A Preliminary Study of Model-driven Individualized Transcranial Electrical Stimulation for Insomnia

The first and final sessions will include clinical assessments and acquisition of MRI and EEG data. To minimize variability, each patient will undergo tDCS at a consistent time in the afternoon or evening and will remain lying in bed with eyes closed throughout stimulation. Stimulation will be delivered using the GTEN 200 system (Magstim EGI, Oregon, USA), which also enables simultaneous EEG recording. The stimulation current will be limited to 1.5 mA, with a maximum of 0.15 mA per electrode (up to 20 electrodes). Electrode placement and current intensity will be individualized to achieve the targeted electric field strength (0.1 or 0.2 V/m at SMHC;). Each session will include 5 min of resting-state EEG immediately before and after stimulation to assess tDCS-induced changes in brain dynamics. Current onset and offset will be gradual, with 2-s ramp-up and ramp-down periods.