For neuroscientist Jimo Borjigin it was a surprise: she could not believe that, although “dying is an essential part of life,” we knew “almost nothing” about the dying brain.
This was evident a little more than 10 years ago by pure “accident”.
“We were doing experiments with rats in the laboratory. “We examined his neurochemical secretions after surgery,” he tells BBC Mundo.
Suddenly, 2 of them died. This allowed them to observe the death process of their brains.
“One of the rats showed a massive secretion of serotonin.”
Had that rat been hallucinating? he wondered. “Serotonin is linked to them,” she explains.
Seeing that explosion of the neurotransmitter piqued his interest.
“That weekend, I started researching specialized literature because I believed there would be an explanation. I searched again and again and ended up realizing that we know very little about the process of dying.”
Since then, the associate professor of neurology and molecular and integrative physiology at the University of Michigan has dedicated herself to studying what happens in the human brain when we are dying.
And what he discovered – he assures – goes against what has been assumed.
The definition of death
“I don’t know if you’ve seen a person go into cardiac arrest,” he tells me.
“The most obvious behavior is that he collapses, falls, passes out.”
“You call her by her name and she doesn’t answer, you touch her and she doesn’t respond, she doesn’t move, it’s like she’s dead.”
We need professionals to tell us if the patient is alive. Many times they use electrocardiogram machines to determine this.
“But for a long time, if someone suffers cardiac arrest, the doctor checks their arms or neck and if they don’t find a pulse, it means that the heart is not pumping blood. “That is defined as clinical death.”
In this process, the greatest attention has been paid to the heart, “it is called cardiac arrest, not cerebral arrest.”
“For all of medicine, even for scientific understanding, it seems that the brain is not working because there is no response: the person cannot speak or sit.”
And the brain needs a lot of oxygen to function. If the heart does not pump blood, oxygen does not reach it.
“All surface signals point to the brain becoming underactive,” explains Borjigin.
However, her and her team’s research shows something different.
Neurotransmitters
In a 2013 study with rats, they observed intense activity of several neurotransmitters after the animals’ hearts stopped and their brains stopped receiving oxygen.
“Serotonin increased 60 times; dopamine, which is a feel-good chemical, increased 40 to 60 times; norepinephrine, which makes you very alert, also rose.”
These high levels, he says, “you never see” when the animal is alive.
In 2015, they published another study on the dying brain in rats.
“In both, 100% of the animals showed an intense activation of brain function,” says the expert.
“The brain was in a hyperactive state.”
gamma waves
In 2023, they published research in which they focused on four patients who were in a coma and on life support, and who had electroencephalography electrodes.
“They were dying from different diseases,” says the scientist.
When the doctors and families concluded that “they were beyond any medical procedure that could help them, they decided to let them go.”
With permission from relatives, mechanical ventilators or respirators were removed.
By doing so, the researchers found that in 2 of the patients, high brain activity linked to cognitive functions was recorded.
Gamma waves – the fastest brain waves – were detected, which are involved in complex information processing and memory.
When a patient’s ventilator is disconnected – says the neurology specialist – generalized hypoxia occurs. This is what the lack of oxygen in the blood is called.
Generalized hypoxia is always associated with cardiac arrest, when the heart fails to pump blood.
“Hypoxia seems to be the unifying theme for activating the brain. And as soon as the ventilators were removed, the brains of two of the four patients activated in seconds.”
Specific parts
While in rats scientists had observed global activation and the entire brain was turned on, “in humans, only parts were activated.”
These were areas associated with conscious functions of the brain.
One of them is known as the “posterior cortical hot zone” (posterior cortical hot zone), which is the occipital temporo-parietal junction (TPO), that is, where the temporal, parietal and occipital lobes interconnect.
“It’s the back part of your brain responsible for sensory perception,” he explains.
It has been associated with consciousness and also with dreams and visual hallucinations.
One area that they saw activated is the so-called Wernicke area, linked to language, speaking and listening.
“We showed that the temporal lobe on both sides is the part that is most activated.”
Located near our ears, that section is very important not only for memory storage, but for other cognitive functions.
The professor highlights that the temporoparietal junction (TPJ) on the right side of the brain has been related to the development of empathy.
“In fact, many patients who have survived cardiac arrests and who had near-death experiences (NDEs) say that those experiences changed them for the better, that they feel more empathy.”
When talking about one of the patients in the study, Borjigin believes that if he had survived, he would surely “have reported the same thing, but, of course, we will never know.”
Near-death experiences
Throughout history, many people who have nearly died or even experienced clinical death and survived thanks to resuscitation techniques have reported having had NDEs.
