Department of Neuroscience, Bilkent University, Cankaya, Ankara 06800, Türkiye.
Aysel Sabuncu Brain Research Center, Bilkent University, Cankaya, Ankara 06800, Türkiye.
Cereb Cortex. 2024 Sep 3;34(9). doi: 10.1093/cercor/bhae380.
The phase synchronization of brain oscillations plays an important role in visual processing, perceptual awareness, and performance. Yet, the cortical mechanisms underlying modulatory effects of post-stimulus phase coherence and frequency-specific oscillations associated with different aspects of vision are still subject to debate. In this study, we aimed to identify the post-stimulus phase coherence of cortical oscillations associated with perceived visibility and contour discrimination. We analyzed electroencephalogram data from two masking experiments where target visibility was manipulated by the contrast ratio or polarity of the mask under various onset timing conditions (stimulus onset asynchronies, SOAs). The behavioral results indicated an SOA-dependent suppression of target visibility due to masking. The time-frequency analyses revealed significant modulations of phase coherence over occipital and parieto-occipital regions. We particularly identified modulations of phase coherence in the (i) 2-5 Hz frequency range, which may reflect feedforward-mediated contour detection and sustained visibility; and (ii) 10-25 Hz frequency range, which may be associated with suppressed visibility through inhibitory interactions between and within synchronized neural pathways. Taken together, our findings provide evidence that oscillatory phase alignments, not only in the pre-stimulus but also in the post-stimulus window, play a crucial role in shaping perceived visibility and dynamic vision.
脑振荡的相位同步在视觉处理、知觉意识和表现中起着重要作用。然而，与视觉的不同方面相关的刺激后相位相干性和频率特异性振荡的调节效应的皮质机制仍存在争议。在这项研究中，我们旨在确定与知觉可见度和轮廓辨别相关的皮质振荡的刺激后相位相干性。我们分析了来自两个掩蔽实验的脑电图数据，其中目标的可见度通过掩蔽下的对比度比或极性在各种起始时间条件（刺激起始异步，SOA）下进行操纵。行为结果表明，由于掩蔽，目标可见度存在 SOA 依赖性抑制。时频分析显示，在枕部和枕顶区域的相位相干性有显著的调制。我们特别确定了相位相干性在（i）2-5 Hz 频率范围内的调制，这可能反映了前馈介导的轮廓检测和持续的可见度；以及（ii）10-25 Hz 频率范围，这可能与通过同步神经通路之间和内部的抑制性相互作用而抑制可见度有关。总之，我们的发现提供了证据表明，振荡相位对准不仅在刺激前，而且在刺激后窗口中，对塑造知觉可见度和动态视觉起着关键作用。
