Effects of transcranial electric stimulation on attentional functions in healthy adults: A meta-analysis

Non-invasive brain stimulation techniques, such as transcranial electric stimulation (tES), are increasingly promoted as methods to enhance attention. However, their efficacy and optimal stimulation targets remain uncertain. We conducted a preregistered meta-analysis of randomized controlled trials in healthy adults (58 trials, 295 outcomes) examining the effects of tES on attentional functions (PROSPERO: CRD42023487035), complemented by a performance-electric field correlation (PEC) analysis to identify brain regions most strongly linked to tES-induced behavioral improvements. In general, tES produced a small but significant improvement in attentional functions compared to control conditions (standardized mean difference [SMD] = 0.24, 95% confidence interval [CI] = 0.12-0.36, I² = 61%). Small but consistent benefits were observed in trials assessing attentional functions after stimulation (40 trials, SMD = 0.23, 95% CI = 0.12-0.33, I² = 39%) and in trials applying anodal transcranial direct current stimulation (tDCS) targeting prefrontal regions (vs sham; 31 trials, SMD = 0.26, 95% CI = 0.12-0.39, I² = 46%) with no evidence of publication bias or serious imprecision. The PEC analysis further revealed that tDCS-induced electric fields in the ventral subregion of the left dorsolateral prefrontal cortex (left vDLPFC) were most strongly associated with improvements in attentional functions following tDCS. Taken together, these findings suggest that tES may enhance attentional functions and the left vDLPFC may be a potential target for future tES studies aiming to improve attention.