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11
Decoding Neural Activity from an Intracortical Decoding Neural Activity from an Intracortical Implant in Humans with TetraplegiaImplant in Humans with Tetraplegia
Chad E. BoutonChad E. Bouton
BattelleBattelleHealth and Life Sciences DivisionHealth and Life Sciences Division
22
BackgroundBackground
• Cyberkinetics (founded in 2001) developed a Brain-Computer Interface (BCI) system called BrainGate
• At the core of the system was the Utah Electrode Array (brain implant)
• Implanted in the Primary Motor Cortex (M1), hand/arm area
• Purpose was to allow severely disabled individuals to communicate, use their PC’s, and even control a wheelchair by decoding their thoughts
33
Elbow Extension
BackgroundBackground
• Battelle developed user training methods and Neural Decoding Algorithms
• Processed signals from the electrode array (96 channels)
• Goal: isolate and predict arm/hand movements the patient is thinking about
Time Domain Signals from Electrode Array
Neural Decoding
Shoulder Abduction
Wrist Flexion
44
PatientsPatients
• 54 year old female stroke victim (“SCI 3”), quadriplegic and unable to speak
• 36 year old male, diagnosed with ALS, quadriplegic and unable to speak
• Conducted an intended motion survey to look at neural modulation (change in neuronal firing patterns) for various visually cued movements
– Shoulder Flexion and Extension
– Shoulder Abduction and Adduction
– Elbow Flexion and Extension
– Wrist Flexion and Hyperextension
– Wrist Radial and Ulnar Deviation
– Wrist Pronation and Supination
– Hand Open and Close
55
Initial Motion Survey with SCI3Initial Motion Survey with SCI3
OMAS, SCI3, Tasks 1A and 2A
0
2
4
6
8
10
12
14
16
18
ShoulderFlexion
ShoulderExtension
Shoulder Add. Shoulder Abd. WristExtension
Wrist Flexion Wrist RadialDev. with Palm
Down
Wrist UlnarDev. with Palm
Down
Num
. of U
nits
Iden
tifie
d
Series1
Zero Units (Neurons) Exhibited Differing Firing Patterns
-2000
200 -100-50050100150200
-150
-100
-50
0
50
100
150
Flexion/extension mixed (dark/med blue)
(Axes are unit-less and represent the first three principal components from a principal components / eigenvector analysis.)
66
Thought-Driven CursorThought-Driven Cursor
• Previous decoding methods (from non-human primate work)– Position based (assumed neural patterns correlated to position in space)– Early demonstration in a human subject:
BG SCI P003 - Center Out - 2006.01.23.wmv
• Marginally stable results - proprioceptive feedback is disrupted in a disabled user
• Introduced user training methods - used motion demonstration (mirror neuron activation) and ‘coaching’ periods
• Moved away from position-based decoding and utilized model-based approaches along with support vector machine methods
• Results for Battelle decoding algorithm - stabilized cursor motion by isolating 6 intended motions: rest, four wrist motions, and close hand:
– SCI P003 8-23-06 Great - excellent motion and diagonal.mov
77
Increasing Degrees-of-Freedom -12 Motions Increasing Degrees-of-Freedom -12 Motions (6 DOF) Recognized by Algorithm(6 DOF) Recognized by Algorithm
1 2 3 4 5 6 7 8 9 10 11 12 130
20
40
60
80
100
120
Imagined Movement
Detection Rate for State vs. All Others: 2006_8_23_16_52.mat
Det
ectio
n R
ate
(%)
97.3
90.8 97
.6
85.4 89.9
79.8
98.4
92.9
92.0
94.0
94.5
80.5
restShoulder Up
Shoulder Down
Shoulder Left
Shoulder RightElbow - Curl
Eblow - Straighten
Wrist UpWrist Down
Wrist Left
Wrist Right
Hand - CloseHand - Open
1 2 3 4 5 6 7 8 9 10 11 12 130
1
2
3
4
5
Imagined Movement
False Positive Rate for State vs. All Others:
Fal
se P
ositi
ve R
ate
(%)
1.0
1.6
0.9
1.6
1.0 1.2
0.8
1.3
1.3
1.1
0.7 0.8
restShoulder Up
Shoulder Down
Shoulder Left
Shoulder RightElbow - Curl
Eblow - Straighten
Wrist UpWrist Down
Wrist Left
Wrist Right
Hand - CloseHand - Open
88
Adaptive AlgorithmAdaptive Algorithm
• Subject ALS1 exhibited decreased and
inconsistent performance
• Incorporated performance feedback during
training (“dots/masses on springs”)
• Adapted decoding algorithm after each training
block
• Demonstration: ALS1_4DOF_matlab_screen.wmv
99
Communicating to OthersCommunicating to Others
• Locked-in syndrome
• 5 imagined movements to move and ‘click’
cursor over virtual keyboard: Aug_Communications_Wonderful_high_quality.wmv
1010
Wheelchair ControlWheelchair Control
• Mobility extremely important and can be
difficult/impossible for certain patients with existing
interfaces
• As aired on 60 Minutes (Nov. 2, 2008), Cathy
Hutchinson became the world’s first person to control
a wheelchair with a brain implant (using the Battelle
training and decoding methods)– Stroke Patient - Controlling Wheelchair.wmv
1111
AcknowledgementsAcknowledgements
• Cyberkinetics, Inc.
• Dr. John Donoghue
• Dr. Leigh Hochberg
• Mike Fritz
• Almut Branner
• Abe Caplan
• Ammar Shaikhouni
• Oystein Johnsen (Eagle)