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On the Neuropsychology of Near-Death Experiences


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Near-death experiences are a pan-human phenomenon involving conscious imaginal experience in temporal proximity to (perceived) physical death. This essay reviews two popular theories on their neurobiological underpinnings. These are the DMT-Pineal hypothesis, and the fight-or-flight REM-intrusion model of Kevin Nelson. After reviewing the evidence for, and shortcomings of, each theory, some amendments based on sounder neuroscience are proposed. Of notable importance, is the evidence for and function of endogenous dream states in the near-death experience. Based on a neuropsychological interpretation of dreams, some tentative claims are made that may be open to further investigation.
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RUNNING HEAD: Neuropsychology of Near-Death Experiences
On the Neuropsychology of Near-Death Experiences
An Amended Version of an Essay
Submitted in Partial Completion of an Honours Degree in Psychology
The University of Cape Town
Psychology Department
Paul J. Brusser
Course Convener
Mark Solms
Word Count
Abstract: 94
Main Body: 2694
Neuropsychology of Near-Death Experiences 2
Near-death experiences are a pan-human phenomenon involving conscious imaginal
experience in temporal proximity to (perceived) physical death. This essay reviews two
popular theories on their neurobiological underpinnings. These are the pineal-DMT
hypothesis, and the fight-or-flight REM-intrusion model of Kevin Nelson. After reviewing
the evidence for, and shortcomings of, each theory, some amendments based on sounder
neuroscience are proposed. Of notable importance, is the evidence for and function of
endogenous dream states in the near-death experience. Based on a neuropsychological
interpretation of dreams, some tentative claims are made that may be open to further
Neuropsychology of Near-Death Experiences 3
On the Neuropsychology of Near-Death Experiences
Near-death experiences (NDEs) are a pan-human phenomenon involving conscious
imaginal experience in temporal proximity to (perceived) physical death. Subjective reports
convey qualities fitting with what William James (1902) considered to be the defining
characteristics of religious experiences i.e. they are noetic (somehow comprehensible, or
meaningful), ineffable (or indescribable post-hoc), transient, and passive (happen to one,
rather than being manifest through agency). A classic NDE proceeds as follows. Beginning:
There is a recognising of crisis, a noise (buzzing), a dark tunnel, and/or a light, or feelings of
serenity. Middle: involves out-of-body experiences, meetings with others, divine light, life
review, and/or reaching a border. End: involves a process of “returning” (Greyson, 1999).
Greyson (1999) has described cognitive, affective, and transcendental types of NDEs; and
these types can be phenomenologically blissful or “hellish”. Greyson (1999) contended that
his contemporary descriptive survey-methods were insufficient to uncover the underlying
aetiology and functionality of NDEs. This mysterious phenomenon is present in a third of
persons who have come close to death, or about 5% of the American population, and confer
profound impacts onto their subjects including (but not limited to) decreased suicidal
ideation, and posttraumatic and spiritual growth (Greyson, 1997, 2003).
Neuropsychological Theories
Building off of Greysons work, Nelson (2011) has proposed a physiological
mechanism for NDEs such that: “Near-death experiences work in the brain as a confluence of
low-blood flow to the eyes, fight-or-flight reactions, and the triggering of REM
consciousness. Physiologically, that’s it” (p.218). The only other line of research I am aware
of that is not lesion-based exists on the pineal-DMT spectrum, which I review first. N-N-
Dimethyltryptamine (DMT) is a naturally occurring tryptamine found in the human body
(and other life-forms), and the psychoactive ingredient in the now almost-infamous
Ayahuasca brew originating from South American religious or shamano-mystical traditions.
DMT’s popularity has grown since the 1950s, culminating in the work of Rick
Strassman (2001) with some of the first American research into psychedelic substances since
the ban in 1960s (Rodriguez, 2007). In a Cartesian renaissance, Strassman (2001) has been
pursuing the hypothesis that the pineal gland produces large amounts of DMT, “[mediating]
the pivotal experiences of deep meditation, psychosis, and near-death experiences” (p. 69).
