Near-death experiences may be grounded in science after all, a new study published in the Proceedings of the National Academy of Science shows.
Led by researchers from the University of Michigan Medical School, the study reports brain activity patterns indicative of consciousness in rats shortly after clinical death when the heart stops beating and blood stops flowing to the brain.
"This study, performed in animals, is the first dealing with what happens to the neurophysiological state of the dying brain," said lead study author Jimo Borjigin, Ph.D., associate professor of molecular and integrative physiology and associate professor of neurology at the University of Michigan Medical School.
Despite 20 percent of all cardiac arrest survivors reporting experiencing a near-death experience during clinical death, whether or not the brain is capable of such activity has long remained a mystery.
"We reasoned that if near-death experience stems from brain activity, neural correlates of consciousness should be identifiable in humans or animals even after the cessation of cerebral blood flow," she said.
In order to find out, the researchers analyzed the recordings of brain activity called electroencephalograms (EEGs) from nine anesthetized rats experiencing induced cardiac arrest. Sure enough, within the first 30 seconds after cardiac arrest, all of the rats demonstrated a surge of highly synchronized albeit transient brain activity similar to a highly aroused brain.
Additionally, the researchers discovered nearly identical patterns in the dying brains of rats undergoing asphyxiation.
"The prediction that we would find some signs of conscious activity in the brain during cardiac arrest was confirmed with the data," Borjigin said.
However, study senior author anesthesiologist Dr. George Mashour, Ph.D., assistant professor of anesthesiology and neurosurgery, said they were suprised by just how high these levels of activity were.
"In fact, at near-death, many known electrical signatures of consciousness exceeded levels found in the waking state, suggesting that the brain is capable of well-organized electrical activity during the early stage of clinical death," he said.
What this says, Borjigin concludes, is that a lack of oxygen or oxygen as well as glucose can stimulate brain activity similar to that experienced in a conscious brain and, going forward, could offer a framework for those near-death experiences reported by so many.
"It will form the foundation for future human studies investigating mental experiences occurring in the dying brain, including seeing light during cardiac arrest," she said.