Scientists revive paralyzed limbs by rewiring brain signals

Researchers at the University of Washington are working to reroute brain signals in an effort to give paralyzed people the ability to move their limbs again.

By creating an artificial connection between nerve cells in the brain and muscles, scientists say they are restoring voluntary movement to the once-paralyzed limbs, according to a report from the University of Washington in Seattle.

The rerouting effectively bypasses damaged nerves in subjects with spinal cord injuries, which generally damage nerves but leave muscles and brain tissue unharmed.

Research that involves making new connections in living brains and even connecting robots to living brains has been gaining a lot of attention in the past year.

Less than a year ago, a scientist at the University of Arizona announced that he had successfully connected a moth’s brain to a robot.

Charles Higgins, an associate professor at the university stated last year that the research will lead to hybrid computers running both technology and living organic tissue. He also said that the hybrid systems could be used to make people with spinal cord injuries mobile again.

Moth-brained robot

Last year Higgins built a robot guided by the brain and eyes of a moth.

He basically strapped a hawk moth to the robot and then put electrodes in neurons that deal with sight in the moth’s brain. Then the robot responded to what the moth was seeing and when something approached the moth, the robot moved out of the way.

Higgins said he had been trying to build a computer chip that would do what brains do when processing visual images. He found that a chip that can function nearly like the human brain would cost about $60,000.

“At that price, I thought I was getting lower quality than if I was just accessing the brain of an insect which costs, well, considerably less,” he said. “If you have a living system, it has sensory systems that are far beyond what we can build. It’s doable, but we’re having to push the limits of current technology to do it.”

This organically guided, 12-in.-tall robot on wheels may be pushing the technology envelope right now, but it’s just the seed of what is coming in terms of combining living tissue with computer components, according to Higgins.

“In future decades, this will be not surprising,” he said. “Most computers will have some kind of living component to them. In time, our knowledge of biology will get to a point where if your heart is failing, we won’t wait for a donor. We’ll just grow you one. We’ll be able to do that with brains, too. If I could grow brains, I could really make computing efficient.”

While the moth is physically attached to the robot at this point, Higgins said he expects that one day only the brain itself will be needed.

“Can we grow a brain that does what we want it to do? Can I grow an eye with a brain connected to it and have it do what I need it to do? Can I engineer an organism and hook it into my artificial system?” he asked. “Yes, I really think this is coming. There are things biology can do so much better. Think of a computer that can be both living and nonliving. We’d be growing tissue that has no more intelligence than a liver or a heart. I don’t see ethical issues here.”

Awesome monkey business

In January, an international group of scientists successfully used a monkey’s brain activity to control a humanoid robot.

Miguel Nicolelis, a professor of neurobiology at Duke University and lead researcher on the project, said at the time the research may only be a few years away from helping paralyzed people walk again by enabling them to use their thoughts to control exoskeletons attached to their bodies.

In the most recent study out of the University of Washington, scientists conducted a proof of concept experiment by directly stimulating muscles using neuron activity in the motor cortex, which is the part of the brain that controls limb movement.

Eberhard Fetz, a UW professor and a researcher at the Washington National Primate Research Center, reported that by not having to decode complex neural signals to control a computer or robotic, direct muscle stimulation may give people more natural control of their movements.

In their experiments, monkeys were enabled to flex and extend their wrist to play a video game by artificially stimulating arbitrarily chosen motor cortex cells in their brains.

The monkeys’ wrist nerves were temporarily numbed with a local anesthetic, which paralyzed the muscles, according to the report. But despite the nerve block, the monkeys were still able to control the contraction strength of their wrist muscles.

University scientists noted that controlling the strength of the muscle contraction is what allows someone to gently pick up an egg or grab tightly to a handrail.

“Nearly every motor cortex neuron we tested in the brain could be used to control the stimulation of the wrist muscles,” said Chet Moritz, a UW senior fellow and lead author on the study. He added that even brain cells initially unrelated to movement could be controlled and used to stimulate muscles.

The university reported that about 10 more years of research will be needed before this research could be applied in human patients.

Computers with organic parts?

Higgins does see an ethical line, though. “Our goal is not to hook up primate brains to a robot,” said Higgins. “There’s the possibility, when you start to tap into brains, for all sorts of evil applications. There are certainly all these ethical issues when you start talking about human and primate brains.”

Higgins said he expects that these future hybrid systems will take the form of a visual sensor that sits on the front of an automobile and keeps the vehicle from rear-ending another car.

He also envisions them being embedded in military robots that can go into a hot zone, see the enemy and actually sniff out land mines. And hybrid systems could be used to make people with spinal cord injuries mobile again.

Will future desktops and laptops have organic parts?

Why not, said Higgins. “Computers now are good at chess and Word and Excel, but they’re not good at being flexible or interacting with other users,” he added. “There may be some way to use biological computing to actually make our computers seem more intelligent.”

Right now, Higgins has successfully attached electrodes into a single vision neuron in the moth’s brain. (Different neurons perform different functions like vision and the sense of smell. Humans have millions, if not trillions, of neurons. Insects have hundreds.)

Now, Higgins is experimenting with connecting four electrodes into neurons on both sides of the moth’s brain, expanding the visual image that the robot receives. “That should give me information about things moving on the left and right of the animal, at different speeds and moving up and down,” he explained.

Higgins is also experimenting with tapping into the moth’s muscles and olfactory senses. If he can work with the muscles, for instance, a strapped down moth trying to move in a certain direction would actually propel the robot.

“We’re developing a lot of technology that could be used for prosthetic applications,” said the researcher. “There are lots of people working on connecting functional brains to people who have nonworking limbs. You connect to the brain and send the information to a human limb or robotic limb. It’s an area that is closely related to what we’re doing.”

 

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