The DMT experience seems to share similar aspects with NDEs (see Figure 1), including: an
exponentially rising, buzzing noise; realer than real imagery; and a transition into another
world (Rodriquez, 2007). Several of Strassman’s (2001) participants in the DMT trials
Neuropsychology of Near-Death Experiences 4
Figure 1: “Phases of the typical high dose DMT experience” (Rodrigues, 2007, p.3).
reported leaving their body, merging with ‘Creation’, encountering other beings, and feeling
OK about not returning; alongside a few who had NDEs before noting the similarity in the
experience. Brain-imaging studies of people who have ingested Ayahuasca show large
increased activity of brain areas BA30 and BA37, correlated with episodic memory function
and contextual mental associations, as well as the anterior BA10. These effects were found to
be largest when subjects were asked to close their eyes (de Araujo et al., 2012).
Strassman (2001) reasoned that the difference between DMT-states and NDEs was
that there was no necessarily-present recognition of an actual physiological death in the short
15-minute experiences. The theory still has a long way to go (Barker, Borjigin, Lomnicka, &
Strassman, 2013). The most solid evidence is that DMT is one of many ligands that act upon
sigma-1 receptor sites, possibly produced by chemical processes involving floating indole-N-
methyl transferase (INMT; Mavlyutov, Epstein, Liu, Verbny, Ziskind-Conhaim, & Ruoho,
2012). Any traces of DMT in the pineal gland may be due to presence of sigma-1 sites and
INMT (Frecska, Szabo, Winkelman, & McKenna, 2013). However, necessary connections to
any endogenous dream or near-death state have not been established.
There is no consensus or strong evidence on what the neurology of NDEs consists of
(Braithwaite, 2008; Facco & Agrillo, 2012), but Nelson (2011) proposes one of the stronger
and more encompassing theories. To reiterate: “Near-death experiences work in the brain as a
confluence of low-blood flow to the eyes, fight-or-flight reactions, and the triggering of REM
consciousness” (p.218). This is a dappled view of NDEs, and I will review the premises
Blood Flow and Anoxia
It has been reliably demonstrated amongst air-force pilots and in fainting studies (i.e.
in syncopic conditions) that reduced cerebral blood-pressure can result in tunnel vision and
hallucination. Out-of-body experiences (OBEs) are present in 16% of fainting cases, audible
noises or voices in 60%, and visual hallucinations in over 50% of cases (Nelson, 2011).
Generally it is found that syncope (temporary loss of consciousness due to low blood
Neuropsychology of Near-Death Experiences 5
pressure) results once, from standing, an average blood-pressure of 50mmHg at heart level is
reached (Wieling, Thijs, Van Dijk, Wilde, Benditt, & van Dijk, 2009), or blood-pressure to
the head is immediately dropped by a neck-cuff (Rossen, Kabat, & Anderson, 1943). Within
6 seconds of syncopic induction the eyes fixate on the midline, and sometimes turn upwards
(Rossen et al., 1943). EEG recordings generally show little to no cortical activity (Wieling et
al., 2009).
As noted by Nelson (2011), the high prevalence of syncopic symptoms in NDEs
probably is due to the high proportion of anoxic or syncopic conditions in which NDEs occur.
Amongst 55 subjects of NDEs, cases included blacking out (10 subjects), heart disturbance (8
subjects), near-drowning (8 subjects), car accidents (8 subjects), together alone totalling 68%
of participants in Nelson’s (2011) survey. Considering the dappled nature of Nelson’s theory,
these findings should be kept in mind as a common ingredient of the NDE.
