The two dimensions of the body representation in women suffering from Anorexia Nervosa

Preserved tactile distance estimation despite body representation distortions in individuals with fibromyalgia

Our mental representation of our body depends on integrating various sensory modalities, such as tactile information. In tactile distance estimation (TDE) tasks, participants must estimate the distance between two tactile tips applied to their skin. This measure of tactile perception has been linked to body representation assessments. Studies in individuals with fibromyalgia (FM), a chronic widespread pain syndrome, suggest the presence of body representation distortions and tactile alterations, but TDE has never been examined in this population. Twenty participants with FM and 24 pain-free controls performed a TDE task on three Body regions (upper limb, trunk, lower limb), in which they manually estimated the interstimuli distance on a tablet. TDE error, the absolute difference between the estimation and the interstimuli distance, was not different between the Groups, on any Body region. Drawings of their body as they felt it revealed clear and frequent distortions of body representation in the group with FM, compared to negligible perturbations in controls. This contrast between distorted body drawings and unaltered TDE suggests a preserved integration of tactile information but an altered integration of this information with other sensory modalities to generate a precise and accurate body representation. Future research should investigate the relative contribution of each sensory information and prior knowledge about the body in body representation in individuals with FM to shed light on the observed distortions.

The characteristics of the implicit body model of the trunk

Knowing where the body is in space requires reference to a stored model of the size and shape of body parts, termed the body model. This study sought to investigate the characteristics of the implicit body model of the trunk by assessing the position sense of midline and lateral body landmarks. Sixty-nine healthy participants localised midline and lateral body landmarks on their thorax, waist and hips, with perceived positions of these landmarks compared to actual positions. This study demonstrates evidence of a significant distortion of the implicit body model of the trunk, presenting as a squatter trunk, wider at the waist and hips. A significant difference was found between perceived and actual location in the horizontal (x) and vertical (y) directions for the majority of trunk landmarks. Evidence of a rightward bias was noted in the perception of six of the nine body landmarks in the horizontal (x) direction, including all midline levels. In the vertical (y) direction, a substantial inferior bias was evident at the thorax and waist. The implicit body model of the trunk is shown to be distorted, with the lumbar spine (waist-to-hip region) held to be shorter and wider than reality.

The impact of weight and negative body image on the body schema in undergraduate women

BACKGROUND AND OBJECTIVES

Alterations of the sensory-motor body schema question the origins of such distortions. For example, in anorexia nervosa where patients think they are broader than they really are (body image) but act as if it was really the case (body schema). To date, the results of studies about what hinders the updating of the body schema so much (weight, body image) have been contradictory.

METHODS

We therefore conducted two studies that aimed to assess the impact of weight and body image problems on body schema in 92 young women without anorexia nervosa. For this purpose, we used a new body schema assessment tool (SKIN) that is sensitive enough to detect fine alterations of body schema in seven different body parts.

RESULTS

In Study 1, the thinness or overweight of the young women had a major impact on their tactile perception, especially because the assessed body part was a sensitive area for body dissatisfaction in young women (e.g., belly, thigh). In Study 2, the level of body dissatisfaction of the participants in its attitudinal and perceptual dimension also had a negative impact on their body schema, again in interaction with weight and body part.

CONCLUSIONS

These results imply that body dissatisfaction and thinness are predictors of massive body schema distortions. An oversized body schema could maintain various weight-control behaviors, thus risking the development, maintenance, or relapse of an eating disorder.

From symptoms to subjective and bodily experiences: the contribution of the Psychodynamic Diagnostic Manual (PDM-2) to diagnosis and treatment monitoring in eating disorders

PURPOSE

Atheoretical and descriptive conceptualizations of eating disorders (EDs) have faced substantial criticism due to their limited ability to assess patients' subjective characteristics and experiences, as needed to determine the most appropriate treatment options. The present article provides an overview of the clinical and empirical literature supporting the potential contribution of the Psychodynamic Diagnostic Manual (PDM-2) to both diagnostic assessment and treatment monitoring.

METHODS

Following a discussion of the most relevant shortcomings of current diagnostic models of EDs and a description of the rationale and structure of the PDM-2, evidence supporting the core PDM-2 dimensions of ED patients' subjective experiences (i.e., affective states, cognitive processes, relational patterns, somatic/bodily experiences and states) are examined, alongside their relevance to ED diagnosis and treatment.

RESULTS

Overall, the reviewed studies support the diagnostic importance of these patterns of subjective experiences in EDs, highlighting their potential role as either predisposing or maintaining factors to target in psychotherapy. A growing body of multidisciplinary evidence also shows that bodily and somatic experiences are central to the diagnosis and clinical management of ED patients. Moreover, there is evidence that a PDM-based assessment may enable closer monitoring of patient progress during treatment, with regard to both subjective experiences and symptom patterns.

CONCLUSIONS

The study suggests that current diagnostic frameworks for EDs would benefit from the addition of a person-centered perspective that considers not only symptoms, but also patients' full range of functioning-including their deep and surface-level emotional, cognitive, interpersonal, and social patterns-to improve patient-tailored interventions.

LEVEL OF EVIDENCE

Level V, narrative review.

