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.
Highlights
Electroencephalogram (EEG) consists of various brain activities, such as alpha, theta, or beta rhythm
The results showed a significant overall effect with an standardized mean difference (SMD) of 0.56, suggesting that Neurofeedback training (NFT) of alpha activity would improve working memory (WM) performance compared with the control group
The results showed a significant overall effect with an SMD of 0.77, suggesting that NFT of alpha activity could improve episodic memory (EM) performance compared with the control group
Summary
Electroencephalogram (EEG) consists of various brain activities, such as alpha, theta, or beta rhythm. Alpha activities of the frontal and parietal cortices have a highly positive correlation with intelligence in healthy adults, memory (Klimesch, 1999; Doppelmayr et al, 2002). Event-related synchronization or desynchronization within 8–12 Hz exhibits a high correlation with accurate motor performance (Ros et al, 2014). These findings suggest that alpha activity plays a specific role in cognitive modulation (Palva and Palva, 2007). 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
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