So, you know what I am talking about: the time when you are just about to fall blissfully asleep and you suddenly feel like you’re falling as if someone threw you off a tree!
According to scientists there are 60-70% people who experience this falling sensation and then twitch and jerk in their sleep. Science refers to any such involuntary jerking of our muscles as myoclonus.
This type of myoclonus that causes you to twitch in your sleep is called a hypnagogic jerk. It happens just as you are transitioning between the state of consciousness and unconsciousness. These jerks are quite common and perfectly normal. Many people often sleep through these jerks without even knowing it, as these twitches sometimes go unremembered, especially when they don’t cause a person to wake up.
The Cause Explained
Sci Show explained the basics of it, I’ll explain this in depth. The two parts in the middle brain, right behind the eyes, which handle these transitions are: –
1. Reticular Activating System (RAS): handles body function while its conscious and transitioning to sleep
2. Ventrolateral Preoptic Nucleus (VLPO): controls the body while asleep
During the sleep transition period the brain stops sending out serotonin (a chemical that keeps us in a good mood) that helps us control our larger muscles like arms and legs (smaller muscles being eyes, wrists, etc.) so that we do not move too much while asleep.
During that sleeping-waking hand-off when you are not quite asleep yet, the body twitches because it has started to dream but hasn’t yet completely lost motor function. While you are moving around in the half-asleep dream, the RAS is struggling with the VLPO. Serotonin levels are dropping, body processes are in the process of being handed over to VLPO, but the dream makes your half asleep muscles move (or cause a hypnagogic jerk). A hypnagogic jerk is the symptom of nerves misfiring as these two systems are in the process of transferring body control.
Another theory says that this mechanism was used to wake our primary ancestors before they fell out of trees while sleeping on the branches. The brain primarily misinterprets relaxation as an indication that the being is falling out of a tree and this causes the muscles to quickly react to catch us from falling.
These hypnagogic twitches also help babies to move their limbs more often, maintaining muscle activity, since babies seldom move these muscles while conscious.
Severe twitches can be a sign of Parkinson’s disease, result of a brain injury or nerve damage or due to stress, anxiety, caffeine and sleep deprivation. If it’s severe, you know it’s time to see a doctor!