Aug 13, 2013 11:03 AM EDT By Russell Westerholm, UniversityHerald Reporter

The white light at the end of the tunnel are just a show human brains create when someone is having a near-death experience, scientists said in a study.

According to the Washington Post, researchers suggested the brain ramps up its neurological activity when the heart stops beating, but they can only speculate such activity actually causes visions of an "afterlife."

University of Michigan scientists conducted their experiment on nine anesthetized rats after inducing a cardiac arrest to record electroencephalogram (EEG) signals.

Within 30 seconds of their hearts stopping, their brains lived and even surged in neurological activity to create highly synchronized features normally associated with consciousness and visual activation. The activity was even at higher levels than a state of normal consciousness.

"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."

The study, published online Monday in the Proceedings of the National Academy of Sciences, said the rats' brains were creating 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.

The most common type of near-death experiences comes from cardiac arrest patients. About 20 percent say they had visions of bright light, important moments from their lives or feeling like they have left their body.

"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."

Borjigin had been testing this theory in rats since 2007, when two of her rodents died overnight. She reviewed the rats' brain activity from overnight and discovered unknown spikes in activity. She took the data to her colleague, Mashour, who is an EEG expert.

An EEG uses electrodes to measure voltage changes in the brain caused by neurons rapidly moving all at once. An awake brain would show spikes depending on what was being processed, while a dead brain should show a flat line.

When the rats' hearts stopped and blood no longer flowed to their brain, the EEG did ot flat-line, it continued as if it were awake.

"We saw a window of activity with certain signatures typically associated with conscious processing," Mashour said.

Despite their findings, many other scientists are skeptical and do not believe these results can be concluded from such a study.

"We don't have any rough and ready way to take a measurement and assign a meaning to it with regards to conscious content," said neurologist Nicholas D. Schiff of the Weill Cornell Medical College, who was not involved in the study. "There's no intrinsic reason to believe that these rats are in some heightened state of awareness."

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