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Front Hum Neurosci. 2017 Jun 28;11:328. doi: 10.3389/fnhum.2017.00328. eCollection 2017.

Network Efficiency and Posterior Alpha Patterns Are Markers of Recovery from General Anesthesia: A High-Density Electroencephalography Study in Healthy Volunteers.

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School of Physical and Occupational Therapy, Faculty of Medicine, McGill University.
Center for Consciousness Science, University of Michigan Medical SchoolAnn Arbor, MI, United States.
Department of Anesthesiology, University of Michigan Medical SchoolAnn Arbor, MI, United States.
Department of Anesthesiology, Washington University School of MedicineSt. Louis, MO, United States.
Department of Anesthesiology, University of PennsylvaniaPhiladelphia, PA, United States.
Neuroscience Graduate Program, University of Michigan Medical SchoolAnn Arbor, MI, United States.


Recent studies have investigated local oscillations, long-range connectivity, and global network patterns to identify neural changes associated with anesthetic-induced unconsciousness. These studies typically employ anesthetic protocols that either just cross the threshold of unconsciousness, or induce deep unconsciousness for a brief period of time-neither of which models general anesthesia for major surgery. To study neural patterns of unconsciousness and recovery in a clinically-relevant context, we used a realistic anesthetic regimen to induce and maintain unconsciousness in eight healthy participants for 3 h. High-density electroencephalogram (EEG) was acquired throughout and for another 3 h after emergence. Seven epochs of 5-min eyes-closed resting states were extracted from the data at baseline as well as 30, 60, 90, 120, 150, and 180-min post-emergence. Additionally, 5-min epochs were extracted during induction, unconsciousness, and immediately prior to recovery of consciousness, for a total of 10 analysis epochs. The EEG data in each epoch were analyzed using source-localized spectral analysis, phase-lag index, and graph theoretical techniques. Posterior alpha power was significantly depressed during unconsciousness, and gradually approached baseline levels over the 3 h recovery period. Phase-lag index did not distinguish between states of consciousness or stages of recovery. Network efficiency was significantly depressed and network clustering coefficient was significantly increased during unconsciousness; these graph theoretical measures returned to baseline during the 3 h recovery period. Posterior alpha power may be a potential biomarker for normal recovery of functional brain networks after general anesthesia.


alpha rhythm; cognition; consciousness; electroencephalography; general anesthesia; graph theory

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