<![CDATA[Introduction: Various transcranial direct current stimulation (tDCS) montages have been used for primary motor cortex (M1) stimulation. However, montage selection is often based on clinical convention rather than differences in the resulting electric field distribution. Aim: To analize the electric field distribution characteristics of commonly used tDCS montages for left M1 stimulation and discuss their implications for neurorestorative practice. Electric field simulations were performed using SimNIBS based on the finite element method (FEM) and the Ernie Extended head model. Five montages were analyzed: C3–C4, C3–Fp2, C3–Fp1, C3–right deltoid (RDt), and C3–left deltoid (LDt), with the anode placed over C3 and a stimulation intensity of 2 mA. Regional analyses were conducted at C3, Cz, and C4. Distinct electric field distributions were observed across all montages. The C3–C4 montage produced the greatest involvement of the medial sensorimotor region and the contralateral hemisphere, whereas C3–Fp1 generated the most localized distribution within the target hemisphere. The C3–Fp2 montage produced the highest electric field intensity at the target region (C3). Extracephalic montages (C3–RDt and C3–LDt) demonstrated relatively lower contralateral hemispheric involvement compared with the bihemispheric montage. The location of the second electrode substantially influences electric field distribution within the sensorimotor network. Each montage exhibits distinct network recruitment characteristics, suggesting that montage selection should be tailored to the intended neuromodulatory objective and the underlying clinical condition.finite element method; FEM neuromodulation; neurorestoration; primary motor cortex; transcranial direct current stimulation; tDCS]]>
