BMI2 SS08 – Class 9 “EEG-MEG 1” Slide 1

Biomedical Imaging 2Biomedical Imaging 2

Class 9 – Electric and Magnetic Field Imaging: Electroencephalography (EEG),

Magnetoencephalography (MEG). Part 1: Theory

04/02/08

BMI2 SS08 – Class 9 “EEG-MEG 1” Slide 2

Biological Contrast MechanismsBiological Contrast Mechanisms

Electric stimulation with electric field

Electrotherapy

Electric stimulation with magnetic field

Magnetoelectrotherapy

Magnetization of material

Magnetotherapy

Electric field from electric sources

Magnetic field from bioelectric sources

Magnetic field from magnetic material

Electric measurement of electric impedance

Magnetic measurement of electric impedance

Magnetic measurement of magnetic susceptibility

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Microscopic Ion ConcentrationsMicroscopic Ion Concentrations

Membrane

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Simplified Membrane, Ion Channel Depiction Simplified Membrane, Ion Channel Depiction

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Microscopic Ion CurrentsMicroscopic Ion Currents

Membrane

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Propagation of Ion CurrentsPropagation of Ion Currents

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Propagation of Ion CurrentsPropagation of Ion Currents

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Typical Voltage vs. Time TransientsTypical Voltage vs. Time Transients

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Interaction of Nerve and MuscleInteraction of Nerve and Muscle

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Electromyography (EMG)Electromyography (EMG)

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Examples of EMG RecordingsExamples of EMG Recordings

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Electrocardiography (ECG, EKG)Electrocardiography (ECG, EKG)

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Electrocardiography (ECG, EKG)Electrocardiography (ECG, EKG)

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Magnetocardiography (MCG)Magnetocardiography (MCG)

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Magnetocardiography (MCG)Magnetocardiography (MCG)

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Electric Transmission of Biological InformationElectric Transmission of Biological Information

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Electric Transmission of Biological InformationElectric Transmission of Biological Information

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Invasive Recording of Electric ActivityInvasive Recording of Electric Activity

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Properties of Electrically Active TissuesProperties of Electrically Active Tissues

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“Typical” Central Nervous System (CNS) Neuron“Typical” Central Nervous System (CNS) Neuron

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Microscopic/Internal → Macroscopic/ExternalMicroscopic/Internal → Macroscopic/External

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EEG and MEG Have Different Surface EffectsEEG and MEG Have Different Surface Effects

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EEG and MEG Have Different Surface EffectsEEG and MEG Have Different Surface Effects

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EEG and MEG Have Different Surface EffectsEEG and MEG Have Different Surface Effects

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EEG and MEG Have Different Surface EffectsEEG and MEG Have Different Surface Effects

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Typical Event-Related Potential (ERP) MeasurementTypical Event-Related Potential (ERP) Measurement

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Averaging Across Repeats (Time-Series Analysis!)Averaging Across Repeats (Time-Series Analysis!)

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ERP ComponentsERP Components

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But Can We Do ERP Imaging?But Can We Do ERP Imaging?

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Theoretical Advantages of MEGTheoretical Advantages of MEG

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Spatial Resolution of MEGSpatial Resolution of MEG

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Spatial Resolution of MEGSpatial Resolution of MEG

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Comparison of Properties of Functional Brain Imaging MethodsComparison of Properties of Functional Brain Imaging Methods

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Measurement ApparatusMeasurement Apparatus

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Scale of Biomagnetic FieldsScale of Biomagnetic Fields

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MEG HelmetMEG Helmet

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MEG Raw Data and ImageMEG Raw Data and Image

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Placement of EEG ElectrodesPlacement of EEG Electrodes

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Placement of EEG ElectrodesPlacement of EEG Electrodes

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Dependence of Amplitude on PositionDependence of Amplitude on Position

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Spatial Sensitivity of an EEG Electrode PairSpatial Sensitivity of an EEG Electrode Pair

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EEG Waveforms—Frequency BandsEEG Waveforms—Frequency Bands

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Power Spectrum of Typical EEGPower Spectrum of Typical EEG

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Behavioral Correlates of EEG WaveformsBehavioral Correlates of EEG Waveforms

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Locating Source of EEG Signal (e.g., Epileptic Focus)Locating Source of EEG Signal (e.g., Epileptic Focus)

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Locating Source of EEG Signal (e.g., Epileptic Focus)Locating Source of EEG Signal (e.g., Epileptic Focus)

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Locating Source of EEG Signal (e.g., Epileptic Focus)Locating Source of EEG Signal (e.g., Epileptic Focus)