A man unable to speak after a stroke has produced sentences through a system that reads electrical signals from speech production areas of his brain, researchers reported in July 2021…The participant had a stroke more than a decade ago that left him with anarthria—an inability to control the muscles involved in speech. Because his limbs are also paralyzed, he communicates by selecting letters on a screen using small movements of his head, producing roughly five words per minute.
To enable faster, more natural communication, neurosurgeon Edward Chang of the University of California, San Francisco, tested an approach that uses a computational model known as a deep-learning algorithm to interpret patterns of brain activity in the sensorimotor cortex, a brain region involved in producing speech . The approach has so far been tested in volunteers who have electrodes surgically implanted for non-research reasons such as to monitor epileptic seizures.
In the new study, Chang’s team temporarily removed a portion of the participant’s skull and laid a thin sheet of electrodes smaller than a credit card directly over his sensorimotor cortex. To “train” a computer algorithm to associate brain activity patterns with the onset of speech and with particular words, the team needed reliable information about what the man intended to say and when….So the researchers repeatedly presented one of 50 words on a screen and asked the man to attempt to say it on cue. Once the algorithm was trained with data from the individual word task, the man tried to read sentences built from the same set of 50 words, such as “Bring my glasses, please.”
With the new approach, the man could produce sentences at a rate of up to 18 words per minute, Chang says…The system isn’t ready for use in everyday life, Chang notes. Future improvements will include expanding its repertoire of words and making it wireless, so the user isn’t tethered to a computer roughly the size of a minifridge.
Excerpts from Kelly Servick, Brain signals ‘speak’ for person with paralysis, Science, July 16, 2021