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Towards a Neuro-scientific Explanation of Near-death Experiences?

Authors:
  • University Hospital of Liège, GIGA Consciousness, University of Liège, Belgium

Abstract and Figures

Near-death experiences can be defined as “profound psychological events with transcendental and mystical elements, typically occurring to individuals close to death or in situations of intense physical or emotional danger. These elements include ineffability, a sense that the experience transcends personal ego, and an experience of union with a divine or higher principle” [1]. Common elements recurring in near-death experiences are experiencing a panoramic life review, feelings of peace and quiet, seeing a dark tunnel, experiencing a bright light, or out-of-body experiences [1] (Fig. 1). During an out-of-body experience, people seem to be awake and see their own body and the world from a location outside their physical body [2] (Fig. 2). Some spiritual and psychological theories have been developed in order to explain near-death experiences and out-of-body experiences. Clinical studies have aimed at determining their frequency and assessing precipitating factors. Recent studies have shown the involvement of the temporo-parietal cortex in the generation of out-of-body experiences and offer a neurological account for the phenomenon, rebuffing dualistic, non-physical explanations. In this chapter, we discuss what is and is not known about the neuronal correlates of these extraordinary experiences. Fig. 1. Common elements recurring in near-death experiences are seeing a dark tunnel, experiencing a bright light, feelings of peace and quiet, experiencing a panoramic life review or out-of-body experience (from Hieronymus Bosch, 1500s “Paradise and the Ascent in the Empyrean” left; and Schiavonetti, 1808 “The soul leaves the body at the moment of death” right). Fig. 2. One of the principal components of near-death experiences is out-of-body experiences. An out-of-body experience is defined by the presence of disembodiment, the impression of seeing the world from an elevated and distanced visuo-spatial perspective and the impression of seeing one’s own body from this perspective. Studies have shown that electrical stimulation of the temporo-parietal junction (highlighted in gray) can generate out-of-body experiences (with permission from Cliff Laureys)
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Towards a Neuro-scientific Explanation
of Near-death Experiences?
A. Vanhaudenhuyse, M. T honnard,andS. Laureys
Introduction
Near-death experiences can be defined as “profound psychological events with tran-
scendental and mystical elements, typically occurring to individuals close to death
or in situations of intense physical or emotional danger. These elements include
ineffability, a sense that the experience transcends personal ego, and an experience
of union with a divine or higher principle ” [1]. Common elements recurring in
near-death experiences are experiencing a panoramic life review, feelings of peace
and quiet, seeing a dark tunnel, experiencing a bright light, or out-o f-body experi-
ences [1] (
Fig. 1). Dur i ng an out-of-body experience, people seem to be awake a nd
see their own body and the world from a location outside their physical body [2]
(
Fig. 2). Some spiritual and psychological theories have been developed in order to
explain near-death experiences and out-of-body experiences. Clinical studies have
aimed at determining their frequency and assessing precipitating factors. Recent
studies have shown the involvement of the temporo-parieta l cortex in the generation
of out-of-body experiences and offer a neurological account for the phenomenon,
rebuffing dualistic, non-physical explanations. In this chapter , we discuss what is
and is not known about the neuronal correlates of these extraordinary experiences.
Fig. 1. Common elements recurring in near-death experiences are seeing a dark tunnel, experiencing a
bright light, feelings of peace and quiet, experiencing a panoramic life review or out-of-body experience
(from Hieronymus Bosch, 1500s Paradise and the Ascent in the Empyrean” left;andSchiavonetti,1808
“The soul leaves the body at the moment of death right).
