Illusory Obesity Triggers Body Dissatisfaction Responses in the Insula and Anterior Cingulate Cortex

Perceptual Dysfunction in Eating Disorders

Eating disorders (EDs) are characterized by abnormal responses to food and weight-related stimuli and are associated with significant distress, impairment, and poor outcomes. Because many of the cardinal symptoms of EDs involve disturbances in perception of one's body or abnormal affective or cognitive reactions to food intake and how that affects one's size, there has been longstanding interest in characterizing alterations in sensory perception among differing ED diagnostic groups. Within the current review, we aimed to critically assess the existing research on exteroceptive and interoceptive perception and how sensory perception may influence ED behavior. Overall, existing research is most consistent regarding alterations in taste, visual, tactile, and gastric-specific interoceptive processing in EDs, with emerging work indicating elevated respiratory and cardiovascular sensitivity. However, this work is far from conclusive, with most studies unable to speak to the precise etiology of observed perceptual differences in these domains and disentangle these effects from affective and cognitive processes observed within EDs. Further, existing knowledge regarding perceptual disturbances in EDs is limited by heterogeneity in methodology, lack of multimodal assessment protocols, and inconsistent attention to different ED diagnoses. We propose several new avenues for improving neurobiology-informed research on sensory processing to generate actionable knowledge that can inform the development of innovative interventions for these serious disorders.

My mother, sisters, and I: Investigating the role of female family members in body dissatisfaction and disordered eating behaviours among young Middle-Eastern women

The global rise in body dissatisfaction and disordered eating concerns is apparent; however, limited research in Middle-Eastern populations gives an incomplete understanding of these concerns. The present study recruited 377 young women aged 18 to 25 years from the Middle-East for an online survey to determine how female family members may contribute to body dissatisfaction and disordered eating behaviours. Guided by the Tripartite Influence Model, we investigated the relationships between appearance pressures and fat talk, from mothers and sister(s), in predicting body dissatisfaction, and in turn, disordered eating symptomatology (restriction and bulimia), as mediated by appearance comparisons and internalisation of the thin-ideal. Overall, greater appearance pressures and fat talk from mothers and sister(s) were associated with body dissatisfaction and disordered eating symptomatology. Greater reported closeness in mother-daughter relationships, but not sister relationships, was associated with less perceived appearance pressure and fat talk by mothers, and lower appearance comparisons, body dissatisfaction and bulimia symptomatology. Finally, participants perceived greater appearance pressure from their mothers than their sister(s), but there was no difference in their perceived levels of fat talk. Findings demonstrate the applicability of a subsection of the Tripartite Influence Model in a non-Western and understudied population, namely in young Middle-Eastern women.

Did you skip leg day? The neural mechanisms of muscle perception for body parts

While the neural mechanisms underpinning the perception of muscularity are poorly understood, recent progress has been made using the psychophysical technique of visual adaptation. Prolonged visual exposure to high (low) muscularity bodies causes subsequently viewed bodies to appear less (more) muscular, revealing a recalibration of the neural populations encoding muscularity. Here, we use visual adaptation to further elucidate the tuning properties of the neural processes underpinning muscle perception for the upper and lower halves of the body. Participants manipulated the apparent muscularity of upper and lower bodies until they appeared 'normal', prior to and following exposure to a series of top/bottom halves of bodies that were either high or low in muscularity. In Experiment 1, participants were adapted to isolated own-gender body halves from one of four conditions; increased (muscularity) upper (body half), increased lower, decreased upper, or decreased lower. Despite the presence of muscle aftereffects when the body halves the participants viewed and manipulated were congruent, there was only weak evidence of muscle aftereffect transfer between the upper and lower halves of the body. Aftereffects were significantly weaker when body halves were incongruent, implying minimal overlap in the neural mechanisms encoding muscularity for body half. Experiment 2 examined the generalisability of Experiment 1's findings in a more ecologically valid context using whole-body stimuli, producing a similar pattern of results as Experiment 1, but with no evidence of cross-adaptation. Taken together, the findings are most consistent with muscle-encoding neural populations that are body-half selective. As visual adaptation has been implicated in cases of body size and shape misperception, the present study furthers our current understanding of how these perceptual inaccuracies, particularly those involving muscularity, are developed, maintained, and may potentially be treated.

Subcortical contributions to the sense of body ownership

The sense of body ownership (i.e. the feeling that our body or its parts belong to us) plays a key role in bodily self-consciousness and is believed to stem from multisensory integration. Experimental paradigms such as the rubber hand illusion have been developed to allow the controlled manipulation of body ownership in laboratory settings, providing effective tools for investigating malleability in the sense of body ownership and the boundaries that distinguish self from other. Neuroimaging studies of body ownership converge on the involvement of several cortical regions, including the premotor cortex and posterior parietal cortex. However, relatively less attention has been paid to subcortical structures that may also contribute to body ownership perception, such as the cerebellum and putamen. Here, on the basis of neuroimaging and neuropsychological observations, we provide an overview of relevant subcortical regions and consider their potential role in generating and maintaining a sense of ownership over the body. We also suggest novel avenues for future research targeting the role of subcortical regions in making sense of the body as our own.

Sense of own body shapes neural processes of memory encoding and reinstatement

How is the fundamental sense of one's body, a basic aspect of selfhood, incorporated into memories for events? Disrupting bodily self-awareness during encoding impairs functioning of the left posterior hippocampus during retrieval, which implies weakened encoding. However, how changes in bodily self-awareness influence neural encoding is unknown. We investigated how the sense of body ownership, a core aspect of the bodily self, impacts encoding in the left posterior hippocampus and additional core memory regions including the angular gyrus. Furthermore, we assessed the degree to which memories are reinstated according to body ownership during encoding and vividness during retrieval as a measure of memory strength. We immersed participants in naturalistic scenes where events unfolded while we manipulated feelings of body ownership with a full-body-illusion during functional magnetic resonance imaging scanning. One week later, participants retrieved memories for the videos during functional magnetic resonance imaging scanning. A whole brain analysis revealed that patterns of activity in regions including the right hippocampus and angular gyrus distinguished between events encoded with strong versus weak body ownership. A planned region-of-interest analysis showed that patterns of activity in the left posterior hippocampus specifically could predict body ownership during memory encoding. Using the wider network of regions sensitive to body ownership during encoding and the left posterior hippocampus as separate regions-of-interest, we observed that patterns of activity present at encoding were reinstated more during the retrieval of events encoded with strong body ownership and high memory vividness. Our results demonstrate how the sense of physical self is bound within an event during encoding, which facilitates reactivation of a memory trace during retrieval.

