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Transcranial direct current stimulation and working memory: Comparison of effect on learning shapes and English letters

Lookup NU author(s): Dr Sriharsha Ramaraju



This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).


We present the results of a study investigating whether there is an effect of Anodal-Transcranial Direct Current Stimulation (A-tDCS) on working memory (WM) performance. The relative effectiveness of A-tDCS on WM is investigated using a 2-back test protocol using two commonly used memory visual stimuli (shapes and letters). In a double-blinded, randomised, crossover, sham-controlled experiment, real A-tDCS and sham A-tDCS were applied separately to the left dorsolateral prefrontal cortex (L-DLPFC) of twenty healthy subjects. There was a minimal interval of one week between sham and real A-tDCS sessions. For the letters based stimulus experiment, 2-back test recall accuracy was measured for a set of English letters (A-L) which were presented individually in a randomised order where each was separated by a blank interval. A similar 2-back protocol was used for the shapes based stimuli experiment where instead of letters, a set of 12 geometric shapes were used. The working memory accuracy scores measured appeared to be significantly affected by memory stimulus type used and by the application of A-tDCS (repeated measures ANOVA p<0.05). A large effect size (d = 0.98) and statistical significance between sham and real A-tDCS WM scores (p = 0.01) was found when shapes were used as a visual testing stimulus, while low (d = 0.38) effect size and insignificant difference (p = 0.15) was found when letters were used. This results are important as they show that recollection different stimuli used in working memory can be affected differently by A-tDCS application. This highlights the importance of considering using multiple methods of WM testing when assessing the effectiveness of A-tDCS.

Publication metadata

Author(s): Ramaraju S, Roula MA, McCarthy PW

Publication type: Article

Publication status: Published

Journal: PLoS one

Year: 2020

Volume: 15

Issue: 7

Online publication date: 24/07/2020

Acceptance date: 25/06/2020

Date deposited: 10/08/2020

ISSN (electronic): 1932-6203

Publisher: Public Library of Science


DOI: 10.1371/journal.pone.0222688

PubMed id: 32706780


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