Several readers of this blog have left comments trying to get me to comment on a recent study claiming to offer a "neuroscientific model of near-death experiences." The paper is behind a paywall, and my policy is never to pay for neuroscience research behind a paywall. Given the very strong tendency of neuroscientists these days to produce poorly designed junk science studies using bad methods, this is good policy for anyone to follow. Making a serious misstatement, the abstract of the paper makes no mention of anything that should make us suspect the paper is worth paying $30 for, and it fails to mention any new experimental research.
I can, however, make some comments on previous papers co-authored by the main author of the study (Charlotte Martial), papers that are publicly available. Her 2020 paper "Near-Death Experience as a Probe to Explore (Disconnected) Consciousness" is one that very badly mischaracterizes near-death experiences. She has a 3D chart in which a near-death experience is depicted as a state of the lowest wakefulness and the lowest connectedness. But contrary to such a description, it has been massively reported by those having near-death experiences that they had a super-high state of wakefulness and a super-high state of connectedness, with the description "realer than real" sometimes used. The study here backs up such claims.
Martial clumsily tries to define wakefulness as being a state of eyes open, but that is not correct. You can be wide awake with your eyes closed. Often awaking in the middle of the night for an hour or more, I routinely do some of my best thinking while lying awake in bed with my eyes closed, in a state of high wakefulness. Martial also makes some arbitrary definition of "connectedness" that seems to correspond to having regular sensory experience. The definition makes no sense in the context of near-death experiences, where people report a very high sense of connectedness that is different from regular sensory experiences.
In her 2020 paper Martial makes the extremely inaccurate statement that "no empirical study has confirmed that NDEs include some real external events." To the contrary, very many accounts of near-death experiences have discussed people describing details of the real world (including real events) during out-of-body experiences, events and details they should not have been able to have known about during some state of what looked like unconsciousness or cardiac arrest occurring during their near-death experiences. Many such accounts are described in my post here. Many other such accounts can be read in my series of 31 posts you can read here, such as my post here. We may presume that whatever "model" of near-death experiences Martial has described in her new paper behind a paywall, it probably involves confusions and mischaracterizations and misstatements similar to those in her 2020 paper "Near-Death Experience as a Probe to Explore (Disconnected) Consciousness," giving an additional reason not to spend thirty dollars to pay for a look at her latest "model."
We have in her 2020 paper vacuous skimpy hand-waving that ignores one of the central reasons why neuroscientists cannot explain near-death experiences that are rich in very vivid memories: the fact that such experiences often occur when the brain has electrically shut down, during the state of asystole that occurs within 15 or 20 seconds after the heart stops. Martial states, "Although memory theories have difficulties explaining NDEs and their resulting rich memory, an answer can be provided by theories demonstrating the importance of the medial temporal lobe for memory encoding and retrieval." This is a strange statement indeed. Theories do not demonstrate things; facts and observations demonstrate things.
No neuroscientist has any detailed credible theory of how a brain could do any such thing as memory encoding or memory retrieval, and there is no understanding of how any of the endless types of things humans learn and experience could ever be translated into brain states or synapse states. And if the brain were to do any memory encoding, it would require the normal electrical operation of the brain, which is often shut down while people are having near-death experiences, while brain waves (as measured by EEG devices) flatline. So it is false to claim as Martial did that "an answer can be provided by theories demonstrating the importance of the medial temporal lobe for memory encoding and retrieval." Neuroscientists are at an utter loss to credibly explain how any brain could form a memory during everyday living, and trying to explain how an electrically inactive brain could form a memory would be harder than explaining how a jet without any fuel could fly between cities. Microscopic examination of human brain tissue has never found any trace of stored memories and never found any trace of learned human knowledge.
The insinuation that the medial temporal lobe is necessary for memory is incompatible with the facts of epilepsy surgery outcomes. The temporal lobe is often removed to treat severe epilepsy, without any damage to memory or cognition, as I discuss in my post here. A paper states, "The data do not confirm concerns that patients undergoing temporal lobe epilepsy surgery are likely to develop accelerated memory decline over the longer term." See the appendix of this post for a discussion of how the data discredits the claim that the medial temporal lobe is vital for memory.
