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, scientists 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.
They then woke up the dreamer and asked him or her 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.
Researchers were then able to predict what images the volunteers had seen with a 60% accuracy rate, rising to more than 70% 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.
"I believe it was a key step towards reading dreams more precisely," Kamitani said.