[FieldTrip] Source statistics after applying a priori mask on gridpoints (or atlas?)

[Tzvetan Popov]

Dear Cecilia,

> Hello fieldtrippers,
> Have a question regarding ft_sourcestatistics.
> I have a priori defined mask around central gridpoints which i would like to apply before running source statistics over two groups/conditions.
> Is there a way/configuration option to do so in fieldtrip?
I am not aware of it. 
> Does it make sense or that is actually not commonly done?
Whether or not it makes sense is up to you to narrate. Indeed it is not commonly done.
> (if so why?)
The goal of the statistic machinery as implemented in FieldTrip (both sensor and source level) is to provide you with a principled decision whether or not the data from 2 or more conditions is exchangeable. If you happen to find a cluster of sensors/voxels regardless of where in the brain, you reject this H0. Thats it. The machinery does not tell you much about where in the brain, time and freq etc. 

In your case, I would simply extract the values from your mask of interest and apply Bonferroni correction. Wouldn’t that suffice?

> 
> another option could be to use an atlas (although it'd be more precise to be able to apply a mask based on gridpoints in my case)
As explained here https://www.fieldtriptoolbox.org/tutorial/salzburg/#compute-the-leadfield <https://www.fieldtriptoolbox.org/tutorial/salzburg/#compute-the-leadfield> you can use your binary mask to constrain your source model. Then you use grand averaging and source statistic as you deem appropriate. 

Good luck,
Tzvetan
 
> 
> 
> Thanks in advance for sharing your wisdom!
> 
> Cecilia
> 
> Cecilia Mazzetti, Postdoc Researcher
> Faculté de médecine de l'Université de Genève
> Chemin des Mines 9, 1202 Genève
> +41 2237 90992
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> https://doi.org/10.1371/journal.pcbi.1002202 <https://doi.org/10.1371/journal.pcbi.1002202>
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