Jim Chapman didn't think it was possible until it happened to him.
In the fall of 1999, after suffering a heart attack while exercising at a local fitness club, Chapman said he came back from what should have been a one-way trip. He was rushed to the hospital in an ambulance. But after half an hour of resuscitative treatment, Chapman's heart stopped beating.
Later, doctors told him that his heart ceased functioning for 2½ to four minutes. But during the time doctors declared him clinically dead, Chapman said he felt as if he wasn't even in the hospital.
"I know when my heart stopped there was a consciousness that continued from being in the ER," Chapman, 59, said. "Everything went silent. When I opened my eyes, I was standing on the edge of a valley, with the sun shining and the breeze on my face."
When he looked to his left, he said he saw "a shimmering area" that coalesced into his family. After the picture of his family faded away, Chapman said he became overwhelmed by a feeling of exhilaration.
When he blinked again, he said he was back in the ER, on the gurney, facing a nurse and doctor.
No longer a cynic, the retired Canadian broadcaster said his near-death experience changed his outlook on life.
According to conventional science, when people's hearts stop beating and they stop breathing, the brain shuts down and consciousness disappears. That school of thought believes that without the brain, consciousness isn't possible.
But a new study launched earlier this month will test a different theory: that consciousness is not localized to the brain and when the brain ceases functioning, the mind can continue to exist.
Led by Dr. Sam Parnia, an expert in the field of consciousness at the United Kingdom's University of Southampton, the study will monitor brain activity during cardiac arrest and test the validity of near-death and out-of-body experiences.
Called the "world's largest-ever study of near-death experiences," the Aware (Awareness During Resuscitation) study is a collaboration between 25 hospitals in the United Kingdom and the United States. U.S. participants include Indiana State University, Rosalind Franklin University of Medicine and Science, the University of Virginia and New York University, according to a spokesman for the University of Southampton.
Parnia said he has been "studying what happens when we die and near-death experiences for more than 12 years. What got me interested in it was seeing patients that I was taking care of die. ... And as I watched the people flatline, I wondered, what happened to this person that was thinking? Has their consciousness been annihilated?
"I realized this hasn't been properly tackled by science," he said.
Three Criteria of Death
During a cardiac arrest, Parnia said, the three criteria of death are present -- the heart stops beating, the lungs stop working and the brain shuts down.
But death is a process that can continue for hours or days and not a specific moment, he said. Additionally, contemporary medical advances make the process reversible in some cases.
Now that science can bring people back to life, he said, it's important to know what happens to the mind during the process.
Parnia said a number of recent studies conducted by independent researchers have shown that 10 to 20 percent of people who go through cardiac arrest and clinical death report near-death experiences.
A 2001 study published in the medical journal The Lancet found that 2.5 percent of 344 people studied had out-of-body experiences associated with cardiac arrest. Out-of-body experiences are a subset of near-death experiences.
Citing a Gallup survey published in 1982, the International Association for Near-Death Studies Inc. said that 5 percent of the adult population in the United States has had a near-death experience.
Verifying Out-of-Body Experiences
Although Parnia recognizes that he can't verify what people experience when they say they have a near-death experience, he said his project will try to verify out-of-body experiences.
Hospitals participating in the study will place signs with specific information on them in places that can only be viewed from the ceiling. If a cardiac patient reports seeing the information on the cards, Parnia said, it could mean that the patient could have indeed obtained the information while his consciousness was detached from his body.
"In most cases in life, we can't separate the mind from the brain," Pernia said. "There's no way we can separate them out. What we have found though is that when you study the brain and consciousness during death, the brain shuts down. Does the mind shut down as well?"
By studying the experiences of about 1,500 people at 25 hospitals over three years, Parnia hopes to begin to answer what he thinks are among the biggest questions in the 21st century: What is the mind? And where do thoughts come from?
A Word From the Skeptics
But not all scientists think that questions persist regarding the origin of consciousness.
Dr. Steven Novella, an academic clinical neurologist at Yale University School of Medicine and president and co-founder of the New England Skeptical Society, doesn't agree that this is a scientifically important or compelling question.
"The mainstream scientific community is pretty well-established that the mind is a manifestation of the brain," he told ABCNews.com. "There is not mental phenomenon apart from brain function."
"That NDEs [near-death experiences] occur is not controversial -- many people report remembering experiences around the time of cardiac arrest from which they were revived. ... The question is not whether or not people have such experiences -- the question is how to interpret them.
"Just as even the most rigorous skeptic does not question that people see UFOs, but rather what the UFOs likely are. The burden of proof for anyone claiming that NDEs are evidence for the survival of the self beyond the physical function of the brain is to rule out other more prosaic explanations. This burden has not been met," he wrote in a recent blog post on the subject.
Additionally, he said, what's most compelling from a neuroscientist's point of view is that scientists can induce out-of-body experiences.
"If we can make these experiences happen by doing something to the brain, that's pretty solid evidence that those experiences are happening in the brain," he said.
The Edge of Science
Still, that resistance is hardly an obstacle for Parnia.
"Whenever you're doing something that's at the edge of science, people are always resistant because colleagues who have been around have already formed an opinion on a particular subject," he said. "If you start to go against it, people will resist it.
"We're doing something that's never been done before. ... Death is commonly perceived to be a subject for philosophy or religion or theology. Of course, there's no reason for that to be the case. Science should be able to study it and guide it."