While You Were Sleeping

As students all over the globe head back to school, we imagine many of them are looking for ways to make learning a little easier and studying a little less onerous. Imagine, for example, how cool it would be if you could study for that upcoming chemistry exam while you were sleeping?

Sadly, that’s not yet a reality. But, as SRxA’s Word on Health learned this week, scientists are getting closer to understanding sleep learning.

Older studies of sleep learning (think of the old tape recorder-under-the-pillow experiments) pretty much failed to demonstrate that it’s possible to absorb information while sleeping. In most cases the trials themselves were flawed. In some cases the subjects were briefly woken during the trials, or else they took place during unnatural sleep, with the subjects drugged.

More recently however, a number of studies have suggested that there may be some sort of connection between sleep and learning and memory consolidation. Anat Arzi, a PhD student working with Prof. Noam Sobel  at the Weizmann Institute of Science in Israel was intrigued and set out to find the right teaching method. “In spite of all the previous research, we thought that some kind of sleep learning should be possible. The question was: which kind?”

Tones and smells turned out to be ideal. They don’t wake the sleepers, yet they are sensed during sleep. And sniffing – the reflexive response to the odors – occurs whether asleep or awake. That meant that instead of relying on reported memories, the researchers only had to watch for the long, deep sniff we automatically take when we smell a good smell, or the short, shallow one associated with a bad smell. When this occurred they knew that their subjects had been conditioned to associate a tone with a particular odor – even though the subjects themselves had no recall, whatsoever, of the “lesson” they had learned while asleep.

Imagine that you wake up in the morning feeling nothing special, yet you find yourself inexplicably behaving just a bit differently during the day. For example, you take a sniff every time you hear a tone,” said Sobel.

This may be the first incontrovertible demonstration of sleep learning in human adult brains.

So what’s next? Sobel and Arzi found that the conditioning is best retained when it takes place during non-REM sleep and plan to explore this further.  Whether or not they find the magic connection that will one day enable us to memorize the periodic table as we sleep, finding proof for one type of sleep learning suggests that others might be possible.