All patients underwent a medical evaluation that include physical examinations and routine laboratory studies before and after stimulation sessions. Patients were randomly allocated to tACS, tDCS, and sham groups. There are about 20 patients in each group. Allocation was by computer generating random numbers. The decision to enroll a patient was always made prior to randomization. Patients were studied using a double-blind design. Study participants, clinical raters, and all personnel responsible for the clinical care of the patient remained masked to allocated conditions and allocation parameters. Only stimulation administrators had access to the randomization list; they had minimal contact with the patients, and no role in assessing the UPDRS(Unified Parkinson´s Disease Rating Scale), Hoehn & Yahr, and MoCA(Montreal Cognitive Assessment). Each patient would be treated for 20 minutes of transcranial electrical stimulation.~Before the stimulation session, UPDRS, Hoehn & Yahr, and MoCA were obtained by a trained investigator to assess the baseline severity of symptoms. The patients received electroencephalography (EEG) recorded during resting state for 5 minutes.~During the stimulation session, patients were asked to perform simple reaction tasks at the same time.~After the stimulation session, UPDRS, Hoehn & Yahr, and MoCA were obtained, as well as the Global Index of Safety（tES slide effects） to assess adverse events of the treatment. The patients also received a measure of electroencephalography (EEG) recorded during the resting state and a simple reaction task.
To investigate the difference in the treatment efficacy between transcranial direct current stimulation and transcranial alternating current stimulation on Parkinson's disease, including the improvements in the motor, cognitive, and underlying neural mechanisms behind differences in efficacy by electroencephalography (EEG).