[Mne_analysis] patch area information

[Olaf Hauk]

Hello,

I would like to ask for some clarification regarding the use of patch 
area information in the computation of forward solutions and inverse 
operators.

In section 7.11.2 (MNE 2.6.), the leadfield is defined without area 
information, and I assume "forward solution" and "gain matrix" are used 
synonymously. In the context of mne_do_forward_solution, a 
"current-density transformation" is mentioned, which requires patch 
information. I therefore assume that MNE uses the patch information for 
the inverse operator (not for the forward solution), in order to compute 
current densities.
Therefore, if I use the forward solution (fwd.sol.data) to compute my 
own inverse operator, I have to divide the estimate at each vertex 
location by its patch area. Is this correct?
In order to obtain the patch area for a particular vertex, I first 
select the vertices used in the forward model in fwd.src.vertno, then 
find the patches that are closest to those in fwd.src.nearest, and 
compute the area of a patch by summing across the corresponding vertex 
areas from the w-file *p-patches*.w (w.data)?
I hope I'm at least heading in the right direction...

Regards,

Olaf


-- 
Dr. Olaf Hauk
MRC Cognition and Brain Sciences Unit
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