Altered processing of conflicting body representations in women with restrictive anorexia nervosa

Cognitive and affective impairments in processing body image have been observed in patients with Anorexia Nervosa (AN) and may induce the hypercontrolled and regulative behaviors observed in this disorder. Here, we aimed to probe the link between activation of body representations and cognitive control by investigating the ability to resolve body-related representational conflicts in women with restrictive AN and matched healthy controls (HC). Participants performed a modified version of the Flanker task in which underweight and overweight body images were presented as targets and distractors; a classic version of the task, with letters, was also administered as a control. The findings indicated that performance was better among the HC group in the task with bodies compared to the task with letters; however, no such facilitation was observed in AN patients, whose overall performance was poorer than that of the HC group in both tasks. In the task with body stimuli, performance among patients with AN was the worst on trials presenting underweight targets with overweight bodies as flankers. These results may reflect a dysfunctional association between the processing of body-related representations and cognitive control mechanisms that may aid clinicians in the development of optimal individualized treatments.

From Virtual Reality to Regenerative Virtual Therapy: Some Insights from a Systematic Review Exploring Inner Body Perception in Anorexia and Bulimia Nervosa

Despite advances in our understanding of the behavioral and molecular factors that underlie the onset and maintenance of Eating Disorders (EDs), it is still necessary to optimize treatment strategies and establish their efficacy. In this context, over the past 25 years, Virtual Reality (VR) has provided creative treatments for a variety of ED symptoms, including body dissatisfaction, craving, and negative emotions. Recently, different researchers suggested that EDs may reflect a broader impairment in multisensory body integration, and a particular VR technique-VR body swapping-has been used to repair it, but with limited clinical results. In this paper, we use the results of a systematic review employing PRISMA guidelines that explore inner body perception in EDs (21 studies included), with the ultimate goal to analyze the features of multisensory impairment associated with this clinical condition and provide possible solutions. Deficits in interoception, proprioception, and vestibular signals were observed across Anorexia and Bulimia Nervosa, suggesting that: (a) alteration of inner body perception might be a crucial feature of EDs, even if further research is needed and; (b) VR, to be effective with these patients, has to simulate/modify both the external and the internal body. Following this outcome, we introduce a new therapeutic approach-Regenerative Virtual Therapy-that integrates VR with different technologies and clinical strategies to regenerate a faulty bodily experience by stimulating the multisensory brain mechanisms and promoting self-regenerative processes within the brain itself.

Assess and rehabilitate body representations via (neuro)robotics: An emergent perspective

The perceptions of our own body (e.g., size and shape) do not always coincide with its real characteristics (e.g., dimension). To track the complexity of our perception, the concept of mental representations (model) of the body has been conceived. Body representations (BRs) are stored in the brain and are maintained and updated through multiple sensory information. Despite being altered in different clinical conditions and being tightly linked with self-consciousness, which is one of the most astonishing features of the human mind, the BRs and, especially, the underlying mechanisms and functions are still unclear. In this vein, here we suggest that (neuro)robotics can make an important contribution to the study of BRs. The first section of the study highlights the potential impact of robotics devices in investigating BRs. Far to be exhaustive, we illustrate major examples of its possible exploitation to further improve the assessment of motor, haptic, and multisensory information building up the BRs. In the second section, we review the main evidence showing the contribution of neurorobotics-based (multi)sensory stimulation in reducing BRs distortions in various clinical conditions (e.g., stroke, amputees). The present study illustrates an emergent multidisciplinary perspective combining the neuroscience of BRs and (neuro)robotics to understand and modulate the perception and experience of one's own body. We suggest that (neuro)robotics can enhance the study of BRs by improving experimental rigor and introducing new experimental conditions. Furthermore, it might pave the way for the rehabilitation of altered body perceptions.

Waiting longer, feeling fatter: Effects of response delay on tactile distance estimation and confidence in females with anorexia nervosa

BACKGROUND

Research suggests that patients with anorexia nervosa (AN) exhibit differences in the perceptual processing of their own bodies. However, some researchers suggest that these differences are better explained with reference to non-perceptual factors, such as demand characteristics or emotional responses to the task. In this study, we investigated whether overestimation of tactile distances in participants with AN results from differences in tactile processing or non-perceptual factors, by measuring the role of allowed response time in an adapted version of the tactile distance estimation task (TDE-D). We further investigated the relationship between allowed response time and participants' confidence in their tactile judgments.

METHOD

Our sample consisted of females: participants with AN (n = 30), recovered (REC) participants (n = 29) and healthy controls (HC) (n = 31). Participants were asked to estimate tactile distances presented on the skin of either a salient (abdomen) or non-salient (arm) body part, either directly after stimulus presentation (direct condition) or after a 5 s delay (delayed condition). Confidence of estimation accuracy was measured after each response.

RESULTS

Results showed that allowing AN and REC more time to respond caused them to estimate tactile distances as larger. Additionally, participants with AN became less confident when given more time to respond.

CONCLUSIONS

These results suggest that non-perceptual influences cause participants with AN to increase their estimates of tactile distances and become less certain of these estimates. We speculate that previous findings-where participants with AN estimate tactile distances as larger than HC-may be due to non-perceptual differences.

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.

Self-perception in anorexia nervosa: When the body becomes an object

OBJECTIVE

Women with anorexia nervosa (AN) act as if they have a larger body, as evidenced in obstacle avoidance tasks, where an allocentric perspective is adopted. This alteration emerges not only when they perform, but also when they imagine movements. However, no previous study has investigated own body centered tasks. As such, in this study we aim at documenting if women with AN show an altered behaviour also when the task requires a first-person perspective.

