restoring communication and mobility - uk … - biomedical...restoring communication and mobility...
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Restoring Communicationand Mobility
What are they?› Artificial devices connected to the body that substitute, restore or
supplement a sensory, cognitive, or motive function of the nervous system that has been damaged or lost due to disease or injury Implantable neural stimulators that provide therapy based on
analyzed neural signals› Designed to provide disabled individuals the ability to control their
own bodies› These devices intend to improve the quality of life for those with
disabilities
General idea behind neural prosthetics?› Accurately probing and recording the electrical signals in the brain
helps us to better understand the relationship among a local population of neurons that are responsible for a specific function
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Why we need it› Pain management Deep brain stimulation for epilepsy, depression,
Parkinson’s, chronic pain, etc.
› Restore sensory function Cochlear implant Retinal prosthesis
› Restore cognitive function Hippocampal prosthesis
› Restore motor function Brain Computer Interface (BCI) for controlling external
devices
Depending on condition to be treated, stimulating electrodes are implanted in certain areas of the brain
Alleviates symptoms such as tremor, rigidity, stiffness, slowed movement, walking problems
Predict/detect epileptic seizures and use feedback to stimulate pre-ictal/ictal regions of the brain
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External: Microphone, Sound Processor, Transmitter
Internal: Receiver, Processor,Stimulating Electrodes
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Hippocampal prosthesis
Silicon chip that attempts to imitate the brain’s ability to create long-term memories› Reconstruct neuron-to-neuron connections that
can be read by properly functioning neural circuitry
Successful in restoring memory in rats and monkeys with impaired memory
So far we have:› Controlled involuntary movement
› Managed pain
› Restored hearing
› Restored sight
› Restored memory
How about helping those who can not move or communicate at all?
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Locked-in syndrome› Complete paralysis of nearly all voluntary muscles› Some eye and facial muscle movement may be
possible› Caused by damage to specific portions of the lower
brain and brainstem, with no damage to the upper brain
› Fully aware, cognitive function still present› Brain works just fine, but it lacks the ability to
communicate to the rest of the body› Amyotrophic Lateral Sclerosis (ALS), brainstem
stroke, Multiple Sclerosis (MS)
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• Give those who have lost the ability to communicate and/or move a better way to communicate, and a way to control their surroundings
Normal neural firing present
Cognitive functions intact
Brain works just fine
Communication between brain and rest of body lost (no communication with spinal cord)
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Bypass the spinal cord with electrode arrays and processors
Place electrode arrays into motor cortex to pick up neural signals
Send neural signals to processors to decode, encode, generate control signals
BCI: Brain Computer Interface
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Neurons communicate via action potentials› Short-lasting events in which the electrical membrane potential
of a neuron rapidly rises (depolarization) and then falls (repolarization)
When a neuron generates an action potential, the signal propagates down the neuron as a current which flows in and out of the cell through excitable membrane regions
Electrodes placed near/on/in the brain can measure voltage changes over time that are caused by the propagating action potentials
Measure the difference in voltage over time between multiple electrodes, and this gives us the electrical brain activity of an individual
Electroencephalography (EEG)› Non-invasive, Poor signal-to-noise ratio
Electrocorticography (ECoG)› Invasive, Better signal-to-noise ratio
Single Unit Neurons (neural spike activity)› Invasive
Local Field Potential› Invasive
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Let’s go inside the brain!
Sense signals quicker
Lower spatial resolution
Less noise
Better signals overall
100 Channel Microelectrode array:small, biocompatible, safe, easily powered
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Delta› 0 Hz to 4 Hz, slow wave sleep
Theta› 4 Hz to 8 Hz, drowsiness or meditation
Alpha› 8 Hz to 12 Hz, closing of eyes, deep relaxation
Beta› 12 Hz to 40 Hz, motor activity, active thinking, active
concentration Gamma
› > 40Hz, hyper brain activity, conscious attention, good for learning
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Different movements (imagined or real) cause different, unique changes in the acquired neural signal
Changes can be seen in individual frequency bands
Any signal that can be represented as an amplitude that varies in time has a corresponding frequency spectrum
Transform signals into a different domain so we can extract features (signal characteristics) from individual frequency bands› Fast Fourier Transform, Wavelet Decomposition, Independent Component
Analysis, etc.› Band power, amplitude, frequency, power spectral density (describes how the
energy of a signal is distributed with frequency)
Notice patterns from extracted features
Control in 2 directions:Up/Down,Left/Right
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iframe width="854" height="480" src="https://www.youtube.com/embed/wxIgdOlT2cY" frameborder="0" allowfullscreen></iframe>
http://www.cbsnews.com/news/paralyzed-woman-uses-mind-control-technology-to-operate-robotic-arm/
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Make it smaller
Process cleaner signals for more accurate control signals
Quicker (as close to Real-Time as possible)
Completely independent (no need for clinician)
Wireless
Lower limb prosthetic