Alpha-frequency feedback to early visual cortex orchestrates coherent naturalistic vision

During naturalistic vision, the brain generates coherent percepts by integrating sensory inputs scattered across the visual field. Here, we asked whether this integration process is mediated by rhythmic cortical feedback. In EEG and fMRI experiments, we experimentally manipulated integrative processing by changing the spatiotemporal coherence of naturalistic videos presented across visual hemifields. Our EEG data revealed that information about incoherent videos is coded in feedforward-related gamma activity while information about coherent videos is coded in feedback-related alpha activity, indicating that integration is indeed mediated by rhythmic activity. Our fMRI data identified scene-selective cortex and hMT as likely sources of this feedback. Analytically combining our EEG and fMRI data further revealed that feedback-related representations in the alpha band shape the earliest stages of visual processing in cortex. Together, our findings indicate that the construction of coherent visual experiences relies on cortical feedback rhythms that fully traverse the visual hierarchy.在自然视觉过程中，大脑通过整合散布于整个视野的感觉输入，构建出连贯的视觉知觉。本研究旨在探究这一整合过程是否由节律性皮层反馈所介导。在脑电图（EEG）与功能磁共振成像（fMRI）实验中，我们通过改变跨视觉半视野呈现的自然视频的时空连贯性，对整合加工过程进行实验操控。脑电图数据显示，非连贯视频的信息编码于与前馈通路相关的伽马（gamma）频段活动中，而连贯视频的信息则编码于与反馈通路相关的阿尔法（alpha）频段活动中，这表明整合过程确实由节律性活动所介导。功能磁共振成像数据进一步确定，场景选择性皮层与hMT为该反馈通路的潜在源头。对脑电图与功能磁共振成像数据进行联合分析后还发现，阿尔法频段内与反馈相关的神经表征塑造着皮层视觉加工的早期阶段。综上，本研究结果表明，连贯视觉体验的构建依赖于可完全遍历视觉层级的皮层反馈节律。