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

[dgw]

Hi Denis,

This effect can be influenced by a lot of variables. I would say
anatomical variability is a huge one but there are tons of factors
which affect just that:

Did you decimate? (I guess you must have to morph, but how severely
did you decimate?)
Are you using --loose, or --loosevar
What parameters with those
Did you use cps?

I suspect the morphing will also influence this, but that is easy to
check (and wise to do see how the labels morph back on the
individual's surface?). Though as long as you have FreeSurfer quality
scans, I don't expect the segmentation to be an issue. What if any
smoothing did you do (at each stage)?

HTH,
D


On Thu, Aug 7, 2014 at 11:25 AM, Denis-Alexander Engemann
<denis.engemann at gmail.com> wrote:
> 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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