Progressively causes the breakdown of cognitive functions and impairs quality of life for patients and their caregivers. In addition to memory impairment, visual attention is also compromised, even at the stage of mild cognitive impairment due to AD (MCI-AD). No treatment has been found for MCI-AD; therefore, attention has been drawn to non-invasive brain stimulation techniques, such as transcranial direct current stimulation (tDCS), in order to enhance cognitive functions by modifying brain plasticity. In the current research, investigator aim to examine the long-term effects of the optimal multiple-session tDCS protocol in MCI-AD on visual attention including the transfer to an ecologically valid virtual environment and identify the neural underpinnings of tDCS-induced behavioral aftereffects using a combined tDCS/ MRI network-based approach.

Investigator will investigate the long-term effects of 10 active tDCS consecutive sessions using an optimized stimulation protocol as compared to a placebo stimulation on visual attention in the MCI-AD. A two-parallel-group, randomized, placebo-controlled design will be used. In addition, the cognitive transfer of tDCS will be evaluated. Repeated tDCS sessions will be performed in 10 consecutive sessions (2 weeks: Monday to Friday) over one preselected ROI together with ongoing visual attention training. During the stimulation, investigator will use the visual matching task. Before the repeated stimulation sessions, participants will undergo the neurocognitive examination. Behavioral examinations of the trained and untrained tasks (i.e. the transfer tasks) will be performed to assess the baseline performance. MRI protocol consisting of T1, T2, FLAIR, and fMRI during the task performance (visual matching task), resting state fMRI, and DTI sequences will be acquired before and after the whole 10-day stimulation protocol in order to search for active vs. placebo tDCS-induced changes in brain activation and resting state functional and structural connectivity and to identify neural correlates of behavioral changes. Behavioral assessment of the trained task and the transfer task will be repeated immediately after and again at a one-month follow-up visit after the end of the last stimulation session

Inclusion Criteria:

• amnestic single or multi-domain mild cognitive impairment patients in accordance with diagnostic criteria (Albert et al., 2011)

Exclusion Criteria:

• psychiatric disorders, including major depression, major vascular lesions, and other brain pathologies detected by MRI that might present with cognitive decline
• a cardio pacemaker or any MRI-incompatible metal in the body
• epilepsy
• any diagnosed psychiatric disorder
• alcohol/drug abuse
• lack of cooperation
• presence of dementia.