Brain activity elicited by viewing pictures of the own virtually amputated body predicts xenomelia

Ownership of the affected leg is further reduced following deceptive behaviors in body integrity dysphoria

Although predicted by the notion of embodied morality, it remains unknown whether a reduced sense of body ownership (SoO) is associated with increased or decreased dishonesty. To clarify this issue, we tested patients with body integrity dysphoria (BID), a clinical condition characterized by chronic reductions of SoO toward one leg that patients persistently desire to have amputated. Participants with BID played a card game in which they could voluntarily tell the truth or cheat an opponent, and thus either steal or give them money. To assess whether SoO toward the effector limb influences (im)moral decisions, responses were communicated with the affected or the unaffected leg. We found that a higher number of self-gain lies was followed by further reductions of SoO toward the affected leg. Our result supports the idea that reductions of SoO may follow immoral behaviors to distance from unwanted characteristics of the self, like one's own dishonesty.

Is this my foot? Experimentally induced disownership in individuals with body integrity dysphoria

In body integrity dysphoria (BID), otherwise healthy individuals feel like a part of their physical body does not belong to them despite normal sensorimotor functioning. Theoretical and empirical evidence suggested aweakened integration of the affected body part into higher-order multisensory cortical body networks. Here, we used a multisensory stimulation paradigm in mixed reality to modulate and investigate multisensory processing underlying body (dis)ownership in individuals with BID of the lower limb. In 20 participants with BID, delay perception and body ownership were measured after introducing delays between the visual and tactile information of viewed stroking applied to affected and unaffected body parts. Unlike predicted, delay perception did not differ between the two body parts. However, specifically for the affected limb, ownership was lower and more strongly modulated by delay. These findings might be following the idea of a stronger dependency on online bottom up sensory signals in BID.

Not my body, not my pain? Pain perception and placebo analgesia in individuals with body integrity dysphoria

Acute and chronic states of physical pain are inherently linked to our bodily perception. Bodily illusion paradigms have demonstrated that an experimentally induced sense of body disownership can modulate both acute and chronic pain. Insight into the relationship between enduring clinical alterations in body perception and pain is much more limited. The current study examined both pain perception and placebo analgesia in Body Integrity Dysphoria (BID), a clinical model of long-term alterations of bodily disownership: in its most commonly studied variant, people feel like a part of their body does not belong to them, leading to a desire for amputation of a physically healthy limb. Heat stimulations were applied before and after a placebo intervention (sham analgesic cream) to the desired and the undesired leg of 19 patients with BID with a unilateral leg amputation desire. Pain perception was assessed using pain thresholds, and ratings for pain intensity and pain unpleasantness. Results show that pain perception and placebo efficacy were lower for the undesired than for the desired leg, demonstrating a potential link between a clinical disorder of body ownership, pain perception, and placebo analgesia.

Brain Abnormalities in Individuals with a Desire for a Healthy Limb Amputation: Somatosensory, Motoric or Both? A Task-Based fMRI Verdict

Body integrity dysphoria (BID), a long-lasting desire for the amputation of physically healthy limbs, is associated with reduced fMRI resting-state functional connectivity of somatosensory cortices. Here, we used fMRI to evaluate whether these findings could be replicated and expanded using a task-based paradigm. We measured brain activations during somatosensory stimulation and motor tasks for each of the four limbs in ten individuals with a life-long desire for the amputation of the left leg and fourteen controls. For the left leg, BID individuals had reduced brain activation in the right superior parietal lobule for somatosensory stimulation and in the right paracentral lobule for the motor task, areas where we previously found reduced resting-state functional connectivity. In addition, for somatosensory stimulation only, we found a robust reduction in activation of somatosensory areas SII bilaterally, mostly regardless of the stimulated body part. Areas SII were regions of convergent activations for signals from all four limbs in controls to a significantly greater extent than in subjects with BID. We conclude that BID is associated with altered integration of somatosensory and, to a lesser extent, motor signals, involving limb-specific cortical maps and brain regions where the first integration of body-related signals is achieved through convergence.

