Neurobionics

LIST OF CONTRIBUTORS xv

PREFACE xvii

PART I FUNDAMENTALS OF NEURAL PROSTHESES 1

1 The Historical Foundations of Bionics 3
N. Donaldson and G.S. Brindley

1.1 Bionics Past and Future 3

1.2 History in 1973 5

1.2.1 Biomaterials 5

1.2.2 Nerve stimulation and recording 6

1.2.3 Transistors 8

1.2.4 Conclusion 9

1.3 Anaesthesia 9

1.4 Aseptic Surgery 10

1.5 Clinical Observation and Experiments 10

1.6 Hermetic Packages 13

1.6.1 Vacuum methods 14

1.6.2 Welding 15

1.6.3 Glass 15

1.6.4 Glass ceramics and solder glasses 16

1.6.5 Ceramics 18

1.6.6 Microcircuit technologies 19

1.6.7 Leak testing 20

1.7 Encapsulation (Electrical Insulation) 20

1.7.1 Insulation 20

1.7.2 Underwater insulation 21

1.7.3 Silicones 21

1.7.4 Primers 24

1.8 Early Implanted Devices 27

1.9 Afterword 29

References 35

2 Development of Stable Long-term Electrode Tissue Interfaces for Recording and Stimulation 38
J. Schouenborg

2.1 Introduction 38

2.2 Tissue Responses in the Brain to an Implanted Foreign Body 39

2.2.1 Acute tissue responses 39

2.2.2 Chronic tissue responses 40

2.2.3 On the importance of physiological conditions 40

2.3 Brain Computer Interfaces (BCI) - State-of-the-Art 41

2.4 Biocompatibility of BCI - on the Importance of Mechanical Compliance 42

2.5 Novel Electrode Constructs and Implantation Procedures 45

2.5.1 Methods to implant ultraflexible electrodes 45

2.5.2 Surface configurations 46

2.5.3 Matrix embedded electrodes 47

2.5.4 Electrode arrays encorporating drugs 49

2.6 Concluding Remarks 50

Acknowledgements 51

References 51

3 Electrochemical Principles of Safe Charge Injection 55
S.F. Cogan, D.J. Garrett, and R.A. Green

3.1 Introduction 55

3.2 Charge Injection Requirements 56

3.2.1 Stimulation levels for functional responses 56

3.2.2 Tissue damage thresholds 56

3.2.3 Charge injection processes 58

3.2.4 Capacitive charge injection 58

3.2.5 Faradaic charge injection 60

3.2.6 Stimulation waveforms 61

3.2.7 Voltage transient analysis 63

3.3 Electrode Materials 70

3.3.1 Non-noble metal electrodes 70

3.3.2 Noble metals 70

3.3.3 High surface area capacitor electrodes 70

3.3.4 Three-dimensional noble metal oxide films 71

3.4 Factors Influencing Electrode Reversibility 71

3.4.1 In vivo versus saline charge injection limits 71

3.4.2 Degradation mechanisms and irreversible reactions 72

3.5 Emerging Electrode Materials 73

3.5.1 Intrinsically conductive polymers 73

3.5.2 Carbon nanotubes and conductive diamond 76

3.6 Conclusion 80

References 80

4 Principles of Recording from and Electrical Stimulation of Neural Tissue 89
J.B. Fallon and P.M. Carter

4.1 Introduction 89

4.2 Anatomy and Physiology of Neural Tissue 90

4.2.1 Active neurons 91

4.3 Physiological Principles of Recording from Neural Tissue 94

4.3.1 Theory of recording 94

4.3.2 Recording electrodes 95

4.3.3 Amplification 98

4.3.4 Imaging 100

4.4 Principles of Stimulation of Neural Tissue 101

4.4.1 Introduction 101

4.4.2 Principles of neural stimulator design 101

4.4.3 Modelling nerve stimulation 104

4.4.4 The activating function 106

4.4.5 Properties of nerves under electrical stimulation 107

4.5 Safety of Electrical Stimulation 110

4.5.1 Safe stimulation limits 110

4.5.2 Metabolic stress 112

4.5.3 Electrochemical stress 114

4.6 Conclusion 117

References 117

PART II DEVICE DESIGN AND DEVELOPMENT 121

5 Wireless Neurotechnology for Neural Prostheses 123
A. Nurmikko, D. Borton, and M. Yin

5.1 Introduction 123

5.2 Rationale and Overview of Technical Challenges Associated with Wireless Neuroelectronic Interfaces 126

5.3 Wireless Brain Interfaces Require Specialized Microelectronics 129

5.3.1 Lessons learned from cabled neural interfaces 129

5.3.2 Special demands for compact wireless neural interfaces 130

5.4 Illustrative Microsystems for High Data Rate Wireless Brain Interfaces in Primates 133

5.5 Power Supply and Management for Wireless Neural Interfaces 140

5.6 Packaging and Challenges in Hermetic Sealing 143

5.7 Deployment of High Data Rate Wireless Recording in Freely Moving Large Animals 146

5.7.1 Sample Case A: Implant in freely moving minipigs in home cage 147

5.7.2 Sample Case B: Implant in freely moving non-human primate in home cage 148

5.7.3 Case C: External head mounted wireless neurosensory in freely moving non-human primates 149

5.8 Summary and Prospects for High Data Rate Brain Interfaces for Neural Prostheses 153

Acknowledgements 157

References 157

