Sleeping and learning go hand
in hand, studies have shown for years. Even a brief nap can boost your memory
and sharpen your thinking. But the relationship goes deeper than that. In a new
study, scientists report that the brain can actually learn something new during
sleep.
Scientists used to believe that a sleeping brain was taking a break. But it
turns out it can be taught a thing or two, scientists reported in a scientific
journal published in August.
“The brain is not passive while you sleep,” neuroscientist Anat Arzi told
Science News. “It’s quite active. You can do quite a lot of things while you are
asleep.” Arzi researches olfaction, or the sense of smell, at the Weizmann
Institute of Science in Rehovot, Israel. She worked on the new study.
Arzi and her coworkers didn’t try to teach the sleeping volunteers any complex
information, like new words or facts. (So sleeping on top of your study notes
won’t boost your grades.) Instead, the scientists taught snoozing volunteers to
make new connections between smells and sounds.
When we smell something nice, like a flower, we automatically take deep breaths.
When we smell something bad, like the stench of a dumpster, we automatically
take short breaths. These natural reactions maximize our exposure to good smells
and minimize our exposure to bad ones. Arzi and her coworkers based their
experiment on these reactions and the knowledge that our senses don’t turn off
while we slumber.
Once the volunteers fell asleep in the lab, the scientists went to work. They
gave the volunteers a whiff of something pleasant, like shampoo, and at the same
time played a particular musical note. The volunteers didn’t wake up, but they
did hear — and sniff deeply. Then the scientists gave the volunteers a whiff of
something repulsive, like rotten fish, and played a different musical note.
Again, the volunteers heard and smelled — a short snort this time — but didn’t
wake up. The researchers repeated the experiment while the volunteers slept.
After just four repetitions, volunteers made a connection between the musical
notes and their paired smells. When the scientists played the musical tone that
went with good smells, the sleepers inhaled deeply — even though there was no
good smell to sniff. And when the scientists played the musical tone that went
with foul odors, the sleepers inhaled briefly — despite there being no bad
smell.
“They learned what the tone signified,” Arzi concluded.
The next day, the volunteers woke up with the sound-smell connection intact.
They inhaled deeply when hearing one tone and cut their breaths short when
hearing the other. Which must have been odd for them: Imagine walking down the
street and taking a deep breath upon hearing a particular sound!