FEM Electromagnetic Dosimetry Analysis of Motor Cortex Plasticity Modulation by HD-tDCS

The modulation of cortical plasticity within the primary motor cortex through HighDefinition Transcranial Direct Current Stimulation (HD-tDCS) represents a significantadvancement in non-invasive brain stimulation technologies. While conventional tDCS hasdemonstrated efficacy in altering cortical excitability, its spatial lack of focality necessitatesthe adoption of high-definition montages to target specific neuroanatomical substrateseffectively. This paper presents a comprehensive Finite Element Method (FEM) analysis ofelectromagnetic dosimetry to quantify the electric field distribution and current densityinduced by HD-tDCS montages targeting the M1 region. By utilizing high-resolutionstructural magnetic resonance imaging data to construct individualized head models, wesimulate the biophysical interaction between applied currents and heterogeneous cranialtissues. The study incorporates anisotropic conductivity tensors derived from diffusion tensorimaging to enhance the predictive accuracy of the models. Our results elucidate the focalbenefits of the 4x1 ring configuration compared to conventional pad electrodes,demonstrating a significant increase in field magnitude localized to the precentral gyrus.Furthermore, we analyze the correlation between the normal component of the electric fieldand the induction of long-term potentiation-like plasticity effects. The findings suggest thatFEM-based dosimetry is an indispensable tool for optimizing stimulation protocols, reducinginter-individual variability, and predicting clinical outcomes in neurorehabilitation contexts.