Near-death experiences aren't imagined, study finds

The bright light, visions and heightened awareness reported by nearly 20 percent of people who have survived cardiac arrest has been hotly debated as a near-death experience, and now those patients have a study that shows it's not all in their heads.

Well, it is in their heads, as researchers have found brain activity associated with consciousness continues in rats for up to 30 seconds after the heart has stopped beating and blood has stopped flowing.

The findings even show a surge in electrical activity and coherence in the brain immediately after the heart stops, suggesting a higher level of consciousness than would be possible in a waking state.

"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, associate professor of molecular and integrative physiology and associate professor of neurology at the University of Michigan Medical School.

Borjigin’s team implanted electrodes on the surface of the brains of nine rats, then injected the animals with potassium chloride, which stopped their hearts and stilled their blood -- the clinical definition of death. For up to 30 seconds afterward, the electrodes picked up synchronized, high-frequency gamma waves.

Borjigin and her team published their findings this week in the Proceedings of the National Academy of Sciences.

"By presenting evidence of highly organized brain activity and neurophysiologic features consistent with conscious processing at near-death, we now provide a scientific framework to begin to explain the highly lucid and realer-than-real mental experiences reported by near-death survivors," the authors wrote.

Doctors have long considered 20 minutes the threshold for survival after the heart stops pumping blood to the brain, depriving it of oxygen and glucose.

But that idea has already been turned on its head, with reports of patients "waking up" after 45 minutes of CPR. More recently, some doctors specializing in resuscitation have saved patients hours after their hearts stopped beating.

In some cases, patients have memory of hearing or seeing events that happened several minutes after their hearts stopped.