Cross-frequency phase-amplitude coupling (PAC) of cortical oscillations is observed within and across cortical regions during higher-order cognitive processes. Particularly, the PAC of alpha and gamma waves in the occipital cortex is closely associated with visual perception. In theory, gamma oscillation is a neuronal representation of visual stimuli, which drives the duty cycle of visual perception together with alpha oscillation. Therefore, it is believed that the timing of entrainment in alpha-gamma PAC may play a critical role in the performance of visual perception. We hypothesized that transcranial alternating current stimulation (tACS) with gamma waves entrained at the troughs of alpha waves would enhance the dynamic visual acuity (DVA). We attempted to modulate the performance of DVA by using tACS. The waveforms of the tACS were tailored to target PAC over the occipital cortex. The waveforms contained gamma (80 Hz) waves oscillating at either the peaks or troughs of alpha (10 Hz) waves. Participants performed computerized DVA task before, immediately after, and 10 min after each stimulation sessions. EEG and EOG were recorded during the DVA task to assess inter-trial phase coherence (ITPC), the alpha-gamma PAC at occipital site and the eye movements. tACS with gamma waves entrained at alpha troughs effectively enhanced DVA, while the tACS with gamma waves entrained at alpha peaks did not affect DVA performance. Importantly, analyses of EEG and EOG showed that the enhancement of DVA performance originated solely from the neuromodulatory effects, and was not related to the modulation of saccadic eye movements. Consequently, DVA, one of the higher-order cognitive abilities, was successfully modulated using tACS with a tailored waveform. Our experimental results demonstrated that DVA performances were enhanced when tACS with gamma bursts entrained on alpha wave troughs were applied over the occipital cortex. Our findings suggest that using tACS with tailored waveforms, modulation of complex neuronal features could effectively enhance higher-order cognitive abilities such as DVA, which has never been modulated with conventional noninvasive brain stimulation methods.

中文翻译：

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使用经颅交流电刺激和α波谷夹带的伽马爆发增强动态视力

在高阶认知过程中，可以在皮层区域内和皮层区域之间观察到皮层振荡的跨频相位幅度耦合（PAC）。特别是枕叶皮质中的α波和γ波PAC与视觉感知密切相关。理论上，伽马振荡是视觉刺激的神经元表征，它与阿尔法振荡一起驱动视觉感知的占空比。因此，人们相信，α-γ PAC 的夹带时间可能对视觉感知的表现起着关键作用。我们假设在α波波谷夹带伽马波的经颅交流电刺激（tACS）会增强动态视力（DVA）。我们尝试使用 tACS 来调节 DVA 的性能。tACS 的波形是针对枕叶皮质上的 PAC 进行定制的。波形包含在 α (10 Hz) 波的波峰或波谷处振荡的伽马 (80 Hz) 波。参与者在每次刺激课程之前、之后立即和之后 10 分钟执行计算机化的 DVA 任务。在 DVA 任务期间记录 EEG 和 EOG，以评估试验间相干性 (ITPC)、枕骨部位的 alpha-gamma PAC 和眼球运动。α 波谷夹带伽马波的 tACS 有效增强了 DVA，而 α 峰夹带伽马波的 tACS 并不影响 DVA 性能。重要的是，脑电图和眼电图分析表明，DVA 表现的增强完全源于神经调节作用，与眼跳运动的调节无关。因此，使用具有定制波形的 tACS 成功调节了 DVA（高阶认知能力之一）。我们的实验结果表明，当在枕叶皮层上应用 α 波波谷夹带伽马爆发的 tACS 时，DVA 性能得到增强。我们的研究结果表明，使用具有定制波形的 tACS 来调节复杂的神经元特征可以有效增强高阶认知能力，例如 DVA，而传统的非侵入性脑刺激方法从未对其进行过调节。