Oscillating transcranial direct current stimulation (osc-tDCS) modulates the spontaneous brain activity in a frequency-specific manner. Most studies evaluated cortical effects of osc-tDCS through spectral measures, without differentiating components associated with rhythmic and non-rhythmic activity. Since osc-tDCS mainly affects brain oscillatory activity, our aim was to investigate on the specific changes of EEG oscillations following a frontal osc-tDCS at 0.8 and at 5 Hz. 20 healthy subjects (26.8 ± 2.5 years) participated in one of two experiments (Exp.1= 0.8-Hz tDCS, n= 10; Exp.2= 5-Hz tDCS, n= 10), consisting of 3 within-subject sessions: two active conditions with different stimulation polarity (anodal osctDCS, cathodal osc-tDCS), and a control condition (sham). EEG oscillatory components (28 cortical derivations) at the stimulation frequency were measured by the Better OSCillation detection method (BOSC). Variations between before and after the osc-tDCS were compared between conditions as a function of polarity (anodal vs. cathodal vs. sham) and frequency (0.8 vs. 5 Hz) of stimulation. The main finding is a significant local increase of 0.81-Hz slow oscillations (F(1,18)=19.97; p=0.0004) and 5.3-Hz theta oscillations (F(1,18)=26.93; p= 0.0001) after 5 Hz compared to 0.8-Hz tDCS. Our study shows larger frequency-specific and cross-frequency effects of 5-Hz compared to 0.8-Hz stimulation, not revealed by conventional FFT analyses. This finding is consistent with a more effective induction of EEG synchronization during wakefulness by means of a stimulation in the theta range, and it suggests to combine measurement of EEG power and EEG oscillations in future studies involving transcranial stimulations.

中文翻译：

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振荡tDCS对EEG振荡的频率依赖性影响：采用更好的OSCillation检测方法（BOSC）的研究。

振荡式经颅直流电刺激（osc-tDCS）以特定于频率的方式调节自发性大脑活动。大多数研究通过频谱测量评估了osc-tDCS的皮层效应，而没有区分与节律性和非节律性活动相关的成分。由于osc-tDCS主要影响大脑的振荡活动，因此我们的目的是研究额叶osc-tDCS在0.8 Hz和5 Hz后脑电图振荡的具体变化。20名健康受试者（26.8±2.5岁）参加了两个实验之一（实验1 = 0.8-Hz tDCS，n = 10;实验2 = 5-Hz tDCS，n = 10），包括3个受试者内实验：两个具有不同刺激极性的活动条件（阳极osctDCS，阴极osc-tDCS）和控制条件（假）。通过更好的OSCillation检测方法（BOSC）测量刺激频率下的EEG振荡成分（28个皮质衍生）。比较了在osc-tDCS之前和之后的条件之间的变化，这些条件是刺激的极性（阳极vs.阴极vs.假）和频率（0.8 vs. 5 Hz）的函数。主要发现是5后第0.81 Hz缓慢振荡（F（1,18）= 19.97; p = 0.0004）和5.3 Hz theta振荡显着局部增加（F（1,18）= 26.93; p = 0.0001） Hz与0.8-Hz tDCS的比较。我们的研究表明，与0.8 Hz刺激相比，5 Hz的特定频率和交叉频率影响更大，传统的FFT分析并未揭示这一点。这一发现与在theta范围内进行刺激时在清醒过程中更有效地诱发EEG同步一致，