1. Essentials of Electroencephalography Groundwork Jarrod Blinch May 17 th, 2011 Comprehensive presentation

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

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

5. Physics-EEG interface

7. 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

8. Rhythms NameSymbolFrequency band Examples Deltaδ0-4Slow-wave sleep Thetaθ4-8Working memory Alphaα8-12Thalamic pacemaker, memory processes, attention, visual awareness Betaβ12-30Suppressed during motor action, imagined movements, nerve stimulation Gammaγ30-~70Binding phenomena, perceiving meaningful objects, attention Omegaω~60-120Retinal origin Rhoρ~250Hippocampal ripples Sigmaσ~600Thalamocortical bursts

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

11. 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

12. 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

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

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

16. Clean data

17. Active and reference electrodes

18. 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…

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

20. Digitisation Amplifier – Gain – Resolution Nyquist theorem

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

24. Artifact rejection

27. Processing… Event-related potentials (Tues, May 31 st, 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