Working to Stave Off Brain’s ‘Wave of Death’Ioannis Tsotras – Getty Images Researchers studying the brain’s final moments have gained new insight into the “wave of death” that occurs before a brain’s activity fully flatlines.
When neural activity stops, it doesn’t stop abruptly, but over time.
The team hopes to find ways to keep the brain functioning even when the heart and lungs fail.
The brain doesn’t shut off like a light switch, even as death approaches. While other bodily organs —namely the heart and lungs—have sudden stops, the brain flickers on through active neurons in a “wave of death ” until it reaches a state of electrical silence.
Brain researchers in Paris have been working to better understand these cascading changes that occur when a brain is deprived of oxygen , as well as what they mean for our conceptualization of death. The results, published in the journal Neurobiology of Disease , show where this wave originates and just how we can potentially stave it off.
Stephane Charpier, head of the research team at the Paris Brain Institute and study author, said in a statement that her team now knows “that a flat EEG does not necessarily mean the definitive cessation of brain functions.” This means that there could be hope for our ability to keep an oxygen-starved brain working even longer than expected.
When the brain stops receiving oxygen, the adenosine triphosphate (ATP) stores that act as fuel for the cells quickly get sucked away. Then, it all becomes a bit chaotic. Electrical balances go out of whack and huge amounts of chemicals are released. “Neural circuits seem to shut down at first,” Severine Mahon, another author on the paper, said in a statement, “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.”
Once the process starts, the neuron activity trends downward until the brain is completely electrically silent. But that isn’t the end, because it’s now time for the “wave of death,” which totally alters the function and structure of the brain. “This critical event, called anoxic depolarization, induces neuronal death throughout the cortex,” Antoine Carton-Leclercq, first author on the study, said in a statement. “Like a swan song, it is the true marker of transition toward the cessation of all brain activity.”
And now we know where it’s coming from. The team found (while studying rats ) that the wave originates in a part of the brain called the neocortex—a region that makes up a large percentage of your brain, which can be divided into six layers. The “wave of death” seems to originate in layer five, deep in the tissue of the neocortex. “We have observed this same dynamic under different experimental conditions,” Mahon said, “and believe it could exist in humans.”
Why does this phenomenon come from so deep in the brain? The team believes that this “wave of death” starts in layer five because the neurons in that layer have exceptionally high oxygen requirements. But it seems like restoring oxygen flow can reverse at least some of these effects. When the team reoxygenated the rats’ brains, the cells replenished their ATP reserves and restored synaptic activity.
And that means there’s hope that the wave can be stopped . Carton-Leclercq said that researchers already knew that brain function could be protected if a patient was resuscitated fast enough. But—while it may take time to figure out exactly how to stop this wave—knowing where it comes from could eventually be helpful in preserving function even more effectively.
“This new study advances our understanding of the neural mechanisms underlying changes in brain activity as death approaches,” Charpier said in a statement. “It is now established that, from a physiological point of view, death is a process that takes its time… and that it is currently impossible to dissociate it rigorously from life.”
“We now need to establish the exact conditions under which these functions can be restored,” Charpier continues, “and develop neuroprotective drugs to support resuscitation in the event of heart and lung failure.”
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