cortical neural pros the tics

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

cortical neural pros the tics

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