Rubber hands 'feel' touch that eyes see

Body detachment in response to emotions: Evidence from a rubber hand illusion study in adolescent patients with non-suicidal self-injurious behavior and dissociative symptoms

Previous studies have proposed a connection between dissociation and the sense of body ownership, and initial evidence suggests that emotions could modulate this relationship. Here we aimed to investigate how differently arousing emotions influence the malleability of the bodily self. This study included 50 adolescent psychiatric patients with non-suicidal self-injurious behavior (NSSI)-who were divided into low-dissociation and high-dissociation groups-along with 25 healthy controls. Participants completed six trials of the rubber hand illusion while listening to neutral, sad, or fearful vocalizations. Heart rate, skin conductance level, and non-specific skin conductance responses were concomitantly measured. After each trial, participants completed the rubber hand illusion questionnaire as a subjective illusion measure, and acute dissociation, mood, and proprioceptive drift were assessed. Overall, the NSSI high-dissociation group reported the highest subjective illusion under all conditions. Additionally, fearful vocalizations resulted in a stronger subjective illusion than the neutral condition in the NSSI low-dissociation group, but not in the NSSI high-dissociation and healthy control groups. The NSSI low-dissociation group showed a higher proprioceptive drift than the NSSI high-dissociation group. Moreover, acute dissociation was positively related to subjective illusion, but not related to proprioceptive drift. In conclusion, body detachment in response to emotions may be responsible for the malleability of the sense of body ownership. This finding highlights the need for clinical interventions to stabilize self-experiences during emotional situations, especially in patients with dissociative symptoms.

Can impersonal touch replace interpersonal touch? An investigation using the rubber hand illusion

Our socio-emotional development and well-being critically depends on interpersonal tactile interactions, which are sensed by the skin through C-tactile (CT) afferents that respond to gentle, slow touch at typical skin temperatures. In the present study, we investigated whether impersonal touch would be able to provide similar pleasantness compared to interpersonal touch within a body-ownership illusion paradigm. To provide impersonal touch at similar parameters, we used a thermal probe kept at [Formula: see text]C (typical skin-to-skin temperature) compared to a flat hand as interpersonal touch. Both forms of touch were performed at CT-compatible speeds of 3cm/s by a male trained experimenter within a classic rubber hand illusion (RHI) paradigm in two counter-balanced within-participant conditions. A sample of N=45 healthy participants was tested and pleasantness ratings, touch deprivation, and the Need-For-Touch-Scale (NFT) were gathered. Overall, the illusion was similar in both touch conditions and, importantly, we found no statistically significant difference in pleasantness between interpersonal and impersonal touch. Interestingly, neither NFT scores, nor touch deprivation measures correlated with individual differences in the RHI and affective ratings. Our results suggest that impersonal touch with CT-optimal components provide a pleasantness and subjective illusion experience compared to interpersonal touch under the RHI paradigm.

Do We Still Need Human Instructors? Investigating Automated Methods for Motor Skill Learning in Virtual Co-Embodiment

Virtual reality, which enables users to engage in physical activities in ways distinct from those in the real world, is increasingly recognized for its potential to enhance motor skill acquisition. Research on co-embodiment learning, in which instructors and learners utilize a single avatar that represents a weighted average of their movements, has demonstrated its efficacy in facilitating motor skill development. However, the current implementation of co-embodiment learning necessitates the real-time participation of instructors proficient in both virtual reality and co-embodiment, which poses challenges for its widespread adoption. To address this limitation, this study proposed a method for developing instructors trained on human motor data to effectively support motor skill learning through co-embodiment. The AI model was trained using supervised learning on data obtained from human motor learning sessions that employed co-embodiment. To evaluate the performance of the AI instructor, we compared the learning performance in co-embodiment learning with that of the AI instructor, recorded human instructor data, and a human instructor as well as in solo learning. The results showed that practicing with the AI instructor significantly improved learning efficiency compared with practicing alone or with recorded data and was comparable to that achieved by practicing with a human instructor.

Effects of Proprioceptive Attenuation with Noisy Tendon Electrical Stimulation on Adaptation to Beyond-Real Interaction

Virtual reality (VR) enables beyond-real interactions (BRI) that transcend physical constraints, offering effective user experiences like extending a hand to grasp distant objects. However, adapting to novel mappings of BRI often reduces performance and the sense of embodiment. To address this, we propose using noisy tendon electrical stimulation (n-TES) to decrease proprioceptive precision. Previous studies have suggested that attenuating proprioceptive precision is crucial for sensory-motor adaptations. Thus, we hypothesize that n-TES, which has been shown to reduce proprioceptive precision and induce visual-dependent perception in VR, can enhance user adaptation to BRI. We conducted a user study using go-go interaction, a BRI technique for interacting with distant objects, to assess the effects of n-TES. Given the individual variability in n-TES response, participants first underwent a proprioceptive precision test to determine the optimal stimulation intensity to lower the proprioceptive precision from 5 levels $(\sigma=0.25-125\text{mA})$. Reaching tasks using a 2x2 within-participants design evaluated the effects of go-go interaction and n-TES on performance, subjective task load, and embodiment. Results from 24 participants showed that go-go interaction increased reaching time and task load while decreasing the sense of embodiment. Contrary to our hypothesis, n-TES did not significantly mitigate most of these negative effects of go-go interaction, except that perceived agency was higher with n-TES during go-go interaction. The limited effectiveness of n-TES may be due to participants' habituation or sensory adaptation during the tasks. Future research should consider the adaptation process to BRI and investigate different BRI scenarios.

Maternal Interaction Relates to Neural Processing of Self-Related Multisensory Information in 5-Month-Olds

The ontogenetic origin of the self in infancy is a topic of ongoing debate. Although influential developmental and neurocognitive theories propose that caregiver-infant interactions play an important role in infants' self-development, little is known about the specific mechanisms involved. Some theories highlight the importance of caregiver sensitivity and touch, while others propose that caregiver contingency plays a central role. The study aimed to investigate infants' self-perception by measuring brain activation in the posterior superior temporal sulcus (pSTS), a region previously associated with self-related processing. A total of 118 mother-infant dyads participated in a free-play interaction, during which maternal sensitivity and touch were measured. Additionally, a face-to-face interaction was conducted to measure maternal contingency. Infants' brain activation was measured using functional near-infrared spectroscopy (fNIRS). They watched a video of their own face while being stroked by a brush on the cheek. The video was either live and the stroking was synchronous to the video (contingent) or the video was delayed by 3 s, which made the stroking asynchronous (non-contingent). The results showed that infants exhibited more HbO-activation in the right pSTS in the non-contingent condition. Importantly, the more sensitive the mothers were and the more they touched infants during free play, the less differential activation the infants showed in response to both conditions. This effect was driven by infants showing less activation to the non-contingent condition when their mothers exhibited more care, maybe because of a smaller prediction error for non-contingent self-related multisensory information. Overall, the study deepens our knowledge of how early social interactions relate to the emergence of the self in infancy.

Investigating the role of weight in body representation through the Rubber Hand Illusion: when individual weight concerns matter

Bodily weight is a physical characteristic involved in body dissatisfaction. We investigated whether the cognitive body representation can be updated to include weight variations using the Rubber Hand Illusion. Moreover, we aimed to explore the role of the individual expression of weight concerns and fat-phobia. Twenty-eight healthy-weight women participated to a Rubber Hand Illusion study, in which an over- and an under-weight rubber hand were tested together with a normal-weigh rubber hand. We verified the effect of hand's weight on the proprioceptive drift and the subjective experience of illusion. Moreover, we measured the individual expression of weight concerns. As with the normal-weight rubber hand, both the underweight and overweight ones produced significant rubber hand illusion effects, as quantified by proprioceptive judgments and questionnaire ratings. Moreover, higher levels of body image concerns were linked to higher shift towards the under-weight rubber hand, as well as higher expression of fat-phobia increased higher illusory subjective experience towards the normal-weight hand. Hands of different weights can be successfully embodied, in line with previous evidence relative to whole body illusions. Nevertheless, we underlined the role of weight concerns in modulating the illusion. Our results are meaningful for those psychopathological conditions characterized by profound changes in individual weight.

