Periodic Reporting for period 2 - SOMA (Ultrasound peripheral interface and in-vitro model of human somatosensory system and muscles for motor decoding and restoration of somatic sensations in amputees)
Reporting period: 2021-09-01 to 2023-02-28
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 focused ultrasound (FUS). An in-depth analysis on animal models has been performed in order to investigate the feasibility of delivering an effective nerve peripheral stimulation through FUS probes. Therefore, the following alternative solutions to Ultrasound for eliciting the PNS were identified and are currently under investigation, 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, a still under analysis solution relying on infrared neural stimulation. Promising results were achieved by the gesture recognition approaches based on EMG signals acquired with ultrasound sensors. SOMA will profoundly improve the knowledge of the sensory afferent pathway providing for the first time an in-vitro model of the somatosensory system and muscle. The capability of this artificial skin in producing neural signals consistent with the afferent signals of a real in-vivo counterpart will be verified.
The mechanical design of the positioning system for the experimental studies on animals was accomplished. The relevant frequency range in the broad spectral range was also defined. Animal experiments to evaluate the US stimulation interface and its efficacy on the PNS were performed. The obtained results have shown that FUS stimulation does not appear to be a reliable method for constituting a useful nerve interface for use in humans and FUS induces functional impairment and structural damage to the peripheral nerve. Therefore, necessary changes in the strategy for the stimulation pathway in the SOMA project were implemented. Stimulation solutions that can provide an innovative and effective alternative to the originally hypothesized FUS were identified and are currently under investigation: 1) a fully implantable and wireless solution for electrical nerve stimulation, 2) an implant for electrically stimulating peripheral nerves that is supplied with energy wirelessly via ultrasound and also exchanges data via ultrasound, 3) a still under analysis solution relying on infrared neural stimulation.
A 32 element “transducer bracelet” consisting of individual 1 MHz transducers has been developed and used to for recording EMG signals.
Gesture recognition approaches based on EMG signals acquired with ultrasound sensors were developed and tested.
The characteristics of the somatosensory system to be integrated in the prosthetic hand were defined and the bio-inspired somatosensory system for hand prosthesis was developed and tested. The information provided by the sensors has been adopted as input to i) a new force-slippage-temperature control strategy able to guarantee an online reaction of the hand to external stimuli; ii) new encoding algorithms of mechanical, thermal and painful sensations. Encoding techniques for PNS stimulation, neurocomputational models to simulate the CNS response during US stimulation were developed and tested.
Human innervated skin and neuromuscular tissue were developed in vitro using primary human cells. A mechatronic testbed able to produce force, thermal and pain-related stimuli on both the in-vivo and in-vitro models was developed and tested.
Coordination and management were oriented to accomplish the objectives established in the CA.
Both internal and external dissemination activities have been performed.
A 32 element “transducer bracelet” consisting of individual 1 MHz transducers has been developed and used to for recording EMG signals.
Gesture recognition approaches based on EMG signals acquired with ultrasound sensors were developed and tested.
The characteristics of the somatosensory system to be integrated in the prosthetic hand were defined and the bio-inspired somatosensory system for hand prosthesis was developed and tested. The information provided by the sensors has been adopted as input to i) a new force-slippage-temperature control strategy able to guarantee an online reaction of the hand to external stimuli; ii) new encoding algorithms of mechanical, thermal and painful sensations. Encoding techniques for PNS stimulation, neurocomputational models to simulate the CNS response during US stimulation were developed and tested.
Human innervated skin and neuromuscular tissue were developed in vitro using primary human cells. A mechatronic testbed able to produce force, thermal and pain-related stimuli on both the in-vivo and in-vitro models was developed and tested.
Coordination and management were oriented to accomplish the objectives established in the CA.
Both internal and external dissemination activities have been performed.
Existing implantable systems for ultrasound recording are for imaging such as intravascular ultrasound imaging. Ultrasound recording of muscular signals are currently performed with bulky probes. Developing integrated circuits for miniaturised ultrasound recording of muscular signals is an advancement of the literature.