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Fig. 2. One of the principal components of near-death experiences is out-of-body experiences. An out-of-
body experience is defined bythepresenceofdisembodiment,theimpressionofseeingtheworldfrom
an elevated and distanced visuo-spatial perspective and the impression of seeing ones own body from this
perspective. Studies have shown that electrical stimulation of the temporo-parietal junction (highlighted in
gray) can generate out-of-body experiences (with permission from Cliff Laureys)
Near-death Experiences
Definition
It is important to stress that near-death experiences occur in what is considered
‘near-death’, i.e., the patient being in transitory and reversible cardiac arrest (clinical
death). Under the US Uniform Determination of Death Act [3], a person is dead
when physicians determine, by applying prevailing clinical criteria, that cardiorespi-
ratory or brain functions are absent and cannot be retrieved. Clinical death is a term
to be avoided, referring in popular media to cessation of blood circulation and
breathing. Without resuscitation, recovery of brain function more than 3 minutes
after a cardiac arrest is rare. This notion of irreversible is reflected in the ‘Pittsburgh
Protocol for non-heart-beating organ donation (now called organ donation after
cardiac death). Here, patients who are hopelessly brain-damaged (but not brain
dead) can have their life-sustaining therapy (e.g., positive-pressure ventilation) with-
962 A. Vanhaudenhuyse, M. Thonnard, and S. Laureys
XXV
drawn. Once their heart stops beating for a period of 3 10 minutes (length varies by
protocol), they can be declared dead (and only then can organs be procured) [4, 5].
At present, there are no universally accepted definitions of near-death experi-
ences. Nevertheless, there are many ways of categorizing its phenomenological ele-
ments. Moody [6] identified a number of common elements recurring in near -death
experiences: Ineffability, hearing oneself pronounced dead, feelings of peace and
quiet, hearing unusual noises, seeing a dark tunnel, being out of the body’, meeting
‘spiritual beings’, experiencing a bright light or a being of light, panoramic life
review, experiencing a realm in which all knowledge exists, experiencing cities of
light, exper iencing a realm of bewildered spirits, experiencing a supernatural res-
cue’, sensing a border or limit, coming back ‘into the body’.
Structured interview of individuals who have had a near-death experience have
identified five stages occurring in the following order: (1) A feeling of peace and
well-being; (2) separation from the physical body; (3) entering a region of darkness;
(4) seeing a brilliant light; (5) going through the light and entering another realm.
The two scales most commonly used to quantif y the subjective experience of near-
death experiences are the Weighted Core Experience Index (WCEI) [7] and the Gre-
yson Near-death Experience Scale [8]. The WCEI includes ten components which are
scored for their presence or absence (maximum score is 29) (
Table 1).
The Gre yson Near-death Experience Scale [8] is a revision of the WCEI and has
146 questions (maximum score of 32). In order to consider the subjective report as
being a true near-death experience, a minimum score of 7 needs to be recorded
(
Table 2).
Theoretical Approaches: Spiritual, Psychological and Organic Hypotheses
Spiritual interpretations consider the existence of near-death experiences as strong
evidence that the mind (i.e., soul) can be separated from the physical body. Support-
ers of this theory consider that near-death experiences provide a glimpse of the spir-
itual realm to which the soul migrat es after death. The second category encompasses
psychological theories according to which near-death experiences are a type of
depersonalization, acting as a protection against the threat of death in situations of
intense danger, by allowing an engagement in pleasurable fantasies [9]. Others ha ve
prop osed a concept of psychological absorption, which may be defined as the ten-
dency to focus attention on imaginative or selected sensory experiences to the exclu-
Table 1. Characteristics of near-death experiences as reported by 62 cardiac arrest survivors, according to
the Weighted Core Experience Index (WCEI) [22].
Number of patients (%)
Awareness of being dead 31 (50 %)
Positive emotions 35 (56 %)
Out-of-body experiences 15 (24 %)
Moving through a tunnel 19 (31 %)
Communication with light 14 (23 %)
Observation of colors 14 (23 %)
Observation of a celestial landscape 18 (29 %)
Meeting with deceased persons 20 (32 %)
Life review 8 (13 %)
Presence of border 5 (8 %)
Towards a Neuro-scientific Explanation of Near-death Experiences? 963
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Table 2. Characteristics of near-death experiences according to the Greyson Near-death Experience Scale.
