Influence of Anatomical Model and Skin Conductivity on the Electric Field Induced in the Head by Transcranial Magnetic Stimulation

Effect of skin conductivity on the electric field induced by transcranial stimulation techniques in different head models

“…Particularly, it was higher than 10% in a region deep inside the brain, when comparing the two extreme values used for σ s (see figures 4(c) and (f)). Similar findings were obtained in Colella et al (2019) with the coil placed on the top of the head. Such SMAPE distributions could be explained by the fact the effect of skin conductivity variations is more relevant on the normal component of the E-field than it is on the tangential one, and in the deep brain regions the induced E-field is mainly oriented orthogonally to the interfaces between GM, WM and CSF.…”

“…A recent study on a simple multilayered sphere revealed that a 15% change in the skin conductivity, caused a variation of about 1% on the induced E-field in the brain, however much less than those induced by other sources of variability, such as the uncertainty in coil positioning (Gomez et al 2015(Gomez et al , 2018. In a preliminary study (Colella et al 2019) with the TMS coil placed at the top of the head of two anatomical models, the authors found that skin conductivity affected the maximum and the average E-field in the brain in a negligible way with respect to the anatomical differences. Despite the low percentage variations found in previous studies, further investigation of local differences is needed, specially where pain receptors are located, as this would be the site of possible side effects onset.…”