METHOD

We explored the performance of eleven woman affected by AN compared to eighteen matched controls, in two motor imagery tasks based on a self-frame of reference, the Hand Laterality Task and the Mental Motor Chronometry Task. Moreover, two control tasks relative to visual imagery were administered.

RESULTS

In the Hand Laterality Task, affected participants did not adopt a motor strategy to judge hands laterality (i.e. no biomechanical constraints effect). Crucially, they also showed an altered behavior in the control task. Similarly, they did not show the expected isochrony in the Mental Motor Chronometry Task, when actions pertained the left (but not the right) hand, in absence of any difference in the control task.

CONCLUSIONS

Our findings reveal altered imagery processes in AN. Specifically, affected participants adopt a third-person, rather than a first-person perspective, even when the task requires to imagine their own body in an internal frame of reference. In other words, participants with AN objectify body stimuli. Different mechanisms (i.e., checking behaviour; mirror self-reflection; altered multisensory integration) can explain such an altered imagery in AN.

No evidence for sex differences in tactile distance anisotropy

Perceptual illusions of the distance between two touches have been used to study mental representations of the body since E. H. Weber's classic studies in the nineteenth century. For example, on many body parts tactile distance is anisotropic, with distances aligned with body width being perceived as larger than distances aligned with body length on several skin regions. Recent work has demonstrated sex differences in other distortions of mental body representations, such as proprioceptive hand maps. Given such findings, I analysed the results of 24 experiments, conducted by myself and my colleagues, measuring tactile distance anisotropy on the hand dorsum in both women and men. The results showed clear, and highly consistent anisotropy in both women and men, with no evidence for any sex difference.

Self-body recognition and attitudes towards body image in younger and older women

Despite the fact that ageing causes dramatic changes in bodily appearance, little is known about how self-body recognition changes across life span. Here, we investigated whether older, compared to younger women, differed in the ability of recognising their own than other women's body parts and whether this effect was associated to negative body image dispositions. Twenty-eight young (M_age: 25.93 years, SD_age = 4.74) and 25 middle-aged (M_age: 54.36 years, SD_age = 4.54) women completed an implicit task consisting of visual matching of self and others' body parts and an explicit self-other body discrimination task. Stimuli comprised of images of body parts of the participant and of other age- and BMI-matched models, which were presented in the original size or modified to look rounder or thinner. Measures of adiposity (i.e. BMI), body image concerns and appearance-related worries for specific body parts and for the whole body were also collected. Whilst both groups showed a self-body advantage in the implicit, but not in the explicit task, the advantage was notably bigger for the younger group. However, the implicit self-advantage was higher in those middle-aged women that displayed more body image concerns and worries for specific body parts. Furthermore, the two groups were comparably less able in recognising their body parts when presented thinner as compared to rounder or in their actual size. Overall, these findings open the possibility that, as women age, their implicit self-recognition abilities may decline in association with more negative body image dispositions.

Affective touch topography and body image

Recent evidence suggests that altered responses to affective touch—a pleasant interoceptive stimulus associated with activation of the C-Tactile (CT) system—may contribute to the aetiology and maintenance of mental conditions characterised by body image disturbances (e.g., Anorexia Nervosa). Here, we investigated whether tactile pleasantness and intensity differ across body sites, and if individual differences in dysmorphic appearance concerns and body and emotional awareness might be associated with touch perceptions across body sites. To this end, we measured perceived pleasantness and intensity of gentle, dynamic stroking touches applied to the palm, forearm, face, abdomen and back of 30 female participants (mean age: 25.87±1.17yrs) using CT-optimal (3 cm/s) and non-CT optimal (0.3 and 30 cm/s) stroking touch. As expected, participants rated CT-targeted touch as more pleasant compared to the two non-CT optimal stroking touch at all body sites. Regardless of stroking velocity, touch applied to the abdomen elicited the lowest pleasantness ratings. Lower levels of emotional awareness, greater levels of interoceptive sensibility and of dysmorphic concerns were associated with lower preference for CT-optimal stroking touch applied to the forearm and the back. These findings begin to elucidate the link between CT sensitivity, dysmorphic appearance concerns and body and emotional awareness, which may have implications for future research looking to inform early interventions. Addressing impaired processing of affective interoceptive stimuli, such as CT-targeted touch, may be the key to current treatment approaches available for those populations at risk of disorders characterised by body image disturbance.

Visual Self-Misperception in Eating Disorders

Many who suffer from eating disorders claim that they see themselves as "fat". Despite decades of research into the phenomenon, behavioural evidence has failed to confirm that eating disorders involve visual misperception of own-body size. I illustrate the importance of this phenomenon for our understanding of perceptual processing, outline the challenges involved in experimentally confirming it, and provide solutions to those challenges.

