A white light at the end of the tunnel? This is what happens when we die.

It's the obsession of poets. "Does dust return to dust? / Does the soul return to heaven? / Is everything vile matter, / rot and mud?" Gustavo Adolfo Bécquer wondered. Others recreate the unknown dimension that lies beyond: "Death will come and tear out my eyes: / I will then see another firmament," Joan Vinyoli predicted, while Sylvia Plath described: "Something else / drags me through the air / – thighs, hair; / scales." They also link it to memories: "When the night is my memory. My memory will be the night," said Alejandra Pizarnik.

Death is the thorn in the side of human beings, who since ancient times have lamented impermanence and sought immortality. They have also done so through cinema. Who doesn't remember Patrick Swayze leaving his body and seeing himself in the arms of a very young Demi Moore in the film Ghost (1990), while refusing to be carried away by little white lights toward the beyond? Light, interactions with other entities, and memories of life," explains UOC neuroscience professor Diego Emilia Redolar. He does so with several studies on these experiences in hand, always with patients who survived cardiac arrest. The first one, made in the Netherlands and published in 2001 in The Lancet, included 344 patients, of whom 18% described having experienced it.

One of the stories collected in the research is particularly disconcerting. A nurse explains that, during a night shift, an ambulance brought a cyanotic and deeply comatose man to the coronary care unit, and she removed his dentures in order to intubate him. A week later, she met the now-stable patient again, who said, "This nurse knows where my teeth are. You were there when I was taken to the hospital, and you took the dentures out of my mouth and put them on that cart." The man explained "that he had seen himself lying in bed and that he had seen from above how the doctors and nurses were working to resuscitate him."

Another significant study in this regard is AWARE I and II by New York researcher Sam Parnia, the results of which were published in a scientific journal specializing in cardiopulmonary resuscitation and cardiac arrest. Of the 140 survivors of the first study, 9% said they had had this type of experience and 46% said they had a flashback while suffering from cardiac arrest. The second It was a prospective study of 25 centers that only included 28 survivors interviewed, of whom 21.4% reported an experience of this type.

Burst of activity

Far from having paranormal motivations, it seems that so-called near-death experiences could have a scientific explanation. Thus, they appear to be caused by a transient increase in the brain's coordinated gamma activity, which is what we experience when we dream, remember, or concentrate, up to 30 seconds after cardiac arrest. This is suggested by several studies, the most consistent of which comes from the University of Michigan, where a team of scientists has verified this with mice, as published in the journal PNAS in 2013, but also with humans in a research in the same publication in 2022, in which two of four people in a coma monitored while life support was withdrawn recorded a burst of gamma activity. But, in addition to this type of activity, associated with a conscious state and sensory perception, "there appears to be synchronized activity in a junction between the temporal, occipital, and parietal cortex, which could explain these experiences," says Redolar.

But why might there be this burst of activity at the moment of death? Or, in the words of the UOC neuroscientist: "How can the gamma increase rapidly just before all the electroencephalographic waves collapse?" The answer is far from clear. It is unknown whether it responds to an evolutionary function or a consequence of the same crisis caused by the loss of oxygen, admits Redolar. Among the possible explanations we find that "the dying brain is in a state of competition between two opposing forces, the decomposition of the brain network and homeostasis [or balance], which struggles to maintain stability" and this could cause the elevated brain activity due to the lack of oxygen to "interact only through the surviving connections."

"Anything can happen to a brain that is suffering," considers Carles Gaig, a neurologist at Hospital Clínic and a specialist in brain death, who hopes for further research to reproduce these results. For him, these are speculations because "these gamma frequencies have been linked to a state of consciousness, but it's difficult to know if this is really the case and what it means in the context of these seriously ill people." Gaig recalls the complexity of this organ, but also the need to understand that it is a creator of perceptions: "If a tree falls in the middle of the forest, and there is no brain to hear the noise, there is no noise. All reality is a construction of our brain." Therefore, he believes that "drawing conclusions about the existence of a superconsciousness" from this brain activity at the moment of death "corresponds more to a wish than a reality."

This brings us to the great problem of neuroscience: consciousness. For Redolar, who has written The blind woman who could read with her tongue (Grijalbo), this is the main obstacle in research on the end of life: "We are beginning to understand how memory works, but we don't really know how this awareness of ourselves is sustained. What neuronal correlate does it have? Is it in some structure? We can transplant a heart, but we can't transplant a brain because we don't have the tools. If only we had the tools."

Beyond the brain

Whether or not life happens before our eyes at the moment of death is a mystery, but the biochemical and physical changes the body undergoes are not. And these "depend on age, the cause of death, external factors such as weather, and whether the death is natural or violent," explains forensic pathologist Narcís Bardalet. We take as an example a case from the beginning of his career, which includes nearly 10,000 autopsies: the body of a woman is found in the river in Estella, Navarra, and Bardalet analyzes her condition at the time of the body's removal. "This is a woman with a relatively advanced state of putrefaction, who is emphysematous, who has characteristics of a denial, who has injuries to her hands and legs," he explains in the series. The coroner, which can be seen on 3cat and which covers her career, also recently captured by Clàudia Pujol in The most shocking cases of forensic scientist Narcís Bardalet (Now Books). What signs can help you determine the time and cause of death? Among others, the rigidity of bodies in the first 48 hours; bruises caused by the gravity of the blood (which do not appear if it is a death in an aqueous environment); a blue-green stain on the abdomen, which causes it to swell from putrefaction after 48 hours; or, later, the appearance of blisters from decomposition, lists this forensic expert.

This is how our bodies transform when we reach the end of life, but how do cells, the most basic components, disintegrate? "Cell death generally occurs when there is not enough oxygen or nutrients," explains Mireia Ortega, a science communicator and doctor in biomedicine. Then molecular changes are triggered, calcium increases, and autolysis occurs, through which "the cells release enzymes that cause their decomposition." Next, it's the bacteria's turn. First, those that make up our microbiota and are hosted by our bodies, and then external microorganisms. In short, as Ortega says, "your body eats itself on a microscopic scale."