Your dreams are no longer safe from the outside - well, kind of. Researchers in Japan have managed to read people's dreams.

Researchers examined three slumbering people's minds with the help of functional magnetic resonance imaging machines (fMRI) and electrical electroencephalography (EEG). The team was led by Yukiyasu Kamitani from the ATR Computational Neuroscience Laboratories.

In the quite elaborate experiment, researchers examined the participants in three-hour blocks over the course of several days. During each block, the participants were awoken between seven to 10 times, every time the researchers saw in their brain scans that they were dreaming, to report what they had dreamt. Then researchers would tell the participants to go back to sleep. The volunteers reported six or seven visual dreams per hour, so altogether, they were able to give the researchers 200 dream reports.

Most of the dreams were about everyday experiences, like riding in their car. From time to time, they were more unusual, like a discussion with a well-known actor. Researchers cobbled together their information to make 20 dream "categories", like male, female, or computer, that made the most frequent appearances in the volunteers' dreams.

Then researchers picked photos that best enumerated the various categories. Volunteers' brains were scanned while they looked at the pictures so that researchers could establish exactly what area of the brain the volunteers were viewing.

The researchers compared the wakeful brain scans with the ones that they had taken when the participants were asleep. They looked particularly at certain portions of the brain: V1, V2, and V3, which are integral to making sense of visual scenes, and perform basic tasks like color contrast; as well as other areas of the brain that perform higher-level visual tasks, like object recognition.

Kamitani said in a presentation given at the Society for Neuroscience's annual meeting earlier this week that the researchers were able to divine whether a man was in the dream, for example, with 75 to 80 percent accuracy.

This study builds on previous research conducted by Kamitani and his colleagues which, in 2008, found that they could reconstruct basic images from brain scans of lower-level visual activity in participants. That study was published in the journal Neuron.

Kamitani hopes to build on the newest research by obtaining the same information from brains during REM sleep, or rapid eye movement. That, he says, will prove to be more difficult because researchers need to wait an hour for participants to descend into that level of sleep.