Tactile distance anisotropy on the feet

Perception of distance between two touches varies with orientation on the hand, with distances aligned with hand width perceived as larger than those aligned with hand length. Similar anisotropies are found on other body parts (e.g., the face), suggesting they may reflect a general feature of tactile organization, but appear absent on other body parts (e.g., the belly). Here, we investigated tactile-distance anisotropy on the foot, a body part structurally and embryologically similar to the hand, but with very different patterns of functional usage in humans. In three experiments, we compared the perceived distance between pairs of touches aligned with the medio-lateral and proximal-distal foot axes. On the hairy skin of the foot dorsum, anisotropy was consistently found, with distances aligned with the medio-lateral foot axis perceived as larger than those in the proximo-distal axis. In contrast, on the glabrous skin of the sole, inconsistent results were found across experiments, with no overall evidence for anisotropy. This shows a pattern of anisotropy on the foot broadly similar to that on the hand, adding to the list of body parts showing tactile-distance anisotropy, and providing further evidence that such biases are a general aspect of tactile spatial organization across the body. Significance: The perception of tactile distance has been widely used to understand the spatial structure of touch. On the hand, anisotropy of tactile distance perception is well established, with distances oriented across hand width perceived larger than those oriented along hand length. We investigated tactile-distance anisotropy on the feet, a body part structurally, genetically, and developmentally homologous to the hands, but with strikingly different patterns of functional usage. We report highly similar patterns of anisotropy on the hairy skin of the hand dorsum and foot dorsum. This suggests that anisotropy arises from the general organization of touch across the body.

Perception of Tactile Distance on the Back

The perceived distance between two touches is anisotropic on many parts of the body. Generally, tactile distances oriented across body width are perceived as larger than distances oriented along body length, though the magnitude of such biases differs substantially across the body. In this study, we investigated tactile distance perception on the back. Participants made verbal estimates of the perceived distance between pairs of touches oriented either across body width or along body length on (a) the left hand, (b) the left upper back, and (c) the left lower back. There were clear tactile distance anisotropies on the hand and upper back, with distances oriented across body width overestimated relative to those along body length/height, consistent with previous results. On the lower back, however, an anisotropy in exactly the opposite direction was found. These results provide further evidence that tactile distance anisotropies vary systematically across the body and suggest that the spatial representation of touch on the lower back may differ qualitatively from that on other regions of the body.

Visual body-size adaptation and estimation of tactile distance

Estimating the size of bodies is crucial for interactions with physical and social environments. Body-size perception is malleable and can be altered using visual adaptation paradigms. However, it is unclear whether such visual adaptation effects also transfer to other modalities and influence, for example, the perception of tactile distances. In this study, we employed a visual adaptation paradigm. Participants were exposed to images of expanded or contracted versions of self- or other-identity bodies. Before and after this adaptation, they were asked to manipulate the width of body stimuli to appear as 'normal' as possible. We replicated an effect of visual adaptation such that the body-size selected as most 'normal' was larger after exposure to expanded and thinner after exposure to contracted adaptation stimuli. In contrast, we did not find evidence that this adaptation effect transfers to distance estimates for paired tactile stimuli delivered to the abdomen. A Bayesian analysis showed that our data provide moderate evidence that there is no effect of visual body-size adaptation on the estimation of spatial parameters in a tactile task. This suggests that visual body-size adaptation effects do not transfer to somatosensory body-size representations.

Visual mapping of body image disturbance in anorexia nervosa reveals objective markers of illness severity

Body image disturbance (BID) is a core feature of eating disorders, for which there are few objective markers. We examined the feasibility of a novel digital tool, "Somatomap", to index BID related to anorexia nervosa (AN) severity. Fifty-five AN inpatients and 55 healthy comparisons (HC) outlined their body concerns on a 2-Dimensional avatar. Next, they indicated sizes/shapes of body parts for their current and ideal body using sliders on a 3-Dimensional avatar. Physical measurements of corresponding body parts, in cm, were collected for reference. We evaluated regional differences in BID using proportional z-scores to generate statistical body maps, and multivariate analysis of covariance to assess perceptual discrepancies for current body, ideal body, and body dissatisfaction. The AN group demonstrated greater regional perceptual inaccuracy for their current body than HC, greater discrepancies between their current and ideal body, and higher body dissatisfaction than HCs. AN body concerns localized disproportionately to the chest and lower abdomen. The number of body concerns and perceptual inaccuracy for individual body parts was strongly associated with Eating Disorder Examination Questionnaire (Global EDE-Q) scores across both groups. Somatomap demonstrated feasibility to capture multidimensional aspects of BID. Several implicit measures were significantly associated with illness severity, suggesting potential utility for identifying objective BID markers.

Body perception treatment, a possible way to treat body image disturbance in eating disorders: a case-control efficacy study

BACKGROUND

The body image disturbance (BID) is a common symptom in eating disorders, often observed and described in anorexia nervosa (AN) and bulimia nervosa (BN). Recently, this symptom has also been observed in binge eating disorder (BED). The research underlines that the BID presents three different altered components: affective, cognitive, and perceptual one. Current treatments for BID have mainly focused on the affective and cognitive components. Nowadays, the need emerges for treatments focused also on the perceptual component of the BID. In this paper, we present the results of an efficacy study on the body perception treatment (BPT), a new treatment for BID focused on the perceptual component of the disorder.

OBJECTIVE

We looked for an additional treatment effect on a protocol for ED inpatients to evaluate the efficacy of BPT. We performed the study through statistical analysis of admission and discharge scores.

