A chip engineered to amplifiy neural signals acts as
intermediary between brain and computer.
Courtesy Nicolelis Lab
What that means, Hochberg says, is that the brain signals that once controlled the subject’s paralyzed hand and arm were still there and functioning—they just could not pass through the damaged spinal cord to allow the arm and hand to move. He hopes devices like BrainGate will circumvent such damage and allow the brain to communicate with a prosthetic limb or even the actual one, in the manner of Miller’s research. “If we can take those natural signals and send them to a functional electrical stimulation system placed in and around the muscles and nerves of an arm or a leg,” Hochberg says, “someone might be able to control their own limb again using neural technology rather than injured biology.”
Another planned clinical trial involves a miniaturized neural electrode the size of a couple of kernels of corn, pioneered by neuroscientist Richard Andersen at Caltech. Hoping to accomplish what some have compared to mind reading, Andersen wants to implant his device in the brain’s higher-level sensory-motor areas, including the parietal lobe and premotor cortex, the seats of personal preference and intent. From a practical perspective, the implant could empower patients to use their abstract thoughts and feelings to control a medical device—a nuanced form of biofeedback. On another level, it could help physicians interpret thoughts that would normally control the patient’s body. “The first thing a doctor often asks is ‘How are you feeling?’?” Andersen says. “By looking at the decoded neural signals, the doctor could know.”
Speaking His Mind
Even better, says Philip Kennedy, would be giving the locked-in the gift of actual voice—and he’s getting close.
Erik Ramsey became the first subject for this research after he suffered a horrible car accident. Surgery repaired a host of broken bones and torn muscles, but Ramsey didn’t seem to wake up. At first his doctors thought that the anesthesia was taking an unusually long time to wear off. But eventually Ramsey’s father, Eddie, realized something was terribly wrong. Ramsey had suffered a catastrophic brain stem stroke, appearing to doom him to a locked-in life at the age of 16.
It might be odd to describe Ramsey as lucky, but in a way he is, because his condition was correctly diagnosed. No one knows how many others in the same state are incorrectly labeled as vegetative or semicomatose and warehoused, doomed to a nightmare world where they exist in a body that feels but cannot move, with a brain that is intact, hearing and seeing but unable to communicate a presence to others. In one 1996 study published in the British Medical Journal, 17 of 40 patients originally diagnosed as vegetative turned out to be locked-in instead. Ramsey found someone who could unlock him.
Ramsey, now 25, has dark, almond-shaped eyes that hint of his mom’s Filipino heritage. He is big and broad-shouldered. If he could get up out of his wheelchair, he’d be well over 6 feet tall. If he were mobile, he’d have the physique of a football player.
His mind is fine but he cannot move, except for tiny eye gestures (up for yes, down for no) and occasional muscle spasms. I ask him if coming to the lab is fun. He looks down. Is it more like work? He looks up. He is an inner-space pioneer whose work holds the promise of freeing himself and others who are locked-in, at least to a degree, by eventually allowing them to have real-time conversations.
“Developing a neural prosthesis for speech is extremely important to me,” says Kennedy, who, as a neurologist, regularly sees patients with ALS and stroke. There are some 30,000 ALS patients in the United States alone. All will become locked-in eventually, and 5,000 to 6,000 each year are at the point where they must decide whether to spend the rest of their lives on a ventilator, unable to speak, or to refuse it and let themselves die. If they knew they could continue to communicate as their disease progressed, they would undoubtedly more often choose to live, and they could even be productive. “People call my office all the time about a loved one who has had a brain stem stroke, lying in bed, unable to speak,” Kennedy says. “I expect to be able to help these people with this research.”
In the effort to unlock the door, Ramsey is treading where no one has gone before. The brain’s precise speech center varies from person to person, so to find Ramsey’s target area—the place where an implant could discern the appropriate speech signals—Kennedy used a functional magnetic resonance imaging (fMRI) scan. Showing Ramsey pictures, he told the young man to say to himself phrases like “This is an elephant” and “This is a dog.”
As Ramsey “spoke” internally, the MRI pinpointed neurons associated with speech, but the results were surprising. The neural signals were not sparked by words or their meanings, per se, but instead by how the muscles of the lips, tongue, jaw, and larynx would move to produce the sounds—movements that Ramsey could only imagine.
In 2004 a neurosurgeon on Kennedy’s team inserted an electrode in the part of Ramsey’s cortex where the signals were most dense. Then an amplifier and transmitter were screwed onto the top of Ramsey’s skull. Ever since then, he has arrived at Kennedy’s lab every Monday, Wednesday, and Friday afternoon. Kennedy’s team affixes an amplifier atop Ramsey’s head to record speech signals from his motor cortex as he imagines physically moving his mouth, tongue, and jaw to make speech sounds, called phonemes.
Over the course of three years, Kennedy’s group has recorded 41 distinct patterns from 56 neurons in Ramsey’s brain. Decoding the signals has been tricky and slow going. But Kennedy collaborator Frank Guenther, associate professor of cognitive and neural systems at Boston University, and his colleague Jonathan Brumberg recently worked out a system that translates neural signals from Ramsey’s implant into vocal form via a synthesiser that produces the corresponding sound.
In February, for the first time, Ramsey heard the synthesized vowels he was “saying” in his head (consonants are harder and will come later) played back in real time, as he was thinking them. He heard the phonemes blare from computer speakers and, at the same time, could see his neural signals directing a cursor to the symbol for the sound (like “ooh” or ?“aah”) on the screen.
Guenther and Brumberg flew in from Boston for this groundbreaking experiment. When the computer “spoke” for Ramsey for the first time, whoops of delight could be heard in Kennedy’s lab. “It was incredibly exciting,” Guenther says. “We finally all knew this was going to work.” Ramsey’s brain is already changing as his neurons learn to fire in specific ways that better control the synthesizer. “We are now convinced we’ll be able to give him rudimentary speech within not too many years,” Guenther says.
