BCI Systems

Brendan Allison, Ph.D.Institute for AutomationUniversity of Bremen6 November, 2008

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A BCI enables communication without movement.

Some patients cannot use any interface requiring movement.

What is a BCI?

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What is a BCI?

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Most BCIs translate your brain’s electrical activity (EEGs) into messages or commands.

Performing mental tasks produces electrical activity detectable with electrode caps.

What is a BCI?

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BCIs may be:

•Non-invasive (usually EEG)•Invasive

•ECoG (surface of cortex)•depth recording (in brain)

What is a BCI?

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When a neuron is active, its voltage may change by 100 mV or more.

Electrical activity in a single neuron.

How do EEGs work?

Neural communication produces electrical activity.

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This activity may be detectable to electrodes on the scalp.

How do EEGs work?

Conventional electrode caps from EGI, Neuroscan, and Electro-Cap.

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Newer EEG recording systems:

• 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

How do EEGs work?

Field recording systems from Quasar, Advanced Brain Monitoring, and Pineda et al (2003).

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QUASAR Hybrid or eIBE sensors

Audio Headset EOG/EEG GlassesQUASAR IBE Electrodes

How do EEGs work?

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Emotiv and NeuroSky systems

How do EEGs work?

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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)

How do EEGs work?

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Other functional imaging approaches:

• Functional Magnetic Resonance Imaging (fMRI)• Magnetoencephalography (MEG)• Positron Emission Tomography (PET)• Functional Near Infrared (fNIR)

How do EEGs work?

A functional MRI An MEG machine Functional Near Infrared

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BCIs cannot read minds or literally interpret mental activity.

hello

yes

pain

What isn’t a BCI?

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BCIs are a popular topic in sci fi!

The Matrices Firefox Strange Days Neuromancer

JohnnyMnemonic

Star Trek: The Cage

Dreamscape The X – Mens

What isn’t a BCI?

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More bci fi ….

Total Recall Minority Report Brainstorm The Lawnmower Men

The Govenator!!

What isn’t a BCI?

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BCIs cannot:

•Read your thoughts.

What isn’t a BCI?

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BCIs cannot:

•Operate without your knowledge or free will.

What isn’t a BCI?

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BCIs cannot:

•Write to the brain.

What isn’t a BCI?

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BCIs cannot:

•Repair injured areas.

(??)

What isn’t a BCI?

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These similar approaches are not BCIs: ??

• Biofeedback• Prosthetics• Retinal or cochlear implants• Medical EEGs• EEG or fMRI Lie Detection• Neuromarketing• Employee screening• Attention or fatigue monitors

What isn’t a BCI?

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BCIs rely on voluntary mental activities such as:

Imagined movement

What is a BCI?

Torrey Pines golf course

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BCIs rely on voluntary mental activities such as:

Emotional imagery

What is a BCI?

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BCIs rely on voluntary mental activities such as:

Selective attention(SSVEP)

What is a BCI?

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BCIs rely on voluntary mental activities such as:

Selective attention(P300)

What is a BCI?

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BCIs rely on voluntary mental activities such as:

Certain mental tasks

6X 942

Object rotation Math Singing

What is a BCI?

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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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How do BCIs work?

o General Schematico P300 BCIo Mu BCIo Other BCIs

Components

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A BCI requires the following:

- At least 2 electrodes - An amplifier designed for

EEGs- A mediocre personal

computer- An A/D card in the computer- Software

Components

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All BCIs have at least four components:

1) Signal Acquisition

2) Feature Extraction

3) Translation Algorithm

4) Operating Environment

Components

The Four BCI Components(Wolpaw et al., 2002; Allison et al., 2007)

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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

Components

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Motor imagery: ERD

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Many sources create noise.

Electrode cap Raw EEGs from a field setting

Acquisition

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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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Recording from a neuron (Kandel et al., 1988)Top: Utah intracranial electrode arrayBottom: Cone electrode

Cortical Neurons

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A severely disabled subject controls a switch (Kennedy et al., 2004)

A patient with an implanted BCI (Cyberkinetics, Inc.)

Cortical Neurons

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Cortical Neurons

ECog activity in several human patients during hand or tongue movement (Miller, in press)

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The P300 only occurs after target flashes (Allison and Pineda, 2003).

Selective attention: P300

EEGs from a P300 BCI

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0 100 200 300 400 500 600 700

time after flash begins (ms)vo

ltage

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Nontargets

Targets

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EnvironmentUser 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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EEGs from a P300 BCI

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0

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0 100 200 300 400 500 600 700

time after flash begins (ms)

volt

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Nontargets

Targets

The P300 only occurs after target flashes (Allison, 2003).It is often largest over site Cz or Pz (central or parietal areas).

Acquisition, Extraction