(CNN)A brain implant has helped restore a type of speech to a man more than 15 years after a stroke robbed him of the ability to speak, researchers reported Wednesday.
They're calling it a neuroprosthesis, and while it's only one patient for now, the team at the University of California, San Francisco (UCSF) hopes their device may help other paralyzed people communicate.
"To our knowledge, this is the first successful demonstration of direct decoding of full words from the brain activity of someone who is paralyzed and cannot speak," said Dr. Edward Chang, a neurosurgeon at UCSF who led the research team.
"It shows strong promise to restore communication by tapping into the brain's natural speech machinery," Chang said in a statement.
The team implanted an array of electrodes over the area of the brain that controls speech in a man who suffered a stroke that left him paralyzed and unable to speak at age 20.
"Since his injury, he has had extremely limited head, neck, and limb movements, and communicates by using a pointer attached to a baseball cap to poke letters on a screen," UCSF said in a statement.
"His cognitive function was intact," the team wrote in their report, published in the New England Journal of Medicine.
The man, now in his late 30s, was prompted to use a limited vocabulary while the device was tuned using computer algorithms to translate electrical activity from his brain. These words were then projected onto a computer screen.
UCSF has a video of the man using the device. "Good morning," he is prompted via a computer screen. "Hello," comes the answer, a few seconds later, also typed as text across the screen.
Asked, "How are you today?" the patient answers, haltingly, "I am very good."
"We decoded sentences from the participant's cortical activity in real time at a median rate of 15.2 words per minute, with a median word error rate of 25.6%," the team wrote.
"We detected 98% of the attempts by the participant to produce individual words, and we classified words with 47.1% accuracy using cortical signals that were stable throughout the 81-week study period," researchers said.