Placeholder Image

Subtitles section Play video

  • Why is it when I fall asleep I get all twitchy? Am I dying?! Am I trying to escape? Are ghosts

  • tickling me?!

  • You know when someone next to you is falling asleep, and they twitch? Or when YOU'RE going

  • to sleep and you feel that falling sensationIt's a thing, and it's normal. Humans twitch

  • involuntarily as they're moving from consciousness into unconsciousness -- called the hypnogogic

  • state. 60-70 percent of people have these twitches, but they usually don't remember

  • actually having them, because they're asleep! That makes them really difficult to study,

  • but that doesn't stop sleep scientists!

  • Science refers to sleep twitching as myoclonus (my-AH-klen-us), and the actual twitch itself

  • is called a hypnagogic jerk. There's no sleep switch in the brain. When you're awake, your

  • conscious brain is in control, and as you fall asleep, the unconscious processes are

  • taking over. Like a shift change at a factory, the handoff has lots of little things that

  • have to go right for the brain allow sleep to set in. Two parts of the middle of the

  • brain handle this transition, the reticular activating system (RAS), and the ventrolateral

  • preoptic nucleus (VLPO). They're in the middle of the brain, next to each other, right behind

  • the eyes. The RAS handles awakeness and the transition to sleep. The VLPO controls you

  • when you ARE asleep. The RAS and the VLPO are the factories handing off to each other,

  • in my earlier analogy.

  • During this transition, the brain stops sending out serotonin. You've probably heard of that

  • chemical, serotonin is what helps keep us happy, low levels of serotonin are an indicator

  • depression. But, serotonin ALSO helps us control our large muscles -- the ones in our arms,

  • and legs so we don't move too much -- but serotonin doesn't control tiny muscles in

  • our wrists, eyes and lips. 90 minutes into sleep, two neurotransmitters GABA and glycine,

  • work together to paralyze you so you don't get up and run around in real lifebut

  • during that waking-sleeping handoff you're not there yet.

  • So, one hypothesis says the twitches come because you're starting to dream, but aren't

  • fully paralyzed. Your RAS is struggling with the VLPO, the serotonin levels are dropping,

  • body processes are being handed over, and the hypnagogic jerk is a symptom of misfiring

  • nerves as these two fight it out. An evolutionary hypothesis says this was a way to wake our

  • primate ancestors before they fell out of a tree -- because the jerk, also known as

  • a sleep start, causes muscles to react quickly.

  • In the end, we're not EXACTLY sure what's happening. But we DO know, that severe twitches

  • CAN be a sign of Parkinson's or Alzheimer's, the result of a brain injury, nerve damage

  • or fibromyalgia, but that's usually if it's a lot of SERIOUS twitching.

  • A new study in Current Biology says the twitches help baby's brains learn how to move their

  • limbs more accurately. They found the brain activity of anaesthetised rats was more vigorous

  • during sleep movement than during actual, awake movement! The researchers determined

  • it was the brain practicing and learning how to make their limbs move properly. So maybe

  • these twitches are a holdover? Who knows. More research is needed for sure.

  • Did you ever twitch so hard you woke up?! Sometimes I remember my twitches, it's weird.

Why is it when I fall asleep I get all twitchy? Am I dying?! Am I trying to escape? Are ghosts

Subtitles and vocabulary

Click the word to look it up Click the word to find further inforamtion about it