Consciousness and the Dying Brain

Abstract

The near-death experience has been reported since antiquity and is often characterized by the perception of light, interactions with other entities, and life recall. Near-death experiences can occur in a variety of situations, but they have been studied systematically after in-hospital cardiac arrest, with an incidence of 10 to 20%. Long attributed to metaphysical or supernatural causes, there have been recent advances in understanding the neurophysiologic basis of this unique category of conscious experience. This article reviews the epidemiology and neurobiology of near-death experiences, with a focus on clinical and laboratory evidence for a surge of neurophysiologic gamma oscillations and cortical connectivity after cardiac and respiratory arrest.

Illustration: Hyunock Nam.

Fig. 1.

Multidimensional framework for consciousness, including near-death or near-death-like experiences. IFT, isolated forearm test; NREM, non–rapid eye movement; REM, rapid eye movement. Used with permission from Elsevier Science & Technology Journals in Martial et al.; permission conveyed through Copyright Clearance Center, Inc.

Fig. 2.

End-of-life electrical surge observed with processed electroencephalographic monitoring. This Bispectral Index tracing started in a range consistent with unconsciousness and then surged to values associated with consciousness just before death and isoelectricity. Used with permission from Mary Ann Liebert Inc. in Chawla et al.; permission conveyed through Copyright Clearance Center, Inc.

Fig. 3.

Surge of feedforward and feedback connectivity after cardiac arrest in a rodent model. Panel A depicts time course of feedforward (blue) and feedback (red) directed connectivity during anesthesia (A) and cardiac arrest (CA). Panel B shows averages of directed connectivity across six frequency bands. Error bars indicate standard deviation. *** denotes P < 0.001.