'Telepathy' breakthrough hailed
A first step has been taken towards hearing imagined speech using a form of electronic telepathy, it has been claimed.
Scientists believe in future it may be possible to "decode" the thoughts of brain-damaged patients who cannot speak.
In a study described by one British expert as "remarkable", US researchers were able to reconstruct heard words from brain wave patterns. A computer programme was used to predict what spoken words volunteers had listened to by analysing their brain activity.
Previous research has shown that imagined words activate similar brain areas as words that are actually uttered. The hope is that imagined words can be uncovered by "reading" the brain waves they produce.
"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," said Professor Robert Knight, one of the researchers from the University of California at Berkeley. "If you could eventually reconstruct imagined conversations from brain activity, thousands of people could benefit."
However, the study involved the use of electrodes inserted through the skull on to the brains of epileptic patients, and a system sophisticated enough to achieve the same result non-invasively remains a long way off.
Scientists enlisted the help of people undergoing brain surgery to investigate the cause of untreatable epileptic seizures, and to pinpoint where the seizures were being generated, neurosurgeons cut a hole in the skull and placed an array of electrodes on to the surface of the brain. In the case of 15 seizure patients, brain activity from the temporal lobe was recorded as they listened to five to 10 minutes of conversation.
Two different computational models were devised to match the spoken sounds to patterns of activity from the electrodes. Patients then heard a single word, and the models were used to predict what it was from the earlier analysis.
The better of the two programmes reproduced a synthesised sound realistic enough for the scientists to guess the original word. There is evidence that the brain breaks sound down to its component acoustic frequencies, with speech spanning the range from about 1 Hertz (cycles per second) to 8,000 Hertz.
British expert Professor Jan Schnupp, from Oxford University, said of the findings, which are reported in the online journal Public Library of Science Biology: "This study by Pasley and others is really quite remarkable."