Brain Computer Interface Mina Mikhail minamohebn@gmail.com - - PowerPoint PPT Presentation

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

• Frontal Lobe

Frontal Lobe

– Primary motor cortex, Frontal Eye, – information processing,

• Parietal

Parietal

– Sensory information, taste, pressure, sound, temp..

• Occipital

Occipital

– Visual processing center

• Temporal

Temporal

– Auditory processing

Frontal lobe Parietal Occipital Temporal

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