Balancing the "inner" and the "outer" self: interoceptive sensitivity modulates self-other boundaries

An exploration of the associations between facets of interoceptive awareness and body image in adolescents

Previous research suggests that lower interoceptive awareness is associated with more negative body image during adolescence. However, studies have not distinguished between adaptive and maladaptive modes of attention toward interoceptive signals, and relationships between interoceptive awareness and positive body image remain unexplored. To address these issues, a sample of 265 British adolescents (140 girls, 125 boys) aged 13-16 years completed measures of interoceptive awareness, body appreciation, functionality appreciation, body pride, body shame, and body surveillance. Correlational analyses broadly indicated that greater interoceptive awareness was significantly associated with more positive body image. Multiple regressions revealed significant predictive relationships between interoceptive awareness and all facets of body image in both girls and boys, except body surveillance, which was not statistically significant for girls. At the univariate level, the interoceptive awareness facets of Attention Regulation, Body Listening, Self-Regulation, and Trusting emerged as significant predictors for at least one facet of positive body image, whilst the Noticing and Emotional Awareness facets did not. These findings broadly align with previous research with adults, which has indicated that the way interoceptive stimuli are appraised and responded to might be more closely associated with facets of body image than the tendency to notice interoceptive stimuli.

Getting closer: Synchronous interpersonal multisensory stimulation increases closeness and attraction toward an opposite-sex other in female participants

Experiencing tactile facial stimulation while seeing synchronous stimulations delivered to another's face induces enfacement, i.e. the subjective experience of ownership over the other's face. The synchronous Interpersonal Multisensory Stimulation (IMS) procedure leading to enfacement induces changes beyond the bodily sense of self, such as increased feeling of closeness between self and other. However, evidence for such an influence of IMS on higher-level self-other representations remains limited. Moreover, research has been restricted to settings involving a same-sex other. The current study tested, in female participants, whether IMS could promote social closeness and attraction toward an opposite-sex other. Across two experiments, enfacement with an opposite-sex face was successfully obtained. Synchronous (vs. asynchronous) IMS yielded greater closeness with the other and induced greater Liking and Attraction scores. These novel findings add further evidence to the existence of a link between body representation and social cognition. Implications for interpersonal attraction are discussed.

Interoceptive accuracy is associated with emotional contagion in a valence- and sex-dependent manner

Over the last years, the neurobiological mechanisms of empathy have been extensively investigated. Recent investigations suggest that interoceptive processes, in particular, those that are related to the experience and perception of cardiac changes, are relevant for affect sharing, mentalizing and self-other distinction. To further investigate the association between interoception and affect-sharing, we measured emotional contagion and interoceptive accuracy in a sample of healthy participants (n = 84). Emotional contagion was assessed with an established self-report questionnaire and interoceptive accuracy was assessed with a validated heartbeat detection task. Across a series of complementary analyses, we found a sex- and valence-dependent association between interoception and affection sharing: Among female but not male participants, interoceptive accuracy was positively associated with emotional contagion for negative but not positive states of others. We provide an evolutionary-based explanation for these findings, which are consistent with previous findings showing positive associations between interoceptive accuracy, mentalizing and self-other distinction.

Atypical bodily self-awareness in vicarious pain responders

Vicarious perception refers to the ability to co-represent the experiences of others. Prior research has shown considerable inter-individual variability in vicarious perception of pain, with some experiencing conscious sensations of pain on their own body when viewing another person in pain (conscious vicarious perception/mirror-pain synaesthesia). Self-Other Theory proposes that this conscious vicarious perception may result from impairments in self-other distinction and maintaining a coherent sense of bodily self. In support of this, individuals who experience conscious vicarious perception are more susceptible to illusions of body ownership and agency. However, little work has assessed whether trait differences in bodily self-awareness are associated with conscious vicarious pain. Here we addressed this gap by examining individual difference factors related to awareness of the body, in conscious vicarious pain responders. Increased self-reported depersonalization and interoceptive sensibility was found for conscious vicarious pain responders compared with non-responders, in addition to more internally oriented thinking (associated with lower alexithymia). There were no significant differences in trait anxiety. Results indicate that maintaining a stable sense of the bodily self may be important for vicarious perception of pain, and that vicarious perception might also be enhanced by attention towards internal bodily states. This article is part of a discussion meeting issue 'Bridging senses: novel insights from synaesthesia'.

