The use of neural implants for stimulation and recording show excellent promise in restoring certain functions to the central nervous system; and neuroprostheses remains one of the most important tools of neuroscientists for the elucidation of the brain's function. Ailments such as Parkinson's disease, obesity, blindness, and epilepsy are being studied from this angle. Development of better electrodes for recording and stimulation is therefore critical to ensure continuing progress in this field. This book addresses one of the main clinical complications with the use of electrodes, namely the reaction of the neurological tissue in the immediate vicinity of an implanted device. The authors describe new techniques for assessing this phenomenon, as well as new microfabrication techniques to impede the inflammatory response of the brain. Inflammation can adversely effect these devices, limiting their lifetime and reducing their effectiveness. The measurement protocols and improved fabrication protocols described within these pages will become standard tools in the future of neuroprostheses. The author holds two U.S. patents on microassembly and is also a Review Editor for Frontiers in Neuroengineering.
Introduction Scope Problem Statement: The Tissue Reaction to Implanted Neuroprostheses The Initial Response The Sustained Response Effect of Tissue Reaction on Recording and Stimulation Tissue Reaction Reduction Methods Literature Review Thin-Film Microelectrode Technology Electrical Impedance Spectroscopy Controlled Release Polymers Technology Position With Respect to State of the Art Research Objectives Limitations Structure References Microfabrication Techniques for Neuroprostheses Introduction Microelectrode Arrays Microfabrication Techniques Device Packaging Electrical Characterization Microfluidic Channels Device Results Conclusion Neural Recording and Stimulation Introduction The Neurophysiological Basis of Recording Detection of Biopotentials Scaling of Electrodes and Noise The Neurophysiological Basis of Stimulation Applications of Neural Recording The Somatosensory Cortex Chronic Hippocampus Recordings Chronic Auditory Cortex Recordings Applications of Neural Stimulation Cochlear and Modiolus Stimulation Retinal Stimulation Conclusion References in vivo Electrical Impedance Spectroscopy Introduction Materials and Methods Implantable Microelectrode Array Fabrication Electrode-Tissue Interface Modelling Peak Resistance Frequency Method Simulation Animal Implantation Procedure in vivo Electrical Impedance Spectroscopy Histology Results in vivo Electrical Impedance Spectroscopy Histology Discussion Conclusion References Controlled Release Drug Coatings Introduction Materials and Methods Microelectrode Array Fabrication Nanoparticle-PEO Coating Synthesis Implantation in vivo Impedance Measurements Histology Results Nanoparticle-PEO Coating Synthesis in vivo Impedance Comparison Qualitative Histological Comparison Discussion Conclusion References Conclusion Summary of Main Results Significance of Contribution to Knowledge Future Perspectives References