[Simnibs-discuss] Position window and efield

[Guilherme B Saturnino]

Dear Jade,


Thanks a lot for your interest in SimNIBS.


/in the position window, and next to the dropdown box for the EEG cap 
positions, are these x y z coordinates that I can input in MNI space?/


These positions are in world space of the input scan. However, you can 
easily transform between subject space and MNI space. Please see here 
for more information:

https://simnibs.github.io/simnibs/build/html/documentation/coordinates.html


You could also skip the GUI completely and setup simulations with python 
or matlab scripts where you input MNI coordinates directly. Examples:


https://github.com/simnibs/simnibs/blob/master/simnibs/examples/simulations/TMS_MNI.m

https://github.com/simnibs/simnibs/blob/master/simnibs/examples/simulations/TMS_MNI.py



/Also, if I generate a model with stimulation to specific coordinates 
and then calculate the norm Efield at the control ROI, what does the 
output equate to? How can I know if this is equivalent to say their 
motor threshold?
/

/
/

The output is an electric field in V/m. We know that electric fields and 
motor threshold in TMS are correlated (see
https://doi.org/10.1093/cercor/bhw292, 
https://doi.org/10.1016/j.neuroimage.2019.116486, https://doi.org/ 
<https://doi.org/10.1016/j.neuroimage.2019.116486>10.1016/j.brs.2017.09.011 
<https://doi.org/10.1016/j.brs.2017.09.011>). But the relationship 
between the two is complex. So we can't say at the moment that if the 
electric field in a given region (for example hand knob) is above a 
certain value you will for sure an MEP, but rather that a larger 
electric field increases the probability of getting an MEP.


Best Regards,

Guilherme



On 03/03/2020 16.05, Jade Jackson wrote:
>
> Dear developers,
>
>
> Thank you for developing this toolbox. I have specific MNI coordinates 
> that I want to stimulate and I want to understand whether the 
> stimulation will spread to a control ROI, and if so, to what degree.
>
> I have a couple of very basic questions, in the position window, and 
> next to the dropdown box for the EEG cap positions, are these x y z 
> coordinates that I can input in MNI space? Also, if I generate a model 
> with stimulation to specific coordinates and then calculate the norm 
> Efield at the control ROI, what does the output equate to? How can I 
> know if this is equivalent to say their motor threshold?
>
> Thanks,
>
> Jade
>
>
> _______________________________________________
> Simnibs-discuss mailing list
> Simnibs-discuss at drcmr.dk
> https://mailman.drcmr.dk/mailman/listinfo/simnibs-discuss
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