Virtual body continuity during action observation affects motor cortical excitability

Body ownership, the sense that the body belongs to oneself, can be altered by inducing body manipulations in Virtual Reality, such as by increasing the visual discontinuity between the avatar's hand and body. Body representation manipulations can also influence motor cortex excitability. We hypothesized that the degree of body continuity between one's body and the observed virtual body would affect ownership feelings and impact motor cortex excitability during action observation. Participants observed virtual hand movements from a first-person perspective with the virtual hand presented with different level of connection with their real hand; the virtual hand could be part of a full virtual body co-located with the real body (Full-Body condition), it could appear as connected to an upper limb visually discontinuous from the real body (Upper Limb condition), or the virtual hand appeared in isolation, fully discontinuous (Detached Hand condition). Results showed increased corticospinal excitability when body continuity is higher (Full-Body and Upper Limb). This effect was mediated by ownership and disownership feelings, supporting the relationship between body perception and motor system.

Trait dissociation is associated with dissociative experiences arising from disrupted multisensory integration

Dissociation is a transdiagnostic mental health symptom involving a sense of detachment from one's own body. A coherent percept of our body relies upon the smooth integration of different senses, such as vision and touch, which are processed by the brain at different speeds. We investigated the association between multi-sensory integration and dissociation in a N = 100 non-clinical sample. An immersive head-mounted display provided participants with a first-person view of their body while their arm was brushed by themselves or by the researcher. This mixed-reality setup allowed for the systematic variation of a delay to the visual feed, resulting in visual information being delayed relative to other senses (e.g. touch). Larger delays were associated with greater self-reported feelings of dis-ownership from the body. In addition, participants with high trait dissociation felt elevated sensations of dis-ownership from the body and were more sensitive to the multi-sensory delay, suggesting an increased tendency to 'fraction' senses in dissociation. Moreover, individuals with higher dissociation displayed similar cardiac reactivity to both self and other touch. These findings highlight two key mechanisms underlying dissociation; altered sensory-integration and increased awareness of self-action.

Body ownership alterations in stroke emerge from reduced proprioceptive precision and damage to the frontoparietal network

BACKGROUND

Stroke patients often experience alterations in their subjective feeling of ownership for the affected limb, which can hinder motor function and interfere with rehabilitation. In this study, we aimed at disentangling the complex relationship between sensory impairment, body ownership (BO), and motor control in stroke patients.

METHODS

We recruited 20 stroke patients with unilateral upper limb sensory deficits and 35 age-matched controls. Participants performed a virtual reality reaching task with a varying displacement between their real unseen hand and a visible virtual hand. We measured reaching errors and subjective ownership ratings as indicators of hand ownership. Reaching errors were modeled using a probabilistic causal inference model, in which ownership for the virtual hand is inferred from the level of congruency between visual and proprioceptive inputs and used to weigh the amount of visual adjustment to reaching movements.

FINDINGS

Stroke patients were more likely to experience ownership over an incongruent virtual hand and integrate it into their motor plans. The model explained this tendency in terms of a decreased capability of detecting visuo-proprioceptive incongruences, proportionally to the amount of proprioceptive deficit. Lesion analysis further revealed that BO alterations, not fully explained by the proprioceptive deficit, are linked to frontoparietal network damage, suggesting a disruption in higher-level multisensory integration functions.

CONCLUSIONS

Collectively, our results show that BO alterations in stroke patients can be quantitatively predicted and explained in a computational framework as the result of sensory loss and higher-level multisensory integration deficits.

FUNDING

Swiss National Science Foundation (163951).

Feeling touch through a mirror: The role of vision and body ownership in generating non-veridical tactile experiences

Tactile experience can be non-veridical, i.e., not related to the actual stimulation of one's body. Recently, using a mirror box procedure in healthy subjects, we found that during bilateral asymmetrical touches, the vision of the right-hand being stimulated, reflected in the mirror, elicited on the real left-hand the feeling of being touched in the same position as the right-hand. Because these errors resemble synchiria, we called these false feelings 'synchiric errors' (SEs). Here, we investigated both the role of top-down feeling of body ownership (BO) over the mirrored hand-using explicit (BO questionnaires) and implicit (Electrodermal Activity) measures of BO- and bottom-up visual processing-by manipulating the presence/absence of visual feedback-in generating SEs during the Tactile Quadrant Stimulation Test (TQS). In TQS, subjects had to indicate the position of a tactile stimulus, applied in asymmetrical quadrants on the dorsum of the two hands, under three conditions: Baseline (no vision), Mirror Condition Vision (MCV; full visual feedback), and Mirror Condition Blind (MCB; visual feedback occluded). We tested 35 healthy individuals. First, measures of BO indicated that most subjects felt the right reflected hand as their own left hand. Moreover, we found a significant presence of SEs in the MCV. Crucially, SEs were significantly higher for the left hand in MCV compared to Baseline and MCB, confirming the critical role of vision in inducing the non-veridical tactile experience. Moreover, the absence of a correlation between SEs and body ownership measures, and a double dissociation between them, indicate that SEs are driven by vision and not by an alteration of BO.

The exposure to body size distortions affects allocentric distance perception in extra-personal space

Previous research demonstrated that body size distortions induced by body illusion can influence spatial perception in near space. We investigated whether manipulating body size through a Full-Body Illusion-like paradigm influences allocentric distance perception in extra-personal space. Participants estimated the distance between landmarks in far space before and after a body illusion with standard or big bodies in anatomical (i.e., virtual and actual legs were aligned) or non-anatomical orientation (i.e., virtual legs were rotated by 45 degrees). We analysed space perception via Multidimensional Scaling for landmark configuration and distance misestimation. Embodiment occurred with bodies in anatomical orientation, while exposure to bigger bodies increased perceived distance, regardless of the presence of the embodiment. However, no significant changes emerged in the perception of landmark configuration. Findings indicated that, in extra-personal space, the distance perception between objects, rather than their shape configuration, is scaled based on a metric reference related to a seen body.

The Effect of a Single Session Rubber Hand Illusion on Pressure Pain Is Not Long-Lasting

BACKGROUND

Rubber hand illusion (RHI) is an experience that causes changes in body perception and awareness as a result of the integration of simultaneous perceived visual and tactile stimuli. After synchronous brush strokes with rubber and real hands, the person perceives the rubber hand as their own. RHI is known to alter pain perception. In this study, it was aimed to evaluate the effects of RHI on pressure pain threshold and continuity of this effect.

METHODS

Twenty-three volunteers who developed RHI were included in our study and two conditions, illusion (synchronous) and control (asynchronous), were applied. The illusion condition was created by synchronous brush strokes, while the control condition was created by asynchronous brush application using different frequency and different finger areas in the same individuals. In both conditions, pressure pain threshold measurements with an algometer were performed at four times: baseline/1st measurement, during the brush stroke/2nd measurement, at the end of the brush stroke/3rd measurement and after the hand was removed from the environment/4th measurement.

RESULTS

It was shown that RHI increased the pressure-pain threshold (p = 0.004) in healthy volunteers. Asynchronous brush strokes arranged as a control trial significantly decreased the pressure pain threshold (p = 0.002).

CONCLUSIONS

It was found that the threshold values that change during the brush strokes return to the initial state after the brush strokes are terminated and the rubber hand is removed from the environment so that the effect of the illusion does not last for a long time with a single session application.

The tangled threads: Unveiling the interplay between the sense of body ownership and the sense of agency in impacting the bodily-self representation in eating disorders

The feeling of owning a body (body ownership) and controlling its actions (sense of agency) contributes to the emergence of the bodily-self representation, whose alteration is at the root of the central psychopathology of Eating Disorders (EDs). Yet, studies addressing these aspects in EDs provided inconsistent results. Here, we simultaneously test body ownership and sense of agency in EDs compared to controls by exploiting different rubber hand illusion (RHI) paradigms (i.e., classic visuo-tactile, passive and active visuo-motor versions). In any RHI versions, no differences in the susceptibility to the illusion between EDs patients and controls emerged at the body ownership questionnaire, thus suggesting a normal multisensory integration mechanism. Crucially, correlation analysis revealed that a higher level of body dissatisfaction is associated with increased susceptibility to RHI, as measured by the body ownership questionnaire. Interestingly, patients with a bulimic variant of EDs reported agency toward the fake hand in the visuo-tactile RHI, revealing an abnormal sense of agency in absence of voluntary movement. Moreover, in the visuo-motor RHI, EDs patients exhibited a proprioceptive drift both in synchronous and asynchronous conditions. Hence, our results revealed a dissociation between explicit and implicit RHI measures, showing a more plastic bodily-self representation when the RHI enlists hand movements, leading to a stronger visual-capture of proprioception. This study contributes to understanding the intricate link between body ownership and agency, shedding light on the role of voluntary actions in driving the sense of self in EDs.

