• New technology in prosthetics is allowing for controlling appendage mechanisms with brain activity.
  • While not an equivalent replacement of a lost limb, further development of the technology will bring us closer to tapping into the full potential of advanced prosthesis.
  • Scientists are working on new electronics that permit two-way communication between different parts of the nervous system and prostheses.
  • This could allow us to send brain signals to disconnected nerves in damaged limbs or to robotic prostheses in order to move them by thought.

TALKING BACK

While advances in medical technology already allow people with damaged limbs or robotic prostheses to communicate with those limbs, they haven’t yet gotten the limbs to properly talk back. That may change, thanks to the work of a team of engineers, researchers, and scientists from the University of Washington’s (UW) GRIDLab and the National Science Foundation Center for Sensorimotor Neural Engineering (CSNE).

The team is creating electronics that permit two-way communication between different parts of the nervous system. This would allow a user to control their limbs using thought and also receive information from the limb, such as whether it is in the correct position or grasping an object tightly enough.

To develop this system, the researchers implanted a set of ElectroCorticoGraphic (ECoG) electrodes directly onto the surfaces of volunteer patients’ brains. They then fitted the patients with gloves equipped with sensors capable of tracking their hand positions. Patients were asked to move their hands into certain positions and would receive sensory feedback on the positioning in the form of electrical currents delivered directly to the brain through the ECoG electrodes. An open hand resulted in no stimulation, but as the hand closed, the stimulation would increase in intensity.

Credit: University of Washington/Mark Stone
Credit: University of Washington/Mark Stone

Researchers claim this is the first time a conscious patient has successfully used a system like theirs, and while their system’s stimulation doesn’t mimic natural “feel,” it’s a start. “Right now we’re using very primitive kinds of codes where we’re changing only frequency or intensity of the stimulation, but eventually it might be more like a symphony,” Rajesh Rao, CSNE director, told News Atlas.

A HELPING HAND

“The idea is that we’re able to translate thoughts into motion,” says Mike McLaughlin of the Johns Hopkins Applied Physics Laboratory, the creators of the Modular Prosthetic Limb. Hopkins is one of the engineering initiatives that have recently brought advancements in prosthetics and bionic limbs, improving comfort and utility for upper-arm amputees.

Studies from biomedical engineers from Bloorview Research Institute have revealed the inefficiency of market-available prosthetic arms, indicating that up to 75% of users reject and abandon their reconstructed limbs. Most arms available rely on controls developed in the 1950s; they had clunky cables, harnesses. The sensors used were just not intuitive enough for comfortable use.

In 2013, Coapt introduced a prosthetic arm enhanced with an new control system that can recognize subtle nerve signals. Coapt uses pattern recognition to decode electric signals from the remaining arm muscles, with an algorithm focused on intuitive learning to produce graceful, natural movement. DEKA Research and Development Corp. from Manchester uses the Coapt technology in their bionic arm LUKE, intelligently named after Luke Skywalker’s prosthesis in Star Wars.

Photo: Megan Scudellari
Photo: Megan Scudellari

LIMITS TO OVERCOME

Still, none of these prosthesis systems work like a real hand. Pre-programmed controls are what makes the robotic extensions work. Coapt lets the user pre-program about six to eight movements for everyday use: pointing, pinching, and making a fist, to name a few.

What limits the technology is the sheer complexity of our body. “If you move your arm, there are probably 500 million neurons involved. Right now, the best we can do is see a few hundred of those neurons,” says McLaughlin.

Scientists hope that future prosthesis can let amputees regain control by tapping into the brain’s symphony directly, by implanting electrodes under the skin or even directly into the brain. It’s easy to take for granted our automatic, well-organized machine of a body—a simple wave hello or a handshake greeting is nearly thoughtless action. Someday soon, technology may let us overcome these physical limitations.

THE FUTURE OF FEELING

Technology like this could make a huge difference in the lives of people with lost limbs or spinal cord injuries, as even the seemingly simplest tasks can be impossible without proper sensory feedback.

Thankfully, teams all across the globe are working on ways to improve haptic feedback, from socks that grant sensation to prosthetic feet to bionic hands fitted with force sensors. As this technology advances, the line between the body you’re born with and the one built for you could eventually blur to the point of seamlessness.

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