[Simnibs-discuss] Nexstim TMS simulation

[Alessandra Dallavecchia]

Dear all,

I have been working on trying to do some e-field simulations for our
TMS-EEG data, but have been running into a couple of issues.

We use a Nexstim system (NBT 2.2), so my first question would be if there
was a reasonable approximation for a coil configuration file that I could
use, or how I might be able to create one specific to the Nexstim figure-8
coil.

My second question is in regards to the coil position coordinates. Nexstim
outputs three coordinates for coil location, direction, and normal in mm.
However, I've noticed that these coordinates are wildly different from
those that SimNIBS gives me when I manually place a point on the GUI as
close to the center of the coil. Both are in mm and are in subject space. I
know that their coordinates line up with FreeSurfer as I do source modeling
for my EEG data, and I've tried a number of permutations (e.g., switching
x/y/z axes), but nothing seems to get me close in SimNIBS to this actual
coil position when I use the Nexstim output coords.

*Left Parietal Stimulation Site from the Nexstim Neuronavigation*
[image: Coil direction.png]

*Similar Coil Position in the SimNIBS GUI:*

[image: Coil Pos SimNIBS.png]

Thank you,

*--*
*Alessandra DallaVecchia, M.A.*
PhD candidate, Cognitive Neuroscience
UCLA Department of Psychology
She/her

*If this email finds you outside of your normal business hours, please do
not feel obligated to reply and feel free to respond when you're next
working or in front of a computer.*
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