Number of cardiac arrest survivors (%)
Parnia et al., 2001
[21] (n = 4)
Greyson, 2003
[24] (n = 27)
Cognitive features
Did time seem to speed up or slow down? 2 (50 %) 18 (66 %)
Were your thoughts speeded up? 0 12 (44 %)
Did scenes from your past come back to you? 0 8 (30 %)
Did you suddenly seem to understand everything? 1 (25 %) 8 (30 %)
Emotional features
Did you have a feeling of peace or pleasantness? 3 (75 %) 23 (85 %)
Did you see, or feel surrounded by, a brilliant light? 3 (75 %) 19 (70 %)
Did you have a feeling of joy? 3 (75 %) 18 (66 %)
Did you feel a sense of harmony or unity with the universe? 2 (50 %) 14 (52 %)
“Paranormal” features
Did you feel separated from your body? 2 (50 %) 19 (70 %)
Were your senses more vivid than usual? 2 (50 %) 4 (15 %)
Did you seem to be aware of things going on elsewhere, as if
by extrasensory perception?
2(50%) 3(11%)
Did scenes from the future come to you? 0 2 (7 %)
Transcendental features
Did you seem to enter some other, unearthly world? 2 (50 %) 17 (63 %)
Did you seem to encounter a mystical being or presence, or
hear an unidentifiable voice?
2(50%) 14(52%)
Did you come to a border or point of no return? 4 (100 %) 11 (41 %)
Did you see deceased or religious spirits? 1 (25 %) 7 (26 %)
sion of stimuli fro m the external environment [10]. However, some authors have
pointed out that near-death experiences differ from depersonalization in the sense
that what is distorted is not ones sense of identity but the association of ones iden-
tity with ones bodily sensations. In this v iew, near-death experiences are considered
as a dissociation of self-identity from bodily sensations and emotions [11].
The last category encompasses so-called organic hypotheses. A large number of
theories have attempted to account for components of near-death experience in
terms of brain dysfunctions. Some authors have considered the possible role of
abnormal levels of blood gases. Indeed, ano xia [12] and hypercarbia [13] can pro-
duce symptoms including seeing bright lights, having out-of-body experiences, reli-
ving past memories, and inducing mystical experiences. Other authors have sug-
gested that near-death experience can be reported as hallucinatory experiences
caused in part by, for example, endorphin [14], serotonin [15], or ketamine [16, 17]
release. More recent theories have proposed that temporal lobe dysfunction ma y
explain out-of-body experiences [2] and bodily hallucinations [18]. Finally, it was
also shown that individuals who reported having near-death exper ience had more
significant epileptiform elec troencephalogram (EEG) activity compared to control
patients [19].
An integrative model of these organic theories has proposed that brain stress
caused by traumatic events leads to the release of neurotransmitters producing
effects such as analgesia, euphoria and detachment. These effects combine with the
effect of decreases in oxygen tension to produce epileptiform discharges in the hip-
964 A. Vanhaudenhuyse, M. Thonnard, and S. Laureys
XXV
pocampus and amygdala, possibly leading to hallucinations and life review. After-
discharges, propagating through limbic connections to other brain areas, could pro-
duce further hallucinations and the sensation of seeing a brilliant light [20]. Finally ,
there exists no EEG data about brain functions in the critical clinical period that is
assumed to be associated with near-death experiences. Indeed, loss of consciousness
was diagnosed only by electrocardiogram (EKG) examinations, independent of neu-
rological or EEG records.
Clinical Studies
Parnia et al. [21] prospectively studied cardiac arrest patients over a one year
period. Of the 63 survivors interviewed within a week of cardiac arrest, 7 (11 %)
reported memories of their period of unconsciousness, 4 of whom (6 %) had near-
death experiences according to the Greyson Near-death Experience scale [8]. All
patients reported that the near-death experience was pleasant. Due to the small
number of patients, it was not possible to draw any clear conclusions regarding pos-
sible causative physiological factors such as hypoxia, hyp e rcarbia, electrolyte distur-
bances, specific cardiac dysrhythmia, carbon dioxide, sodium and potassium ob-
tained from arterial blood gas and peripheral blood, or the administration of drugs
around the period of arrest. Only the partial pressure of oxygen was reported to be
higher in the near-death experience group as compared to non-near-death experi-
ence survivors.
