Science News has a major article discussing sleep paralysis, the state in which a person can wake, but remains in the paralysed state used to stop movements during dreaming.
Sleep paralysis, sometimes called ‘awareness during sleep paralysis’, to distinguish it from the normal muscle inhibiting function of REM sleep, is now attracting a substantial amount of research.
One paper by researchers Katharine Holden and Chris French (PDF) even suggested that some ‘alien abduction’ experiences may be due, in part, to terrifying sleep paralysis episodes.
Little is known, however, about the exact brain mechanisms which control sleep paralysis (although parts of the brain stem are known to be important) meaning it is has traditionally been difficult to make educated guesses about why paralysis sometimes remains after waking.
Link to Science News article ‘Night of the Crusher’