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BCI Systems
Brendan Allison, Ph.D.
Institute for Automation
University of Bremen
6 November, 2008
What is a BCI?
A BCI enables communication
without movement.
Some patients cannot use any
interface requiring movement.
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What is a BCI?
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What is a BCI?
Most BCIs translate your brain’s
electrical activity (EEGs) into
messages or commands.
Performing mental tasks produces electrical activity detectable with electrode caps.
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What is a BCI?
BCIs may be:
• Non-invasive (usually EEG)
• Invasive
• ECoG (surface of cortex)
• depth recording (in brain)
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How do EEGs work?
Neural communication produces
electrical activity.
Electrical activity in a single neuron.
When a neuron is active, its voltage
may change by 100 mV or more.
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How do EEGs work?
This activity may be detectable to
electrodes on the scalp.
Conventional electrode caps from EGI, Neuroscan, and Electro-Cap.
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How do EEGs work?
Newer EEG recording systems:
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Require less or no prep time and skill
Require less or no gel
Require fewer electrodes
Are more portable
Handle artifacts better
Are wireless
Are cheaper
Field recording systems from Quasar, Advanced Brain Monitoring, and Pineda et al (2003).
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How do EEGs work?
QUASAR Hybrid or eIBE sensors
Audio Headset
QUASAR IBE
Electrodes
EOG/EEG Glasses
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How do EEGs work?
Emotiv and NeuroSky systems
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How do EEGs work?
Invasive BCIs record activity
from electrodes under the
scalp.
Pyramidal neurons (Kandel et al., 1988)
Electrocorticogram (ECoG) recording
montage in a human patient. (Leuthardt
et al., 2004)
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How do EEGs work?
Other functional imaging approaches:
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Functional Magnetic Resonance Imaging (fMRI)
Magnetoencephalography (MEG)
Positron Emission Tomography (PET)
Functional Near Infrared (fNIR)
A functional MRI
An MEG machine
Functional Near Infrared
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What isn’t a BCI?
BCIs cannot read minds or literally
interpret mental activity.
yes
hello
pain
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What isn’t a BCI?
BCIs are a popular topic in sci fi!
The Matrices
Johnny
Mnemonic
Firefox
Star Trek:
The Cage
Strange Days
Dreamscape
Neuromancer
The X – Mens
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What isn’t a BCI?
More bci fi ….
Total Recall
Brainstorm
Minority Report The Lawnmower Men
The Govenator!!
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What isn’t a BCI?
BCIs cannot:
• Read your thoughts.
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What isn’t a BCI?
BCIs cannot:
• Operate without your
knowledge or free will.
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What isn’t a BCI?
BCIs cannot:
• Write to the brain.
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What isn’t a BCI?
BCIs cannot:
• Repair injured areas.
(??)
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What isn’t a BCI?
These similar approaches are not BCIs: ??
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Biofeedback
Prosthetics
Retinal or cochlear implants
Medical EEGs
EEG or fMRI Lie Detection
Neuromarketing
Employee screening
Attention or fatigue monitors
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What is a BCI?
BCIs rely on voluntary mental activities such as:
Imagined movement
Torrey Pines golf course
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What is a BCI?
BCIs rely on voluntary mental activities such as:
Emotional imagery
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What is a BCI?
BCIs rely on voluntary mental activities such as:
Selective attention
(SSVEP)
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What is a BCI?
BCIs rely on voluntary mental activities such as:
Selective attention
(P300)
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What is a BCI?
BCIs rely on voluntary mental activities such as:
Certain mental tasks
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X9
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Object rotation
Math
Singing
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What is a BCI?
Emerging new tasks for BCIs:
• Perceived error
• Imagined music
• New modalities and variants
(Passive BCIs):
• Anticipation
• Alertness/fatigue
• Familiarity/recognition
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Components
How do BCIs work?
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General Schematic
P300 BCI
Mu BCI
Other BCIs
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Components
A BCI requires the following:
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At least 2 electrodes
An amplifier designed for EEGs
A mediocre personal computer
An A/D card in the computer
Software
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Components
All BCIs have at least four components:
1) Signal Acquisition
2) Feature Extraction
3) Translation Algorithm
4) Operating Environment
The Four BCI Components
(Wolpaw et al., 2002; Allison et al., 2007)
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Components
Acquisition: The user performs a task that produces a distinct
EEG signature for that BCI
Extraction: Salient features are extracted from the EEG
Translation: A pattern classification system uses these EEG
features to determine which task the user performed
Environment: The BCI presents feedback to the user, and forms
a message or command
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Motor imagery: ERD
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Acquisition
Many sources create noise.
Electrode cap
Raw EEGs from a field setting
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Acquisition
A headband used for a 1D mu
BCI (Pineda et al., 2003)
Several brain areas responsible for movement.
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Extraction, Translation
Mu activity used for one dimensional control (Wolpaw et al., 1991)
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Cortical Neurons
Recording from a neuron (Kandel et al., 1988)
Top: Utah intracranial electrode array
Bottom: Cone electrode
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Cortical Neurons
A patient with an implanted BCI
(Cyberkinetics, Inc.)
A severely disabled subject controls a switch
(Kennedy et al., 2004)
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Cortical Neurons
ECog activity in several human patients during hand or tongue movement (Miller, in press)
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Selective attention: P300
EEGs from a P300 BCI
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voltage (uV)
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Nontargets
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Targets
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700
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time after flash begins (ms)
The P300 only occurs after target
flashes (Allison and Pineda, 2003).
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Environment
User task:
Imagine movement to move the cursor down.
Relax to move it up.
A mu BCI using BCI2000 (Schalk et al., 2004)
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Acquisition, Extraction
EEGs from a P300 BCI
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voltage (uV)
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Nontargets
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Targets
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100
200
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500
600
700
-2
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time after flash begins (ms)
The P300 only occurs after target flashes (Allison, 2003).
It is often largest over site Cz or Pz (central or parietal areas).
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