Scientists have reconstructed the words people hear by using a computer algorithm to decode electrical signals in the brain.
Eggheads at the University of California in Berkeley fastened electrodes onto the bare brains of patients undergoing neurosurgery. The scientists were studying the superior temporal gyrus (ridge on the cerebral cortex), the area thought to play a crucial role in comprehending the sounds we hear.
During surgery, patients were played recordings of people speaking. As the patients' brains processed the auditory information, the electrodes attached to their brains transmitted electrical signals into a computer. Software then calculated how the subjects' brains responded according to the speech frequencies they heard. It could therefore reproduce a sound close enough to the original word for the researchers to guess the word better than chance.
The study shows that one day people like Stephen Hawking may be able to upgrade the speech software they use to technology that can process their very thoughts.
“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 Robert Knight, professor of psychology and neuroscience, and lead author of the study, published in PLoS Biology. "If you could eventually reconstruct imagined conversations from brain activity, thousands of people could benefit."
The research is based on a study of only 15 people and the technique cannot yet read imagined speech. Understanding that is the next step, says Brian Pasley, a post-doctoral researcher who worked on the project.
"This research is based on sounds a person actually hears, but to use this for a prosthetic device, these principles would have to apply to someone who is imagining speech," Pasley said in a statement.
"There is some evidence that perception and imagery may be pretty similar in the brain. If you can understand the relationship well enough between the brain recordings and sound, you could either synthesise the actual sound a person is thinking, or just write out the words with a type of interface device."
The team behind the research is fighting the suggestion that subsequent technology based on this procedure could be used with malign intent. For the moment, the technique works only on patients who are undergoing neurosurgery and willing to have 256 electrodes attached to their exposed brains.
“How Dr Strangelove might use this in the future is slightly above my pay grade,” Knight said. ®