A new study of near-death experiences has revealed key changes in the brain that may trigger its onset. Scientists have long believed that the heart plays a central role in death, but the new study challenges that long-held belief.

The findings, published in the Proceedings of the National Academy of Sciences, are based on studies of heart and brain activity of rats in the moments before the animals died from lack of oxygen. The researchers found that the animals' brains sent a flurry of signals to the heart that caused fatal damage to the organ that led to death, Fox News reports.

But when the researchers blocked those signals, the heart survived for longer. If a similar process occurs in humans, as the researchers suspect, then it might be possible to help people survive after their hearts stop by cutting off these signals from the brain.

"People naturally focus on the heart, thinking that if you save the heart, you'll save the brain," Jimo Borjigin, a neuroscientist at the University of Michigan Medical School in Ann Arbor who helped lead the new research.

"[But] you have to sever [the chemical communication between] the brain and heart in order to save the heart," Borjigin told LiveScience, adding that the finding is "contrary to almost all emergency medical practice."

Every year, some 400,000 Americans experience cardiac arrest and only about 10 percent survive, according to the American Heart Association.

But the new study shows even after a person’s heart stops beating, and loses consciousness and no signs of life, the brain continues to be active — flooding the heart with signals, probably in a desperate attempt to save the organ.

That brain activity may account for the near-death experiences some people report, Borjigin said.