Neuroscientist Mario Beauregard writes: "Near-death experiences (NDEs) are vivid, realistic, and often deeply life-changing experiences occurring to individuals who have been psychologically or physiologically close to death. A clear memory of the experience, enhanced mental activity, and a conviction that the experience is more real than ordinary waking consciousness are core features of NDEs (Greyson, 2011).
"NDEs are frequently evoked by cardiac arrest. When the heart stops, breathing stops as well, and blood flow and oxygen uptake in the brain are rapidly interrupted; the EEG becomes isoelectric (flat-line) within 10-20 seconds, and brainstem reflexes vanish (Clute & Levy, 1990); the individual having the cardiac arrest is then considered to be clinically dead. Because the brain structures supporting conscious experience and higher mental functions (e.g. perception, memory, and awareness) are dramatically impaired, cardiac arrest survivors are not expected to have clear and lucid mental experiences during the cardiac arrest period that will be remembered.
"Nonetheless, studies carried out in the United Kingdom (Parnia et al., 2001), the Netherlands (van Lommel et al., 2001), Belgium (Lallier et al., 2015), and the United States (Schwaninger et al., 2002; Greyson, 2003) have revealed that about 15 percent of cardiac arrest survivors do report some recollection from the time when they were clinically dead. In these studies, more than 100 cases of full-blown NDEs were reported. It is noteworthy that while they are clinically dead, NDErs sometimes report perceptions that coincide with reality.
"Advocates of materialist theories of the mind object that even if the EEG is isoelectric, there may be some residual brain activity that goes undetected because of the limitations of scalp-EEG technology. This is possible, given that scalp-EEG technology measures mostly the activity of large populations of cortical neurons. However, the brain activity agreed upon by contemporary neuroscientists as the necessary condition of conscious experience is well detected via current EEG technology, and is clearly abolished by cardiac arrest (Greyson, 2011).
"Proponents of materialist theories of the mind also argue that NDEs do not occur during the actual episodes of brain insult, but just before or just after the insult, when the brain is more or less functional (Saavedra-Aguilar & Gómez-Jeria, 1989; Blackmore, 1993; Woerlee, 2004). The problem with this interpretation is that unconsciousness generated by cardiac arrest leaves patients amnesic and confused for events occurring immediately before and after such episodes (Aminoff et al., 1988; Parnia & Fenwick, 2002; van Lommel et al., 2001)."
Mario Beauregard, “The Next Great Scientific Revolution,”
in Beauregard, Mario; Dyer, Natalie; Woollacott, Marjorie. Expanding Science:
Visions of a Postmaterialist Paradigm, Vol. 2, Postmaterialist Sciences
Series (pp. 21-23). The Academy for the Advancement of Postmaterialist Sciences
(AAPS), 2020. Kindle Edition.
Aminoff, M. J., Scheinman, M. M.,
Griffin, J. C., & Herre, J. M. (1988). Electrocerebral accompaniments of
syncope associated with malignant ventricular arrhythmias. Annals of Internal
Medicine, 108, 791–796.
Blackmore, S.J. (1993). Dying to Live:
Science and the Near- Death Experience. London: Grafton.
Clute, H. L. & Levy, W. J. (1990).
Electroencephalographic changes during brief cardiac arrest in humans.
Anesthesiology, 73 (5), 821–825.
Greyson, B. (2003). Incidence and
correlates of near-death experiences in a cardiac care unit. General Hospital
Psychiatry, 25 (4), 269-276.
Greyson, B. (2011). Implications of
near-death experiences for a postmaterialist psychology. Psychology of Religion
and Spirituality, 2 (1), 37-45.
Lallier, F., Velly, G., & Leon, A.
(2015). Near-death experiences in survivors of cardiac arrest: a study about
demographic, medical, pharmacological and psychological context. Critical Care,
19 (Suppl 1), P421.
Parnia, S., & Fenwick, P. (2002).
Near death experiences in cardiac arrest. Resuscitation, 52, 5–11.
Saavedra-Aguilar, J. C. &
Gómez-Jeria, J. S. (1989). A neurobiological model for near-death experiences.
Journal of Near-Death Studies, 7 (4), 205-222.
van Lommel, P., van Wees, R., Meyers, V. & Elfferich,
I. (2001). Near-death experience in survivors of cardiac arrest: A prospective
study in the Netherlands. Lancet, 358 (9298), 2039–2045.
Woerlee, G. M. (2004). Cardiac arrest and near-death experiences. Journal of Near-Death Studies, 22, 235-249.