Effects of Working Memory Training Coupled with tDCS in Older Adults

Aims: The aim of this study was to assess the effects of a 5-day Working Memory Training (WMT) coupled with tDCS on near- (Digit Span) and far- (Raven Advanced Progressive Matrices - RAPM) transfer tasks, as well as, on salivary IGF-1 levels, as a proxy of cellular neuroplasticity.

Method: In this single-center, double-blind randomized sham-controlled experiment, 54 older adults (Mage = 68.6; 32 females) were randomly assigned to one of three groups: 1) WMT (dual n-back task) + atDCS (anodal, 2 mA; 20min; placed over the left dorsolateral prefrontal cortex - DLPFC); 2) WMT + sham tDCS; 3) double-placebo. Five sessions were carried out and assessments were conducted at baseline, post-training, and at a 15-day follow-up. Saliva was also collected at baseline and post-training.

Results: The analyses showed that only the atDCS+WMT group displayed a significant improvement in reasoning (RAPM), at post-training and follow-up, and in short-term memory (forward digit span), at follow-up. Additionally, preliminary analysis showed that, at post-training, tDCS+WMT groups showed a higher IGF-1 level than the other two groups.

Conclusion: Our findings demonstrated that atDCS may potentialize WMT by promoting transfer effects in short-term memory and reasoning in older adults, which are observed especially at follow-up. Furthermore, atDCS effects may also be associated with an increase in IGF-1 levels.