Distinct neural signatures of multimodal resizing illusions

Illusory body resizing typically uses multisensory integration to change the perceived size of a body part. Previous studies associate these multisensory body illusions with frontal theta oscillations and parietal gamma oscillations for dis-integration and integration of multisensory signals, respectively. However, recent studies also support illusory changes of embodiment from unimodal visual stimuli. This preregistered study (N = 48) investigated differences between multisensory visuo-tactile and unimodal visual resizing illusions using EEG, to gain a more comprehensive understanding of the neural underpinnings of resizing illusions in a healthy population. We hypothesised (1) stronger illusion in multisensory compared to unimodal, and unimodal compared to incongruent (dis-integration) conditions, (2) greater parietal gamma during multisensory compared to unimodal, and (3) greater frontal theta during incongruent compared to baseline conditions. Subjective Illusory results partially support Hypothesis 1, showing a stronger illusion in multisensory compared to unimodal conditions, but finding no significant difference comparing unimodal to incongruent conditions. Results partially supported EEG hypotheses, finding increased parietal gamma activity comparing multisensory to unimodal visual conditions, happening at a later stage of the illusion when compared to previous rubber hand illusion EEG findings, whilst also finding increased parietal theta activity when comparing incongruent to non-illusion conditions. While results demonstrated that only 27% of participants experienced the stretching illusion with unimodal visual stimuli compared to 73% of participants experiencing the stretching illusion in the multisensory condition, further analysis suggested that those who experience visual-only illusions exhibit a different neural signature to those who do not, with activity focussed around frontal and parietal regions early on in the illusory manipulation, compared to activity focussed more over parietal regions and at a later point in the illusory manipulation for the full sample of participants. Our results replicate previous subjective experience findings and support the importance of multisensory integration for illusory changes in perceived body size, whilst adding to our understanding of the temporal onset of multisensory integration within resizing illusions, differing from that of rubber hand illusions.

Neural mechanisms of perceptual and affective body-image disturbance during own-body and ideal-body estimation

Body-image disturbance is a core feature of eating disorders and can predict their development in healthy individuals. There are two components of body-image disturbance: perceptual disturbance (associated with overestimation of body size) and affective disturbance (associated with body dissatisfaction). Previous behavioral studies have hypothesized that attention to particular body parts and negative body-related emotions resulting from social pressure are associated with the respective degrees of perceptual and affective disturbance; however, the neural representations that underlie this hypothesis have not been elucidated. Thus, this study investigated the brain regions and connectivity associated with the degree of body-image disturbance. Specifically, we examined the brain activations associated with participants' estimation of the width of their actual and ideal bodies; we sought to determine which brain regions and functional connectivity from body-related visual processing regions were correlated with the degree of each component of body-image disturbance. The degree of perceptual disturbance was positively correlated with excessive width-dependent brain activations in the left anterior cingulate cortex when estimating one's body size; it was positively correlated with the functional connectivity between the left extrastriate body area and left anterior insula. The degree of affective disturbance was positively correlated with excessive width-dependent brain activation in the right temporoparietal junction and negatively correlated with functional connectivity between the left extrastriate body area and right precuneus when estimating one's ideal body size. These results support the hypothesis that perceptual disturbance is associated with attentional processing, whereas affective disturbance is associated with social processing.

Neural Substrates of Body Ownership and Agency during Voluntary Movement

Body ownership and the sense of agency are two central aspects of bodily self-consciousness. While multiple neuroimaging studies have investigated the neural correlates of body ownership and agency separately, few studies have investigated the relationship between these two aspects during voluntary movement when such experiences naturally combine. By eliciting the moving rubber hand illusion with active or passive finger movements during functional magnetic resonance imaging, we isolated activations reflecting the sense of body ownership and agency, respectively, as well as their interaction, and assessed their overlap and anatomic segregation. We found that perceived hand ownership was associated with activity in premotor, posterior parietal, and cerebellar regions, whereas the sense of agency over the movements of the hand was related to activity in the dorsal premotor cortex and superior temporal cortex. Moreover, one section of the dorsal premotor cortex showed overlapping activity for ownership and agency, and somatosensory cortical activity reflected the interaction of ownership and agency with higher activity when both agency and ownership were experienced. We further found that activations previously attributed to agency in the left insular cortex and right temporoparietal junction reflected the synchrony or asynchrony of visuoproprioceptive stimuli rather than agency. Collectively, these results reveal the neural bases of agency and ownership during voluntary movement. Although the neural representations of these two experiences are largely distinct, there are interactions and functional neuroanatomical overlap during their combination, which has bearing on theories on bodily self-consciousness.SIGNIFICANCE STATEMENT How does the brain generate the sense of being in control of bodily movement (agency) and the sense that body parts belong to one's body (body ownership)? Using fMRI and a bodily illusion triggered by movement, we found that agency is associated with activity in premotor cortex and temporal cortex, and body ownership with activity in premotor, posterior parietal, and cerebellar regions. The activations reflecting the two sensations were largely distinct, but there was overlap in premotor cortex and an interaction in somatosensory cortex. These findings advance our understanding of the neural bases of and interplay between agency and body ownership during voluntary movement, which has implications for the development of advanced controllable prosthetic limbs that feel like real limbs.

Relating different Dimensions of Bodily Experiences: Review and proposition of an integrative model relying on phenomenology, predictive brain and neuroscience of the self

How we mentally experience our body has been studied in a variety research domains. Each of these domains focuses in its own ways on different aspects of the body, namely the neurophysiological, perceptual, affective or social components, and proposes different conceptual taxonomies. It is therefore difficult to find one's way through this vast literature and to grasp the relationships between the different dimensions of bodily experiences. In this narrative review, we summarize the existing research directions and present their limits. We propose an integrative framework, grounded in studies on phenomenal consciousness, self-consciousness and bodily self-consciousness, that can provide a common basis for evaluating findings on different dimensions of bodily experiences. We review the putative mechanisms, relying on predictive processes, and neural substrates that support this model. We discuss how this model enables a conceptual assessment of the interrelationships between multiple dimensions of bodily experiences and potentiate interdisciplinary approaches.

