Virtual Limb Research Articles

Myoelectric motor execution and sensory training to treat chronic pain and paralysis in a replanted arm: a case study

BackgroundFollowing upper limb amputation, surgeries such as arm transplantation or replantation might be an option to restore function. After such surgeries, rehabilitation of the arm is needed. However, conventional rehabilitation is dependent on some volitional movement of the arm. If there is no or minimal movement of the arm, conventional rehabilitation might not be successful. The purpose of this study is to evaluate a novel combination of myoelectric motor execution (MME) and sensory training (ST) to reduce pain and improve upper limb function in a person with a highly impaired replanted arm.MethodsThe participant, a 72-year-old male, had his right arm replanted after a traumatic accident. No functional recovery was achieved following conventional rehabilitation and chronic neuropathic pain developed post-surgery. The participant then received 18 sessions of MME in which intended movements were decoded from the replanted arm’s myoelectric signals using machine learning and real-time feedback was provided on a screen. Nine sessions included ST using tactile grids where the participant discriminated different sensations.ResultsThe participant regained active extension of the thumb (4 degrees) and regained active wrist movement (flex: 6 degrees, extend: 10 degrees), both of which had no active movement prior the MME interventions. He also perceived an increase in sensation in the thumb and fingers. Pain levels fluctuated throughout the study and no consistent change could be concluded.ConclusionMME is a novel virtual rehabilitation treatment which provides feedback using virtual limbs and serious games. MME combined with ST is a potential rehabilitation treatment for individuals with highly impaired arms and hands which might ameliorate chronic neuropathic pain.

Can the left hand benefit from being right? The influence of body side on perceived grasping ability

AbstractRight-handed individuals (RHIs) demonstrate perceptual biases towards their right hand, estimating it to be larger and longer than their left. In addition, RHIs estimate that they can grasp larger objects with their right hand than their left. This study investigated whether visual information specifying handedness enhances biases in RHIs’ perceptions of their action capabilities. Twenty-two participants were placed in an immersive virtual environment in which self-animated, virtual hands were either presented congruently to their physical hand or mirrored. Following a calibration task, participants estimated their maximum grasp size by adjusting the size of a virtual block until it reached the largest size they thought they could grasp. The results showed that, consistent with research outside of virtual reality, RHIs gave larger estimates of maximum grasp when using their right physical hand than their left. However, this difference remained regardless of how the hand was virtually presented. This finding suggests that proprioceptive feedback may be more important than visual feedback when estimating maximum grasp. In addition, visual feedback on handedness does not appear to enhance biases in perceptions of maximum grasp with the right hand. Considerations for further research into the embodiment of mirrored virtual limbs are discussed.

Motor learning in multijoint virtual arm movements with novel kinematics

Humans move their hands toward precise positions, a skill supported by the coordination of multiple joint movements, even in the presence of inherent redundancy. However, it remains unclear how the central nervous system learns the relationship between redundant joint movements and hand positions when starting from scratch. To address this question, a virtual-arm reaching task was performed in which participants were required to move a cursor corresponding to the hand of a virtual arm to a target. The joint angles of the virtual arm were determined by the heights of the participants’ fingers. The results demonstrated that the participants moved the cursor to the target straighter and faster in the late phase than they did in the initial phase of learning. This improvement was accompanied by a reduction in the amount of angular changes in the virtual limb joint, predominantly characterized by an increased reliance on the virtual shoulder joint as opposed to the virtual wrist joint. These findings suggest that the central nervous system selects a combination of multijoint movements that minimize motor effort while learning novel upper-limb kinematics.

Temporal visuomotor synchrony induces embodiment towards an avatar with biomechanically impossible arm movements

Visuomotor synchrony in time and space induces a sense of embodiment towards virtual bodies experienced in first-person view using Virtual Reality (VR). Here, we investigated whether temporal visuomotor synchrony affects avatar embodiment even when the movements of the virtual arms are spatially altered from those of the user in a non-human-like manner. In a within-subjects design VR experiment, participants performed a reaching task controlling an avatar whose lower arms bent in inversed and biomechanically impossible directions from the elbow joints. They performed the reaching task using this “unnatural avatar” as well as a “natural avatar,” whose arm movements and positions spatially matched the user. The reaching tasks were performed with and without a one second delay between the real and virtual movements. While the senses of body ownership and agency towards the unnatural avatar were significantly lower compared to those towards the natural avatar, temporal visuomotor synchrony did significantly increase the sense of embodiment towards the unnatural avatar as well as the natural avatar. These results suggest that temporal visuomotor synchrony is crucial for inducing embodiment even when the spatial match between the real and virtual limbs is disrupted with movements outside the pre-existing cognitive representations of the human body.

