Scientists in Japan said Friday they had found a way to "read" people's dreams, using MRI scanners to unlock some of the secrets of the unconscious mind.
Researchers have managed what they said was "the world's first decoding" of night-time visions, the subject of centuries of speculation that have captivated humanity since ancient times.
In the study, published in the journal Science, researchers at the ATR Computational Neuroscience Laboratories, in Kyoto, western Japan, used magnetic resonance imaging (MRI) scans to locate exactly which part of the brain was active during the first moments of sleep.
The scientists then woke up the dreamers and asked them what images they had seen, a process that was repeated 200 times.
These answers were compared with the brain maps that had been produced by the MRI scanner, the researchers said, adding that they later built a database, based on the results.
On subsequent attempts they were able to predict what images the volunteers had seen with a 60 percent accuracy rate, rising to more than 70 percent with around 15 specific items including men, words and books, they said.
"We have concluded that we successfully decoded some kinds of dreams with a distinctively high success rate," said Yukiyasu Kamitani, a senior researcher at the laboratories and head of the study team.
"Dreams have fascinated people since ancient times, but their function and meaning has remained closed," Kamitani told AFP. "I believe this result was a key step towards reading dreams more precisely."
His team is now trying to predict other dream experiences such as smells, colours and emotion, as well as entire stories in people's dreams.
"We would like to introduce a more accurate method so that we can work on a way of visualising dreams," he said.
Kamitani, however, admits that there is still a long way to go before they are anywhere near understanding a whole dream.
He said the decoding patterns differ for individuals and the database they have developed cannot be applied generally, rather it has to be generated for each person.
The experiment also only used the images the subjects were seeing right before they were woken up. Deep sleep, where subjects have more vivid dreams, remains a mystery.
"There are still a lot of things that are unknown," he added.
Kamitani's experiment is the latest in a government-led brain study programme aimed at applying the science to medical and welfare services, government officials said.
"Our expectations from the dream study are quite high," said an official of the science and technology ministry's brain research promotion programme.
The ministry spent around 3.4 billion yen ($35 million) on the dream and other neuroscience studies for the fiscal year that ended on March 31.
"This technology may help disabled people to be able to move artificial limbs with their brain, or it may lead to a remedy for dementia or other brain-related diseases in the future," the official said.
"But we are looking carefully at the ethical aspects of the technology, which may allow a third person to look at somebody else's thoughts in the future," she said.
In 2011, a team of researchers at the University of California, Berkeley, used an MRI system to capture images from the brains of subjects who were awake and later reconstructed them as video clips.