So you're floating peacefully above your body, looking down. You see doctors and nurses scramble to revive the corporeal you that's still lying on the gurney.

Chances are you've heard a similar description of what's called a near death, out-of-body experience. For a lot of people, it's a powerful, even mystical experience. Perhaps proof of an afterlife. However, while there may be an afterlife, scientists have found that the experience of hovering outside one's body coinciding with a brush with death is probably all in the mind.

It turns out that an out-of-body experience is pretty common. In fact, about one in twenty people listening to this show have had one. In the majority of cases, that hovering sensation happens when people are either falling asleep or waking up.

Here's what happens. When we nod off, we first go through an intermediate stage of light dozing before entering the deep, dream-filled sleep stage, called REM. When we wake up, we pass from REM through that same in between sleep stage before regaining consciousness. Some people, though, are prone to go directly from wakefulness to REM sleep, and from REM to wakefulness.

In other words, they blend REM sleep and consciousness, a phenomenon called arousal system disturbance. One consequence is that you can be awake and still dreaming, dreams that can include floating outside your body.

Now, it turns out that a physical crisis, like being near death, can trigger this same response in people with arousal system disturbance. Which means that the floating, white light experience may seem and feel very real, though it's really all in the mind.