From monkeys to humans: observation-basedEMGbrain-computer interface decoders for humans with paralysis.

Objective. Intracortical brain-computer interfaces (iBCIs) aim to enable individuals with paralysis to control the movement of virtual limbs and robotic arms. Because patients' paralysis prevents training a direct neural activity to limb movement decoder, most iBCIs rely on 'observation-based' decoding in which the patient watches a moving cursor while mentally envisioning making the movement. However, this reliance on observed target motion for decoder development precludes its application to the prediction of unobservable motor output like muscle activity. Here, we ask whether recordings of muscle activity from a surrogate individual performing the same movement as the iBCI patient can be used as target for an iBCI decoder.Approach. We test two possible approaches, each using data from a human iBCI user and a monkey, both performing similar motor actions. In one approach, we trained a decoder to predict the electromyographic (EMG) activity of a monkey from neural signals recorded from a human. We then contrast this to a second approach, based on the hypothesis that the low-dimensional 'latent' neural representations of motor behavior, known to be preserved across time for a given behavior, might also be preserved across individuals. We 'transferred' an EMG decoder trained solely on monkey data to the human iBCI user after using Canonical Correlation Analysis to align the human latent signals to those of the monkey.Main results. We found that both direct and transfer decoding approaches allowed accurate EMG predictions between two monkeys and from a monkey to a human.Significance. Our findings suggest that these latent representations of behavior are consistent across animals and even primate species. These methods are an important initial step in the development of iBCI decoders that generate EMG predictions that could serve as signals for a biomimetic decoder controlling motion and impedance of a prosthetic arm, or even muscle force directly through functional electrical stimulation.

The effects of temperature on elastic energy storage and release in a system with a dynamic mechanical advantage latch.

Changes in temperature alter muscle kinetics and in turn affect whole-organism performance. Some organisms use the elastic recoil of biological springs, structures which are far less temperature sensitive, to power thermally robust movements. For jumping frogs, the use of elastic energy in tendons is facilitated through a geometric latching mechanism that operates through dynamic changes in the mechanical advantage (MA) of the hindlimb. Despite the well-documented use of elastic energy storage, frog jumping is a locomotor behavior that is significantly affected by changes in temperature. Here, we used an in vitro muscle preparation interacting in real time with an in silico model of a legged jumper to understand how changes in temperature affect the flow of energy in a system using a MA latch. We used the plantaris longus muscle-tendon unit (MTU) to power a virtual limb with changing MA and a mass being accelerated through a real-time feedback controller. We quantified the amount of energy stored in and recovered from elastic structures and the additional contribution of direct muscle work after unlatching. We found that temperature altered the duration of the energy loading and recovery phase of the in vitro/in silico experiments. We found that the early phase of loading was insensitive to changes in temperature. However, an increase in temperature did increase the rate of force development, which in turn allowed for increased energy storage in the second phase of loading. We also found that the contribution of direct muscle work after unlatching was substantial and increased significantly with temperature. Our results show that the thermal robustness achieved by an elastic mechanism depends strongly on the nature of the latch that mediates energy flow, and that the relative contribution of elastic and direct muscle energy likely shapes the thermal sensitivity of locomotor systems.

Enhancing Diabetes Care And Preventing Foot Ulcers In Indigenous Communities: Two Examples Of A Holistic Approach In The Province of Quebec

This is a review of a session at the virtual Limb Preservation Symposia that recognizes a dual initiative undertaken to address diabetes management and prevent diabetic foot ulcers within Indigenous communities in the Province of Quebec (Canada). It highlights two intertwined projects: "Culturally Adapted Diabetes Management and Interprofessional Care" and "Preventing Diabetic Foot Ulcers: A Pilot Project." Both initiatives underscore the importance of culturally adapted care, patient engagement, and collaborative approaches in addressing diabetes management and preventing diabetic foot ulcers within Indigenous communities.

CrowbarLimbs: A Fatigue-Reducing Virtual Reality Text Entry Metaphor.

