Summary: A groundbreaking new study provides early evidence of consciousness in the dying brain, shedding light on the mysteries of near-death experiences.
Researchers identified a surge of gamma wave activity, associated with consciousness, in the dying brains of comatose patients. The activity was detected in a neural hotspot associated with dreaming and altered states of consciousness, providing exciting new insights into the human mind.
Though caution is advised due to the small sample size, this research could change the way we understand death.
A new study provides early evidence of a surge of activity correlated with consciousness in the dying brain.
The study identified four patients who passed away due to cardiac arrest in the hospital while under EEG monitoring. Two of the patients showed an increase in heart rate along with a surge of gamma wave activity, considered the fastest brain activity and associated with consciousness.
The activity was detected in the so-called hot zone of neural correlates of consciousness in the brain, the junction between the temporal, parietal, and occipital lobes in the back of the brain.
Source: University of Michigan
Reports of near-death experiences–with tales of white light, visits from departed loved ones, hearing voices, among other attributes—capture our imagination and are deeply engrained in our cultural landscape.
The fact that these reports share so many common elements begs the question of whether there is something fundamentally real underpinning them—and that those who have managed to survive death are providing glimpses of a consciousness that does not completely disappear, even after the heart stops beating.
A new study published in the Proceedings of the National Academy of Science, provides early evidence of a surge of activity correlated with consciousness in the dying brain.
The study, led by Jimo Borjigin, Ph.D., associate professor in the Department of Molecular & Integrative Physiology and the Department of Neurology, and her team is a follow-up to animal studies conducted almost ten years ago in collaboration with George Mashour, M.D., Ph.D., the founding director of the Michigan Center for Consciousness Science.
Similar signatures of gamma activation were recorded in the dying brains of both animals and humans upon a loss of oxygen following cardiac arrest.
“How vivid experience can emerge from a dysfunctional brain during the process of dying is a neuroscientific paradox. Dr. Borjigin has led an important study that helps shed light on the underlying neurophysiologic mechanisms,” said Mashour.
The team identified four patients who passed away due to cardiac arrest in the hospital while under EEG monitoring. All four of the patients were comatose and unresponsive. They were ultimately determined to be beyond medical help and, with their families’ permission, removed from life support.
Upon removal of ventilator support, two of the patients showed an increase in heart rate along with a surge of gamma wave activity, considered the fastest brain activity and associated with consciousness.
Furthermore, the activity was detected in the so-called hot zone of neural correlates of consciousness in the brain, the junction between the temporal, parietal and occipital lobes in the back of the brain. This area has been correlated with dreaming, visual hallucinations in epilepsy, and altered states of consciousness in other brain studies.
These two patients had previous reports of seizures, but no seizures during the hour before their deaths, explained Nusha Mihaylova, M.D., Ph.D., a clinical associate professor in the Department of Neurology who has collaborated with Dr. Borjigin since 2015 by collecting EEG data from deceased patients under ICU care.
The other two patients did not display the same increase in heartrate upon removal from life support nor did they have increased brain activity.
Because of the small sample size, the authors caution against making any global statements about the implications of the findings. They also note that it’s impossible to know in this study what the patients experienced because they did not survive.
“We are unable to make correlations of the observed neural signatures of consciousness with a corresponding experience in the same patients in this study. However, the observed findings are definitely exciting and provide a new framework for our understanding of covert consciousness in the dying humans,” she said.
Larger, multi-center studies including EEG-monitored ICU patients who survive cardiac arrest, could provide much needed data to determine whether or not these bursts in gamma activity are evidence of hidden consciousness even near death.
Additional authors on this paper include Gang Xu, Duan Li, Fangyun Tian, Peter M. Farrehi, Jack M. Parent and Michael Wang.
Surge of neurophysiological coupling and connectivity of gamma oscillations in the dying human brain
The brain is assumed to be hypoactive during cardiac arrest. However, animal models of cardiac and respiratory arrest demonstrate a surge of gamma oscillations and functional connectivity.
To investigate whether these preclinical findings translate to humans, we analyzed electroencephalogram and electrocardiogram signals in four comatose dying patients before and after the withdrawal of ventilatory support.
Two of the four patients exhibited a rapid and marked surge of gamma power, surge of cross-frequency coupling of gamma waves with slower oscillations, and increased interhemispheric functional and directed connectivity in gamma bands.
High-frequency oscillations paralleled the activation of beta/gamma cross-frequency coupling within the somatosensory cortices. Importantly, both patients displayed surges of functional and directed connectivity at multiple frequency bands within the posterior cortical “hot zone,” a region postulated to be critical for conscious processing. This gamma activity was stimulated by global hypoxia and surged further as cardiac conditions deteriorated in the dying patients.
These data demonstrate that the surge of gamma power and connectivity observed in animal models of cardiac arrest can be observed in select patients during the process of dying.