Another prospec tive study was conducted by Van Lommel et al. [22] and involved
344 cardiac arrest survivors. Sixty-two (18 %) patien ts reported a near-dea th experi-
ence, 41 (12 %) of whom reported a core near-death experience experience (i.e.,
scoring 6 or more on the WCEI [7]). No patients reported distressing near-death
experiences. Duration of cardiac arrest, medication, fear of death before cardiac
arrest, and the duration between the near-death experience and the interview were
not rela ted to the occurrence of near-death experiences. However, people younger
than 60 were more likel y to report a near-death experience than older people, as
were those suffering their first myocardial infarction. Mo re vivid near-death experi-
ence (i.e., higher WCEI scores) were reported by patients surviving cardiac arrest
outside the hospital, and were more frequently reported by women and those
reporting being afraid of death before the cardiac arrest. Two and eight years after
the near-death experience, patients were re-interviewed and compared with a con-
trol group (cardiac arrest survivors who did not report a near-death experience).
This longitudinal follow-up showed that near-death experiences produce long-last-
ing effects in terms of increased belief in an afterlife and decreased fear of death,
increased interest in the meaning of ones own life, and increased social awareness
such as showing love and accepting others.
Schwaninger et al. [23] prospectively studied 174 cardiac arrest patients (of whom
119 [68 %] died). Of the remaining 55 patients, 30 (17 %) were interviewed using the
Greyson Near-death Experience scale [8] (25 were excluded due to neurological
impairment or intubation until discharge). Seven patients reported a near-death
experience (13 % of survivors). A 6-month follow-up confirmed previous findings of
long-lasting transformational effects of near-death experiences with regard to per-
sonal understanding of life and self, social attitudes, and changes in social customs
and religious or spiritual beliefs.
Finally, Greyson [24] prospectively studied 1595 cardiac sur vivors patients, of
whom 27 (2 %) scored 7 or more points on the Greyson Near-death Experience scale
Towards a Neuro-scientific Explanation of Near-death Experiences? 965
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Table 3. Frequency of near-death experiences in cardiac arrest survivors according to the Weighted C ore
Experience Index (WCEI) or the Greyson Near-death Experience Scale [8].
Authors Scale Total number
of patients
Number of patients having
reported near-death experience (%)
Van Lommel et al. (2001) [22] WCEI 344 41 (12 %)
Parnia et al. (2001) [21] Greyson scale 63 4 (6 %)
Schwaninger et al. (2002) [23] Greyson scale 55 7 (13 %)
Greyson (2003) [24] Greyson scale 1595 27 (2 %)
[8]. Near-death experiencers, comprising 2 % of the entire sample, included 10 % of
patients admitted with cardiac arrest, 1 % of those with myocardial infarction, 1 %
of those with unstable angina, and 1 % of those with other cardiac diagnoses.
Patients who reported a near-death experience were younger, more likely to have
lost consciousness, and more likely to report prior so-called “paranormal experi-
ences but not extrasensory perceptions. Religious beliefs prior to the near-death
experience were not related to the frequency of near-death experiences.
In summary, these studies report incidence rates of near-death experiences in
survivors from cardiac arrest ranging from 2 % to 13 % (
Table 3)andshowahigher
incidence in younger patients. The reported experiences suggest tha t features of
near-death experiences are similar among patients (
Tables 1 and 2).
Out-of-body Experiences
Definition
One of the princip al components of near-death experiences is the out-of-body expe-
rience. Out-of-body experience is defined by the presence of three phenomenologi-
cal characteristics: Disembodiment (i.e., location of the self outside one’s body); the
impression of seeing the world from an eleva t ed and distanced visuo-spatial per-
spective; and the impression of seeing ones own body from this perspective (i.e.,
autoscopy) [25] (
Fig. 2,upperpart).Understandinghowthebraingeneratesthe
abnormal self during out-of-body experiences is particularly interesting since out-
of-body experiences are not only found in clinical populations, but also appear in
approximately 10 % of the healthy population [25, 26]. The out-of-body experience
can also be present in various situations, such as psychiatric disorders, drug abuse,
general anesthesia, and sleep.
Neuroanatomical Correlates
There is increasing evidence showing that out-of-body experiences may result from
adeficientmultisensoryintegrationatthetemporo-parietaljunctionarea[2,18,27].