Text entry remains challenging in virtual environments, where users may quickly experience physical fatigue in some body parts using existing methods. In this paper, we propose "CrowbarLimbs," a novel virtual reality (VR) text entry metaphor with two deformable extended virtual limbs. By using a crowbar-like metaphor and placing the virtual keyboard at a user-preferred location based on the user's physical stature, our method can assist the user in placing their hands and arms in a comfortable posture, thus effectively reducing the physical fatigue in various body parts, such as hands, wrists, and elbows. In an initial user study, we found that CrowbarLimbs achieved text entry speed, accuracy, and system usability comparable to those of previous VR typing methods. To investigate the proposed metaphor in more depth, we further conducted two additional user studies to explore the ergonomically user-friendly shapes of CrowbarLimbs and virtual keyboard locations. The experimental results indicate that the shapes of CrowbarLimbs have significant effects on the fatigue ratings in various body parts and text entry speed. Furthermore, placing the virtual keyboard near the user and at half their height can lead to a satisfactory text entry rate of 28.37 words per minute.

102. Novel Methodology for Systematic Sensory Characterization and Stimulus Testing After Major Limb Loss

Purpose: Sensory referral is commonly experienced by patients after amputation, in which touches to the residual limb are perceived as originating from the phantom limb. This phenomenon offers a compelling interface for noninvasive delivery of sensory feedback in prosthetic limbs. However, a more comprehensive understanding of the complexities of the sensory experience is necessary, especially with the rising popularity of surgical techniques such as targeted muscle reinnervation (TMR) and regenerative peripheral nerve interfaces (RPNI). We hypothesize that in TMR and RPNI, repurposing and providing transected nerves with muscle targets for reinnervation may alter or induce patterns of referred sensation. Methods: To study this, we have developed a novel methodology for detailed sensory characterization of the residual limb, compatible for both upper and lower extremity amputation. We designed a computer program for mapping sensory referral, in which participants interact with a virtual representation of their phantom limb. With a touchscreen laptop, participants can zoom and rotate to see the entire limb. Light touch, deep pressure, and vibratory stimuli are presented to the residual limb, and participants tap on the virtual limb to mark the location of the perceived sensation. Results: Our software interface is intuitive for participants to use and is designed to provide a standardized testing methodology, such that any researcher may quickly and confidently perform rigorous, repeatable sensory characterization of a limb. It also minimizes experimenter bias by eliminating ambiguity in verbal responses; participants tap directly on the virtual limb where the feeling appears to originate without needing to verbally describe that anatomical location. The data points on the virtual limb can then be correlated with the tested points on the residual limb to generate a map of referred sensation. Conclusion: Providing an egocentric virtual body for sensory testing enables participants to indicate with high accuracy where a stimulus is perceived on their phantom limb. With our innovative tool, we can screen for individuals with sensory referral and generate complete sensory referral mappings of the residual limb. Aspects of sensory capabilities can be compared across individuals and groups, including surface area of referring skin and rate of referral to peripheral nerve distributions or phantom limb anatomy. Our systematic methodology will facilitate unbiased explorations of sensory referral after amputation, especially after TMR and RPNI surgery.

Feeling of Ownership over an Embodied Avatar's Hand Brings About Fast Changes of Fronto-Parietal Cortical Dynamics.

When we look at our body parts, we are immediately aware that they belong to us and we rarely doubt about the integrity, continuity, and sense of ownership of our body. Despite this certainty, immersive virtual reality (IVR) may lead to a strong feeling of embodiment over an artificial body part seen from a first-person perspective (1PP). Although such feeling of ownership (FO) has been described in different situations, it is not yet understood how this phenomenon is generated at neural level. To track the real-time brain dynamics associated with FO, we delivered transcranial magnetic stimuli over the hand region in the primary motor cortex (M1) and simultaneously recorded electroencephalography (EEG) in 19 healthy volunteers (11 male/8 female) watching IVR renderings of anatomically plausible (full-limb) versus implausible (hand disconnected from the forearm) virtual limbs. Our data show that embodying a virtual hand is temporally associated with a rapid drop of cortical activity of the onlookers' hand region in the M1 contralateral to the observed hand. Spatiotemporal analysis shows that embodying the avatar's hand is also associated with fast changes of activity within an interconnected fronto-parietal circuit ipsilateral to the brain stimulation. Specifically, an immediate reduction of connectivity with the premotor area is paralleled by an enhancement in the connectivity with the posterior parietal cortex (PPC) which is related to the strength of ownership illusion ratings and thus likely reflects conscious feelings of embodiment. Our results suggest that changes of bodily representations are underpinned by a dynamic cross talk within a highly-plastic, fronto-parietal network.SIGNIFICANCE STATEMENT Observing an avatar's body part from a first-person perspective (1PP) induces an illusory embodiment over it. What remains unknown are the cortical dynamics underpinning the embodiment of artificial agents. To shed light on the physiological mechanisms of embodiment we used a novel approach that combines noninvasive stimulation of the cortical motor-hand area and whole-scalp electroencephalographic (EEG) recordings in people observing an embodied artificial limb. We found that just before the illusion started, there is a decrease of activity of the motor-hand area accompanied by an increase of connectivity with the parietal region ipsilateral to the stimulation that reflects the ratings of the embodiment illusion. Our results suggest that changes of bodily representations are underpinned by a dynamic cross talk within a fronto-parietal circuit.

