A brain-computer interface that's fast and accurate
One rainy day in October 2007, Dennis Degray was taking out the trash when he slipped, fell and landed on his chin. He severely injured his spinal cord, becoming paralyzed from the neck down. “I’ve got nothing going on below the collarbones,” he says.
But above the collarbones, in the motor cortex of his brain, he now has two implanted electrode arrays, each the size of a baby aspirin. In a recent study, he and two other participants, who have severe limb weakness from amyotrophic lateral sclerosis, demonstrated the fastest, most accurate typing to date using only their brains to control an on-screen cursor.
“This study reports the highest speed and accuracy, by a factor of three, over what’s been shown before,” says Stanford professor of electrical engineering Krishna Shenoy, PhD, a senior author of the paper, which was published online in February in eLife. “We’re approaching the speed at which you can type text on your cellphone.”
The study is part of the BrainGate collaboration among Stanford, Brown University, Massachusetts General Hospital, Case Western Reserve University and the Providence VA Medical Center, which aims to provide brain-computer interfaces that help people communicate and move despite neurological disease, neurological injury or limb loss.
Shenoy’s lab pioneered the algorithm for the interface, which transmits signals from the brain to a computer via a cable, then translates them into point-and-click commands for an on-screen keyboard. With minimal training, the participants were able to visualize the arm, hand and finger movements necessary to type a letter and then watch as the cursor selected it on the screen.
Degray was able to copy sentences and phrases — think “The quick brown fox jumped over the lazy dog” — at a rate of 7.8 words per minute. The other two participants’ average rates were 6.3 and 2.7 words per minute. They did not use automatic word-completion software, which likely would have made their typing faster.
“Our study’s success marks a major milestone on the road to improving quality of life for people with paralysis,” says professor of neurosurgery Jaimie Henderson, MD, a co-senior author of the study who implanted the devices in two of the three patients. The tiny silicon chips are just over one-sixth of an inch square, with 100 electrodes that penetrate the brain to about the thickness of a quarter and tap into the electrical activity of individual nerve cells in the brain region controlling movement, the motor cortex.
Shenoy says the day is coming, perhaps five years from now, when a wireless brain-computer interface can be fully implanted without cosmetic impact and used around the clock without caregiver assistance. “I don’t see any insurmountable challenges,” he says. “We know the steps we have to take to get there.”
Meanwhile, those who have tested the latest typing interface are enthusiastic. “This is like one of the coolest video games I’ve ever gotten to play with,” says Degray. “And I don’t even have to put a quarter in it.”