Near-death experiences (NDEs) are episodes of disconnected consciousness with prototypical mystical features, often occurring during actual or perceived physical threat. Various explanatory theories have been proposed, but integration has been limited. Converging evidence from neuroscience—including non-human studies, psychedelic-induced mystical experiences, and research on the dying brain—now offers a comprehensive explanation. This Review discusses psychological and neurophysiological processes underlying NDEs, including cellular and electrophysiological brain network changes and neurotransmitter alterations. The authors propose a model encompassing a cascade of concomitant processes within an evolutionary framework and consider how NDE research informs debates on consciousness emergence near brain death.
In a small double-blind, placebo-controlled, cross-over trial with three adults who had prolonged disorders of consciousness after a coma, an intravenous sub-anesthetic dose of the atypical psychedelic ketamine increased brain complexity as measured by Lempel-Ziv complexity, but did not change the explainable consciousness indicator. Patients showed reduced spastic paresis and spent more time with their eyes open, yet their diagnosis of consciousness did not improve. No adverse effects occurred. The findings suggest a potential therapeutic role for ketamine in disorders of consciousness and support a link between brain complexity and conscious states.