Ah Sleep! Apart from perhaps enjoying a favourite meal in good company I doubt whether there are any more enjoyable things to than to drift off into a deep refreshing sleep after a long day. The other night I found that I kept waking up soon after nodding off. Have you noticed when you’re drifting off to sleep sometimes you wake up with a startle?
I’m sure we’ve all probably experienced that horrible feeling: something similar to falling or the intangible feeling that something terrible has just happened. Your arms and legs might jerk or violently and pity anyone else who might be in the same bed as you.
But what on Earth is going on? Isn’t sleep supposed to be something relaxing and an opportunity for your brain and mind to rejuvenate and reset itself?
What you are experiencing is entirely normal and has an impressive sounding name. Smugly impress your friends next time you are enjoying a coffee/ glass of wine/beer [insert preferred drink] in your local coffee-shop/pub/park [insert preferred social meeting venue] by telling them all about what we call a “hypnagogic jerk”!
No-one seems to know why exactly why these jerks occur although its likely to be due to a mysterious part of the brain called the ‘reticular activating system’. This is an important part of the brain that keeps us awake and conscious: It is spread across the bottom of the brain and as long as you are alive it is always working. It keeps us awake and alert during the day and monitors our surroundings to make sure that no harm comes to us when we’re asleep. If something (like a loud bang) were to happen in the while you’re in the land of ‘nod’ the reticular activating system wakes up the rest of your brain.
Normally when we drift off to sleep, all our muscles start to relax and it seems that the reticular activating system part of the brain wrongly interprets this: for some reason the reticular activating system thinks “Arms and legs getting loose and floppy – help I must be falling!” – quick wake up!”. The reticular activating system sends out emergency ‘wake up!’ impulses to the rest of the brain and you wake up with a startle.
The Tetris Effect
This isn’t the only odd thing to happen when we try to get to sleep. Have you ever been concentrating on something hard during the day or solving a puzzle/problem and then when you try to fall asleep you can see the same problem or puzzle vividly in your mind? I first noticed after long sessions of playing computer games.
This phenomenon has been studied by scientists who chose to look at the effect of the computer game Tetris. They discovered that after playing for several hours nearly everyone experiences visions of blocks lining up and arranging themselves as they try to sleep. They named it the ‘Tetris effect’. If people were then woken up early on in their sleep then they were also dreaming about Tetris blocks!
What is happening during this time and in your dreams your mind is trying to ‘solve’ the problem better and is working out more efficient ways of lining up those blocks. People who slept better learnt how to become better at playing Tetris. (Phillips, H, 1999, Stickgold et al, 2000)
So if you want to learn something new or be better at some skill (be it playing the piano or flying a plane) then the bottom line is that good quality sleep counts!
Further Reading on Sleep:
A very comprehensive and academic look at everything sleep related: http://www.icmr.nic.in/ijmr/2010/february/0203.pdf
Phillips, H (1999) Perchance to Learn. New Scientist 163(2205): pp. 26-30
Stickgold, R., Malia, A., Maguire, D., Roddenberry, D., & O’Connor, M. (2000). Replaying the game: Hypnagogic images in normals and amnesics. Science 290: 350-353