The embodiment of assistive devices-from wheelchair to exoskeleton

Robotic exoskeleton embodiment in post-stroke hemiparetic patients: an experimental study about the integration of the assistance provided by the REFLEX knee exoskeleton

Hemiparetic gait is the most common motor-disorder after stroke and, in spite of rehabilitation efforts, it is persistent in 50% of community dwelling stroke-survivors. Robotic exoskeletons have been proposed as assistive devices to support impaired joints. An example of these devices is the REFLEX knee exoskeleton, which assists the gait of hemiparetic subjects and whose action seems to be properly embodied by stroke survivors, who were able to adapt the motion of their non-assisted limbs and, therefore, reduce their compensation mechanisms. This paper presents an experimental validation carried out to deepen into the effects of REFLEX's assistance in hemiparetic subjects. Special attention was paid to the effect produced in the muscular activity as a metric to evaluate the embodiment of this technology. Significant differences were obtained at the subject level due to the assistance; however, the high dispersion of the measured outcomes avoided extracting global effects at the group level. These results highlight the need of individually tailoring the action of the robot to the individual needs of each patient to maximize the beneficial outcomes. Extra research effort should be done to elucidate the neural mechanisms involved in the embodiment of external devices by stroke survivors.

Continuous synthesis of artificial speech sounds from human cortical surface recordings during silent speech production

Objective. Brain-computer interfaces can restore various forms of communication in paralyzed patients who have lost their ability to articulate intelligible speech. This study aimed to demonstrate the feasibility of closed-loop synthesis of artificial speech sounds from human cortical surface recordings during silent speech production.Approach. Ten participants with intractable epilepsy were temporarily implanted with intracranial electrode arrays over cortical surfaces. A decoding model that predicted audible outputs directly from patient-specific neural feature inputs was trained during overt word reading and immediately tested with overt, mimed and imagined word reading. Predicted outputs were later assessed objectively against corresponding voice recordings and subjectively through human perceptual judgments.Main results. Artificial speech sounds were successfully synthesized during overt and mimed utterances by two participants with some coverage of the precentral gyrus. About a third of these sounds were correctly identified by naïve listeners in two-alternative forced-choice tasks. A similar outcome could not be achieved during imagined utterances by any of the participants. However, neural feature contribution analyses suggested the presence of exploitable activation patterns during imagined speech in the postcentral gyrus and the superior temporal gyrus. In future work, a more comprehensive coverage of cortical surfaces, including posterior parts of the middle frontal gyrus and the inferior frontal gyrus, could improve synthesis performance during imagined speech.Significance.As the field of speech neuroprostheses is rapidly moving toward clinical trials, this study addressed important considerations about task instructions and brain coverage when conducting research on silent speech with non-target participants.

Human Exteroception during Object Handling with an Upper Limb Exoskeleton

Upper limb exoskeletons may confer significant mechanical advantages across a range of tasks. The potential consequences of the exoskeleton upon the user's sensorimotor capacities however, remain poorly understood. The purpose of this study was to examine how the physical coupling of the user's arm to an upper limb exoskeleton influenced the perception of handheld objects. In the experimental protocol, participants were required to estimate the length of a series of bars held in their dominant right hand, in the absence of visual feedback. Their performance in conditions with an exoskeleton fixed to the forearm and upper arm was compared to conditions without the upper limb exoskeleton. Experiment 1 was designed to verify the effects of attaching an exoskeleton to the upper limb, with object handling limited to rotations of the wrist only. Experiment 2 was designed to verify the effects of the structure, and its mass, with combined movements of the wrist, elbow, and shoulder. Statistical analysis indicated that movements performed with the exoskeleton did not significantly affect perception of the handheld object in experiment 1 (BF₀₁ = 2.3) or experiment 2 (BF₀₁ = 4.3). These findings suggest that while the integration of an exoskeleton complexifies the architecture of the upper limb effector, this does not necessarily impede transmission of the mechanical information required for human exteroception.

Hybrid brain/neural interface and autonomous vision-guided whole-arm exoskeleton control to perform activities of daily living (ADLs)

BACKGROUND

The aging of the population and the progressive increase of life expectancy in developed countries is leading to a high incidence of age-related cerebrovascular diseases, which affect people's motor and cognitive capabilities and might result in the loss of arm and hand functions. Such conditions have a detrimental impact on people's quality of life. Assistive robots have been developed to help people with motor or cognitive disabilities to perform activities of daily living (ADLs) independently. Most of the robotic systems for assisting on ADLs proposed in the state of the art are mainly external manipulators and exoskeletal devices. The main objective of this study is to compare the performance of an hybrid EEG/EOG interface to perform ADLs when the user is controlling an exoskeleton rather than using an external manipulator.

METHODS

Ten impaired participants (5 males and 5 females, mean age 52 ± 16 years) were instructed to use both systems to perform a drinking task and a pouring task comprising multiple subtasks. For each device, two modes of operation were studied: synchronous mode (the user received a visual cue indicating the sub-tasks to be performed at each time) and asynchronous mode (the user started and finished each of the sub-tasks independently). Fluent control was assumed when the time for successful initializations ranged below 3 s and a reliable control in case it remained below 5 s. NASA-TLX questionnaire was used to evaluate the task workload. For the trials involving the use of the exoskeleton, a custom Likert-Scale questionnaire was used to evaluate the user's experience in terms of perceived comfort, safety, and reliability.

RESULTS

All participants were able to control both systems fluently and reliably. However, results suggest better performances of the exoskeleton over the external manipulator (75% successful initializations remain below 3 s in case of the exoskeleton and bellow 5s in case of the external manipulator).

CONCLUSIONS

Although the results of our study in terms of fluency and reliability of EEG control suggest better performances of the exoskeleton over the external manipulator, such results cannot be considered conclusive, due to the heterogeneity of the population under test and the relatively limited number of participants.

Embodiment for Robotic Lower-Limb Exoskeletons: A Narrative Review

Research on embodiment of objects external to the human body has revealed important information about how the human nervous system interacts with robotic lower limb exoskeletons. Typical robotic exoskeleton control approaches view the controllers as an external agent intending to move in coordination with the human. However, principles of embodiment suggest that the exoskeleton controller should ideally coordinate with the human such that the nervous system can adequately model the input-output dynamics of the exoskeleton controller. Measuring embodiment of exoskeletons should be a necessary step in the exoskeleton development and prototyping process. Researchers need to establish high fidelity quantitative measures of embodiment, rather than relying on current qualitative survey measures. Mobile brain imaging techniques, such as high-density electroencephalography, is likely to provide a deeper understanding of embodiment during human-machine interactions and advance exoskeleton research and development. In this review we show why future exoskeleton research should include quantitative measures of embodiment as a metric of success.

