It is unclear how the brain works just before cardiac arrest. Although cardiac arrest is generally accompanied by the loss of overt awareness, it is unknown if people can experience covert consciousness while they are dying. About 10 to 20 percent of cardiac arrest survivors report having near-death experiences (NDE), which are said to be highly vivid and common to persons from different ethnic and theological backgrounds. In fact, it has been asserted that these events take place during clinical death and even when the electroencephalogram (EEG) is in electrical quiescence. NDE provides a biological paradox that 
calls into question our basic assumptions about the dying brain, which is generally thought to be nonfunctional in such circumstances.
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Patients displayed a spike in gamma wave activity
Early evidence of a spike in activity in the dying brain that is associated with consciousness is shown in a recent study that was published in the Proceedings of the National Academy of Sciences. This study conducted by a team of highly skilled scientists at the Michigan Center for Consciousness Science, is a follow-up to animal studies conducted almost ten years ago in collaboration with other teams. Following cardiac arrest, similar gamma activation signatures were observed in the dying brains of both animals and humans.
This study looked back at patients who passed away in the neurointensive care unit (NICU) at Michigan Medicine, University of Michigan since 2014. Four people who died from cardiac arrest while being monitored by an EEG were discovered by the team. They were all unconscious and comatose. In the end, it was decided that they couldn’t be saved by medicine, and with their family’s consent, they were taken off life support. Two of the patients displayed a rise in heart rate and a spike in gamma wave activity, which is thought to be the quickest brain activity and is linked to consciousness when the ventilator support was removed.
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Additionally, activity in the brain’s “hot zone” of neural correlates of consciousness, which is the intersection of the temporal, parietal, and occipital lobes, was found. In other brain research, this region has been linked to altered states of consciousness, visual hallucinations in epilepsy, and dreaming. While two patients did not exhibit the same increase in heart rate following removal from life support or exhibit higher brain activity, the other two patients had a history of seizures but had none within the hour before their deaths.
The scientists advise against drawing any broad conclusions regarding the relevance of the findings due to the tiny sample size. They further point out that because the patients in this study did not survive, it is difficult to tell what they went through.
Clinical significance
The study’s empirical data strongly suggests that it is possible to activate the dying human brain. To ascertain if these bursts in gamma activity are proof of concealed consciousness even close to death, larger, multi-center investigations using EEG-monitored ICU patients who survive cardiac arrest may be necessary.
Read Also: Researchers Capture What Happens in the Brain during Near-Death Experiences
Conclusion
Just like the scientists said, it’s too early to draw conclusions. However, the current investigation supports prior findings in animal models and in dying patients that global hypoxia increases gamma power and gamma coupling with slower oscillations on EEG.
References
Surge of neurophysiological coupling and connectivity of gamma oscillations in the dying human brain
