[Simnibs-discuss] tDCS electrode is being simulated as skin

[Gülce Lale]

Dear SimNIBS Team,

We conduct post-hoc modelling for each subject using T1 and T2 images acquired while the participant was in the scanner with the tDCS electrodes attached. Here SimNIBS headreco images the 2mm layer of electrode paste and includes in in the head mesh but segments it as skin (see attached images).

According to SimNIBS skin conductance is 0.465 s/m and the electrode material conductivity is 29.4 s/m. One would expect the Ten20 Electrode paste which is applied with a 2mm thickness between the electrode and skin to have a different measure. However, since it is being considered and modelled as skin this could results in deviations in the electric field modelling.

How do we account/solve this?

Could we model the electrodes 2mm below the head surface, knowing that the outer 2mm thickness of the skin are actually due to the paste? Thus, modelling the electrodes on the “actual” skin outer layer (and not on top of the paste). SimNIBS then allows us to specify past + electrode thickness. Where we assume SimNIBS calculates a different conductivity measure for both.

Is there an alternative solution to best account for the change of conductance?

Thank you for your help in advance.
Best wishes,
Gülce 

Gülce Lale
MSc Neurosciences



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