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Dying Brain Activity Found in Consciousness “Hot Zone”

A brain crackles with electricity.
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Fascination with near-death experiences, often featuring white light, encounters with deceased loved ones and auditory phenomena, has permeated our cultural consciousness. The prevalence of these shared elements has prompted researchers to explore the possibility that a form of consciousness persists even after cardiac function has ceased.

A link to consciousness

The journal Proceedings of the National Academy of Sciences recently published a study offering the suggestion that a burst of activity in the brain during its final moments may be linked to consciousness.

University of Michigan Associate Professor Jimo Borjigin spearheaded the research, which built upon animal studies conducted approximately a decade earlier in partnership with George Mashour, the founder and director of the Michigan Center for Consciousness Science.

Studies in animals and humans detailed comparable surges of gamma brain waves after experiencing oxygen deprivation due to cardiac arrest. Mashour noted that the study provided valuable insights into the neurophysiological mechanisms underlying such phenomena. “How vivid experience can emerge from a dysfunctional brain during the process of dying is a neuroscientific paradox,” he added.

The researchers examined four hospital patients who succumbed to cardiac arrest while in a comatose state and under EEG monitoring. After receiving permission from the patients' families, the individuals were taken off life support.

Two of the patients exhibited a surge in gamma wave activity – a rapid brain signal associated with consciousness – and an increased heart rate upon the removal of ventilator support. The activity was detected in the brain's "hot zone," an area implicated in dreaming, epilepsy-related visual hallucinations and altered states of consciousness. This area is found at the intersection between the occipital, parietal and temporal lobes.

Limitations remain

Although the two patients had a history of seizures, they did not experience any during the hour preceding their deaths, said Nusha Mihaylova, a clinical associate professor in the University of Michigan’s Department of Neurology. The remaining patients did not display increased heart rates or gamma activity after life support was withdrawn.

The authors noted some significant limitations to their work. Given the limited sample size, the researchers cautioned against drawing definitive conclusions from their findings. They also acknowledged the impossibility of determining the patients' experiences, as none survived.

Mihaylova stated that while the study did not correlate the observed neural signatures with patients' subjective experiences, the findings offered an exciting new framework for understanding covert consciousness in dying people.

Future, larger-scale studies involving multiple centers could yield critical data to determine whether the observed gamma activity bursts are indicative of a novel form of consciousness in the moments before death. These investigations should incorporate EEG-monitored ICU patients who recover from cardiac arrest to enable researchers to explore potential correlations between neural signatures and patient experiences.

As our comprehension of the dying brain evolves, researchers aim to unravel the enigma of near-death experiences and their implications for our understanding of consciousness. This knowledge could ultimately reshape our collective perception of life, death and the human experience.

Reference: Xu G, Mihaylova T, Li D, et al. Surge of neurophysiological coupling and connectivity of gamma oscillations in the dying human brain. PNAS. 2023;120(19):e2216268120. doi:10.1073/pnas.2216268120

Meet the Author
Ruairi J Mackenzie
Ruairi J Mackenzie
Senior Science Writer