Scientists at the University of California, Berkeley, have developed a method capable of decoding the patterns in visual areas of the brain to determine what someone has seen. Specifically, they used functional magnetic resonance imaging to record activity in the visual cortices of volunteers while they viewed a series of images. The researchers could then infer what image a person was seeing by monitoring activity in different sections of the brain and deciphering what information would most likely be found in the corresponding part of the visual field. The method, however, is limited to deciphering information that can be clearly represented mathematically, such as pictures, sounds and movements. The work showed up March 5 in Nature online.