[Simnibs-discuss] Adding Tissues in the leadfield question

[Axel Thielscher]

Hi Martin,


in general terms, the tdcs optimization tries to focus the currents on 
the target region(s) while avoiding all the rest (the "rest" is 
determined as all surfaces except the target regions). By including CSF 
and skull into the leadfield, you basically ask the optimization to 
avoid those surfaces as well, and this then will cause changes in your 
optimization results.


Best regards,

Axel


On 18-05-2022 19:51, Martin Bardhi wrote:
> Hello,
> My name is Martin B and I am a university student researched using 
> simNibs tDCS optimization feature for my project. When testing some of 
> the functionality of the optimization scripts I found that if I 
> include different tissues in the leadfield (CSF and skull surfaces for 
> example (1003,1004) ) the resulting optimization will have different 
> electrode placements (even when I then exclude these tissues from 
> target.tissues().
> I am a little confused as to what including these tissues in the 
> leadfield does, as I initially thought it just meant that electric 
> field would be recorded there but I have now found that it changes the 
> optimization in some way. So, my question is: what does including 
> different tissues in the leadfield do. And if I wanted to obtain an 
> optimization that would be best reflective of real-world results, what 
> tissues should I include (if any)?
>
> Thanks,
>
> Martin
>
>
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-- 
Dr. Axel Thielscher
Professor of Neurophysics and Neuroimaging
Danish Research Center for Magnetic Resonance
Copenhagen University Hospital Hvidovre
DK-2650 Hvidovre, Denmark
www.drcmr.dk
&
Department of Health Technology
Technical University of Denmark
DK-2800 Kgs. Lyngby
http://www.healthtech.dtu.dk/
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