METHODS

We conducted a case-control study in a hospital ward specialized in eating disorders. Two groups were identified: the control group (TAU; N = 91) and the experimental group (TAU + BPT; N = 91). The experimental group performed BTP activities in addition to the treatment at usual. All patients in both groups had an eating disorder diagnosis (AN, BN, BED and EDNOS/OSFED). Sampling occurred on a time basis and not by randomization. Moreover, all patients admitted in the ED hospital ward in the time frame considered (from end-2009 to mid-2017) were included in the study. BPT activities were introduced in mid-2013 and three psychometric instruments upon entry and discharge were used: Symptom Check List-90 (SCL-90) to measure the general psychopathological state; the Eating Disorder Inventory-3 (EDI-3) to estimate the incidence of personality traits strongly correlated to eating disorders; the body uneasiness test (BUT) to measure the body uneasiness. We performed a pre/post analysis for both groups; we studied the additional effect of the treatment through deltas analysis of the three questionnaires (Δ = assessment at discharge - assessment at the entrance). Data were analyzed using the Student T and the Wilcoxon rank-sum test.

RESULTS

The pre/post analysis showed statistically significant improvement in both conditions (TAU and TAU + BPT) in the general psychopathological state (SCL-90) and in the incidence of personality traits (EDI-3). Improvements in body uneasiness (BUT) were observed only in the experimental group (TAU + BPT). Furthermore, the analysis of the deltas shows more significant improvements in TAU + BPT compared to TAU in all the variables considered.

CONCLUSION

We found an additional effect of the BPT on TAU. The usual ED protocol added with BPT activities showed significantly better clinical results. We have interpreted these results in light of recent developments in the neuroscientific field of body image.

LEVEL OF EVIDENCE

Level II: controlled trial without randomization.

Visuo-tactile shape perception in women with Anorexia Nervosa and healthy women with and without body concerns

A key feature of Anorexia Nervosa is body image disturbances, the study of which has focused mainly on visual and attitudinal aspects, did not always contain homogeneous groups of patients, and/or did not evaluate body shape concerns of the control group. In this study, we used psychophysical methods to investigate the visual, tactile and bimodal perception of elliptical shapes in a group of patients with Anorexia Nervosa (AN) restricting type and two groups of healthy participants, which differed from each other by the presence of concerns about their own bodies. We used an experimental paradigm designed to test the hypothesis that the perceptual deficits in AN reflect an impairment in multisensory integration. The results showed that the discrimination thresholds of AN patients are larger than those of the two control groups. While all participants overestimated the width of the ellipses, this distortion was more pronounced in AN patients and, to a lesser extent, healthy women concerned about their bodies. All groups integrated visual and tactile information similarly in the bimodal conditions, which does not support the multi-modal integration impairment hypothesis. We interpret these results within an integrated model of perceptual deficits of Anorexia Nervosa based on a model of somatosensation that posits a link between object tactile perception and Mental Body Representations. Finally, we found that the participants' perceptual abilities were correlated with their clinical scores. This result should encourage further studies that aim at evaluating the potential of perceptual indexes as a tool to support clinical practices.

Anorexia nervosa and the size-weight illusion: No evidence of impaired visual-haptic object integration

Body image disorders in anorexia nervosa (AN) patients and recovered AN (RAN) patients have been suggested to stem from aberrant integration of sensory information. Previous research by Case et al. (2012) used the size-weight illusion (SWI) to study multisensory integration in AN. Their results showed a diminished SWI in AN patients, which they interpreted as evidence of decreased integration of visual and proprioceptive information. However, their method did not distinguish between visual and haptic size information, which was presented concurrently while making weight judgements. Therefore, the reported effect might be attributed to integrating visual, haptic size cues, or a combination of both processes with proprioceptive input. Here, we use the SWI to investigate the integration of visual and haptic object-related sensory information in a sample of AN patients (n = 30), RAN patients (n = 29) and healthy controls (HC) (n = 29). We aimed to distinguish the contribution of visual and haptic object size by including separate visual and haptic SWI conditions. In addition to explicit measures, we included grip force measurements to assess implicit expectations about object weight. We further analysed the correlation between the SWI and a visual body size estimation (VSE) task. In contrast to Case et al. (2012), we found no evidence of differential SWI experience between groups. All participants reported a stronger visual SWI compared to haptic SWI. Grip force rate (but not peak) showed evidence of motor adaptation for the larger object in the visual condition. Furthermore, there was no correlation between the VSE and SWI, indicating no relation between perceived object weight and body size estimation. These results do not support the hypothesised impairment of visual-haptic object related integration in AN.

Explicit and Implicit Own's Body and Space Perception in Painful Musculoskeletal Disorders and Rheumatic Diseases: A Systematic Scoping Review

Background: Pain and body perception are essentially two subjective mutually influencing experiences. However, in the field of musculoskeletal disorders and rheumatic diseases we lack of a comprehensive knowledge about the relationship between body perception dysfunctions and pain or disability. We systematically mapped the literature published about the topics of: (a) somatoperception; (b) body ownership; and (c) perception of space, analysing the relationship with pain and disability. The results were organized around the two main topics of the assessment and treatment of perceptual dysfunctions.

Methods: This scoping review followed the six-stage methodology suggested by Arksey and O'Malley. Ten electronic databases and grey literature were systematically searched. The PRISMA Extension for Scoping Reviews was used for reporting results. Two reviewers with different background, independently performed study screening and selection, and one author performed data extraction, that was checked by a second reviewer.

