A 'Hot Zone' In The Brain May Reveal When, And Even What, We Dream | KUOW News and Information

A 'Hot Zone' In The Brain May Reveal When, And Even What, We Dream

Apr 10, 2017
Originally published on April 11, 2017 6:28 am

Most of us have about five dreams each night, though we're not likely to remember any of them.

But a team of researchers has found a pattern of brain activity that seems to reveal not only when the brain is generating a dream but something about the content of that dream.

"When subjects were having [dream] experiences during sleep, there was a region in the back of the brain that tended to be very active, as if this region was a little bit more awake," says Francesca Siclari, a researcher at the Center for Research and Investigation in Sleep at Lausanne University Hospital in Switzerland.

Patterns of brain activity in this region also suggested whether the dream included a face or movement, Siclari and a team of researchers at the University of Wisconsin-Madison report in Nature Neuroscience.

The team found that dreams occurred during both rapid eye movement — REM — and non-REM sleep. But there were also periods of deep sleep in which dreaming did not occur.

The team studied dreams by monitoring electrical activity in the brains of 32 people as they slept.

Participants were awakened frequently and asked to report whether they'd been dreaming. This reduced the problem of people forgetting dreams over the course of a full night's sleep.

And sure enough, people in the study were able to recall not only whether they had been dreaming but often what they had been dreaming about. Dreams included riding a bicycle, seeing geometric shapes in motion and smelling perfume.

After a person reported a dream, the investigators went back and reviewed brain activity patterns recorded with a technique known as high-density electroencephalography. This allowed researchers to connect dreaming with a decrease in low-frequency activity and an increase in high-frequency activity at the back of the brain.

By looking for this electrical signature in the brain, the researchers were able to predict when a person had been dreaming about 90 percent of the time.

In a smaller study, the researchers looked at activity in areas of the brain that respond to specific stimuli, like seeing a face, hearing speech or perceiving movement. Activity in these areas during dreams offered hints at what the person had been dreaming about.

For example, when someone's dream included a face, there was activity in a part of the brain used to recognize faces. And when a dream involved a sense of movement, there was activity in an area that is involved in the perception of movement.

There was "a very close correspondence [between] brain areas that are active when we dream about things compared to brain activities that are active when we see or perceive things during wakefulness," Siclari says.

"We're using our brains the same way when we're dreaming that we use [them] to carry out those same functions when we're awake," says Robert Stickgold, an associate professor of psychiatry at Harvard Medical School, who was not involved in the study.

But Stickgold isn't convinced that measuring activity in the back of the brain is a sure way to detect dreaming. Even people who are awakened every half-hour probably don't remember every dream, he says.

"What they're really measuring is what's happening before you wake someone up and the person remembers having been dreaming," Stickgold says. 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 shift into a state of activity where we're dreaming, as opposed to having dreamless sleep?" he says.

Finding an answer to that question, Stickgold says, could help scientists understand how the brain becomes fully conscious when we wake up each morning.

"That's a phenomenal question that we just don't have an answer to," he says.

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AUDIE CORNISH, HOST:

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.

(SOUNDBITE OF SIRISWAD SONG, "INSPIRATIONAL FRIENDS") Transcript provided by NPR, Copyright NPR.