Prediction-based neural mechanisms for shielding the self from existential threat

The human mind has an automatic tendency to avoid awareness of its mortality. How this protective mechanism is implemented at the neuronal level is unknown. Here we test the hypothesis that prediction-based mechanisms mediate death-denial by shielding the self from existential threat. We provide evidence that self-specific predictive processes are downregulated during the perception of death-related linguistic stimuli and that this mechanism can predict fear-of-death. Using a magnetoencephalography visual mismatch paradigm, we show that the brain's automatic prediction response to deviancy is eliminated when death words and self-face representations are coupled, but remains present when coupled to other-face or to negative words. We further demonstrate a functional link between how death impacts self-image vs. Other-image, and show that it predicts fear-of-death. Finally, we confirm this effect in a behavioral active inference experiment showing that death-related words bias perceptual judgment on facial self and other morphed video clips. Together these results lay out, for the first time, a plausible neural-based mechanism of death-denial.

Embodiment into a robot increases its acceptability

Recent studies have shown how embodiment induced by multisensory bodily interactions between individuals can positively change social attitudes (closeness, empathy, racial biases). Here we use a simple neuroscience-inspired procedure to beam our human subjects into one of two distinct robots and demonstrate how this can readily increase acceptability and social closeness to that robot. Participants wore a Head Mounted Display tracking their head movements and displaying the 3D visual scene taken from the eyes of a robot which was positioned in front of a mirror and piloted by the subjects’ head movements. As a result, participants saw themselves as a robot. When participant’ and robot’s head movements were correlated, participants felt that they were incorporated into the robot with a sense of agency. Critically, the robot they embodied was judged more likeable and socially closer. Remarkably, we found that the beaming experience with correlated head movements and corresponding sensation of embodiment and social proximity, was independent of robots’ humanoid’s appearance. These findings not only reveal the ease of body-swapping, via visual-motor synchrony, into robots that do not share any clear human resemblance, but they may also pave a new way to make our future robotic helpers socially acceptable.

An interoceptive illusion of effort induced by false heart-rate feedback

Interoception, or the sense of the internal state of the body, is key to the adaptive regulation of our physiological needs. Recent theories contextualize interception within a predictive coding framework, according to which the brain both estimates and controls homeostatic and physiological variables, such as hunger, thirst, and effort levels, by orchestrating sensory, proprioceptive, and interoceptive signals from inside the body. This framework suggests that providing false interoceptive feedback may induce misperceptions of physiological variables, or "interoceptive illusions." Here we ask whether it is possible to produce an illusory perception of effort by giving participants false acoustic feedback about their heart-rate frequency during an effortful cycling task. We found that participants reported higher levels of perceived effort when their heart-rate feedback was faster compared with when they cycled at the same level of intensity with a veridical feedback. However, participants did not report lower effort when their heart-rate feedback was slower, which is reassuring, given that failing to notice one's own effort is dangerous in ecologically valid conditions. Our results demonstrate that false cardiac feedback can produce interoceptive illusions. Furthermore, our results pave the way for novel experimental manipulations that use illusions to study interoceptive processing.