Evidence of a hierarchical representation in bodily self-consciousness: the neural correlates of embodiment and presence in virtual worlds

Introduction

Bodily Self-Consciousness (BSC) is the perception of bodily awareness that arises from the integration of neuronal signals in multiple sensory modalities. BSC is composed of embodiment (the perception of owning a body) and presence (the perception of being at a location). Converging lines of evidence suggest embodiment and presence are supported by different neural networks. Several models have been proposed to describe how BSC manifests from these networks, but how these networks interact is not fully understood. We propose that the perception of presence is predicated upon the perception of embodiment. Specifically, even though neural networks for presence and embodiment partially overlap, there exists a subset of brain areas that mediate the flow of information from those supporting embodiment to those supporting presence.

Methods

To test this model, sensory feedback was manipulated in a virtual environment to affect BSC, while measuring behavioral performance and physiological responses in relevant brain areas. Correlated versus uncorrelated feedback was used to manipulate perceptions of embodiment. First- versus third-person perspective was used to manipulate perceptions of presence.

Results

Mean reaction times and accuracy were better with correlated feedback and first-person perspective. Functional magnetic resonance imaging (fMRI) measurements of neuronal activity identified frontoparietal and temporoparietal brain areas that appear to support embodiment and presence, respectively. We compared the effect of embodiment manipulations on presence areas and vice versa. The effect sizes for manipulations of embodiment were greater than those for manipulations of presence. This trend was also observed for brain areas that appeared to encode both embodiment and presence.

Discussion

This data indicates that networks associated with embodiment and presence overlap, and brain areas that support presence may depend upon the activity of those that support embodiment.

Immersive virtual reality in the rehabilitation of athlete nerve entrapments

INTRODUCTION

The implementation of Virtual Reality technology is approaching a breakthrough within the medical, and rehabilitation fields. The level of immersion in the virtual environment is profound and the potential applications are vast.

METHODS

This article reviews the capabilities of Virtual Reality in conjunction with the rehabilitation of nerve entrapments in sport athletes and examines the interactions between our body and brain within the virtual realm. In clinical practice it could be used as a complement to face-to-face therapy to asynchronous use by the patient in any location as a telerehabilitation system.

CONCLUSION

The use of Virtual Reality is a novel, potential, and promising tool in the treatment of nerve entrapments, even possible in the form of telerehabilitation. The response of body and brain in a virtual setting is good, the evolutions in technology can only improve this and this need to be substantiated by further scientific research.

Development and validation of a pictographic assessment embodiment scale

Embodiment is a complex concept related to the subjective perception of an object as it belongs to its own body. In general, this construct has been evaluated by means of questionnaires, but validation studies in other cultures and limitations related with barriers of language received little attention. The purpose of the present investigation was twofold: to validate the factorial structure of embodiment questionnaire (EQ) and to construct a pictographic scale (PAE) to measure embodiment without relapse verbal representations. In the first experiment, 136 participants underwent a Rubber Hand Illusion (RHI) procedure following both congruent and incongruent (control) visuo-tactile stimulations. Then, they evaluated embodiment illusion in EQ using a Likert-type scale to rate their agreement or disagreement with 27 statements and with a pictographic scale designed to assess their subjective experience of the illusion. Principal components analysis in EQ scores identified four components that emerged in both conditions: Embodiment, Disembodiment, Affect and Deafference. PAE scale was highly correlated with embodiment factor and can differentiate between conditions. In a second experiment, 30 participants underwent the RHI procedure, and they were assessed using PAE and proprioceptive drift. Results indicate a high positive correlation between PAE and post-illusion drift score. These results provide evidence about the consistency of the factorial structure of EQ across cultures, and we also provide a new pictographic tool that allows quick measurement of embodiment overcoming language barriers.

Time course of the rubber hand illusion-induced analgesia

Introduction

Previous investigations on pain modulatory effects of the rubber hand illusion (RHI) yielded mixed results. However, these studies used separate stimuli to induce pain and the RHI. Using a visual-thermal stimulation approach, the illusion-inducing stimulus was simultaneously the pain stimulus which ensured that participants focused entirely on the illusion-inducing stimulus.

Objectives

In this study, we investigated the time course of pain modulation induced by illusionary body ownership over artificial hands using the visual-thermal RHI and the influence of the stimulation intensity.

Methods

In a 2 × 4 within-subject design, participants received thermal stimulation on their hidden real left hand, while the rubber hand synchronously lit up red. Four stimulation intensities were used: moderate pain (+0°C), -0.75°C, +0.75°C, and +1.5°C. For control trials, the rubber hand was rotated by 180°. With the right hand, participants provided continuous pain ratings using a slide knob.

Results

Embodiment ratings were higher in the RHI compared with the control condition. Continuous pain ratings were lower in the RHI condition for all temperature levels except for +0.75°C. Rubber hand illusion-induced pain reduction was observed throughout most of the stimulation interval, absent only at the very beginning and end.

Conclusion

These findings suggest that visual-thermal induction of the RHI is consistently associated with increased embodiment ratings, regardless of the temperature level presented. The illusion is further accompanied by reduced pain ratings throughout major parts of the stimulation interval. On the whole, these findings speak for the robustness of the effect and the practicality of our visual-thermal stimulation approach.

Dissociations between bodily self-awareness components in women with Anorexia Nervosa

The awareness of our body arises from the convergence between physical (e.g., autonomic signals, perception of body in space) and mental (e.g., subjective sensations) components. The divergence between these components could characterise bodily self-awareness distortions that are typical of some neuropsychiatric syndromes, such as Anorexia Nervosa. We investigated this hypothesis by testing 22 women with restrictive-type AN and a matched sample of 22 healthy women with a multisensory integration paradigm. Participants underwent the Mirror Box Illusion, by which we explored three different (typically convergent) elements of bodily self-awareness: (i) the subjective experiences of embodiment, (ii) hand localisation, and (iii) the skin temperature change associated with the manipulation. In people with AN, we found an altered orchestration between skin temperature changes, explicit sensations of embodiment and proprioceptive bias. These components were modulated differently by the experimental condition compared to healthy controls. These findings suggest that targeted interventions to restore the convergence bodily self-awareness components might be beneficial in treating the self distortions associated with AN.

The acceptability, feasibility, and usability of a virtual reality pain education and rehabilitation program for Veterans: a mixed-methods study

Introduction

Persistent pain is a leading cause of medical discharges for Veterans. Pain science education (PSE) aims to better people's understanding about pain and is effective at reducing pain and depressive symptoms in Veterans. Preliminary evidence suggests virtual reality (VR)-delivered PSE has clinical benefits for people with persistent pain. This study investigated the acceptability, feasibility, and usability for VR-PSE for Veterans with persistent pain.

Methods

Veterans (n = 7) and healthcare professionals (HCPs) experienced in treating Veterans (n = 5) participated in workshops that involved working through the VR-PSE program, online questionnaires, and a focus group. Quantitative data were analysed by descriptive statistics. Qualitative data were analysed using a framework analysis according to the Theoretical Framework of Acceptability (TFA). A mixed-methods analysis combined the quantitative and qualitative data via triangulation, with the findings presented according to the TFA domains.

Results

The VR-PSE program was considered easy to use, engaging, and adaptable for different functional capabilities. Appropriate screening for contraindications prior to using the VR-PSE program was considered important by HCPs. Both Veterans and HCPs emphasized the need for a trusting client-clinician relationship to improve the acceptability of the VR-PSE program.

Discussion

Overall, the VR-PSE program was found to be acceptable, feasible, and usable and may be a useful tool to incorporate into the clinical management of Veterans with persistent pain. Further research is needed to investigate the efficacy of VR-PSE programs on clinical outcomes for Veterans with persistent pain.