Integrated Neuroregenerative Techniques for Plasticity of the Injured Spinal Cord

On the slow path to improving the life expectancy and quality of life of patients post spinal cord injury (SCI), recovery remains controversial. The potential role of the regenerative capacity of the nervous system has led to numerous attempts to stimulate the SCI to re-establish the interrupted sensorimotor loop and to understand its potential in the recovery process. Numerous resources are now available, from pharmacological to biomolecular approaches and from neuromodulation to sensorimotor rehabilitation interventions based on the use of various neural interfaces, exoskeletons, and virtual reality applications. The integration of existing resources seems to be a promising field of research, especially from the perspective of improving living conditions in the short to medium term. Goals such as reducing chronic forms of neuropathic pain, regaining control over certain physiological activities, and enhancing residual abilities are often more urgent than complete functional recovery. In this perspective article, we provide an overview of the latest interventions for the treatment of SCI through broad phases of injury rehabilitation. The underlying intention of this work is to introduce a spinal cord neuroplasticity-based multimodal approach to promote functional recovery and improve quality of life after SCI. Nonetheless, when used separately, biomolecular therapeutic approaches have been shown to have modest outcomes.

Investigating User Volitional Influence on Step Length in Powered Exoskeleton Designed for Users with SCI

Volitional movement from users of assistive lower limb exoskeletons may be exploited to increase the controlled variability in the movements of a human-exoskeleton system. This may in turn allow these devices to handle the variability encountered in the terrain of everyday life. This study aimed to investigate the degree to which users can volitionally influence step length, when using an assistive exoskeleton designed for users with spinal cord injury (SCI) running a fixed robotic exoskeleton trajectory. An experiment was conducted to investigate the accessible range of step lengths when five able-bodied participants and one participant with SCI piloted a user-balanced exoskeleton. Participants were asked to take steps as large as possible ("large") and as small as possible ("small"), with the able-bodied individuals asked to minimise use of their leg muscles, with step length of each step measured. Surface electromyography (sEMG) data were collected on major leg muscles of the able-bodied subjects to monitor their muscle activities with a novel processing method introduced to facilitate discussion in the context of users with SCI. The results demonstrate that a user can intentionally manipulate the resulting step length, with every participant having significantly different large and small step sizes (p < 0.05). However, large variations were observed between individuals in terms of absolute step lengths and difference between large and small steps. Moreover, the range of step length (normalised by the leg length) ranged from 0.237 to 0.375 for the able-bodied subjects and 0.245 for the individual with SCI. Although positive correlation was present between the sEMG data and resulting step lengths, the result was not statistically significant (p > 0.05).

Future Treatment of Neuropathic Pain in Spinal Cord Injury: The Challenges of Nanomedicine, Supplements or Opportunities?

Neuropathic pain (NP) is a common chronic condition that severely affects patients with spinal cord injuries (SCI). It impairs the overall quality of life and is considered difficult to treat. Currently, clinical management of NP is often limited to drug therapy, primarily with opioid analgesics that have limited therapeutic efficacy. The persistence and intractability of NP following SCI and the potential health risks associated with opioids necessitate improved treatment approaches. Nanomedicine has gained increasing attention in recent years for its potential to improve therapeutic efficacy while minimizing toxicity by providing sensitive and targeted treatments that overcome the limitations of conventional pain medications. The current perspective begins with a brief discussion of the pathophysiological mechanisms underlying NP and the current pain treatment for SCI. We discuss the most frequently used nanomaterials in pain diagnosis and treatment as well as recent and ongoing efforts to effectively treat pain by proactively mediating pain signals following SCI. Although nanomedicine is a rapidly growing field, its application to NP in SCI is still limited. Therefore, additional work is required to improve the current treatment of NP following SCI.

Coordination Between Partial Robotic Exoskeletons and Human Gait: A Comprehensive Review on Control Strategies

Lower-limb robotic exoskeletons have become powerful tools to assist or rehabilitate the gait of subjects with impaired walking, even when they are designed to act only partially over the locomotor system, as in the case of unilateral or single-joint exoskeletons. These partial exoskeletons require a proper method to synchronize their assistive actions and ensure correct inter-joint coordination with the user’s gait. This review analyzes the state of the art of control strategies to coordinate the assistance provided by these partial devices with the actual gait of the wearers. We have analyzed and classified the different approaches independently of the hardware implementation, describing their basis and principles. We have also reviewed the experimental validations of these devices for impaired and unimpaired walking subjects to provide the reader with a clear view of their technology readiness level. Eventually, the current state of the art and necessary future steps in the field are summarized and discussed.

Embodiment Comfort Levels During Motor Imagery Training Combined With Immersive Virtual Reality in a Spinal Cord Injury Patient

Brain-machine interfaces combining visual, auditory, and tactile feedback have been previously used to generate embodiment experiences during spinal cord injury (SCI) rehabilitation. It is not known if adding temperature to these modalities can result in discomfort with embodiment experiences. Here, comfort levels with the embodiment experiences were investigated in an intervention that required a chronic pain SCI patient to generate lower limb motor imagery commands in an immersive environment combining visual (virtual reality -VR), auditory, tactile, and thermal feedback. Assessments were made pre-/ post-, throughout the intervention (Weeks 0-5), and at 7 weeks follow up. Overall, high levels of embodiment in the adapted three-domain scale of embodiment were found throughout the sessions. No significant adverse effects of VR were reported. Although sessions induced only a modest reduction in pain levels, an overall reduction occurred in all pain scales (Faces, Intensity, and Verbal) at follow up. A high degree of comfort in the comfort scale for the thermal-tactile sleeve, in both the thermal and tactile feedback components of the sleeve was reported. This study supports the feasibility of combining multimodal stimulation involving visual (VR), auditory, tactile, and thermal feedback to generate embodiment experiences in neurorehabilitation programs.

A Differentiable Dynamic Model for Musculoskeletal Simulation and Exoskeleton Control

An exoskeleton, a wearable device, was designed based on the user's physical and cognitive interactions. The control of the exoskeleton uses biomedical signals reflecting the user intention as input, and its algorithm is calculated as an output to make the movement smooth. However, the process of transforming the input of biomedical signals, such as electromyography (EMG), into the output of adjusting the torque and angle of the exoskeleton is limited by a finite time lag and precision of trajectory prediction, which result in a mismatch between the subject and exoskeleton. Here, we propose an EMG-based single-joint exoskeleton system by merging a differentiable continuous system with a dynamic musculoskeletal model. The parameters of each muscle contraction were calculated and applied to the rigid exoskeleton system to predict the precise trajectory. The results revealed accurate torque and angle prediction for the knee exoskeleton and good performance of assistance during movement. Our method outperformed other models regarding the rate of convergence and execution time. In conclusion, a differentiable continuous system merged with a dynamic musculoskeletal model supported the effective and accurate performance of an exoskeleton controlled by EMG signals.

