.1 Frequency-Dependent Facilitation and Inhibition and Best Frequency Shifts 517
3.1.2 Expanded and Compressed Frequency Map Reorganization 518
3.1.3 Role of Facilitation and Inhibition in Producing Two Types of Reorganization 519
3.1.4 Sharpening and Broadening of Frequency-Tuning Curves 521
3.1.5 Corticofugal Modulation of Cochlear Hair Cells 522
3.1.6 Ipsilateral Versus Contralateral Corticofugal Modulation 523
4 Multiparametric Corticofugal Modulation 524
4.1 Modulation of Duration Tuning in the Big Brown Bat 524
4.2 Modulation of Delay Tuning in the Mustached Bat 524
4.3 Modulation of Minimum Threshold in the Mouse and Bat 524
4.4 Modulation of Spatial Tuning in the Big Brown Bat 525
4.5 Frequency Map Reorganization After Cochlear Lesions 525
4.6 Non-auditory Augmentation of Corticofugal Modulatory Systems 525
4.6.1 Time Course of Frequency Shifts After Electric Stimulation and Fear Conditioning 525
4.6.2 Circuitry for Frequency Changes in Auditory Fear Conditioning 526
4.6.3 Tone-Specific BF Shifts Versus Conditioned Behavioral Responses 528
4.6.4 Auditory Memory Versus Associative Memory 528
4.6.5 Multiparametric Cholingeric and Dopaminergic Modulation 529
5 Functions of the Corticofugal System 529
5.1 Egocentric Selection in Different Species and Sensory Systems 529
5.2 Other Corticofugal Contributions 530
6 Epilogue 531
References 531
25 Auditory Evoked Potentials and Their Utility in the Assessment of Complex Sound Processing 536
1 Studying Human Auditory Cortex 536
2 Average Evoked Potentials: Definition and Classification 537
3 Middle-Latency Responses 537
4 Long-Latency Responses 537
5 Automatic Processing: Contingent Responses 538
6 Role of Attention 538
7 Neural Bases of Event-Related Potentials 539
7.1 Non-invasive Measures of Event-Related Potential Generator Localization 539
8 Invasive Measures of Evoked Potential Generator Localization 540
8.1 Generators of Specific Components 540
9 Animal Models 543
10 Development 545
11 Average Evoked Potentials in Auditory Sensory and Cognitive Neuroscience 546
11.1 Context Dependence of Auditory Cortical Activity: Electroencephalographic Modulation 546
11.2 Modulation by Sound Context 547
12 Cortical Representation of Temporal Information 549
12.1 Amplitude Modulation 549
12.2 Speech Sounds 550
13 Average Evoked Potentials in Neurological Disorders 552
14 Electroencephalography and Auditory Cortex 553
15 Future Directions 553
References 554
26 Auditory Memories and Feedback Processing for Vocal Learning 561
1 Vocal Learning and Its Evolution 561
2 The Sensory Phase of Vocal Learning 562
3 Avian Auditory and Motor (Song System) Pathways 563
3.1 Auditory Pathways 563
3.2 Song System Pathways 564
3.2.1 Auditory Input to the Song System 564
4 Auditory Memories 564
4.1 Representations of Song Memories in the Auditory System 564
4.1.1 Field L 565
4.1.2 Caudomedial Nidopallium 565
4.1.3 Caudal Mesopallium 566
4.2 Representations of Auditory Memories in the Song System 566
5 Song Processing in Females 567
6 Auditory Processing of Feedback in the Song System 568
6.1 Maintenance of Adult Song 568
6.2 Role of the AFP in Maintenance of Adult Song 569
6.3 On-Line Processing of Auditory Feedback in the Song System 569
7 Sleep and Auditory Processing 570
8 Conclusions and Future Directions 571
References 572
27 Population Dynamics in Auditory Cortex: Optical Imaging 576
1 Introduction 576
2 Methodology for Optical Imaging 577
2.1 Sources of Intrinsic Signals 577
2.2 Wavelength and the Capillary System 577
2.3 Fourier-Based Imaging Techniques 577
2.4 Optical Imaging Using Voltage-Sensitive Dyes 578
2.4.1 In Vivo and In Vitro Optical Imaging 578
2.4.2 Depth Dependency of the Optical Signal and Spatial Resolution 579
2.4.3 Recording Layers and the Signal Source 579
2.4.4 Noise Canceling 579
3 Analysis of Auditory Representations by Optical Imaging 580
3.1 Frequency Representations 580
3.2 Multiple Auditory Areas 581
4 Beyond Frequency Representation 583
4.1 Intensity Representation 583
4.2 Periodicity Representation 583
4.3 Binaural Organization 583
4.4 Complex Sounds and Animal Vocalization 584
4.5 Auditory Cortex Plasticity 584
4.5.1 Cochlear Implants and Cochlear Implant Plasticity 584
4.5.2 Cross-Modal Plasticity and Rewiring in AI 586
5 Primary Auditory Cortex Organization: Evidence for Multiple Functional Maps? 587
6 Visualization of Dynamic Response Properties and Synaptic Mechanisms of Primary Auditory Cortex 587
6.1 Visualization of Dynamic Response Properties 587
6.2 The Layer-Specific Spread of Activity: Neural Circuitry In and Between Cortical Layers 588
6.3 Synaptic Mechanisms of Vertical and Horizontal Spread of Activity 589
7 Comparison Between Intrinsic and Voltage-Sensitive Dye Signals 589
