A team of international researchers have shown that motor information could be recorded using implantable interfaces connected with the peripheral nervous system (PNS). The study has implications for the development of neuro-controlled hand prostheses. The results of this research were published September 5 in the Journal of Neruoengineering and Rehabilitation.
The aim of this study was twofold: first, to verify whether “hand-related” actions (such as different grip types or movements of single fingers) can be decoded by processing neural motor-related signals recorded by longitudinal intrafascicular electrodes (LIFEs)-intrafascicular electrodes inserted longitudinally into the nerve; second, to increase the understanding of the basic mechanisms, as well as of the possibilities and limits of this approach.
LIFEs offer the ability to target specific nerve fibers and the procedure has a relatively low level of invasiveness required for their implantation as compared to targeted muscle reinnervation (TMR). They have also been used to control a one-degree of freedom hand prosthesis during short-term trials with amputees.
A new version of LIFEs, named thin-film LIFEs (tfLIFEs) were implanted in the median and ulnar nerves of the subject’s residual limb during a four-week trial. The trials on the recording of neural motor LIFE signals were carried out during the last week of experiments. Specifically, the subject was asked to separately and selectively dispatch the order to perform three movements-palmar grasp, pinch grasp, and flexion of the little finger-in response to images that were randomly presented to him on a computer screen. A spike-sorting and classification algorithm, developed by several members of the team, wwas used to record the LIFE motor signals.
The results showed that motor information (e.g., grip types and single-finger movements) could be extracted with classification accuracy around 85 percent and that the user could improve his ability to govern motor commands over time.
The researchers state that these results open up new and promising possibilities for the development of a neuro-controlled hand prosthesis. The use of implantable interfaces into the PNS could allow the restoration of the pre-existing neural connection-a more natural approach-which could allow the full usability of dexterous prostheses by the user who simply dispatches motor commands for hand movements as he normally did before amputation.
