title: Evaluation of local electric fields generated by transcranial direct current stimulation with an extracephalic reference electrode based on realistic 3D body modeling.
abstract: In this study, local electric field distributions generated by transcranial direct current stimulation (tDCS) with an extracephalic reference electrode were evaluated to address extracephalic tDCS safety issues. To this aim, we generated a numerical model of an adult male human upper body and applied the 3D finite element method to electric current conduction analysis. In our simulations, the active electrode was placed over the left primary motor cortex (M1) and the reference electrode was placed at six different locations: over the right temporal lobe, on the right supraorbital region, on the right deltoid, on the left deltoid, under the chin, and on the right buccinator muscle. The maximum current density and electric field intensity values in the brainstem generated by the extracephalic reference electrodes were comparable to, or even less than, those generated by the cephalic reference electrodes. These results suggest that extracephalic reference electrodes do not lead to unwanted modulation of the brainstem cardio-respiratory and autonomic centers, as indicated by recent experimental studies. The volume energy density was concentrated at the neck area by the use of deltoid reference electrodes, but was still smaller than that around the active electrode locations. In addition, the distributions of elicited cortical electric fields demonstrated that the use of extracephalic reference electrodes might allow for the robust prediction of cortical modulations with little dependence on the reference electrode locations.
authors.affiliation: Department of Biomedical Engineering, Hanyang University, Seoul, Korea. ich@hanyang.ac.kr
authors.forename: Chang-Hwan
authors.initials: CH
authors.lastname: Im
authors.forename: Ji-Hye
authors.initials: JH
authors.lastname: Park
authors.forename: Miseon
authors.initials: M
authors.lastname: Shim
authors.forename: Won Hyuk
authors.initials: WH
authors.lastname: Chang
authors.forename: Yun-Hee
authors.initials: YH
authors.lastname: Kim
mesh_terms: D000328:Adult; D001933:Brain Stem; D004553:Electric Conductivity; D004558:Electric Stimulation / Q000295:instrumentation*; D004566:Electrodes; D057918:Fiducial Markers; D020342:Finite Element Analysis; D006801:Humans; D008297:Male; D012886:Skull; D013116:Spinal Cord