A neuroscientific model of near-death experiences

Near-death experiences (NDEs) are episodes of disconnected consciousness that typically occur in situations that involve an actual or potential physical threat or are perceived as such, and the experiences are characterized by a rich content with prototypical mystical features. Several explanatory theories for NDEs have been proposed, ranging from psychological or neurophysiological to evolutionary models. However, these concepts were often formulated independently, and, owing to the fragmented nature of research in this domain, integration of these ideas has been limited. Lines of empirical evidence from different areas of neuroscience, including non-human studies, studies investigating psychedelic-induced mystical experiences in humans, and research on the dying brain, are now converging to provide a comprehensive explanation for NDEs. In this Review, we discuss processes that might underlie the rich conscious experience in NDEs, mostly focusing on prototypical examples and addressing both the potential psychological mechanisms and neurophysiological changes, including cellular and electrophysiological brain network modifications and alterations in neurotransmitter release. On the basis of this discussion, we propose a model for NDEs that encompasses a cascade of concomitant psychological and neurophysiological processes within an evolutionary framework. We also consider how NDE research can inform the debate on the emergence of consciousness in near-death conditions that arise before brain death.