Upon meeting the inclusion criteria and providing informed consent, each participant will complete a series of cognitive assessments and tDCS at the hospital outpatient clinics or inpatient department. Participants were randomly allocated to anode tDCS group with cognitive training, anode tDCS group and the sham group. There are about 20 participants in each group. Participants were studied using a double-blind design. Study participants and all personnel responsible for the effects of the participants remained masked to allocated condition and allocation parameters. Only tDCS administrators had access to the randomization list; they had minimal contact with the participants, and no role in cognitive assessments. For the first 30 participants, allocation was decided by draw. For the subsequent 30 patients, allocation was according to computer generated random numbers. Each participant would be treated for 10 days in two weeks by HD-tDCS.~Before the tDCS, a series of cognitive assessments and neuropsychological tests were obtained by a trained investigator to assess baseline. Each assessment will involve a set of assessment tools, including Alzheimer's Disease Assessment Scale-Cognitive Subscale (ADAS-Cog), Montreal Cognitive Assessment (MoCA) and associative memory as the primary outcome measure and various other tasks and questionnaires to measure cognition(DS, Stroop test, VFT, SDMT), memory (AVLT, AMT, working memory test), emotion(HAMA-17, HAMD-14, eye-tracking technolodgy), executive function(SST, WSCT, GDT) and stimulation tolerability. All the tests are conducted in two days. The participants had receiving a magnetic resonance imaging scan in multi-modalities, and electroencephalography (EEG) record.~Evaluations were conducted one week after treatment and at the end of two weeks of treatment, as well as the Global Index of Safety to assess adverse events of the stimulation. Participants were instructed to focus their answers on the past 7/14 days. The participants had also receiving a battery measure of neuropsychological tests, magnetic resonance imaging scan in multi-modalities, and EEG record. All tests were instructed to finished within 24 hours after the last stimulation. One month and three months after the last stimulation, participants were interviewed to obtain the same assessment as before. They were instructed to focus their answers on the past months.
To investigate the clinical effect neural mechanism of high-definition transcranial direct current stimulation combined with cognitive training on early AD