Neurofeedback of Alpha Activity on Memory in Healthy Participants: A Systematic Review and Meta-Analysis

Abstract

Background: Neurofeedback training (NFT) has recently been proposed as a valuable technique for cognitive enhancement and psychiatric amelioration. However, effect of NFT of alpha activity on memory is controversial. The current study analyzed previous works in terms of randomized and blinded analyses, training paradigms, and participant characteristics to validate the efficacy of alpha NFT on memory in a healthy population.Objectives: A systematic meta-analysis of studies with randomized controlled trials was performed to explore the effect of alpha NFT on working memory (WM) and episodic memory (EM) in a healthy population.Methods: We searched PubMed, Embase, and Cochrane Library from January 1, 1999, to November 30, 2019. Previous studies were evaluated with the Cochrane risk of bias (RoB). A meta-analysis calculating absolute weighted standardized mean difference (SMD) using random-effects models was employed. Heterogeneity was estimated using I2 statistics. Funnel plots and Egger's test were performed to evaluate the quality of evidence.Results: Sixteen studies with 217 healthy participants in the control group and 210 participants in the alpha group met the eligibility criteria. Alpha NFT studies with WM measures presented little publication bias (P = 0.116), and 5 of 7 domains in the Cochrane RoB exhibited a low risk of bias. The overall effect size from 14 WM studies was 0.56 (95% CI 0.31–0.81, P < 0.0001; I2 = 28%). Six EM studies exhibited an effect size of 0.77 (95% CI 0.06–1.49, P = 0.03; I2 = 77%).Conclusion: Meta-analysis results suggest that alpha NFT seems to have a positive effect on the WM and EM of healthy participants. Future efforts should focus on the neurophysiological mechanisms of alpha NFT in memory.

Validation of eyes-closed resting alpha amplitude predicting neurofeedback learning of upregulation alpha activity

“…Possible reasons for the discrepancy between these two studies of the upregulation alpha NFT are different training sessions (12 vs. 20), trial amount of a session (6 vs. 12), and trial duration (6 min vs. 20 s). A meta-analysis study indicated that a long trial duration is good to increase alpha amplitude and duration during NFT 33 . The MRAA of the previous study ranged from 0.9 to 1.05 throughout 20 sessions 27 .…”

“…The present study carried out NFT to upregulate alpha activity because previous studies have demonstrated advantages of alpha NFT in memory enhancement 9 , 11 , 31 , 33 . We anticipated trainability and independence of alpha activity in the NFT process.…”

Neurofeedback and the Aging Brain: A Systematic Review of Training Protocols for Dementia and Mild Cognitive Impairment

“…Findings suggested that this protocol may be an effective option to improve working memory and episodic memory. Specifically, the authors found moderate effect size for both memory categories, whilst further analysis showed little risk for publication bias among these RCTs (Yeh et al, 2020). Efficacy in improving cognitive function has thus far mainly been demonstrated in young and healthy individuals.…”

“…Alternatively, protocols that were previously tested in healthy participants could be translated to patients. For instance, a recent meta-analysis (Yeh et al, 2020) evaluated RCTs of EEG neurofeedback training of the alpha frequency band in healthy individuals. Findings suggested that this protocol may be an effective option to improve working memory and episodic memory.…”

“…Another relevant aspect is the lack of control groups and conditions in many experimental designs. In this review, we only identified one RCT (Jirayucharoensak et al, 2019) and one controlled protocol (Hohenfeld et al, 2017(Hohenfeld et al, , 2020, which stands in stark contrast to the 16 RCTs that were recently reported in a meta-analysis of EEG protocols for memory improvement in healthy participants (Yeh et al, 2020). Another difference worth noticing is that most trials that were included in the meta-analysis by Yeh et al featured larger sample sizes per group, and several trials included multiple arms, enabling them to control for different non-specific effects (Sorger et al, 2019).…”