Subjective Response Measurement to Prosthesis or Device Use: Validation of the Prosthetic-Bionic Paradigm Questionnaire (PBP-Q)

Many subjects with somatic pathologies or traumas in their recent anamnesis tend to experience symptoms and changes to their daily life parameters after technically successful treatment. Hence, this study aims to validate an investigation tool inspired by the prosthetic-bionic paradigm-namely, the PBP-Q-which allows for the evaluation of variation in questions relating to identity, psychosociality, and psychopathology in relation to the use of a prosthesis or device. We gathered 118 participants (68 females and 50 males) aged between 27 and 94 years (Mean = 58.42 ± 15.17). We performed both exploratory (EFA) and confirmatory (CFA) factor analyses on this sample. Moreover, we calculated the internal consistency for the PBP-Q scales and the total score for the questionnaire's final 26-item and 5-factor versions. The five scales are psychological well-being; interpersonal relationships; professional relationships; autonomy and safety; addictions, compulsions, and obsessions. The internal consistency is good for both the total score and the subscales. In conclusion, overall, the PBP-Q has satisfactory psychometric properties, especially considering the measure's complexity. It provides a quick and effective way to evaluate the changes that might arise after the use of a prosthesis or device and, subsequently, has implications for clinical practice.

Towards Robot-Assisted Therapy for Children With Autism—The Ontological Knowledge Models and Reinforcement Learning-Based Algorithms

Robots are more and more present in our lives, particularly in the health sector. In therapeutic centers, some therapists are beginning to explore various tools like video games, Internet exchanges, and robot-assisted therapy. These tools will be at the disposal of these professionals as additional resources that can support them to assist their patients intuitively and remotely. The humanoid robot can capture young children’s attention and then attract the attention of researchers. It can be considered as a play partner and can directly interact with children or without a third party’s presence. It can equally perform repetitive tasks that humans cannot achieve in the same way. Moreover, humanoid robots can assist a therapist by allowing him to teleoperated and interact from a distance. In this context, our research focuses on robot-assisted therapy and introduces a humanoid social robot in a pediatric hospital care unit. That will be performed by analyzing many aspects of the child’s behavior, such as verbal interactions, gestures and facial expressions, etc. Consequently, the robot can reproduce consistent experiences and actions for children with communication capacity restrictions. This work is done by applying a novel approach based on deep learning and reinforcement learning algorithms supported by an ontological knowledge base that contains relevant information and knowledge about patients, screening tests, and therapies. In this study, we realized a humanoid robot that will assist a therapist by equipping the robot NAO: 1) to detect whether a child is autistic or not using a convolutional neural network, 2) to recommend a set of therapies based on a selection algorithm using a correspondence matrix between screening test and therapies, and 2) to assist and monitor autistic children by executing tasks that require those therapies.

Exoskeletons for Mobility after Spinal Cord Injury: A Personalized Embodied Approach

Endowed with inherent flexibility, wearable robotic technologies are powerful devices that are known to extend bodily functionality to assist people with spinal cord injuries (SCIs). However, rather than considering the specific psychological and other physiological needs of their users, these devices are specifically designed to compensate for motor impairment. This could partially explain why they still cannot be adopted as an everyday solution, as only a small number of patients use lower-limb exoskeletons. It remains uncertain how these devices can be appropriately embedded in mental representations of the body. From this perspective, we aimed to highlight the homeostatic role of autonomic and interoceptive signals and their possible integration in a personalized experience of exoskeleton overground walking. To ensure personalized user-centered robotic technologies, optimal robotic devices should be designed and adjusted according to the patient's condition. We discuss how embodied approaches could emerge as a means of overcoming the hesitancy toward wearable robots.

On the psychological origins of tool use

The ubiquity of tool use in human life has generated multiple lines of scientific and philosophical investigation to understand the development and expression of humans' engagement with tools and its relation to other dimensions of human experience. However, existing literature on tool use faces several epistemological challenges in which the same set of questions generate many different answers. At least four critical questions can be identified, which are intimately intertwined-(1) What constitutes tool use? (2) What psychological processes underlie tool use in humans and nonhuman animals? (3) Which of these psychological processes are exclusive to tool use? (4) Which psychological processes involved in tool use are exclusive to Homo sapiens? To help advance a multidisciplinary scientific understanding of tool use, six author groups representing different academic disciplines (e.g., anthropology, psychology, neuroscience) and different theoretical perspectives respond to each of these questions, and then point to the direction of future work on tool use. We find that while there are marked differences among the responses of the respective author groups to each question, there is a surprising degree of agreement about many essential concepts and questions. We believe that this interdisciplinary and intertheoretical discussion will foster a more comprehensive understanding of tool use than any one of these perspectives (or any one of these author groups) would (or could) on their own.

Maladaptive reorganization following SCI: The role of body representation and multisensory integration

In this review we focus on maladaptive brain reorganization after spinal cord injury (SCI), including the development of neuropathic pain, and its relationship with impairments in body representation and multisensory integration. We will discuss the implications of altered sensorimotor interactions after SCI with and without neuropathic pain and possible deficits in multisensory integration and body representation. Within this framework we will examine published research findings focused on the use of bodily illusions to manipulate multisensory body representation to induce analgesic effects in heterogeneous chronic pain populations and in SCI-related neuropathic pain. We propose that the development and intensification of neuropathic pain after SCI is partly dependent on brain reorganization associated with dysfunctional multisensory integration processes and distorted body representation. We conclude this review by suggesting future research avenues that may lead to a better understanding of the complex mechanisms underlying the sense of the body after SCI, with a focus on cortical changes.

Exploring the Embodiment of a Virtual Hand in a Spatially Augmented Respiratory Biofeedback Setting

Enhancing the embodiment of artificial limbs—the individuals' feeling that a virtual or robotic limb is integrated in their own body scheme—is an impactful strategy for improving prosthetic technology acceptance and human-machine interaction. Most studies so far focused on visuo-tactile strategies to empower the embodiment processes. However, novel approaches could emerge from self-regulation techniques able to change the psychophysiological conditions of an individual. Accordingly, this pilot study investigates the effects of a self-regulated breathing exercise on the processes of body ownership underlying the embodiment of a virtual right hand within a Spatially Augmented Respiratory Biofeedback (SARB) setting. This investigation also aims at evaluating the feasibility of the breathing exercise enabled by a low-cost SARB implementation designed for upcoming remote studies (a need emerged during the COVID-19 pandemic). Twenty-two subjects without impairments, and two transradial prosthesis users for a preparatory test, were asked (in each condition of a within-group design) to maintain a normal (about 14 breaths/min) or slow (about 6 breaths/min) respiratory rate to keep a static virtual right hand “visible” on a screen. Meanwhile, a computer-generated sphere moved from left to right toward the virtual hand during each trial (1 min) of 16. If the participant's breathing rate was within the target (slow or normal) range, a visuo-tactile event was triggered by the sphere passing under the virtual hand (the subjects observed it shaking while they perceived a vibratory feedback generated by a smartphone). Our results—mainly based on questionnaire scores and proprioceptive drift—highlight that the slow breathing condition induced higher embodiment than the normal one. This preliminary study reveals the feasibility and potential of a novel psychophysiological training strategy to enhance the embodiment of artificial limbs. Future studies are needed to further investigate mechanisms, efficacy and generalizability of the SARB techniques in training a bionic limb embodiment.

