Objectives: 1) To examine whether the real transcranial direct current stimulation (tDCS) group would perform better in the cognitive training (CT) intervention than the sham tDCS group and the CT group; 2) To determine if, as a consequence of the stimulation generated by the use of tDCS, there would be a transfer effect to other cognitive domains and to cognitive tasks in activities of daily living; 3) To investigate the time and spatial responses of tDCS on the brain cortex during and after tDCS application.

Hypothesis to be tested: By applying anodal tDCS with the combination of a CT delivered via the use of tablet PCs in older adults at risk of MCI, it will enhance their cognitive task performance in CT and subsequently generalize to other cognitive domains as well, involving a transferability to cognitive tasks in activities of daily living.

Design and subjects: A multi-centered single-blinded randomized controlled trial (RCT) with three groups (CT alone/Sham tDCS with the combination of a CT/ Real tDCS coupling with CT) The participants who will take part of this study will be older adults at risk of MCI Study instruments: tDCS, Ipad, Neuron Up CT Apps, EEG. Interventions: The intervention will last for 9 sessions (3 sessions per week for 3 weeks). Sham tDCS and real tDCS, will be combined with the same CT which is used in the CT group. During the experimental intervention, anodal tDCS will be placed on left dorsolateral prefrontal cortex (DLPFC) and cathodal tDCS on the contralateral deltoid muscle with the combination of a CT. During the experimental intervention, anodal tDCS will be placed on left dorsolateral prefrontal cortex (DLPFC) and cathodal tDCS on the contralateral deltoid muscle with the combination of a CT.

Main outcome measures: Cognitive assessments, CT performance, EEG. In addition, delta and theta frequency suppression and alpha increment power under the anode electrode will be observed.

Inclusion Criteria:

• The inclusion criteria will follow the modified Petersen's criteria:

  1. Aged between 60 and 85 years old;

  2. Obtaining a score on the Montreal Cognitive Assessment Test (MoCA) between 19 and 26;

  3. Achieving a score on the Clinical Dementia Rating (CDR) of 0.5 or below ;

  4. Self-reported cognitive decline by the participants themselves and

  5. Being independent in daily living activities.

     Additional criteria in this study include:

  6. Having completed three or more years of primary education;

  7. Ability to participate in a therapy session lasting at least 30 minutes;

  8. Community ambulant with or without aids; and

  9. Ability to perform a proper range of motion with hands in order to use a tablet PC.

Exclusion Criteria:

• 1) Individuals presenting with a diagnosis of dementia or any other neurological disease; (2) Individuals with depression determined by a score on Geriatric Depression Scale of >5, (3) History of drug or alcohol abuse or dependence in the last 3 months; and (4) Participants who had metallic fixtures around the cephalic area or skin lesions in the areas at where the electrodes were going to be attached were excluded from the study.