When an 87-year-old patient began having seizures after undergoing surgery as a result of a fall, doctors used electroencephalography (EEG) to monitor his status; unfortunately, the patient deteriorated and died while these recordings were being made.
The unforeseen event allowed scientists to record the electrical activity of a dying human brain due to the patient's do-not-resuscitate status and with the family's approval. While simplified EEG recordings from patients who had been removed off life support had previously been captured, the entire positioning of recording equipment, in this case, allowed for an unprecedented quantity of information.
"We measured 900 seconds of brain activity around the time of death and set a specific focus to investigate what happened in the 30 seconds before and after the heart stopped beating," Ajmal Zemmar, a neurosurgeon at the University of Louisville, said.
They noticed alterations in a specific band of brain oscillations, known as gamma oscillations, but also in others including delta, theta, alpha, and beta oscillations, just before and after the heart stopped functioning.
Neural oscillations, often known as brain waves, are the collective electrical activity of neurons firing in the brain. These electrical activity waves occur at varying frequencies, and different frequency bands have been connected to diverse conscious states.
As a result, neuroscientists have been able to link particular brain wave frequencies to specific activities such as information processing, perception, awareness, and memory while awake, as well as states of dreaming and meditation.
Just after the patient died from a cardiac arrest, his brain activity exhibited a relative surge in gamma band power that was interacting the most with alpha waves - a pattern comparable to memory recall.
"Given that cross-coupling between alpha and gamma activity is involved in cognitive processes and memory recall in healthy subjects, it is intriguing to speculate that such activity could support a last 'recall of life' that may take place in the near-death state," the team wrote.
What we know about brain waves during memory retrieval suggests that the brain may follow a predictable pattern of activity during death. The findings are also similar to changes in neural activity observed in rodents during death, according to the authors.
The findings are intriguing because they support the theory that the brain plans and executes a biological response to death that is conserved among species with a common evolutionary history and neural architecture.
Although it can be difficult to examine what happens to the brain during death, especially when patients leave behind bereaved family members, Zemmar finds solace in the concept that our brains may immerse us in our most cherished memories as we pass away.
The case report was published in Frontiers in Aging Neuroscience.
