In recent months and years different research teams have been developing prosthetics that tap into the nerve system of the user, meaning movements can be controlled by the mind in a similar way biological limbs function. However, despite significant progress having been made, mind-controlled prosthetics produced to date have been limited in their dexterity.

That looks set to change following the recent publication of details around a prosthetics research project of a team of scientists from the University of Michigan Medical School, led by Paul Cederna. The new control system they have developed, details of which can be found in the most recent edition of the Science Translational Medicine journal, is so dexterous it can undo shirt buttons.

Like other prosthetics that are thought controlled, the new technique works by the technology interpreting the nerve signals that would have controlled the movements of the lost limb. These signals are then sent to the robotic hand, which moves the fingers and thumb in the intended way.

However, where previous attempts at similar technology have been limited is by very low voltage nerve signals that are difficult to distinguish. Professor Cederna’s team found a solution. They discovered that these signals could be amplified by the placement of small pieces of muscle on each nerve.

“Nerve signals come down, enter the muscle, the muscle contracts and we record huge signals.”

These stronger signals mean the tech could accurately interpret exactly which nerve in a bundle of fibres was firing. The scientists are hopeful that the vastly improved levels of dexterity that result could change the way amputees relate to their prosthetics.

“The patients use possessive terms to describe it. They say: ‘My hand, my finger.’ It is almost like the prosthesis is being embodied. It is part of them — as opposed to a tool strapped to their body.”

A positive side-effect of how patients who have been trialling the new technology in the lab accepted the prosthetic as a genuinely functioning part of their body is that they also experienced a reduction in ‘phantom pain’. Amputees often experience a sense of discomfort or pain emanating from where their lost limb would have been, despite the fact that it is not physically there and could not, therefore, be a source of genuine pain.

The signals the new system is able to interpret are so accurate they represent a leap forward on even the best prosthetics developed until now. That opens up a whole new range of possibilities around how prosthetics can be used. Until now, the functionalities the ‘hardware’ has been capable of have been ahead of what the ‘software’ of signals could take advantage of. The University of Michigan Medical School team now have the inverse problem.

“The engineers have made hands that are exquisite. But there has never been a good way to control all their functionality. We had a beautiful piece of machinery that we couldn’t use. Now we can harvest so many signals, we find the prosthetics actually need more functions.”

Source: The Times

The new control system can so far only be used in a laboratory environment but the team hopes that the technology will be ready for patients that are part of trials to take home with them within 2 years.

Karen Sussex, a 54-year-old who lost her right hand after a 2016 illness is one such patient, whose involvement in the trials will mean she qualifies to be among the first to get to keep one of the new prosthetics. And she’s clearly looking forward to it:

“It feels like I have my hand back. All I have to do is think that I’m moving one of my fingers and then that finger moves.”