Wednesday, 1 August 2012

Learning in Your Sleep

Imagine climbing into bed, turning off the light, and shutting your eyes.  As you drift off to sleep, a small machine monitors your brainwaves, and when it indicates that you have entered a stage of deep rest known as slow-wave sleep, a Mozart sonata begins to play softly.  You’ve spent a solid hour practicing this sonata during the day, and while it plays repeatedly during your slumber, the memory trace laid down in your brain during that practice session becomes reactivated in both the auditory and motor parts of the brain.  In the morning, unaware of your nighttime “practice session”, your performance of the sonata is significantly improved.

I would normally be highly skeptical of this type of claim.  It reminds me of that scene in Huxley’s Brave New World where children listen to history lessons in their sleep, instead of having to go to school.  It sounds like new age mumbo-jumbo to me.

Except that this exact type of learning effect has been shown by researchers at Northwestern University and published in this month’s issue of Nature Neuroscience.  The experiment was straightforward:  Sixteen people learned to play two short melodies on the piano, and then had a 90 minute nap.  When they entered slow-wave sleep, one of the melodies was quietly played twenty times.  After the nap, performance on the melody that had been played during the nap was significantly improved compared to the melody that wasn’t played.

This study brings together two interesting aspects of music learning.  The first is the role of sleep in aiding learning.  Previous studies have shown that memory consolidation during sleep is an important source of improvement between practice sessionsThe second aspect is the importance of sensorimotor integration in learning to play an instrument.  During practicing, our brains learn to associate the sounds we produce (the auditory feedback) with the movements that lead to those sounds. The auditory and motor parts of our brains become more highly linked, so that just hearing a song that we know how to play activates motor parts of the brain, and just making the movements associated with playing a song (like pressing the keys of an unplugged keyboard) causes auditory parts of the brain to light up.  This is why hearing the music in our sleep can cause improvements in our motor performance:  the replaying of the song reactivates the auditory memory, which simultaneously reactivates the motor memory, strengthening both these memories and their association with each other.

So, am I going to start listening to piano music in my sleep?  I’m certainly considering giving it a try.  There are a few possible caveats to the potential gains here.  First, music might interfere with sleep.  In the research study, there were a couple of subjects who did wake up while the music was playing, so this could definitely be a downside.  Another issue to consider is that the music should probably be played during slow-wave sleep, as it was in the research study, to have maximum effect (although the effects of playing music during other stages of sleep have yet to be examined).  Most people (myself included) don’t keep track of when they are in deep sleep.  However, there are iphone apps that claim to monitor stages of sleep (usually these aim to waken you during light sleep) and these could potentially be adapted to trigger music during deep sleep.  A third issue is that the effect on music motor learning might simply be a bias instead of an absolute gain in learning.  What this means is that listening to one song might improve performance on that song at the expense of other songs being learned.  In the research study, the melody that was played during sleep improved 7.9%, while the other melody only improved 2.6%.  Meanwhile, for people who didn’t have either melody played during their sleep, both melodies improved about 4.4%.  Perhaps there is a limit to how much improvement can happen during sleep: listening to the one melody caused it to be improved but maybe also caused the other melody to improve less.

In any case, it sounds like a fun summer project and I do have a couple of piano pieces I’m trying to learn, so why not?  Sweet dreams!


Antony, J.W., Gobel, E.W., O’Hare, J.K., Reber, P.J., and Paller, K.A. (2012). Cued memory reactivation during sleep influences skill learning. Nature Neuroscience 15, 1114–1116.