By Caleb Hellerman
CNN Medical Senior Producer

Our special this weekend, “Another Day: Cheating Death,” includes the story of Laura Geraghty, a school bus driver in Massachusetts who survived a cardiac arrest that left her without a heartbeat for 57 minutes.  While the medical aspect is astounding, just as interesting is the story Geraghty told when she was revived.

She’d floated out of her body, and found herself in a world of incredibly bright light – heaven, she says. While there she saw her son, daughter, granddaughter and even her ex-husband – who wouldn’t take her hand when she reached out to him. Eventually she came back to the real world.

Many cultures and religions describe a vivid world on the border of life and death, but the classic modern near-death experience, or NDE, was described by Dr. Raymond Moody in his 1966 book, “Life After Life.”  While not every NDE includes the same features, among the most common – according to Moody – are bright lights, a tunnel, a sense of being out of the body and an intense feeling of peace and calm.

Most people who return from the verge of death with memories like this say it’s a life-changing experience. Many view it as direct proof of an afterlife – that the place they “visit” is the world we all will see after we die. But increasingly, near-death experience (a term coined by Moody) is being studied from the perspective of science.

Dr. Kevin Nelson, a neurologist at the University of Kentucky, believes an NDE is caused by REM activity, the same type of brain activity that’s linked to dreaming.  REM activity, says Nelson, can be triggered by intense stress or even lack of oxygen. In fact, he says many people experience an out-of-body experience during fainting episodes, or if they momentarily lose blood flow to the brain – as in a massive head rush.

Another intriguing experiment is underway at more than two dozen medical centers in the U.S. and Europe. It’s led by Dr. Sam Parnia, a critical care physician at New York Presbyterian-Cornell Hospital in New York. The setup is ingenuous. In hospital areas with critically ill patients, panels are hung from the ceiling to a height at which only someone floating near the ceiling could see what’s painted on top. If any patient reports a sense of floating - investigators can see if they accurately report what’s on the panel. Because the patients are being carefully monitored in ICUs, the experiment could also determine whether there are physical differences among people who report NDEs, and those who don’t.  

Parnia says he doesn’t know what he’ll find – but he does believe science can answer the question of what these experiences are really all about.  

What do you think? Can near-death experience be explained by what’s going on in the brain?

Watch “Another Day: Cheating Death” at 8 and 11 p.m. ET Saturday and Sunday.

Don’t miss, Dr. Gupta’s new book “Cheating Death”, available now wherever books are sold.  Be sure to follow – and tweet your medical miracle to – @sanjayguptacnn with #miracle and you could win a signed copy of the book and a Skype guest appearance from Dr. Gupta at your book club event.

Editor’s Note: Medical news is a popular but sensitive subject rooted in science. We receive many comments on this blog each day; not all are posted. Our hope is that much will be learned from the sharing of useful information and personal experiences based on the medical and health topics of the blog. We encourage you to focus your comments on those medical and health topics and we appreciate your input. Thank you for your participation.