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Scientists are starting to understand how our brains make dreams. A new study suggested that dreaming is accompanied by a distinctive pattern of brain activity. And as NPR's Jon Hamilton reports, that brain activity can hint at what people are dreaming about.
JON HAMILTON, BYLINE: The average person has about five dreams each night and usually doesn't remember any of them. So Francesca Siclari from Lausanne University Hospital in Switzerland used a special technique to help several dozen volunteers recall their dreams.
FRANCESCA SICLARI: They went to bed. And every now and then, about every 15 to 30 minutes, we woke them up with a computerized alarm sound.
HAMILTON: Siclari says the idea was that people would be much more likely to remember a dream when it was still fresh. And sure enough, people in the study were able to recall dreams about riding a bicycle, seeing geometric shapes and smelling perfume. Then Siclari and a team of researchers went back and looked at high definition recordings of electrical activity in the volunteers' brains.
SICLARI: When subjects were having experiences during sleep, there was one region of the brain - a region in the back of the brain - that tended to be very active, as if this region was a little bit more awake than the other ones.
HAMILTON: Siclari says activity in this hot zone corresponds with dreaming more than 90 percent of the time. And activity in other parts of the brain offered hints about what the person had been dreaming about. For example, Siclari says when someone's dream included a face, there was activity in a part of the brain used to recognize faces.
SICLARI: So we could really find a very close correspondence to the brain areas that are active when we dream about things compared to brain areas that are active when we see or perceive things during wakefulness.
HAMILTON: The research appears in the journal "Nature Neuroscience." And Robert Stickgold of Harvard Medical School says it confirms something other studies have suggested.
ROBERT STICKGOLD: We're using our brains the same way when we're dreaming that we use to carry out those same functions when we're awake.
HAMILTON: But Stickgold isn't convinced that measuring activity in the back of the brain is a sure way to detect dreaming. He says even people who are woken up every half hour probably don't remember every dream.
STICKGOLD: What they're really measuring is what's happening before you wake someone up and the person remembers having been dreaming.
HAMILTON: And it's possible that forgotten dreams have a different electrical signature in the brain. Even so, Stickgold thinks this sort of research has the potential to help scientists understand not only dreaming but an even greater mystery - consciousness. When we sleep, our brains repeatedly cross the boundary between unconsciousness and dreaming, which researchers consider a form of consciousness. Stickgold says the question is how does the brain move back and forth all night?
STICKGOLD: And it's not that different from the question of what happens when we wake up and become fully conscious. That's a phenomenal question that we just don't have an answer to.
HAMILTON: And probably won't for quite a while, but Stickgold thinks more research on dreams could provide some clues. Jon Hamilton, NPR News.
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