Download Introduction to Machine Intelligence

Neuroprosthetics
Week 1
Introduction
Contact
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Kevin Warwick
Room 171
Ext. 8210
[email protected]
www.kevinwarwick.com
What is a Neuroprosthetic?
- Traditional Definition
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It is a device which replaces nerve function lost as a
result of disease or injury.
The neuroprosthetic can act as a bridge between
functioning elements of the nervous system and nerves
over which control has been lost.
Can be used in the spinal cord to allow standing in
paraplegics.
Can be used to restore hand and upper limb movement
in Tetraplegics.
What is a Neuroprosthetic?
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A neuroprosthetic may act as a bridge
between the nervous system and a
physical prosthesis.
This can be the case in upper limb
replacement for amputees.
What is a Neuroprosthetic?
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Intelligent Hand Prosthesis
What is a Neuroprosthetic?
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A neuroprosthetic can augment or replace
damaged or destroyed sensory input pathways.
It records and processes inputs from outside the
body and transmits information to the sensory
nerves for interpretation by the brain.
Examples: Cochlear implant to restore hearing,
retinal cortex prostheses for restoring vision,
extra sensory input.
Nerve Interaction
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Common component is the need to interact
directly with nerves.
System must collect signals from nerves and/or
generate signals on nerves.
Interaction may be with individual nerve cells
and fibres or with nerve trunks containing
hundreds to millions of axons.
Must understand and speak the language of the
nervous system.
The language changes as the signalling
requirements change – e.g. auditory and optic
nerves very different.
Potential Impact
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Subject is in its infancy.
Could help extend lifespan, alter
workforce, assist healthcare.
Could lessen physical and psychological
impact of injury or disease.
Potential to extend and enhance human
capabilities – Cyborgs.
Ethical questions – Therapy and
Enhancement.
Uses and potential uses ?
Uses +
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Cochlear, retinal, optic nerve
Nerve stimulation for foot drop.
Sacral nerve stimulation to prevent/control
shitting.
Artificial genitourinary sphincter to control sexual
activity!!
Nerve stimulator for long term artificial
respiration.
Pain control via spinal cord.
Chronic Deep brain stimulation.
From I,Cyborg page 306
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“The human brain and spinal cord are linking structures
that can be changed through stimulation. All the
disabilities that spinal cord injured patients have arise
from disordered nerve function. Potential benefits of the
use of implant technology include:”
Re-education of the brain
Prevention of spinal deformity
Treatment of pain
Assisting bladder emptying
Improving bowel function
From I,Cyborg page 306
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Treatment of spasticity
Improvement of respiratory function
Reduction of cardiovascular maleffects
Prevention of pressure sores
Improvement/restoration of sexual function
Improved mobility
Improved activities of daily living
Evolution of neuroprosthetics
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Early experimentation
Key tools
First successes
Rapid expansion
Experimentation
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18th Century – Luigi Galvani contracted frog’s
muscles, Allesandro Volta connected a battery to
his ear for an aural sensation.
1934 – first electronic hearing aid
1957 – first cochlear implant (first successful
commercial product not until 1980)
1961 – first motor prosthesis
2000 – tremor control for Parkinson’s
Key tools
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1947/63 – transistor and integrated circuit developed –
particularly useful as an amplifier
1952 – Hodgkin and Huxley’s model of neuron behaviour
(based on squid neurons) – action potentials
1971 – microprocessor allowed rapid processing of
electrical signals
1977 – VLSI provided transistors the size of a neuron
1981 – first (IBM) pc allowed experimentation, modelling
and control
1990’s – scanning tunnel microscope enabled visual
exploration
First successes
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1957 – first cochlear implant by Djourno and Eyries –
consisted of electrodes placed in the auditory nerve,
which were stimulated at different pulse rates
1970s – clinical trials begun in USA
1961 – first motor prosthesis for foot drop in hemiplegics
1980s – Functional Electrical Stimulation (FES) of motor
nerves and muscles shown to be valid
1990s – neural prostheses developed (trialled) for
standing and for upper limbs
1990s – urinary incontinence systems trialled
Rapid expansion
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Last 10 years has seen an incredible growth in
the field
1998 – bladder controller commercially available
2000 – middle ear implant and auditory
brainstem implant
2001 – self-contained heart replacement and
sub-retinal tests
2002 – first implant tests on a healthy volunteer
– enhancements!
How do neurons communicate ?
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Before talking to nerves and neurons it is important to
know how they talk to each other.
Monitor signals transmitted to a stimulus and correlate
signal features with stimulus information.
Most nerves communicate via Action Potentials – these
are complex signals generated by ion movements across
neuronal membranes.
Recording devices must intercept voltages and ionic
currents.
Implementing such a device is complicated because of
the micrometer scale of neurons and the small changes
(millivolts at most) in membrane potentials – all in the
presence of noise!
How do we communicate with
neurons ?
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We must manipulate voltages and inject currents to
make ourselves heard by the correct cell group without
damaging either cells or surroundings.
This is ongoing research – lots we don’t know yet.
Impaling a cell with an electrode is direct but the cell
may well die as a result.
Key issues are: 1. amplitude of stimulating signal, 2.
duration and polarity of the signal, 3. spatial selectivity.
Balanced biphasic charge best represents natural ionic
currents, but how can this be delivered.
Questions: surface area, conductivity, geometry,
materials, architecture, power requirements.
Implant Durability
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System must operate successfully for extended
periods in a hostile environment.
Device must be palatable (or invisible) to the
natural defence mechanisms of the body.
A number of materials have been identified as
being “safe”. They can perform the basic
functions required from carrying electrical
charge to providing insulation.
Long term effectiveness also depends on wound
healing. Encapsulation increases the distance
between implant and cells. Implant movement
can be detrimental.
Course Structure
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Week 2 – Implant Technologies
Week 3 – Neuron modelling
Week 4 – Stimulating/recording nerves
Week 5 – Design issues
Week 6 – Cochlear implants
Week 7 – Visual Neuroprostheses
Week 8 – Motor Prostheses
Week 9 – Emerging Technologies
TBA – Mark on our experimentation