Brain Computer Interface
Mina Mikhail
minamohebn@gmail.com
Introduction
• Ways for controlling computers
– Keyboard
– Mouse
– Voice
– Gestures
• Ways for communicating with people
– Talking
– Writing
– Gestures
Problem
• Shortage of the current ways of interaction
– Require muscle movements
• Disabled people
– Totally paralyzed people are estimated to be
2 cases per 100,000 each year
– Amyotrohic lateral sclerosis (ALS)
• This raises the need of a new way of
communication
Brain Computer Interface
• Direct Neural Interface or Brain-Machine
interface
• An interface between the human brain and
computers
• A New communication Channel
BCI Misconceptions
• Cannot read thoughts
• Cannot write to the brain
• Cannot repair injured areas
• Cannot operate without your will
Human Brain
• The Ultimate Parallel Machine !
• Billions of neurons require a lot of energy.
– 15% of the cardiac output
– 20% of total body oxygen consumption
– 25% of total body glucose utilization.
• Energy consumption for the brain to simply
survive is 0.1 calories per minute … and …
• 1.5 calories per minute during crossword
puzzle
Brain Regions
Parietal
Frontal lobe
Occipital
• Frontal Lobe
Temporal
– Primary motor cortex, Frontal Eye,
– information processing,
• Parietal
– Sensory information, taste, pressure, sound,
temp..
• Occipital
– Visual processing center
• Temporal
– Auditory processing
Human Brain
• Whenever a neuron is active, its voltage
changes
Human Brain
• Million of neurons fire together
• Each mental state produces a distinct
pattern of electrical activity
Measuring Brain Activity
Measuring Brain Activity
• Positron emission tomography
– A radio Active isotope is injected into the
subject’s blood
– Isotopes emits positrons
• Advantages
– High spatial resolution
• Disadvantages
– Expensive
– Low time resolution
– Not portable
Functional Magnetic Resonance
• FMRI depends on blood flow
• It measures the magnetic properties of the
hoemoglobin
• Active neurons consume oxygen carried by
hemoglobin
• Advantages
– High spatial resolution
• Disadvantages
– Expensive
– Low time resolution
– Not portable
EEG
• Measures the electrical activity of the
neurons.
• Advantages
– High time resolution
– Cheaper
– portable
• Disadvantages
– Low spatial resolution
– Still not user friendly
EEG Montage
• 10-20 system
– An international system that describes and
applies the location of the electrodes
Rhythmic Activity
• Delta Band
– < 3 Hz
– Deep sleep
• Theta Band
– 4-7 Hz
– Drowsiness and meditation
• Alpha Band
– 8-12 Hz
– Awake
• Beta Band
– 13-30 Hz
– Concentration and thinking
BCI Categories
BCI Categories
BCI Categories
Differences
• Electrode placements
• Number of electrodes
• Number of trial before taking a decision
General Approach
Signal Acquisition
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EEG CAP
Bioamplifier
Electrodes
Active electrodes
Conductive gel
Impedance Checker
Signal Preprocessing
• Artifacts
– Technical Artifacts
• Line noise
• Electrode Artifacts
Signal Preprocessing
• Physiological Artifacts
– Eye Blinking artifacts
– Eye movement Artifacts
– Muscle Activity artifact
Signal Preprocessing
Methods for Artifact Rejection
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Filters
Artifact Rejection
Artifact Subtraction (using EMG sensors)
Blind Source Separation
– Independent Component Analysis (ICA)
Feature Extraction (frequency
domain)
• Frequency Domain Features
– FFT, wavelets, finite impulse response
– EEG Frequency Band Power
• most of the times a measure of event related
desynchronization (ERD) is used
Feature Extraction (Time
domain)
• Spatial Domain Feautres
– Hjorth parameters
• Three parameters are used to characterize the
EEG
– Activity (mean power)
– Mobility (mean frequency)
– Complexity
Classification
• Bayes Classifiers
• Support Vector Machines
• Artifical Neural Networks
Application
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Wheel Chair
Controlling Cursor
Controlling OS
Word Processing
Research Labs
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Graz Brain Computer Interface
BCI Research at Alberta University
BCI Research at Oxford University
Berlin Brain Computer Interface
Computer Vision and Multimedia
Laboratory Geneva University
BCI Systems