1. MEG/EEG Module Trainees Kai Hwang Tina Rasmussen TA Gus Sudre Bronwyn Woods Instructor Bill Eddy, Ph.D. Anna Haridis Thanks to:

2. Goals Learn the basics of EEG/MEG –Why? Excellent temporal resolution, direct and noninvasive measurement of neuronal activity –How? Used simple motor, somatosensory, visual paradigms to learn data collection, pre- processing and analysis Easy to run, predictable results

3. Tasks: motor, visual, somatosensory TaskParametersWe’ll present… Paced finger tapping: Index finger, middle finger, big toe. A visual cue to indicate tap right or left finger. ISI = 800ms Source localization result of right index, right middle finger tapping. Visual checkerboard: Checkerboard stimuli shifted randomly between 4 quadrants of visual fields. Slow: ISI = 1sec, Duration = 300ms. Fast: ISI = 100ms, Duration = 300ms. Source localization of 4 quadrants of visual field. The effect of averaging and artifact rejection on sensor waveform. Time frequency analysis in sensor space Electrical stimulation: Index finger, middle finger, big toe. ISI = 492 ms, Duration = 10 ms Nothing due to time constraint.

4. Simultaneous MEG/EEG measurement

5. Experiences: EEG head cap was very stiff. It did not fit well to the head for some subjects. MEG head position indicator (HPI) coils could not be well localized by the MEG scanner, when they were glued to the EEG head cap Solution to both problems: Glue the EEG electrodes and the HPI coils directly onto the subject’s scalp Simultaneous MEG/EEG measurement

6. Processing Steps Preprocessing –Spatial filtering (SSS) –Temporal filtering (0 – 40Hz) Off-line averaging –By trial type (different finger, visual quadrant) –Reject trials with artifacts (EOG, ECG, etc) Source localization –MNE, dSPM Time-frequency analysis –Fieldtrip (Matlab)

7. Can MEG distinguish motor regions of different fingers? Right IndexRight Middle Average of 191 trials Average of 119 trials

8. Can MEG localize 4 quadrants of visual space? Upper right Bottom left Upper left Bottom right Average of 240 trials 120ms after stim. onset

9. How many events are needed to obtain a stable average waveform? Top right quadrant

10. Artifact rejection for EEG signals

11. Temporal variation of EEG activity over the visual cortex 5 consecutive stimuli: First stimulus always at bottom left Position of next 4 varies randomly ISI = 100ms, Duration= 300ms. Electrode O2 (EEG059) is placed over the right occipital lobe.

12. What have we learned? Experiments: Data recording setup Simultaneous MEG/EEG experiments Signal processing/analysis: Signal cleaning (SSS, continuous HPI, filtering) Event-related potentials Source estimation/localization Time-frequency analysis Analysis tools: MNE (GUI, batch scripts) Shell scripting (bash and C shell) Matlab toolbox (FieldTrip)

14. Toe tapping

15. Somatosensory Stimulation Right Toe

16. Somatosensory Stimulation Right Middle

17. SSS or no SSS? Right index tapping. White = no SSS, yellow= SSS on average, blue SSS before averaging MEG1821

18. cHPI (motion correction) Noisy!

19. Time-frequency analysis: EEG signals Fast:

20. Temporal variation of EEG activity over the visual cortex 3 consecutive stimuli First stimulus always at top right Next 2 shifted randomly ISI = 100ms, Duration= 300ms.