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Review
. 2020 Nov;50(15):2465-2486.
doi: 10.1017/S0033291720003670. Epub 2020 Oct 19.

Efficacy of non-invasive brain stimulation on cognitive functioning in brain disorders: a meta-analysis

Marieke J Begemann  1 , Bodyl A Brand  1 , Branislava Ćurčić-Blake  1 , André Aleman  1 , Iris E Sommer  1
Affiliations
Review

Efficacy of non-invasive brain stimulation on cognitive functioning in brain disorders: a meta-analysis

Marieke J Begemann et al. Psychol Med. 2020 Nov.

Abstract

Background: Cognition is commonly affected in brain disorders. Non-invasive brain stimulation (NIBS) may have procognitive effects, with high tolerability. This meta-analysis evaluates the efficacy of transcranial magnetic stimulation (TMS) and transcranial Direct Current Stimulation (tDCS) in improving cognition, in schizophrenia, depression, dementia, Parkinson's disease, stroke, traumatic brain injury, and multiple sclerosis.

Methods: A PRISMA systematic search was conducted for randomized controlled trials. Hedges' g was used to quantify effect sizes (ES) for changes in cognition after TMS/tDCS v. sham. As different cognitive functions may have unequal susceptibility to TMS/tDCS, we separately evaluated the effects on: attention/vigilance, working memory, executive functioning, processing speed, verbal fluency, verbal learning, and social cognition.

Results: We included 82 studies (n = 2784). For working memory, both TMS (ES = 0.17, p = 0.015) and tDCS (ES = 0.17, p = 0.021) showed small but significant effects. Age positively moderated the effect of TMS. TDCS was superior to sham for attention/vigilance (ES = 0.20, p = 0.020). These significant effects did not differ across the type of brain disorder. Results were not significant for the other five cognitive domains.

Conclusions: Our results revealed that both TMS and tDCS elicit a small trans-diagnostic effect on working memory, tDCS also improved attention/vigilance across diagnoses. Effects on the other domains were not significant. Observed ES were small, yet even slight cognitive improvements may facilitate daily functioning. While NIBS can be a well-tolerated treatment, its effects appear domain specific and should be applied only for realistic indications (i.e. to induce a small improvement in working memory or attention).

Keywords: Brain disorder; cognitive dysfunction; non-invasive brain stimulation; prefrontal cortex; repetitive transcranial magnetic stimulation; transcranial direct current stimulation.

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Conflict of interest statement

The authors report no potential conflicts of interest.

Figures

Fig. 1.
Fig. 1.
PRISMA flow diagram of the performed literature search. PRISMA, Preferred Reporting Items for Systematic Reviews and Meta-Analyses, dementia, depression, SZ (schizophrenia), MS (multiple sclerosis), PD (Parkinson's diseases), stroke and TBI (traumatic brain injury).
Fig. 2.
Fig. 2.
Forest plots of the effect of tDCS and TMS on working memory and tDCS on attention/vigilance. Results are summarized for all studies, sorted by brain disorder. (a) Forest plot of the effect of tDCS on attention/vigilance, outlier excluded. (b) Forest plot of the effect of TMS on working memory. (c) Forest plot of the effect of tDCS on working memory. BACS, Brief Assessment of Cognition in Schizophrenia; CDR, Cognitive Drug Research Computerized Assessment System; PAL, Paired Associate Learning; RBANS, Repeatable Battery for the Assessment of Neuropsychological Status; SWM, Spatial Working Memory; WMS, Wechsler Memory Scale; WM, Working Memory.
Fig. 3.
Fig. 3.
Meta-regression of the effect of TMS on working memory. Study-samples depicted by circles proportional to their sample size. The x-axis represents the mean age of the study-samples in years, y-axis depicts the effect size (Hedges' g).
See this image and copyright information in PMC

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