Little evidence for an effect of the rubber hand illusion on basic movement

Body ownership refers to the distinct sensation that our observed body belongs to us, which is believed to stem from multisensory integration. This is commonly shown through the rubber hand illusion (RHI), which induces a sense of ownership over a false limb. Whilst the RHI may interfere with object-directed action and alter motor cortical activity, it is not yet clear whether a sense of ownership over an artificial hand has functional consequences for movement production per se. As such, we performed two motion-tracking experiments (n = 117) to examine the effects of the RHI on the reaction time, acceleration, and velocity of rapid index finger abduction. We observed little convincing evidence that the induction of the RHI altered these kinematic variables. Moreover, the subjective sensations of rubber hand ownership, referral of touch, and agency did not convincingly correlate with kinematic variables, and nor did proprioceptive drift, suggesting that changes in body representation elicited by the RHI may not influence basic movement. Whilst experiment 1 suggested that individuals reporting a greater sensation of the real hand disappearing performed movements with smaller acceleration and velocity following illusion induction, we did not replicate this effect in a second experiment, suggesting that these effects may be small or not particularly robust. Overall, these results indicate that manipulating the conscious experience of body ownership has little impact on basic motor control, at least in the RHI with healthy participants.

Pain Reduction after Short Exposure to Virtual Reality Environments in People with Spinal Cord Injury

Emerging literature suggests that virtual reality (VR) may be a viable therapy for neuropathic pain (NP). This pilot study aimed to investigate the immediate effect of VR in reducing NP in people with spinal cord injury (SCI). Eight individuals with chronic NP after SCI were recruited and underwent consecutive exposure to scenery and somatic virtual environments (VE). The numeric rating scale (NRS) was used to assess pain before and after exposure to each VE. The Immersive Tendencies Questionnaire (ITQ) and Presence Questionnaire (UQO-PQ) were used to investigate the interaction between reported pain relief post-intervention with immersion and presence. There was a significant reduction in pain levels (5.1 ± 0.4, mean ± SEM) after short exposure to the scenery (3.1 ± 0.7, p = 0.04) and somatic VE (3.0 ± 0.7, p = 0.04), with no difference between intervention types (p = 0.56). There was a statistically significant negative correlation between the total ITQ score and the change in NRS after the scenery VR intervention (r_s = 0.743, p = 0.035). PQ scores showed no significant correlation with changes in pain following either intervention type. We found that short-term exposure to VR environments results in a reduction in chronic NP intensity in people with SCI.

Rebuilding Body-Brain Interaction from the Vagal Network in Spinal Cord Injuries

Spinal cord injuries (SCIs) exert devastating effects on body awareness, leading to the disruption of the transmission of sensory and motor inputs. Researchers have attempted to improve perceived body awareness post-SCI by intervening at the multisensory level, with the integration of somatic sensory and motor signals. However, the contributions of interoceptive-visceral inputs, particularly the potential interaction of motor and interoceptive signals, remain largely unaddressed. The present perspective aims to shed light on the use of interoceptive signals as a significant resource for patients with SCI to experience a complete sense of body awareness. First, we describe interoceptive signals as a significant obstacle preventing such patients from experiencing body awareness. Second, we discuss the multi-level mechanisms associated with the homeostatic stability of the body, which creates a unified, coherent experience of one's self and one's body, including real-time updates. Body awareness can be enhanced by targeting the vagus nerve function by, for example, applying transcutaneous vagus nerve stimulation. This perspective offers a potentially useful insight for researchers and healthcare professionals, allowing them to be better equipped in SCI therapy. This will lead to improved sensory motor and interoceptive signals, a decreased likelihood of developing deafferentation pain, and the successful implementation of modern robotic technologies.

Are Functional Measures Sufficient to Capture Acceptance? A Qualitative Study on Lower Limb Exoskeleton Use for Older People

Lower limb exoskeletons (LLE) are robotic devices developed to assist walk. In the field of healthcare, this technology has been available for almost a decade, yet it still faces important acceptance issues. While LLE were first developed for patients with spinal cord injuries, we expect their use to expand to everyday settings to benefit other populations, namely that of older people with reduced mobility (RM). We propose a qualitative approach to unearth key psychosocial themes on the acceptance of LLE in daily living for older people. The study analyses perceptions of older people with RM, as well as their entourage, including informal and professional caregivers. Using a grounded theory approach we analysed 12 semi-structured interviews with older people with RM; 2 focus groups with informal caregivers, and 2 focus groups with professional caregivers. LLE were introduced to participants through photo-elicitation. Older people with RM believed that LLE would increase their autonomy. They also perceived that using LLE would make them feel less of a burden for their entourage. Beyond these expected benefits, results captured participants’ ambivalence, dependent on their experiences of the ageing process and perceptions on the human–machine interaction. Informal caregivers highlighted that LLE could provide important relief related to the burden of care. Nonetheless, professional caregivers raised the fear of LLE leading to dehumanization of care. While each group had specific concerns on how LLE use would impact their lives, psychosocial considerations played a key role in LLE acceptance.

Review: How Can Intelligent Robots and Smart Mechatronic Modules Facilitate Remote Assessment, Assistance, and Rehabilitation for Isolated Adults With Neuro-Musculoskeletal Conditions?

Worldwide, at the time this article was written, there are over 127 million cases of patients with a confirmed link to COVID-19 and about 2.78 million deaths reported. With limited access to vaccine or strong antiviral treatment for the novel coronavirus, actions in terms of prevention and containment of the virus transmission rely mostly on social distancing among susceptible and high-risk populations. Aside from the direct challenges posed by the novel coronavirus pandemic, there are serious and growing secondary consequences caused by the physical distancing and isolation guidelines, among vulnerable populations. Moreover, the healthcare system's resources and capacity have been focused on addressing the COVID-19 pandemic, causing less urgent care, such as physical neurorehabilitation and assessment, to be paused, canceled, or delayed. Overall, this has left elderly adults, in particular those with neuromusculoskeletal (NMSK) conditions, without the required service support. However, in many cases, such as stroke, the available time window of recovery through rehabilitation is limited since neural plasticity decays quickly with time. Given that future waves of the outbreak are expected in the coming months worldwide, it is important to discuss the possibility of using available technologies to address this issue, as societies have a duty to protect the most vulnerable populations. In this perspective review article, we argue that intelligent robotics and wearable technologies can help with remote delivery of assessment, assistance, and rehabilitation services while physical distancing and isolation measures are in place to curtail the spread of the virus. By supporting patients and medical professionals during this pandemic, robots, and smart digital mechatronic systems can reduce the non-COVID-19 burden on healthcare systems. Digital health and cloud telehealth solutions that can complement remote delivery of assessment and physical rehabilitation services will be the subject of discussion in this article due to their potential in enabling more effective and safer NMSDK rehabilitation, assistance, and assessment service delivery. This article will hopefully lead to an interdisciplinary dialogue between the medical and engineering sectors, stake holders, and policy makers for a better delivery of care for those with NMSK conditions during a global health crisis including future pandemics.

