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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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0:19-0:50; 2:07-2:47

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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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Radial 8 Task

Radial 8 Task

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Control in 3 directions:Up/Down,Left/Right,Front/Back

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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

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http://www.cbsnews.com/videos/paralyzed-woman-controls-robotic-arm-with-mind