August 13, 2013
Spike In Brain’s Electrical Activity Could Explain Near-Death Experience
redOrbit Staff & Wire Reports - Your Universe Online
The researchers conducted their study using rats, and observed how shortly after clinical death — when the heart stops beating and blood stops flowing to the brain – the rats displayed brain activity patterns characteristic of conscious perception.
"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, PhD, associate professor of molecular and integrative physiology and associate professor of neurology at the University of Michigan Medical School.
"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.
About one-in-five cardiac arrest survivors report having had a near-death experience during clinical death. According to previous research, these visions and perceptions have been described as "realer than real," although it remains unclear whether the brain is capable of such activity after cardiac arrest.
"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," Borjigin said.
The researchers analyzed the recordings of brain activity called electroencephalograms (EEGs) from nine anesthetized rats undergoing experimentally induced cardiac arrest. Within the first 30 seconds after cardiac arrest, all of the rats displayed a widespread, transient surge of highly synchronized brain activity that had features associated with a highly aroused brain.
The researchers also observed 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," said Borjigin.
"We were surprised by the high levels of activity," said study senior author George Mashour, MD, PhD, an anesthesiologist and assistant professor of anesthesiology and neurosurgery at the University of Michigan.
"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."
The brain is assumed to be inactive during cardiac arrest, although the neurophysiological state of the brain immediately following cardiac arrest had not been systemically investigated until now.
"This study tells us that reduction of oxygen or both oxygen and glucose during cardiac arrest can stimulate brain activity that is characteristic of conscious processing," said Borjigin.
"It also provides the first scientific framework for the near-death experiences reported by many cardiac arrest survivors.”
However, the researchers acknowledge there is a “long way to go” in understanding near-death experiences.
“We haven’t correlated the observed brain activity with a conscious experience,” Mashour said.
The only way to accomplish that would be to obtain electrode recordings in a person who had a near-death experience and returned to describe the incident, and there are very few, if any, possible circumstances under which that would be possible.