[Mne_analysis] mne or dspm for comparing evoked amplitude between subjects

[Hari Bharadwaj]

Hi Matt,
   In my opinion, for a fixed ROI, either would be fine if the
distributions are made similar for some baseline period across
subjects. For instance, if you express each subject's evoked response
in the ROI (dSPM or MNE) in terms of z-scores relative to the baseline
period i.e. something to the effect of
     z(t) = (x(t) - mean(x(baseline)))/std(x(baseline))
then since all subjects are similar in the baseline period (i.e mean 0,
variance 1), the peaks in the trial period can be compared across groups
of subjects.

The preference for dSPM over MNE in my mind primarily comes from the dSPM
enabling a better ROI selection (if it is based on MEG data, rather than
apriori) since localization is typically less biased.

Regards,
Hari



On Wed, December 12, 2012 6:43 pm, Matthew Panichello wrote:
> Hi Everyone,
>
> I'd like to extract the peak evoked amplitude within a particular ROI
> for each of my subjects, then test if this value differs between two
> subgroups of the subjects.
>
> I'm vaguely aware that normalization can be important when comparing
> certain statistics between subjects, although I'm not entirely certain
> when this is appropriate. I have a hunch it may be applicable now, though.
>
> As I understand it, dspm is essentially noise-normalized mne. Is it more
> appropriate to use dspm, rather than mne, when comparing peak response
> amplitude between subjects?
>
> Thanks,
>
> --
> Matthew Panichello
> Research Coordinator, Bar Group
> Massachusetts General Hospital
> Phone: 617-726-9034
>
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-- 
Hari Bharadwaj
PhD Candidate, Biomedical Engineering,
Boston University
677 Beacon St.,
Boston, MA 02215

Martinos Center for Biomedical Imaging,
Massachusetts General Hospital
149 Thirteenth Street,
Charlestown, MA 02129

hari at nmr.mgh.harvard.edu
Ph: 734-883-5954