It may now appear to be just the stuff of science fiction, but scientists say a mind-reading device is inching its way ever closer to reality.
In fact, an international team claims to have already showed it could tell what someone was hearing just by decoding their brain waves, a breakthrough which may lead to an implant that can interpret imagined speech in patients who can't talk.
In their research, the scientists demonstrated that the brain breaks down words into complex patterns of electrical activity, which can be decoded and translated back into an approximate version of the original sound. And, as the brain is believed to process thought in a similar way to sound, the research offers hope to thousands of brain-damaged patients who are not being able to communicate with their loved ones, 'The Daily Telegraph' reported.
Prof Robert Knight, one of the researchers from the University of California at Berkeley, said: "This is huge for patients who have damage to their speech mechanisms because of a stroke or Lou Gehrig's disease and can't speak. "If you'd eventually reconstruct imagined conversations from brain activity, thousands of people could benefit."
For their research, the scientists analysed 15 epilepsy patients who were undergoing exploratory surgery to find the cause of their seizures, a process in which electrodes are connected to the brain through a hole in the skull. While the electrodes were attached, the scientists monitored activity in the temporal lobe -- a speech-processing area of the brain -- as the patients listened to five to 10 minutes of conversation.
By breaking down the conversation into its component sounds, they were able to build two computer models which matched distinct signals in the brain to individual sounds. Subsequently, the team tested the models by playing a recording of a single word to the patients, and predicting from the brain activity what the word they had heard was.
The better of the two programmes was able to produce a close enough approximation of the word that the scientists could guess what it was, from a list of two options, 90 per cent of the time, the 'Public Library of Sciences Biology' journal reported. Dr Brian Pasley, who led the study, compared the method to a pianist who could watch a piano being played in a soundproof room and "hear" the music just by watching the movement of the keys.
He said: "This is just to understand how the brain converts sound into meaning, and that is a very complicated process. The clinical application would be down the road if we could find out more about those imaginary processes." An expert, Prof Jan Schnupp, at Oxford University, has described the findings as "remarkable".
He said: "Neuroscientists have long believed that the brain essentially works by translating aspects of the external world, such as spoken words, into patterns of electrical activity. "But proving that this is true by showing that it is possible to translate these activity patterns back into the original sound is nevertheless a great step forward."