Transcranial electrical stimulation improves cognitive training effects in healthy elderly adults with low cognitive performance

Objective: To investigate the efficacy of transcranial direct (tDCS) or alternating current stimulation (tACS) in boosting cognitive training efficiency in healthy older adults. We further explored whether such improvements depend on general cognitive performance or age. Methods: In this randomized, sham-controlled study, 59 healthy elderly participants (mean age 71.7) were assigned to receive computer-based cognitive training (10 sessions, 50 min, twice weekly) com-bined with tDCS (2 mA), tACS (5 Hz), or sham stimulation over the left dorsolateral prefrontal cortex (20 minutes). Cognitive performance was assessed with the Montreal Cognitive Assessment (MoCA), and a cognitive composite score derived from a broad neuropsychological test battery before and imme-diately after the intervention as well as at 6 and 12 months follow-ups. Results: Performance in the cognitive composite score improved significantly in all groups but was not further modulated by neurostimulation. Additional analyses revealed that participants with a low initial MoCA score (<1SD) improved significantly more in the tDCS than in the sham group. Conclusion: TDCS increased the efficacy of cognitive training, but only in participants with initially low general cognitive performance. Significance: Cognitive interventions including tDCS should address baseline performance as modulating factor of cognitive outcomes. (c) 2021 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

The study aimed to investigate the impact of tDCS or tACS on cognitive training efficiency in healthy older adults, finding that tDCS can enhance the effectiveness of cognitive training but only in participants with initially low general cognitive performance.