Brain Computer Interface. Mina Mikhail

Transcription

1 Brain Computer Interface Mina Mikhail

2 Introduction Ways for controlling computers Keyboard Mouse Voice Gestures Ways for communicating with people Talking Writing Gestures

3 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

4 Brain Computer Interface Direct Neural Interface or Brain-Machine interface An interface between the human brain and computers A New communication Channel

5 BCI Misconceptions Cannot read thoughts Cannot write to the brain Cannot repair injured areas Cannot operate without your will

6 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

7 Brain Regions Frontal Lobe Primary motor cortex, Frontal Eye, information processing, Parietal Sensory information, taste, pressure, sound, temp.. Occipital Visual processing center Temporal Auditory processing Frontal lobe Temporal Parietal Occipital

8 Human Brain Whenever a neuron is active, its voltage changes

9 Human Brain Million of neurons fire together Each mental state produces a distinct pattern of electrical activity

10 Measuring Brain Activity

11 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

12 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

13 EEG Measures the electrical activity of the neurons. Advantages High time resolution Cheaper portable Disadvantages Low spatial resolution Still not user friendly

14 EEG Montage system An international system that describes and applies the location of the electrodes

15 Rhythmic Activity Delta Band < 3 Hz Deep sleep Theta Band 4-7 Hz Drowsiness and meditation Alpha Band 8-12 Hz Awake Beta Band Hz Concentration and thinking

16 BCI Categories

17 BCI Categories

18 BCI Categories

19 Differences Electrode placements Number of electrodes Number of trial before taking a decision

20 General Approach

21 Signal Acquisition EEG CAP Bioamplifier Electrodes Active electrodes Conductive gel Impedance Checker

22 Signal Preprocessing Artifacts Technical Artifacts Line noise Electrode Artifacts

23 Signal Preprocessing Physiological Artifacts Eye Blinking artifacts Eye movement Artifacts Muscle Activity artifact

24 Signal Preprocessing

25 Methods for Artifact Rejection Filters Artifact Rejection Artifact Subtraction (using EMG sensors) Blind Source Separation Independent Component Analysis (ICA)

26 Feature Extraction (frequency Frequency Domain Features domain) FFT, wavelets, finite impulse response EEG Frequency Band Power most of the times a measure of event related desynchronization (ERD) is used

27 Feature Extraction (Time domain) Spatial Domain Feautres Hjorth parameters Three parameters are used to characterize the EEG Activity (mean power) Mobility (mean frequency) Complexity

28 Classification Bayes Classifiers Support Vector Machines Artifical Neural Networks

29 Application Wheel Chair Controlling Cursor Controlling OS Word Processing

30 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

31 BCI Systems