[FieldTrip] Oscillatory power normalization

[Matt Mollison]

Hi FieldTrippers,

In almost all the papers I've read involving oscillatory power, some kind
of transformation is done to the data due to the 1/f power spectrum effect
(power decreases as frequency increases). I'm mostly looking at
within-subjects experiments (every subject behaved in all conditions)
comparing conditions across subjects, but it seems like normalizing the
power spectrum should apply in any case (especially if any kind of
parametric stats are done—right?).

Anyway, it's not apparent to me how to use FT functions like
ft_freqanalysis to make these transformations (e.g., log10 normalization,
dB normalization [EEGLab does this], vector length normalization, etc.; the
only thing I see is in ft_sourcedescriptives, but I'm not doing source
analyses), and it confuses me why this is the case. I can't find much
discussion regarding the 1/f issue on the FT wiki or the mailing list. This
seems like an important step that is missing from any frequency analysis
workflow. Am I missing something (meaning I just don't see the option), am
I misunderstanding something (meaning I'm incorrect in this assumption), or
is this an issue that needs to be fixed?

Thanks,
Matt

--
Univ. of Colorado at Boulder
Dept. of Psychology and Neuroscience
matthew.mollison at colorado.edu
http://psych.colorado.edu/~mollison/
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