6 Preclinical testing of Neural Prostheses 162
D. McCreery

6.1 Introduction 162

6.2 Biocompatibility Testing of Neural Implants 163

6.3 Testing for Mechanical and Electrical Integrity 165

6.4 In vitro Accelerated Testing and Accelerated Aging of Neural Implants 166

6.5 In vivo Testing of Neural Prostheses 171

6.6 Conclusion 181

References 182

PART III CLINICAL APPLICATIONS 187

7 Auditory and Visual Neural Prostheses 189
R.K. Shepherd, P.M. Seligman, and M.N. Shivdasani

7.1 Introduction 189

7.2 Auditory Prostheses 190

7.2.1 The auditory system 190

7.2.2 Hearing loss 191

7.2.3 Cochlear implants 191

7.2.4 Central auditory prostheses 195

7.2.5 Combined electric and acoustic stimulation 198

7.2.6 Bilateral cochlear implants 198

7.2.7 Future directions 199

7.3 Visual Prostheses 199

7.3.1 The visual system 199

7.3.2 Vision loss 201

7.3.3 Retinal prostheses 201

7.3.4 Central visual prostheses 204

7.3.5 Perceptual effects of visual prostheses 204

7.3.6 Future directions 206

7.4 Sensory Prostheses and Brain Plasticity 206

7.5 Conclusions 207

Acknowledgements 207

References 207

8 Neurobionics: Treatments for Disorders of the Central Nervous System 213
H. McDermott

8.1 Introduction 213

8.2 Psychiatric Conditions 215

8.2.1 Obsessive-compulsive disorder 215

8.2.2 Major depression 218

8.3 Movement Disorders 219

8.3.1 Essential Tremor 219

8.3.2 Parkinson's disease 219

8.3.3 Dystonia 220

8.3.4 Tourette's syndrome 221

8.4 Epilepsy 221

8.5 Pain 223

8.6 Future directions 223

Acknowledgements 227

References 227

9 Brain Computer Interfaces 231
D.M. Brandman and L.R. Hochberg

9.1 Introduction 231

9.2 Motor Physiology 232

9.2.1 Neurons are the fundamental unit of the brain 232

9.2.2 Movement occurs through coordinated activity between multiple regions of the nervous system 233

9.2.3 Motor cortex: a first source for iBCI signals 234

9.2.4 The parietal cortex is implicated in spatial coordination 237

9.2.5 The premotor and supplementary motor cortices are engaged in movement goals 237

9.2.6 Functional brain organization is constantly changing 238

9.2.7 Section summary 238

9.3 The Clinical Population for Brain Computer Interfaces 239

9.3.1 Paralysis may result from damage to the motor system 239

9.3.2 Individuals with spinal cord injuries develop motor impairments that may impact hand function 240

9.3.3 Individuals with LIS develop motor impairment that impacts communication 241

9.4 BCI Modalities 242

9.4.1 Other neural activity-based signals for BCI devices 244

9.4.2 Electrodes placed in the cortex record action potentials from neurons 245

9.4.3 Raw voltage signals are processed into spikes 246

9.5 BCI Decoding and Applications 247

9.5.1 BCI decoders convert neural information into control of devices 248

9.5.2 BCI decoders allow for the control of prosthetic devices 249

9.6 Future Directions 252

9.6.1 Scientific and engineering directions for developing BCI technology 253

9.6.2 Clinical directions for development of BCI technology 254

9.7 Conclusion 255

References 255

PART IV COMMERCIAL AND ETHICAL CONSIDERATIONS 265

10 Taking a Device to Market: Regulatory and Commercial Issues 267
J.L. Parker

10.1 Introduction 267

10.2 Basic Research 268

10.3 Preclinical Development 285

10.4 Clinical Trials and Approval to Sell 285

10.5 Building a Business not a Product 289

10.6 Conclusions 291

References 292

Webliography 292

11 Ethical Considerations in the Development of Neural Prostheses 294
F.J. Lane, K.P. Nitsch, and Marcia Scherer

11.1 Introduction 294

11.2 Individuals with Disabilities and Technology Development 295

11.2.1 Assistive technology in the context of disability 295

11.2.2 International classification of functioning, disability and health 295

11.2.3 "Nothing About Us, Without Us" 297

11.2.4 Matching Person and Technology: applications to neural prosthesis development 299

11.2.5 Disability culture: the cochlear implant 301

11.3 Ethical Principles of Biomedical Research 301

11.3.1 Principles of biomedical ethics 302

11.3.2 Informed consent in clinical research trials 306

11.3.3 Information and informed consent 306

11.3.4 The process of obtaining informed consent 307

11.3.5 Decision-making 308

11.3.6 Influence of culture and country 308

11.3.7 What information is material? 308

11.3.8 Restoration versus enhancement and mental change 313

11.4 Conclusions 314

References 315

Appendix: Examples of Companies Developing and/or Marketing

Bionic Devices 319

Index 327