Influence of White Matter Anisotropy on the Effects of Transcranial Direct Current Stimulation: A Finite Element Study

Abstract

Although the use of transcranial direct current stimulation (tDCS), a noninvasive brain stimulation technique, has become popular in cognitive neuroscience research and clinical applications, there still exists limited knowledge on how to optimally use tDCS for the brain stimulation. To understand the underlying principles and effects of tDCS, finite element analysis (FEA) has been successfully applied due to its truly volumetric analysis and capability of incorporating the anisotropic tissue property. However, there are still many factors to be considered in stimulation: the influence of the white matter (WM) anisotropy is one of them which has not been considered in tDCS. In this study, we have examined the influence of the WM anisotropic conductivities on tDCS via high-resolution FE head models of the whole head. The effects of the WM anisotropy has been assessed by comparing the current density maps computed from the anisotropic FE model against those of the isotropic model using the similarity measures. The results show that there are significant differences caused by the tissue anisotropy, indicating that the anisotropic electrical conductivity is one of the critical factors to be considered during tDCS for accurate and effective stimulation of the brain.