Neural oscillations in the alpha band (8–12 Hz) have been proposed as a key mechanism for the temporal resolution of visual perception. Higher alpha frequencies have been related to improved segregation of visual events over time, whereas lower alpha frequencies have been related to improved temporal integration. Similarly, also the phase of ongoing alpha has been shown to correlate with temporal integration/segregation. To test a causal relationship between alpha oscillations and perception, we here employed multi-channel transcranial alternating current stimulation (mc-tACS) over the right parietal cortex, whereas participants performed a visual temporal integration/segregation task that used identical stimuli with different instructions. Before and after mc-tACS we recorded the resting-state electroencephalogram (EEG) to extract the individual alpha frequency (IAF) and delivered electrical stimulation at slightly slower and faster frequencies (IAF±2 Hz). We hypothesized that this would not only drive endogenous alpha rhythms, but also affect temporal integration and segregation in an opposite way. However, the mc-tACS protocol used here did not consistently increase or decrease the IAF after the stimulation and did not affect temporal integration/segregation accuracy as expected. Although we found some preliminary evidence for an influence of tACS phase on temporal integration accuracy, the ongoing phase of mc-tACS oscillations did not reliably modulate temporal integration/segregation accuracy in a sinusoidal way as would have been predicted by an effective entrainment of brain oscillations. These findings may guide future studies using different stimulation montages for investigating the role of cortical alpha oscillations for human vision.

中文翻译：

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测试 tACS 对顶叶皮层在调节视觉感知中内源性 α 节律和时间整合窗口中的作用

阿尔法波段（8-12 Hz）的神经振荡已被提议作为视觉感知时间分辨率的关键机制。较高的阿尔法频率与随着时间的推移改善视觉事件的分离有关，而较低的阿尔法频率与改善的时间整合有关。同样，正在进行的阿尔法阶段也已被证明与时间整合/分离相关。为了测试 alpha 振荡和感知之间的因果关系，我们在这里在右侧顶叶皮层采用多通道经颅交流电刺激 (mc-tACS)，而参与者执行视觉时间整合/分离任务，该任务使用具有不同指令的相同刺激。在 mc-tACS 之前和之后，我们记录了静息状态脑电图 (EEG) 以提取个体 α 频率 (IAF)，并以稍慢和稍快的频率 (IAF±2 Hz) 进行电刺激。我们假设这不仅会驱动内源性阿尔法节律，还会以相反的方式影响时间整合和分离。然而，这里使用的 mc-tACS 协议在刺激后并没有持续增加或减少 IAF，也没有像预期的那样影响时间整合/分离的准确性。尽管我们发现了一些初步证据表明 tACS 相位对时间积分精度的影响，mc-tACS 振荡的持续阶段并没有可靠地以正弦方式调节时间积分/分离精度，正如大脑振荡的有效夹带所预测的那样。这些发现可能会指导未来的研究，使用不同的刺激蒙太奇来研究皮质 α 振荡对人类视觉的作用。