Nerve Chips: Bridging Mind and Machine

Alik WidgeMEMS LaboratoryNeurobotics LaboratoryCarnegie Mellon University

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…

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?

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

Nerve Chips: Why?

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

Y Matsuoka, 2001P Heiduschka and S Thanos, 1998

Replace missing sensory data

Route them around dead or damaged tissue

But even better yet….

Nerve Chips: Why? …expand human capabilities to the limits of human

imagination

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,

Alzheimer’s, Parkinson’s, 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?

Neuroanatomy in a Nutshell

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

Don’t transmit current to non-target cells Don’t 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

How Do We Do It? (1)

Nerve Cuff Flexible cuff wrapped

around a whole nerve Mechanically stable Not very selective Causes muscle fatigue Can’t use in brain Still a popular method

because it’s simple and stable

P Heiduschka and S Thanos, 1998

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

How Do We Do It? (3)

Microelectrode Array Array of tiny conducting

spikes Can stick it anywhere in

the nervous system Can’t 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

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)

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

What Can We Do Now? (2)

What Can We Do Now? (2)

Videos of FES Application: Correcting Foot Drop

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

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?

What’s 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

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…

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 haven’t thought of yet

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