意识障碍是由严重脑损伤引起的意识受损状态。先前的静息状态功能磁共振成像研究已通过使用图论分析报告了意识障碍患者在不同拓扑尺度下的异常脑网络特性。然而,目前尚不清楚区域间定向传播活动如何影响意识障碍患者功能性脑网络的拓扑组织。为了揭示意识障碍患者拓扑组织的改变,我们通过结合功能连通性分析和时延估计构建了全脑定向功能网络。然后,我们在三个拓扑尺度上基于有向功能脑网络进行了图论分析,从节点尺度来看,静息态网络规模达到全球规模。最后,典型相关分析用于确定意识障碍患者拓扑特性改变与临床评分之间的相关性.在节点尺度上,我们观察到意识障碍患者的前外侧程度降低和程度升高。在静息态网络规模,意识障碍患者在默认模式网络内以及默认模式网络与其他静息状态网络之间显示出重组的基序模式.在全球范围内,我们发现意识障碍患者的整体聚集系数低于对照组.典型相关分析结果表明,意识障碍患者的异常程度和基序破坏与临床评分显著相关。我们的发现表明,意识障碍可以通过整个大脑在多个拓扑尺度上的异常定向连接模式来揭示,被破坏的定向连接模式可以作为临床生物标志物来评估意识障碍患者的功能障碍。
Disorders of consciousness are impaired states of consciousness caused by severe brain injuries. Previous resting-state functional magnetic resonance imaging studies have reported abnormal brain network properties at different topological scales in patients with disorders of consciousness by using graph theoretical analysis. However, it is still unclear how inter-regional directed propagation activities affect the topological organization of functional brain networks in patients with disorders of consciousness. To reveal the altered topological organization in patients with disorders of consciousness, we constructed whole-brain directed functional networks by combining functional connectivity analysis and time delay estimation. Then we performed graph theoretical analysis based on the directed functional brain networks at three topological scales, from the nodal scale, the resting-state network scale to the global scale. Finally, the canonical correlation analysis was used to determine the correlations between altered topological properties and clinical scores in patients with disorders of consciousness. At the nodal scale, we observed decreased in-
degree and increased out-
degree in the precuneus in patients with disorders of consciousness. At the resting-state network scale, the patients with disorders of consciousness showed reorganized motif patterns within the default mode network and between the default mode network and other resting-state networks. At the global scale, we found a lower global clustering coefficient in the patients with disorders of consciousness than in the controls. The results of the canonical correlation analysis showed that the abnormal
degree and the disrupted motif were significantly correlated with the clinical scores of the patients with disorders of consciousness. Our findings showed that consciousness impairment can be revealed by abnormal directed connection patterns at multiple topological scales in the whole brain, and the disrupted directed connection patterns may serve as clinical biomarkers to assess the dysfunction of patients with disorders of consciousness.