Mediterranean-Style Diet and Other Determinants of Well-Being in Omnivorous, Vegetarian, and Vegan Women

Due to the lack of studies comparing the determinants of well-being in omnivores and vegetarians, we examined associations of socio-demographic and lifestyle factors, including adherence to a Mediterranean-style diet, in relation to well-being in omnivorous, vegetarian, and vegan women. Well-being was assessed using a validated WHO-5 Well-Being Index. Adherence to the Mediterranean-style diet was determined using a modified Mediterranean diet score. The study was conducted on 636 women (23.9 ± 5.7 years), of whom 47.3% were omnivores, 33.2% vegetarians, and 19.5% vegans. The good well-being group (WHO-5 Index ≥ 13 points) comprised 30.9% of the omnivores, 46.0% of the vegetarians, and 57.3% of the vegans. The remaining participants were classified as belonging to the poor well-being group (<13 points). Compared to the omnivores, the vegetarians and vegans had a 1.6-fold (95% CI: 1.04-2.42) and a 2.4-fold (95% CI: 1.45-3.99) higher probability of having good well-being, respectively. In omnivores, the predictors of good well-being were adherence to the Mediterranean-style diet (a 1-score increment was associated with a 17% higher probability of good well-being, P-trend = 0.016), higher self-perceived health status, and lower levels of stress. In vegetarians and vegans, it was older age, higher physical activity (≥3 h/week), 7-8 h sleep time, and similarly to omnivores' higher self-perceived health status and lower stress level. Our findings indicate that following a Mediterranean-style diet was associated with better well-being in omnivores. Furthermore, we identified that different determinants were associated with well-being in omnivorous and vegetarian and vegan women.

Embodying the avatar of an omnipotent agent modulates the perception of one's own abilities and enhances feelings of invulnerability

Immersive virtual reality can give people the illusion of owning artificial bodies (i.e., avatars) and controlling their actions. Tellingly, people appear to adhere to the newly embodied entities not just on the basis of physical traits but also behaving accordingly with the hallmarks of the represented characters. In two studies we pushed the limits of this process by testing if one's own sense of power could be affected by embodying the anthropomorphic representation of the Christian God, that is considered an omnipotent entity. A human Muscled and a Normotype avatar were used as controls. Results showed that participants embodying the God-avatar: (i) reacted to a threatening event compromising their physical safety by exhibiting a lower skin conductance response and heart rate deceleration compared to the Normotype-control avatar (Study 1); (ii) estimated they had more physical abilities compared to both the Normotype-control and the Muscled-control avatars (Study 2). Taken together, our findings suggest that embodying an omnipotent agent may exert an influence on people's perception of their own limits and capabilities, nourishing feelings of physical invulnerability and strength. Our study indicates that effectively embodying virtual role models may boost achievements and have translational implications in the field of empowerment.

Body weight distortions in an auditory-driven body illusion in subclinical and clinical eating disorders

Previous studies suggest a stronger influence of visual signals on body image in individuals with eating disorders (EDs) than healthy controls; however, the influence of other exteroceptive sensory signals remains unclear. Here we used an illusion relying on auditory (exteroceptive) signals to manipulate body size/weight perceptions and investigated whether the mechanisms integrating sensory signals into body image are altered in subclinical and clinical EDs. Participants' footstep sounds were altered to seem produced by lighter or heavier bodies. Across two experiments, we tested healthy women assigned to three groups based on self-reported Symptomatology of EDs (SED), and women with Anorexia Nervosa (AN), and used self-report, body-visualization, and behavioural (gait) measures. As with visual bodily illusions, we predicted stronger influence of auditory signals, leading to an enhanced body-weight illusion, in people with High-SED and AN. Unexpectedly, High-SED and AN participants displayed a gait typical of heavier bodies and a widest/heaviest visualized body in the 'light' footsteps condition. In contrast, Low-SED participants showed these patterns in the 'heavy' footsteps condition. Self-reports did not show group differences. The results of this pilot study suggest disturbances in the sensory integration mechanisms, rather than purely visually-driven body distortions, in subclinical/clinical EDs, opening opportunities for the development of novel diagnostic/therapeutic tools.

Curved sixth fingers: Flexible representation of the shape of supernumerary body parts

A recent perceptual illusion induces the feeling of having a sixth finger on one's hand. It is unclear whether the representation of supernumerary fingers is flexible for shape. To test whether we can embody a sixth finger with a different shape from our own fingers, we induced a sixth finger which curved laterally though 180°. Participants reported feeling both curved and straight sixth fingers, depending on the stimulation pattern. Visual comparative judgements of the felt curvature of the supernumerary finger, showed means of 182° in the curved condition, and 35° in the straight condition. Our results show we can feel a supernumerary finger with different shape from our actual fingers, indicating that shape is represented flexibly in the perception of our hands. This study also adds evidence to the independence of the supernumerary finger from the actual fingers, showing we can represent the sixth finger with its own shape.

Interoceptive sensibility and body satisfaction in pregnant and non-pregnant women with and without children

Pregnancy is a time of great physical and psychological change. As well as prominent changes in the external appearance of the body, such as the baby bump, there are also substantial changes taking place within the body. Our awareness of, and attention towards, internal bodily signals (interoception) is thought to have a direct impact on how we feel about our bodies. Therefore, understanding how our experience of these interoceptive signals might change during pregnancy may have important implications for maternal wellbeing. This study examined body satisfaction and interoceptive sensibility (subjective experience of interoception) in pregnant and non-pregnant women with and without children. Feelings towards pregnancy-specific changes in body satisfaction and interoceptive sensibility were also examined in women in their first pregnancy (primigravida) and subsequent pregnancies (multigravida). It was found that pregnancy did not directly impact levels of body satisfaction, instead pregnant and non-pregnant women with children reported less satisfaction with their bodies compared to those without children. Primigravida women were more satisfied with the appearance of pregnancy specific bodily changes compared to multigravida women. Interestingly, these differences in body satisfaction in those with children (pregnant and non-pregnant) were mediated by the extent to which women trusted their bodies (measure of interoceptive sensibility). All other pregnancy related changes in interoceptive sensibility and body satisfaction were either non-significant or had small effect sizes. These results may suggest body trust as an important factor to support during the transition to parenthood in order to improve body satisfaction in mothers.

Distortion of mental body representations

Our body is central to our sense of self, and distorted body representations are found in several serious medical conditions. This paper reviews evidence that distortions of body representations are also common in healthy individuals, and occur in domains including tactile spatial perception, proprioception, and the conscious body image. Across domains, there is a general tendency for body width to be overestimated compared to body length. Intriguingly, distortions in both eating disorders and chronic pain appear to be exaggerations of this baseline pattern of distortions, suggesting that these conditions may relate to dysfunction of mechanisms for body perception. Distortions of body representations provide a revealing window into basic aspects of self-perception.

Region-of-interest analysis approaches in neuroimaging studies of body ownership: An activation likelihood estimation meta-analysis

How do we feel that we own our body? By manipulating the integration of multisensory signals and creating the illusory experience of owning external body parts and entire bodies, researchers have investigated the neurofunctional correlates of body ownership. Recent attempts to synthesize the neuroimaging literature of body ownership through meta-analysis have shown partly inconsistent results. A large proportion of functional magnetic resonance imaging (fMRI) findings on body ownership include analyses based on regions of interest (ROIs). This approach can produce inflated findings when results are synthesized in meta-analyses. We conducted a systematic search of the fMRI literature of ownership of body parts and entire bodies. Three activation likelihood estimation (ALE) meta-analyses were conducted, testing the impact of including ROI-based findings. When both whole-brain and ROI-based results were included, frontal and posterior parietal multisensory areas were associated with body ownership. When only ROI-based results were included, larger areas of the frontal and posterior parietal cortices and the middle occipital gyrus were associated with body ownership. A whole-brain meta-analysis, excluding ROI-based results, found no significant convergence of activation across the brain. These findings highlight the difficulty of quantitatively synthesizing a neuroimaging field where a large part of the literature is based on findings from ROI-based analyses. We discuss these findings in the light of current practices within this field of research and highlight current problems of meta-analytic approaches of body ownership. We recommend the sharing of unthresholded data as a means to facilitate future meta-analyses of the neuroimaging literature of body ownership.