Results: Thirty-seven studies fulfilled the eligibility criteria. The majority of studies (68%) concerned the assessment methodology, and the remaining 32% investigated the effects of therapeutic interventions. Research designs, methodologies adopted, and settings varied considerably across studies. Evidence of distorted body experience were found mainly for explicit somatoperception, especially in studies adopting self-administered questionnaire and subjective measures, highlighting in some cases the presence of sub-groups with different perceptual features. Almost half of the intervention studies (42%) provided therapeutic approaches combining more than one perceptual task, or sensory-motor tasks together with perceptual strategies, thus it was difficult to estimate the relative effectiveness of each single therapeutic component.

Conclusions: To our knowledge, this is the first attempt to systematically map and summarize this research area in the field of musculoskeletal disorders and rheumatic diseases. Although methodological limitations limit the validity of the evidence obtained, some strategies of assessment tested and therapeutic strategies proposed represent useful starting points for future research. This review highlights preliminary evidence, strengths, and limitations of the literature published about the research questions, identifying key points that remain opened to be addressed, and make suggestions for future research studies. Body representation, as well as pain perception and treatment, can be better understood if an enlarged perspective including body and space perception is considered.

An Investigation of Lower Limb Representations Underlying Vision, Touch, and Proprioception in Body Integrity Identity Disorder

Individuals with Body Integrity Identity Disorder (BIID) have a (non-psychotic) longstanding desire to amputate or paralyze one or more fully-functioning limbs, often the legs. This desire presumably arises from experiencing a mismatch between one's perceived mental image of the body and the physical structural and/or functional boundaries of the body itself. While neuroimaging studies suggest a disturbed body representation network in individuals with BIID, few behavioral studies have looked at the manifestation of this disrupted lower limb representations in this population. Specifically, people with BIID feel like they are overcomplete in their current body. Perhaps sensory input, processed normally on and about the limb, cannot communicate with a higher-order model of the leg in the brain (which might be underdeveloped). We asked individuals who desire paralysis or amputation of the lower legs (and a group of age- and sex-matched controls) to make explicit and implicit judgments about the size and shape of their legs while relying on vision, touch, and proprioception. We hypothesized that BIID participants would mis-estimate the size of their affected leg(s) more than the same leg of controls. Using a multiple single-case analysis, we found no global differences in lower limb representations between BIID participants and controls. Thus, while people with BIID feel that part of the body is foreign, they can still make normal sensory-guided implicit and explicit judgments about the limb. Moreover, these results suggest that BIID is not a body image disorder, per se, and that an examination of leg representation does not uncover the disturbed bodily experience that individuals with BIID have.

The Dancers' Visuospatial Body Map Explains Their Enhanced Divergence in the Production of Motor Forms: Evidence in the Early Development

Dance represents an opportunity to promote not only motor skills but also other cognitive functions and general well-being. In this study, 58 children aged 6–10 years were enrolled in order to test the issue if dance improves divergent thinking in motor and visual domains (domain-general and domain-specificity hypotheses), and whether the topological map of the body mediates their performance at the motor task (mediation hypothesis). Therefore, 33 children practicing dance were compared with a control group (25 children). Children were administered the visual divergent thinking task of the Torrance Test of Creative Thinking, consisting in making drawings starting from given shapes, and the motor-form divergent thinking task, opportunely developed consisting in producing acted motor forms in the extrapersonal space. Both tasks were presented for 10 min and were scored in terms of fluency, flexibility, and originality. The ability to form the topological map of the body was measured by the frontal body-evocation test. Results revealed that children practicing dance outperformed the control group only in terms of the ability to perform motor forms. In addition, dancers showed a better topological map of the body, and, most importantly, besides the direct effect of group on the ability to produce acted motor forms, a significant indirect effect of the group, mediated by performances on frontal body-evocation task, was found. These results have important implications for cognition, showing that dance can improve the topological map of the body that in turn enhances creativity in motor domain since the early developmental age.

No evidence of tactile distance anisotropy on the belly

The perceived distance between two touches has been found to be larger for pairs of stimuli oriented across the width of the body than along the length of the body, for several body parts. Nevertheless, the magnitude of such biases varies from place to place, suggesting systematically different distortions of tactile space across the body. Several recent studies have investigated perceived tactile distance on the belly as an implicit measure of body perception in clinical conditions including anorexia nervosa and obesity. In this study, we investigated whether there is an anisotropy of perceived tactile distance on the belly in a sample of adult women. Participants made verbal estimates of the perceived distance between pairs of touches oriented either across body width or along body length on the belly and the dorsum of the left hand. Consistent with previous results, a large anisotropy was apparent on the hand, with across stimuli perceived as larger than along stimuli. In contrast, no such bias was apparent on the belly. These results provide further evidence that anisotropies of perceived tactile distance vary systematically across the body and suggest that there is no anisotropy at all on the belly in healthy women.

