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Paralyzed Patient Moves Prosthetic Arm With Her Mind
It sounds like science fiction, but researchers are gaining ground in developing mind-controlled robotic arms that could give people with paralysis or amputated limbs more independence.
The technology, known as brain-computer (or brain-machine) interface, is in its infancy as far as human use — though scientists have been studying the concept for years. But experts say that people with paralysis or amputations could be using the technology at home within the next decade.
It basically boils down to people using their thoughts to control a robot arm that then performs a desired task, like grasping and moving a cup. That’s done via tiny electrode “grids” implanted in the brain that read the movement signals firing from individual nerve cells, then translate them to the robot arm.
“We have the ability to capture information from the brain and use it to control the robotic arm,” said Dr. Elizabeth Tyler-Kabara, who presented her team’s latest findings on the technology Tuesday, at the annual meeting of the American Association of Neurological Surgeons, in New Orleans.
However, she stressed, “we still have a ton to learn.”
Right now, the robot arm is confined to the lab. After getting their electrodes implanted, study patients come to the lab to work with the robotic limb under the researchers’ supervision. So far, Tyler-Kabara and her colleagues at the University of Pittsburgh School of Medicine have tested the approach in one patient. Researchers at Brown University in Providence, R.I., have done it in a handful of others.
One of the big questions, Tyler-Kabara said, is “how much control is enough?” That is, how well does the mind-controlled arm need to work to bring real everyday benefits to people?
At the meeting on Tuesday, Tyler-Kabara presented an update on how her team’s patient is faring. The 53-year-old woman had long-standing quadriplegia due to a disease called spinocerebellar degeneration — where, for unknown reasons, the connections between the brain and muscles slowly deteriorate.
Tyler-Kabara performed the surgery, where two tiny electrode grids were placed in the area of the brain that would normally control the movement of the right hand and arm. The electrode points penetrate the brain’s surface by about one-sixteenth of an inch.
“The idea is pretty scary,” Tyler-Kabara acknowledged. But her team’s patient had no complications from the surgery and left the hospital the next day. There’ve been no longer-term problems either, she said — though, in theory, there would be concerns about infection or bleeding over the long haul.
The surgery left the patient with two terminals that protrude through her skull. The researchers used those to connect the implanted electrodes to a computer, where they could see brain cells firing when the patient thought about moving her hand.
She was quickly able to master simple movements with the robotic arm, like high-fiving the researchers. And after six months, she was performing “10-degrees-of-freedom” movements, Tyler-Kabara reported at the meeting.
That includes not only moving the arm, but also flexing and rotating the wrist, grasping objects and affecting several different hand “postures.” She has accomplished feats like feeding herself chocolate.
The researchers initially used a computer in training sessions with the patient, but after that the robot arm is directly linked to the electrodes — so there is no need for “computer assistance,” according to Tyler-Kabara.
Still, before the technology can ultimately be used at home, she said, researchers have to devise a “fully implanted” wireless system for controlling the robot arm.
Another expert talked about the new technology.
“This is one more encouraging step toward developing something practical that people can use in their daily lives,” said Dr. Robert Grossman, a neurosurgeon at Methodist Neurological Institute in Houston, who was not involved in the research.
It’s hard to put a time line on it all, Grossman said, since technological advances could changes things. He also noted that several research groups are looking at different approaches to brain-computer interfaces.
One, Grossman said, is to do it noninvasively, through electrodes placed on the scalp.
Study author Tyler-Kabara said that noninvasive approach has met with success in helping people perform simple tasks, like moving a cursor on a computer screen. “But I don’t think it will ever be good enough for performing complicated tasks,” she said, noting that it can’t work as precisely as the implanted electrodes.
A next step, Tyler-Kabara said, is to develop a “two-way” electrode system that stimulates the brain to generate sensation — with the aim of helping people adjust the robot’s grip strength.
She said there is also much to learn about which people will ultimately be good candidates for the technology. There may, for example, be some brain injuries that prevent people from benefiting.
Because this study was presented at a medical meeting, the data and conclusions should be viewed as preliminary until published in a peer-reviewed journal.
Sense of Touch Reproduced Through Prosthetic Hand
In a study recently published in IEEE Transactions on Neural Systems and Rehabilitation Engineering, neurobiologists at the University of Chicago show how an organism can sense a tactile stimulus, in real time, through an artificial sensor in a prosthetic hand.
Scientists have made tremendous advances toward building lifelike prosthetic limbs that move and function like the real thing. These are amazing accomplishments, but an important element to creating a realistic replacement for a hand is the sense of touch. Without somatosensory feedback from the fingertips about how hard you’re squeezing something or where it’s positioned relative to the hand, grasping an object is about as accurate as using one of those skill cranes to grab a stuffed animal at an arcade. Sure, you can do it, but you have to concentrate intently while watching every movement. You’re relying on your sense of vision to compensate for the lack of touch.
Sliman Bensmaia, assistant professor of organismal biology and anatomy at the University of Chicago, studies the neural basis of the sense of touch. Now, he and his colleagues are working with a robotic hand equipped with sensors that send electrical signals to electrodes implanted in the brain to recreate the same response to touch as a real hand.
Bensmaia spoke about how important the sense of touch is to creating a lifelike experience with a prosthetic limb.
“If you lose your somatosensory system it almost looks like your motor system is impaired,” he said. “If you really want to create an arm that can actually be used dexterously without the enormous amount of concentration it takes without sensory feedback, you need to restore the somatosensory feedback.”
The researchers performed a series of experiments with rhesus macaques that were trained to respond to stimulation of the hand. In one setting, they were gently poked on the hand with a physical probe at varying levels of pressure. In a second setting, some of the animals had electrodes implanted into the area of the brain that responds to touch. These animals were given electrical pulses to simulate the sensation of touch, and their hands were hidden so they wouldn’t see that they weren’t actually being touched.
Using data from the animals’ responses to each type of stimulus, the researchers were able to create a function, or equation, that described the requisite electrical pulse to go with each physical poke of the hand. Then, they repeated the experiments with a prosthetic hand that was wired to the brain implants. They touched the prosthetic hand with the physical probe, which in turn sent electrical signals to the brain.
Bensmaia said that the animals performed identically whether poked on their own hand or on the prosthetic one.
“This is the first time as far as I know where an animal or organism actually perceives a tactile stimulus through an artificial transducer,” Bensmaia said. “It’s an engineering milestone. But from a neuroengineering standpoint, this validates this function. You can use this function to have an animal perform this very precise task, precisely identically.”
The FDA is in the process of approving similar devices for human trials, and Bensmaia said he hopes such a system is implemented within the next year. Producing a lifelike sense of touch would go a long way toward improving the dexterity and performance of prosthetic hands, but he said it would also help bridge a mental divide for amputees or people who have lost the use of a limb. Until now, prosthetics and robotic arms feel more like tools than real replacements because they don’t produce the expected sensations.
“If every time you see your robotic arm touching something, you get a sensation that is projected to it, I think it’s very possible that in fact, you will consider this new thing as being part of your body,” he said.