Decoupled temporal variability and signal synchronization of spontaneous brain activity in loss of consciousness: An fMRI study in anesthesia.

Abstract

Two aspects of the low frequency fluctuations of spontaneous brain activity have been proposed which reflect the complex and dynamic features of resting-state activity, namely temporal variability and signal synchronization. The relationship between them, especially its role in consciousness, nevertheless remains unclear. Our study examined the temporal variability and signal synchronization of spontaneous brain activity, as well as their relationship during loss of consciousness. We applied an intra-subject design of resting-state functional magnetic resonance imaging (rs-fMRI) in two conditions: during wakefulness, and under anesthesia with clinical unconsciousness. In addition, an independent group of patients with disorders of consciousness (DOC) was included in order to test the reliability of our findings. We observed a global reduction in the temporal variability, local and distant brain signal synchronization for subjects during anesthesia. Importantly, we found a link between temporal variability and both local and distant signal synchronizations during wakefulness: the higher the degree of temporal variability, the higher its intra-regional homogeneity and inter-regional functional connectivity. In contrast, this link was broken down under anesthesia, implying a decoupling between temporal variability and signal synchronization; this decoupling was reproduced in patients with DOC. Our results suggest that there exist some as yet unclear physiological mechanisms of consciousness which "couple" the two mathematically independent measures, temporal variability and signal synchronization of spontaneous brain activity. Our findings not only extend our current knowledge of the neural correlates of anesthetic-induced unconsciousness, but have implications for both computational neural modeling and clinical practice, such as in the diagnosis of loss of consciousness in patients with DOC.

• Authors: Zirui Huang, Jun Zhang, Jinsong Wu, Pengmin Qin, Xuehai Wu, Zhiyao Wang, Rui Dai, Yuan Li, Weimin Liang, Ying Mao, Zhong Yang, Jianfeng Zhang, Annemarie Wolff, Georg Northoff
• Journal: NeuroImage (Neuroimage) Vol. 124 Issue Pt A Pg. 693-703 (Jan 01 2016) ISSN: 1095-9572 [Electronic] United States
• PMID: 26343319 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2015 Elsevier Inc. All rights reserved.

Topics

• Adult
• Algorithms
• Anesthesia
• Brain (physiopathology)
• Brain Mapping
• Consciousness Disorders (diagnosis, pathology)
• Electroencephalography Phase Synchronization
• Female
• Humans
• Magnetic Resonance Imaging (methods)
• Male
• Middle Aged
• Models, Neurological
• Neural Pathways (physiology)
• Neurosurgical Procedures
• Reproducibility of Results
• Rest (physiology)
• Signal Processing, Computer-Assisted
• Unconsciousness (pathology)
• Wakefulness (physiology)