Focal electrical stimulation of this area in a patient who was undergoing evaluation
for epilepsy treatment induced repeated out-of-body experiences and illusory trans-
formations of the patient’s arm and legs [ 1 8 ] . In a study of six neurological patients
(with epilepsy or migraine), Blanke et al. [2] showed that out-of-body experiences
were always described from one visuo-spatial perspective, which was localized in a
second body outside the physical body (e.g., inverted by 180° with respect to the
extra personal visual space and the habitual physical body position). All patients
966 A. Vanhaudenhuyse, M. Thonnard, and S. Laureys
XXV
showed immediate self-recognition and th e i r lesion overlap was centered on t h e
temporo-parietal junction, including the anterior part of the angular gyrus and the
posterior temporal gyrus. De Ridder et al. [27] induced an out-of-body experience
in a 63-year-old man with an implanted electrode over the right temporo-parietal
junction. Using a positron emission tomography (PET) scan, these authors also
showed that the out-of-body experience was related to increased activity in the right
temporo-parietal junction, superior temporal, and right precuneal cortices. They
suggested that the induced altered spatial self-recognition was mediated by the tem-
poro-parietal junction, which is involved in vestibular-somatosensory integration of
body orientation in space. Similarly, Blanke [28] suggested a model to explain out-
of-body experiences proposing that “ out-of-body experiences are related to a disin-
tegration within personal space (multisensory dysfunction) and disintegration
between personal space (vestibular) and extrapersonal (visual) due to interference
with the temporo-parietal junction. In these models, the experience of seeing ones
body in a position that does not coincide with the felt position of ones body is
assumed to be related to temporo-parietal junction dysfunction (
Fig. 2,lowerpart).
Conclusion
Near-death experiences and out-of-body experiences remain fascinating phenomena
which are abundant in popular beliefs, mythology, and spiritual experiences of many
ancient and modern societies. Clinical studies suggest that characteristics of near-
death experiences are culturally invariant and can be investigated neuroscientific-
ally. The frequency of near-death experiences in cardiac arrest survivors varies from
2 to 13 % and near-death experiences seem to be more common in younger patients.
Longitudinal studies have shown profound long-lasting transformational effects of
near-death experiences with regard to personal understanding of life and self, social
attitudes, and changes in social customs and religious or spiritual beliefs. One of the
principal components of near-death experiences is the out-of-body experience that
is associated with partial impairments in consciousness and disturbed own body
processing. Recent studies employing deep brain stimulation and neuroimaging
have demonstrated that out-of-body experiences result from a deficient multisen-
sory integration at the temporo-parietal junction. Ongoing studies aim to further
identify the functional neuroanatomy of near-death experiences by means of stan-
dardized EEG recordings.
Acknowledgements: This research was funded by the Belgian National Funds for
Scientific Research (FNRS), the European Commission, the James McDonnell Foun-
dation, the Mind Science Foundation, the French Speaking Community Concerted
Research Action (ARC-06/11 340), the Fondation M´edicale Reine Elisabeth, and the
University of Li`ege. A.V. was funded by ARC 06/11 340 and S.L. is senior research
associate at the FNRS.
Towards a Neuro-scientific Explanation of Near-death Experiences? 967
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... According to the scale, an individual with a NDE scale score of 7 or higher on the maximum of 32 qualifies as a NDE experiencer [16]. The Greyson NDE scale is the most widely used tool to standardize the identification of NDErs in research literature [18]. According to a recent retrospective collection of data obtained from 354 individuals with selfreported NDEs over a 7-year period using the NDE scale, the top three most reported features were (1) a feeling of peace or pleasantness (92%), (2) a feeling of detachment from the body (77%), and (3) seeing or feeling surrounded by a brilliant light (74%) [19]. ...
... However, from the 2% of the patients' sample with explicit recall of "seeing" and "hearing" actual events related to their resuscitation, none of them could report seeing the targets. Like we will discuss in the next sections, neuroscientifically, it seems more probable that NDE features are the result of specific interactions between psychological and neurological mechanisms precipitated by the context of occurrence and an altered state of consciousness [18,64]. ...
