Worldwide, the number of people suffering from an arm amputation is estimated to 3 million, but there is a limited regular prosthetic use due also to lack of functionality. The potential of the development of closed-loop neuroprostheses can let SOMA significantly improve the quality of life of people who have suffered from an amputation. The SOMA project wants to develop a completely novel low invasive peripheral interface for restoring natural and multimodal tactile sensations in amputee subjects, with high selectivity and discrimination capabilities. The development of a bio-inspired sensory system, of bio-inspired control strategies and of encoding algorithms for peripheral stimulation aim at significantly improve manipulation capability and user acceptability of the prostheses. The project wants to investigate whether multiple somatic and close-to-natural sensations can be delivered in amputees via peripheral nerve stimulation. The extensive experimental work performed in the 2nd reporting period proved that FUS stimulation was unable to induce nerve electrical activity within a very large range of frequencies and parameters, and even more FUS at low frequencies caused damage to the stimulated nerve. Therefore, the following alternative solutions to Ultrasound for eliciting the PNS were identified and investigated, i.e. a fully implantable and wireless solution for electrical nerve stimulation, an ultrasonic wireless link through body tissue for communicating with an implanted electrical stimulation system. The SOMA stimulation systems, consisting of the implantable electrical stimulator linked to a US coin receiver were implanted in large animal model (i.e. a sheep) demonstrating that they work adequately for stimulating the peripheral nerve, through either extraneural or intraneural electrodes. Moreover, the US signals can control the protocols of stimulation delivered from the electrical stimulator.
Promising results were achieved by the gesture recognition approaches based on EMG signals acquired with ultrasound sensors.
The experimental validation of the SOMA neuroprosthetic system made on able-bodied and transradial amputee subjects demonstrated that the system effectively integrates sensory feedback to enhance upper-limb prosthetic control. By incorporating temperature, force, slippage, and pain perception, the system provides real-time bidirectional communication, allowing users to intuitively interpret sensory cues and adjust their actions accordingly.
SOMA will profoundly improve the knowledge of the sensory afferent pathway providing for the first time an in-vitro model that replicates the behaviour of the human somatosensory system and muscles. The capability of this artificial skin in producing neural signals consistent with the afferent signals of a real in-vivo counterpart have been verified.
