ETH Zurich

Neurofeedback and the prosthetic limb: A way to make users ‘feel’

Artificial limbs have been lacking a sense of touch since their creation in 1846, but thanks to a group of researchers that has all changed.

Quick Notes:

  • Neurofeedback has been used to connect residual nerves to the artificial leg for more personalized control

  • These new pathways from limb to brain gave users improved ‘sense’ of the limb

  • Phantom limb pain was significantly reduced for both participants

Artificial legs have long been used to help amputees walk again, but without the ability to connect to the user’s brain pathways, learning how to use one in everyday life was a long process, and walking function would never be as smooth or seamless as it would have been prior to having lost that leg.

But now, researchers out of ETH Zurich and The University of Belgrade have teamed up with companies SensArs and Össur to create a whole new type of prosthetic process, giving the user a sense of touch where it was thought to be lost forever.

Amputees cannot feel their leg prosthesis. This means that the terrain they’re walking on, where their leg is, and how it is moving is unknown to them unless they are fully focused on it. But with this new process of neurofeedback, participants were able to “feel” all the things a person with intact legs could feel, giving them a better sense of control and confidence while walking. The bionic prosthesis allowed the volunteers to “feel” their legs in real-time.

The team used an interface to link nerves in the leg to the prosthetic.

While an individual who hasn’t undergone amputation will feel where their legs are while walking and have their nervous system send them signals, an amputee will not, making it impossible to control leg movements without actively doing so—until now.

They have found the ability to attach nerves in the upper thigh to both the prosthetic limb and a neurofeedback mechanism. They then used sensors on the bottom of the feet and around the knee joint to get closer access to how the leg would naturally move. To put it all together, electrodes and a neurostimulator were implanted into the volunteers, and then the area around it was left to heal.

ETH Zurich

This was then used to send signals from the brain directly to the limb in question. This allowed the participants of the proof-of-concept study to gain more control over their limb, restoring otherwise lost sensory feedback. The two volunteers who participated in the study showed vast improvements in not only their natural ability to walk on the limb, but also in the energy they expelled while walking, such as oxygen use and mental fatigue.

The improvements also saw a decrease in phantom limb pain.

In addition to the prosthesis fitting and sensor implantation, the participants went through a series of intraneural stimulation sessions, which led to the suppression of phantom limb pain. One of the participants in the small study had a significant reduction in their pain and the other reported it was gone altogether.

With up to 80 percent of amputees reporting chronic phantom limb pain, the promise of technology in that area could mean a severe reduction in those numbers and a new treatment for the symptoms that amputees face following the loss of their leg.

This process of being able to send signals in real-time from the brain to the artificial leg will make walking after amputation less demanding than it has ever been. The participants had gone through walking tests considerably faster, and even improved confidence in their artificial limb when driving.

A deeper dive — Related reading from the 101: