Department of Psychology, Kingston University, Penrhyn Road, Kingston Upon Thames, KT1 2EE, United Kingdom.
Departamento de Psicología Básica, Universidad Autónoma de Madrid, 28049 Cantoblanco, Madrid, Spain.
Brain Stimul. 2019 Mar-Apr;12(2):231-241. doi: 10.1016/j.brs.2018.11.008. Epub 2018 Nov 17.
In the past decade, several studies have examined the effects of transcranial direct current stimulation (tDCS) on long-term episodic memory formation and retrieval. These studies yielded conflicting results, likely due to differences in stimulation parameters, experimental design and outcome measures.
In this work we aimed to assess the robustness of tDCS effects on long-term episodic memory using a meta-analytical approach.
We conducted four meta-analyses to analyse the effects of anodal and cathodal tDCS on memory accuracy and response times. We also used a moderator analysis to examine whether the size of tDCS effects varied as a function of specific stimulation parameters and experimental conditions.
Although all selected studies reported a significant effect of tDCS in at least one condition in the published paper, the results of the four meta-analyses showed only statistically non-significant close-to-zero effects. A moderator analysis suggested that for anodal tDCS, the duration of the stimulation and the task used to probe memory moderated the effectiveness of tDCS. For cathodal tDCS, site of stimulation was a significant moderator, although this result was based on only a few observations.
To warrant theoretical advancement and practical implications, more rigorous research is needed to fully understand whether tDCS reliably modulates episodic memory, and the specific circumstances under which this modulation does, and does not, occur.
在过去的十年中，已有多项研究探讨了经颅直流电刺激（tDCS）对长期情景记忆形成和提取的影响。这些研究结果相互矛盾，可能是由于刺激参数、实验设计和结果测量的差异所致。
本研究旨在采用元分析方法评估 tDCS 对长期情景记忆的影响的稳健性。
我们进行了四项元分析，以分析阳极和阴极 tDCS 对记忆准确性和反应时间的影响。我们还使用了一个调节分析来检验 tDCS 效果的大小是否因特定的刺激参数和实验条件而有所变化。
尽管所有选定的研究在发表的论文中至少有一个条件报告了 tDCS 的显著效果，但四项元分析的结果仅显示出统计学上无显著接近零的效应。调节分析表明，对于阳极 tDCS，刺激的持续时间和用于探测记忆的任务调节了 tDCS 的有效性。对于阴极 tDCS，刺激部位是一个显著的调节因素，尽管这一结果仅基于少数观察结果。
为了推进理论发展和实际应用，需要进行更严格的研究，以充分了解 tDCS 是否可靠地调节情景记忆，以及在何种情况下会发生这种调节，以及在何种情况下不会发生这种调节。
