Transcranial direct current stimulation as an adjunct to cognitive training for older adults with mild cognitive impairment

Background: Cognitive training (CT) for persons with mild cognitive impairment (MCI) may not be optimal for enhancing cognitive functioning. Combining CT with transcranial direct current stimulation (tDCS) may maximise the strength of transmission across synaptic circuits in pathways that are stimulated by CT. The synergistic effects of CT and tDCS may be superior to those of CT alone. Objectives: To investigate whether tDCS combined with CT (tDCS+CT) is superior to CT alone in terms of domain-specific and task-specific cognitive outcomes in older adults with MCI. Methods: This double-blind, sham-controlled randomised trial included 67 older adults with MCI assigned to three groups: tDCS+CT, sham tDCS+CT, and CT alone. Nine sessions of computerised CT were administered for 3 weeks. Simultaneously with CT, tDCS or sham tDCS was delivered to the left dorsolateral prefrontal cortex. Standardised cognitive assessments were carried out at baseline, post-intervention, and at 6-week follow-up. Participants' performance in the CT tasks was rated every session. Results: All three groups had improvements in global cognition and everyday memory (p0.94). The tDCS+CT group had the highest decrease in the completion and reaction times of working memory and attention activities (p