Code for: Systematic review and network meta-analysis of anodal tDCS effects on verbal episodic memory: Modelling heterogeneity of stimulation locations

Code for: Bartl, G. J., Blackshaw, E., Crossman, M., Allen, P., & Sandrini, M. (2020). Systematic review and network meta-analysis of anodal tDCS effects on verbal episodic memory: Modeling heterogeneity of stimulation locations. Zeitschrift für Psychologie, 228(1), 3–13. https://doi.org/10.1027/2151-2604/a000396 R code (metaregression_rscript) for metaregresion: Annotated script performing the following: loads necessary packages, downloads dataset, runs metregression, runs Eggers test, calculates confidence interval for tau squared. R code (nma_rscript) for network meta-analysis: Annotated script performing the following: loads necessary packages, downloads dataset, runs network meta-analysis, creates graph, ranks treatment arms, creates forest plot. There is growing interest in the study of transcranial direct current stimulation (tDCS), a non-invasive brain stimulation technique, as an effective intervention to improve memory. In order to evaluate the relative efficacy of tDCS based on the location of anodal electrode sites, we conducted a systematic review examining the effect of stimulation applied during encoding on subsequent verbal episodic memory in healthy adults. We performed a network meta-analysis of 20 studies (23 experiments) with N = 978 participants. Left ventrolateral prefrontal and temporo-parietal sites appeared most likely to enhance episodic memory, although any significant effects were based on findings from single studies only. We did not find evidence for verbal retrieval enhancement of tDCS versus sham stimulation where the effect was based on more than one experimental paper. More frequent replication efforts and stricter reporting standards may improve the quality of evidence and allow more precise estimation of population-level effects of tDCS. GB received project-specific funding from Santander UK. GB and EB are supported by the Vice-Chancellor’s Scholarship from the University of Roehampton. Analysis code for metaregression; Analysis code for network meta-analysis