EEG over the occipital sites contains signatures of loss and recovery of consciousness during general anesthesia
Monday, Nov 14, 2011, 3:00 PM - 4:00 PM
, P. L. PURDON
, E. T. PIERCE
, J. L. WALSH
, A. F. SALAZAR-GOMEZ
, P. G. HARRELL
, C. TAVARES-STOECKEL
, K. HABEEB
, E. N. BROWN
Anesthesia, Critical Care and Pain Med., Massachusetts Gen. Hosp., Boston, MA;
Harvard Med. Sch., Boston, MA;
Brain and Cognitive Sci.,
Harvard-MIT Div. of Hlth. Sci. and Technol., MIT, Cambridge, MA
General anesthesia-induced unconsciousness is associated with substantial increases in electroencephalogram (EEG) power in the delta (0-4Hz), alpha (8-12Hz) and beta (12-30Hz) ranges at frontal electrode sites. This well-known pattern is called anteriorization. The analysis of EEG power changes at the occipital sites has received less attention. We recorded 64 leads of EEG while healthy volunteers underwent loss and recovery of consciousness induced by propofol delivered using a computer-controlled infusion. Level of consciousness was determined by the changes in the subjects’ responses to a set of auditory behavioral tasks. We computed the power spectra of the radial current density estimated at the EEG sites. Subjects were asked to keep their eyes closed during the entire experiment even when they were fully awake. Therefore, while the subjects were awake, a strong alpha rhythm was observed at the occipital electrode sites. We found a systematic relationship between the ratio of the alpha and delta power (ADR) over the occipital sites and the subjects' level of consciousness. In terms of the ADR the two-hour experiments could be divided into 5 distinct time periods: Awake (ADR>1); loss of consciousness (ADR~1); unconsciousness (ADR<1); recovery of consciousness (ADR~1); and awake (ADR>1). We previously reported the ADR changes when subjects lost consciousness in response to increasing doses of propofol (Society for Neuroscience, 2010, 343.4.). Our results suggest that the ADR computed from occipital EEG electrodes may be a readily discernible marker of loss of consciousness, the unconscious state and recovery of consciousness under general anesthesia.
[Authors]. [Abstract Title]. Program No. XXX.XX. 2011 Neuroscience Meeting Planner. Washington, DC: Society for Neuroscience, 2011. Online.
2011 Copyright by the Society for Neuroscience all rights reserved. Permission to republish any abstract or part of any abstract in any form must be obtained in writing by SfN office prior to publication.
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