The long sixth finger illusion: The representation of the supernumerary finger is not a copy and can be felt with varying lengths

We can have a distorted perception of our body, instantly induced with multisensory illusions, anaesthesia or Virtual Reality, and recent studies show we can also feel extra body parts. Newport and colleagues (Newport et al., 2016) created an illusion that induces the feeling of having a sixth finger on one's hand, for a brief moment. By changing the paradigm with a double back and forth stroking, we were able to extend the duration of this illusion (Cadete & Longo, 2020), which can reflect an endured representation of a supernumerary finger. This innovation allowed us to test one specific distortion in the supernumerary finger: length. Patients with supernumerary phantom limb syndrome feel like they have an extra limb, as if one of their limbs was duplicated (Staub et al., 2006), resembling the same size and shape of the existing one. It is unclear from existing studies whether a supernumerary limb is represented as a copy of the existing limb, or if it is represented independently, with its own features. We therefore aimed to investigate whether the properties of the supernumerary sixth finger could be altered, independently of the actual little finger. Hence, we tested whether we can embody a sixth finger with double the size of the average little finger, and half its size. Participants reported feeling a long and a short sixth finger, and gave visual judgements on the felt length of the supernumerary finger, that matched the condition length. Overall, the results show that the supernumerary sixth finger is not a mere copy of the little finger but is represented independently, with distinct features from the existing finger. Moreover, the representation of the supernumerary finger is flexible, allowing the embodiment of a long or a short sixth finger.

Embodiment in Virtual Reality Intensifies Emotional Responses to Virtual Stimuli

Modulating emotional responses to virtual stimuli is a fundamental goal of many immersive interactive applications. In this study, we leverage the illusion of illusory embodiment and show that owning a virtual body provides means to modulate emotional responses. In a single-factor repeated-measures experiment, we manipulated the degree of illusory embodiment and assessed the emotional responses to virtual stimuli. We presented emotional stimuli in the same environment as the virtual body. Participants experienced higher arousal, dominance, and more intense valence in the high embodiment condition compared to the low embodiment condition. The illusion of embodiment thus intensifies the emotional processing of the virtual environment. This result suggests that artificial bodies can increase the effectiveness of immersive applications psychotherapy, entertainment, computer-mediated social interactions, or health applications.

Towards a Comprehensive Understanding of Body Image: Integrating Positive Body Image, Embodiment and Self-Compassion

Body image (BI) disturbance is a relevant factor in the etiology and treatment of eating disorders (ED). Although progress has been made in recent decades in understanding BI and its relationship with ED, the efficacy of BI disturbance prevention and intervention programs is still limited. In order to reach deeper understanding of BI disturbance and clarify the interactions between some protective and risk factors related to this construct, we carried out a literature review on some specific BI-related factors that so far have been analyzed independently. We specifically examined positive and negative BI; embodiment and its role in the development of positive and negative BI; and self-compassion as a protective factor that promotes positive embodiment (vs. disembodiment) and protection against body shame. We conclude that integrating the available evidence on these factors into BI models may be used to enhance our understanding of BI and improve the efficacy of prevention and intervention programs to help fight negative BI (by reducing body shame and disembodiment) and promote positive BI (by increasing self-compassion and positive embodiment).

Use of a real-life practical context changes the relationship between implicit body representations and real body measurements

A mismatch exists between people's mental representations of their own body and their real body measurements, which may impact general well-being and health. We investigated whether this mismatch is reduced when contextualizing body size estimation in a real-life scenario. Using a reverse correlation paradigm, we constructed unbiased, data-driven visual depictions of participants' implicit body representations. Across three conditions-own abstract, ideal, and own concrete body-participants selected the body that looked most like their own, like the body they would like to have, or like the body they would use for online shopping. In the own concrete condition only, we found a significant correlation between perceived and real hip width, suggesting that the perceived/real body match only exists when body size estimation takes place in a practical context, although the negative correlation indicated inaccurate estimation. Further, participants who underestimated their body size or who had more negative attitudes towards their body weight showed a positive correlation between perceived and real body size in the own abstract condition. Finally, our results indicated that different body areas were implicated in the different conditions. These findings suggest that implicit body representations depend on situational and individual differences, which has clinical and practical implications.

Changing your body changes your eating attitudes: embodiment of a slim virtual avatar induces avoidance of high-calorie food

The virtual-reality full-body illusion paradigm has been suggested to not only trigger the illusory ownership of the avatar's body but also the attitudinal and behavioral components stereotypically associated to that kind of virtual body. In the present study, we investigated whether this was true for stereotypes related to body size: body satisfaction and eating control behavior. Healthy participants underwent the full-body illusion paradigm with an avatar having either a larger or a slimmer body than their own, and were assessed for implicit attitudes towards body image and food calorie content at baseline and after each full-body illusion session. Results showed that the illusion emerged regardless of the avatar's body size, whereas the perceived dimension of the own body size changed according to the avatar's body size (i.e., participants felt to be slimmer after embodying their slim avatar and larger after embodying their large avatar). Crucially, we found that implicit attitudes towards food, but not those towards one's own body, were modulated by the size of the virtual body. Compared to baseline, ownership of a slimmer avatar increased the avoidance of high-calorie food, whereas ownership of a larger avatar did not induce changes. Our findings suggest that the illusory feeling of being slimmer drives also the food-related stereotypes associated with that body size, increasing the regulation of eating behaviors.

Body size overestimation in anorexia nervosa: Contributions of cognitive, affective, tactile and visual information

Body image disturbance (BID) in anorexia nervosa (AN) is poorly understood and the individual contribution of perceptual, cognitive, and affective components remains unclear. This study compared females with AN and matched healthy controls (HC) on a perceptual size estimation task. Participants (AN n=19 M[SD] age=16.97[2.24], HC n=19, age=15.77[2.17]) were blindfolded and estimated the size of neutral objects, safe foods, unsafe foods, and parts of their bodies (hips, waist, knees, ankle) over three blocks using: 1) no sensory information (baseline), 2) tactile information, and 3) added visual information. There were no significant differences between AN and HC on neutral and safe or unsafe food objects. Participants with AN were significantly more likely to overestimate their body size across blocks compared to HC. Both groups made fewer errors on unsafe foods and body parts when using tactile or visual information compared to baseline. Exploratory analyses revealed significant correlations between body size overestimation and drive for thinness and body dissatisfaction in the AN group, with body dissatisfaction being the most robust. Results suggest that both deficits in tactile and visual perception and affective factors play a role in BID for young women with AN.

