(CNN) -- You're about to go to "heaven" and live to tell about it. And your story will become the subject of scientific research.
It's the perfect day. You're strolling down a sidewalk, listening to an ensemble of bird songs, soaking up a balmy breeze fragranced with fresh spring flowers, and gazing up at a cloudless sky of pure azure.
Pleasantly distracted, you step off the sidewalk into the street. Brakes screech; horns blare; people shriek in horror. You snap back to reality ... just as the truck hits you.
You fly for yards like a rag doll; you land hard. You're numb all over and fading fast. It's all over; you know it. Your life flashes before you like an epic movie. The End.
You leave your body and look down at it. People are bending over it. Someone is sobbing uncontrollably. As the ambulance rushes up, a blinding light surges above you. It beckons you softly.
You follow it through a tunnel to a place much more vividly real and spectacular than the banner Sunday afternoon you just left behind. You are sure you have arrived in the hereafter.
Weeks later, you wake up to the steady beeps of an EKG monitor next to your hospital bed.
The scientific journey begins
If your hospital is in Belgium, Dr. Steven Laureys may pay you a visit, interested to hear what you remember from your NDE, or near-death experience.
He tells you that many people have gone down this road before you and that you can trust him with your experience.
"Patients in intensive care are scared to tell their stories," he said. They are afraid people won't take them seriously, especially doctors and scientists.
People who go on these fantastic journeys are often forever changed. Many seem to come back happier and no longer fear death, he said. The experience becomes a cornerstone of their lives.
NDEs feel "even more real than real," Laureys said. It's this sparkling clarity and living color of the experience, which many have when they lose consciousness, that he and his team have researched.
But he doesn't think it comes from a spirit world. Laureys is a scientist, he emphasizes. He prefers not to mix that with religion.
His hypothesis is that near-death experiences originate in human physiology. "It is this dysfunctional brain that produces these phenomena," he said.
Laureys and his staff are interested in how the brain creates the mind and its perception of reality. "Our main focus is consciousness research in comatose patients," he said. His team hopes to raise the quality of their comfort and care.
The same story, again and again
Over the years, many patients have awakened from comas to tell Laureys about trips to the hereafter.
Their stories all have elements that are the same or very similar.
"After being close to death, some people will report having had an out-of-body experience, having seen a bright light or being passed through a tunnel; all well-known elements of the famous Near-Death Experience," according to the study by Laureys and his team of six scientists.
Raymond and Nadine, both from Belgium, had heart attacks. When oxygen was cut off from their brains, they had out-of-body sensations, Laureys said.
"I felt as if I were sucked out of my body at one point," said Raymond. "I was going through a completely black tunnel, very, very quickly, a speed you cannot express, because you just don't experience it."
When Nadine's heart attack came on, she could see herself from outside her body. "It's as if you are on a cloud, even if it's not really that," she said.
It eluded her control, and that frightened her. She went into a dark hole. "You wonder if you will really return to your body," she said.
A light appeared at the end of Raymond's tunnel. He, too, was at first afraid and resisted. The light was female, and she "communicated" with him.
He surrendered to her. "I realized that I shouldn't struggle, and I let myself go. It was at that moment that the experience took place."
Scientific research on people having NDEs is tough, because the exact instant that they occur is unknown, making them nearly impossible to observe, Laureys said.
It would also be cruel to run brain scans on someone who was possibly facing the moment of death.
So, Laureys and his team studied the near-death memories of people who survived -- in particular those of coma patients -- with the help of a psychological examination.
The Memory Characteristics Questionnaire tests for sensory and emotional details of recollections and how people relive them in space and time. In other words, it gauges how present, intense and real a memory is.
They compared NDEs with other memories of intense real-life events like marriages and births, but also with memories of dreams and thoughts -- things that did not occur in physical reality.
The researchers paralleled new memories with old ones. And they compared the patients who had NDEs with groups of others who didn't.
Memories of important real-life events are more intense than those of dreams or thoughts, Laureys said.
