Brain learns while you snooze
Sleeping mind can make associations between smells and sounds By Laura Sanders
Web edition: August 29, 2012
Print edition: October 6, 2012; Vol.182 #7 (p. 9)
Even while in a deep slumber, people can still learn brand new information. Sleepers soak in new associations between smells and sounds, knowledge that lingers into the next waking day, researchers report online August 26 in Nature Neuroscience.
The new study is the first to show that entirely new information can creep into the sleeping mind, says study coauthor Anat Arzi of the Weizmann Institute of Science in Israel. Sleep used to be considered a kind of reversible death, she says. “But the brain is not passive while you sleep. It’s quite active. You can do quite a lot of things while you are asleep.”
But before overtaxed students rejoice, the results don’t mean that Spanish vocabulary tapes now have a place on the nightstand. Researchers have tried and largely failed to find evidence that trickier information, such as new pairs of words, can make its way into the brain during sleep.
Instead of trying to teach people something complicated like a new language, Arzi and her colleagues relied on subjects’ sense of smell. As anyone who has walked by a dumpster in July knows, smells can elicit a nose-jerk reaction. Catching a whiff of hot trash automatically makes people inhale less, curbing the size of the inhale. But a scent of fresh bread spurs a long, deep inhale. Arzi and her team took advantage of this sniff reflex for their experiment.
As people slept in the laboratory, the researchers delivered pleasant scent, such as shampoo. As this nice smell crept into the sleepers’ noses, the researchers played a particular tone. Later, a disgusting smell, such as rotten fish or carrion, was paired with a different tone. Neither the smell nor the sound woke people up.
After just four exposures to the smell-tone pair during a single...
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