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.   

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. 

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.

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.”

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.