[Mne_analysis] pick orientation, MNE, dSPM and group analyses

[Denis-Alexander Engemann]

Dear list,

I'm currently comparing group grand averages in a set of functional labels
which are derived from the PALS B12 Brodmann parcellation. These were then
used with subjects' stcs after morphing to fsaverage.
Now I'm really struck that with surface orientation AND mean flipping the
minima and maxima, even for dSPM shrink to values below 1 while the
expected temporal dynamics are preserved. In the 'wild', that is, *before*
averaging, the signed dSPMS are between -7 and 8, just as the
free-orientation dSPM maxima are around 8 --- *after*  --- averaging.

I'm wondering whether this could be a result of the morphing, the
anatomical variability, or even the segmentation quality.

Any hint would be appreciated.

Denis
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