Fight-or-Flight and REM-intrusion
One plausible evolutionary hypothesis for NDEs is that they occur as a defence
mechanism that is, in extreme survival situations it is better to feign death than risk further
attention and injury. Nelson (2011) argues that intense pain or blood-loss causes the
ventrolateral periaqueductal gray to ‘reign in’ the sympathetic, adrenal, fight-or-flight
response to crisis, and activate the parasympathetic nervous system and rapid eye-movement
(REM) sleep. In this state, heart-rate slows in frequency and intensity. However, feigning
death may be better described as an opioid mediated parasympathetic state (Lanius, Paulsen,
& Corrigan, 2014). Schore (2001) theorises this mechanism to be at work in dissociative
states amongst children with traumatic relational histories.
Nelson (2011) made one error: that during REM sleep the sympathetic nervous
system is actually activated although the body is paralysed, keeping it from acting out
dreams. What of the NDE can be determined thus far is that life-threatening trauma and
cortical blood-pressure drops can often result in fainting and analgesic dissociation, and
sometimes OBEs. Greyson (2000) found that people who experienced NDEs are more likely
to report dissociative symptoms in other areas of life. The exclusion of the REM hypothesis
challenges Nelson’s (2011) proposition that it is the “REM-consciousness” which produces
the dream-imagery, bright light, and other beings reported in NDEs.
Cardiac Arrest, NDEs, and Rats
A point of importance to consider here is the sequence of the classic NDE. Subjects
often report tunnel vision, and/or OBEs, and most often a feelings of peace or serenity. Thus
far I have attributed these to low-blood pressure, opioids, and dissociation in most, if not
Neuropsychology of Near-Death Experiences 6
all, cases overlapping. Subjects usually only then report a brilliant light which Nelson (2011)
attributed to REM-consciousness. One of Nelson’s (2011) interviewees typifies this in her
recounting of hearing her own death being announced while being immersed in white light
and taken to “the other side”. Other NDE reports are similar but do not result in spiritual
envelopment. To this end I wish to delineate two separable phases in the classic NDE, and I
consider the latter to be NDEs-proper.
Borjigin et al. (2013) artificially induced cardiac arrest in rats and:
identified a transient surge of synchronous gamma oscillations that occurred within
the first 30s after cardiac arrest and preceded isoelectric electroencephalogram.
Gamma oscillations during cardiac arrest were global and highly coherent; moreover,
this frequency band exhibited a striking increase in anteriorposterior-directed
connectivity and tight phase-coupling to both theta and alpha waves (p. 1432).
Further research revealed that 60s after cardiac arrest, electroencephalogram (EEG)
recordings showed synchronised spikes with electrocardiogram (EKG) readings from the
heart. This “corticocardiac coherence” continued until the 300s point and ventricular
fibrillation occurred (Li et al., 2015). Li et al. (2015) also measured a significant rise in
cortical adenosine, dopamine, norepinephrine, serotonin, GABA, glutamate, and aspartate
immediately following asphyxia. “Secretion was detected for as long as 20 min of asphyxia
for all neurotransmitters tested” (p. E2076). Dopamine levels were already rising at time 0s,
and were 12-fold by the time 60s.
Greyson, Kelly, & Dunseath (2013) critiqued of Borjigin et al. (2013) rightfully that
electrical activity is not equivalent to conscious experience. More pertinently though, they
cited that EEG recordings on humans become isoelectric after 10s, and that while all of
Borjigin et al.’s (2013) rats showed this electrical surge, only 18-20% of human cardiac
survivors report NDEs. Borjigin, Wang, and Mashour (2013) noted that human EEG
recordings were obtained using scalp electrodes whereas their electrodes were intracranial. In
light of the further research (Li et al., 2015), it appears that not only is there robust evidence
of sustained (and coherent) electrical activity but also neurotransmitter secretion following
asphyxia. Taken as true, I would consider the 18-20% prevalence of NDEs to be indicative of
whether the trauma of cardiac arrest resulted in a de-activation of the hypothalamic memory
encoding systems.