Addressing Disturbance in Bodily Experience After Ventricular Assist Device Implantation: A Multicenter Randomized Controlled Trial of Curricular Psychological Support

BACKGROUND

Disturbance in bodily experience (BE) after ventricular assist device (VAD) implantation is common. This study aims to investigate the effect of focused psychological support to improve BE in VAD patients.

METHODS

This national, multicenter, longitudinal study enrolled 140 VAD patients from four centers across Germany in a prospective, randomized controlled trial. Patients were randomized (1:1) to receive curricular and focused psychological intervention in the post-implantation step-down units after implantation (n = 70) or treatment as usual (n = 70). BE was assessed using the Bodily Experience Scale in VAD Patients (BE-S) after implantation (baseline) and followed up 12 months later. Data were analyzed using mixed-effects models.

RESULTS

VAD patients with disturbance in BE (BE-S ≥ 2) after implantation (n = 43, 63.24%) benefit from the targeted intervention. Compared to the subsample of the control group (CG) patients with initial BE disturbance (n = 46, 69.7%), the intervention group (IG) displays a significantly stronger decrease from baseline to the 1-year follow-up (p = 0.01). Generally, women (p = 0.4) and emergently implanted patients (p = 0.24) show a smaller, albeit not significant, decrease in BE disturbance. All patients have high overall gratitude scores, which increase slightly but not significantly over time.

CONCLUSION

The efficacy of targeted psychological support in reducing disturbance in BE among VAD patients is highlighted. Given the strong correlation between BE and other mental health domains, such as anxiety and depression, it is essential to address disturbances in BE to improve the overall mental health of VAD patients.

Relating proprioceptive embodiment to body dissatisfaction in anorexia and bulimia patients: effect of visual body images

Eating disorders (ED) are associated with a maladaptive body schema and several cognitive biases. This pilot study aimed to investigate the effect of visual stimulation by body images on maladaptive body schema and body dissatisfaction in patients with ED. The rubber hand illusion (RHI) was applied to a sample of 33 women with anorexia or bulimia nervosa and 27 control subjects. The RHI was administered in a novel way using a standard-sized hand that had been distorted in appearance (perceived as unsatisfactory), and it was used before and after an ad hoc priming effect (exposure to thin-body media images). In accordance with the maladaptive body schema, ED patients exhibited higher scores on the Body Shape and Body Perception Questionnaires (with a positive correlation between the scores) and there was a significant increase in scores for all items in the location-proprioception and agency domains. However, before the priming effect, the ED sample showed significantly lower scores on all proprioceptive drift items during the distorted RHI condition and the regression analysis demonstrated a significant association between reduced proprioceptive drift (recording a similar embodiment index to healthy subjects) and improved body dissatisfaction. Following the priming effect, the proprioceptive drift embodiment index increased, and no ANOVA interaction was recorded. The maladaptive body schema in patients with bulimia or anorexia nervosa is characterised by both distorted proprioception and high interoceptive awareness. The visual body images that are perceived as unsatisfactory play a role in preserving proprioception and consequently in reducing body dissatisfaction. Conversely, the exposure effect of thin-body ideal images is involved in the maladaptive body schema.

Impact of an upper limb motion-driven virtual rehabilitation system on residual motor function in patients with complete spinal cord injury： a pilot study

BACKGROUND

Assessing residual motor function in motor complete spinal cord injury (SCI) patients using surface electromyography (sEMG) is clinically important. Due to the prolonged loss of motor control and peripheral sensory input, patients may struggle to effectively activate residual motor function during sEMG assessments. The study proposes using virtual reality (VR) technology to enhance embodiment, motor imagery (MI), and memory, aiming to improve the activation of residual motor function and increase the sensitivity of sEMG assessments.

METHODS

By Recruiting a sample of 12 patients with AIS A/B and capturing surface electromyographic signals before, druing and after VR training, RESULTS: Most patients showed significant electromyographic improvements in activation frequency and or 5-rank frequency during or after VR training. However, one patient with severe lower limb neuropathic pain did not exhibit volitional electromyographic activation, though their pain diminished during the VR training.

CONCLUSIONS

VR can enhance the activation of patients' residual motor function by improving body awareness and MI, thereby increasing the sensitivity of sEMG assessments.

Modulation of thermal perception by VR-based visual stimulation to the embodied virtual body

Visual stimulation to the embodied virtual body could modulate human perception, however the associated neurophysiological mechanisms have not elucidated yet. The present study aimed to reveal the underlying neurophysiological mechanisms from a neurophysiological viewpoint. Fifteen healthy participants were subjected to three visual conditions (i.e., fire, water, and non-visual effect conditions) and psychological pain stimulation (thermal grill stimulation). Oscillatory neural activities during stimulation were measured with electroencephalogram. The association between accessory visual stimulation applied to the embodied virtual body, induced by virtual reality, and perception was examined through neuronal oscillatory analysis using electroencephalogram data. Regression analysis was performed to obtain data on brain regions contributing to sensory modulation with body illusion. The results of subjective measures under the fire and water conditions showed that thermal perception were modulated by a visual stimulus to the virtual hand. Furthermore, we found that the insula was commonly associated with thermal perception under the fire and water conditions. This result indicate that the insula may control sensory information as a gatekeeper as well as facilitate the access to human attention and cognition as a hub, suggesting the influence on perception and cognition.

How pain and body representations transform each other: A narrative review

Pain, as a multidimensional and subjective experience, intertwines with various aspects of body representation, involving sensory, affective and motivational components. This review explores the bidirectional relationship between pain and body representations, emphasizing the impact of the sense of ownership on pain perception, the transformative impact of pain on motor imagery, the effects associated with vicarious pain perception on body representations and the role of pain in the maintenance of body representations in specific clinical conditions. Literature indicates complex interactions between pain and body representations, with the sense of ownership inducing analgesic effects in some cases and hyperalgesia in others, contingent upon factors such as the appearance of the affected limb. Pain sensations inform the body on which actions might be executed without harm, and which are potentially dangerous. This information impacts on motor imagery too, showing reduced motor imagery and increased reaction times in tasks where motor imagery involves the painful body parts. Finally, contrary to the conventional view, according to which pain impairs body representation, evidence suggests that pain can serve as an informative somatosensory index, preserving or even enhancing the representation of the absent or affected body parts. This bidirectional relationship highlights the dynamic and multifaceted nature of the interplay between pain and body representations, offering insights into the adaptive nature of the central nervous system in response to perceived bodily states.

Body Ownership and the Motor System: Rapid Facilitation of Embodied Fake Hand Movement on Actual Movement Execution

Body ownership-the perception that one's body belongs to oneself-has been explored using a rubber hand illusion, in which individuals misperceive a fake hand as their own (i.e., embodiment of the fake hand) when an unseen real hand and a visible fake hand are stroked synchronously. Thus, the movement of an embodied fake body may be represented in one's own sensorimotor system. Using a combination of the rubber hand illusion and a motor task, we investigated whether simple movement of the embodied fake hand influenced the subsequent movement of the participants' hand. The participants lifted their own index finger immediately upon observing the index finger lifting on the embodied (rubber hand illusion) or non-embodied (non-rubber hand illusion) fake hand (Experiment 1), and a light-emitting diode turning on near the fake hand (Experiment 2). The reaction times, peak velocities, and peak acceleration were extracted from the participants' finger-lifting movements. In Experiment 1, the reaction time was significantly shorter in the rubber hand illusion condition than in the non-rubber hand illusion condition, suggesting the rapid facilitation effect of embodied fake hand movement on actual movement. However, no such motor facilitation was observed in Experiment 2, confirming that the improved reaction time in Experiment 1 resulted from the visual movement of the fake hand rather than attention to the fake hand itself. In contrast to the reaction time, the peak velocity and acceleration did not differ significantly in either experiment. These findings reflect the similar sensorimotor representations of illusory and actual self-movement.