Quantitative and Qualitative Exploration of the Effect of a Wearable Item on Non-Organic Virtual Limb Embodiment and User Behavior in Immersive Environments

Abstract This experiment was designed to investigate the potential contribution to the sense of embodiment of a wristband worn by the participants in both real and virtual environments. In addition, two virtual limb models were compared following a mixed between-within subjects design: an organic hand and a non-organic prosthesis matching the proposed task. Quantitative results revealed no significant effect of the wristband, while post-experiment semistructured interviews revealed that the wristband fostered the identification with the virtual limbs for several participants, but that it might be conditioned by interindividual differences. Ownership scores were significantly higher with the virtual hand. However, participants experienced a very high sense of agency with both conditions despite the lack of finger tracking when controlling the prosthesis. Agency was positively correlated with participants' perceived change in their body schema when embodying the prosthesis. Subjective and objective measures demonstrated that participants were less hesitant and that more collisions were recorded at higher speeds against potentially threatening objects with the non-organic prosthesis.

Comparison of Myoelectric Control Schemes for Simultaneous Hand and Wrist Movement using Chronically Implanted Electromyography: A Case Series.

A current biomedical engineering challenge is the development of a system that allows fluid control of multi-functional prosthetic devices through a human-machine interface. Here we probe this challenge by studying two subjects with trans-radial limb loss as they control a virtual hand and wrist system using 6 or 8 chronically implanted intramuscular electromyographic (iEMG) signals. The subjects successfully controlled a 4, 5, and 6 Degrees of Freedom (DoF's) virtual hand and wrist systems to perform a target matching task. Two control systems were evaluated where one tied EMG features directly to movement directions (Direct Control) and the other method determines user intent in the context of prior training data (Linear Interpolation). Subjects successfully matched most targets with both controllers but differences were seen as the complexity of the virtual limb system increased. The Direct Control method encountered difficulty due to crosstalk at higher DoF's. The Linear Interpolation method reduced crosstalk effects and outperformed Direct Control at higher DoF's. This work also studied the use of the Postural Control Algorithm to control the hand postures simultaneously with wrist degrees of freedom. This work presents preliminary evidence that the PC algorithm can be used in conjunction with wrist control, that Direct Control with iEMG signals allows stable 4-DoF control, and that EMG pre-processing using the Linear Interpolation method can improve performance at 5 and 6-DoF's.

Embodiment and Performance in the Supernumerary Hand Illusion in Augmented Reality

In teleoperations, robots are generally used because related tasks are too dangerous, uncomfortable or impossible for humans to perform. When using augmented reality to control robotic limbs in such teleoperations, it is essential to understand how these extra virtual limbs are experienced. In particular, the relationship between the embodiment experience of the user and relevant outcomes such as task performance must be examined. In this article, we study the relationship between experienced embodiment of a supernumerary virtual arm that acts alongside a user’s two real arms, and their task performance in augmented reality. Specifically, we compare how well users can trace a virtual half ring placed just outside of personal space using their virtual arm in a condition where there is expected to be low embodiment (a floating disconnected hand) and a condition where there is expected to be high embodiment (a connected arm and hand). Embodiment is measured quantitatively through skin conductance response and qualitatively through ownership, agency, and self-location questionnaires. Performance is measured in terms of tracing precision. The results show positive correlations between subjective ownership and agency, and agency and performance, but no correlation between subjective or objective ownership and performance. Also, ownership ratings were low overall, while the agency ratings were significantly higher for the disconnected hand condition than the connected arm condition, as was performance. Notably, the presence of the virtual arm evoked incorrect expectations of the movement capabilities of the arm, which may have contributed to an overall preference for the unrealistic disconnected hand over the more realistic connected arm in this particular task. Our results imply that methods to increase performance in various teleoperations can indeed be found in the experience of embodiment: not necessarily directly through ownership, but through ownership mediated by agency.

