Department of Psychology, Ludwig-Maximilians-Universität München, Leopoldstr. 13, Munich, 80802, Germany.
Graduate School of Systemic Neurosciences, Ludwig-Maximilians-Universität München, Großhaderner Str. 2, Planegg-Martinsried, 82152, Germany.
Eur J Neurosci. 2022 Jan;55(2):405-425. doi: 10.1111/ejn.15563. Epub 2022 Jan 11.
Oscillatory theta activity in a fronto-parietal network has been associated with working memory (WM) processes and may be directly related to WM performance. In their seminal study, Polanía et al. (2012) (de-)coupled a fronto-parietal theta-network by applying transcranial alternating current stimulation (tACS), and showed that anti-phase tACS led to slower and in-phase tACS to faster response times in a verbal WM task compared to placebo stimulation. In the literature, this 'synchronization-desynchronization' effect has only been partly replicated, and electric field modelling suggests that it might not be the fronto-parietal network that is primarily stimulated during in-phase tACS with a shared return electrode. This provides one possible reason for inconsistency in the literature. In this study, we aimed to reproduce the findings reported by Polanía et al. (2012). We also aimed to investigate whether in-phase theta tACS with multiple close-by return electrodes for focal stimulation of the frontal and the parietal cortex will have at least as much of a facilitatory effect as the in-phase stimulation as indicated by Polania et al. (2012). In a single-trial distributional analysis, we explored whether mean, variation and right-skewness of the response time distribution are affected. Against our hypothesis, we found no 'synchronization-desynchronization' effect by fronto-parietal theta tACS on response times using the same delayed letter discrimination task and stimulation parameters in two experiments, both between-subjects and within-subjects. However, we could show that in a more demanding 3-back task, fronto-parietal in-phase and in-phase focal theta tACS substantially improved task performance compared to placebo stimulation.
额顶网络的振荡θ活动与工作记忆（WM）过程有关，并且可能与 WM 表现直接相关。在他们的开创性研究中，Polanía 等人（2012 年）通过应用经颅交流电刺激（tACS）去耦额顶θ网络，并且表明与安慰剂刺激相比，反相 tACS 导致言语 WM 任务的反应时间变慢，同相 tACS 导致反应时间变快。在文献中，这种“同步-去同步”效应仅部分得到复制，并且电场建模表明，在同相 tACS 期间，具有共享返回电极的额顶网络可能不是主要被刺激的网络。这为文献中的不一致性提供了一个可能的原因。在这项研究中，我们旨在复制 Polanía 等人（2012 年）报告的发现。我们还旨在研究使用多个靠近的返回电极进行额顶皮质的焦点刺激的同相θ tACS 是否会像 Polania 等人（2012 年）所表明的那样，对反应时间产生至少与同相刺激一样的促进作用。在单次试验分布分析中，我们探索了反应时间分布的平均值、变异性和右偏度是否受到影响。与我们的假设相反，我们在两个实验中都没有发现额顶θ tACS 对反应时间的“同步-去同步”效应，这两个实验都是在两个实验中进行的，一个是在两个实验中进行的，另一个是在两个实验中进行的。但是，我们可以证明，在更具挑战性的 3 -back 任务中，额顶同相和同相焦点θ tACS 与安慰剂刺激相比，显著提高了任务表现。
