Frontoparietal neurostimulation modulates working memory training benefits and oscillatory synchronization

Abstract

There is considerable interest in maintaining working memory (WM) because it is essential to accomplish most cognitive tasks, and it is correlated with fluid intelligence and ecologically valid measures of daily living. Toward this end, WM training protocols aim to improve WM capacity and extend improvements to unpracticed domains, yet success is limited. One emerging approach is to couple WM training with transcranial direct current stimulation (tDCS). This pairing of WM training with tDCS in lon gitudinal designs promotes behavioral improvement and evidence of transfer of performance gains to untrained WM tasks. However, the mechanism(s) underlying tDCS-linked training benefits remain unclear. Our goal was to gain purchase on this question by recording high-density EEG before and after a weeklong WM training + tDCS study. Participants completed four sessions of frontoparietal tDCS (active anodal or sham) during which they performed a visuospatial WM change detection task. Participants who received active anodal tDCS demonstrated significant improvement on the WM task, unlike those who received sham stimulation. Importantly, this pattern was mirrored by neural correlates in spectral and phase synchrony analyses of the HD-EEG data. Notably, the behavioral interaction was echoed by interactions in frontal-posterior alpha band power, and theta and low alpha oscillations. These findings indicate that one mechanism by which paired tDCS + WM training operates is to enhance cortical efficiency and connectivity in task-relevant networks.

Predicting Working Memory Training Benefits From Transcranial Direct Current Stimulation Using Resting-State fMRI

“…Some evidence shows that one session of tDCS can improve WM performance in healthy ( Sandrini et al, 2012 ; Brunoni and Vanderhasselt, 2014 ; Trumbo et al, 2016 ; Brunye et al, 2017 ), and patient populations ( Boggio et al, 2006 ; Jo et al, 2009 ; Saunders et al, 2015 ; Wu et al, 2016 ), reviewed in Berryhill and Martin (2018) . In contrast to the variability in single-session protocols, tDCS-WM training protocols show more consistent WM benefits ( Martin et al, 2013 ; Richmond et al, 2014 ; Jones et al, 2015b , 2017 ; Au et al, 2016b ; Stephens and Berryhill, 2016 ; Katz et al, 2017 ; Ke et al, 2019 ; but see: Möller et al, 2017 ). However, the jury remains split as several reviews, and meta-analyses provide differing conclusions, suggesting that there are few cognitive benefits associated with tDCS ( Horvath et al, 2015 ), that meta-analyses minimizing tDCS-effects are flawed ( Antal et al, 2015 ), or that there are benefits under certain conditions, such as longitudinal designs ( Brunoni and Vanderhasselt, 2014 ; Elmasry et al, 2015 ; Hill et al, 2016 ; Jantz et al, 2016 ; Mancuso et al, 2016 ).…”

Review of the Neural Processes of Working Memory Training: Controlling the Impulse to Throw the Baby Out With the Bathwater

“…In another tDCS study, Jones and colleagues attempted to better understand how tDCS creates cognitive gains reflected in brain function when coupled with WMT ( 84 ). To this aim, EEG recordings were taken before and after a week of visuospatial WM change detection training, during which participants completed four sessions of frontoparietal tDCS (active anodal or sham).…”

Executive Function Deficits in Seriously Ill Children—Emerging Challenges and Possibilities for Clinical Care

“…For these reasons and since the functional relevance of the oscillations in question remains to be investigated further, tACS should be classified as a rather experimental, but promising approach at this stage. Interestingly, another neuromodulation approach (transcranial direct current stimulation (tDCS)) has recently been used in conjunction with a short behavioral training, with this specific combination of interventions leading to (i) significant working memory improvements and (ii) changes in theta/alpha oscillations in a small group of healthy controls ( 85 ). Although its effects on neuronal oscillations may be of a more indirect or supportive nature, tDCS could thus also constitute a promising and safe ( 86 ) approach in this regard.…”

“…Furthermore, elements from cognitive-behavioral therapy (and in fact also the aforementioned cognitive training approaches) are an essential part of neuronal oscillation-based treatment approaches ( 72 , 85 ). In addition, for home-treatment approaches, families need to be provided with a detailed introduction to the technical aspects of the treatment (e.g., how to set up the system, connect electrodes, conduct troubleshooting).…”