Excerpt from "Amazing Video Shows Us the Actual Movies that Play in Our Mind," by Alasdair Wilkins, io9, September 22, 2012:
"Researchers at UC Berkeley used functional magnetic resonance imaging (fMRI) and some seriously complex computational models to figure out what images our minds create when presented with movie and TV clips. So far, the process is only able to reconstruct the neural equivalents of things people have already seen, but eventually it might be possible to construct the images people see in dreams and memories.
This could also open up new ways to communicate with those whose speech is severely impaired, such as stroke victims, patients with neurological diseases, and even people in comas. It's probably worth stressing that we're decades away from using this tech to read people's thoughts and intentions, just in case that's something you're worried about.
The researchers developed this technique by showing study participants a series of black-and-white photographs while imaging their minds. By comparing the photographs with the scans, they were able to engineer a way to recognize any image from how the brain responded. With that basic principle in place, it was then only a question of building up a sufficiently complex computer model to decode moving, color images like those in the video above."