Doctors have found that the brain can stay active 30 seconds after cardiac arrest (here, brain waves from a rat by EEG). This supports the thesis of a state of consciousness during which all kinds of hallucinations are possible.
Thus, behind the light tunnels and the possible hallucinations, the disturbances of the limbic system (amygdala, hippocampus ...) and of the prefrontal and temporal cortices have emerged as serious potential responsible, given the involvement of these brain regions in the memory, emotions or behavior. Other possible causes: the secretions of neurotransmitters (dopamine, serotonin ...) and other endorphins and opioids, chaotic when the body is fighting its final battle, or the modification of blood gases (lack of oxygen and / or increase in carbon). Explanations that remain to be proven, however.
If its biological origin remains uncertain, research nonetheless sheds light on the indisputable reality of the experience for those who live it. At the end of 2014, Sam Parnia, of the State University of New York, published the largest panel of testimonies identified in the hospital environment. A recognized specialist in the field, the doctor was himself surprised. While we generally speak of 10 to 20% of people affected by an NDE, he discovers that 39% of the patients questioned describe a "sensation of consciousness", but without always keeping "explicit memory" of it. It also brings to light the dark side of the experience: feeling of fear, of persecution ...
Those who "come back"
For people who have "returned", the feeling is strong and very real. Several works, including those carried out in 2013 by psychologist Marie Thonnard, at the University of Liège, conclude that "the memories of this experience cannot be seen as those of purely imaginary events.
On the contrary, their physiological origin could lead them to be truly perceived, although not really experienced. "
What is certain is that, even when dying, the brain is active. University of Michigan neurologist Jimo Borjigin has shown in rats that they can remain very active within 30 seconds of cardiac arrest.
Thus making plausible the idea that near-death experiences take place just before or just after this extreme episode.
Not to mention that undetectable brain activity does not mean absent. So Sam Parnia notes in his latest study that in some cases "consciousness seems to subsist for three minutes without a heartbeat". The hypothesis is bold and the doctor says he needs more cases to confirm it.
Either way, specialists all agree on one point: the subjects of a near-death experience are indeed experiencing something extraordinary while they are on the verge of death.