Cerco, CNRS Université de Toulouse, Toulouse, France.
Artificial and Natural Intelligence Toulouse Institute, Toulouse, France.
Elife. 2023 Mar 6;12:e85035. doi: 10.7554/eLife.85035.
Previous research has associated alpha-band [8-12 Hz] oscillations with inhibitory functions: for instance, several studies showed that visual attention increases alpha-band power in the hemisphere ipsilateral to the attended location. However, other studies demonstrated that alpha oscillations positively correlate with visual perception, hinting at different processes underlying their dynamics. Here, using an approach based on traveling waves, we demonstrate that there are two functionally distinct alpha-band oscillations propagating in different directions. We analyzed EEG recordings from three datasets of human participants performing a covert visual attention task (one new dataset with = 16, two previously published datasets with = 16 and = 31). Participants were instructed to detect a brief target by covertly attending to the screen's left or right side. Our analysis reveals two distinct processes: allocating attention to one hemifield increases top-down alpha-band waves propagating from frontal to occipital regions ipsilateral to the attended location, both with and without visual stimulation. These top-down oscillatory waves correlate positively with alpha-band power in frontal and occipital regions. Yet, different alpha-band waves propagate from occipital to frontal regions and contralateral to the attended location. Crucially, these forward waves were present only during visual stimulation, suggesting a separate mechanism related to visual processing. Together, these results reveal two distinct processes reflected by different propagation directions, demonstrating the importance of considering oscillations as traveling waves when characterizing their functional role.
先前的研究将 alpha 波段（8-12 Hz）的振荡与抑制功能联系起来：例如，有几项研究表明，视觉注意力会增加与被注视位置同侧半球的 alpha 波段功率。然而，其他研究表明，alpha 振荡与视觉感知呈正相关，暗示了它们动态背后的不同过程。在这里，我们使用基于行波的方法，证明了存在两种在不同方向上传播的功能上不同的 alpha 波段振荡。我们分析了三个人类参与者执行隐蔽视觉注意任务的 EEG 记录数据集（一个新数据集，n = 16，两个先前发表的数据集，n = 16 和 n = 31）。参与者被指示通过隐蔽地注视屏幕的左侧或右侧来检测短暂的目标。我们的分析揭示了两个不同的过程：将注意力分配到一个半视野会增加从额部到与被注视位置同侧的枕部的自上而下的 alpha 波段波的传播，无论是在有还是没有视觉刺激的情况下。这些自上而下的振荡波与额部和枕部的 alpha 波段功率呈正相关。然而，不同的 alpha 波段波从枕部向额部和与被注视位置相反的方向传播。至关重要的是，这些前向波仅在视觉刺激期间存在，表明与视觉处理相关的另一种机制。总之，这些结果揭示了两种不同的过程，反映在不同的传播方向上，表明在描述其功能作用时，将振荡视为行波的重要性。
