The impact of paired cognitive training with transcranial direct current stimulation on everyday functioning for older adults with mild cognitive impairment – beyond conventional testing

Background: Cognitive Training (CT) is a non-pharmacological therapy that may enhance cognitive function, yet little evidence supports the transfer of cognitive improvement to real-life situations when applied to individuals with mild cognitive impairment (MCI). CT strengthens neural circuits during practice, circuits that could be targeted by transcranial direct current stimulation (tDCS) to increase the likelihood of transmission across neurons and alter behaviour. Concurrent CT and tDCS may produce superior transfer effects noticeable in everyday function.
Objective: To investigate the efficacy of CT coupled with multisession tDCS to produce transfer effects of everyday memory in older adults with MCI.
Methods: Sixty-seven older adults with MCI participated in a randomised double-blind trial and were assigned to three groups: 1) tDCS combined with CT (tDCS+CT), 2) sham tDCS combined with CT (sham tDCS+CT) and 3) CT alone. All groups received nine sessions of computerised CT based on executive function over three weeks. Stimulation groups (verum and sham) received tDCS to the left prefrontal cortex and the contralateral brachioradialis muscle (anode left, cathode right) with concurrent CT. The Rivermead Behavioural Memory Test-3 (RBMT) was administered at baseline, post-intervention, and at six-week follow-up.
Results: Total RBMT score improved in all groups after intervention and at follow-up (p < 0.017) with a larger effect noted in the tDCS+CT group (d > 0.94). No tDCS specific effect was found between groups for total RBMT score (p = 0.97). Within-group differences were noted for RBMT sub-scores verbal, visual, prospective memory and new learning (p< 0.02).
Conclusions: Computerised CT of executive function appears to produce robust transfer effects of enhanced everyday memory, yet concurrent tDCS provides no superior transfer effect.