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• Onye dere ya, Margarita Rodríguez
• Ndị mere akụkọ a, BBC News Mundo

Neuroscientist Jimo Borjigin was surprised when she realised that we knew “almost nothing” about what happened in the brain when we die although “dying is an essential part of life”.

The realisation came around a decade ago by “pure accident”.

“We were doing experiments in rats and monitoring their brain neurochemical secretions after surgery,” she tells BBC News Mundo.

Suddenly, two of them died.

That allowed her to observe the death process of their brains.

“One of the rats showed massive secretion of serotonin. Had that rat been hallucinating?” she wondered. “The serotonin is linked to hallucination,” she explains.

Seeing that explosion of serotonin - a mood-regulating chemical - sparked her curiosity.

“So I started to do literature research over the weekend, thinking there must be an explanation. I was surprised to find out that we know so little about the dying process.”

Since then, Dr Borjigin, who is associate professor in molecular and integrative physiology and neurology at the University of Michigan, has dedicated herself to studying what happens in the brain when we are dying.

And what she discovered, she says, goes against what had been assumed.

The definition of death

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She explains that for a long time, if someone had no pulse after a cardiac arrest, they would have been defined as clinically dead.

In this process, the attention is focused on the heart: “It's called a cardiac arrest, but it doesn't say brain arrest.

“The scientific understanding is that the brain looks like it's not functioning because there's no response: these people cannot talk, cannot stand, cannot sit up.”

The brain needs a lot of oxygen to function. If the heart does not pump blood, oxygen does not reach it.

“So all superficial indications are that the brain is no longer functioning, or at least the brain is hypoactive, not hyperactive,” she explains.

However, her team's research shows something different.

Brain in ‘hyperdrive’

In a 2013 study on rats, they observed intense activity in several neurotransmitters after the animals' hearts stopped.

“Serotonin increased 60-fold, and dopamine, which is a chemical that makes you feel good, increased tremendously, like 40- to 60-fold.

“And norepinephrine, which makes you feel very alert, increased about 100-fold.”

She says that it’s impossible to see such high levels when the animal is alive.

In 2015, the team published another study on the brains of dying rats.

“In both cases, 100% of the animals showed massive great functional brain activation,” she says.

“The brain is in hyperdrive, is in a hyperactive state.”

Gamma waves

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In 2023, they published a piece of research in which they focused on four patients who were in a coma and on life support, and fitted with electroencephalography electrodes that scan the activity of the brain.

Those four people were dying. Doctors and families got together and “believed that they were beyond help, so they decided to let them go”.

With permission from relatives, the ventilators keeping them alive were turned off.

The researchers then found that two of the patients had a highly activated brain, which is indicative of cognitive functions.

Gamma waves - the fastest brain waves - were also detected. Gamma waves are involved in complex information processing and memory.

One of the patients had high activity in the temporal lobes on both sides of the brain.

Dr Borjigin points out that the right temporoparietal junction is known to be very important for empathy:

“Many patients who survive cardiac arrest [and have] near-death experiences (NDEs) say that it made them into a better person, that they are able to have empathy towards others.”

Near-death experiences

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Some people who have gone through NDEs say they can see their lives flash before their eyes or remember key moments.

Many say they saw an intense light and others describe having out-of-body experiences and observing the scene from above.

Can the hyperactive brain Dr Borjigin observed in her studies explain why some people have had such intense experiences on the threshold of death?

“Yeah, I think it does,” she says.

“At least 20%-25% of the survivors of cardiac arrest report seeing a white light, seeing something, so that suggests the visual cortex is activated.”

In the case of the two patients in whom high brain activity was observed after the ventilators were turned off, the researcher says their visual cortices (which support conscious vision) showed intense activation “that potentially correlates with this visual experience”.

A new understanding

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Dr Borjigin acknowledges that her study in humans is very small in size and that more research is needed on what happens in the brain when we are dying.

However, after more than 10 years of research in this area, there is one thing that is clear to her: “I think instead of being hypoactive, the brain is hyperactive during cardiac arrest.”

But what happens to the brain when it realises that it is not getting oxygen?

“We're trying to understand that. So there's little in the literature. Really, nothing is known,” she says.

She mentions hibernation and tells me she has the following hypothesis: as animals, including at least rats and humans, we have an endogenous mechanism to deal with lack of oxygen.

“Until now, the brain is thought to be the innocent bystander of cardiac arrest: when the heart stops, the brain just drops dead. That's the current thinking: the brain can't deal with this and just dies.”

But, she insists, we don't know if that’s the case for sure.

She believes the brain does not take off its boxing gloves easily. Just like in responses to other crises, it fights:

“Hibernation is one of the very good examples that I believe [shows] the brain is actually equipped with the mechanism to survive this ordeal or the lack of oxygen. But that remains to be investigated.”

Much more to discover

Dr Borjigin considers that what she and her team have found in their studies is just the tip of a giant iceberg and that there is still a lot to discover:

“I believe that the brain has endogenous mechanisms to deal with hypoxia [when it is deprived of oxygen] that we're not understanding.

“So superficially we know that people who have a cardiac arrest have this amazing, subjective experience, and our data shows that that experience is due to a heightening of the brain activity.

“Now the question is: why does the dying brain have heightened brain activity?

“We need to come together to understand, to study, to research, to find out because we may be making a premature diagnosis of death for millions of people, since we don't understand the mechanism of death.”