Multiple dimensions of interoceptive awareness are associated with facets of body image in British adults

Previous research has identified a relationship between interoception and body image, where lower interoceptive awareness (IA) is associated with negative body image. However, relationships between facets of interoception and positive body image remain unexplored, and men and older adults remain underrepresented. To overcome these limitations, we assessed relationships between multiple dimensions of interoceptive awareness (IA) and multiple facets of body image in community adults. An online sample of 646 British adults (447 women) aged 18-76 years completed the Multidimensional Assessment of Interoceptive Awareness (MAIA), the Body Appreciation Scale-2, the Functionality Appreciation Scale, the Authentic Pride subscale from the Body and Appearance Self-Conscious Emotions Scale, and the Appearance Orientation and Overweight Preoccupation subscales from the Multidimensional Body-Self Relations Questionnaire. Hierarchical regressions revealed significant predictive relationships between IA and all five facets of body image after controlling for sex, body mass index, and age. In the final models, the MAIA subscales emerged as significant predictors for at least one facet of body image, with the exception of the MAIA Body Listening subscale. These findings extend previous work by demonstrating significant relationships between IA and previously unexplored facets of body image, which may hold promise for practitioner-based interventions.

Altered bodily self-consciousness and peripersonal space in autism

There is some evidence that disordered self-processing in autism spectrum disorders is linked to the social impairments characteristic of the condition. To investigate whether bodily self-consciousness is altered in autism spectrum disorders as a result of multisensory processing differences, we tested responses to the full body illusion and measured peripersonal space in 22 adults with autism spectrum disorders and 29 neurotypical adults. In the full body illusion set-up, participants wore a head-mounted display showing a view of their ‘virtual body’ being stroked synchronously or asynchronously with respect to felt stroking on their back. After stroking, we measured the drift in perceived self-location and self-identification with the virtual body. To assess the peripersonal space boundary we employed an audiotactile reaction time task. The results showed that participants with autism spectrum disorders are markedly less susceptible to the full body illusion, not demonstrating the illusory self-identification and self-location drift. Strength of self-identification was negatively correlated with severity of autistic traits and contributed positively to empathy scores. The results also demonstrated a significantly smaller peripersonal space, with a sharper (steeper) boundary, in autism spectrum disorders participants. These results suggest that bodily self-consciousness is altered in participants with autism spectrum disorders due to differences in multisensory integration, and this may be linked to deficits in social functioning.

Shared multisensory experience affects Others' boundary: The enfacement illusion in schizophrenia

Schizophrenia has been described as a psychiatric condition characterized by deficits in one's own and others' face recognition, as well as by a disturbed sense of body-ownership. To date, no study has integrated these two lines of research with the aim of investigating Enfacement Illusion (EI) proneness in schizophrenia. To accomplish this goal, the classic EI protocol was adapted to test the potential plasticity of both Self-Other and Other-Other boundaries. Results showed that EI induced the expected malleability of Self-Other boundary among both controls and patients. Interestingly, for the first time, the present study demonstrates that also the Other-Other boundary was influenced by EI. Furthermore, comparing the two groups, the malleability of the Other-Other boundary showed an opposite modulation. These results suggest that, instead of greater Self-Other boundary plasticity, a qualitative difference can be detected between schizophrenia patients and controls in the malleability of the Other-Other boundary. The present study points out a totally new aspect about body-illusions and schizophrenia disorder, demonstrating that EI is not only confined to self-sphere but it also affects the way we discriminate others, representing a potential crucial aspect in the social domain.

Seeing myself through my heart: Cortical processing of a single heartbeat speeds up self-face recognition

Recent research has highlighted the contribution of interoceptive signals to different aspects of bodily self-consciousness (BSC) by means of the cardio-visual stimulation - i.e. perceiving a pulsing stimulus in synchrony with one's own heart. Here, for the first time, we investigate the effects of individual heartbeats on a critical feature of BSC, namely the recognition of one's own face. Across two studies, we explored the cardiac-timing effects on a classic self-face recognition task. In Study 1, participants saw morphed faces that contained different percentages of the self-face and that of another unfamiliar individual. Study 2 used a similar design, albeit participants saw morphed faces of the self-face and that of a familiar other to provide a better control of self-familiarity. Results from both studies consistently revealed that the cortical processing of cardiac afferent signals conveyed by the firing of arterial baroreceptors affects the speed, but not the accuracy, of self-face recognition, when a single picture is presented during cardiac systole, as compared to diastole. This effect is stronger and more stable for stimuli with more self-cues than other-cues and for 'ambiguous' stimuli - i.e. at the individual point of subjective equality. Results from Study 2 also revealed that cardiac effects on the speed of self-face recognition cannot be explained simply on the basis of the imbalanced familiarity between the self's and other's faces used. The present findings highlight the interoceptive contributions to self-recognition and may be expand our understanding of pathological disturbances of self-experience.