The contribution of stimulating multiple body parts simultaneously to the illusion of owning an entire artificial body

The full-body ownership illusion exploits multisensory perception to induce a feeling of ownership of an entire artificial body. Although previous research has shown that synchronous visuotactile stimulation of a single body part is sufficient for illusory ownership of the whole body, the effect of combining multisensory stimulation across multiple body parts remains unknown. Therefore, 48 healthy adults participated in a full-body ownership illusion with conditions involving synchronous (illusion) or asynchronous (control) visuotactile stimulation to one, two, or three body parts simultaneously (2×3 design). We used questionnaires to isolate illusory ownership of five specific body parts (left arm, right arm, trunk, left leg, right leg) from the full-body ownership experience and sought to test not only for increased ownership in synchronous versus asynchronous conditions but also for potentially varying degrees of full-body ownership illusion intensity related to the number of body parts stimulated. Illusory full-body ownership and all five body-part ownership ratings were significantly higher following synchronous stimulation than asynchronous stimulation (p-values < .01). Since non-stimulated body parts also received significantly increased ownership ratings following synchronous stimulation, the results are consistent with an illusion that engages the entire body. Furthermore, we noted that ownership ratings for right body parts (which were often but not always stimulated in this experiment) were significantly higher than ownership ratings for left body parts (which were never stimulated). Regarding the effect of stimulating multiple body parts simultaneously on explicit full-body ownership ratings, there was no evidence of a significant main effect of the number of stimulations (p = .850) or any significant interaction with stimulation synchronicity (p = .160), as assessed by linear mixed modelling. Instead, median ratings indicated a moderate affirmation (+1) of an illusory full-body sensation in all three synchronous conditions, a finding mirrored by comparable full-body illusion onset times. In sum, illusory full-body ownership appears to be an 'all-or-nothing' phenomenon and depends upon the synchronicity of visuotactile stimulation, irrespective of the number of stimulated body parts.

The role of affective touch in whole-body embodiment remains equivocal

Previous studies have highlighted that affective touch delivered at slow velocities (1-10 cm/s) enhances body-part embodiment during multisensory illusions, yet its role towards whole-body embodiment is less established. Across two experiments, we investigated the role of affective touch towards subjective embodiment of a whole mannequin body within the full body illusion, amongst healthy females. Participants perceived affective touch to be more pleasant than non-affective touch, but this did not enhance subjective embodiment within the illusion and no interaction between synchrony (Experiment 1), or congruency (Experiment 2), and the velocity of touch was observed. Finally, the perceived pleasantness of touch was not modulated by subthreshold eating disorder psychopathology, as measured by means of a self-report questionnaire. Therefore, the present findings suggest that enhancement of embodiment due to affective touch may be body-part specific, and not generalise to greater ownership towards a whole body.

Duplication of the bodily self: a perceptual illusion of dual full-body ownership and dual self-location

Previous research has shown that it is possible to use multisensory stimulation to induce the perceptual illusion of owning supernumerary limbs, such as two right arms. However, it remains unclear whether the coherent feeling of owning a full-body may be duplicated in the same manner and whether such a dual full-body illusion could be used to split the unitary sense of self-location into two. Here, we examined whether healthy human participants can experience simultaneous ownership of two full-bodies, located either close in parallel or in two separate spatial locations. A previously described full-body illusion, based on visuo-tactile stimulation of an artificial body viewed from the first-person perspective (1PP) via head-mounted displays, was adapted to a dual-body setting and quantified in five experiments using questionnaires, a behavioural self-location task and threat-evoked skin conductance responses. The results of experiments 1-3 showed that synchronous visuo-tactile stimulation of two bodies viewed from the 1PP lying in parallel next to each other induced a significant illusion of dual full-body ownership. In experiment 4, we failed to find support for our working hypothesis that splitting the visual scene into two, so that each of the two illusory bodies was placed in distinct spatial environments, would lead to dual self-location. In a final exploratory experiment (no. 5), we found preliminary support for an illusion of dual self-location and dual body ownership by using dynamic changes between the 1PPs of two artificial bodies and/or a common third-person perspective in the ceiling of the testing room. These findings suggest that healthy people, under certain conditions of multisensory perceptual ambiguity, may experience dual body ownership and dual self-location. These findings suggest that the coherent sense of the bodily self located at a single place in space is the result of an active and dynamic perceptual integration process.

Extended Reality for the Clinical, Affective, and Social Neurosciences

Brain science research often involves the use of low-dimensional tools and stimuli that lack several of the potentially valuable features of everyday activities and interactions. Although this research has provided important information about cognitive, affective, and social processes for both clinical and nonclinical populations, there is growing interest in high-dimensional simulations that extend reality. These high-dimensional simulations involve dynamic stimuli presented serially or concurrently to permit the assessment and training of perceivers' integrative processes over time. Moreover, high-dimensional simulation platforms can contextually restrain interpretations of cues about a target's internal states. Extended reality environments extend assessment and training platforms that balance experimental control with emotionally engaging background narratives aimed at extending the affective experience and social interactions. Herein, we highlight the promise of extended reality platforms for greater ecological validity in the clinical, affective, and social neurosciences.

Which hand is mine? Discriminating body ownership perception in a two-alternative forced-choice task

The experience of one's body as one's own is referred to as the sense of body ownership. This central part of human conscious experience determines the boundary between the self and the external environment, a crucial distinction in perception, action, and cognition. Although body ownership is known to involve the integration of signals from multiple sensory modalities, including vision, touch, and proprioception, little is known about the principles that determine this integration process, and the relationship between body ownership and perception is unclear. These uncertainties stem from the lack of a sensitive and rigorous method to quantify body ownership. Here, we describe a two-alternative forced-choice discrimination task that allows precise and direct measurement of body ownership as participants decide which of two rubber hands feels more like their own in a version of the rubber hand illusion. In two experiments, we show that the temporal and spatial congruence principles of multisensory stimulation, which determine ownership discrimination, impose tighter constraints than previously thought and that texture congruence constitutes an additional principle; these findings are compatible with theoretical models of multisensory integration. Taken together, our results suggest that body ownership constitutes a genuine perceptual multisensory phenomenon that can be quantified with psychophysics in discrimination experiments.

