Public Release: 

Researchers uncover way to restore movement sensation in upper limb amputation patients

New findings published in journal Science Translational Medicine

Cleveland Clinic

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IMAGE: Illusory movement perception improves motor control for prosthetic hands. view more 

Credit: With permission, Cleveland Clinic Center for Medical Art & Photography © 2018. All Rights Reserved

Cleveland: A team of researchers led by Cleveland Clinic has published first-of-its-kind findings in Science Translational Medicine on a new method of restoring natural movement sensation in patients with prosthetic arms.

Led by Paul Marasco, Ph.D., the research team has successfully engineered a sense of complex hand movement in patients with upper limb amputations. This breakthrough may enhance the ability to control their prostheses, independently manage activities of daily living and improve quality of life.

"By restoring the intuitive feeling of limb movement - the sensation of opening and closing your hand - we are able to blur the lines between what the patients' brains perceived as 'self' versus 'machine'," said Marasco, head of the Laboratory for Bionic Integration in Cleveland Clinic's Lerner Research Institute. "These findings have important implications for improving human-machine interactions and bring us closer than ever before to providing people with amputation with complete restoration of natural arm function."

The team used small, but powerful, robots to vibrate specific muscles to "turn on" patients' sensation of movement, allowing them to feel that their fingers and hands were moving and that they were an integrated part of their own body. By feeling their missing hands while controlling their bionic prostheses, patients in the study could make complex grip patterns to perform specific tasks as well or better than able-bodied people.

To improve the relationship between the mind and the prosthesis, the researchers investigated whether they could use a movement illusion to help patients better control their bionic hands. They studied six patients who had previously undergone targeted nerve reinnervation, a procedure that establishes a neural-machine interface by redirecting amputated nerves to remaining muscles. When they vibrated the patients' reinnervated muscles to provide illusory movement, they not only felt their missing limbs move, but could use these sensations to intentionally manipulate their prostheses to accurately guide complex grips.

This is important because when an able-bodied person moves, the brain constantly receives feedback regarding the movement's progress. This unconscious sense prevents errors in movement, like overreaching, and allows the body to make necessary adjustments. People with amputation lose this essential feedback, however, and as a result, cannot control their prostheses without having to watch them carefully at all times.

The new study shows that the sense of missing limb movement, caused by the strategic muscle vibration, provided patients with better spatial awareness and improved fine motor control without having to visually monitor the prostheses. Additionally, the movement sensation made the bionic arms feel more like "self."

"When you make a movement and then you feel it occur, you intrinsically know that you are the author of that movement and that you have a sense of control or 'agency' over your actions," said Marasco. "People who have had an amputation lose that feeling of control, which leaves them feeling frustrated and disconnected from their prosthetic limbs. The illusions we generate restore the sensation of movement and reestablish their sense of agency over their prosthetics. This helps people with amputation to feel more in control."

Going forward, the research team is exploring ways to expand these techniques to patients who have lost a leg, as well as for those with conditions that inhibit movement sensation such as stroke. They are also working to package the system into a prosthesis for longer-term applications to enable patients to operate the system on a daily basis.

"The ultimate goal of our research is to use movement sensation to streamline the relationship between patients and their technology, to better integrate their prosthetics as a natural part of themselves," said Marasco.

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Marasco is a principal investigator in the Advanced Platform Technology Research Center, Louis Stokes Cleveland Department of Veterans Affairs Medical Center and an associate staff scientist in the Department of Biomedical Engineering in Cleveland Clinic's Lerner Research Institute. In 2016, he received a Presidential Early Career Award for Scientists and Engineers from former President Barack Obama.

Co-authors on the study included Jacqueline Hebert from the University of Alberta; Jon Sensinger from the University of New Brunswick; Ravi Nataraj from the Stevens Institute of Technology; and Brett Mensh from the Howard Hughes Medical Institute.

This study was funded through a National Institutes of Health, Office of the Director, Common Fund, Transformative R01 Research Award, # 1R01NS081710 - 01.

After the embargo lifts, the study can be accessed at: http://stm.sciencemag.org/lookup/doi/10.1126/scitranslmed.aao6990

About Cleveland Clinic

Cleveland Clinic is a nonprofit multispecialty academic medical center that integrates clinical and hospital care with research and education. Located in Cleveland, Ohio, it was founded in 1921 by four renowned physicians with a vision of providing outstanding patient care based upon the principles of cooperation, compassion and innovation. Cleveland Clinic has pioneered many medical breakthroughs, including coronary artery bypass surgery and the first face transplant in the United States. U.S. News & World Report consistently names Cleveland Clinic as one of the nation's best hospitals in its annual "America's Best Hospitals" survey. Among Cleveland Clinic's 52,000 employees are more than 3,600 full-time salaried physicians and researchers and 14,000 nurses, representing 140 medical specialties and subspecialties. Cleveland Clinic's health system includes a 165-acre main campus near downtown Cleveland, 10 regional hospitals, more than 150 northern Ohio outpatient locations - including 18 full-service family health centers and three health and wellness centers - and locations in Weston, Fla.; Las Vegas, Nev.; Toronto, Canada; Abu Dhabi, UAE; and London, England. In 2017, there were 7.6 million outpatient visits, 229,000 hospital admissions and 207,000 surgical cases throughout Cleveland Clinic's health system. Patients came for treatment from every state and 185 countries. Visit us at clevelandclinic.org. Follow us at twitter.com/ClevelandClinic. News and resources available at newsroom.clevelandclinic.org.

About Lerner Research Institute

The Lerner Research Institute is home to Cleveland Clinic's laboratory, translational and clinical research. Its mission is to promote human health by investigating in the laboratory and the clinic the causes of disease and discovering novel approaches to prevention and treatments; to train the next generation of biomedical researchers; and to foster productive collaborations with those providing clinical care. Lerner researchers publish more than 1,500 articles in peer-reviewed biomedical journals each year. Lerner's total annual research expenditure was $260 million in 2016 (with $140 million in competitive federal funding, placing Lerner in the top five research institutes in the nation in federal grant funding). Approximately 1,500 people (including approximately 200 principal investigators, 240 research fellows, and about 150 graduate students) in 12 departments work in research programs focusing on heart and vascular, cancer, brain, eye, metabolic, musculoskeletal, inflammatory and fibrotic diseases. The Lerner has more than 700,000 square feet of lab, office and scientific core services space. Lerner faculty oversee the curriculum and teach students enrolled in the Cleveland Clinic Lerner College of Medicine (CCLCM) of Case Western Reserve University - training the next generation of physician-scientists. Institute faculty also participate in multiple doctoral programs, including the Molecular Medicine PhD Program, which integrates traditional graduate training with an emphasis on human diseases. The Lerner is a significant source of commercial property, generating 64 invention disclosures, 15 licenses, 121 patents, and one new spinoff company in 2016. Visit us at http://www.lerner.ccf.org. Follow us on Twitter at http://www.twitter.com/CCLRI.

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