The role of visuomotor synchrony on virtual full-body illusions in children and adults

The present study explored the effects of visuomotor synchrony in virtual reality during the embodiment of a full human avatar in children (aged 5-6 years) and adults. Participants viewed their virtual bodies from a first-person perspective while they moved the body during self-generated and structured movement. Embodiment was measured via questions and psychophysiological responses (skin conductance) to a virtual body-threat and during both movement conditions. Both children and adults had increased feelings of ownership and agency over a virtual body during synchronous visuomotor feedback (compared to asynchronous visuomotor feedback). Children had greater ownership compared to adults during synchronous movement but did not differ from adults on agency. There were no differences in SCRs (frequency or magnitude) between children and adults, between conditions (i.e., baseline or movement conditions) or visuomotor feedback. Collectively, the study highlights the importance of visuomotor synchrony for children's ratings of embodiment for a virtual avatar from at least 5 years old, and suggests adults and children are comparable in terms of psychophysiological arousal when moving (or receiving a threat to) a virtual body. This has important implications for our understanding of the development of embodied cognition and highlights the considerable promise of exploring visuomotor VR experiences in children.

Words as social tools (WAT): A reprise

The paper presents new evidence collected in the last five years supporting the Words As social Tools proposal on abstract concepts. We discuss findings revolving around three central tenets. First, we show that-like concrete concepts-also abstract concepts evoke sensorimotor experiences, even if to a lower extent, and that they are linked to inner experiences (e.g., interoceptive, proprioceptive, and metacognitive). Second, we present findings suggesting that linguistic and social interaction are crucial for acquiring and using abstract concepts. Specifically, rating and behavioral studies reveal that people tend to feel uncertain about the meaning of abstract concepts. On top of that, with abstract concepts, people rely more on others to ask for information, negotiate conceptual meaning, or outsource their knowledge. We propose that inner speech might contribute both to the monitoring process and the preparation to interact with others. Finally, we illustrate recent studies conducted in our lab highlighting abstract concepts variability across individuals (age, expertise), cultures, and languages.

The Vagus Nerve as a Gateway to Body Ownership: taVNS Reduces Susceptibility to a Virtual Version of the Cardiac and Tactile Rubber Hand Illusion

Transcutaneous auricular vagus nerve stimulation (taVNS) has been shown to influence cognitive and emotional function and enhance interoceptive awareness. This study investigates if taVNS effects extend to the experience of body ownership, as measured via susceptibility to the rubber hand illusion (RHI) in a virtual reality setting. The experiment involved 27 participants who underwent real and sham stimulation in two separate sessions while experiencing synchronous or asynchronous visuo-cardiac and visuo-tactile feedback on a virtual arm in place of their own. Results indicated that active compared to sham taVNS decreased sensitivity to the illusion in both cardiac and tactile trials. Specifically, a greater proprioceptive drift difference (PDD) toward the rubber hand was observed for synchronous compared to asynchronous trials only during sham (t(26) = -4.58, pbonf < 0.001) but not during active (pbonf = 1.00) stimulation. A similar pattern was also observed for subjective ownership, where synchronous trials led to greater subjective ownership than asynchronous trials only during sham (t(26) = -3.52, pbonf = 0.010) but not during active (pbonf = 1.00) stimulation. These findings suggest that stimulation might enhance body ownership, making individuals more attuned to their real bodily signals and less susceptible to bodily illusions. Additionally, physiological measures such as heart rate (HR), heart rate variability (HRV), and skin sympathetic nervous activity (SKNA) were assessed to explore the autonomic effects of taVNS. We observed a decrease in HR during active stimulation (t(26) = 4.30, pbonf < 0.001), and an increase in SKNA during both sham (t(26) = -4.40, pbonf < 0.001) and active stimulation (t(26) = -4.85, pbonf < 0.002). These findings contribute to the understanding of the vagus nerve's role in integrating visceral and somatosensory signals, with implications for clinical applications in conditions characterized by altered interoception and body ownership.

Tool evolution as a prerequisite for consciousness

Within the concept of the extended mind, the active modification of external objects, externalizations, is seen as an auxiliary means to adapt to the environment. Toolmaking and use are advanced stages of externalizations that evolve. All past or present tools can, theoretically, be precisely assigned a location in an evolutionary tree with predecessors and progeny. Tools are reliably replicated, modified, and selected by their ability to facilitate human needs. Tool evolution, therefore, fulfills Darwinian criteria where the material tool is the phenotype and the instruction to build it is the code. The ostensive triangle consisting of a pointing individual, an observing individual, and a pointed-at object or tool is the germ cell of social transmission of instructions. Tool-building instructions ultimately can be reduced to distinct sequences of motor acts that can be recombined and are socially transmitted. When executed, they replicate tools for the reward of convenience or improved fitness. Tools elicit affordances relating to their use that synchronize different individuals' perceptions, result in psychological "understanding," and thereby modify social networks. Massive tool fabrication as present today in the "tool-sphere" has, therefore, accelerated prosociality and over time led to the acquisition of an individual's third person perspective. The entangled biological evolution accelerated the ongoing cumulative cultural evolution by selecting traits facilitating social transmission. In this context, tool evolution and the corresponding acquired individual instructional content is a precondition to the emergence of higher cognition and "consciousness." A neuroscience investigating externalizations as the starting point of this process is urgently needed.

Psychological induction of interoceptive hunger cues and their effect on food desire

Certain interoceptive hunger cues are caused by gut physiology. These interoceptive cues may have psychological consequences, namely an ability to enhance the desire to eat, which are independent of their physiological cause. Testing this idea is difficult because the physiological processes are normally linked to any consequence. In this preliminary report we attempted to induce an interoceptive hunger cue (a stomach rumble), to examine its psychological consequences independent from its physiological cause. In three online Studies (1-3), participants viewed images of food while listening to different sounds including quiet stomach rumbles and judged the source of the sound, and their desire to eat the depicted foods. In Studies 1-3, irrespective of when they last ate and their reported level of hunger, and relative to control sounds, stomach rumble sounds enhanced desire to eat depicted foods, especially when they were mislocalised to the participants' own stomachs. In Study 1 49% of participants reported some degree of mislocalisation, 74% in Study 2, and 77% in Study 3. Overall, around 40% reported mimicry, where they felt that hearing the computer-generated stomach rumble sound induced the same in themselves. In Study 3 heart beat sounds were included. These too were mislocalised, and enhanced desire to eat depicted foods. In sum, this preliminary report suggests it may be possible to psychologically induce interoceptive cues, including one specific to hunger, and that these cues may then enhance food desire when mislocalised to self. In addition, the findings support the idea that interoceptive hunger cues may have associative properties that augment desire to eat.

Lack of visual experience leads to severe distortions in the hand representation of the body model

This study investigates the impact of vision on the maintenance of hand representation in the implicit body model, particularly focusing on congenitally blind individuals. To address this, we performed a hand landmark localization task on blind individuals who lacked visual experience of their bodies and compared their performance to normally sighted and normally sighted but blindfolded participants. Through measurements of finger lengths, hand width, and shape index, we demonstrate that blind participants exhibit significantly greater distortions in their hand representation compared to sighted and blindfolded controls. Notably, blind individuals displayed a marked overestimation of hand width and an underestimation of finger lengths, particularly in digits D2, D3, and D4. Surprisingly, blind subjects with partial vision displayed more severe distortions than those with no residual vision. Furthermore, our findings reveal that late-blind participants exhibit similar levels of distortion as congenitally blind individuals, suggesting an extended period of susceptibility to the lack of visual input in shaping body representations. The Reverse Distortion (RD) hypothesis provides a plausible explanation for these distortions, suggesting that compensatory mechanisms occur within the body model to counteract the anisotropic cortical representations. Our results support this hypothesis: blind individuals have expanded cortical representations processing tactile information, so this could lead to more pronounced distortions in their hand representation of the body model. This underscores the importance of visual input in modulating body representations. Overall, our study highlights the malleability of body representations and the intricate interplay between sensory inputs and cortical processing in shaping the implicit body model.

