A breakthrough by researchers at Northwestern University is giving hope to millions of amputees that they might eventually regain some of the ability they lost. While most prosthetic limbs utilize a motor in order to achieve motion, the Northwestern prosthesis can be controlled by the wearer’s own mind.
Jesse Sullivan was an electrical lineman until 2001 when he was electrocuted so severely that both of arms needed to be amputated. But Jesse wasn’t ready to give up. Eight years ago, he underwent surgery and was fitted with experimental prosthetic limbs, developed by a team of biomechanical engineers at the Rehabilitation Institute of Chicago (RIC) through the Northwestern University. The prostheses utilized a system that interprets brain signals. By connecting the arms to nerves in Jesse’s stump and connecting those nerves to nerves in his chest, the system is able to “amplify” his brain signals, giving Jesse him more control than any previous generation of prosthetic limbs.
Amazingly, the studies in the years after Jesse’s surgery have shown that the nerves in his stumps have become stronger over time. This has astounded doctors since the nerves of amputated limbs usually become weaker over time as they are not used. Nate Bunderson, a researcher on the project who is now at the Georgia Institute of Technology, said in a presentation at the Society of Neuroscience conference in San Diego last November that he believes this may be due to Jesse’s brain becoming accustomed to the new path. “If you transfer the nerves [from the stump] to healthy muscles, then you can amplify the brain signals used to control the arm,” said Bunderson.
Todd Kuiken, MD, PhD, the man who created Jesse’s prosthetic arms and the RIC’s Director of Amputee Programs, said that their next step is to continuing exploring how patterns of brain activity may be used to control prosthetic limbs and to make the technology available for more patients — including those whose prosthetic limbs are older and less sophisticated.
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