Edited by Solomon H. Snyder, The Johns Hopkins University School of Medicine, Baltimore, MD, and approved July 9, 2013 (received for review May 2, 2013)
The brain is assumed to be hypoactive during cardiac arrest. However, the neurophysiological state of the brain immediately following cardiac arrest has not been systematically investigated. In this study, we performed continuous electroencephalography in rats undergoing experimental cardiac arrest and analyzed changes in power density, coherence, directed connectivity, and cross-frequency coupling. We identified a transient surge of synchronous gamma oscillations that occurred within the first 30 s after cardiac arrest and preceded isoelectric electroencephalogram. Gamma oscillations during cardiac arrest were global and highly coherent; moreover, this frequency band exhibited a striking increase in anterior–posterior-directed connectivity and tight phase-coupling to both theta and alpha waves. High-frequency neurophysiological activity in the near-death state exceeded levels found during the conscious waking state. These data demonstrate that the mammalian brain can, albeit paradoxically, generate neural correlates of heightened conscious processing at near-death.
↵1J.B. and U.L. contributed equally to this work.
Author contributions: J.B. and M.M.W. conceived the idea of the project; J.B. and G.A.M. designed experiments; J.B., U.L., and G.A.M. planned analysis; T.L. and D.P. performed electrode implantation; J.B., T.L., D.P., S.H., and D.K. collected data; U.L. wrote analysis programs; J.B., U.L., J.S., J.H., and G.A.M. analyzed data; and J.B., U.L., M.M.W., and G.A.M. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1308285110/-/DCSupplemental.