"If you use this questionnaire ... if the memory is real, it's richer, and if the memory is recent, it's richer," he said.
The coma scientists weren't expecting what the tests revealed.
"To our surprise, NDEs were much richer than any imagined event or any real event of these coma survivors," Laureys reported.
The memories of these experiences beat all other memories, hands down, for their vivid sense of reality. "The difference was so vast," he said with a sense of astonishment.
Even if the patient had the experience a long time ago, its memory was as rich "as though it was yesterday," Laureys said.
"Sometimes, it is hard for them (the patients) to find words to explain it."
The questionnaire asks people about their level of certainty that a remembered experience was a real event and not imagined or dreamed. "They (the patients) are very convinced that it is real," Laureys said.
A simple Internet search reveals hundreds of accounts of near-death experiences -- some real, some perhaps invented. Many people are convinced they are proof positive that an afterlife exists outside of the physical realm -- and that it is wondrous.
There are reports of religious images appearing at times in NDEs, but they are not limited to one single religion, and they don't always appear. Sometimes Buddha, Jesus or Mohammed appear, but usually they don't, Laureys said.
Nevertheless, an NDE can make a convert of a skeptic. Dr. Eben Alexander is a well-known case of an agnostic scientist who became convinced of the existence of the spiritual.
He has often shared his story in television interviews with journalists and expressed his views in lectures and in books and video presentations, which he sells on his website.
Alexander, a neurosurgeon, according to his autobiography, has described his experience in the same terms as the Belgian researchers: "hyper-reality," "too real to be real."
In the beginning, he tried to interpret his experience as a brain function, he wrote on his website, but he became increasingly spiritual. He has come to the conclusion that people are reincarnated.
Alexander says his experience could not have been a hallucination, because the parts of the brain necessary to produce his experiences were basically dead when he had them.
It's your brain, Laureys tells you
Laureys strongly disagrees. "There is no evidence there can be conscious experience without brain activity," he said.
Lying in your hospital bed, you have become a true believer, and you are happier for it.
But your brain never died, the doctor tells you. You were in a coma. Perhaps your heart stopped for a while; maybe it didn't. But that's not even necessary to have an out-of-body experience.
"Many individuals having had NDEs were not physically in danger of death suggesting that the perception, on its own, of the risk of death seems to be important in eliciting NDEs," the study said.
It's enough just to think you're dying to have one.
The American Psychological Association concurs. It defines near-death experiences as "profound psychological events with transcendental and mystical elements, typically occurring to individuals close to death or in situations of intense physical or emotional danger."
In the case of coma patients, the brain producing the NDE may be functioning minimally, but it is still alive, Laureys hypothesized. He said one can stimulate certain parts of the brain to produce single elements of the experience.
It's a vivid hallucination, Laureys' report surmises. "It was a normal brain activity that produced their extraordinary perceptions."
Needs more research
Though the results of his studies were marked and consistent, the Belgian research team has tested only a small number of patients so far.
And it has not been able to scan brain images of patients having NDEs to get hard data on the hypothesis of the physiological nature of the experience.
Laureys' research alone is not enough. He wants to see more scientists get involved. As a doctor, he feels it's the compassionate thing for them to do.
Too many people have the experience for serious researchers to ignore it, he said, and a lot of people are afraid that their consciousness will linger long after they pass away, making them witnesses to whatever happens to their bodies.
"The public is historically afraid to be buried alive," Laureys said. "People are afraid to sign up as organ donors." They are scared they may have to watch them being extracted from their bodies.
There are more than enough spiritual models for NDEs, he said -- and superstitious ones. "There are a lot of crazy explanations out there."
It's high time for more hard science, Laureys said. A high percentage of his coma patients report having had NDEs, and he believes many of us go through these "afterlife" experiences when we die.
Laureys doesn't want to speculate on the existence of heaven or hell, but he does say that only a small minority of near-death experiences are horrifying. Most of them are pleasant and uplifting.
From his accounts, it sounds like more people go to "heaven" than to "hell."