The prediction-confirmation account of the sense of body ownership: Evidence from a rubber hand illusion paradigm

We investigated the contribution of multisensory predictions to body ownership, and beyond, to the integration of body-related signals. Contrary to the prevailing idea, according to which, to be integrated, cues necessarily have to be perceived simultaneously, we instead proposed the prediction-confirmation account. According to this account, a perceived cue can be integrated with a predicted cue as long as both signals are relatively simultaneous. To test this hypothesis, a standard rubber hand illusion (RHI) paradigm was used. In the first part of each trial, the illusion was induced while participants observed the rubber hand being touched with a paintbrush. In the subsequent part of the trial, (i) both rubber hand and the participant's real hand were stroked as before (i.e., visible/synchronous condition), (ii) the rubber hand was not stroke anymore (i.e., visible/tactile-only condition), or (iii) both rubber hand and the participant's real hand were synchronously stroked while the location where the rubber hand was touched was occulted (i.e., occulted/synchronous condition). However, in this latter condition, participants still perceived the approaching movement of the paintbrush. Thus, based on this visual cue, the participants can properly predict the timepoint at which the tactile cue should occur (i.e., visuotactile predictions). Our major finding was that compared with the visible/tactile-only condition, the occulted/synchronous condition did not exhibit a decrease of the RHI as in the visible/synchronous condition. This finding supports the prediction-confirmation account and suggests that this mechanism operates even in the standard version of the RHI.

Examining the physical and psychological effects of combining multimodal feedback with continuous control in prosthetic hands

Myoelectric prosthetic hands are typically controlled to move between discrete positions and do not provide sensory feedback to the user. In this work, we present and evaluate a closed-loop, continuous myoelectric prosthetic hand controller, that can continuously control the position of multiple degrees of freedom of a prosthesis while rendering proprioceptive feedback to the user via a haptic feedback armband. Twenty-eight participants without and ten participants with upper limb difference (ULD) were recruited to holistically evaluate the physical and psychological effects of the controller via isolated control and sensory tasks, dexterity assessments, embodiment and task load questionnaires, and post-study interviews. The combination of proprioceptive feedback and continuous control enabled more accurate position and force modulation than without proprioceptive feedback, and restored blindfolded object identification ability to open-loop discrete controller levels. Dexterity assessment and embodiment questionnaire results revealed no significant physical performance or psychological embodiment differences between control types, with the exception of perceived sensation questions, which were significantly higher (p < 0.001) for closed-loop controllers. Key differences between participants with and without ULD were identified, including increasingly lower perceived body completeness and heterogeneity in frustration in participants with ULD, which can inform future development and rehabilitation.

Somatosensory cortex and body representation: Updating the motor system during a visuo-proprioceptive cue conflict

The brain's representation of hand position is critical for voluntary movement. Representation is multisensory, combining visual and proprioceptive cues. When these cues conflict, the brain recalibrates its unimodal estimates, shifting them closer together to compensate. Converging evidence from research in perception, behavior, and neurophysiology suggest that such updates to body representation are communicated to the motor system to keep hand movements accurate. We hypothesized that primary somatosensory cortex (SI) is crucial in this updating process due to its role in proprioception and connections with primary motor cortex. We tested this hypothesis in two experiments. We predicted that proprioceptive, but not visual, recalibration would be associated with change in short latency afferent inhibition (SAI), a measure of sensorimotor integration (influence of sensory input on motor output) (Expt. 1). We further predicted that modulating SI activity with repetitive transcranial magnetic stimulation (TMS) should affect recalibration of the proprioceptive estimate of hand position, but have no effect on the visual estimate or on the normal inverse relationship between proprioceptive and visual recalibration (Expt. 2). Our results are consistent with these predictions, supporting the idea that (1) SI is indeed a key region in facilitating motor system updates based on changes in body representation, and (2) this function is mediated by unisensory (proprioceptive) processing, separate from multisensory visuo-proprioceptive computations. Other aspects of the body representation (visual and multisensory) may be conveyed to the motor system via separate pathways, e.g. from posterior parietal regions to motor cortex.

Action of the Euclidean versus projective group on an agent's internal space in curiosity driven exploration

According to the Projective Consciousness Model (PCM), in human spatial awareness, 3-dimensional projective geometry structures information integration and action planning through perspective taking within an internal representation space. The way different perspectives are related to and transform a world model defines a specific perception and imagination scheme. In mathematics, such a collection of transformations corresponds to a 'group', whose 'actions' characterize the geometry of a space. Imbuing world models with a group structure may capture different agents' spatial awareness and affordance schemes. We used group action as a special class of policies for perspective-dependent control. We explored how such a geometric structure impacts agents' behaviors, comparing how the Euclidean versus projective groups act on epistemic value in active inference, drive curiosity, and exploration. We formally demonstrate and simulate how the groups induce distinct behaviors in a simple search task. The projective group's nonlinear magnification of information transformed epistemic value according to the choice of frame, generating behaviors of approach toward objects with uncertain locations due to limited sampling. The Euclidean group had no effect on epistemic value: no action was better than the initial idle state. In structuring a priori an agent's internal representation, we show how geometry can play a key role in information integration and action planning. Our results add further support to the PCM.

Current virtual reality-based rehabilitation interventions in neuro-developmental disorders at developmental ages

This mini-review examines the available papers about virtual reality (VR) as a tool for the diagnosis or therapy of neurodevelopmental disorders, focusing on Attention Deficit Hyperactivity Disorder (ADHD), Autism Spectrum Disorder (ASD), and Specific Learning Disorders (SLD). Through a search on literature, we selected 62 studies published between 1998 and 2024. After exclusion criteria, our synoptic table includes 32 studies on ADHD (17 were on diagnostic evaluation and 15 were on therapeutic interventions), 2 on pure ASD, and 2 on pure SLD. These cover a total of 8,139 participants with ADHD (ages 3-19), 458 with ASD (ages 4-19), and 162 with SLD (ages 7-11). Results show that VR offers high ecological validity and enables improvements in cognitive and social skills. Specifically, in individuals with ADHD, VR showed benefits in attention and executive function, with optimal results when combined with pharmacological treatments. For ASD kids, VR proved effective in enhancing social skills and emotional regulation through personalized virtual scenarios. However, the literature on SLD remains limited, suggesting an evolving area of research. Despite limitations related to small sample sizes and technology costs, VR presents a promising outlook for clinical intervention in neuro-developmental disorders, supporting enhanced skills in a safe and controlled environment. We conclude that both immersive and non-immersive VR represents a valuable supplement to traditional therapies, allowing for personalized approaches.

The contribution of cutaneous thermal signals to bodily self-awareness

Thermosensory signals may contribute to the sense of body ownership, but their role remains highly debated. We test this assumption within the framework of pathological body ownership, hypothesising that skin temperature and thermoception differ between right-hemisphere stroke patients with and without Disturbed Sensation of Ownership (DSO) for the contralesional plegic upper limb. Patients with DSO exhibit lower basal hand temperatures bilaterally and impaired perception of cold and warm stimuli. Lesion mapping reveals associations in the right Rolandic Operculum and Insula, with these regions linked to lower skin temperature located posterior to those associated with thermoception deficits. Disconnections in bilateral parietal regions are associated with lower hand temperature, while disconnections in a right-lateralized thalamus-parietal hub correlate with thermoception deficits. We discuss the theoretical implications of these findings in the context of the ongoing debate on the role of homeostatic signals in shaping a coherent sense of body ownership.

Baseline dependent differences in the perception of changes in visuomotor delay

Introduction

The detection of, and adaptation to delayed visual movement feedback has been extensively studied. One important open question is whether the Weber-Fechner Laws hold in the domain of visuomotor delay; i.e., whether the perception of changes in visuomotor delay depends on the amount of delay already present during movement.

Methods

To address this, we developed a virtual reality based, continuous hand movement task, during which participants had to detect changes in visuomotor mapping (delay): Participants (N = 40) performed continuous, auditory-paced grasping movements, which were measured with a data glove and transmitted to a virtual hand model. The movements of the virtual hand were delayed between 0 and 700 ms with the delay changing repeatedly in a roving oddball design. Participants had to indicate any perceived delay changes by key press. This design allowed us to investigate detection accuracy and speed related to the magnitude of the delay change, and to the "baseline" delay present during movement, respectively.

Results

As expected, larger delay changes were detected more accurately than smaller ones. Surprisingly, delay changes were detected more accurately and faster when participants moved under large > small delays.

Discussion

These results suggest that visual movement feedback delay indeed affects the detection of changes in visuomotor delay, but not as predicted by the Weber-Fechner Laws. Instead, bodily action under small delays may have entailed a larger tolerance for delay changes due to embodiment-related intersensory conflict attenuation; whereas better change detection at large delays may have resulted from their (visual) saliency due to a strong violation of visuomotor predictions.

