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Essentials of Electroencephalography Groundwork

Essentials of Electroencephalography Groundwork. Jarrod Blinch May 17 th , 2011 Comprehensive presentation. Overview. Overall goal Physics-EEG interface Potentials Rhythms Fallacies Recording Artifacts Processing…. Overall goal. Connect psychology with physiology

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Essentials of Electroencephalography Groundwork

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  1. Essentials ofElectroencephalographyGroundwork Jarrod Blinch May 17th, 2011 Comprehensive presentation

  2. Overview • Overall goal • Physics-EEG interface • Potentials • Rhythms • Fallacies • Recording • Artifacts • Processing…

  3. Overall goal • Connect psychology with physiology • EEG has been linked to psychology

  4. Physics-EEG interface

  5. Potentials • Spontaneous • Uncorrelated with the occurrence of an experimental condition • Induced • Correlated with experimental conditions but not strictly phase-locked to its onset • Evoked • Strictly phase-locked to the onset of an experimental condition across trials • Emitted • In response to omitted stimuli

  6. Rhythms

  7. Fallacies • EEG is an epiphenomenon • EEG practice divorced from theory • Artifact-free data • EEG versus MEG • Data reduction

  8. EEG versus MEG • EEG and MEG measure the same dipoles • MEG is more accurate than EEG • Results with one can be checked with the other • MEG is better because it is reference free

  9. Data reduction • EEG is contained in the raw data and nothing is added by computer transformation • Adding more electrodes beyond the standard 10/20 system provides no useful information • New data analysis methods in search of application

  10. Overview • Overall goal • Physics-EEG interface • Potentials • Rhythms • Fallacies • Recording • Artifacts • Processing…

  11. Recording • Clean data • Active and reference electrodes • Noise • Electrodes and impedance • Digitisation • Filtering

  12. Clean data

  13. Active and reference electrodes

  14. Noise • AC line current (60 Hz) • Shielded or use DC • Monitor (60-120 Hz) • Faraday cage • Movement • Relax, drop the jaw • EMG (10-1000 Hz) • EKG (1.0-1.4 Hz) • Pulse-wave • Electrodes • Alpha waves (6-12 Hz) • Skin potentials…

  15. Electrodes and impedance • Why skin impedances below 5 kΩ? • Common-mode rejection • Skin potentials

  16. Digitisation • Amplifier • Gain • Resolution • Nyquist theorem

  17. Filtering • Filters can substantially distort data • Essential to reduce noise • Aliasing, low-pass • Skin potentials, high-pass (.01 Hz)

  18. Artifact rejection

  19. Processing… • Event-related potentials (Tues, May 31st, 2 pm) • Principal component analysis • Independent component analysis (June) • Cortical dynamics (June) Osman & Moore (1993). The locus of dual-task interference: Psychological refractory effects on movement-related brain potentials. Journal of Experimental Psychology: Human Perception and Performance, 19(6), 12-92-1312. - Experiment 1, just 10 pages Luck (1998). Sources of dual-task interference: Evidence from human electrophysiology. Psychological Science, 9(3), 223-227. - Experiment 1, only 3 pages

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