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8/8/2019 Cortical Neural Pros the Tics
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Cortical Neural Prosthetics
Presented by Artie Wu
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Cortical Neural Prosthetics
Andrew B. Schwartz Department of Neurobiology and Bioengineering, University of
Pittsburgh Annual Review of Neuroscience. 2004. 27:487-507
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O utline
Background on Neural ProstheticsMotivationElectrodes Microwires Michigan probes Cyberkinetics probesComplicationsExtraction AlgorithmsFLAMES: Floating Light Activated MicroElectrical Stimulator
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Neural Prostheses
Stimulating and recording electrodes implantedin cerebral cortex to activate neurons in differentparts of CNSCortical Neural Prostheses (CNP) to control armmovement Use neural activity to control devices to replace
natural, animate movements in paralyzed individuals
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Current Benefits of Neural Prostheses
Restore hearing, visionAlleviate symptoms of Parkinsons Disease (PD)Rid Tourette syndromeMitigate head or spinal-cord traumaRestore movement in paralyzed patients
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Ridding Tourette
Source: University Hospitals of Cleveland, affiliated with CWRU
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Problems of Muscle Activation
Muscle activation muscle force is nonlinear problemPrimary motor cortex drives motor activation Depends on force, muscle length, limb geometry,
orientation of limb relative to external forces, andinertia of moving segments
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Representing Movement
Current CNPs represent movement as end pointdisplacements Motor cortical discharge rate proportional to tuning
function (discharge rate related to direction)All cells actively code each directionWeighted response gives specific direction using PopulationVector Algorithm (PVA)Magnitude and direction of this neural vector representationis highly correlated with movement velocity
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Electrodes: Silicon MicromachinedMicroprobes
Michigan probe Planar devices Boron diffusion delineates shape of probe Multiple recording sites along shaft
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Electrodes: Silicon MicromachinedMicroprobes
Cyberkinetics Inc/University of Utah array 100 microelectrodes array on 4mm by 4mm base Array inserted into cortex
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Tissue Reactions
Blood vessels disrupted and microhemorrhageAstrocytes proliferate and form encapsulation aroundelectrode
Cellular sheath around electrode with dense cellsSwelling pushes neurons awayNeuron density is increases after several weeks
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Impedance Caused by Encapsulation
Source: Chronic neural recordings using silicon microelectrode arrayselectrochemically deposited with a poly(3,4-ethylenedioxythiophene)(PED O T) film, K. Ludwig, J. Neural Eng. 3. 2006, 59-70.
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Extraction algorithms: Inferential
Population Vector Algorithm relates movementdirection and firing rate in motor cortex
D b o = A cos = b xmx + b ymy + b zm z
D: discharge rate A: amplitude of tuning function
: angle between cells preferred directionB : vector in direction of preferred direction,magnitude is AM : unit vector in movement direction
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Extraction algorithms: Classifiers
Based on pattern recognitionEx: Self-organizing feature map (S O FM) Single layer of nodes connected to input vector with set of
connection weight (i.e., discharge rate) Initially, weight vectors set randomly Element with weight vector closest to input vector = winner Neighbors weights moved closer to input vectors Each cluster assigned direction
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FLAMES: Floating Light ActivatedMicro Electrical Stimulators
Source: Steve Menn
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FLAMES: Floating Light ActivatedMicro Electrical Stimulators
Source: Steve Menn
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Round 3 Design Specs
56 different devices1,2,3,4 diodesWith and without 50k
parallel resistor
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Thank you