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Outline. ERPs/ERFs in SPM: a revisionA short introduction to the "conventional" quantification of ERPsContrasts and inference in M/EEG vs. fMRIHow to do it in SPM things to bear in mind. . . . . How does SPM/EEG work?. . Raw M/EEG data. Single trialsEpochingArtefactsFilteringAveraging, etc
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1. Contrasts & Inference - EEG & MEG Outi Tuomainen & Rimona Weil
17.5.2005
mfd
2. Outline ERPs/ERFs in SPM: a revision
A short introduction to the "conventional" quantification of ERPs
Contrasts and inference in M/EEG vs. fMRI
How to do it in SPM + things to bear in mind
6. "ERPs are signal-averaged epochs of EEG that are time-locked to the onset of stimulus"
So a waveform can be seen as a time series that plots scalp voltage (µV, T) over time (ms)
ERPs are usually recorder at multiple scalp electrode sites spatial parameter to complement the temporal and frequency information
Quantifying ERPs: can be organised into three categories: temporal, spatial and spatiotemporal Revision: ERPs/ERFs
7. Quantification of ERPs A) Temporal:
- how waveforms recorded at individual sites vary over time across experimental conditions
- amplitude and latency as a function of condition
B) Spatial:
- topographic mapping: quantifying variation in voltage across the scalp electrode array at single time point or time window
8. Quantification of ERPs
9. Quantification of ERPs Mean amplitude by Condition (2, within-subject factor) & Group (2) at Fz (electrode, within-subject factor)
Electrode factor?
-> e.g. if Left Hemisphere electrodes are likely to be systematically different from Right Hemisphere electrodes
- In high-density montages it is a good idea to divide electrodes into averaged regions (anterior-posterior, left-right, ventral-dorsal)
10. Outline ERPs/ERFs in SPM: a revision
A short introduction to the "conventional" quantification of ERPs
Contrasts and inference in M/EEG vs. fMRI
How to do it in SPM + things to bear in mind