Embodied cognition: So flexible as to be "disembodied"?

This review aims to explore what I call the "Embodiment Cost Hypothesis" (ECH), according to which, when humans "embody" a part of the world other than their bodies, a measurable cost is detectable on their real bodies. The review analyzes experimental evidence in favor of the ECH by examining studies from different research fields, including studies of action observation (2), tool-use (3), rubber hand illusion (4), and full-body illusions (5). In light of this literature, this review argues that embodiment effects can profitably be seen as phenomena associated with both benefits (resulting from the embodiment of external objects/bodies) and costs (resulting from the disembodiment at various levels of the subject's own body). Implications are discussed in relation to the ongoing debate on the embodied cognition (EC) approach.

"It's not my knee" - understanding ongoing pain and discomfort after total knee replacement through (re)embodiment

Objective

Up to 20% of people who undergo total knee replacement surgery have ongoing pain and discomfort. The aim of this study was to understand what role the concepts of embodiment (of both having a body and experiencing the world through one's body) and incorporation (integrating something into one's body) might have in understanding experiences of pain and discomfort after total knee replacement.

Methods

We conducted semistructured interviews with 34 people who had received total knee replacement at either of 2 National Health Service hospitals in the UK, and who had chronic postsurgical pain (n = 34, ages 55–93 years). Data were audiorecorded, transcribed, and analyzed thematically.

Results

Two main themes were identified: 1) when describing chronic postsurgical pain, some participants also described sensations of discomfort, including heaviness, numbness, pressure, and tightness associated with the prosthesis; 2) participants reported a lack of felt connection with and agency over their replaced knee, often describing it as alien or other, and lacked confidence in the knee.

Conclusion

Participants’ experiences indicate that some people do not achieve full incorporation of the prosthesis. Our study emphasizes the importance of physicians treating patients as whole people and moving beyond clinical and procedural ideas of success. Our findings suggest that to optimize postoperative outcomes, rehabilitation must focus not only on strengthening the joint and promoting full recovery to tasks but on modifying a person's relationship to the new joint and managing sensations of otherness to achieve full incorporation of the joint or re‐embodiment.

Talking with Your (Artificial) Hands: Communicative Hand Gestures as an Implicit Measure of Embodiment

When people talk, they move their hands to enhance meaning. Using accelerometry, we measured whether people spontaneously use their artificial limbs (prostheses) to gesture, and whether this behavior relates to everyday prosthesis use and perceived embodiment. Perhaps surprisingly, one- and two-handed participants did not differ in the number of gestures they produced in gesture-facilitating tasks. However, they did differ in their gesture profile. One-handers performed more, and bigger, gesture movements with their intact hand relative to their prosthesis. Importantly, one-handers who gestured more similarly to their two-handed counterparts also used their prosthesis more in everyday life. Although collectively one-handers only marginally agreed that their prosthesis feels like a body part, one-handers who reported they embody their prosthesis also showed greater prosthesis use for communication and daily function. Our findings provide the first empirical link between everyday prosthesis use habits and perceived embodiment and a novel means for implicitly indexing embodiment.

Bioinspired Postural Controllers for a Locked-Ankle Exoskeleton Targeting Complete SCI Users

Several lower-limb exoskeletons enable overcoming obstacles that would impair daily activities of wheelchair users, such as going upstairs. Still, as most of the currently commercialized exoskeletons require the use of crutches, they prevent the user from interacting efficiently with the environment. In a previous study, a bio-inspired controller was developed to allow dynamic standing balance for such exoskeletons. It was however only tested on the device without any user. This work describes and evaluates a new controller that extends this previous one with an online model compensation, and the contribution of the hip joint against strong perturbations. In addition, both controllers are tested with the exoskeleton TWIICE One, worn by a complete spinal cord injury pilot. Their performances are compared by the mean of three tasks: standing quietly, resisting external perturbations, and lifting barbells of increasing weight. The new controller exhibits a similar performance for quiet standing, longer recovery time for dynamic perturbations but better ability to sustain prolonged perturbations, and higher weightlifting capability.

Painful metaphors: enactivism and art in qualitative research

Enactivism is an emerging theory for sense-making (cognition) with increasing applications to research and medicine. Enactivists reject the idea that sense-making is simply in the head or can be reduced to neural processes. Instead, enactivists argue that cognisers (people) are embodied and action-oriented, and that sense-making emerges from relational processes distributed across the brain-body-environment. We start this paper with an overview of a recently proposed enactive approach to pain. With rich theoretical and empirical roots in phenomenology and cognitive science, conceptualising pain as an enactive process is appealing as it overcomes the problematic dualist and reductionist nature of current pain theories and healthcare practices. Second, we discuss metaphor in the context of pain and enactivism, including a pain-related metaphor classification system. Third, we present and discuss five paintings created alongside an enactive study of clinical communication and the co-construction of pain-related meanings. Each painting represents pain-related metaphors delivered by clinicians during audio-recorded clinical appointments or discussed by clinicians and patients during interviews. We classify these metaphors, connecting them to enactive theory and relevant literature. The art, metaphors and associated narratives draw attention to the intertwined nature of language, meaning and pain. Of clinical relevance to primary and allied healthcare, we explore how clinicians' taken-for-granted pain-related metaphors can act as scaffolding for patients' pain and agency, for better or worse. We visually depict and give examples of clinical situations where metaphors became enactive, in that they were clinically reinforced and embodied through assessment and treatment. We conclude with research and clinical considerations, suggesting that enactive metaphor is a widely overlooked learning mechanism that clinicians could consider employing and intentionally shape.

Passive Brain-Computer Interfaces for Enhanced Human-Robot Interaction

Brain-computer interfaces (BCIs) have long been seen as control interfaces that translate changes in brain activity, produced either by means of a volitional modulation or in response to an external stimulation. However, recent trends in the BCI and neurofeedback research highlight passive monitoring of a user's brain activity in order to estimate cognitive load, attention level, perceived errors and emotions. Extraction of such higher order information from brain signals is seen as a gateway for facilitation of interaction between humans and intelligent systems. Particularly in the field of robotics, passive BCIs provide a promising channel for prediction of user's cognitive and affective state for development of a user-adaptive interaction. In this paper, we first illustrate the state of the art in passive BCI technology and then provide examples of BCI employment in human-robot interaction (HRI). We finally discuss the prospects and challenges in integration of passive BCIs in socially demanding HRI settings. This work intends to inform HRI community of the opportunities offered by passive BCI systems for enhancement of human-robot interaction while recognizing potential pitfalls.

