 The purpose of the study is to investigate the effect of High Density- tDCS HD- tDCS on cognitive function in Alzheimers Disease. One anode and four return electrodes are placed over DLPFC, where low intensity current 2mA is induced to the surface of the scalp. Electrode placement is individualized for each participant. Participants will undergo 15 stimulations, with a duration of 20 minutes each. All patients will undergo neuropsychological assessment and MRI evaluation. 