Does life really pass before our eyes when we die?

Guillaume Thierry, professor of cognitive neuroscience at the University of Bangor, wants to know how long humans are conscious after death.

The first time I got past the horror of the concept of death and wondered what the experience of death might be like, I was around 15 years old. I had just discovered the horrible aspects of the French Revolution and how the heads were carefully cut from the body by a guillotine.

The words that I remember to this day are the last of Georges Danton, on April 5, 1794, who is said to have said to his executioner: “Show my head to the people, it is worth seeing. Years later, having become a cognitive neuroscientist, I began to wonder to what extent a brain suddenly separated from the body could still perceive its environment and perhaps think.

Danton wanted his head shown, but could he see or hear people? Was he conscious, even for a brief moment? How did his brain shut down?

On June 14, 2021, these questions were violently reminded of me. I left for Marseille, France after being called to Avignon by my mother because my brother was in critical condition, days after he was suddenly diagnosed with terminal lung cancer. But when I landed, I was told my brother died four hours ago. An hour later, I found him perfectly still and beautiful, his head slightly turned to the side as if in a deep sleep state. Only he wasn’t breathing and he was cold to the touch.

Though I refused to believe it that day, and for the next few months, my brother’s extraordinarily brilliant and creative spirit had evaporated to remain palpable in the works of art he left behind. him. However, at the last moment that I had the opportunity to pass with his lifeless body in a hospital room, I felt the need to speak to him.

And I did this, despite 25 years of studying the human brain and knowing full well that about six minutes after the heart stops, and the blood supply to the brain is cut off, the brain essentially dies. Then the deterioration reaches a point of no return and central awareness – our ability to feel that we are here and now and to recognize that our thoughts are our own – is lost. Could there be something left of my beloved brother’s spirit to hear my voice and generate thoughts, five hours after his death?

Some science experiments

Experiments have been carried out with the aim of better understanding the testimonies of people who have had a near-death experience. Such an event has been associated with out-of-body experiences, a feeling of deep bliss, a call, seeing a light shining above, but also deep bouts of anxiety or emptiness. and complete silence. One of the main limitations of studies of such experiences is that they focus too much on the nature of the experiences themselves and often neglect the context that precedes them.

Some people, having undergone anesthesia while in good shape or having been involved in a sudden accident resulting in an instantaneous loss of consciousness, have little reason to feel deep anxiety when their brain begins to shut down. On the contrary, someone with a prolonged history of serious illness might be more likely to be abused.

It’s not easy to get permission to study what’s really going on in the brain during our last moments of life. But a recent paper looked at electrical brain activity in an 87-year-old man who suffered a head injury in a fall as he died from a series of seizures and strokes. ‘cardiac arrest. Although this is the first publication of such data collected during the transition from life to death, the article is highly speculative regarding the possible “mind experiences” that accompany the transition to the death.

Researchers have found that certain brain waves, called alpha and gamma, change patterns even after blood stops flowing to the brain. “Given that cross-coupling between alpha and gamma activity is implicated in cognitive processes and memory recall in healthy subjects, it is intriguing to speculate that such activity could support last-life recall. which can take place in the state of imminent death. ,” they write.

However, such coupling isn’t uncommon in the healthy brain — and doesn’t necessarily mean life flashes before our eyes. Furthermore, the study did not answer my basic question: how long does it take after the supply of oxygen to the brain stops for essential neural activity to disappear? The study only reported brain activity recorded over a period of about 15 minutes, including a few minutes after death.

In rats, experiments have established that after a few seconds, consciousness is lost. And after 40 seconds, the vast majority of neural activity is gone. Some studies have also shown that this brain shutdown is accompanied by a release of serotonin, a chemical associated with excitement and feelings of happiness.

But what about us? While humans can be revived after six, seven, eight or even ten minutes in extreme cases, it could theoretically be hours before their brains completely shut down.

I’ve come across a number of theories trying to explain why life would flash before someone’s eyes as the brain prepares to die. Perhaps this is a completely artificial effect associated with the sudden increase in neural activity when the brain begins to shut down. It may be a last resort, a defense mechanism of the body trying to overcome impending death. Or maybe it’s a deep-rooted, genetically programmed reflex that keeps our minds “occupied” as the most distressing event of our entire lives is clearly unfolding.

My hypothesis is somewhat different. Perhaps our most essential existential motivation is to understand the meaning of our own existence. If so, then seeing his life flash before his eyes could be our last attempt – however desperate – to find an answer, necessarily expedited because we are running out of time.

And whether or not we succeed or have the illusion that we have, it must result in absolute mental bliss. I hope that future research in the field, with longer measurements of neural activity after death, perhaps even brain imaging, will support this idea – whether it lasts minutes or hours, for the good of my brother, and that of all of us.

Guillaume Thierry, Professor of Cognitive Neuroscience, Bangor University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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