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 sensation…
It'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 life… but 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.