Hello,
I don't understand why my signals are so low when I perform the Morlet wavelet transformation on Brainstorm. The calculation is done in Volts, so should I adjust the scale?
Could you help me? Thanks in advance and have a nice day,
Arthur.
I checked on my end and could find a similar amplitude for a random EEG file. It makes sense since you're computing the power, having an approximate unit of V^2/Hz. With your signals being in the microvolt range, the square of the range will give something in the ballpark of 10^-12. You could rescale indeed, but the results are not per definition wrong.
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Hello,
Yes, that's what I thought too, but I wanted confirmation. Which you've done!
Thank you very much.
Have a nice day,
Arthur.
@ArthurP, @SBeumer, just to clarify. When using (complex) Morlet wavelet to compute the power time-frequency representation, what it is obtained is the instantaneous power, which has the units of the recordings squared. I.e., units µV (10^-6 V) become 10^-12 V.
It is the power spectrum density (PSD) that has as unit the units of the recordings squared over Hz (V^2/Hz)
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Indeed, I forgot the difference in units between time-frequency and Power spectrum density, you are correct!