Implicit mechanisms of body image alterations: The covert attention exposure effect

Visual exposure to extreme-sized bodies elicits explicit self-body image variations. Several features of such modulation remain to be clarified. In this study we explored whether this effect: (i) acts on implicit mechanisms in modifying one's body-size perception, (ii) is body-exposure-specific also at the implicit level, and (iii) is modulated by interoceptive sensibility. We assigned a covert attention task to 100 women, exposing them to extreme-sized bodies (thin and fat) or extreme-sized objects (thin and fat bottles). Before and after the attentional exposure, we tested the association between the "self/others" and "thin/fat" concepts using an Implicit Association Test. We also collected a measure of interoceptive sensibility by means of a self-report questionnaire. Results showed that participants exposed to fat bodies implicitly presented a stronger association between the "self" and "thin" concepts. This association was significantly weaker in the group exposed to thin bodies. This effect was absent after exposure to thin and fat bottles. Notably, participants with a higher tolerance of negative bodily interoceptive signals were less susceptible to the malleability of body image exerted by the exposure attentional task. Our findings shed new light on the relationship between the perception of internal (e.g., visceral) and external (e.g., visual) signals in the representation of our body.

Validity of Virtual Reality Body Exposure to Elicit Fear of Gaining Weight, Body Anxiety and Body-Related Attentional Bias in Patients with Anorexia Nervosa

Fear of gaining weight (FGW), body image disturbances, associated anxiety and body-related attentional bias are the core symptoms of anorexia nervosa (AN) and play critical roles in its development and maintenance. The aim of the current study is to evaluate the usefulness of virtual reality-based body exposure software for the assessment of important body-related cognitive and emotional responses in AN. Thirty female patients with AN, one of them subclinical, and 43 healthy college women, 25 with low body dissatisfaction (BD) and 18 with high BD, owned a virtual body that had their silhouette and body mass index. Full-body illusion (FBI) over the virtual body was induced using both visuo-motor and visuo-tactile stimulation. Once the FBI was induced, the FBI itself, FGW, body anxiety and body-related attentional bias toward weight-related and non-weight-related body areas were assessed. One-way analyses of covariance (ANCOVA), controlling for age, showed that AN patients reported higher FGW, body anxiety and body-related attentional bias than healthy controls. Unexpectedly, patients with AN reported significantly lower FBI levels than healthy participants. Finally, Pearson correlations showed significant relationships between visual analog scales and body-related attentional bias measures, compared to other eating disorder measures. These results provide evidence about the usefulness of virtual reality-based body exposure to elicit FGW and other body-related disturbances in AN patients. Thus, it may be a suitable intervention for reducing these emotional responses and for easing weight recovery.

Perception of Our Own Body Influences Self-Concept and Self-Incoherence Impairs Episodic Memory

How does our body affect the way we think about our personality? We addressed this question by eliciting the perceptual illusion that pairs of friends swapped bodies with each other. We found that during the illusion, the participants rated their own personality characteristics more similarly to the way they previously rated their friend's personality, and this flexible adjustment of self-concept to the "new" bodily self was related to the strength of illusory ownership of the friend's body. Moreover, a subsequent memory test showed that personality traits rated during the friend-body-swap illusion were generally remembered worse than traits rated during the control conditions; importantly, however, this impairment of episodic recognition memory was reduced for the participants who considerably adjusted their self-concept during the illusory body swapping. These findings demonstrate that our beliefs about own personality are dynamically shaped by the perception of our body and that coherence between the bodily and conceptual self-representations is important for the normal encoding of episodic memories.

Fluidity of gender identity induced by illusory body-sex change

Gender identity is a collection of thoughts and feelings about one’s own gender, which may or may not correspond to the sex assigned at birth. How this sense is linked to the perception of one’s own masculine or feminine body remains unclear. Here, in a series of three behavioral experiments conducted on a large group of control volunteers (N = 140), we show that a perceptual illusion of having the opposite-sex body is associated with a shift toward a more balanced identification with both genders and less gender-stereotypical beliefs about own personality characteristics, as indicated by subjective reports and implicit behavioral measures. These findings demonstrate that the ongoing perception of one’s own body affects the sense of one’s own gender in a dynamic, robust, and automatic manner.

A Continuous Illusion of Having a Sixth Finger

Our body is central to our sense of self and personal identity, yet it can be manipulated in the laboratory in surprisingly easy ways. Several multisensory illusions have shown the flexibility of the mental representation of our bodies by inducing the illusion of owning an artificial body part or having a body part with altered features. Recently, new studies showed we can embody additional body parts such as a supernumerary finger. Newport et al. recently reported a novel six-finger illusion using conflicting visual and tactile signals induced with the mirror box to create the illusory perception of having a sixth finger for a brief moment. In this study, we aimed to replicate this result and to investigate whether the experience of embodiment of a sixth finger could be prolonged for an extended duration by applying continuous visual-tactile stimulation. Results showed that a continuous illusion of having a sixth finger can be clearly induced. This shows that the six-finger illusion does not reflect merely a momentary confusion due to conflicting multisensory signals but can reflect an enduring representation of a supernumerary finger.

The Virtual Hand Illusion in Obesity: Dissociation Between Multisensory Interactions Supporting Illusory Experience and Self-Location Recalibration

The Rubber Hand Illusion (RHI) is used widely to investigate the multisensory integration mechanisms that support bodily self-consciousness and, more specifically, body ownership and self-location. It has been reported that individuals affected by obesity show anomalous multisensory integration processes. We propose that these obesity-induced changes could lead to an unusual susceptibility to the RHI and anomalous bodily self-experience. To test this hypothesis, we administered a modified version of the RHI (using a picture of the participant's hand) to individuals affected by obesity and participants with a healthy weight. During synchronous and asynchronous stimulation, we compared the subjective experience of the illusion (using a questionnaire) and the effect of the illusion on self-location (i.e., proprioceptive drift). In accordance with the illusion phenomenology, both groups had a comparable subjective illusory experience after the synchronous stimulation. Nevertheless, individuals affected by obesity showed less recalibration of self-location than healthy weight participants. In light of a recent interpretation of the multisensory integration mechanisms that underpin the RHI, our findings suggest that in obesity visuo-tactile integration supporting the subjective experience of the illusion is preserved, whereas visuo-proprioceptive integration for self-location is reduced.

Gulliver's virtual travels: active embodiment in extreme body sizes for modulating our body representations

It is noted that the perceptual experience of body and space can be modulated by changing the action capabilities or by manipulating the perceived body dimensions through a multisensory stimulation. This study adds to pre-existing literature by investigating the alterations in bodily experience following embodiment to both enlarged and shrunked bodies, while participants actively navigated in a virtual environment. A normal-sized body served as a reference condition. After each embodied navigation, participants estimated the height and width of three different body parts. Results revealed that the embodiment over shrunked body induced a significant reduction in participants' body image, while no changes were reported after the embodiment over the enlarged body. Findings were discussed in terms of previous literature exploring the constraints implicated in the ownership over different bodies.