Malleability of the self: electrophysiological correlates of the enfacement illusion

Self-face representation is fundamentally important for self-identity and self-consciousness. Given its role in preserving identity over time, self-face processing is considered as a robust and stable process. Yet, recent studies indicate that simple psychophysics manipulations may change how we process our own face. Specifically, experiencing tactile facial stimulation while seeing similar synchronous stimuli delivered to the face of another individual seen as in a mirror, induces 'enfacement' illusion, i.e. the subjective experience of ownership of the other's face and a bias in attributing to the self, facial features of the other person. Here we recorded visual Event-Related Potentials elicited by the presentation of self, other and morphed faces during a self-other discrimination task performed immediately after participants received synchronous and control asynchronous Interpersonal Multisensory Stimulation (IMS). We found that self-face presentation after synchronous as compared to asynchronous stimulation significantly reduced the late positive potential (LPP; 450-750 ms), a reliable electrophysiological marker of self-identification processes. Additionally, enfacement cancelled out the differences in LPP amplitudes produced by self- and other-face during the control condition. These findings represent the first direct neurophysiological evidence that enfacement may affect self-face processing and pave the way to novel paradigms for exploring defective self-representation and self-other interactions.

Interoception and Its Interaction with Self, Other, and Emotion Processing: Implications for the Understanding of Psychosocial Deficits in Borderline Personality Disorder

PURPOSE OF REVIEW

We review evidence for the potential importance of interoception, i.e., the processing of signals arising from inside the body, for deficient psychosocial functioning in borderline personality disorder (BPD).

RECENT FINDINGS

Evidence suggests that variability in interoception interacts with higher-order psychological functions such as self, other, and emotion processing. These domains are characteristically impaired in BPD, suggesting a likely causal role of disturbed interoception in the etiology of the disorder. The inability to identify and describe one's own emotional states represents a proxy of impaired interoception which might further mediate between the perception of inner physiological conditions and psychosocial functioning in BPD. There is preliminary evidence explaining how early life stress might adversely affect central interoceptive representation and psychosocial functioning in BPD. Based on these findings and the specific pattern of disturbances in BPD, we propose the crucial role of interoception in an integrated biobehavioral model for BPD.

Altered Processing and Integration of Multisensory Bodily Representations and Signals in Eating Disorders: A Possible Path Toward the Understanding of Their Underlying Causes

According to the Diagnostic and Statistical Manual of Mental Disorders (DSM V) eating problems are the clinical core of eating disorders (EDs). However, the importance of shape and weight overvaluation symptoms in these disorders underlines the critical role of the experience of the body in the etiology of EDs. This article suggests that the transdiagnostic centrality of these symptoms in individuals with EDs may reflect a deficit in the processing and integration of multisensory bodily representations and signals. Multisensory body integration is a critical cognitive and perceptual process, allowing the individual to protect and extend her/his boundaries at both the homeostatic and psychological levels. To achieve this goal the brain integrates sensory data arriving from real-time multiple sensory modalities and internal bodily information with predictions made using the stored information about the body from conceptual, perceptual, and episodic memory. In this view the emotional, visual, tactile, proprioceptive and interoceptive deficits reported by many authors in individuals with EDs may reflect a broader impairment in multisensory body integration that affects the individual's abilities: (a) to identify the relevant interoceptive signals that predict potential pleasant (or aversive) consequences; and (b) to modify/correct the autobiographical allocentric (observer view) memories of body related events (self-objectified memories). Based on this view, the article also proposes a strategy, based on new technologies (i.e., virtual reality and brain/body stimulation), for using crossmodal associations to reactivate and correct the multisensory body integration processes.