Differential experiences of embodiment between body-powered and myoelectric prosthesis users

Prosthesis embodiment, the perception of a prosthesis as part of one's body, may be an important component of functional recovery for individuals with upper limb absence. This work determined whether embodiment differs between body-powered and myoelectric prosthesis users. In a sample of nine individuals with transradial limb absence, embodiment was quantified using a survey regarding prosthesis ownership and agency. The extent to which the prosthesis affected the body schema, the representation of the body's dimensions, was assessed using limb length estimation. Because body-powered prostheses offer proprioceptive feedback that myoelectric prostheses do not, it was hypothesized that both measures would reveal stronger embodiment of body-powered prostheses. However, our results did not show differences across the two prosthesis designs. Instead, body schema was influenced by several patient-specific characteristics, including the cause of limb absence (acquired or congenital) and hours of daily prosthesis wear. These results indicate that regular prosthesis wear and embodiment are connected, regardless of the actual prosthesis design. Identifying whether embodiment is a direct consequence of regular prosthesis use would offer insight on how individuals with limb absence could modify their behavior to more fully embody their prosthesis.

The patterning of local variability during the acquisition of a novel whole-body continuous motor skill in young adults

There is increasing evidence that movement variability during motor skill acquisition plays a functional role. Specifically, initial variability might represent exploration of the possible motor space for solutions and error identification. Following practice, individuals might exploit a reduced amount of motor solutions to execute the task. While this variability pattern has been supported during discrete upper limb and multi-finger force tasks, there is a paucity of evidence for continuous whole-body motor tasks. Therefore, the purpose of this study was to characterize the role of variability during the acquisition of a whole-body continuous motor task across practice sessions in young adults. Twelve young adults aged 18-35-years participated in this study. Subjects practiced a novel, sagittal plane task, the kettlebell swing, using an online training video. We conducted an uncontrolled manifold analysis to partition local variability of the configuration of the kettlebell and body segments based on their impact on the position of the center-of-mass (COM) in the sagittal plane. Our results demonstrated that following initial practice, variability that did not affect the COM position remained elevated, suggesting sustained exploration of motor solutions. Following multiple practice sessions, variability related to motor solutions decreased, potentially indicating exploitation. The results from this study support the proposal that young adults initially utilize a range of motor solutions when acquiring a whole-body motor skill, followed by exploitation of stereotypic movement.

Is an artificial limb embodied as a hand? Brain decoding in prosthetic limb users

The potential ability of the human brain to represent an artificial limb as a body part (embodiment) has been inspiring engineers, clinicians, and scientists as a means to optimise human-machine interfaces. Using functional MRI (fMRI), we studied whether neural embodiment actually occurs in prosthesis users' occipitotemporal cortex (OTC). Compared with controls, different prostheses types were visually represented more similarly to each other, relative to hands and tools, indicating the emergence of a dissociated prosthesis categorisation. Greater daily life prosthesis usage correlated positively with greater prosthesis categorisation. Moreover, when comparing prosthesis users' representation of their own prosthesis to controls' representation of a similar looking prosthesis, prosthesis users represented their own prosthesis more dissimilarly to hands, challenging current views of visual prosthesis embodiment. Our results reveal a use-dependent neural correlate for wearable technology adoption, demonstrating adaptive use-related plasticity within the OTC. Because these neural correlates were independent of the prostheses' appearance and control, our findings offer new opportunities for prosthesis design by lifting restrictions imposed by the embodiment theory for artificial limbs.

Acquisition of Ownership Illusion with Self-Disownership in Neurological Patients

The multisensory regions in frontoparietal cortices play a crucial role in the sense of body and self. Disrupting this sense may lead to a feeling of disembodiment, or more generally, a sense of disownership. Experimentally, this altered consciousness disappears during illusory own-body perceptions, increasing the intensity of perceived ownership for an external virtual limb. In many clinical conditions, particularly in individuals with a discontinuous or absent sense of bodily awareness, the brain may effortlessly create a convincing feeling of body ownership over a surrogate body or body part. The immediate visual input dominates the current bodily state and induces rapid plastic adaptation that reconfigures the dynamics of bodily representation, allowing the brain to acquire an alternative sense of body and self. Investigating strategies to deconstruct the lack of a normal sense of bodily ownership, especially after a neurological injury, may aid the selection of appropriate clinical treatment.

Passive Brain-Computer Interfaces for Enhanced Human-Robot Interaction

Brain-computer interfaces (BCIs) have long been seen as control interfaces that translate changes in brain activity, produced either by means of a volitional modulation or in response to an external stimulation. However, recent trends in the BCI and neurofeedback research highlight passive monitoring of a user's brain activity in order to estimate cognitive load, attention level, perceived errors and emotions. Extraction of such higher order information from brain signals is seen as a gateway for facilitation of interaction between humans and intelligent systems. Particularly in the field of robotics, passive BCIs provide a promising channel for prediction of user's cognitive and affective state for development of a user-adaptive interaction. In this paper, we first illustrate the state of the art in passive BCI technology and then provide examples of BCI employment in human-robot interaction (HRI). We finally discuss the prospects and challenges in integration of passive BCIs in socially demanding HRI settings. This work intends to inform HRI community of the opportunities offered by passive BCI systems for enhancement of human-robot interaction while recognizing potential pitfalls.

Exoskeleton and End-Effector Robots for Upper and Lower Limbs Rehabilitation: Narrative Review

Recovery of upper and lower limbs function is essential to reach independence in daily activities in patients with upper motor neuron syndrome (UMNS). Rehabilitation can provide a guide for motor recovery influencing the neurobiology of neuronal plasticity providing controlled, repetitive, and variable patterns. Increasing therapy dosage, intensity, number of repetition, execution of task-oriented exercises, and combining top-down and bottom-up approaches can promote plasticity and functional recovery. Robotic exoskeletons for upper and lower limbs, based on the principle of motor learning, have been introduced in neurorehabilitation. In this narrative review, we provide an overview of literature published on exoskeleton devices for upper and lower limb rehabilitation in patients with UMNS; we summarized the available current research evidence and outlined the new challenges that neurorehabilitation and bioengineering will have to face in the upcoming years. Robotic treatment should be considered a rehabilitation tool useful to generate a more complex, controlled multisensory stimulation of the patient and useful to modify the plasticity of neural connections through the experience of movement. Efficacy and efficiency of robotic treatment should be defined starting from intensity, complexity, and specificity of the robotic exercise, that are related to human-robot interaction in terms of motion, emotion, motivation, meaning of the task, feedback from the exoskeleton, and fine motion assistance. Duration of a single session, global period of the treatment, and the timing for beginning of robotic treatment are still open questions. There is the need to evaluate and individualize the treatment according to patient's characteristics. Robotic devices for upper and lower limbs open a window to define therapeutic modalities as possible beneficial drug, able to boost biological, neurobiological, and epigenetic changes in central nervous system. We need to implement large and innovative research programs to answer these issues in the near future.

