# Units of source estimates

**URL:** <https://mne.discourse.group/t/units-of-source-estimates/1424>\
**Category:** Mailing List Archive (read-only)\
**Tags:** list-archive\
**Created:** [February 13, 2018, 5:33pm UTC](https://mne.discourse.group/t/units-of-source-estimates/1424 "2018-02-13T17:33:17Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![system](https://global.discourse-cdn.com/free1/uploads/mne/original/1X/85cc6bd2b69cb698a166dc6d880fb550510d0144.jpeg) [@system](https://mne.discourse.group/u/system)\
**Post date:** [February 13, 2018, 5:33pm UTC](https://mne.discourse.group/t/units-of-source-estimates/1424/1 "2018-02-13T17:33:17Z")

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Hi All,

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?

For example, my understanding is that:  
(1) MNE returns estimates in current amplitude Am/m^2  
(2) dSPM and sLORETA return standardized estimates (arbitrary units?)

I would expect the sparse estimates to return current amplitudes, but I'm  
not sure. What about beamformers?

Thanks,  
Emily  
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**Author:** ![system](https://global.discourse-cdn.com/free1/uploads/mne/original/1X/85cc6bd2b69cb698a166dc6d880fb550510d0144.jpeg) [@system](https://mne.discourse.group/u/system)\
**Post date:** [February 13, 2018, 6:31pm UTC](https://mne.discourse.group/t/units-of-source-estimates/1424/2 "2018-02-13T18:31:09Z")

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Sorry, I think the MNE estimates are in Am, not Am/m^2.

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**Author:** ![system](https://global.discourse-cdn.com/free1/uploads/mne/original/1X/85cc6bd2b69cb698a166dc6d880fb550510d0144.jpeg) [@system](https://mne.discourse.group/u/system)\
**Post date:** [February 13, 2018, 8:36pm UTC](https://mne.discourse.group/t/units-of-source-estimates/1424/3 "2018-02-13T20:36:40Z")

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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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