Researchers have discovered that people can gain a sense of spatial position and movement of their prostheses with a method that uses vibration of reinnervated muscles, which could allow the devices to become intuitively controllable. The research team developed an automated neural-machine interface that vibrated the muscles used for control of prosthetic hands. This system established kinesthetic sense, allowing the participants to control prosthetic hand movements in the absence of visual feedback and increasing their sense of agency. This approach could be an effective strategy for improving motor performance and quality of life in amputees.
Vibrating the muscles used for prosthetic control in specific locations and intensities via the neural-machine interface produced the illusory perception of complex grip movements. Within minutes, three people with amputations integrated this kinesthetic feedback and improved movement control of their prostheses, according to the study, which was published March 14 in Science Translational Medicine. In some cases, the participants were able to perform hand movements while blindfolded. The study says that combining intent, kinesthesia, and vision instilled participants with a sense of agency over the robotic movements. This feedback approach for closed-loop control opens a pathway to seamless integration of minds and machines.
The schematics represents perceived movements induced by 90-Hz vibration to the reinnervated residual muscles in six amputee participants..
Photograph courtesy of Science Translational Medicine.
Using a hand-held vibration unit, the researchers vibrated the proximal reinnervated residual muscles of six participants who used their intact hand to demonstrate what they felt. Every participant spontaneously reported perceiving functionally relevant complex movement in their missing hand, wrist, or elbow, and researchers isolated 22 individual movement percepts. Muscles reinnervated by the median nerve provided various percepts of digit flexion. Muscles reinnervated by the radial nerve provided percepts of extension. The perceived movements were experienced as synergistic hand gestures despite being elicited in the biceps, triceps, brachialis, and pectoralis, without cutaneous tactile correspondence in the overlying skin, according to the study.
The authors believe the results suggest that the sensory-neural structure of the elbow and shoulder muscles was reassigned through reinnervation by the nerves originally serving the hand.
