Transcranial Alternating Current Stimulation

Patients in the tACS group received a total of 15 sessions of brain stimulation. The sessions were conducted on weekdays (from Monday to Friday) for three consecutive weeks. Each session lasted 30 minutes. The alternating current stimulations were generated by a CVFT-MG201 machine. Stimulations were delivered by two U-shaped electrodes (approximately 7 cm2) fixed on the patient's left and right mastoid regions (anode or cathode varied depending on polarity of the alternating current). The frequencies (supra-slow waves: \< 1 Hz; theta to gamma), levels of intensities (0 to 3mA), and density function (follows a bell-shaped curve; mean intensity \~ 2.1mA) of the current were delivered according to the manufacturer's pre-set random protocol.