WASHINGTON • People robbed of the ability to talk due to a stroke or another medical condition may soon have real hope of regaining a voice, thanks to technology that harnesses brain activity to produce synthesised speech, researchers have said.
Scientists at the University of California, San Francisco (UCSF) implanted electrodes into the brains of volunteers and decoded signals in cerebral speech centres to guide a computer-simulated version of their vocal tract - lips, jaw, tongue and larynx - to generate speech through a synthesiser.
This speech was mostly intelligible, though somewhat slurred in parts, raising hope among the researchers that with some improvements, a clinically viable device could be developed in the coming years for patients with speech loss.
"We were shocked when we first heard the results - we couldn't believe our ears. It was incredibly exciting that a lot of the aspects of real speech were present in the output from the synthesiser," said study co-author and UCSF doctoral student Josh Chartier on Wednesday.
"Clearly, there is more work to get this to be more natural and intelligible, but we were very impressed by how much can be decoded from brain activity."
Stroke, ailments such as cerebral palsy, amyotrophic lateral sclerosis, Parkinson's disease and multiple sclerosis, brain injuries and cancer sometimes take away a person's ability to speak.
Some people use devices that track eye or residual facial muscle movements to laboriously spell out words letter by letter, but producing text or synthesised speech this way is slow, typically no more than 10 words per minute.
Natural speech is usually 100 to 150 words per minute.
The five volunteers, all capable of speaking, were given the opportunity to take part because they were epilepsy patients who already were going to have electrodes temporarily implanted in their brains to map the source of their seizures before neurosurgery. Future studies will test the technology on people who are unable to speak.