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.
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?
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.
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."