[Mne_analysis] weighted MNE units

Alexandre Gramfort alexandre.gramfort at inria.fr
Tue Oct 8 04:50:38 EDT 2019
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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



On Tue, Oct 8, 2019 at 10:15 AM Thiede, Anja <anja.thiede at helsinki.fi>
wrote:

>         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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