Can you learn while you sleep?

As a student, I have admittedly entertained the idea of learning by osmosis.  Who wouldn’t want to catch some shut-eye with a textbook as your pillow and absorb all its information overnight?  How many hours of studying would you save if you could listen to your Spanish language lessons while you sleep, and wake up speaking fluently?

Sadly, this never worked.  But researchers have taken the first steps in making this fantasy come true!  A new study in the October issue of Nature Neuroscience by Arzi et al. shows that humans can learn while they are asleep and can act on this knowledge both while still asleep and after awakening the next morning.

It is well known that, during sleep, our brains consolidate and enhance memories that were formed when we were awake, but it was a longstanding belief that we could not learn new information while we are asleep.  This was based on a study in the 1950s in which people were asked to remember almost 100 facts at 5-minute intervals throughout their night of sleep.  Unsurprisingly, not a single subject could recall any fact they were told that night.

The success of the present study lies in the simple nature of their experiment.  While their subjects were asleep, the researchers sprayed volunteers with pleasant (e.g. shampoo) and unpleasant (e.g. rotten fish) odors, and observed that their volunteers took deeper breaths when presented with pleasant odors than with unpleasant ones.  Now that it was clear that sleeping brain could distinguish these odors, each kind of odor was paired with an audible tone.  For example, a pleasant smell was paired with a high-pitched beep, while an unpleasant smell was paired with a low-pitched beep.  The next morning, only the tones were presented, and the researchers found that the volunteers took deeper breaths when presented with tones that had been paired with pleasant odors compared to unpleasant ones.  Amazingly, this learned response could already been seen during the night!

In other words, the volunteers learned this conditioning lesson while they were asleep, and it stayed with them after they had awoken!  Naturally, the volunteers had no recollection of having been presented with odors or tones while they were asleep.

Now that we know that we can learn something while we sleep, it will be interesting to know where the limits of this ability lie.  What can we or can we not learn while we are asleep?  Perhaps there is hope for osmotic learning!

Arzi, A., Shedlesky, L., Ben-Shaul, M., Nasser, K., Oksenberg, A., Hairston, I.S. & Sobel, N. (2012). Humans can learn new information during sleep, Nature Neuroscience, 15 (10) 1465. DOI: 10.1038/nn.3193
Images adapted from Shutterstock and Stickgold, R. (2012). To sleep: perchance to learn, Nature Neuroscience, 15 (10) 1323. DOI: 10.1038/nn.3223

Kate Fehlhaber

Kate graduated from Scripps College in 2009 with a Bachelor of Arts degree in Neuroscience, completing the cellular and molecular track with honors. As an undergraduate, she studied long-term plasticity in models of Parkinson’s disease in a neurobiology lab at University of California, Los Angeles. She continued this research as lab manager before entering the University of Southern California Neuroscience graduate program in 2011 and then transferring to UCLA in 2013. She completed her PhD in 2017, where her research focused on understanding the communication between neurons in the eye. Kate founded Knowing Neurons in 2011, and her passion for creative science communication has continued to grow.