External Email - Use Caution
hi,
Thank you Alex for your fast reply! If I understood correctly, then these
small values are indeed correct and should be comparable to others obtained
with the same method (e.g. for group comparisons), even if they are not the
absolute amplitudes. Is that correct?
yes
What about the unit, is it indeed Am or should it rather be called an
arbitrary unit?
it is indeed Am when you use MNE.
Alex
Best regards,
Anja
*From:* mne_analysis-bounces at nmr.mgh.harvard.edu [mailto:
mne_analysis-bounces at nmr.mgh.harvard.edu] *On Behalf Of *Alexandre
Gramfort
*Sent:* tiistaina 8. lokakuuta 2019 11.51
*To:* Discussion and support forum for the users of MNE Software <
mne_analysis at nmr.mgh.harvard.edu>
*Subject:* Re: [Mne_analysis] weighted MNE units
* External Email - Use Caution *
Dear Anja,
MNE promotes sources with minimal energy / variance. This leads
to a bias in the estimated amplitudes. If you care about absolute
amplitudes you should have a look at dipole fits or sparse solvers
that estimate multi-dipole configurations.
HTH
Alex
* External Email - Use Caution *
Hi,
I am using MNE Python to do source modeling with weighted MNE and am
wondering about very small units of the sources. This is something that I
have found with my own data and could reproduce the issue using the sample
data:
https://github.com/athiede13/speech_sources/blob/master/weighted_MNE_sample.py
While I would expect source activations in the range of 30-60 nAm (for
example as in dipole solution
https://mne.tools/stable/auto_examples/inverse/plot_mixed_norm_inverse.html
that uses the same data), what I get are values in the range of 0.3-0.6
nAm. So there seems to be a difference of 2 orders of magnitude. Do you
know where this could come from? I have pondered about this for a while and
cannot find the source of the difference.
Thanks for having a look and I hope that we can figure it out!
Best regards,
Anja Thiede
_________________________________________________________________________
Anja Thiede, M.Sc.
Doctoral student
Cognitive Brain Research Unit
Department of Psychology and Logopedics
Faculty of Medicine
University of Helsinki
E-Mail: anja.thiede at helsinki.fi
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