A 2018 paper co-authored by Martial had the misleading title "DMT Models the Near-Death Experience." The paper is critically discussed in my 2018 post here, where I find quite a few reasons for rejecting its validity. The study group sizes used were the usual way-too-small study group sizes used in neuroscience studies. There was one group of 3 subjects receiving 7 milligrams of DMT, another group of four subjects receiving 14 milligrams of DMT, and another group of five subjects receiving 20 milligrams. In a properly designed study of this type every study group would have consisted of at least 20 subjects.
The amount of DMT given in the study was utterly unrealistic for any discussion of a natural release of DMT. The question of DMT in the brain was clarified by David E. Nichols in a paper he authored in the Journal of Psychopharmocology. Speaking of DMT (also known as N,N-dimethyltryptamine) in the paper Nichols says, “It is clear that very minute concentrations of N,N-dimethyltryptamine have been detected in the brain, but they are not sufficient to produce psychoactive effects.” Addressing speculations that DMT is produced by the tiny pea-sized pineal gland in the brain, Nichols points out that the main purpose of the pineal gland is to produce melatonin, but the pineal gland only produces 30 micrograms of melatonin per day. But the pineal gland would need to produce about 20 milligrams of DMT (about 660 times more than 30 micrograms) to produce a mystical or hallucinatory experience. “The rational scientist will recognize that it is simply impossible for the pineal gland to accomplish such a heroic biochemical feat,” says Nichols. In the article in which he states that, it is noted that “DMT is rapidly broken down by monoamine oxidase (MAO) and there is no evidence that the drug can naturally accumulate within the brain.” Strassman attempted to detect DMT in the brains of 10 human corpses, but was not able to find any.
It is vital that any researcher asking subjects questions from the Greyson Scale (like the questions above) give us exact data on how high the numbers were in the answers given. But Martial failed to do that. Her paper merely reports what fraction of the respondents answered either 1 or 2 to each of the questions corresponding to the Greyson Scale. Failing to report the data that you collected (when it is extremely easy to do so) is a very bad defect in a research paper.
- 62% give the "extremely" answer (4) for "you had the impression of being outside of, or separated from your own body."
- 58% give the "extremely" answer (4) for "you had the sensation of leaving the earthly world or of entering a new dimension and/or environment."
- 56% give the "extremely" answer (4) for "you saw or felt surrounded by a bright light without any determined material origin."
- 35% give the "extremely" answer (4) for "your thoughts speeded up."
"Davies and Weeks (1993) did report one case of postoperative amnesia in a series of 58 cases of unilateral temporal lobectomy, whereas Walczak et al. (1990) found one case of marked deterioration in memory from a preoperative normal state in their series of 100 patients who underwent such surgery. Rausch and Langfitt (1992) estimated that, on the basis of their series, 'the prevalence of patients at risk for postoperative amnesia who otherwise met criteria for surgery fell between one and four out of 218’ (p. 508), and Jones‐Gotman et al. (1993) noted that 'the base‐rate of post‐resection amnesia, were all patients operated on without prior screening with the amobarbital procedure, may be less than 1%, (p. 447).' "
The authors of the 2003 paper state, "We were able to locate nine definite cases of amnesia following unilateral temporal lobe surgery in the English‐language literature." This is not very worrying, given that (1) many thousands of operations of this type were done before the year 2003; (2) doctors or scientists often loosely use the term "amnesia" for any of a large variety of memory performance problems, and typically use such a term for cases that are something other than a severe loss of learned or episodic memories; (3) there are many reasons why a person may have memory problems, and a few people having memory problem after a particular operation does not show the operation caused such a memory problem.
In fact, in Table 3 of the paper we are given the details of the impairments of these nine cases of claimed amnesia; and none of them sound like a case of loss of knowledge or episodic memories (with the possible exception of case 5, which is not well-described). We hear about what seem like rather minor memory performance shortfalls. A 2009 study carefully testing "before and after" memory results for 82 patients who had surgery for temporal lobe epilepsy tells us this: "The main finding of this study is that, at variance from the picture emerging from short-term follow-up studies, longer-term memory outcome after TLE [temporal lobe epilepsy] surgery seems to be good, as after 2 years memory performance was equal to or better than baseline [before surgery] in most patients." A review of 911 surgical operations for epilepsy (looking for bad effects) mentions no case of amnesia or memory loss or memory deterioration.
There is no robust evidence that surgical treatment for temporal lobe epilepsy causes loss of memories.