Borders of physical self in virtual reality: a systematic review of virtual hand position discrepancy detection

Introduction

Virtual reality (VR) holds significant promise for psychiatric research, treatment, and assessment. Its unique ability to elicit immersion and presence is important for effective interventions. Immersion and presence are influenced by matching-the alignment between provided sensory information and user feedback, and self-presentation-the depiction of a user's virtual body or limbs. Discrepancies between real and virtual hands can affect the sense of presence and thus treatment efficacy. However, the precise impact of positional offsets in healthy individuals remains under-explored. This review assesses how various factors influence the detection thresholds for positional offsets in VR among healthy subjects.

Methods

A comprehensive database search targeted English-language studies on the detection thresholds of virtual hand positional offsets using head-mounted displays (HMDs) with specific tracking capabilities. Data on methodologies, participant demographics, and VR system specifics were extracted.

Results

Thirteen studies met the inclusion criteria, revealing significant variability in detection thresholds-from a few millimeters to 42 cm for linear shifts and from 2° to 45° for angular shifts. Sensitivity to these offsets was affected by hand movement direction and magnitude, hand representation realism, and the presence of distractions. VR system specifications, such as resolution and tracking accuracy, also played a significant role. Methodological issues included small sample sizes, inadequate demographic reporting, and inconsistent presence or avatar embodiment measures.

Conclusion

The results highlight the need to consider identified influencing factors to maximize user presence in VR-based therapies. Variability in VR device capabilities also emphasizes the need for detailed reporting of device properties in research. The individual variability in offset detection further illustrates VR's potential as a tool for studying body ownership and multisensory integration.

Focusing Attention to Improve Throwing Skills in Children With Autism Spectrum Disorder: Exploring the Influence of Working Memory

This study is aimed at investigating the impact of internal and external attention focus on learning a throwing skill in children with autism, as well as the relationship between working memory and learning rate. Twenty-four children aged 6-8 years with autism were assigned to internal and external attention groups. Participants performed a throwing task while their working memory was assessed using Cornoldi's working memory test. The data was analyzed using ANOVA with repeated measures involving two attention instructions and five blocks during the acquisition stage. An independent t-test was conducted during the retention phase. Furthermore, a Pearson correlation test was utilized to explore any potential relationship between working memory and performance in both the acquisition and retention stages. Data analysis revealed no significant difference between the internal and external attention groups during the acquisition phase (p > 0.05), but a significant difference was found in the retention phase (p < 0.05). There was no correlation between working memory and learning outcomes (p > 0.05). The results suggest that internal attention may enhance motor learning in children with autism, and reducing working memory load does not necessarily favor external attention.

Self /other recognition and distinction in adolescents with anorexia nervosa: A pilot study using a double mirror paradigm

BACKGROUND

Abnormalities in body perception in patients affected by anorexia nervosa have been widely studied, but without explicit reference to their relationship to others and the social processes involved. Yet, there are a several arguments supporting impairments in interpersonal relationships in these patients. Notably, some evidence suggests that self/other distinction (SOD), the ability to distinguish one's own body, actions and mental representations from those of others could be impaired. But research remains scarce in this area.

MATERIAL AND METHODS

A single-centre, prospective pilot study was conducted to investigate, for the first time, self-recognition and SOD in seven adolescents with anorexia nervosa compared with matched healthy controls (HCs) using the "Alter Ego"TM double mirror paradigm. This innovative device allows the progressive morphing of one's own face to that of another and vice versa between two subjects that interact on opposite sides of the device. Two judgement criteria were used: 1) M1: the threshold at which subjects start to recognize their own face during other-to-self morphing, and 2) M2: the threshold at which subjects start to recognize the other's face during self-to-other morphing. In a second part, SOD was reassessed during five different sensorimotor tasks aimed at increasing body self-consciousness in participants with anorexia nervosa.

RESULTS

The results showed that the participants with anorexia nervosa exhibited earlier self-recognition in the other-to-self sequence and delayed other-recognition in the self-to-other sequence. Furthermore, in contrast with that of HCs, the critical threshold for switching between self and other varied with the direction of morphing in anorexia nervosa participants. Finally, when participants with anorexia were seated in a chair with a backrest and footrest strengthening the median axis of their body, the self-recognition threshold (M1) increased significantly, approaching that of controls.

CONCLUSIONS

Although additional research is needed to replicate the results of this pilot study, it revealed the first behavioural evidence of altered SOD in individuals affected by anorexia nervosa through an embodied, semiecological face-recognition paradigm. The relationships between anomalies in body perception and alterations in interpersonal relationships are discussed within an integrative framework from phenomenology to neuroscience, and new research and therapeutic perspectives are presented.

Reconceptualizing Disorders of the Self as Disorders of Relationship

OBJECTIVE

To validate a universal neuropsychological model that suggests that disorders of the self are best conceptualized as disintegrated neuropsychological processes (ie, sensations, mental experiences) that lack a sense of relationship to the unified experience/sense of self.

DESIGN

Cross-sectional observational study.

SETTING

Rehabilitation hospital outpatient clinics.

PARTICIPANTS

A total of 73 individuals including 33 with acquired brain injury and 40 with multiple sclerosis.

INTERVENTION

Not applicable.

MAIN OUTCOME MEASURES

On the basis of the Cambridge Depersonalization Scale, a measure of general disintegration of sensations and mental experiences, a team of rehabilitation clinicians and researchers proposed 6 clinically derived indices of specific disintegrated neuropsychological inputs (ie, sensations), outputs (ie, mental experiences), and experiences of disintegration (ie, space, time, context).

RESULTS

As hypothesized (1) a confirmatory factor analysis supported the proposed factors including disintegrated bodily sensations (root mean square error of approximation [RMSEA]=0.193, P=.009; comparative fit index [CFI]=0.909; Tucker-Lewis index [TLI]=0.819), disintegrated context (RMSEA=0.143, P=.129; CFI=0.970; TLI=0.911), disintegrated emotions (RMSEA=0.090, P=.266; CFI=0.967; TLI=0.902), disintegrated cognition (RMSEA=0.091, P=.210; CFI=0.963; TLI=0.939), disintegrated smell/taste, and disintegrated spatial perception (measures of model fit for these last 2 factors could not be determined given they included only 2 items); and (2) Pearson correlations indicated that all 7 Cambridge Depersonalization Scale indices were negatively correlated with a measure associated with right hemisphere functioning, with 5 achieving/approaching statistical significance.

CONCLUSION

The results suggest that (1) neuropsychological abilities should be conceptualized in terms of relatively singular neuropsychological domains (ie, affect, behavior, cognition, sensation) and the experience of relationship that is created when they are integrated, and (2) disorders of the self are best conceptualized as disorders of disintegration that are associated with decreased relationship between specific neuropsychological processes and the unified experience/sense of self.

Rescaling perceptual hand maps by visual-tactile recalibration

After concurrent visual and tactile stimuli have been presented repeatedly with a spatial offset, unisensory tactile stimuli, too, are perceived with a spatial bias towards the previously presented visual stimuli. This so-called visual-tactile ventriloquism aftereffect reflects crossmodal recalibration. As touch is intrinsically linked to body parts, we asked here whether recalibration occurs at the level of individual stimuli or at a higher, integrated, map-like level. We applied tactile stimuli to participants' hidden left hand and simultaneously presented visual stimuli with spatial offsets that, if integrated with the tactile stimuli, implied a larger hand. After recalibration, participants pointed to tactile-only stimuli and judged the distance between two tactile stimuli on the hand. The pattern of changes in tactile localization after recalibration was consistent with participants aiming at targets on an enlarged hand. This effect was evident also for new, tactile-only locations that had not been paired with visual stimuli during recalibration. In contrast, distance judgements were not consistently affected by recalibration. The generalization of recalibration to new, non-trained stimulus sites, but not across tasks and responses, suggests a link of low-level multisensory processing and map-like body representations that may, however, be purpose-specific and not organized as a general-purpose "body schema".

