[Eeglablist] Wavelet comparisons

Stavros Zanos stavroszanos at yahoo.com
Fri Feb 11 10:55:40 PST 2005

Hi all.
In an ECoG experiment, I want to calculate frequency power changes in induced activity.  I have applied the continuous wavelet transform (CWT) and now I want to use a measure of 'change' from the baseline (that is, prior to the event).  Three issues arise:
1) How to calculate the "baseline" wavelet coefficient: I could take a 100msec window prior to the event and calculate an average baseline coefficient.  Is this 'mathematically' valid?  It works ok for frequency power data, but coefficient data are another story.
2) How to calculate the "change": I could simply take the adjusted difference in the coefficient between each timepoint and the baseline.  But is this valid?
3) How to produce an "average change" waveform: Is this possible by simply averaging coefficient waveforms for all trials?
My intuition says that wavelet data are to be treated differently that plain frequency power data.
Any help will be greatly appreciated.
Stavros Zanos, MD.
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