[FieldTrip] What kind of baseline correction to use for time-frequency analysis

[Esther Eijlers]

Dear community,

Although I’ve seen other questions related to this topic, I still have some questions regarding baseline correction when executing a time-frequency analysis:

After time-frequency analysis, I want to use the trial output either to compare (within participants) trials from different conditions or to put the datapoints of different trials into a regression (also on participant level).
The question for me is how to deal with a baseline correction in this situation? The data before each trial of interest is in reaction to viewing a fixation cross.

  1.  If I understand it correctly, with the default config setting for cfg.polyremoval the mean of the whole trial is subtracted (prior to spectral analysis) to get rid of the offset in oscillations.
  2.  Does it mean that since I’m doing analyses on a participant level first, I only need to do this kind of baseline correction (from stimulus onset on)?
  3.  I thought that I should not subtract the mean of a window prior to stimulus onset, from the raw trial data before doing time-frequency analysis (the kind of baseline correction you would do with ERP analyses), but I see this happening in some articles. Did I not get it right, or is this related to the distinction between evoked and induced power, or something else?
  4.  Or is it an option (and should I) subtract the mean of a window prior to stimulus onset only after decomposition of the data in the power spectrum, for all trials?

Thanks a lot!

Best,
Esther


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