December 2025
Orthodox neuroscience’s best-yet attempt to explain away Near-Death Experiences (NDEs) as mere physical side effects of the process of dying is weak, according to a critique by Dr. Bruce Greyson, one of the world’s leading experts in the subject, and his co-author Marieta Pehlivanova.
ILLUSTRATION FalcoZen / Pixabay
The winter edition of Psychology of Consciousness: Theory, Research, and Practice, Greyson and Pehlivanova point out numerous problems with the NEPTUNE theory (Neurophysiological Evolutionary Psychological Theory Understanding Near-Death Experience) put forth last spring by seven neuroscientists.
That theory, which received significant media coverage, was an attempt to unify fragmented ideas proposed by reductionist science to explain NDEs. All such ideas presume human consciousness is produced by the brain, so no consciousness exists without brain activity. The NDE phenomenon, NEPTUNE neuroscientists conclude, is nothing more than the dying brain’s attempt to cope. It’s a chain reaction of neurophysiological and psychological processes, starting with hypotension, oxygen deprivation, and elevated CO2, which produces dream-like visions and a calming effect for the dying person. The team suggests this may have some sort of evolutionary advantage.
However, Greyson‘s work — which includes pioneering NDE research for 50 years, serving as a professor emeritus of psychiatry and neurobehavioral sciences at the University of Virginia, and receiving the highest honor bestowed by the American Psychiatric Association (Distinguished Life Fellow) — has shown NDEs are more than a physical experience and consciousness exists outside the brain. This is consistent with post-materialist philosophy.
In the Psychology of Consciousness rebuttal, Greyson and his UVA co-author Marieta Pehlivanova acknowledge the NEPTUNE team made a “significant contribution to the literature” by collating evidence from diverse physiological hypotheses into one over-arching model. But deficiencies are considerable, ranging from omission of empirical data that doesn’t support or directly contradicts NEPTUNE’s speculations, to conflating or confusing NDEs with other phenomena.
For instance, the NEPTUNE theory claims NDEs are sparked by a drop in oxygen in the blood and an increase in carbon dioxide. (The neuroscientists limited their investigation to purported NDEs after heart attacks.) This hypoxia prompts a cascade of other processes, the theory claims.
Yet, while hypoxia and hypercarbia may be common results of cardiac arrest, two important studies involving large samples of NDE patients showed “increased or comparable oxygen and decreased or comparable carbon dioxide levels in Near-Death Experiencers compared with comparison patients,” according to Greyson and Pehlivanova. NEPTUNE did not consider these studies.
The NEPTUNE authors also suggest a region of the brain called the Temporoparietal Junction (TPJ) is electrically stimulated as part of the neurophysiological chain reaction leading to NDEs. But Greyson and Pehlivanova point out TPJ stimulation experiences are nothing like NDEs. Even patients in NEPTUNE’s own research citations believed their experiences were illusory, the rebuttal states. Classic NDE patients, in contrast, “perceive the event as profoundly real.” Further, there is no true Out-of-Body experience (OBE) after these TPJ stimulations, unlike many NDEs.
“Electrical stimulation studies have produced not OBEs but rather optical illusions in which experiencers do not believe themselves to have left their bodies. Despite these experiences being labeled by some researchers as OBEs, they are not labeled as such by the experiencers,” Greyson and Pehlivanova write.
NEPTUNE went so far as to cite one study (with a single patient case) where TPJ triggered a vision of a supernatural person “resembling the encounter of entities reported in NDEs.” Greyson and Pehlivanova noted the patient actually described this “entity” as something like her own shadow.
“This is not remotely comparable to the visions reported in many NDEs of identified deceased persons who are seen, heard, smelled, and touched, and interact meaningfully, conveying information to the experiencer,” the rebuttal reads.
Greyson and Pehlivanova note numerous other serious flaws in the NEPTUNE theory. But perhaps their most passionate objection is philosophical. The NEPTUNE team, led by Charlotte Martial of the University of Liége in Belgium, refused to consider any research that does not accept the “fundamental tenet of neuroscience that human experience arises from the brain.”
Greyson and Pehlivanova object to this outright bias, saying a substantial body of empirical evidence has emerged which challenges the strictly physicalist model. In fact, two of the four studies cited in NEPTUNE to support the “fundamental tenet,” were led by neuropsychiatrist Giulio Tononi, who has since disavowed the tenet, the rebuttal noted. Tononi has even castigated any “self-appointed tribunal” that demands the dogma of physicalism.
In their conclusion, Greyson and Pehlivanova said they are not altogether rejecting physical causes involved in Near-Death Experiences. Instead, they are asserting that “these physiological correlates alone are insufficient to account fully for the occurrence and phenomenology of NDEs.”
Written by Tom Zolper
Edited by Anders Bolling & Liza Horan
