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Electrode types and connections to excitable tissue

Electrode types and connections to excitable tissue. Based on chapter 2 of Neural Engineering, Bin He. Interfaces with the nervous system. Majority: electrical Other ways: chemical (ISE), magnetic Ideas?. How to stimulate?. Cogan, Ann Rev Biomed Eng, 2008.

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Electrode types and connections to excitable tissue

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  1. Electrode types and connections to excitable tissue Based on chapter 2 of Neural Engineering, Bin He

  2. Interfaces with the nervous system • Majority: electrical • Other ways: chemical (ISE), magnetic • Ideas?

  3. How to stimulate? Cogan, Ann Rev Biomed Eng, 2008. Two approaches: current controlled or voltage controlled.

  4. Mechanisms of charge transfer • Faradaic: oxidation and reaction • Capacitive

  5. High pass electrodes • Electrodes are either polarizable (capacitor-like) or non-polarizable (resistor-like). • Usual metal electrodes: polarizable (high pass)

  6. Needle electrodes • Also known as depth electrodes • Used for cortex when micromachined • Problem: can’t access several layers

  7. Slanted array (Utah) W Rutten, Ann Rev Biomed Eng 2002

  8. Verifying placement and tissue damage after chronic implants • Histological methods • Inflammatory measures • Electrochemical performance

  9. Challenges • How to measure damage without damaging the tissue even more • How to miniaturize the electrode without losing signal

  10. Insulated leads Contacts Ag/AgCl electrodes Ag/AgCl electrodes Contacts Base (b) Base Insulated leads (a) Tines Exposed tip Base (c) Electrode Arrays Examples of microfabricated electrode arrays. (a) One-dimensional plunge electrode array, (b) Two-dimensional array, and (c) Three-dimensional array

  11. Multielectrode Neural Recording and stimulation (example) Reference : http://www.cyberkineticsinc.com/technology.htm Reference : http://www.nottingham.ac.uk/neuronal-networks/mmep.htm

  12. Horizontal needle / shank probes • Potential fix for depth problem • Active probes • Wireless implants • CMOS-compatible processing

  13. Low pass (or non-polarizableelectrodes): traditional example: Ag/AgCl

  14. Challenges • Ag/AgCl is toxic. • Most electrodes are not only high pass (neither only low pass). • Interfaces are nonlinear • Biocompatibility issues • Miniaturization (“nano-rization”?) brings other parameters to the interface

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