The effects of transcranial direct current stimulation on within- and cross-paradigm transfer following multi-session backward recall training

https://doi.org/10.1016/j.bandc.2020.105552Get rights and content
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Highlights

  • Randomised controlled trial combining backward recall memory training and tDCS.

  • Systematic investigation into task features constraining training transfer.

  • Measurement of potential benefits of tDCS for training and for transfer across tasks with varying degrees of overlap with training task.

  • Training transfer is constrained by paradigm but not task materials.

  • tDCS over left DLPFC (1 mA, 10 min) does not enhance training or transfer.

Abstract

Transcranial direct current stimulation (tDCS) has been shown to enhance the efficacy and generalisation of working memory (WM) training, but there has been little systematic investigation into how coupling task-specific WM training with stimulation impacts more specifically on transfer to untrained tasks. This randomised controlled trial investigated the boundary conditions to transfer by testing firstly whether the benefits of training on backward digit recall (BDR) extend to untrained backward recall tasks and n-back tasks with different materials, and secondly which, if any, form of transfer is enhanced by tDCS. Forty-eight participants were allocated to one of three conditions: BDR training with anodal (10 min, 1 mA) or sham tDCS, or visual search training with sham tDCS, applied over the left dorsolateral prefrontal cortex. Transfer was assessed on within- (backward recall with digits, letters, and spatial locations) and cross-paradigm (n-back with digits and letters) transfer tests following three sessions of training and stimulation. On-task training gains were found, with transfer to other backward span but not n-back tasks. There was little evidence that tDCS enhanced on-task training or transfer. These findings indicate that training enhances paradigm-specific processes within WM, but that tDCS does not enhance these gains.

Keywords

Working memory
Cognitive training
Transcranial direct current stimulation
tDCS
Brain stimulation

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