Body as First Teacher: The Role of Rhythmic Visceral Dynamics in Early Cognitive Development

Embodied cognition-the idea that mental states and processes should be understood in relation to one's bodily constitution and interactions with the world-remains a controversial topic within cognitive science. Recently, however, increasing interest in predictive processing theories among proponents and critics of embodiment alike has raised hopes of a reconciliation. This article sets out to appraise the unificatory potential of predictive processing, focusing in particular on embodied formulations of active inference. Our analysis suggests that most active-inference accounts invoke weak, potentially trivial conceptions of embodiment; those making stronger claims do so independently of the theoretical commitments of the active-inference framework. We argue that a more compelling version of embodied active inference can be motivated by adopting a diachronic perspective on the way rhythmic physiological activity shapes neural development in utero. According to this visceral afferent training hypothesis, early-emerging physiological processes are essential not only for supporting the biophysical development of neural structures but also for configuring the cognitive architecture those structures entail. Focusing in particular on the cardiovascular system, we propose three candidate mechanisms through which visceral afferent training might operate: (a) activity-dependent neuronal development, (b) periodic signal modeling, and (c) oscillatory network coordination.

Investigating Passive Presentation Paradigms to Approximate Active Haptic Palpation

Active, exploratory touch supports human perception of a broad set of invisible physical surface properties. When traditionally hands-on tasks, such as medical palpation of soft tissue, are translated to virtual settings, haptic perception is throttled by technological limitations, and much of the richness of active exploration can be lost. The current research seeks to restore some of this richness with advanced methods of passively conveying haptic data alongside synchronized visual feeds. A robotic platform presented haptic stimulation modeled after the relative motion between a hypothetical physician's hands and artificial tissue samples during palpation. Performance in discriminating the sizes of hidden "tumors" in these samples was compared across display conditions which included haptic feedback and either: 1) synchronized video of the participant's hand, recorded during active exploration; 2) synchronized video of another person's hand; 3) no accompanying video. The addition of visual feedback did not improve task performance, which was similar whether receiving relative motion recorded from one's own hand or someone else's. While future research should explore additional strategies to improve task performance, this initial attempt to translate active haptic sensations to passive presentations indicates that visuo-haptic feedback can induce reliable haptic perceptions of motion in a stationary passive hand.

Women show enhanced proprioceptive target estimation through visual-proprioceptive conflict resolution

To form a unified and coherent perception of the organism's state and its relationship with the surrounding environment, the nervous system combines information from various sensory modalities through multisensory integration processes. Occasionally, data from two or more sensory channels may provide conflicting information. This is particularly evident in experiments using the mirror-guided drawing task and the mirror-box illusion, where there is conflict between positional estimates guided by vision and proprioception. This study combined two experimental protocols (the mirror-box and the mirror-guided drawing tasks) to examine whether the learned resolution of visuo-proprioceptive conflicts in the mirror-guided drawing task would improve proprioceptive target estimation of men and women during the mirror-box test. Our results confirm previous findings of visual reaching bias produced by the mirror-box illusion and show that this effect is progressively reduced by improvement in the mirror drawing task performance. However, this was only observed in women. We discuss these findings in the context of possible gender differences in multisensory integration processes as well as in embodiment.

I am where I believe my body is: The interplay between body spatial prediction and body ownership

Body ownership refers to the feeling that the body belongs to oneself. This study explores how our ability to predict our body's location in space influences feelings of ownership and disownership towards it, comparing two illusion techniques: the virtual Rubber Hand Illusion (vRHI) and the first-person perspective Full-Body Illusion (1pp-FBI). Participants were exposed to each illusion, where they observed a virtual body aligned or misaligned with their own. Participants observed the virtual body for 60s (i.e., visual exposure) and then experienced the multisensory body illusion. During the illusion, participants received tactile stimulation while observing the avatar being synchronously touched. After two minutes, a virtual knife appeared and stabbed the virtual body. We recorded the Skin Conductance Response (SCR) as an implicit embodiment measure. After the visual exposure and the body illusion, we administered a Body Localization Task to evaluate the body's perceived position and a questionnaire to measure embodiment and disembodiment subjective experience. We performed a series of Bayesian regression in a factorial within-subject design. Results showed that both illusions increased feelings of ownership, but this effect was weaker in the misaligned 1pp-FBI. Interestingly, disownership only occurred in the misaligned 1pp-FBI, particularly when the legs were misaligned. Additionally, we found a recalibration of the body's position toward the misaligned virtual body, but no changes emerged when the real and the fake body were aligned. Correlation analyses partially supported the hypothesis that the perceived body's position influences embodiment sensations in the 1pp-FBI. These findings suggest that our perception of where our body is in space plays a crucial role in how much we feel it belongs to us, supporting the idea that ownership may be more related to the perceived location than the body itself.

Evaluation of a New Mobile Virtual Reality Setup to Alter Pain Perception: Pilot Development and Usability Study in Healthy Participants

Background

Chronic pain presents a significant treatment challenge, often leading to frustration for both patients and therapists due to the limitations of traditional methods. Research has shown that synchronous visuo-tactile stimulation, as used in the rubber hand experiment, can induce a sense of ownership over a fake body part and reduces pain perception when ownership of the fake body part is reported. The effect of the rubber hand experiment can be extended to the full body, for example, during the full-body illusion, using both visuo-tactile and cardiovisual signals.

Objective

This study first aimed to evaluate the usability and accuracy of a novel, mobile virtual reality (VR) setup that displays participants' heartbeats as a flashing silhouette on a virtual avatar, a technique known as the cardiovisual full-body illusion. The second part of the study investigated the effects of synchronous cardiovisual stimulation on pain perception and ownership in 20 healthy participants as compared with asynchronous stimulation (control condition).

Methods

The setup comprised a head-mounted display (HMD) and a heart rate measurement device. A smartphone-based HMD (Samsung Galaxy S8+) was selected for its mobility, and heart rates were measured using smartwatches with photoplethysmography (PPG). The accuracy of 2 smartwatch positions was compared with a 5-point electrocardiogram (ECG) standard in terms of their accuracy (number and percent of missed beats). Each participant underwent two 5-minute sessions of synchronous cardiovisual stimulation and two 5-minute sessions of asynchronous cardiovisual stimulation (total of 4 sessions), followed by pain assessments. Usability, symptoms of cybersickness, and ownership of the virtual body were measured using established questionnaires (System Usability Scale, Simulator Sickness Questionnaire, Ownership Questionnaire). Pain perception was assessed using advanced algometric methods (Algopeg and Somedic algometer).

Results

Results demonstrated high usability scores (mean 4.42, SD 0.56; out of 5), indicating ease of use and acceptance, with minimal side effects (mean 1.18, SD 0.46; out of a possible 4 points on the Simulator Sickness Questionnaire). The PPG device showed high heart rate measurement precision, which improved with optimized filtering and peak detection algorithms. However, compared with previous work, no significant effects on body ownership and pain perception were observed between the synchronous and asynchronous conditions. These findings are discussed in the context of existing literature on VR interventions for chronic pain.

Conclusions

In conclusion, while the new VR setup showed high usability and minimal side effects, it did not significantly affect ownership or pain perception. This highlights the need for further research to refine VR-based interventions for chronic pain management, considering factors like visual realism and perspective.

Influence of interoception and body movement on the rubber hand illusion

Rubber hand illusion (RHI) refers to the illusory sense of body ownership of a fake hand, which is induced by synchronous visuotactile stimulation to the real and fake hands. A negative correlation was reported between the cardiac interoception and the strength of RHI, but the subsequent studies have been unsuccessful in replicating it. On the other hand, voluntary action is suggested to link interoception and the sense of body ownership in different situations. If so, moving RHI, induced by the active or the passive finger tapping while observing a fake hand, might reveal the relationship more clearly. The measurement of interoception has been another issue. We, therefore, examined the relationship between the moving RHI and two measures of interoception: interoceptive accuracy (IAcc) measured by the conventional heartbeat counting task and interoceptive sensibility (IS) measured using a questionnaire. For the classical visuotactile RHI, our results supported the lack of association between the interoception measures and RHI. For the moving RHI, a stronger sense of body ownership was induced for participants with higher IS regardless of active or passive movement, and a stronger sense of agency was caused by active than passive movement only for those with lower IAcc. These results reveal the dynamic links between the interoception and the bodily senses. The results also suggest that multiple dimensions of interoception affect the bodily senses differently.