Center for Consciousness Science; Department of Anesthesiology.
Center for Consciousness Science; Department of Anesthesiology.
Neuroimage. 2022 Apr 1;249:118891. doi: 10.1016/j.neuroimage.2022.118891. Epub 2022 Jan 8.
Recent neuroimaging studies have demonstrated that spontaneous brain activity exhibits rich spatiotemporal structure that can be characterized as the exploration of a repertoire of spatially distributed patterns that recur over time. The repertoire of brain states may reflect the capacity for consciousness, since general anesthetics suppress and psychedelic drugs enhance such dynamics. However, the modulation of brain activity repertoire across varying states of consciousness has not yet been studied in a systematic and unified framework. As a unique drug that has both psychedelic and anesthetic properties depending on the dose, ketamine offers an opportunity to examine brain reconfiguration dynamics along a continuum of consciousness. Here we investigated the dynamic organization of cortical activity during wakefulness and during altered states of consciousness induced by different doses of ketamine. Through k-means clustering analysis of the envelope data of source-localized electroencephalographic (EEG) signals, we identified a set of recurring states that represent frequency-specific spatial coactivation patterns. We quantified the effect of ketamine on individual brain states in terms of fractional occupancy and transition probabilities and found that ketamine anesthesia tends to shift the configuration toward brain states with low spatial variability. Furthermore, by assessing the temporal dynamics of the occurrence and transitions of brain states, we showed that subanesthetic ketamine is associated with a richer repertoire, while anesthetic ketamine induces dynamic changes in brain state organization, with the repertoire richness evolving from a reduced level to one comparable to that of normal wakefulness before recovery of consciousness. These results provide a novel description of ketamine's modulation of the dynamic configuration of cortical activity and advance understanding of the neurophysiological mechanism of ketamine in terms of the spatial, temporal, and spectral structures of underlying whole-brain dynamics.
最近的神经影像学研究表明，自发脑活动表现出丰富的时空结构，可以被描述为对随时间重复出现的、分布在空间上的模式组合的探索。脑状态的组合可能反映了意识的能力，因为全身麻醉会抑制这种动力学，而迷幻药物则会增强这种动力学。然而，在不同的意识状态下，脑活动组合的调制尚未在一个系统和统一的框架内进行研究。氯胺酮是一种独特的药物，其具有致幻和麻醉特性，取决于剂量，这为研究意识连续体中脑重构动力学提供了机会。在这里，我们研究了不同剂量氯胺酮诱导的清醒状态和意识改变状态下皮质活动的动态组织。通过对源定位脑电图 (EEG) 信号包络数据进行 k-均值聚类分析，我们确定了一组代表特定频率的空间协同激活模式的重复状态。我们根据分数占用率和转换概率量化了氯胺酮对个体脑状态的影响，发现氯胺酮麻醉倾向于将配置转移到具有低空间可变性的脑状态。此外，通过评估脑状态出现和转换的时间动态，我们表明亚麻醉剂量的氯胺酮与更丰富的组合相关，而麻醉剂量的氯胺酮会引起脑状态组织动态变化，组合丰富度从降低的水平演变为与正常清醒状态相当的水平，然后在意识恢复之前。这些结果提供了氯胺酮对皮质活动动态配置调制的新描述，并从空间、时间和潜在全脑动力学的光谱结构方面，推进了对氯胺酮神经生理学机制的理解。
