Department of Brain and Cognitive Engineering, Korea University, Seoul, 02841, Korea.
Department of Anesthesiology, University of Wisconsin, Madison, Wisconsin, 53792, USA.
Sci Rep. 2017 Dec 1;7(1):16791. doi: 10.1038/s41598-017-15082-5.
Reliable electroencephalography (EEG) signatures of transitions between consciousness and unconsciousness under anaesthesia have not yet been identified. Herein we examined network changes using graph theoretical analysis of high-density EEG during patient-titrated propofol-induced sedation. Responsiveness was used as a surrogate for consciousness. We divided the data into five states: baseline, transition into unresponsiveness, unresponsiveness, transition into responsiveness, and recovery. Power spectral analysis showed that delta power increased from responsiveness to unresponsiveness. In unresponsiveness, delta waves propagated from frontal to parietal regions as a traveling wave. Local increases in delta connectivity were evident in parietal but not frontal regions. Graph theory analysis showed that increased local efficiency could differentiate the levels of responsiveness. Interestingly, during transitions of responsive states, increased beta connectivity was noted relative to consciousness and unconsciousness, again with increased local efficiency. Abrupt network changes are evident in the transitions in responsiveness, with increased beta band power/connectivity marking transitions between responsive states, while the delta power/connectivity changes were consistent with the fading of consciousness using its surrogate responsiveness. These results provide novel insights into the neural correlates of these behavioural transitions and EEG signatures for monitoring the levels of consciousness under sedation.
可靠的麻醉状态下意识与无意识之间转变的脑电图（EEG）特征尚未确定。在此，我们使用高分辨率 EEG 的图论分析检查了患者滴定异丙酚诱导镇静期间的网络变化。反应性作为意识的替代物。我们将数据分为五个状态：基线、进入无反应状态、无反应状态、进入反应状态和恢复。功率谱分析显示，从反应性到无反应性，delta 功率增加。在无反应性中，delta 波作为行波从前额传播到顶叶区域。delta 连通性的局部增加在顶叶区域而不是在前额叶区域明显。图论分析表明，局部效率的增加可以区分反应性水平。有趣的是，在反应性状态的转变过程中，与意识和无意识相比，beta 连通性增加，同样，局部效率也增加。在反应性的转变过程中，网络变化明显，beta 频带功率/连通性的增加标志着反应性状态之间的转变，而 delta 功率/连通性的变化与使用替代反应性的意识消失一致。这些结果为这些行为转变的神经相关性以及镇静状态下意识监测的 EEG 特征提供了新的见解。
