Nerve Chips: Bridging Mind and Machine

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Nerve Chips Bridging Mind and Machine
Alik Widge MEMS Laboratory Neurobotics
Laboratory Carnegie Mellon University
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Your Humble Speaker

• Dartmouth Class of 1999
• Double major, computer science/cognitive science
• Inspired by ENGS007, Fall 1995
• M.D./Ph.D. Program, University of Pittsburgh
• 2 years med school
• 3 years grad school
• 2 more years med school
• And then residency

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Roadmap

• The topic interfaces between the nervous system
  and electronic devices
• Why?
• What could they do for us?
• Do we really need that?
• How?
• What problems do we have to solve?
• What techniques have been tried?
• What will we do next?

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Nerve Chips Why?

• What could we do if we could tap into neural
  signals?

• Route them around dead or damaged tissue

• Control artificial limbs and organs (or anything
  else that can be run by a computer)

• Replace missing sensory data

• But even better yet.

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Nerve Chips Why?

• expand human capabilities to the limits of human
  imagination

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Do We Really Need That?

• Neurological disorders cost 250 billion/yr in
  USA
• Acute care, rehab, inability to work, long-term
  care
• Stroke, injuries, birth defects, diabetes,
  Alzheimers, Parkinsons, multiple sclerosis
• No real cure for any of these
• Prosthetics exist, but hard to control
• No good sensory prosthetics (except hearing)
• Would you like to
• see with better accuracy, even in the dark?
• control your environment with a thought?
• experience otherwise-impossible sensations?

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Neuroanatomy in a Nutshell
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What Do We Have to Do?

• Get our interface into the body
• Keep the body from attacking and rejecting the
  chip
• Get close to the target nerve cells
• Transmit electrical current to the targets
• Dont transmit current to non-target cells
• Dont harm the nerve with too much current
• Record signals from the targets
• Try to separate out the voices of single cells
• Do all this to thousands of cells at the same
  time
• Adapt to the body changing over time

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How Do We Do It? (1)

• Nerve Cuff
• Flexible cuff wrapped around a whole nerve
• Mechanically stable
• Not very selective
• Causes muscle fatigue
• Cant use in brain
• Still a popular method because its simple and
  stable

P Heiduschka and S Thanos, 1998
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How Do We Do It? (2)

• Sieve Electrode
• Axons of a cut nerve regenerate through holes in
  silicon chip
• Lets us talk to individual axons
• We either have to wait for a nerve to get cut or
  cut it ourselves
• Not in the clinic yet, but soon

L Wallman et al., 1999
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How Do We Do It? (3)

• Microelectrode Array
• Array of tiny conducting spikes
• Can stick it anywhere in the nervous system
• Cant be sure every spike will hit a cell
• Can damage tissue
• Some clinical trials ongoing
• Versions of this let you do some semi-cool things
  with animals

PJ Rousche and RA Normann, 1998
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What Can We Do Now? (1)

• Cochlear Implants (hearing prosthesis)
• Pick up speech sounds with a microphone
• Filter digitally to reduce noise
• Pass to electrode array in cochlea (inner ear)

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What Can We Do Now? (2)

• Functional Electrical Stimulation (FES)
• Electrical stimulators similar to nerve cuff
• Implant near or inside key muscles
• Stimulation controlled by patient commands
  (remote control device)
• Coordinated stimulation programs to produce hand
  grasp, walking, etc.
• Can also trigger stimulation from sensors

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What Can We Do Now? (2)
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What Can We Do Now? (2)

• Videos of FES Application Correcting Foot Drop

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What Can We Do Now? (3)

• Visual prosthesis
• Camera on glasses
• Video sent to belt-pack computer for processing
• 10x10 electrode array on the surface of visual
  cortex
• Actual result 3-5 specks of light (phosphenes)
• Can read big text, navigate in some environments

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What Can We Do Now? (4)

• Multielectrode arrays to control animal behavior
• RoboRat (SUNY)
• Electrodes in whisker part of brain indicate
  direction
• Electrodes in pleasure center reward for
  correct behavior
• RoboRoach (Tokyo University)
• Antennae replaced by electrode
• Note large electronic backpack required for each
  case
• Effect wears off as animal adapts to the stimuli
• Any social/ethical implications?

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Whats Still Missing?

• All of these still use pretty big currents
• Hurts the cells, rapidly fatigues the muscles if
  stimulating them directly
• Need to be talking to a lot more cells to get
  true biological precision and resolution
• Only one (sieve electrode) is really specific for
  individual cells
• Can always use more mechanical stability and
  biocompatibility

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The Next Step?

• Make a chip that has living neurons built into it
• Use those living cells as your connection to the
  patient
• Nothing is better at talking to neurons than
  other neurons

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How Do We Get There?

• Nanotechnology design of new impossible
  materials
• Electrode coatings that contain brain molecules,
  trick cells into acting like electrode is part
  of brain
• Polymer chains that can enter the cell
• Conductive polymer chains that place your
  electrode inside a cell without hurting it
• Components that self-assemble through chemical
  forces
• Other crazy stuff I havent thought of yet

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Thanks

• Advisors
• Kaigham Gabriel (ECE, Robotics)
• Yoky Matsuoka (MechE, Robotics)
• Victor Weedn (MBIC)
• Sources of Money
• NIH training grant T32N507433-03
• Department of the Army (NDSEG Fellowship)
• Paralyzed Veterans of America
• Inspiration
• Dr. Joe Rosen
• You