We pioneered a human-machine system whereby prosthetic sensors readouts are translated into the language of the nervous system of three amputees, achieving significant health and functional benefits. In detail, natural sensory feedback can be restored in above-knee amputees and can be exploited by them to improve the use of the leg prosthesis during different ambulation tasks and to promote its integration in their body schema. We designed a neuroprosthesis to restore sensory feedback referred on the phantom lower limb of transfemoral amputees and triggered from the bionic leg by stimulating the residual tibial branch of the sciatic nerve through implanted neural interfaces (more than 10 Journal articles, including Nat Med, Sci Trans Med, Curr Bio, Sci Advances, Biomaterials, Nat Com).
The neuroprosthesis is constituted by alower limb prosthesis equipped with sensors under the foot sole and in the knee, a controlling microcomputer and a stimulating system. The policy of the biomimetic current injection in the nerve is designed with help of sophisticated computational models (published in several Journal articles, Nat Com, iScience etc.) which emulate the neurophysiology of the peripheral nerve fibers transmission of the information. Then, nature does the rest: the signals from the residual nerves are conveyed to the brain of the person, to perceive what happens at the prosthesis and to adjust the walking accordingly. The machine and the body are finally re-connected. Together with the functional outcomes, we assessed the cognitive (brain) integration of the device into the body schema of the subjects through measurements of prosthesis embodiment and cognitive effort while using the artificial leg. Then, thanks to the full portability and real-time operation of our novel hardware and software system, amputees stepped out form the lab to the ecological environment, proving that our approach promoted mobility over sand, diminished metabolic cost and therefore overall usability fo the device. The results from these proof-of-concept provide the rationale for larger population studies .
Analogous system has been developed then for the diabetic neuropathy, and tested with several patients. We have modified the stimulating device into the non-invasive, easy to wear smart-stimulating sock, with several active electrodes. By means of the properly developed AI-based policy of stimulation (published in JNE, JNER, NatCom) we enabled the restoration of missing sensations from the diabetic feet, and their proper integration within body schema of patients.
Overall, FeelAgain project delivered 1. several computational models of the human nervous system (sciatic nerve, pudendal nerve, vagus nerve), usable in research and clinical applications worldwide, 2. novel sophisticate assessment tools for clinical research, 3. first in-human neuroprostheses with their clinical validation. All these pave the way for further research about how the brain interpretation of artificial feedback and for the development of sensory-enhanced leg neuroprostheses, which could drastically ameliorate life quality in people with disability.