8 Outlook 589
8.1 Optical Imaging: Complementary or Confirmatory? 589
8.2 What Electrophysiology Can Learn From Optical Imaging and Vice Versa 590
8.3 Advanced Optical Recording Techniques 591
References 591
28 From Tones to Speech: Magnetoencephalographic Studies 595
1 Basics of Magnetoencephalography 595
1.1 From Neural Currents to the Magnetic Fields: The Forward Problem 595
1.2 Interpretation of Magnetic Fields 596
1.3 Estimation of a Single Current Dipole 597
1.4 Multi-dipole Approaches 597
1.5 Synthetic Sensors: Beamformers 598
1.6 Spectro-Temporal Approaches: Peaks, Peak Activation Sequences, Oscillations, Phase 598
1.7 Relation to Other Techniques: Unique Contributions of Magnetoencephalography 598
2 Auditory Evoked Magnetic Fields: Basic Phenomena 599
2.1 On-Response, Sustained Field, and Off-Response 599
2.2 Waves P50m, N100m, and P200m 600
2.3 Transition Responses 600
2.4 Mismatch Negativity 601
2.5 Faster Transient Responses 602
2.6 Steady-State Responses 602
3 Domains of Magnetoencephalographic Research in Auditory Cognition 603
3.1 The Construction of Elementary Auditory Attributes 604
3.2 Elementary Operations in Auditory Cortex 604
3.3 Speech Processing: Overview 605
3.4 Vowels, Consonants, and Syllables 606
3.5 Words 607
3.6 Connected Speech 608
4 Magnetoelectroencephalographic Studies on the Structure of Human Auditory Cortex 608
4.1 Localization of Primary Auditory Cortex 609
4.2 Tonotopic Maps 609
4.3 Dipoles Representing Multiple Cortical Sources 609
5 Conclusions and Perspectives 610
References 610
29 The Relationship of Auditory Cortical Activity to PerceptionINTbreak and Behavior
1 Introduction 614
2 Processing of Basic Sound Features 615
2.1 Methods for Relating Neural Activity to Perception 615
2.2 Analysis and Representation of Complex Sounds in the Auditory Cortex 616
2.2.1 Amplitude Modulation 617
2.2.2 Cortical Spectrotemporal Response Fields, Timbre, and Speech Perception 618
2.2.3 Pitch Perception and Auditory Cortex 619
3 Perception of Stream Segregation 620
4 Perceptual Fill-in in Auditory Cortex 620
5 The Effects of Learning, Behavior, and Motivation in Auditory Cortical Responses 621
5.1 Long-Term Versus Short-Term Plasticity in Cortex 622
5.2 The Effects of Task Engagement 623
5.3 Reward, Value, and Activity 625
5.4 Intermodal Selective Attention 626
5.5 Intermodal Predictability and Cortical Responses 627
5.6 Intramodal Selective Attention 628
5.7 Activity Related to Sensory-Motor Associations 628
5.8 Memory, Comparison, or Delay Activity 629
5.9 Non-auditory Activity: Sensory and Motor Related 629
5.10 Decision- or Choice-Related Activity 629
5.11 Conclusion on Non-auditory Influences in Auditory Cortex 631
References 632
30 Processing Strategies in Auditory Cortex: Comparison with Other Sensory Modalities 639
1 Common Organizational Themes in Sensory Systems 639
2 The Standard Model and Auditory Cortex 640
2.1 Emergent Properties of Single Neurons in Primary Auditory Cortex 640
2.2 Maps in Primary Auditory Cortex 643
2.3 Multiple Auditory Areas and Functional Streams 644
2.4 Dynamic Processing of Information 645
2.5 Summary and Interpretation 646
3 The Road to Perception 647
References 648
31 Cortical Speech and Music Processes Revealed by FunctionalINTbreak Neuroimaging
1 Introduction 653
1.1 Human Auditory Cortex: Specializations for Music and Speech 653
1.2 Pathways and Hierarchies 653
1.3 Pitch and Music: Low-Level Specializations Versus Higher Order Distributed Mechanisms 654
1.4 Tonotopy 655
1.5 The Cortical Pitch-Sensitive Area 655
1.6 Mechanism of Pitch Extraction 657
1.7 Auditory Stream Segregation 658
1.8 Effects of Attention on Auditory Cortex Activation 659
1.9 Gain Control for Task-Relevant Areas 660
1.10 Auditory Imagery 661
1.11 Involuntary Capture of Auditory Attention 661
1.12 Pitch Patterns: Melodies 661
2 Speech-Related Functions 664
2.1 Low-Level Specializations Versus Higher Order Distributed Mechanisms 664
2.1.1 Speech: Left Auditory Cortex Specialization 665
2.1.2 Speech: Higher Order Constraints 665
2.1.3 Speech: Interactions Between Auditory and Other Cortices 666
2.2 Voice 667
3 Summary and Conclusions 668
References 668
32 Toward a Synthesis of Cellular Auditory Forebrain FunctionalINTbreak Organization
1 Auditory Forebrain Organization 674
1.1 Auditory Forebrain Serial Processing 674
1.2 Topography of Projections 674
1.3 Scaling the Projection Systems 675
1.4 Parallel Descending Pathways 675
1.5 Subdivisions of Auditory Cortex 675
2 The Problem of Interneurons 675
3 A Case for Comparative Neuroscience 676
4 Neuropil: A Synaptic Nexus 677
5 Auditory Forebrain Maps: Topography in a State of Flux 677
6 Conclusions 678
References 678
Index 682