Congruency of Information Rather Than Body Ownership Enhances Motor Performance in Highly Embodied Virtual Reality.

In immersive virtual reality, the own body is often visually represented by an avatar. This may induce a feeling of body ownership over the virtual limbs. Importantly, body ownership and the motor system share neural correlates. Yet, evidence on the functionality of this neuroanatomical coupling is still inconclusive. Findings from previous studies may be confounded by the congruent vs. incongruent multisensory stimulation used to modulate body ownership. This study aimed to investigate the effect of body ownership and congruency of information on motor performance in immersive virtual reality. We aimed to modulate body ownership by providing congruent vs. incongruent visuo-tactile stimulation (i.e., participants felt a brush stroking their real fingers while seeing a virtual brush stroking the same vs. different virtual fingers). To control for congruency effects, unimodal stimulation conditions (i.e., only visual or tactile) with hypothesized low body ownership were included. Fifty healthy participants performed a decision-making (pressing a button as fast as possible) and a motor task (following a defined path). Body ownership was assessed subjectively with established questionnaires and objectively with galvanic skin response (GSR) when exposed to a virtual threat. Our results suggest that congruency of information may decrease reaction times and completion time of motor tasks in immersive virtual reality. Moreover, subjective body ownership is associated with faster reaction times, whereas its benefit on motor task performance needs further investigation. Therefore, it might be beneficial to provide congruent information in immersive virtual environments, especially during the training of motor tasks, e.g., in neurorehabilitation interventions.

Shared Prosthetic Control Based on Multiple Movement Intent Decoders.

A number of movement intent decoders exist in the literature that typically differ in the algorithms used and the nature of the outputs generated. Each approach comes with its own advantages and disadvantages. Combining the estimates of multiple algorithms may have better performance than any of the individual methods. This paper presents and evaluates a shared controller framework for prosthetic limbs based on multiple decoders of volitional movement intent. An algorithm to combine multiple estimates to control the prosthesis is developed in this paper. The capabilities of the approach are validated using a system that combines a Kalman filter-based decoder with a multilayer perceptron classifier-based decoder. The shared controller's performance is validated in online experiments where a virtual limb is controlled in real-time by amputee and intact-arm subjects. During the testing phase subjects controlled a virtual hand in real time to move digits to instructed positions using either a Kalman filter decoder, a multilayer perceptron decoder, or a linear combination of the two. The shared controller results in statistically significant improvements over the component decoders. Specifically, certain degrees of shared control result in increases in the time-in-target metric and decreases in unintended movements. The shared controller of this paper combines the good qualities of component decoders tested in this paper. Herein, combining a Kalman filter decoder with a classifier-based decoder inherits the flexibility of the Kalman filter decoder and the limited unwanted movements from the classifier-based decoder, resulting in a system that may be able to perform the tasks of everyday life more naturally and reliably.

BCI-Based Rehabilitation on the Stroke in Sequela Stage.

Background Stroke is the leading cause of serious and long-term disability worldwide. Survivors may recover some motor functions after rehabilitation therapy. However, many stroke patients missed the best time period for recovery and entered into the sequela stage of chronic stroke. Method Studies have shown that motor imagery- (MI-) based brain-computer interface (BCI) has a positive effect on poststroke rehabilitation. This study used both virtual limbs and functional electrical stimulation (FES) as feedback to provide patients with a closed-loop sensorimotor integration for motor rehabilitation. An MI-based BCI system acquired, analyzed, and classified motor attempts from electroencephalogram (EEG) signals. The FES system would be activated if the BCI detected that the user was imagining wrist dorsiflexion on the instructed side of the body. Sixteen stroke patients in the sequela stage were randomly assigned to a BCI group and a control group. All of them participated in rehabilitation training for four weeks and were assessed by the Fugl-Meyer Assessment (FMA) of motor function. Results The average improvement score of the BCI group was 3.5, which was higher than that of the control group (0.9). The active EEG patterns of the four patients in the BCI group whose FMA scores increased gradually became centralized and shifted to sensorimotor areas and premotor areas throughout the study. Conclusions Study results showed evidence that patients in the BCI group achieved larger functional improvements than those in the control group and that the BCI-FES system is effective in restoring motor function to upper extremities in stroke patients. This study provides a more autonomous approach than traditional treatments used in stroke rehabilitation.

