Meta-Analysis
Copyright ©The Author(s) 2025. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Psychiatry. Sep 19, 2025; 15(9): 107754
Published online Sep 19, 2025. doi: 10.5498/wjp.v15.i9.107754
Effect of theta-transcranial alternating current stimulation on working memory performance among healthy adults: A systematic review and meta-analysis
Tian-Ya Hou, Xiao-Fei Mao, Rui-Ke Zhang
Tian-Ya Hou, Xiao-Fei Mao, Rui-Ke Zhang, Faculty of Psychology, Naval Medical University, Shanghai 200433, China
Co-corresponding authors: Xiao-Fei Mao and Rui-Ke Zhang.
Author contributions: Hou TY and Zhang RK designed the experiment and wrote the manuscript; Hou TY analyzed the data; Mao XF and Zhang RK made equal contributions as co-corresponding authors; all authors contributed to the critical revision, editing of the article, prepared the draft and approved the submitted version.
Supported by Shanghai Municipal Health Commission’s Special Clinical Research Project for the Hygiene Industry, No. 20244Y0041; and Youth Initiation Fund of Naval Medical University, No. 2023QN028 and No. 2023QN030.
Conflict-of-interest statement: All the authors report no relevant conflicts of interest for this article.
PRISMA 2009 Checklist statement: The authors have read the PRISMA 2009 Checklist, and the manuscript was prepared and revised according to the PRISMA 2009 Checklist.
Open Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: https://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Rui-Ke Zhang, Lecturer, Faculty of Psychology, Naval Medical University, No. 800 Xiangyin Raod, Shanghai 200433, China. zrk_2015@163.com
Received: April 1, 2025
Revised: May 22, 2025
Accepted: July 24, 2025
Published online: September 19, 2025
Processing time: 150 Days and 23.4 Hours
Abstract
BACKGROUND

Working memory serves as a fundamental cognitive function that substantially impacts performance in various cognitive tasks. Extensive neurophysiological research has established that theta oscillations (4-8 Hz) play an essential role in supporting working memory operations. Theta-band transcranial alternating current stimulation (tACS) offers a potential mechanism for working memory enhancement through direct modulation of these fundamental neural oscillations. Nevertheless, current empirical evidence shows substantial variability in the observed effects of theta-tACS across studies.

AIM

To conduct a systematic review and meta-analysis evaluating the effects of theta-tACS on working memory performance in healthy adults.

METHODS

A systematic literature search was performed on PubMed, EMBASE, and Web of Science up to March 10, 2025. Effect sizes were computed using Hedges’ g with 95% confidence intervals (CIs), with separate meta-analyses for all included studies and for distinct working memory paradigms [n-back and delayed match-to-sample (DMTS) tasks] to examine potential task-specific effects. Subgroup analyses and meta-regression were performed to evaluate the influence of key moderating variables.

RESULTS

The systematic review included 21 studies (67 effect sizes). Initial meta-analysis showed theta-tACS moderately improved working memory (Hedges’ g = 0.405, 95%CI: 0.212-0.598). However, this effect became nonsignificant after correcting for publication bias (trim-and-fill adjusted Hedges’ g = 0.082, 95%CI: -0.052 to 0.217). Task-specific analyses revealed significant benefits in n-back tasks (Hedges’ g = 0.463, 95%CI: 0.193-0.733) but not in DMTS tasks (Hedges’ g = 0.257, 95%CI: -0.186 to 0.553). Moderator analyses showed that performance in n-back tasks was influenced by stimulation frequency (P = 0.001), concurrent status (P = 0.014), task modality (P = 0.005), and duration (P = 0.013), whereas only the region of targeted stimulation (P = 0.012) moderated DMTS tasks.

CONCLUSION

Theta-tACS enhances working memory in healthy adults, with effects modulated by the task type and protocol parameters, offering dual implications for cognitive enhancement and clinical interventions.

Keywords: Working memory; Transcranial alternating current stimulation; Theta; Healthy adults; N-back; Delayed match-to-sample task

Core Tip: In this meta-analysis, we evaluated theta-band transcranial alternating current stimulation for working memory enhancement in healthy adults. Although initial analyses showed moderate efficacy, correction for publication bias rendered effects nonsignificant. Notably, task-specific effects emerged, specifically showing significant improvement in n-back tasks vs null effects in delayed match-to-sample tasks. Key moderators of performance included stimulation frequency, concurrent status, task modality, and stimulation duration for n-back tasks and the target region for match-to-sample tasks. Although these findings primarily guide cognitive enhancement protocols for healthy individuals, they also provide mechanistic insights for potential clinical translation to populations with working memory deficits.