Sense of ownership and not the sense of agency is spatially bounded within the space reachable with the unaugmented hand

While reaching for a coffee cup, we are aware that the hand we see belongs to us and it moves at our will (reflecting our senses of ownership and agency, respectively), and that the cup is within our hand's reach rather than beyond it (i.e., in reachable space, RS, rather than in non-reachable space, NRS). Accepted psychological explanations of our sense of ownership, sense of agency, and our perception of space surrounding the body as RS or NRS propose a unitary dependence on Euclidean distance from the body. Here, we propose an alternate, affordance-based explanation of experienced ownership, agency, and perception of space surrounding the body as RS and NRS. Adult participants experienced the static rubber hand illusion (RHI) and its dynamic variant, while the rubber hand was either within their arm's reach (i.e., in self-identified RS) or beyond it (i.e., in self-identified NRS). We found that when the participants experienced synchronous visual and tactile signals in the static RHI, and synchronous visual and kinesthetic signals in the dynamic RHI, they felt illusory ownership when the rubber hand was in RS but not when it was in NRS. Conversely, when the participants experienced synchronous visual and kinesthetic signals in the dynamic RHI, they felt agency, regardless of the rubber hand's location. In addition, illusory ownership was accompanied by proprioceptive drift, a feeling that their hand was closer to the rubber hand than it actually was, but agency was not accompanied by proprioceptive drift. Together, these results indicate that our sense of ownership, while malleable enough to incorporate visible non-corporeal objects resembling a body part, is spatially constrained by proprioceptive signals specifying that body part's actual location. In contrast, our sense of agency can incorporate a visible non-corporeal object, independent of its location with respect to the body. We propose that the psychological processes mediating our sense of ownership are closely linked with our perception of space surrounding the body, and that the spatial independence of our sense of agency reflects the coupling between our actions and perception of the environment, such as while using handheld tools as extensions of our body.

Identification of clinically related requirements of a novel assistive device for people with a high spinal cord injury

People with spinal cord injuries (SCI), and particularly with high level lesions, can potentially lose the ability to effectively operate computers. The Multimedia Authoring and Management using your Eyes and Mind (MAMEM) project aims to design and produce a novel assistive device to support computer use by individuals with SCI and other disabilities. The solution harnesses eye tracking and brain waves, as measured by encephalography (EEG), to manipulate common computer functions. This paper describes the first step in the project, during which we defined clinically related requirements of the assistive device. These definitions were based on data from three sources: (1) a narrative review; (2) a focus group of SCI rehabilitation professionals; and (3) structured questionnaires administrated to potential computer users with SCI, addressing computer-use habits, barriers, and needs. We describe both the collection of data from each source and the clinically related requirements extracted. The novel three-source requirement assessment method is discussed, and the advantages and disadvantages of each data source are reported. In conclusion, we suggest that this approach makes it possible to organize, discuss, and prioritize the requirements, and to create a work program while planning the device. This increases our level of certainty that the efficacy and adequacy of the assistive device will be maximized, in terms of the clinical needs of users.

Who Will Be the Members of Society 5.0? Towards an Anthropology of Technologically Posthumanized Future Societies

The Government of Japan’s “Society 5.0” initiative aims to create a cyber-physical society in which (among other things) citizens’ daily lives will be enhanced through increasingly close collaboration with artificially intelligent systems. However, an apparent paradox lies at the heart of efforts to create a more “human-centered” society in which human beings will live alongside a proliferating array of increasingly autonomous social robots and embodied AI. This study seeks to investigate the presumed human-centeredness of Society 5.0 by comparing its makeup with that of earlier societies. By distinguishing “technological” and “non-technological” processes of posthumanization and applying a phenomenological anthropological model, this study demonstrates: (1) how the diverse types of human and non-human members expected to participate in Society 5.0 differ qualitatively from one another; (2) how the dynamics that will shape the membership of Society 5.0 can be conceptualized; and (3) how the anticipated membership of Society 5.0 differs from that of Societies 1.0 through 4.0. This study describes six categories of prospective human and non-human members of Society 5.0 and shows that all six have analogues in earlier societies, which suggests that social scientific analysis of past societies may shed unexpected light on the nature of Society 5.0.

How Cognitive Models of Human Body Experience Might Push Robotics

In the last decades, cognitive models of multisensory integration in human beings have been developed and applied to model human body experience. Recent research indicates that Bayesian and connectionist models might push developments in various branches of robotics: assistive robotic devices might adapt to their human users aiming at increased device embodiment, e.g., in prosthetics, and humanoid robots could be endowed with human-like capabilities regarding their surrounding space, e.g., by keeping safe or socially appropriate distances to other agents. In this perspective paper, we review cognitive models that aim to approximate the process of human sensorimotor behavior generation, discuss their challenges and potentials in robotics, and give an overview of existing approaches. While model accuracy is still subject to improvement, human-inspired cognitive models support the understanding of how the modulating factors of human body experience are blended. Implementing the resulting insights in adaptive and learning control algorithms could help to taylor assistive devices to their user's individual body experience. Humanoid robots who develop their own body schema could consider this body knowledge in control and learn to optimize their physical interaction with humans and their environment. Cognitive body experience models should be improved in accuracy and online capabilities to achieve these ambitious goals, which would foster human-centered directions in various fields of robotics.

Detection of movement onset using EMG signals for upper-limb exoskeletons in reaching tasks

BACKGROUND

To assist people with disabilities, exoskeletons must be provided with human-robot interfaces and smart algorithms capable to identify the user's movement intentions. Surface electromyographic (sEMG) signals could be suitable for this purpose, but their applicability in shared control schemes for real-time operation of assistive devices in daily-life activities is limited due to high inter-subject variability, which requires custom calibrations and training. Here, we developed a machine-learning-based algorithm for detecting the user's motion intention based on electromyographic signals, and discussed its applicability for controlling an upper-limb exoskeleton for people with severe arm disabilities.

METHODS

Ten healthy participants, sitting in front of a screen while wearing the exoskeleton, were asked to perform several reaching movements toward three LEDs, presented in a random order. EMG signals from seven upper-limb muscles were recorded. Data were analyzed offline and used to develop an algorithm that identifies the onset of the movement across two different events: moving from a resting position toward the LED (Go-forward), and going back to resting position (Go-backward). A set of subject-independent time-domain EMG features was selected according to information theory and their probability distributions corresponding to rest and movement phases were modeled by means of a two-component Gaussian Mixture Model (GMM). The detection of movement onset by two types of detectors was tested: the first type based on features extracted from single muscles, whereas the second from multiple muscles. Their performances in terms of sensitivity, specificity and latency were assessed for the two events with a leave one-subject out test method.

