sleep paralysis

I think everyone has had this experience: You're dreaming and wake up suddenly only to discover that you can't move. Maybe your eyes are still closed, maybe they are open, but your arms, legs, head, even fingers and toes are immobile. Within a minute, you have regained your ability to move, but it is a very uncomfortable and sometimes scary situation.

This is called sleep paralysis and has happened to most people. At dinner last night, the topic of the ghosts at the Driskill hotel came up (some guests were staying there). This led to a conversation about personal scary experiences, and someone brought up waking up and feeling paralyzed. I thought I had read before that during REM sleep (or some phase around there), the brain signals for some kind of chemical to be released that in effect (affect?) paralyzes the body, allowing for a more restorative sleep. A woman at the table said she had heard differently: at night, our souls leave our body to go travelling around, presumably to the land where they come from, maybe to run around the Driskill and scare people. When we wake up and feel paralyzed, it is because our soul (maybe "subtle body" is more accurate. she didn't say soul, but I can't remember) has yet to return to our body.

Whatever the cause, sleep paralysis is sometimes accompanied by auditory and visual hallucinations that can be quite scary. I found this on a medical definition website (http://www.medterms.com/script/main/art.asp?articlekey=9810):
Sleep paralysis goes by a number of names, including the "old hag" in Newfoundland (for an old witch thought to sit on the chest of the paralyzed sleeper), "kokma" in the West Indies (for a ghost baby who jumps on the sleeper's chest and attacks the throat), "kanashibari" in Japan and "gui ya" or ghost pressure in China (because a ghost is believed to sit on and assault the sleeper). Medically, sleep paralysis is sometimes called waking paralysis, predormital (before-sleep) paralysis, postdormital (after-sleep) paralysis, and REM sleep atonia.

I like that! Kokma sounds spooky - a ghost baby, holy shit! Actually, they are all pretty terrifying. There is another interesting article on answers.com and wikipedia (I think it's the same one).