Quote:
● Sleep paralysis is one of a suite of sleep disorders known as the parasomnias, and an excellent example of how our brain mechanisms governing one state of consciousness can malfunction and intrude onto another. With sleep paralysis, the person wakes up out of REM sleep and tries to rise, but their brain stem is slower to make the transition and continues to inhibit muscle activity (muscle paralysis, aka "atonia," being one of the three REM traits). In addition, body paralysis is often paired with what are called "hypnagogic hallucinations" -- aural and visual elements from the dream world superimposed over top of the waking world.
● When this happens the other way around--when waking functions intrude on sleep--it is called an arousal disorder. The most well known of these is sleepwalking also known as somnambulism. Sleepwalking, in Harvard researcher Allan Hobson's words, is like the well-known Yellow Pages ad, except "it's your brain stem doing the walking." The sleeper is actually in deep slow-wave sleep. The cerebral cortex is thought to be more or less offline, yet somehow complex goal-directed behaviors get fired up and the sleeper is sent staggering around the house.
● "Sleep terrors"--familiar to many parents--is the term for another arousal disorder, in which young children (and some adults) sit bolt upright out of sleep and scream holy murder. Their eyes may be open but they're oblivious to the calming voices of their parents; in fact, these children are really in slow-wave sleep.
● Another variation--linked to the onset of Parkinson's disease--happens mostly in men over fifty. It's called "REM sleep behavior disorder," and it's similar to sleep-walking except the sleeper isn't in slow-wave but in REM sleep. Somehow muscle atonia is deactivated and sleepers get up to act out their often violent dreams--often on their spouses.
● Parasomnias are incredibly important in understanding consciousness because they show that, in the words of one group of researches, "wake and sleep are not mutually exclusive states, and that sleep is not necessarily a global brain phenomenon."
I was away from the computer a lot by the time I started typing this. But I'll post more tomorrow after I'm done buying books. I'll look for some on dreaming. :)