Section Brain Stimulation and Cognition, Department of Cognitive Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University, Maastricht, The Netherlands.
Maastricht Brain Imaging Centre (MBIC), Maastricht University, Maastricht, The Netherlands.
Eur J Neurosci. 2020 Jun;51(11):2299-2313. doi: 10.1111/ejn.14677. Epub 2020 Jan 29.
In recent years, the influence of alpha (7-13 Hz) phase on visual processing has received a lot of attention. Magneto-/encephalography (M/EEG) studies showed that alpha phase indexes visual excitability and task performance. Studies with transcranial alternating current stimulation (tACS) aim to modulate oscillations and causally impact task performance. Here, we applied right occipital tACS (O2 location) to assess the functional role of alpha phase in a series of experiments. We presented visual stimuli at different pre-determined, experimentally controlled, phases of the entraining tACS signal, hypothesizing that this should result in an oscillatory pattern of visual performance in specifically left hemifield detection tasks. In experiment 1, we applied 10 Hz tACS and used separate psychophysical staircases for six equidistant tACS-phase conditions, obtaining contrast thresholds for detection of visual gratings in left or right hemifield. In experiments 2 and 3, tACS was at EEG-based individual peak alpha frequency. In experiment 2, we measured detection rates for gratings with (pseudo-)fixed contrast. In experiment 3, participants detected brief luminance changes in a custom-built LED device, at eight equidistant alpha phases. In none of the experiments did the primary outcome measure over phase conditions consistently reflect a one-cycle sinusoid. However, post hoc analyses of reaction times (RT) suggested that tACS alpha phase did modulate RT for specifically left hemifield targets in both experiments 1 and 2 (not measured in experiment 3). This observation requires future confirmation, but is in line with the idea that alpha phase causally gates visual inputs through cortical excitability modulation.
近年来，α（7-13 Hz）相位对视觉处理的影响受到了广泛关注。脑磁图/脑电图（M/EEG）研究表明，α相位指数可反映视觉兴奋性和任务表现。经颅交流电刺激（tACS）的研究旨在调节振荡并对任务表现产生因果影响。在这里，我们应用右侧枕叶 tACS（O2 位置）在一系列实验中评估α相位的功能作用。我们在不同的预先确定的实验控制相位下呈现视觉刺激，假设这应该导致左半视野检测任务中的视觉表现呈现出振荡模式。在实验 1 中，我们应用 10 Hz tACS，并为六个等距 tACS 相位条件使用单独的心理物理阶梯，以获得左或右半视野中视觉光栅检测的对比阈值。在实验 2 和 3 中，tACS 基于 EEG 个体峰值α频率。在实验 2 中，我们测量了具有（伪）固定对比度的光栅的检测率。在实验 3 中，参与者在定制的 LED 设备中检测到八个等距α相位的短暂亮度变化。在没有一个实验中，主要结果测量都没有一致地反映出一个周期的正弦曲线。然而，对反应时间（RT）的事后分析表明，tACSα相位确实在实验 1 和 2 中调节了特定左半视野目标的 RT（实验 3 中未测量）。这一观察结果需要进一步确认，但与α相位通过皮层兴奋性调制对视觉输入进行因果门控的观点一致。
