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Understanding our dreams is one of the most elusive goals in science. But now, here's a headline that is not science fiction: Researchers have developed a technique for observing what people are dreaming.
NPR's Rob Stein tells us more.
ROB STEIN, BYLINE: For centuries, philosophers, poets, psychologists and others have been fascinated by dreams. But Jack Gallant, a neuroscientist at Berkeley, says solving the mystery of our dreams is one of the toughest problems out there.
JACK GALLANT: The question of what we can know about our psyches from knowing what we dream is a long-standing question. In psychology and neuroscience, there's been 100 years of argument about whether dreams are important or unimportant. We don't really know, because we really haven't had very good access to peoples' dreams.
STEIN: We don't have very good access because we have to rely on how people describe their dreams, often as they're already slipping away.
GALLANT: Because of the nature of dreams, we find it very difficult to remember our dreams and to sort of describe them well. So the idea is you could perhaps build a dream decoder that would allow you to inspect your dreams after you had them and sort of interrogate them and figure out, you know, what you were dreaming about.
STEIN: And now, scientists in Japan are reporting that they have taken a step toward doing just that. Yukiyasu Kamitani is a neuroscientist in Kyoto who led the work.
YUKIYASU KAMITANI: We built a decoding program for the decoding of dream content, by analyzing brain activity during sleep.
STEIN: Here's how Kamitani's team built their dream decoding program. First, they conducted brain scans over and over and over again on three volunteers, just as they were starting to dream.
KAMITANI: We focused on dream experience which can be detected just a few minutes after the sleep onset.
STEIN: The researchers woke up the study subjects repeatedly to ask them to describe their dreams. So they could start to figure out which patterns of brain activity matched specific parts of their dreams.
KAMITANI: Many of them were just about daily life - in office or home - but some were, you know, funny, bizarre, you know, experience.
STEIN: Including one man who dreamed he was having dinner with a famous Japanese movie star.
The scientists then did more brain scans while the volunteers were awake, so they could tweak their decoding program.
KAMITANI: We used that to train the decoder.
STEIN: Then they put their decoder to the test, scanning subjects' brains while they were dreaming to see if they can tell what was going through their minds. And in a paper being published in this week's issue of the journal Science, the researchers report that they were often able to match certain brain activity to certain objects, like a chair, a window or a man.
KAMITANI: Our result shows that we can predict what a person is seeing during dream. The result suggest that it may be possible to read out dream contents, even when you don't remember just by, you know, looking at brain activity.
STEIN: Neuroscientist Jack Gallant calls the research a technologic tour de force and says the ultimate decoder would provide vivid, detailed, representations of our dreams.
GALLANT: If you could build the perfect dream decoder, it would create a movie on your television screen and would just replay your dreams. It would replay all the actions that happened, the actors, the people involved, and it would replay the sound.
STEIN: We're nowhere near that yet, but Gallant says this latest research is a milestone in starting to try to understand our dreams.
GALLANT: In this field of dream decoding, no one has managed to successfully do this before. So this is - it's not the final step down this road, it's the first step.
STEIN: A small step towards revealing why we dream and what our dreams really mean.
Rob Stein, NPR News. Transcript provided by NPR, Copyright NPR.