Restoring Communication and 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 1
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 2
External: Microphone, Sound Processor, Transmitter Internal: Receiver, Processor, Stimulating Electrodes 3
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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? 6
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) 7
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) 8
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 9
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 10
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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 13
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0:19-0:50; 2:07-2:47 15
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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 17
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 18
Radial 8 Task Radial 8 Task 19
Control in 3directions: Up/Down, Left/Right, Front/Back 20
iframe width="854" height="480" src="https://www.youtube.com/embed/w xigdolt2cy" frameborder="0" allowfullscreen></iframe> http://www.cbsnews.com/news/paralyzed -woman-uses-mind-control-technology-tooperate-robotic-arm/ 21
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 22
http://www.cbsnews.com/videos/paralyze d-woman-controls-robotic-arm-with-mind 23