Half awake in the middle of the night, you are startled into the sudden awareness that a shadowy figure is above you. Terrified, you try to move or cry out, but the weight of this creature feels to be pushing down your chest, pinning down your whole body, and choking you silent. The creature is humanoid, and the sense of its presence is overwhelming. This lasts seconds, or minutes, but eventually it ends and you are fully awake, alone and scared half to death.
If this sounds familiar, then congratulations, you’ve experienced the sheer terror of a bad case of sleep paralysis. A quirk of the biochemistry of the mind has caused you to become briefly trapped halfway between sleep and reality, and the rational part of your mind usually suppressed during dreaming is freaking the hell out. Sleep research, one of the great frontiers of neuroscience, has only recently developed a model of what might be occurring.
Sleep paralysis occurs only during the transitions between wakefulness and sleep. It is especially likely to occur if you have been altering your sleep cycles, eg. jet lagged, napping at unusual times, or if you are a narcoleptic. Messing with your sleeping patterns increases your chances of waking up during the rapid eye movement (REM) stage of sleep during which dreaming is most vivid. Narcoleptics chaotic sleep patterns cause them to frequently fall directly in and out REM, often without noticing.
For narcoleptics, negative sleep paralysis experiences are frequently reported. 6% of the rest of the population experience frequent sleep paralysis, and 60% experience it occasionally. In surveys from Canada, China, England, Japan and Nigeria, 20 to 60% of individuals reported having experienced sleep paralysis at least once in their lifetime
It is specifically the borderland between REM and awake, between dreams and the real world, where you can accidentally get stuck into some interesting brain glitches. During REM a part of the front brain called the dorsolateral prefrontal cortex, linked to planing and thinking logically, is turned off. This is why dreams have such a unique, non-lineal, illogical flavour – and why we don’t question it during the dream. But to prevent us acting out our vivid, illogical, dreams during REM, our brain paralyses our body. Incidentally, it is a failure of this mechanism that causes sleep walking.
So far we have an excellent mechanism to explain sleep paralysis. A person moving to or from a REM state incompletely could experience a situation where they feel that are completely awake, but experience full body paralysis, combined with the illogical hallucinatory suggestibility of dreaming. A potent mix for a terrifying nightmare about being ‘crushed’.
The neuroscientist Baland Jalal specialises in studying sleep paralysis and thinks there might be a further piece to this puzzle. Another part of the brain, the temporoparietal junction, also experiences diminished activity during REM. This area has been shown to be critical in the brain’s ability to distinguish the self from others. Disrupting the temproparietal junction in a normal awake person causes strong out-of-body experiences, such as the sensation of floating above your physical self. Diminished activity in the junction is likely why in dreams your perspective is often ambiguously outside of your own body or even of another person.
Jalal thinks that if we wake into sleep paralysis and try to move then our brain has a problem. Due to the paralysis, it is not receiving signals back from the body to confirm that we have moved. The part of the brain responsible for our mental image of our bodies posture and position in space is confused about where we are and assumes the self is roughly nearby, floating above you.
Personally, I’ve frequently experienced the odd sensation of suddenly falling when on the cusp of sleep. Similarly, dreams where I am weightlessly floating. These are both common reactions to the lack of feedback from the body during REM.
In sleep paralysis, as we try to move but receive no feedback, our brains just have to assume that our body has moved. This creates a misleading impression of something floating above us. Jalal thinks our REM-state brain with it’s inability to recognise the self, assumes this is something else, creating the sensation of another person’s body uncomfortably close to us. In a sense, we are getting scared by our own mentally projected shadow.
He argues that it is the combination of all this factors that creates the powerful and terrifying illusion:
…our brain regards it as highly improbable that chest pressure, sensations of suffocation, rapid breathing (which are caused by REM physiology) and on top of everything, seeing a human-like shadow, occur by random chance. When REM dreaming becomes activated as well, the shadowy-figure can take on all kinds of sophisticated shapes and dimensions, and the entire plot thickens. At this point, memory and the narrative abilities of other brain regions, play a role in the evolving hallucination.”
If that’s not strange enough, Jalal’s research has found that your cultural background plays a strong part in severity and frequency of sleep paralysis. Virtually every culture has a myth regarding the cause of sleep paralysis. The myth of the succubus/incubus is one of the better known Western interpretations, a demon believed to climb onto sleepers so as to have sex with them and drain life-force out of them. Indeed, sleep paralysis illusions can involve the sensation of being raped, an unfortunate crossover of arousal and nightmarish sleep paralysis.
Our English word, nightmare, is a specific reference to a sleep paralysis myth. Mare or mara are mythical Scandinavian goblins which ride the chests of sleepers. The painting at the top of the article is a depiction of a mare goblin terrorising a sleeper. In the US the illusory visitor is traditionally known as a night hag, you might be able to defeat it by wiggling your fingers and toes. In Fiji, a dissatisfied deceased relative is trying to eat you. In Thailand, an evil spirit called a pee ahm is holding you down. In Italy, a cat-like creature known as the pandafeche has you in its grasp. In Egypt, a jinn may be hunting you and failing to deal with it by having your home blessed and reciting religious passages could lead to your death. Some alien abduction stories also fit the scenario, with odd creatures pinning you and experimenting. And there are many more in cultures all over the world, each sharing the common elements of a creature preventing you moving and/or suffocating you during the night.
Of course these myths are self-reinforcing, as a suggestive sleepers mind is prone to interpret sleep paralysis in accordance with their cultures’ mythic explanation. Oddly in Denmark, the scientific explanation of sleep paralysis is relatively well known. Jalal found by comparing the experiences of Egyptians, for whom an encounter with a jinn could mean death, and the Danes, for whom it meant nothing much, that sleep paralysis was more frequent and much longer lasting for Egyptian sufferers. Jalal concluded that for people who believed strongly in the mythic negative connotations of the event, it became a self-reinforcing loop whereby the fear and terror interfered with their sleep, leading to impaired sleep and creating an increased likelihood of paralysis occurring. Fear may also prolong the paralysis.
In other words, a solution to recurring sleep paralysis can be simply understanding what is actually occurring and thus knowing not to worry too much during and after the event. Jalal also advocates using sleep paralysis as an opportunity to slip into lucid dreaming. Lucid dreaming, being aware you are in a dream and taking control, is very close to sleep paralysis. Jalal suggests that if someone is able to calm themselves during a sleep paralysis attack, then they can take control and start to shape the dream world to whatever they want.
I discovered some interesting new words researching this article:
Hypnopomp – is the state leading out of sleep into wakefulness, the opposite of:
Hypnagogia – the state leading from wakefulness into sleep.
Eigengrau – German for ‘intrinsic grey’. The uniform dark grey background distinguishably lighter than black, which many people report seeing in the absence of light. Also called dark light, or brain grey.
So, “In a hypnagogic state last night the whole room seemed eigengrau.”, is a thing you could say if you were at a neuroscientists’ party, and a bit of an asshat.