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The notion that death represents a passing to an afterlife, where we are reunited with loved ones and live eternally in a utopian paradise, is common in the anecdotal reports of people who have encountered a “near-death experience” (NDE). These experiences are usually portrayed as being extremely pleasant including features such as a feeling of peacefulness, the vision of a dark tunnel leading to a brilliant light, the sensation of leaving the body, or the experience of a life review. NDEs are increasingly being reported as a clearly identifiable physiological and psychological reality of clinical and scientific significance. The definition and causes of the phenomenon as well as the identification of NDE experiencers are still matters of debate. The phenomenon has been thoroughly portrayed by the media, but the science of NDEs is rather recent and still lacking of rigorous experimental data and reproducible controlled experiments. It seems that the most appropriate theories to explain the phenomenon tend to integrate both psychological and neurobiological mechanisms. The paradoxical dissociation between the richness and intensity of the memory, probably occurring during a moment of brain dysfunction, offers a unique opportunity to better understand the neural correlates of consciousness. In this chapter, we will attempt to describe NDEs and the methods to identify them. We will also briefly discuss the NDE experiencers’ characteristics. We will then address the main current explicative models and the science of NDEs.
... 315-316) defines NDEs as "profound psychological events with transcendental and mystical elements, typically occurring to individuals close to death or in situations of intense physical or emotional danger." Prototypical features of NDE are out-ofbody experiences (OBE), experiencing a panoramic life review, feeling of peace and quiet, seeing a dark tunnel, experiencing a bright light (Vanhaudenhuyse et al., 2009;Martial et al., 2020). While some scholars believe that it is possible to explain NDEs in psychological or neurobiological terms (see for example Mobbs and Watt, 2011;Martial et al., 2020), some other scholars argue that physicalists theories of the mind cannot explain how people can experience the vivid and complex thoughts of the NDE, given that brain activity is seemingly absent (see for example Haesler and Beauregard, 2013;van Lommel, 2013). ...
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What distinguishes conscious information processing from other kinds of information processing is its phenomenal aspect (PAC), the-what-it-is-like for an agent to experience something. The PAC supplies the agent with a sense of self, and informs the agent on how its self is affected by the agent’s own operations. The PAC originates from the activity that attention performs to detect the state of what I define “the self” (S). S is centered and develops on a hierarchy of innate and acquired values, and is primarily expressed via the central and peripheral nervous systems; it maps the agent’s body and cognitive capacities, and its interactions with the environment. The detection of the state of S by attention modulates the energy level of the organ of attention (OA), i.e., the neural substrate that underpins attention. This modulation generates the PAC. The PAC can be qualified according to five dimensions: qualitative, quantitative, hedonic, temporal and spatial. Each dimension can be traced back to a specific feature of the modulation of the energy level of the OA.
... Near-death experience (NDE) has been reported in situations where the brain transitions toward death. Subjective descriptions of this phenomenon are described as intense and surreal and include a panoramic life review with memory recalls, transcendental and out-of-body experiences with dreaming, hallucinations and a meditative state (Vanhaudenhuyse et al., 2007). ...
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The neurophysiological footprint of brain activity after cardiac arrest and during near-death experience (NDE) is not well understood. Although a hypoactive state of brain activity has been assumed, experimental animal studies have shown increased activity after cardiac arrest, particularly in the gamma-band, resulting from hypercapnia prior to and cessation of cerebral blood flow after cardiac arrest. No study has yet investigated this matter in humans. Here, we present continuous electroencephalography (EEG) recording from a dying human brain, obtained from an 87-year-old patient undergoing cardiac arrest after traumatic subdural hematoma. An increase of absolute power in gamma activity in the narrow and broad bands and a decrease in theta power is seen after suppression of bilateral hemispheric responses. After cardiac arrest, delta, beta, alpha and gamma power were decreased but a higher percentage of relative gamma power was observed when compared to the interictal interval. Cross-frequency coupling revealed modulation of left-hemispheric gamma activity by alpha and theta rhythms across all windows, even after cessation of cerebral blood flow. The strongest coupling is observed for narrow-and broad-band gamma activity by the alpha waves during left-sided suppression and after cardiac arrest. Albeit the influence of neuronal injury and swelling, our data provide the first evidence from the dying human brain in a non-experimental, real-life acute care clinical setting and advocate that the human brain may possess the capability to generate coordinated activity during the near-death period.
