'Flying' in your sleep may be a paralysis
http://www.telegraph.co.uk/connected/main.jhtml?view=DETAILS&grid=&xml=/connected/2007/03/05/nsleep0

'Flying' in your sleep may be a paralysis
By Roger Highfield, Science Editor

People who have out-of-body experiences, such as flying along a tunnel
towards a heavenly light, are more likely to suffer a strange effect
called sleep paralysis, according to a survey that adds to mounting
evidence for a biological explanation for the experience.
During sleep paralysis, people experience a kind of breakdown between
states of consciousness which takes place on the fringe of sleep, either
when falling asleep or waking. Because the brain turns off the body's
ability to move during dreaming, muscles can lose their tone, or
tension, causing paralysis.

The details of sleep paralysis vary from person to person. Some hear
vague sounds, indistinct voices and demonic gibberish. Others see
hallucinations of humans, animals and supernatural creatures. There is a
striking inability to move or to speak, or a weight on the chest.

Also common are feelings of rising off the bed or flying. In addition,
people report out-of-body experiences, sometimes accompanied by
"autoscopy" when they look down on themselves. Not surprisingly, these
moments are accompanied by fear.
Throughout history, there have also been accounts of people having
visions on the brink of death - what are now called "near-death
experiences".

Today, the two odd effects are linked by a study that backs the idea
that the near-death experience is a biological experience, rather than
anything to do with a spiritual dimension, a glimpse of heaven or the
existence of the soul.
People who have had near-death experiences are also likely to have
suffered sleep paralysis, according to the survey published by a team in
Neurology, the journal of the American Academy of Neurology, by Prof
Kevin Nelson, from the University of Kentucky, Lexington.
In a survey of 55 people who had a "near-death experience" - defined as
a time during a life-threatening episode when a person experienced a
variety of feelings, including unusual alertness, seeing an intense
light, and a feeling of peace - he found three quarters had an
out-of-body experience and half of them had also felt they had left
their body during the transition between wakefulness and sleep.

"We found that 96 per cent (24 of 25) of near-death subjects having
sleep paralysis also had an out-of-body experience either during sleep
transition or near-death," said Prof Nelson.

In a control group of 55 people, three reported an out-of-body
experience. Two of them also suffered sleep paralysis. Prof Nelson says
this suggests the same brain circuitry plays a role.

The sleep paralysis linked with out-of-body experiences was thought
rare, but may strike between 40 per cent and 60 per cent of people at
least once.

They report sensations of floating, flying, falling or leaving one's
body. It ranges from relatively tranquil floating experiences to
horrible feelings of falling or rising at high speed.