Cardiac arrest survivors frequently report marvelous, inexplicable conscious sensations during their near-death experiences. Although such claims may seem hard to dispute or affirm objectively, new research suggests that these ethereal episodes may be grounded in observable biological processes.

By monitoring brain activity in anesthetized rats undergoing experimentally-induced cardiac arrest, researchers at the University of Michigan recorded signatures and patterns characteristic of conscious perception within 30 seconds after clinical death. The findings, which are published in the journal PNAS, represent the first systematic investigation of the neurophysiological state of the brain following cardiac arrest.

“This study, performed in animals, is the first dealing with what happens to the neurophysiological state of the dying brain," lead author Jimo Borjigin of the University of Michigan Medical School said in a press release. "It will form the foundation for future human studies investigating mental experiences occurring in the dying brain, including seeing light during cardiac arrest.”

In all of the test subjects, the cessation of blood flow through the heart and brain was followed by a temporary, widespread surge of highly synchronized activity similar to that of a highly aroused brain. According to senior author George Mansour, M.D., Ph.D., the activity had been predicted by the research team; however, the high, synchronized levels came as a surprise to everyone.

“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 noted.

These excessive levels of activity may explain why approximately 20 percent of cardiac arrest survivors report near-death experiences, and why some refer to them as “realer than real,” according to the press release. Additionally, identical results were observed in rats undergoing experimental asphyxiation, suggesting that the near-death experience is not exclusive to cardiac arrest survivors.

"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," Borjigin explained. "It also provides the first scientific framework for the near-death experiences reported by many cardiac arrest survivors."

According to the National Institutes of Health, near-death experiences have been the focus of several studies over the past 30 years, with proposed explanations ranging from dissociative defense mechanisms to memories of birth. The sensation typically involves peace and well-being, out-of-body experiences, brilliant lights, and the perceived passage into a different realm.

Source: Jimo Borjigin, UnCheol Lee, Tiecheng Liu, Dinesh Pal, Sean Huff, Daniel Klarr, Jennifer Sloboda, Jason Hernandez, Michael M. Wang, and George A. Mashour. “Surge of neurophysiological coherence and connectivity in the dying brain.”PNAS 2013 ; published ahead of print August 12, 2013, doi:10.1073/pnas.1308285110