A Conceptual Model of Tactile Processing across Body Features of Size, Shape, Side, and Spatial Location

The processing of touch depends of multiple factors, such as the properties of the skin and type of receptors stimulated, as well as features related to the actual configuration and shape of the body itself. A large body of research has focused on the effect that the nature of the stimuli has on tactile processing. Less research, however, has focused on features beyond the nature of the touch. In this review, we focus on some features related to the body that have been investigated for less time and in a more fragmented way. These include the symmetrical quality of the two sides of the body, the postural configuration of the body, as well as the size and shape of different body parts. We will describe what we consider three key aspects: (1) how and at which stages tactile information is integrated between different parts and sides of the body; (2) how tactile signals are integrated with online and stored postural configurations of the body, regarded as priors; (3) and how tactile signals are integrated with representations of body size and shape. Here, we describe how these different body dimensions affect integration of tactile information as well as guide motor behavior by integrating them in a single model of tactile processing. We review a wide range of neuropsychological, neuroimaging, and neurophysiological data and suggest a revised model of tactile integration on the basis of the one proposed previously by Longo et al.

Abnormal brain processing of gentle touch in anorexia nervosa

Body image disturbance is a core symptom in anorexia nervosa (AN). Recent research suggests that abnormalities in touch perception may contribute to the disease mechanisms in AN. Here, we used functional magnetic resonance imaging (fMRI) to study possible abnormalities in cortical processing of affective touch in AN. Gentle skin strokes were applied to the right forearm during fMRI scanning in women diagnosed with AN (n = 25) and in matched healthy controls (HC; n = 25). Blocks of skin stroking were alternated with blocks of static skin indentation. Participants provided ratings of the pleasantness of skin stroking stimulation. AN participants perceived skin stroking as significantly less pleasant than HC. We observed no group differences for the contrast between skin stroking and skin indentation in primary tactile regions. We did find, however, significantly less activity in the AN group in areas including left caudate nucleus. Also, we found less activity in the AN group in bilateral lateral occipital cortex for the main effect of skin stroking. Our results suggest that abnormal functioning of the dorsal striatum could affect evaluation of pleasant tactile stimuli, and that abnormal functioning of the lateral occipital cortex might be related to disturbed body image perception.

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.

Women with Anorexia Nervosa do not show altered tactile localization compared to healthy controls

Body image disturbance is a key symptom of Anorexia Nervosa (AN). Previous studies found that women with AN overestimate their body size in comparison with healthy controls (HC), at least for unimodal measures involving either only visual input (e.g. distorted photographs technique) or only tactile input (e.g. tactile distance tasks). Distorted body representations are hypothesized to cause this misperception in AN. We here tested whether this overestimation remains present in a novel one-point-localization (OPL) task involving the mapping of a tactile stimulus onto a visual image. Two experiments compared the ability of 27 women with AN and 40 HC to accurately localize a tactile stimulus on a live image of their body. Women with AN and HC did not differ in their performance. Instead, participants in both groups showed systematic distortions in their localization performance. This study suggests that the mapping of a tactile stimulus does not involve a distorted body representation in women with AN compared to HC.

Feel the Time. Time Perception as a Function of Interoceptive Processing

The nature of time is rooted in our body. Constellations of impulses arising from the flesh constantly create our interoceptive perception and, in turn, the unfolding of these perceptions defines human awareness of time. This study explored the connection between time perception and interoception and proposes the Interoceptive Buffer saturation (IBs) index. IBs evaluates subjects’ ability to process salient stimuli from the body by measuring subjective distortions of interoceptive time perception, i.e., the estimated duration of tactile interoceptive stimulations. Thirty female healthy subjects were recruited through consecutive sampling and assessed for common variables related to interoceptive alterations: depressive symptoms (Beck Depression Inventory, BDI-II), eating disorders (EDI-3) risk, and anxiety levels (State Trait Anxiety Inventory, STAI). Interoceptive cardiac accuracy (IAc) was assessed as well. Subjects performed verbal time estimation of interoceptive stimuli (IBs) delivered using a specifically designed interoceptive tactile stimulator, as well as verbal time estimation of visual and auditory stimuli. Results showed that IBs index positively correlated with IAc, and negatively with EDI-3 Drive for Thinness (DT) risk subscale. Moreover, IBs index was positively predicted by IAc, and negatively predicted by DT and somatic factors of depression. Our results suggest that underestimations in interoceptive time perception are connected to different psychological conditions characterized by a diminished processing of high salience stimuli from the body. Conversely, overestimations of the duration of interoceptive stimuli appear to be function of subjects’ ability to correctly perceive their own bodily information. Evidence supported IBs index, fostering the concept of interoceptive treatments for clinical purposes.

An ecological approach to the behavioral assessment of executive functions in anorexia nervosa

The use of ecological tests to assess executive functions (EFs) in patients with anorexia nervosa (AN) has not examined extensively. The objective of this study was to analyze and compare the performance of patients with AN and healthy controls (HCs) on standard versus ecologically valid tests on EFs. Sixty-two females aged between 16 and 42 who were diagnosed with AN and 70 matched HCs completed 2 neuropsychological test batteries: standard tests (WCST, TMT, Stroop, ToL, fluency test) and the Behavioral Assessment of Dysexecutive Syndrome (BADS). On the standard tests, patients with AN produced more perseverative response and were slower than HCs in the TMT; in contrast, they scored as well as HCs on tasks that assessed categorization, interference in color naming, planning and semantic fluency. Conversely, there were differences in the ecological tests with patients with AN systematically slower in the resolution of complex tasks. Results demonstrated the power of ecological tests in capturing selective impairments in multifaceted and unstructured tests. Patients with AN experienced systematic deceleration in the resolution of ecological tasks. Also, the increased time needed to solve the tasks, was not reflected in overall improvement in performance. This evidence is further discussed with respect to central coherence.