Building the bodily self-awareness: Evidence for the convergence between interoceptive and exteroceptive information in a multilevel kernel density analysis study

Exteroceptive and interoceptive signals shape and sustain the bodily self-awareness. The existence of a set of brain areas, supporting the integration of information coming from the inside and the outside of the body in building the sense of bodily self-awareness has been postulated, yet the evidence remains limited, a matter of discussion never assessed quantitatively. With the aim of unrevealing where in the brain interoceptive and exteroceptive signals may converge, we performed a meta-analysis on imaging studies of the sense of body ownership, modulated by external visuotactile stimulation, and studies on interoception, which involves the self-awareness for internal bodily sensations. Using a multilevel kernel density analysis, we found that processing of stimuli of the two domains converges primarily in the supramarginal gyrus bilaterally. Furthermore, we found a right-lateralized set of areas, including the precentral and postcentral, and superior temporal gyri. We discuss these results and propose this set of areas as ideal candidates to match multiple body-related signals contributing to the creation of a multidimensional representation of the bodily self.

Characterizing Body Image Distortion and Bodily Self-Plasticity in Anorexia Nervosa via Visuo-Tactile Stimulation in Virtual Reality

We combined virtual reality and multisensory bodily illusion with the aim to characterize and reduce the perceptual (body overestimation) and the cognitive-emotional (body dissatisfaction) components of body image distortion (BID) in anorexia nervosa (AN). For each participant (20 anorexics, 20 healthy controls) we built personalized avatars that reproduced their own body size, shape, and verisimilar increases and losses of their original weight. Body overestimation and dissatisfaction were measured by asking participants to choose the avatar that best resembled their real and ideal body. Results show higher body dissatisfaction in AN, caused by the desire of a thinner body, and no body-size overestimation. Interpersonal multisensory stimulation (IMS) was then applied on the avatar reproducing participant’s perceived body, and on the two avatars which reproduced increases and losses of 15% of it, all presented with a first-person perspective (1PP). Embodiment was stronger after synchronous IMS in both groups, but did not reduce BID in participants with AN. Interestingly, anorexics reported more negative emotions after embodying the fattest avatar, which scaled with symptoms severity. Overall, our findings suggest that the cognitive-emotional, more than the perceptual component of BID is severely altered in AN and that perspective (1PP vs. 3PP) from which a body is evaluated may play a crucial role. Future research and clinical trials might take advantage of virtual reality to reduce the emotional distress related to body dissatisfaction.

A New Theory of Gender Dysphoria Incorporating the Distress, Social Behavioral, and Body-Ownership Networks

When postmortem studies related to transgender individuals were first published, little was known about the function of the various identified nuclei. Now, over 2 decades later, significant progress has been made associating function with specific brain regions, as well as in identifying networks associated with groups of behaviors. However, much of this progress has not been integrated into the general conceptualization of gender dysphoria in humans.

When postmortem studies related to transgender individuals were first published, little was known about the function of the various identified nuclei. Now, over 2 decades later, significant progress has been made associating function with specific brain regions, as well as in identifying networks associated with groups of behaviors. However, much of this progress has not been integrated into the general conceptualization of gender dysphoria in humans. I hypothesize that in individuals with gender dysphoria, the aspects of chronic distress, gender atypical behavior, and incongruence between perception of gender identity and external primary sex characteristics are all directly related to functional differences in associated brain networks. I evaluated previously published neuroscience data related to these aspects and the associated functional networks, along with other relevant information. I find that the brain networks that give individuals their ownership of body parts, that influence gender typical behavior, and that are involved in chronic distress are different in individuals with and without gender dysphoria, leading to a new theory—that gender dysphoria is a sensory perception condition, an alteration in the sense of gender influenced by the reflexive behavioral responses associated with each of these networks. This theory builds upon previous work that supports the relevance of the body-ownership network and that questions the relevance of cerebral sexual dimorphism in regard to gender dysphoria. However, my theory uses a hierarchical executive function model to incorporate multiple reflexive factors (body ownership, gender typical/atypical behavior, and chronic distress) with the cognitive, reflective process of gender identity.

Investigating the Components of Body Image Disturbance Within Eating Disorders

Body image disturbance has been highlighted as a common characteristic within the development and maintenance of clinical eating disorders (EDs), represented by alterations in an individual's bodily experience. However, whilst the perceptual stability of the sense of body ownership has been investigated in ED patients, the stability of the sense of body agency in those with ED is yet to be examined. Therefore, body ownership and body agency were investigated using the moving rubber hand illusion, alongside measures of explicit and implicit body satisfaction. Furthermore, with evidence demonstrating a direct link between perceptual and cognitive-affective components of body image in the healthy population, the relationship between measures of body perception and body satisfaction was investigated. Results showed that both ED and healthy individuals displayed a similar subjective experience of illusory ownership and agency towards the fake hand, following voluntary movement. However, whilst both groups initially overestimated their own hand width prior to the illusion, the ED group displayed a significant reduction in hand size estimation following the illusion, which was not matched to the same degree in healthy individuals. In addition, ED individuals displayed a significantly lower body satisfaction compared with healthy females, on both an explicit and implicit level. Such implicit outcomes were shown to be driven specifically by a weaker association between the self and attractiveness. Finally, a significant relationship was observed between specific perceptual measures and implicit body satisfaction, which highlights the important link between perceptual and cognitive-affective components of one's body image. Together, such findings provide a useful foundation for further research to study the conditions in which these two components relate with regard to body image and its disturbance, particularly in relation to the prognosis and treatment of EDs.

Barbie's new look: Exploring cognitive body representation among female children and adolescents

The original Barbie doll’s unrealistic body shape can negatively affect young girls’ body image. Mattel produced new Barbie dolls with “tall”, “curvy”, and “petite” body types, yet how girls perceive and evaluate the three new Barbie body types remains unknown. This study investigated whether young girls engage in an automatic “self-other matching” process when viewing the different Barbie doll representations. Female children and adolescents (N = 38; M_age = 10; 6–14 years old; SD = 2.24 years) completed a body-part compatibility task to provide an index of how they implicitly relate cognitive representations of their own body to the different doll images. Significant (p < .05) body-part compatibility effects emerged for the original, curvy and petite dolls, but not for the tall Barbie. These findings indicate that girls engage in a self-other body matching process when viewing Barbie, but that the strength of this matching is influenced by the doll’s body type. Results provide new evidence on the underlying cognitive mechanisms that occur when girls are exposed to physique-salient toys, and may have implications for young girls’ body image development and use of appearance-based social comparisons.

