Neuroscientific model of near-death experiences finds consistent physiological pattern

A multidisciplinary team led by the University of Liège has proposed a unified neuroscientific model explaining the mechanisms behind near-death experiences (NDEs), drawing on converging empirical findings across neurobiology, psychology, and evolutionary theory.

Findings suggest that factors such as oxygen deprivation, increased carbon dioxide, and disrupted brain energy metabolism can initiate brain responses that lead to vivid perceptual and emotional experiences often reported during NDEs.

Subjects reporting NDEs describe a wide range of phenomena, though typically only certain types of experiences are elevated to the level of public interest.

Many intriguing NDEs capture the imagination, and selection bias pushes us toward focusing on experiences that appear thematically repetitive. Less retold are NDEs that, though just as vivid, contain nightmarish, mundane, or nonsense themes. Subjective states resembling NDEs can occur in both life-threatening and non-life-threatening situations, such as fainting and drug use.

Scientifically, NDEs are described as episodes of disconnected consciousness that occur in contexts involving actual or perceived physical threats. Reported experiences are highly varied in phenomenology, with content and interpretation shaped by triggering conditions such as the individual's psychological state and physiological responses.

Previous theories to explain NDEs have included psychological, neurophysiological, and evolutionary models, typically developed independently of a broader research framework.

In the review article, "A neuroscientific model of near-death experiences," published in Nature Reviews Neurology, researchers conducted a narrative review that draws on human and animal studies, psychedelic neuroscience, and clinical data to explain how altered states of awareness can emerge at critical moments.

No single experimental cohort was analyzed as the authors synthesized data from a range of previously published studies. Animal studies and neuroimaging data from critically ill patients provided insight into the physiological breakdown that may initiate NDEs.

A consistent pattern of physiological disruption emerged during cardiac arrest and other critical events. Reduced cerebral blood flow triggers hypoxia and elevates carbon dioxide levels.

A cascade of factors then induces cerebral acidosis and depletes ATP, the cell's primary energy source, and produces a surge in neurotransmitter release across multiple brain systems, including serotonin, dopamine, glutamate, noradrenaline, GABA, acetylcholine, and endorphins.

Key mechanistic details include elevated serotonin levels and 5-HT2A receptor activation, potentially contributing to visual hallucinations and feelings of hyper-reality. Dopamine release may influence emotional salience. Noradrenaline and acetylcholine appear linked to memory encoding. GABA and endorphins are proposed to induce calming sensations.

Researchers found parallels between NDEs and psychedelic-induced states, particularly with substances like DMT and ketamine, which affect similar receptor systems.

Psychological traits such as dissociation proneness and REM sleep intrusion tendencies may predispose individuals to experiencing NDEs under stress. Findings also suggest that NDEs and death-feigning behaviors (thanatosis) may share evolutionary roots as coping mechanisms.

Based on the convergence of neurobiological and psychological responses to severe physiological stress, researchers crafted NEPTUNE (Neurophysiological Evolutionary Psychological Theory Understanding Near-death Experience), a model to provide a comprehensive framework integrating diverse lines of evidence.

According to the study authors, "Our NEPTUNE model, although theoretical at present, provides a foundation for the next research phase, which will entail empirical testing of each mechanism."

Future research aims to empirically test aspects of the NEPTUNE model using neuroimaging, physiological monitoring, and continued exploration of brain activity near death.

NEPTUNE also raises questions about consciousness during critical illness and the potential reevaluation of brain death protocols in light of documented surges in brain activity after cardiac arrest.

—Justin Jackson

This article was originally published on MedicalXpress Breaking News-and-Events.