Sleep paralysis
Sleep paralysis is a brief, harmless state in which the mind wakes before the body regains its mobility, at the edge of falling asleep or waking up. For a few seconds to a few minutes, the sleeper is aware yet unable to move or speak, sometimes alongside images or a felt presence. It reflects the muscular atonia of REM sleep lingering while consciousness has already returned. Very common, it fades on its own.
What is really happening
During REM sleep, your body deliberately powers down: the muscles go slack to keep you from acting out your dreams. In sleep paralysis, your awareness comes back a little ahead of that release. You feel awake, lucid, yet still motionless for a short moment. The brain, meanwhile, can carry a scrap of dream onto the backdrop of your bedroom, which is where those striking images come from.
The faces cultures gave it
Nearly every culture has named this nighttime visit. In Japan it is kanashibari, the sense of being "bound by metal." In the English countryside it was the "old hag" sitting on the chest, the word nightmare itself coming from a creature that oppresses the sleeper. Newfoundland called it the Old Hag. These stories turn a universal sensation into tales, a mirror of fears rather than a curse.
Riding out the moment
If you know this moment, take heart that it always passes on its own, often within a few breaths. Many find it calming to remember, in the middle of the scene, that they are simply at the border of sleep and waking. Gently resting your attention on your breath, or on one finger to wiggle, eases movement back in. The presence you feel is only your dream lingering.
Sources
- , Dreaming: An Introduction to the Science of Sleep (2002)
- , The Nightmare Experience, Sleep Paralysis and Witchcraft Accusations (2003)