“A lot of people believed that what they saw was heaven,” said lead researcher and neurologist Jimo Borjigin. “Science hadn’t given them a convincing alternative.”
Scientists from the University of Michigan recorded electroencephalogram (EEG) signals in nine anesthetized rats after inducing cardiac arrest. Within the first 30 seconds after the heart had stopped, all the mammals displayed a surge of highly synchronized brain activity that had features associated with consciousness and visual activation. The burst of electrical patterns even exceeded levels seen during a normal, awake state.
In other words, they may have been having the rodent version of a near-death experience.
“On a fundamental level, this study makes us think about the neurobiology of the dying brain,” said senior author and anesthesiologist George A. Mashour. It was published Monday online by the Proceedings of the National Academy of Sciences.
Near-death experiences have been reported by many who have faced death, worldwide and across cultures. About 20 percent of cardiac arrest survivors report visions or perceptions during clinical death, with features such as a bright light, life playback or an out-of-body feeling.
“There’s hundreds of thousands of people reporting these experiences,” Borjigin said. “If that experience comes from the brain, there has to be a fingerprint of that.”
An unanswered question from a previous experiment set her down the path of exploring the phenomenon. In 2007, Borjigin had been monitoring neurotransmitter secretion in rats when, in the middle of the night, two of her animals unexpectedly died. Upon reviewing the overnight data, she saw several unknown peaks near the time of death.
This got her thinking: What kinds of changes does the brain go through at the moment of death?
Then last year, Borjigin turned to Mashour, a colleague with expertise in EEG and consciousness, for help conducting the first experiment to systematically investigate the brain after cardiac arrest. EEG uses electrodes to measure voltage fluctuations in the brain caused by many neurons firing at once. A normal, awake brain should show spikes depending on what types of processing are going on; in a completely dead brain, it flat-lines.
When the heart suddenly stops, blood flow to the brain stops and causes death in a human within minutes. A likely assumption would be that, without a fresh supply of oxygen, any sort of brain activity would go flat. But after the rats went into cardiac arrest, Mashour and his colleagues observed the opposite happening.