Near-death Experiences Under Scrutiny
The secret of the bizarre mental experiences reported by some people returning from the brink of death may lie in the chemistry of the blood, or response of the body’s systems to sudden changes in the setup for their routine operation.
Separate studies by an American professor of neurology and a team of Slovenian researchers on people who narrowly survived heart attacks have shown that such mental experiences like “life streaming like a movie”, “great bliss”, “conversations with sublime persons”, “acquaintances, including dead ones assembling at the bedside” may be triggered by such physiological phenomena as reduced blood flow to the brain, retinal collapse, REM sleep or raised carbon dioxide levels in blood.
Near-death experiences are phenomena often reported by people who returned from the brink of death or were resusciated after suffering heart attacks. According to one definition, these are sensations experienced close to death or in situations of intense physical or emotional stress, involving motifs like transcendence of reality or mystical encounters. These include cognitive components like accelerated thought processes, “the streaming of life in one’s mind like a movie”, emotional ones like feelings of peace and euphoria, or surreal ones like encounters with mystical beings or deceased people.
Body’s physiological responses to traumatic experiences like a heart attack are seen as the source of near-death experiences.
Although theories concerning the mechanisms of near-death experiences are in no short supply, none can sufficiently explain the phenomena by themselves. Physiological theories see near-death experiences as a part of the physiological processes that accompany the process of death. According to this explanation, reported experiences are triggered by such factors as oxygen starvation, raised carbon dioxide levels in the blood, changes in levels of endorphine, serotonine or ketamine, abnormal operation of brain’s temporal lobe or the limbic system associated with emotions.
Psychological theories try to explain near-death experiences with severed connections between the events, dissociation from personality or the activation of memories of birth.
Surreal theories, meanwhile, see these experiences as proofs of life after death or the existence of the soul as an entity separate from the body.
A team of researchers led by Zalika Klemenc-Ketis interviewed 52 patients who had heart attacks outside the hospitals where they were subsequently brought and taken under intensive care. After assurances that their identities would be kept confidential, they were asked whether they had such experiences. The patients were also asked to fill a questionnaire called Greyson Near Death Experiences Scale, designed to reveal the authenticity and intensity of the sensations.
Researchers further collected data on the gender, age, level of education, religious convictions, and the intensity of their fear of death before and after the heart attack and obtained the details of the medication used, the the time it took for their resusciation and blood test results from the hospital records.
The study of the data revealed that 11 patients, or one-fifths of the sample had near-death experiences.
Conclusion of the researchers is that independent of age, gender, conviction, faith, education, fear of death etc., the raised level of carbon dioxide in blood before and during the attack plays the dominant role. The relative deficiency of the potassium level in blood serum was also seen to play a subsidiary role. Another finding is the propensity of people who had these experiences before, to re-live them later.
Researchers say findings can be explained by disruption of brain’s acid-base balance by excess carbon dioxide, which then triggers sensations of bright rays, hallucinations, out-of-body experiences and transcended reality.
According to neurology professor Kevin Nelson of the University of Kentucky who has worked on near-death-experiences for 30 years, these stem from certain effects the approaching death brings to bear on the functioning of the brain and sensory organs.
The American expert stresses the role of a phase of sleep called REM (short for rapid eye movements). This is the part of sleep when we dream most. At this phase, the sleeping individual experiences a state of paralysis except for the eye and heart muscles and the muscles of the diaphragm needed for breathing. This is believed to be an evolutionary adaptation (gained back in time when our hominid ancestors were living on trees) to prevent people from harming themselves as they “act out” their dreams.
Prof. Nelson, thinks some people are more susceptible to a state called REM intrusion, compared to others. In people who enter this state, the paralysis which accompanies the REM phase comes when t hey are awake, and often together with very vivid hallucinations. Having studied 55 people who reported near-death experiences, Professor Nelson has established that 60 percent of them have previously experienced REM intrusion. According to the researcher, instead of passing from REM stage to wakefulness, the brains of people who had near-death experiences blend these two states. And this takes the individual to an area which the professor terms the borderlands of consciousness. “Many people enter this unstable borderland for only a few seconds or minutes before emerging into REM or waking,” the professor says. “In the borderland, paralysis, lights, hallucinations and dreaming can come to us. During a crisis such as a cardiac arrest, the borderland could explain much of what we know as the near-death experience.”
The feeling of experiencing one’s own death stems from the paralysis of the body induced by the REM phase of the sleep.
As for the oft-reported experiences like light, tunnel, spiritual encounters, floating out of the body , Prof. Nelson explains these with reduced blood flow to the brain.
As 20 percent of the blood pumped by the heart normally goes to the brain, if this volume gets reduced to a third, the brain suffers loss of consciousness 10-20 seconds later. Even when this radical drop in the volume of blood flow lasts for hours, the brain avoids damage, but the person can oscillate between conscious and unconscious states during this period. And no matter how long or brief they last, most of the things happening in the brain stem from the reaction to this reduced flow of blood.
As the blood rushes out of the brain, first the retina, which converts images to electric signals at the back of the eye and transfers them to the brain via the optical nerve, fades out just before the loss of consciousness. Because the blackout starts from the rim and moves inward, the characteristic tunnel vision forms. And as for the light at the end of the tunnel, it could be the strong light at the hospital’s emergency ward, the last thing the brain may sense and recognise as it is drained of blood. Alternatively, it could well be a light “produced inside” the brain by the REM system which is known to activate the visual cortex.
As for the reason why people see themselves walking in a tunnel, the secret is the temporoparietal region of the brain (triggering the out-of-body experiences) being next door neighbor to the region responsible for the sense of motion. Normally this region shuts during REM sleep, but sometimes the door is left ajar and as it transits into REM, brain experiences a sense of motion.
Frequently reported of feeling being dead stems from the paralysis of muscles during the REM stage.
Feeling of floating out of the body, meanwhile, is attributed to effects of electric shocks given during heart attacks.
The cause of the feeling of a deep bliss, another common motif of near-death experiences, is the brain’s reward system. The brain prompts the body to excrete chemicals which trigger sensations of relief and satisfaction in cases of acute crises .
- 1. “The effect of carbon dioxide on near-death experiences in out-of-hospital cardiac arrest survivors: a prospective observational study”, Klemenc-Ketis, Z. Vd, 7 April 2010-04-08
- 2. “Carbon dioxide may explain ‘near death experiences’”, BioMedCentral, 7 April 2010
- 3. “Tunnels of light. Meeting with dead loved ones... the truth about near-death experiences”, Mail.on Sunday, 9 May 2011