Given the aforementioned evidence it would appear that the sequence of the classic
NDE proceeds from a dissociative state to a neurological surge at the point of cardiac arrest
or asphyxia. Given the dream-imagery of NDEs, I must now note that REM sleep and
Neuropsychology of Near-Death Experiences 7
dreaming are neurologically dissociable (Solms & Turnbull, 2002). Damage to the pontine
structures generative of REM sleep do not preclude dreaming, and damage to dream
generative dopamine pathways and occipitotemporo-parietal junction do not preclude REM
sleep. The dopamine rush evident during asphyxia may be evidence of the activation, and
possibly hyper-activation, of dreaming systems resulting in hallucinatory imagery. More
importantly, this imagery takes over following the dissociative “journey through the tunnel”.
That is to say, instead of constructing the objects of experience from sensory modalities, the
mental apparatus inverts the image-generating function to form the objects of experience by
retrieving information from its internal stores (Solms & Turnbull, 2002). This is the same
inversion of activation seen in the Ayahuasca subjects when their eyes were closed (de
Araujo et al., 2012).
Dreaming of God
If my above hypothesis is correct, there is still the question as to why the nature of the
NDE-dream is so intense, sublime, and religious. It would be useful here if the DMT-
hypothesis were confirmed as DMT naturally produces strikingly vivid and spiritual dream-
imagery. What I can hypothesise is that the vividness is due to the magnitude of the
dopamine surge. Administration of L-Dopa (a dopamine precursor) is associated with
increased vividness and emotionality of dreams in subjects. Vice versa, antipsychotics
(dopamine antagonists) reduce vividness (Sacks, 1973; Solms & Turnbull, 2002).
A second point to consider is why NDEs are indescribable, or ineffable in James’s
(1902) terms. One possible explanation relates to anoxia: although the brain is dreaming, left
temporal areas associated with language (in the cortical extremities) may be progressively
less-active due to anoxia and glucose deprivation. This may explain why so much of the
communication in NDEs is “telepathic”. This may be credible as anomia is a frequently
observed cognitive deficit following sustained anoxia. Another explanation is simply the
absolute non-ordinary nature of the NDE. Symbolic and telepathic communication are
pervasive in DMT experiences, although cognition usually remains intact, lingual, and
undistorted. What makes them ineffable is simply the fact that there is no cultural discourse
for such experiences (Strassman, 2001).
A third point, why do NDEs so often contain motifs of a God-archetype or close
relatives, who often communicate whether the subject will be returning to life? While many
Americans and English report returning for love or unfinished work, Indians often report
being incorrectly processed by a giant bureaucracy (Mauro, 1992). Nahm (2009) claims to
have found examples of ‘mistaken’ deaths and ‘correction’ cases among Roman NDE
Neuropsychology of Near-Death Experiences 8
reports. With these historically and culturally variabled reasons for return, one might be
tempted to say these dream-characters to represent the subject’s own will-to-live. Yet, even in
cases where the subject desires not to return, the beings may instruct their return (Nelson,
2011). Thus it is reasonable that the dream characters exist as a confluence of both the
subject’s motivated imagoes and the representation of the body’s physical state. The
corticocardiac coherence reported by Li et al. (2015) may be of interest in this regard. Li et al.
(2015) reported that “blocking the brain’s autonomic outflow significantly delayed terminal
ventricular fibrillation and lengthened the duration of detectable cortical activities despite
the continued absence of oxygen” (p. E2073, emphases added). It thus appears to be the case,
in rats, that cortical coherence is correlated with a recovery of heart-rate 20-30s after anoxia,
but after 60s the corticocardiac coherence acts to actually accelerate the dying process. If the
dream-state is active, and the brain-body is actively involved in its own demise then the
NDE-characters may be ‘messengers’ as to the prognosis of the subject. There are many
epistemological issues here of course. We have no data regarding people who actually died,
or at what exact time points the phenomena occur. These propositions are tentative to say the
least, but I wish to include one more possible element in the NDE.
Agency in the Bardo
Many NDE-subjects report sleep-paralysis and lucid dreaming in their ordinary lives.
