Periodic Reporting for period 3 - SOMA (Ultrasound peripheral interface and in-vitro model of human somatosensory system and muscles for motor decoding and restoration of somatic sensations in amputees)
Berichtszeitraum: 2023-03-01 bis 2025-02-28
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 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.
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.
Animal experiments were conducted to evaluate the US stimulation interface and its effects on the PNS. The results showed that FUS stimulation is not a reliable method for creating a useful nerve interface in humans, as it causes functional impairment and structural nerve damage. As a result, alternative stimulation solutions were identified, developed, and validated in the 3rd reporting period: 1) a fully implantable and wireless electrical nerve stimulation solution, 2) an implantable system stimulating peripheral nerves wirelessly via ultrasound and exchanging data, and 3) a non-invasive transcutaneous electrical nerve stimulation approach integrated into a closed-loop prosthetic wrist-hand, aimed at enhancing upper-limb prosthetic control.
An optimized version of intraneural electrodes and a 32-element “transducer bracelet” for recording EMG signals were developed. Gesture recognition based on EMG signals from ultrasound sensors was tested. The characteristics of the somatosensory system for the prosthetic hand were defined, and a bio-inspired system was tested. The sensors provided input to i) a new control strategy for the hand’s response to external stimuli, and ii) new encoding algorithms for mechanical, thermal, and pain sensations. Techniques for PNS stimulation and models for simulating CNS responses during US stimulation were developed and tested.
Hardware and software modules were integrated to build the SOMA neuroprosthetic system, which was tested on able-bodied and amputee subjects using non-invasive PNS stimulation. The functionality of the fully implantable electrical stimulator and hybrid US-electrical system was tested on animal models. Human innervated skin and neuromuscular tissue were developed in vitro, and a mechatronic testbed was created to produce force, thermal, and pain-related stimuli on both in-vivo and in-vitro models. Coordination and management efforts aimed at meeting the project objectives, with internal and external dissemination activities completed.
An optimized version of intraneural electrodes and a 32-element “transducer bracelet” for recording EMG signals were developed. Gesture recognition based on EMG signals from ultrasound sensors was tested. The characteristics of the somatosensory system for the prosthetic hand were defined, and a bio-inspired system was tested. The sensors provided input to i) a new control strategy for the hand’s response to external stimuli, and ii) new encoding algorithms for mechanical, thermal, and pain sensations. Techniques for PNS stimulation and models for simulating CNS responses during US stimulation were developed and tested.
Hardware and software modules were integrated to build the SOMA neuroprosthetic system, which was tested on able-bodied and amputee subjects using non-invasive PNS stimulation. The functionality of the fully implantable electrical stimulator and hybrid US-electrical system was tested on animal models. Human innervated skin and neuromuscular tissue were developed in vitro, and a mechatronic testbed was created to produce force, thermal, and pain-related stimuli on both in-vivo and in-vitro models. Coordination and management efforts aimed at meeting the project objectives, with internal and external dissemination activities completed.
Existing implantable systems for ultrasound recording are mainly used for imaging, such as intravascular ultrasound. Ultrasound recording of muscular signals is typically done with bulky probes. Developing miniaturized integrated circuits for ultrasound recording of muscular signals represents an advancement in the field.
The SOMA project advances the literature through findings from animal model experiments, showing that FUS stimulation cannot activate peripheral nerve axons. Innovative solutions have been developed, with a focus on electrical nerve stimulation. While existing systems are still bulky and not implantable, a fully implantable and wireless solution for nerve stimulation marks a significant innovation. Hybrid solutions combining ultrasound and electrical stimulation have been proposed but still have limitations, such as few stimulating channels and a lack of tunable stimulation parameters. The SOMA project overcomes these issues, pushing beyond the current state of the art.
The implementation of an Ultra Fast Ultrasound (UF US) platform for identifying single motor unit activity in voluntary contractions has led to breakthrough results. Our method combines HD sEMG decomposition and UF US for motor unit identification, providing new insights into muscle contraction and neural control.
B-mode ultrasound for gesture recognition has been used for classifying gestures, but our studies introduced two novelties: i) using a portable B-mode US system rather than a large medical-grade system, and ii) developing a regression approach, showing that US-based regression outperforms sEMG models.
A somatosensory system replicating human hand characteristics and sensations in prosthetics is still lacking. Information from such a system could improve manipulation performance and restore somatic sensations, enhancing user satisfaction.
The validation of an artificial innervated skin and muscle biohybrid model represents a novelty that could serve as an alternative to animal testing. Our innervated skin model uses endogenous components, not synthetic materials.
Finally, the closed-loop neuroprosthetic system developed in this project represents a major advancement, capable of accurately recognizing motion intentions and providing close-to-natural somatic sensations in a somatotopic manner.
The SOMA project advances the literature through findings from animal model experiments, showing that FUS stimulation cannot activate peripheral nerve axons. Innovative solutions have been developed, with a focus on electrical nerve stimulation. While existing systems are still bulky and not implantable, a fully implantable and wireless solution for nerve stimulation marks a significant innovation. Hybrid solutions combining ultrasound and electrical stimulation have been proposed but still have limitations, such as few stimulating channels and a lack of tunable stimulation parameters. The SOMA project overcomes these issues, pushing beyond the current state of the art.
The implementation of an Ultra Fast Ultrasound (UF US) platform for identifying single motor unit activity in voluntary contractions has led to breakthrough results. Our method combines HD sEMG decomposition and UF US for motor unit identification, providing new insights into muscle contraction and neural control.
B-mode ultrasound for gesture recognition has been used for classifying gestures, but our studies introduced two novelties: i) using a portable B-mode US system rather than a large medical-grade system, and ii) developing a regression approach, showing that US-based regression outperforms sEMG models.
A somatosensory system replicating human hand characteristics and sensations in prosthetics is still lacking. Information from such a system could improve manipulation performance and restore somatic sensations, enhancing user satisfaction.
The validation of an artificial innervated skin and muscle biohybrid model represents a novelty that could serve as an alternative to animal testing. Our innervated skin model uses endogenous components, not synthetic materials.
Finally, the closed-loop neuroprosthetic system developed in this project represents a major advancement, capable of accurately recognizing motion intentions and providing close-to-natural somatic sensations in a somatotopic manner.