Neuroscientists Learn More About the 'Wave of Death' of Consciousness

They've pinpointed its source and discovered it can be reversed

Hiya!

For whatever reason, I’ve always been more curious about where we came from before birth than where we go when we die, even as a kid. But I seem to be an outlier because most people are more concerned about where they’re going, and few have even considered where they came from. Despite many theories and countless religions, humanity may never know the answers to either question — not while still alive, anyway.

Death itself is a strange thing. The movies make it seem as though death occurs practically, and sometimes literally, with the flip of a switch — the flat line on a heart monitor, a character can’t find a pulse, someone takes their last breath — and then it’s all done. But unsurprisingly, reality is more complicated. We may not know what happens after we die, but scientists are learning quite a bit about what happens while we die.

Point of Death

Generally speaking, death has a pretty universally defined state characterized by a complete and irreversible termination of bodily functions. Meaning there’s no pulse, no brain activity, and pupils don’t respond to light.

But from a neurological perspective, death is a tricky concept to define. A growing body of research suggests that death isn’t so much a flip of a switch from life to death but a process that can take several minutes, includes complex brain activity, and, in some cases, is reversible.

Previous Research

We require oxygen to live, and when we don’t get it, our bodies and brains experience oxygen deprivation, also known as anoxia. In a previous study published in Frontiers in Neuroscience, researchers from the Dynamics of Epileptic Networks and Neuronal Excitability team at Paris Brain Institute showed that when anoxia sets in, the brain engages in a series of successive changes.

The brain generally stores a critical molecule called ATP, which is the primary energy source for all cellular activities. But when the brain is deprived of oxygen, its ATP storage is rapidly depleted. In turn, this disrupts brain neurons and releases a massive amount of glutamate, an essential and the most abundant excitatory neurotransmitter that’s released by nerve cells in the brain that send signals throughout the body.

A neuroscientist with the Paris Brain Institute (PBI) and one of the study’s authors, Séverine Mahon, explained in a press release,

"Neural circuits seem to shut down at first...then we see a surge in brain activity — specifically an increase in gamma and beta waves. These waves are usually associated with a conscious experience. In this context, they may be involved in near-death experiences reported by people who have survived cardiorespiratory arrest."

Afterward, neuronal activity gradually decreases until perfect electrical silence occurs in the brain. This can be shown by a flat line on an electroencephalogram (EEG), which uses small electrodes attached to a person’s scalp to measure electrical activity.

This might seem like the end of the death process, but this silence is quickly interrupted by a high-amplitude wave called “the wave of death” caused by the depolarization of neurons — a phenomenon scientists call “anoxic depolarization.” This process seems to initiate cell death in the brain’s cortex — the wrinkly part that makes up the outer layer of the brain’s surface.

Antoine Carton-Leclercq, who is also with the PBI and an author of the study, explains:

"This critical event, called anoxic depolarization, induces neuronal death throughout the cortex. Like a swan song, it is the true marker of transition towards the cessation of all brain activity."

The wave of death is distinguished by massive electrical flows moving slowly inside the brain, spreading throughout the cortex until consciousness is fully and completely extinguished. Mahon and Stéphane Charpier, another author of the study who is with Paris’ Sorbonne University, told Newsweek:

"Recovering from such a cataclysm requires so much energy that neurons often die in the minutes and hours following the wave of death. This is why, before our work, the wave of death was thought to be irreversible."

However, the team found that the wave of death isn’t as final as once believed. If the brain receives oxygen quickly enough, the effects of anoxic depolarization can be reversed. A process the scientists named a “wave of resuscitation,” which engages in a slow recovery of brain functions.

Identifying both waves — the waves of death and resuscitation — is incredible and goes a long way in helping us better understand the death process. Yet, like so many discoveries, the results lead to more questions. The researchers state in the press release:

“We already knew that it is possible to reverse the effects of anoxic depolarization if we manage to resuscitate the subject within a specific time window. We still had to understand in which areas of the brain the death wave is likely to do the most damage to preserve brain function as much as possible.”

So, next, the researchers wanted to find where the wave of death originates in the cortex and whether it spreads evenly throughout. And that’s precisely what they did.