During lucid dreaming, in which the dreamer is aware of the dream-state and can have
control over the dream, that there is strong 40 Hz coherence between frontal and occipital-
parietal regions, and possible activation of the dorsolateral prefrontal cortex (Hobson, 2009).
What this means is that agency is available to the dreamer. It was Nelson’s (2011) hypothesis
that a “lagged REM switch” resulted in the confluence of dreaming and waking
consciousness. We can see that, whatever the mechanism, considering that many NDE-
subjects report actively begging god for their return, it raises the question of whether the
human subject has a degree of influence on the corticocardiac motivated death measured in Li
et al.’s (2015) rats. Such a hypothesis is reminiscent of the Tibetan Book of the Dead which
illustrates the challenges faced by the dead in the ‘bardo’ (or “transitionary state”) such that
one may choose one’s karmic path.
I have attempted to outline, amend, and integrate established knowledge on the
neurology and neuropsychology of NDEs. There remain many unanswered questions, and the
epistemological and methodological issues of studying humans on the cusp of no return
makes the project no easier. I have, however, attempted to lay out some hypotheses that may
Neuropsychology of Near-Death Experiences 9
be testable or at least open to further investigation. The DMT studies are useful for
phenomenological comparison, although their intersection with endogenous states is at the
moment unestablished. What does seem to be the case though is that the NDE-proper is the
result of an endogenous neuro-electrical surge after asphyxia, whereas other dissociative
reactions to trauma are exactly just that, although often present in NDE subjects. The
disproportional presence of dissociative and sleep-paralytic experiences amongst NDE
subjects may be pertinent to understanding the presence of memory and agency during NDEs.
It was beyond the scope of this essay to examine the differentiation of blissful and “hellish
NDEs, but given the evidence reviewed, research into approach and avoidance in dreams may
be informative in this regard (Malcolm-Smith, Koopowitz, Pantelis, & Solms, 2012).
On a final note: neo-dualist survivalists still wish to prove the continuation of
dynamic consciousness after death (Braithwaite, 2008). What rather seems to be the case, as
is in modern neuroscience, is that there is no mind-activity uncorrelated to brain-activity. The
survivalist may take consolation in knowing that concepts of self, other, and time appear to
disintegrate as NDEs progress and that their end, if they are so fortunate to experience it, will
be a moment of uncomprehended, timeless bliss, bathed in a wash of white dream-light.
Anything thereafter, we do not, and for all we do know, we cannot, know.
Neuropsychology of Near-Death Experiences 10
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Full-text available
N,N-dimethyltryptamine (DMT) is classified as a naturally occurring serotonergic hallucinogen of plant origin. It has also been found in animal tissues and regarded as an endogenous trace amine transmitter. The vast majority of research on DMT has targeted its psychotropic/psychedelic properties with less focus on its effects beyond the nervous system. The recent discovery that DMT is an endogenous ligand of the sigma-1 receptor may shed light on yet undiscovered physiological mechanisms of DMT activity and reveal some of its putative biological functions. A three-step active uptake process of DMT from peripheral sources to neurons underscores a presumed physiological significance of this endogenous hallucinogen. In this paper, we overview the literature on the effects of sigma-1 receptor ligands on cellular bioenergetics, the role of serotonin, and serotoninergic analogues in immunoregulation and the data regarding gene expression of the DMT synthesizing enzyme indolethylamine-N-methyltransferase in carcinogenesis. We conclude that the function of DMT may extend central nervous activity and involve a more universal role in cellular protective mechanisms. Suggestions are offered for future directions of indole alkaloid research in the general medical field. We provide converging evidence that while DMT is a substance which produces powerful psychedelic experiences, it is better understood not as a hallucinogenic drug of abuse, but rather an agent of significant adaptive mechanisms that can also serve as a promising tool in the development of future medical therapies.
