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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
•• Frontal Lobe Frontal Lobe – Primary motor cortex, Frontal Eye,– information processing,
•• ParietalParietal– Sensory information, taste, pressure, sound,
temp..•• OccipitalOccipital
– Visual processing center•• TemporalTemporal
– Auditory processing
Frontal lobe
Parietal
OccipitalTemporal
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
• 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
• 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
• Wheel Chair• Controlling Cursor• Controlling OS• Word Processing
Research Labs
• 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