The SOMA project is advancing the literature thank to the Consortium findings, by means of experiments on animal models, that FUS stimulation cannot activate peripheral nerve axons. Therefore, new innovative solutions have been identified and are under investigation. Existing systems for electrical nerve stimulation are still bulky and not implantable. A fully implantable and wireless solution for electrical nerve stimulation is an incremental novelty with respect to the existing literature. To reduce the invasivity of the stimulation solution, still preserving selectivity, hybrid solutions combining ultrasound and electrical stimulation have been proposed in the literature. They still present technological limits, such as the limited number of stimulating channels, the absence of tunable stimulation parameters. A novel solution that will overcome the aforementioned limits will push beyond the state of the art.
The implementation of a Ultra Fast Ultrasound (UF US) platform capable of identifying single motor unit activity in voluntary contractions has achieved breakthrough novel results. Our method is the first one to combine HD sEMG decomposition and UF US for motor unit identification. With this framework, our experimental data collection and analysis are providing novel insights into muscle contraction and neural control of movements.
The application of B-mode ultrasound for gesture recognition has so far been applied for the classification of different gestures and contractions. Our studies have shown two novelties: i) we used a portable B-mode US system instead of a larger medical grade US; ii) we developed a regression approach, instead of a classification, demonstrating that the US-based regression is superior to the more established sEMG models.
A somatosensory system able to reproduce the human hand physiological characteristics and to replicate the huge variety of sensations felt by humans in the prosthetic system is still missing in the literature.
The information retrieved by a somatosensory system embedded in the prosthesis could be fundamental to ameliorate manipulation performance in several tasks and to restore multimodal somatic sensations, by means of new encoding approaches, with a significant impact on the user’s satisfaction.
The full validation of an artificial innervated skin and muscle biohybrid model based on three different types of stimulation tests (physical, TENS-based and FUS-based) is a novelty that will demonstrate its reliability and the consequent possibility of using it as an artificial testbed as alternative to a living animal.
Our innervated skin represents a unique model in which all components of extracellular matrix are endogenous and not synthetic materials present in the final tissue.
The SOMA project is advancing the literature thank to the Consortium findings, by means of experiments on animal models, that FUS stimulation cannot activate peripheral nerve axons. Therefore, new innovative solutions have been identified and are under investigation. Existing systems for electrical nerve stimulation are still bulky and not implantable. A fully implantable and wireless solution for electrical nerve stimulation is an incremental novelty with respect to the existing literature. To reduce the invasivity of the stimulation solution, still preserving selectivity, hybrid solutions combining ultrasound and electrical stimulation have been proposed in the literature. They still present technological limits, such as the limited number of stimulating channels, the absence of tunable stimulation parameters. A novel solution that will overcome the aforementioned limits will push beyond the state of the art.
The implementation of a Ultra Fast Ultrasound (UF US) platform capable of identifying single motor unit activity in voluntary contractions has achieved breakthrough novel results. Our method is the first one to combine HD sEMG decomposition and UF US for motor unit identification. With this framework, our experimental data collection and analysis are providing novel insights into muscle contraction and neural control of movements.
The application of B-mode ultrasound for gesture recognition has so far been applied for the classification of different gestures and contractions. Our studies have shown two novelties: i) we used a portable B-mode US system instead of a larger medical grade US; ii) we developed a regression approach, instead of a classification, demonstrating that the US-based regression is superior to the more established sEMG models.
A somatosensory system able to reproduce the human hand physiological characteristics and to replicate the huge variety of sensations felt by humans in the prosthetic system is still missing in the literature.
The information retrieved by a somatosensory system embedded in the prosthesis could be fundamental to ameliorate manipulation performance in several tasks and to restore multimodal somatic sensations, by means of new encoding approaches, with a significant impact on the user’s satisfaction.
The full validation of an artificial innervated skin and muscle biohybrid model based on three different types of stimulation tests (physical, TENS-based and FUS-based) is a novelty that will demonstrate its reliability and the consequent possibility of using it as an artificial testbed as alternative to a living animal.
Our innervated skin represents a unique model in which all components of extracellular matrix are endogenous and not synthetic materials present in the final tissue.