Use of anodal transcranial direct current stimulation for improving motor performance in healthy adults: A systematic review and meta-analysis

PurposeTranscranial direct current stimulation (tDCS) can noninvasively modulate activity in targeted brain regions. It is well established that the excitability of motor-related regions can increase when the target region is located beneath the anode (anodal tDCS), suggesting its potential to increase motor performance. Although such attempts have been widely examined, the results remain inconclusive. The purpose of this study was to assess the conditions under which anodal tDCS may improve motor performance in healthy adults. MethodsWe conducted a systematic review of studies on the use of anodal tDCS for improving motor performance in healthy adults. A computerized search was performed using the Web of Science, Scopus, PubMed, JDreamIII, and Ichushi-Web to identify relevant studies published between January 1, 1990 and May 25, 2022. ResultsTwenty-five studies were included in the qualitative synthesis. For the meta-analysis, 25 trials (N=885) were extracted from 23 studies. There were significant effects of anodal tDCS on motor performance improvement, but with evidence of publication bias and substantial heterogeneity among the trials. Post-hoc analysis revealed that motor performance 24 hours after the application of anodal tDCS may benefit from stimulation. There was no marked effect related to stimulation intensity, duration, or whether stimulation was provided during motor performance. ConclusionsOur study clarified the current state of anodal tDCS use for motor performance enhancement and indicates that there is currently no reliable evidence to support its effectiveness. Further studies, particularly randomized controlled trials, are necessary to establish the reliability of these effects for future applications.