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DARPA uses nerve/muscle interfaces to give amputees feedback and improve control

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June 2, 2013

Artist’s concept of a flat interface nerve electrode (FINE)

Artist’s concept of a flat interface nerve electrode (FINE)

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Artificial limbs have come a long way in recent years with the development of prostheses that can be controlled directly by the patient’s nerves. The problem is, links between living nerves and the prostheses break down over time, which makes permanent attachment and practical control difficult. To understand why this happens and to help give patients more control over their prostheses, DARPA has instituted a number of programs aimed at improving neural interfaces and allowing amputees to have better control of advanced prostheses in the near term.

According to the US Defense Department, over 2,000 US military personnel have suffered major amputations since the year 2000. With the US government committed to providing these amputees with advanced prosthetic technology, DARPA’s Reliable Neural-Interface Technology (RE-NET) program studies why neural interfaces stop working properly and why a prosthetic limb can’t understand nerve signals well enough to move with high speed and resolution.

RE-NET is divided into a number of teams focusing on a number of different approaches. One is the Histology for Interface Stability over Time team that studies interactions between biotic (living) and abiotic (artificial) systems and why they fail, as well as other factors involved.

The others are the Reliable Peripheral Interfaces and the Reliable Central-Nervous-System Interfaces teams. They are working to build systems to study how interfaces connected directly to the brain and spinal cord can be used to control prostheses with high reliability and performance.

An example of this was demonstrated at the Rehabilitation Institute of Chicago where Former Army Staff Sgt. Glen Lehman, injured in Iraq, used neural interfaces and existing muscles to demonstrate simultaneous joint control of a prosthetic arm. Lehman's arm relied on Targeted Muscle Re-innervation, which involves transferring multiple nerves to regions of a targeted muscle and then using independent signals from the nerves to control the prosthesis.

Artist's concept of Leaded Implantable Myoelectric Sensors, which are a part of Targeted M...

“Although the current generation of brain, or cortical, interfaces have been used to control many degrees of freedom in an advanced prosthesis, researchers are still working on improving their long-term viability and performance,” said Jack Judy, DARPA program manager. “The novel peripheral interfaces developed under RE-NET are approaching the level of control demonstrated by cortical interfaces and have better biotic and abiotic performance and reliability. Because implanting them is a lower risk and less invasive procedure, peripheral interfaces offer greater potential than penetrating cortical electrodes for near-term treatment of amputees. RE-NET program advances are already being made available to injured warfighters in clinical settings.”

One factor in controlling advanced prosthetic limbs is sensory feedback, Without it, an artificial arm is just a dead rod of metal and plastic that needs to be controlled by sight. Researchers at Case Western Reserve University used a Flat Interface Nerve Electrode (FINE) to demonstrate direct sensory feedback. Instead of using the patient’s residual nerves to just control the prosthesis, the researchers used the link to provide a rudimentary sense of touch. This way, the patient had some awareness of the limb and what it was doing, so it could be used to rummage in a bag or pick up objects hidden behind a curtain.

DARPA said that the RE-NET program will continue until 2016.

The video below shows an advanced prosthesis with simultaneous joint control.

Source: DARPA

About the Author
David Szondy David Szondy is a freelance writer based in Monroe, Washington. An award-winning playwright, he has contributed to Charged and iQ magazine and is the author of the website Tales of Future Past.   All articles by David Szondy
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3 Comments

Amputees like me, who are missing lower limbs, need this technology to allow us to have a prosthesis that can actually move and be controlled by our residual limb in the same manner as a natural leg would. They have had arms with increasing realness but weight bearing lower limbs have not advanced as much. I know how to marry these technologies if any biomechanical engineers are interested.

Roger Chan
3rd June, 2013 @ 09:24 am PDT

Alternatively, re-innervation of transplanted natural limbs should be attempted first. The reason that the severed CNS does not reconnect, except in fetuses and the very, very young (mice) is because of a lack of fetal blood circulation. The fetal blood differs from "normal" blood in that it allows innervation everywhere. Once the baby is born, the blood changes in order to accept CNS inputs only from the strongest senders, so feedback chemosensory proteins in the blood "report" to start a regression process. In an amputee, the regression process in the blood born pheromone receptor proteins is underway, so the neural regeneration that takes place in a fetus isn't possible. With age, babies flail around a lot less because the brain is able to take control of the smaller Central Nervous System that the reabsorption of weak growing neurons allows. Certainly this would be easier, less painful, and more beneficial than trying to interface neurons to prostheses from scratch.

TogetherinParis
5th June, 2013 @ 10:06 am PDT

re; TogetherinParis

Unless you happen to have a genetically identical donor transplants require suppressing the immune system. I would rather have the prosthetic.

Slowburn
2nd July, 2013 @ 04:02 pm PDT
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