Institute for Biomedical Imaging and Translational Research (CIBIT), University of Coimbra, Coimbra, Portugal.
Institute of Nuclear Sciences Applied to Health (ICNAS), University of Coimbra, Coimbra, Portugal.
Hum Brain Mapp. 2024 Aug 15;45(12):e26779. doi: 10.1002/hbm.26779.
Recently, there has been a resurgence in experimental and conceptual efforts to understand how brain rhythms can serve to organize visual information. Oscillations can provide temporal structure for neuronal processing and form a basis for integrating information across brain areas. Here, we use a bistable paradigm and a data-driven approach to test the hypothesis that oscillatory modulations associate with the integration or segregation of visual elements. Spectral signatures of perception of bound and unbound configurations of visual moving stimuli were studied using magnetoencephalography (MEG) in ambiguous and unambiguous conditions. Using a 2 × 2 design, we were able to isolate correlates from visual integration, either perceptual or stimulus-driven, from attentional and ambiguity-related activity. Two frequency bands were found to be modulated by visual integration: an alpha/beta frequency and a higher frequency gamma-band. Alpha/beta power was increased in several early visual cortical and dorsal visual areas during visual integration, while gamma-band power was surprisingly increased in the extrastriate visual cortex during segregation. This points to an integrative role for alpha/beta activity, likely from top-down signals maintaining a single visual representation. On the other hand, when more representations have to be processed in parallel gamma-band activity is increased, which is at odds with the notion that gamma oscillations are related to perceptual coherence. These modulations were confirmed in intracranial EEG recordings and partially originate from distinct brain areas. Our MEG and stereo-EEG data confirms predictions of binding mechanisms depending on low-frequency activity for long-range integration and for organizing visual processing while refuting a straightforward correlation between gamma-activity and perceptual binding. PRACTITIONER POINTS: Distinct neurophysiological signals underlie competing bistable percepts. Increased alpha/beta activity correlate with visual integration while gamma correlates with segmentation. Ambiguous percepts drive alpha/beta activity in the posterior cingulate cortex.
最近，人们重新开展了实验和概念研究，以了解脑节律如何组织视觉信息。振荡可以为神经元处理提供时间结构，并为跨脑区整合信息形成基础。在这里，我们使用双稳态范式和数据驱动方法来测试以下假设：振荡调制与视觉元素的整合或分离相关。我们使用脑磁图（MEG）在模糊和明确条件下研究了视觉运动刺激的绑定和未绑定配置的感知的频谱特征。使用 2×2 设计，我们能够从视觉整合、知觉或刺激驱动中分离出与注意力和模糊性相关的活动的相关性。发现两个频带受到视觉整合的调制：一个是阿尔法/贝塔频带，另一个是更高的伽马频带。在视觉整合过程中，几个早期视觉皮质和背侧视觉区域的阿尔法/贝塔功率增加，而在分离过程中，伽马频带功率出人意料地增加了。这表明阿尔法/贝塔活动具有整合作用，可能来自维持单一视觉表示的自上而下的信号。另一方面，当需要并行处理更多表示时，伽马频带活动增加，这与伽马振荡与知觉连贯性相关的观点不一致。这些调制在颅内 EEG 记录中得到了证实，并部分源自不同的大脑区域。我们的 MEG 和立体 EEG 数据证实了绑定机制的预测，这些机制取决于低频活动进行长程整合和组织视觉处理，同时反驳了伽马活动和知觉绑定之间存在直接关联的观点。