Full-text available
The brain is assumed to be hypoactive during cardiac arrest. However, the neurophysiological state of the brain immediately following cardiac arrest has not been systematically investigated. In this study, we performed continuous electroencephalography in rats undergoing experimental cardiac arrest and analyzed changes in power density, coherence, directed connectivity, and cross-frequency coupling. We identified a transient surge of synchronous gamma oscillations that occurred within the first 30 s after cardiac arrest and preceded isoelectric electroencephalogram. Gamma oscillations during cardiac arrest were global and highly coherent; moreover, this frequency band exhibited a striking increase in anterior-posterior-directed connectivity and tight phase-coupling to both theta and alpha waves. High-frequency neurophysiological activity in the near-death state exceeded levels found during the conscious waking state. These data demonstrate that the mammalian brain can, albeit paradoxically, generate neural correlates of heightened conscious processing at near-death.
Full-text available
We report a qualitative liquid chromatography-tandem mass spectrometry (LC/MS/MS) method for the simultaneous analysis of the three known N,N-dimethyltryptamine endogenous hallucinogens, their precursors and metabolites, as well as melatonin and its metabolic precursors. The method was characterized using artificial cerebrospinal fluid (aCSF) as the matrix and was subsequently applied to the analysis of rat brain pineal gland-aCSF microdialysate. The method describes the simultaneous analysis of 23 chemically diverse compounds plus a deuterated internal standard by direct injection, requiring no dilution or extraction of the samples. The results demonstrate that this is a simple, sensitive, specific and direct approach to the qualitative analysis of these compounds in this matrix. The protocol also employs stringent MS confirmatory criteria for the detection and confirmation of the compounds examined, including exact mass measurements. The excellent limits of detection and broad scope make it a valuable research tool for examining the endogenous hallucinogen pathways in the central nervous system. We report here, for the first time, the presence of N,N-dimethyltryptamine in pineal gland microdialysate obtained from the rat. Copyright © 2013 John Wiley & Sons, Ltd.
Greyson et al. (1) state that it is misleading to describe the rat brain as hyperaroused because the EEG power at near death was only a small fraction of that of the waking state in our study (2). However, they neglect to note that we showed that the power of EEG signals associated with consciousness increased in every rat we tested [see figure 2A of Borjigin et al. (2)]. Greyson et al. posit that “the pertinent question here is not whether there is any brain electrical activity at all after cardiac arrest, but whether there is activity of the type currently thought to be necessary for conscious experience.” In complete accordance with their opinion, our entire study (2) is devoted to demonstrating the presence of electrical fingerprints of consciousness in the near-death brain. We report increased power and global synchrony in the gamma bandwidth, two neurophysiologic features associated with conscious processing. Moreover, this gamma band exhibits an eightfold increase in top-down information processing (thought to be a key element of consciousness) and fivefold increase in bottom-up information flow (thought to represent sensory information processing) at near death. In addition, we found tight coupling of gamma bands with both theta and alpha bands, yet another indicator of conscious information processing in the postarrest brain. Thus, our work (2) directly answers the concern of Greyson et al.
Borjigin et al. (1) describe recordings from electrodes implanted in rat brains that were made during and after cardiac arrest in rats. The surprising and unexplained 30-s surge in electrical coherence and connectivity certainly merits further study, but the authors’ suggestion that this transient electrical surge has implications for near-death experiences in humans seems premature to us.
Numerous investigations have been concerned with the effects of acute arrest of cerebral circulation in animals. The earlier workers¹ studied the effects of ligation of the cerebral arteries. More recently, observations have been made on the effects of temporary occlusion of the chief cerebral arteries² and of temporary cessation of the heart beat.³ Using the method of occlusion of the chief cerebral arteries, Sugar and Gerard⁴ measured the survival time for different regions of the cat brain by the persistence of spontaneous action potentials. A careful study of the changes in function and structure of the brain of the cat resulting from temporary occlusion of the pulmonary artery was reported on by Weinberger, Gibbon and Gibbon.⁵ These methods involved one or another of the following complications: anesthesia; surgical procedures at the time of arrest of circulation in the brain; incomplete arrest of circulation as a