Some spoke of having spent their lives in a flash or to remember key moments; many of having seen an intense light; others of having left their bodies, rising up and seeing what was happening around them.
Can the hyperactive brain that Borjigin has observed in his studies explain why some people have had such intense experiences on the threshold of death?
“I think so,” he replies.
Their 2023 study notes that in a group of people who survived cardiac arrest, at least 20% or 25% reported seeing a light, meaning their visual cortex was activated.
When referring to the two patients in whom high brain activity was observed after being disconnected from the respirators, the researcher explains that their visual cortices showed intense activation, “which possibly correlates with that visual experience.”
“Some patients who survived have even reported hearing what was happening during their surgery or what the paramedics who rescued them said after being in a car accident.”
In reference to the two patients who died, the professor indicates that “the part of the brain responsible for the perception of speech, language, rear hot zoneshe was very active in both.”
“Paradoxical”
That death has long focused on the heart has led to the belief that the brain stops functioning when a person suffers cardiac arrest, Borjigin says.
“But that phenomenon is not consistent with observations of people who have had near-death experiences.”
While there is no behavior that indicates the brain is functioning during cardiac arrest, it cannot be assumed that it is not, he says.
“How is it possible that a person can have extremely emotional, impressive mental experiences, of seeing a light, hearing voices, feeling out of body, floating in the air? “That’s all part of brain function.”
“Because medical professionals think the brain is underactive, there are those who believe that all of this activity must come from outside the body, that it is something extracorporeal.”
“But we didn’t believe in that and in 2013, when we published the first research with animals, we wrote that the idea that these subjective experiences come from outside the body cannot be proven, it is impossible.”
“That’s why, from the beginning, I have firmly believed that they come from the brain, even though it is paradoxical because it is thought that the brain does not work when you suffer cardiac arrest.”
“I am convinced that near-death experiences come from brain activity that occurs before vital signs of the heart and brain cease, not from activity afterward.”
A new understanding
Borjigin acknowledges that his study in humans is very small and that much more research is needed on what happens in the brain when we are dying.
However, after more than ten years focused on this area, there is one thing that is clear:
“The brain, instead of being hypoactive, becomes hyperactive during cardiac arrest.”
“We need to improve our understanding of brain function during a crisis like that.”
In fact, he thinks that this increase in brain activity that he has seen in his studies is part of a survival mode of the brain when it is deprived of oxygen.
But what happens to the brain when it realizes that it is not getting oxygen?
“We are trying to understand that, there is little literature, we don’t know for sure,” he responds.
He tells me about hibernation and tells me that he has a hypothesis: “That animals, including at least rats and humans, have an endogenous mechanism to deal with a lack of oxygen.”
“Until now it is believed that the brain is an innocent bystander of cardiac arrest: when the heart stops, the brain simply dies, the current idea is that the brain cannot deal with it and dies.”
But – he insists – we don’t know.
Survival
Borjigin believes that the brain does not take off its gloves easily. And in other crises, he fights.
“Hibernation is actually one of the best examples of why I think the brain is equipped with the mechanism to survive this ordeal, the lack of oxygen, but that needs to be investigated.”
It asks me to imagine a family that, suddenly, is hit by an economic crisis: the parents lose their jobs and there is no kind of i entry.
“What do they do? They reduce their expenses, they take non-essential things off the list.”
“They use the money they have left only for what allows them to survive.”
Now he thinks that money is oxygen for the brain.
“I think the brain does the same thing. What is its most essential function? It is not the one that allows you to dance, speak, move. Those functions are not essential. The essential thing is to breathe, to let the heart beat.”
“That’s why I think the brain says: ‘I better do something about this crisis that’s coming.’ And it has to conserve that decreasing amount of oxygen that enters your system.”
under an iceberg
Borjigin considers that what he found in his studies is just the tip of a giant iceberg, beneath which there is a lot to discover.
“When I explained my theory to you with the example of a family that has to redefine its financial priorities, it is because I believe that the brain does the same, I believe that it has endogenous mechanisms to deal with hypoxia that we are not understanding.”
“That’s what I mean by something under a huge iceberg that we see on the surface.”
“On the surface, we know that there are people who go into cardiac arrest who have this incredible subjective experience, and our data shows that that experience is due to increased brain activity.”
“But, the question is: why does the dying brain have such intense activity?”
“We need to investigate, discover, understand that because we could be making premature diagnoses of death for millions of people, given that we do not understand the mechanism of death.”
Keep reading:
* Is it real that people, before dying, see their loved ones who have already died?
* Why do some patients improve just before dying?
* The moving phenomenon that occurs in people who are about to die
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