... Near-Death Experiences (NDEs) are increasingly being reported as a clearly identifiable physiological and psychological reality of clinical and scientific significance [1]. NDEs can be defined as a set of mental events including highly emotional, self-related, mystical and spiritual aspects occurring in an altered state of consciousness classically in the context of a life-threatening condition (e.g., cardiac arrest, trauma, perioperative complications, neardrowning or asphyxia, electrocution, attempted suicide) [2][3][4]. ...
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The notion that death represents a passing to an afterlife, where we are reunited with loved ones and live eternally in a utopian paradise, is common in the reports of people who have encountered a “Near-Death Experience” (NDE). NDEs are thoroughly portrayed by the media but empirical studies are rather recent. The definition of the phenomenon as well as the identification of NDE experiencers is still a matter of debate. To date, NDEs’ identification and description in studies have mostly derived from answered items in questionnaires. However, questionnaires’ content could be restricting and subject to personal interpretation. We believe that in addition to their use, user-independent statistical text examination of freely expressed NDEs narratives is of prior importance to help capture the phenomenology of such a subjective and complex phenomenon. Towards that aim, we included 158 participants with a firsthand retrospective narrative of their self-reported NDE that we analyzed using an automated text-mining method. The output revealed the top words expressed by experiencers. In a second step, a hierarchical clustering analysis was conducted to visualize the relationships between these words. It revealed three main clusters of features: visual perceptions, emotions and spatial components. We believe the user-independent and data-driven text mining approach used in this study is promising by contributing to the building a rigorous description and definition of NDEs.
... As reported above, 10 of 16 NDE items were scored significantly higher under DMT than placebo. Items that did not survive multiple comparison correction (experiences of extrasensory perception, life-review, precognition of future events, increased speed of thoughts and seeing deceased people/relatives) are also items that are less commonly endorsed in 'actual' NDEs (Schwaninger et al., 2002;Greyson, 2003;Vanhaudenhuyse et al., 2009). The Affective subscale of the NDE scale was scored particularly highly under DMT, and emotion is also a prominent feature of actual NDEs (Greyson, 1983(Greyson, , 2003Schwaninger et al., 2002;Martial et al., 2017). ...
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Near-death experiences (NDEs) are complex subjective experiences, which have been previously associated with the psychedelic experience and more specifically with the experience induced by the potent serotonergic, N,N-Dimethyltryptamine (DMT). Potential similarities between both subjective states have been noted previously, including the subjective feeling of transcending one's body and entering an alternative realm, perceiving and communicating with sentient 'entities' and themes related to death and dying. In this within-subjects placebo-controled study we aimed to test the similarities between the DMT state and NDEs, by administering DMT and placebo to 13 healthy participants, who then completed a validated and widely used measure of NDEs. Results revealed significant increases in phenomenological features associated with the NDE, following DMT administration compared to placebo. Also, we found significant relationships between the NDE scores and DMT-induced ego-dissolution and mystical-type experiences, as well as a significant association between NDE scores and baseline trait 'absorption' and delusional ideation measured at baseline. Furthermore, we found a significant overlap in nearly all of the NDE phenomenological features when comparing DMT-induced NDEs with a matched group of 'actual' NDE experiencers. These results reveal a striking similarity between these states that warrants further investigation.
... Neuroscientifically, the current theories explaining a NDE and its core features hypothesize that they occur during an altered state of consciousness, accompanied by specific brain activities resulting from the interactions between neuropsychophysiological mechanisms (Vanhaudenhuyse et al., 2009). ...
Thesis
When facing a life-threatening situation –or a situation perceived as such, some people will report having lived various phenomenological experiences (e.g., out-of-body experiences, encountering deceased relatives) that are intriguing by their extra-ordinary aspect. These distinct perceptual experiences are commonly referred to as the phenomenon of “near-death experience” (NDE). To date, the scientific literature devoted to this phenomenon contains a predominance of opinion and review articles, while there is a lack of empirical investigations that try to understand its rich phenomenology. Through four data-driven studies, we had two main objectives: (1) to better characterize the memory of NDE, as well as (2) to better define the cognitive profile of their experiencers (i.e., people who have experienced a NDE).
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