Virtual reality-based treatment for regaining upper extremity function induces cortex grey matter changes in persons with acquired brain injury

BackgroundIndividuals with acquired brain injuries (ABI) are in need of neurorehabilitation and neurorepair. Virtual anatomical interactivity (VAI) presents a digital game-like format in which ABI survivors with upper limb paresis use an unaffected limb to control a standard input device and a commonplace computer mouse to control virtual limb movements and tasks in a virtual world.MethodsIn a prospective cohort study, 35 ambulatory survivors of ABI (25/71% stroke, 10/29% traumatic brain injury) were enrolled. The subjects were divided into three groups: group A received VAI therapy only, group B received VAI and physical/occupational therapy (P/OT), and group C received P/OT only. Motor skills were evaluated by muscle strength (hand key pinch strength, grasp, and three-jaw chuck pinch) and active range of motion (AROM) of the shoulder, elbow, and wrist. Changes were analyzed by ANOVA, ANCOVA, and one-tailed Pearson correlation analysis. MRI data was acquired for group A, and volumetric changes in grey matter were analyzed using voxel-based morphometry (VBM) and correlated with quantified motor skills.ResultsAROM of the shoulder, elbow, and wrist improved in all three groups. VBM revealed grey matter increases in five brain areas: the tail of the hippocampus, the left caudate, the rostral cingulate zone, the depth of the central sulcus, and the visual cortex. A positive correlation between the grey matter volumes in three cortical regions (motor and premotor and supplementary motor areas) and motor test results (power and AROM) was detected.ConclusionsOur findings suggest that the VAI rehabilitation program significantly improved motor function and skills in the affected upper extremities of subjects with acquired brain injuries. Significant increases in grey matter volume in the motor and premotor regions of affected hemisphere and correlations of motor skills and volume in nonaffected brain regions were present, suggesting marked changes in structural brain plasticity.Trial registrationThe trial “Limitations of motor brain activity – use of virtual reality for simulation of therapeutic interventions” has been registered under reference number ISRCTN11757651.

Visual feedback from a virtual body modulates motor illusion induced by tendon vibration.

Frequency-specific tendon vibration (TV) elicits illusory kinesthetic sensations around the vibrated body parts. Studies indicate that vision plays a fundamental role in modulating such illusions. In our current study, we used immersive virtual reality (IVR) to investigate the role of body-related visual feedback in modulating illusory sensation of movement in the left arm. Thirty healthy participants were asked to evaluate the onset of motor illusion and four illusion-related features (vividness, duration, extension andaftereffect), in the presence and absence of real and virtual visual feedback. Additionally, subjective reports of the embodiment illusion (the sense of embodying a virtual surrogate) were collected in virtual conditions. Results showed a progressive decrease in the perception of the motor illusion along a continuum ranging from the absence of visual feedback (maximal illusory perception) to the observation of one's own real arm (minimal illusory perception). Interestingly, the appearance of the virtual limbs affected the movement illusion differently. Specifically, TV evoked a stronger kinesthetic illusion when observing the virtual handdetached from thelimb than during the observation of the virtual full limb and virtual object. This suggests that a closer visual resemblance between the virtual and real limb results in a greater effect on proprioceptive processing. However, no significant correlation was found between the illusion of arm movement and the illusion of embodiment, indicating that the two phenomena may not be directly related. These findings provide new insight into the role of body-related visual feedback in modulating motor illusions.

Embodiment, Presence, and Their Intersections

Subjective experience of human control over remote, artificial, or virtual limbs has traditionally been investigated from two separate angles: presence research originates from teleoperation, aiming to capture to what extent the user feels like actually being in the remote or virtual environment. Embodiment captures to what extent a virtual or artificial limb is perceived as one’s own limb. Unfortunately, the two research fields have not interacted much. This survey intends to provide a coherent overview of the literature at the intersection of these two fields to further that interaction. Two rounds of systematic research in topic-related data bases resulted in 414 related articles, 14 of which satisfy the deliberately strict inclusion criteria: 2 theoretical frameworks that highlighted intersections and 12 experimental studies that evaluated subjective measures for both concepts. Considering the surrounding literature as well, theoretical and experimental potential of embodiment and presence are discussed and suggestions to apply them in teleoperation research are derived. While increased publication activity is observed between 2016 and 2018, potentially caused by affordable virtual reality technologies, various open questions remain. To tackle them, human-in-the-loop experiments and three guiding principles for teleoperation system design (mechanical fidelity, spatial bodily awareness, and self-identification) are suggested.

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.