Neuroscientist Jimo Borjigin was surprised to learn that we know "almost nothing" about what happens in the brain at the moment of death, even though "death is an essential part of life."
She found out about ten years ago "by chance".
"We did experiments on rats and monitored their secretion of neurochemical substances," she tells BBC Mundo.
Two died suddenly.
This allowed her to watch their brains die.
"One of the rats secreted serotonin in large quantities. Was that rat hallucinating?” she wondered.
"Serotonin is associated with hallucinations," explains Borjidzin.
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Such a storm of serotonin - the hormone that regulates mood - fueled her curiosity.
"So I started researching the literature over the weekend, believing there must be an explanation.
"I was surprised to realize that we know so little about death."
Since then, Dr. Borjidzin, an associate professor of molecular and integrative physiology and neurology at the University of Michigan, has dedicated herself to studying what happens in the brain in the final moments of life.
And what she discovered is contrary to previous assumptions, she says.
Definition of death
She explains that for a long time, clinical death has been declared after a prolonged absence of a pulse after cardiac arrest.
Here, the attention is focused on the heart: "It is called acute cardiac arrest, but it is not called brain arrest."
"The scientific understanding is that the brain looks like it doesn't work because it doesn't give an answer: these people can't speak, they can't stand, they can't sit".
The brain needs a lot of oxygen to function.
If the heart does not pump blood, oxygen does not reach the brain.
"So all visible indicators indicate that the brain is no longer working, or at least hypoactive, not hyperactive," she explains.
However, her team's research suggests otherwise.
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Brain in 'hyperdrive'
During research in rats in 2013, intense activity of several neurotransmitters was observed after the animals' hearts stopped.
"Serotonin levels increased 60-fold, and dopamine, the feel-good chemical, increased an incredible 40 to 60 times.
"And the level of noradrenaline (norepinephrine), which promotes alertness, increased about 100 times".
She says such high levels are impossible when the animal is alive.
In 2015, her team published another study on the brains of dying rats.
"In both studies, in 100 percent of the animals, a large functional activation of the brain was recorded," she says.
"The brain is in hyperdrive, it is in a hyperactive state".
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Gamma waves
The team is 2023, published part research with four patients in a coma and on artificial life support, on which electroencephalographic electrodes are placed that record brain activity.
These patients were dying.
Doctors and families gathered and "believing that there was no help for them, they gave up the fight".
With the relative's permission, they were disconnected from the ventilators that kept them alive.
The researchers then found that the brains of the two patients were highly active, indicating cognitive function.
Gamma waves were also discovered - the fastest brain waves.
Gamma waves play a role in complex information processing and memory.
In one patient, high activity was recorded in the temporal (temporal) lobe on both sides of the brain.
Dr. Borjidzin points out that it is known that the area of the right junction of the temporal and parietal lobes is very important for empathy.
"Many patients who survive acute cardiac arrest (and have) a near-death experience say that they have become better people and have compassion for others."
A near death experience
Some people who have a near-death experience say they can see their life flash before their eyes or remember the most important moments.
Many say that they saw a bright light, and others that they had an out-of-body experience and that they observed everything "from above".
Could the hyperactivity of the brain that Dr. Borjidzin observed in her research explain why some people have such intense near-death experiences?
"Yes, I think it can," she says.
"At least 20 to 25 percent of people who survive acute cardiac arrest report seeing a white light, seeing something, so that indicates that the visual cortex of the brain is activated."
In the case of two patients who showed high brain activity after they were taken off the ventilator, the researcher says their visual cortices (which support conscious vision) showed intense activation "potentially related to this visual experience."
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New knowledge
Dr. Borjidzin admits that she has conducted very few human studies and that more research is needed on what happens in the brain at the moment of death.
However, after more than 10 years of research in this area, one thing is clear to her: "I think that during acute cardiac arrest the brain is not hypoactive, but hyperactive."
But what happens to the brain when it realizes it is not getting oxygen?
"We're trying to figure it out. There is very little literature on this. You really don't know anything," she says.
He mentions hibernation and says he has the following assumption - as animals, which include rats and humans, we have an endogenous mechanism to combat the lack of oxygen.
"Until now, the brain was thought to be a passive observer during acute cardiac arrest: when the heart stops, the brain simply dies.
"That's the current understanding: the brain can't deal with it and it just dies."
But she claims that we don't know if that's actually true.
He believes that the brain is not surrendered lightly.
As in other crisis situations, the brain struggles.
"Hibernation is one of the very good examples that I believe (shows) that the brain is actually equipped with a mechanism to survive this temptation or lack of oxygen.
"But that needs to be investigated."
Much remains to be discovered
Borjidzin believes that what she and her team have discovered during their research is only the tip of a huge iceberg and that there is much more to discover.
"I believe that the brain has endogenous mechanisms to cope with hypoxia (when there is no oxygen) that we do not understand.
"Our knowledge is so sketchy about these amazing, personal experiences people have during acute cardiac arrest, and our data shows that this experience is due to increased brain activity.
"Now the question arises: why does the dying brain have increased brain activity?
"We have to join forces to understand it, to study it, to investigate it, and to discover it, because because we don't understand the mechanism of death, we may be prematurely declaring the death of millions of people."
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