Department for Human Neuroscience, Institute for Medical Research, University of Belgrade, Belgrade, Serbia.
The School of Computing, Union University, Belgrade, Serbia.
Sci Rep. 2021 Feb 4;11(1):3013. doi: 10.1038/s41598-021-82577-7.
Associative memory (AM) reflects the ability to remember and retrieve multiple pieces of information bound together thus enabling complex episodic experiences. Despite growing interest in the use of transcranial direct current stimulation (tDCS) for the modulation of AM, there are inconsistent evidence regarding its benefits. An alternative to standard constant tDCS could be the application of frequency-modulated tDCS protocols, that mimic natural function-relevant brain rhythms. Here, we show the effects of anodal tDCS oscillating in theta rhythm (5 Hz; 1.5 ± 0.1 mA) versus constant anodal tDCS and sham over left posterior parietal cortex on cued recall of face-word associations. In a crossover design, each participant completed AM assessment immediately following 20-min theta-oscillatory, constant, and sham tDCS, as well as 1 and 5 days after. Theta oscillatory tDCS increased initial AM performance in comparison to sham, and so did constant tDCS. On the group level, no differences between oscillatory and constant tDCS were observed, but individual-level analysis revealed that some participants responded to theta-oscillatory but not to constant tDCS, and vice versa, which could be attributed to their different physiological modes of action. This study shows the potential of oscillatory tDCS protocols for memory enhancement to produce strong and reliable memory-modulating effects which deserve to be investigated further.
联想记忆（AM）反映了记住和检索多个相关信息的能力，从而使复杂的情景体验成为可能。尽管人们对经颅直流电刺激（tDCS）在调节 AM 方面的应用越来越感兴趣，但关于其益处的证据并不一致。标准恒稳 tDCS 的替代方法可能是应用频率调制 tDCS 方案，模拟与自然功能相关的脑节律。在这里，我们展示了在左后顶叶皮层上施加 5Hz（1.5±0.1mA）的阳极 tDCS 与恒稳阳极 tDCS 和假刺激相比，对人脸-词汇联想的线索回忆的影响。在交叉设计中，每位参与者在接受 20 分钟的 theta 振荡、恒稳和假刺激以及 1 天和 5 天后，立即完成 AM 评估。与假刺激相比，theta 振荡 tDCS 增加了初始 AM 表现，恒稳 tDCS 也是如此。在组水平上，没有观察到 theta 振荡和恒稳 tDCS 之间的差异，但个体水平分析表明，一些参与者对 theta 振荡有反应，但对恒稳 tDCS 没有反应，反之亦然，这可能归因于它们不同的生理作用模式。这项研究表明，振荡 tDCS 方案具有增强记忆的潜力，可以产生强烈而可靠的记忆调节效应，值得进一步研究。
