Brain decoding: Reading minds By scanning blobs of brain activity, scientists may be able to decode people's thoughts, their dreams and even their intentions. · Kerri Smith1 23 October 2013"See how scientists decode vision, dreamscapes and hidden mental states from brain activity. Jack Gallant perches on the edge of a swivel chair in his lab at the University of California, Berkeley, fixated on the screen of a computer that is trying to decode someone's thoughts. · Deep-learning computers close in on artificial intelligence On the left-hand side of the screen is a reel of film clips that Gallant showed to a study participant during a brain scan. And on the right side of the screen, the computer program uses only the details of that scan to guess what the participant was watching at the time. Anne Hathaway's face appears in a clip from the film Bride Wars, engaged in heated conversation with Kate Hudson. The algorithm confidently labels them with the words 'woman' and 'talk', in large type. Groups around the world are using techniques like these to try to decode brain scans and decipher what people are seeing, hearing and feeling, as well as what they remember or even dream about. Neuroscientists can predict what a person is seeing or dreaming by looking at their brain activity. Russell Poldrack, an fMRI specialist at the University of Texas at Austin, says that decoding allows researchers to test existing theories from psychology that predict how people's brains perform tasks. “There are lots of ways that go ,,” he says. In early studies1, 2 scientists were able to show that they could get enough information from these patterns to tell what category of object someone was looking at — scissors, bottles and shoes, for example. “We were quite surprised it worked as well as it did,” says Jim Haxby at Dartmouth College in New Hampshire, who led the first decoding study in 2001. The same is true for dreams. Kamitani and his team published their attempts at dream decoding in Science earlier this year. They let participants fall asleep in the scanner and then woke them periodically, asking them to recall what they had seen. The team tried first to reconstruct the actual visual information in dreams, but eventually resorted to word categories. Their program was able to predict with 60% accuracy what categories of objects, such as cars, text, men or women, featured in people's dreams. Decoding relies on the fact that correlations can be established between brain activity and the outside world. ; Haxby, J. V. et al. Science 293, 2425–2430 (2001). 2. Cox, D. D. & Savoy, R. L. et al. NeuroImage 19, 261–270 (2003). 3. Haynes, J.-D. & Rees, G. Nature Neurosci. 8, 686–691 (2005).