Perceptual Networks Group, Department of Psychology, University of Fribourg, Fribourg, Switzerland.
Brain and Language Lab, Department of Clinical Neuroscience, University of Geneva, Geneva, Switzerland.
Hum Brain Mapp. 2018 Oct;39(10):3854-3870. doi: 10.1002/hbm.24216. Epub 2018 May 24.
Visual selective attention operates through top-down mechanisms of signal enhancement and suppression, mediated by α-band oscillations. The effects of such top-down signals on local processing in primary visual cortex (V1) remain poorly understood. In this work, we characterize the interplay between large-scale interactions and local activity changes in V1 that orchestrates selective attention, using Granger-causality and phase-amplitude coupling (PAC) analysis of EEG source signals. The task required participants to either attend to or ignore oriented gratings. Results from time-varying, directed connectivity analysis revealed frequency-specific effects of attentional selection: bottom-up γ-band influences from visual areas increased rapidly in response to attended stimuli while distributed top-down α-band influences originated from parietal cortex in response to ignored stimuli. Importantly, the results revealed a critical interplay between top-down parietal signals and α-γ PAC in visual areas. Parietal α-band influences disrupted the α-γ coupling in visual cortex, which in turn reduced the amount of γ-band outflow from visual areas. Our results are a first demonstration of how directed interactions affect cross-frequency coupling in downstream areas depending on task demands. These findings suggest that parietal cortex realizes selective attention by disrupting cross-frequency coupling at target regions, which prevents them from propagating task-irrelevant information.
视觉选择性注意通过信号增强和抑制的自上而下机制进行操作，由α 波段振荡介导。这种自上而下的信号对初级视觉皮层 (V1) 中局部处理的影响仍知之甚少。在这项工作中，我们使用 EEG 源信号的格兰杰因果关系和相位-振幅耦合 (PAC) 分析来描述 V1 中协调选择性注意的大规模相互作用和局部活动变化之间的相互作用。任务要求参与者注意或忽略定向光栅。时变有向连接分析的结果揭示了注意力选择的频率特异性效应：来自视觉区域的自上而下的 γ 波段影响迅速增加以响应被注意的刺激，而来自顶叶皮层的分布式自上而下的 α 波段影响则响应被忽略的刺激而出现。重要的是，结果揭示了顶叶信号与视觉区域中 α-γPAC 之间的关键相互作用。顶叶 α 波段的影响破坏了视觉皮层中的 α-γ 耦合，从而减少了视觉区域中 γ 波段输出的数量。我们的研究结果首次证明了有向相互作用如何根据任务需求影响下游区域的跨频耦合。这些发现表明，顶叶皮层通过破坏目标区域的跨频耦合来实现选择性注意，从而防止它们传播与任务无关的信息。