The magic hand: Plasticity of mental hand representation

Internal spatial body configurations are crucial to successfully interact with the environment and to experience our body as a three-dimensional volumetric entity. These representations are highly malleable and are modulated by a multitude of afferent and motor information. Despite some studies reporting the impact of sensory and motor modulation on body representations, the long-term relationship between sensory information and mental representation of own body parts is still unclear. We investigated hand representation in a group of expert sleight-of-hand magicians and in a group of age-matched adults naïve to magic (controls). Participants were asked to localise landmarks of their fingers when their hand position was congruent with the mental representation (Experiment 1) and when proprioceptive information was “misleading” (Experiment 2). Magicians outperformed controls in both experiments, suggesting that extensive training in sleight of hand has a profound effect in refining hand representation. Moreover, the impact of training seems to have a high body-part specificity, with a maximum impact for those body sections used more prominently during the training. Interestingly, it seems that sleight-of-hand training can lead to a specific improvement of hand mental representation, which relies less on proprioceptive information.

Body representation disturbances in visual perception and affordance perception persist in eating disorder patients after completing treatment

Body image disturbances (BID) are a key feature of eating disorders (ED). Clinical experience shows that BID exists in patients who Completed their Eating Disorder Treatment (CEDT), however studies concerning BID in CEDT patients are often limited to cognition and affect, measured by interviews and questionnaires. The current study is the first systematic study investigating the full scope of the mental body representation, including bodily attitudes, visual perception of body size, tactile perception, and affordance perception in CEDT patients. ED patients (N = 22), CEDT patients (N = 39) and healthy controls (HC; N = 30) were compared on BID tasks including the Body Attitude Test (BAT), Visual Size Estimation (VSE), Tactile Estimation Task (TET), and Hoop Task (HT). Results on the BAT show higher scores for ED patients compared to CEDT patients and HC but no difference between CEDT patients and HC. Both ED and CEDT patients show larger overestimations on the VSE and HT compared to HC, where ED patients show the largest overestimations. No group differences were found on the TET. The results indicate the existence of disturbances in visual perception and affordance perception in CEDT patients. Research focussing on more effective treatments for ED addressing multiple (sensory) modalities is advised.

Dissatisfaction with own body makes patients with eating disorders more sensitive to pain

Body image represents a multidimensional concept including body image evaluation and perception of body appearance. Disturbances of body image perception are considered to be one of the central aspects of anorexia nervosa and bulimia nervosa. There is growing evidence that body image distortion can be associated with changes in pain perception. The aim of our study was to examine the associations between body image perception, body dissatisfaction, and nociception in women with eating disorders and age-matched healthy control women. We measured body dissatisfaction and pain sensitivity in 61 patients with Diagnostic and Statistical Manual of Mental Disorders-Fourth Edition diagnoses of eating disorders (31 anorexia nervosa and 30 bulimia nervosa) and in 30 healthy women. Thermal pain threshold latencies were evaluated using an analgesia meter and body image perception and body dissatisfaction were assessed using Anamorphic Micro software (digital pictures of their own body distorted into larger-body and thinner-body images). Patients with eating disorders overestimated their body size in comparison with healthy controls, but the two groups did not differ in body dissatisfaction. In anorexia and bulimia patient groups, body dissatisfaction (calculated in pixels as desired size/true image size) correlated with pain threshold latencies (r=0.55, p=0.001), while between body image perception (determined as estimation size/true image size) and pain threshold, no correlation was found. Thus, we demonstrated that in patients with eating disorders, pain perception is significantly associated with emotional contrary to sensory (visual) processing of one’s own body image. The more the patients desired to be thin, the more pain-sensitive they were. Our findings based on some shared mechanisms of body dissatisfaction and pain perception support the significance of negative emotions specific for eating disorders and contribute to better understanding of the psychosomatic characteristics of this spectrum of illnesses.

Body distortions in Anorexia Nervosa: Evidence for changed processing of multisensory bodily signals

Body size and shape distortion is a core feature of Anorexia Nervosa (AN) - patients experience their body as fat while objectively being very thin. The cause of this distortion is unclear and disturbances in body perception could be involved. Body perception comprises estimating shape and location of one's body and requires integrating multisensory signals. We investigated if and how body location perception is changed and tested 23 AN patients and 23 healthy controls (HC) in a Rubber Hand Illusion (RHI) reaching paradigm. We presented two types of multisensory conflicts (visual-proprioceptive hand location; visual-tactile touch synchrony) and tested if the impact of visual-proprioceptive and visual-tactile signals on hand location perception differs between AN and HC groups. We found significant group differences in shifts of reaching trajectories, indicating that the influence of proprioceptive signals on hand location estimates is reduced in AN. Hand location estimates were relatively more biased towards external visual information, and shorter illness durations predicted a larger visual bias. Although touch synchrony also significantly influenced hand location estimates, this effect did not differ between groups. Our findings provide compelling evidence that multisensory body location perception - specifically the processing of visual-proprioceptive signals - is changed in AN.