Body integrity identity disorder using augmented reality: a symptom reduction study

Body integrity identity disorder (BIID) is a rare condition characterised by a discrepancy between specific areas of an individual's perceived body image and body schema which causes the individual to disassociate those physical areas of their body from their internal representation. There are currently no efficacious, ethically unambiguous means for achieving long-lasting symptom reductions. In the case we present, two patients with BIID underwent an augmented reality (AR)-based simulation that virtually amputated their alienated limbs, allowing them to experience their ideal selves. During the exposure, both patients reported reductions in BIID-related complaints. These preliminary results suggest the existence of a possible therapeutic and diagnostic potential that AR possesses, which warrants further consideration within clinical healthcare settings.

When having a limb means feeling overcomplete. Xenomelia, the chronic sense of disownership and the right parietal lobe hypothesis

ABSTRACTXenomelia is a rare condition characterized by a persistent and intense desire for amputation of one or more healthy limbs. Some frequent clinical manifestations suggest the involvement of distinct neural substrates. Specifically, recent aetiopathological hypotheses about xenomelia propose a neurodevelopmental origin, highlighting the putative contribution of the right parietal lobe and right insula, known to subserve the construction of a coherent representation of the body as a whole. This literature review is aimed at analysing relevant findings about structural and functional brain correlates of xenomelia, focusing on the identification of key regions and their hemispheric distribution. Finally, implications about the potential link between xenomelia and phylogenetic development of the right parietal lobe are discussed. Despite a certain degree of heterogeneity and the spatial extension of networks involved, signs of partial right-sided lateralization of cortical nodes and left-sided lateralization of subcortical nodes emerged. Indeed, some areas-rsPL, riPL, PMC and rInsula-have been consistently found altered in xenomelia. In conclusion, the presence of both structural and functional multi-layered brain abnormalities in xenomelia suggests a multifactorial aetiology; however, as the prevalence of correlational studies, causal relationships remain to be investigated.

Lower limb peripersonal space and the desire to amputate a leg

Body integrity identity disorder (BIID) is a rare condition defined by a persistent desire to amputate or paralyze a healthy limb (usually one or both of the legs). This desire arises from experiencing a mismatch between the internal body model and the actual physical/functional boundaries of the body. People with BIID show an abnormal physiological response to stimuli approaching the affected (unwanted) but not the unaffected leg, which might suggest a retracted peripersonal space (PPS: a multisensory integration zone near the body) around the unwanted limb. Thus, using a visuo-tactile interaction task, we examined leg PPS in a group of healthy men and three men with BIID who desired unilateral leg amputation. PPS size (~ 70 cm) around the unwanted BIID legs did not differ from that of healthy controls. Although the leg feels foreign in BIID, it still seems to maintain a PPS, presumably to protect it and facilitate interactions within the surrounding environment.

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.

Mental rotation of feet in individuals with Body Integrity Identity Disorder, lower-limb amputees, and normally-limbed controls

Body Integrity Identity Disorder (BIID) is a non-psychotic condition wherein individuals desire amputation or paralysis of one or more healthy, fully-functioning limbs (predominantly the legs). Individuals with BIID have been suggested to have a mismatch between the perceived mental representation of the body and its actual physical structure, such that their desired identity matches that of a lower-limb amputee. Accordingly, studies have reported an altered central network involving body representation of the legs in BIID, but its relationship to behavior remains unclear. In the present study, we investigated the integrity of body representation in individuals with BIID, acquired lower-limb amputees, and normally-limbed controls using an online mental rotation task. Participants judged the laterality of left and right foot images presented from different views, orientations, and of different types. We expected BIID participants to be slower for mentally rotating images that corresponded to their affected legs than lower-limb amputees and normally-limbed participants. We found that the groups did not significantly differ in their performance. All participants were slower at judging feet presented in awkward postures than natural postures, replicating previous studies and validating our online paradigm. The results are discussed in terms of the robust nature of visual and sensorimotor lower-limb representations, whether related to the self or as prototype, in the context of disturbed lower-limb integrity.