Sleep paralysis is a condition characterized by temporary
paralysis of the body shortly after waking up (known as
hypnopompic paralysis) or, less often, shortly before falling
asleep (known as
hypnagogic paralysis).
[1]
Physiologically, it is closely related to the paralysis that occurs as a natural part of
REM (rapid eye movement) sleep, which is known as
REM atonia. Sleep paralysis occurs when the
brain awakes from a REM state, but the bodily paralysis persists. This leaves the person fully aware, but unable to move. In addition, the state may be accompanied by
hypnagogic hallucinations.
More often than not, sleep paralysis is believed by the person affected by it to be no more than a
dream.[
citation needed] This explains many dream recountings which describe the person lying frozen and unable to move. The
hallucinatory element to sleep paralysis makes it even more likely that someone will interpret the experience as a dream, since completely fanciful, or dream-like, objects may appear in the room alongside one's normal vision.