The human brain is so complex that we’ve never been 100% sure we understand everything about it. Even when they think they have the answer to something, researchers are still cautious about their findings. And this fact especially applies to the mystery that is the sleeping brain.
Sure, we have a measured understanding of sleep cycles thanks to fMRI scans, but we still don’t know why certain things happen. And when it comes to sleep syndromes and phenomena, the mystery deepens precisely because there are no set answers for why the sleeping brain works when it’s healthy.
Here are 11 mysterious sleep-related phenomena (some of which you probably didn’t know about):
1. Hypnagogic jerk. Before you start dreaming, your body is usually paralyzed, so it doesn’t act out a dream. But on some occasions, you might start dreaming before your body is fully “unplugged.”
During a hypnagogic jerk, your body might react to a sudden movement like falling or tripping. Like with anything involving the complexities of the brain, researchers aren’t sure why this happens.
2. Sleep paralysis. For centuries, cultures around the world have tried to explain this phenomenon using supernatural answers. It happens when the mind wakes up during REM sleep (when the body is at its most relaxed, to the point of being paralyzed).
But researchers only know when it happens, not why. Today, it’s believed that one in four people will experience sleep paralysis. Symptoms include breathlessness, inability to move or speak, a sense of dread, and in some cases, hallucinations.
3. Sleepwalking. This disorder involves waking up in the middle of the night and doing all sorts of activities. It’s a terrifying affliction because the person doesn’t remember that they did it, and in some cases, they can hurt themselves.
The causes of sleepwalking are a mystery. You’re more propense to be a sleepwalker if it runs in your family, but researchers still don’t understand how or why it originates in the brain.
4. Sleep talking. Also known as somniloquy, this is a disorder where a sleeping person talks. The things they say can range from mumbling to shouting, to long and complicated rants.
5. Nocturnal sleep-related eating disorder (NSRED). Also known as sleep eating, this is a type of sleepwalking that’s closely tied to a person’s conscious wants and desires for food.
It’s considered to be both a sleep disorder and an eating disorder because the person is fulfilling a desire they suppress while they’re awake. Like with sleepwalking, the person doesn’t realize they’re eating and they can’t remember any of it the next day.
6. Night terror. The difference between a night terror and a nightmare is that a night terror involves specific actions. Night terrors involve screaming, panic, sleep walking and thrashing around on the bed.
Like most sleep disorders, it’s believed to be congenital. However, no one understands why it happens other than the fact that it gets inherited and it’s mostly children who experience it.
7. Exploding head syndrome. This painless syndrome involves a person hearing an explosive noise before they fall asleep. It can sometimes feel like an explosion is taking place inside the person’s head.
It’s considered a type of sleep disorder and an unusual type of hallucination that happens to people who are in between being asleep and awake. The causes are unknown.
8. An out-of-body experience (OBE). While this isn’t a sleep disorder, it’s still interesting to note. An OBE involves the feeling of “floating” or “observing” one’s body from the outside.
Out-of-body experiences are unrelated to sleep disorders. Researchers classify it as a dissociative experience with psychological and neurological causes. It has nothing to do with the “spirit” leaving the body, and it’s most likely due to a temporary brain malfunction (Hines, 2003).