Affective judgement of social touch on a hand associated with hand embodiment

Social touch constitutes a critical component of human interactions. A gentle tap on the hand, for instance, can sometimes create emotional bonding and reduce interpersonal distance in social interactions. Evidence of tactile empathy suggests that touch can be experienced through both physical sensation and observation, yet vicarious perception of observed touch on an object as a function of the object’s conceptual representation (e.g., Is this object identified as mine? Does this object feel like part of me?) remains less explored. Here we examined the affective judgement of social touch when the illusory sense of ownership over a dummy hand was manipulated through the rubber-hand illusion. When the same social touch was performed on either the real or the dummy hand, we found a similar sense of perceived pleasantness between the felt and observed touch, but only when the dummy hand was embodied; when it was not, the perceived pleasantness of the observed touch was lesser (an “embodiment effect”; Experiment 1). In addition, we found that the embodiment effect associated with the observed touch was insensitive to the way in which embodiment was manipulated (Experiment 2), and that this effect was specific to social but not neutral touch (Experiment 3). Taken together, our findings suggest a role of embodiment in the affective component of observed social touch and contribute to our understanding of tactile empathy for objects.

The effect of intranasal oxytocin on the perception of affective touch and multisensory integration in anorexia nervosa: protocol for a double-blind placebo-controlled crossover study

INTRODUCTION

Anorexia nervosa (AN) is an eating disorder characterised by restriction of energy intake, fears of gaining weight and related body image disturbances. The oxytocinergic system has been proposed as a pathophysiological candidate for AN. Oxytocin is a neuropeptide involved in bodily processes (eg, breast feeding) and in the onset of social behaviours (eg, bonding). Studies investigating the effect of intranasal oxytocin (IN-OT) in AN showed that it can improve attentional bias for high-calorie food and fat bodies stimuli, and related stress. However, less is known about the effect of IN-OT on bodily awareness and body image distortions, key features of the disorder linked to its development, prognosis and maintenance. Here, we aim to investigate the effect of IN-OT on the perception of affective, C-tactile-optimal touch, known to be impaired in AN and on multisensory integration processes underlying a body ownership illusion (ie, rubber hand illusion). For exploratory purposes, we will also investigate the effect of IN-OT on another interoceptive modality, namely cardiac awareness and its relationship with affective touch.

DESIGN, METHODS AND ANALYSIS

Forty women with AN and forty matched healthy controls will be recruited and tested in two separate sessions; self-administering IN-OT (40 IU) or placebo, intranasally, in a pseudo-randomised manner. The data from this double-blind, placebo-controlled, cross-over study will be analysed using linear mixed models that allow the use of both fixed (treatment levels) and random (subjects) effects in the same analysis. To address our main hypotheses, separate analyses will be run for the affective touch task, where the primary outcome dependent variable will be the pleasantness of the touch, and for the rubber hand illusion, where we will investigate multisensory integration quantified as subjective embodiment towards the rubber hand. In the latter, we will manipulate the synchronicity of touch and the size of the hand.

ETHICS AND DISSEMINATION

Ethics approval has been obtained by National Research Ethics Service NRES Committee London (Queen's Square Committee, ref number 14/LO/1593). The results will be disseminated through conference presentations and publication in peer-reviewed journals.

The Effect of Visual Capture Towards Subjective Embodiment Within the Full Body Illusion

Typically, multisensory illusion paradigms emphasise the importance of synchronous visuotactile integration to induce subjective embodiment towards another body. However, the extent to which embodiment is due to the 'visual capture' of congruent visuoproprioceptive information alone remains unclear. Thus, across two experiments (total N = 80), we investigated how mere visual observation of a mannequin body, viewed from a first-person perspective, influenced subjective embodiment independently from concomitant visuotactile integration. Moreover, we investigated whether slow, affective touch on participants' own, unseen body (without concomitant touch on the seen mannequin) disrupted visual capture effects to a greater degree than fast, non-affective touch. In total, 40% of participants experienced subjective embodiment towards the mannequin body following mere visual observation, and this effect was significantly higher than conditions which included touch to participants own, unseen body. The velocity of the touch that participants received (affective/non-affective) did not differ in modulating visual capture effects. Furthermore, the effects of visual capture and perceived pleasantness of touch was not modulated by subthreshold eating disorder psychopathology. Overall, this study suggests that congruent visuoproprioceptive cues can be sufficient to induce subjective embodiment of a whole body, in the absence of visuotactile integration and beyond mere confabulatory responses.

Distorted body image influences body schema in individuals with negative bodily attitudes

There is now a considerable body of evidence to suggest that internal representations of the body can be meaningfully separated into at least two general levels; body image as a perceptual construct and body schema as a motor metric. However, recent studies with eating disordered individuals have suggested that there may in fact be more interaction between these two representations than first thought. We aimed to investigate how body image might act to influence body schema within a typical, healthy population. 100 healthy adult women were asked to judge the smallest gap between a pair of sliding doors that they could just pass through. We then determined whether these estimates were sufficient to predict the size of the smallest gap that they could actually pass through, or whether perceptual and attitudinal body image information was required in order to make these predictions. It was found that perceptual body image did indeed mediate performance on the egocentric (but not allocentric) motor imagery affordance task, but only for those individuals with raised body image concerns and low self-esteem; body schema was influenced by both the perceptual and attitudinal components of body image in those with more negative bodily attitudes. Furthermore, disparities between perceived versus actual size were associated with body parts that had larger variations in adipose/muscle-dependent circumference. We therefore suggest that it may be the affective salience of a distorted body representation that mediates the degree to which it is incorporated into the current body state.

Neuroscience of Virtual Reality: From Virtual Exposure to Embodied Medicine

Is virtual reality (VR) already a reality in behavioral health? To answer this question, a meta-review was conducted to assess the meta-analyses and systematic and narrative reviews published in this field in the last twenty-two months. Twenty-five different articles demonstrated the clinical potential of this technology in both the diagnosis and the treatment of mental health disorders: VR compares favorably to existing treatments in anxiety disorders, eating and weight disorders, and pain management, with long-term effects that generalize to the real world. But why is VR so effective? Here, the following answer is suggested: VR shares with the brain the same basic mechanism: embodied simulations. According to neuroscience, to regulate and control the body in the world effectively, the brain creates an embodied simulation of the body in the world used to represent and predict actions, concepts, and emotions. VR works in a similar way: the VR experience tries to predict the sensory consequences of an individual's movements, providing to him/her the same scene he/she will see in the real world. To achieve this, the VR system, like the brain, maintains a model (simulation) of the body and the space around it. If the presence in the body is the outcome of different embodied simulations, concepts are embodied simulations, and VR is an embodied technology, this suggests a new clinical approach discussed in this article: the possibility of altering the experience of the body and facilitating cognitive modeling/change by designing targeted virtual environments able to simulate both the external and the internal world/body.