[Mne_analysis] Units of source estimates

[Alexandre Gramfort]

hi,

Hoping this is an easy question for someone to answer, otherwise I can
> answer it myself with the literature / source code: Which of the source
> estimation techniques implemented in MNE-python return estimates of the
> current amplitude?
>

well it differs a lot between solvers and even options.


>
> For example, my understanding is that:
> (1) MNE returns estimates in current amplitude Am/m^2
>

it's in Am


> (2) dSPM and sLORETA return standardized estimates (arbitrary units?)
>

it is MNE scaled by some standard deviation so it has no units. It's
comparable
to a T or and F statistic.

I would expect the sparse estimates to return current amplitudes, but I'm
> not sure.
>

sparse solvers (TF-)MxNE family, gamma-MAP, MUSIC, single dipole fit returns
dipole amplitudes in Am.


> What about beamformers?
>

it depends on the options. If you use something like the Neural Activation
Index (NAI)
to "normalize" LCMV solutions you also have quantities without units. I am
less an
expert on beamformer options but they won't return you Am.

HTH
Alex


>
> Thanks,
> Emily
>
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