RESULTS

The onset of movement was detected with a maximum sensitivity of 89.3% for Go-forward and 60.9% for Go-backward events. Best performances in terms of specificity were 96.2 and 94.3% respectively. For both events the algorithm was able to detect the onset before the actual movement, while computational load was compatible with real-time applications.

CONCLUSIONS

The detection performances and the low computational load make the proposed algorithm promising for the control of upper-limb exoskeletons in real-time applications. Fast initial calibration makes it also suitable for helping people with severe arm disabilities in performing assisted functional tasks.

The Overlooked Outcome Measure for Spinal Cord Injury: Use of Assistive Devices

Although several outcome measures are used to assess various areas of interest regarding spinal cord injuries (SCIs), little is known about the frequency of their use, and the ways in which they transform shared knowledge into implemented practices. Herein, 800 professionals from the International Spinal Cord Society, especially trained for caring in patients with SCI, were invited to respond to an Internet survey collecting information on the use of standardized measures in daily clinical practices. We asked both clinicians and researchers with different areas of interest about their use of functional outcome measures, and, in particular, which scales they habitually use to assess various aspects of clinical practice and rehabilitation. We selected a set of rating scales, which were validated for measuring SCIs (http://www.scireproject.com/outcome-measures). The results show that the areas of interest assessed by most of the participants were neurological status, upper limb, lower limb gait, pain, spasticity, self-care, and daily living. The most widely used rating scales were the spinal cord independence measure, the functional independence measure and the International Standards for Neurological Classification of Spinal Cord Injury. Instead, the majority of respondents did not evaluate the use of assistive technology. Despite the availability of several outcome scales, the practice of evaluating SCIs with standardized measures for assistive technologies and wheelchair mobility is still not widespread, even though it is a high priority in the rehabilitation of SCI patients. The results emphasize the need for a more thorough knowledge and use of outcome scales, thus improving the quality of assistive device evaluation.

On Replacement Body Parts

Technological advances are making devices that functionally replace body parts-artificial organs and limbs-more widely used, and more capable of providing patients with lives that are close to "normal." Some of the ethical issues this is likely to raise relate to how such prostheses are conceptualized. Prostheses are ambiguous between being inanimate objects and sharing in the status of human bodies-which already have an ambiguous status, as both objects and subjects. At the same time, the possibility of replacing body parts with artificial objects puts pressure on the normative status typically accorded to human bodies, seemingly confirming that body parts are replaceable objects. The paper argues that bodies' normative status relies on the relation of a body to a person and shows that persons could have similar relations to prostheses. This suggests that in approaching ethical issues surrounding prostheses, it is appropriate to regard them as more like body parts than like objects.

Physiological and kinematic effects of a soft exosuit on arm movements

BACKGROUND

Soft wearable robots (exosuits), being lightweight, ergonomic and low power-demanding, are attractive for a variety of applications, ranging from strength augmentation in industrial scenarios, to medical assistance for people with motor impairments. Understanding how these devices affect the physiology and mechanics of human movements is fundamental for quantifying their benefits and drawbacks, assessing their suitability for different applications and guiding a continuous design refinement.

METHODS

We present a novel wearable exosuit for assistance/augmentation of the elbow and introduce a controller that compensates for gravitational forces acting on the limb while allowing the suit to cooperatively move with its wearer. Eight healthy subjects wore the exosuit and performed elbow movements in two conditions: with assistance from the device (powered) and without assistance (unpowered). The test included a dynamic task, to evaluate the impact of the assistance on the kinematics and dynamics of human movement, and an isometric task, to assess its influence on the onset of muscular fatigue.

RESULTS

Powered movements showed a low but significant degradation in accuracy and smoothness when compared to the unpowered ones. The degradation in kinematics was accompanied by an average reduction of 59.20±5.58% (mean ± standard error) of the biological torque and 64.8±7.66% drop in muscular effort when the exosuit assisted its wearer. Furthermore, an analysis of the electromyographic signals of the biceps brachii during the isometric task revealed that the exosuit delays the onset of muscular fatigue.

CONCLUSIONS

The study examined the effects of an exosuit on the characteristics of human movements. The suit supports most of the power needed to move and reduces the effort that the subject needs to exert to counteract gravity in a static posture, delaying the onset of muscular fatigue. We interpret the decline in kinematic performance as a technical limitation of the current device. This work suggests that a powered exosuit can be a good candidate for industrial and clinical applications, where task efficiency and hardware transparency are paramount.

Feel-Good Robotics: Requirements on Touch for Embodiment in Assistive Robotics

The feeling of embodiment, i.e., experiencing the body as belonging to oneself and being able to integrate objects into one's bodily self-representation, is a key aspect of human self-consciousness and has been shown to importantly shape human cognition. An extension of such feelings toward robots has been argued as being crucial for assistive technologies aiming at restoring, extending, or simulating sensorimotor functions. Empirical and theoretical work illustrates the importance of sensory feedback for the feeling of embodiment and also immersion; we focus on the the perceptual level of touch and the role of tactile feedback in various assistive robotic devices. We critically review how different facets of tactile perception in humans, i.e., affective, social, and self-touch, might influence embodiment. This is particularly important as current assistive robotic devices – such as prostheses, orthoses, exoskeletons, and devices for teleoperation–often limit touch low-density and spatially constrained haptic feedback, i.e., the mere touch sensation linked to an action. Here, we analyze, discuss, and propose how and to what degree tactile feedback might increase the embodiment of certain robotic devices, e.g., prostheses, and the feeling of immersion in human-robot interaction, e.g., in teleoperation. Based on recent findings from cognitive psychology on interactive processes between touch and embodiment, we discuss technical solutions for specific applications, which might be used to enhance embodiment, and facilitate the study of how embodiment might alter human-robot interactions. We postulate that high-density and large surface sensing and stimulation are required to foster embodiment of such assistive devices.

Embodying functionally relevant action sounds in patients with spinal cord injury

Growing evidence indicates that perceptual-motor codes may be associated with and influenced by actual bodily states. Following a spinal cord injury (SCI), for example, individuals exhibit reduced visual sensitivity to biological motion. However, a dearth of direct evidence exists about whether profound alterations in sensorimotor traffic between the body and brain influence audio-motor representations. We tested 20 wheelchair-bound individuals with lower skeletal-level SCI who were unable to feel and move their lower limbs, but have retained upper limb function. In a two-choice, matching-to-sample auditory discrimination task, the participants were asked to determine which of two action sounds matched a sample action sound presented previously. We tested aural discrimination ability using sounds that arose from wheelchair, upper limb, lower limb, and animal actions. Our results indicate that an inability to move the lower limbs did not lead to impairment in the discrimination of lower limb-related action sounds in SCI patients. Importantly, patients with SCI discriminated wheelchair sounds more quickly than individuals with comparable auditory experience (i.e. physical therapists) and inexperienced, able-bodied subjects. Audio-motor associations appear to be modified and enhanced to incorporate external salient tools that now represent extensions of their body schemas.