AUTHOR=Teixeira-Santos Ana C. , Moreira Célia S. , Pereira Diana R. , Pinal Diego , Fregni Felipe , Leite Jorge , Carvalho Sandra , Sampaio Adriana 

TITLE=Working Memory Training Coupled With Transcranial Direct Current Stimulation in Older Adults: A Randomized Controlled Experiment

JOURNAL=Frontiers in Aging Neuroscience

VOLUME=Volume 14 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/aging-neuroscience/articles/10.3389/fnagi.2022.827188

DOI=10.3389/fnagi.2022.827188

ISSN=1663-4365

ABSTRACT=Background: Transcranial direct current stimulation (tDCS) has been employed to boost working memory training (WMT) effects. Nevertheless, there is limited evidence on the efficacy of this combination in older adults. The present study aimed to assess the delayed transfer effects of transcranial direct current stimulation (tDCS) coupled with working memory training (WMT) in older adults in a 15-day follow-up. We explored if general cognitive ability, age, and educational level predicted the effects.
Methods: In this single-center, double-blind randomized sham-controlled experiment, 54 older adults were randomized into three groups: anodal-tDCS+WMT, sham-tDCS+WMT, or
double-sham. Five sessions of tDCS (2 mA) were applied over the left dorsolateral
prefrontal cortex. Far transfer was measured by Raven’s Advanced Progressive Matrices (RAPM), while the near transfer effects were assessed through Digit Span. A frequentist linear mixed model was complemented by a Bayesian approach in data analysis.
Results: WMT improved dual n-back performance in both groups submitted to this intervention but only the group receiving WMT+anodal-tDCS displayed a significant improvement from pretest to follow-up in transfer measures of reasoning (RAPM) and short-term memory (Forward Digit Span). Near transfer improvements predicted gains in far transfer, demonstrating that the far transfer is due to an improvement in the trained construct of working memory. Age and Vocabulary scores seem to predict the gains in reasoning. However, Bayesian results do not provide substantial evidence to support this claim.
Conclusion: This study will help to consolidate the incipient but auspicious field of cognitive training coupled with tDCS in healthy older adults. Our findings demonstrated that anodal tDCS may potentialize WMT by promoting transfer effects in short-term memory and reasoning in older adults, which is observed especially at follow-up.