Affective Touch Enhances Self-Face Recognition During Multisensory Integration

Multisensory integration is a powerful mechanism for constructing body awareness and key for the sense of selfhood. Recent evidence has shown that the specialised C tactile modality that gives rise to feelings of pleasant, affective touch, can enhance the experience of body ownership during multisensory integration. Nevertheless, no study has examined whether affective touch can also modulate psychological identification with our face, the hallmark of our identity. The current study used the enfacement illusion paradigm to investigate the role of affective touch in the modulation of self-face recognition during multisensory integration. In the first experiment (N = 30), healthy participants were stroked on the cheek while they were looking at another face being stroked on the cheek in synchrony or asynchrony with affective (slow; CT-optimal) vs. neutral (fast; CT-suboptimal) touch. In the second experiment (N = 38) spatial incongruence of touch (cheek vs. forehead) was used as a control condition instead of temporal asynchrony. Overall, our data suggest that CT-optimal, affective touch enhances subjective (but not behavioural) self-face recognition during synchronous and spatially congruent integration of different sensations and possibly reduces deafference during asynchronous multisensory integration. We discuss the role of affective touch in shaping the more social aspects of our self.

You Fill My Heart: Looking at One's Partner Increases Interoceptive Accuracy

The integration of external and internal bodily signals provides a coherent, multisensory experience of one’s own body. The ability to accurately detect internal bodily sensations is referred to as interoceptive accuracy (IAcc). Previous studies found that IAcc can be increased when people with low IAcc engage in self-processing such as when looking in the mirror or at a photograph of one’s own face. However, the way the self is represented changes depending on the context. Specifically, in social situations, the self is experienced in relation to significant others and not as an isolated individual. Intriguingly, in a relational context romantic partners can be used as social mirrors for one’s self. We here investigated whether directing one’s attention to romantic partners would enhance one’s IAcc, similar to the effect of self-face observation when the self is processed in isolation. During a heartbeat counting task, both concurrent self-face and partner-face observation improved accuracy in those with initially low IAcc; however, this improvement was significantly greater for the partner’s face. These results suggest that significant others may play an important role in determining the quality of one’s self-awareness. Given that high interoceptive awareness is linked to better emotion regulation, increased IAcc during partner observation is likely to have an adaptive role in maintaining stable and secure romantic relationships through greater emotion regulation.

The multisensory basis of the self: From body to identity to others [Formula: see text]

By grounding the self in the body, experimental psychology has taken the body as the starting point for a science of the self. One fundamental dimension of the bodily self is the sense of body ownership that refers to the special perceptual status of one's own body, the feeling that "my body" belongs to me. The primary aim of this review article is to highlight recent advances in the study of body ownership and our understanding of the underlying neurocognitive processes in three ways. I first consider how the sense of body ownership has been investigated and elucidated in the context of multisensory integration. Beyond exteroception, recent studies have considered how this exteroceptively driven sense of body ownership can be linked to the other side of embodiment, that of the unobservable, yet felt, interoceptive body, suggesting that these two sides of embodiment interact to provide a unifying bodily self. Lastly, the multisensorial understanding of the self has been shown to have implications for our understanding of social relationships, especially in the context of self-other boundaries. Taken together, these three research strands motivate a unified model of the self inspired by current predictive coding models.

Active interoceptive inference and the emotional brain

We review a recent shift in conceptions of interoception and its relationship to hierarchical inference in the brain. The notion of interoceptive inference means that bodily states are regulated by autonomic reflexes that are enslaved by descending predictions from deep generative models of our internal and external milieu. This re-conceptualization illuminates several issues in cognitive and clinical neuroscience with implications for experiences of selfhood and emotion. We first contextualize interoception in terms of active (Bayesian) inference in the brain, highlighting its enactivist (embodied) aspects. We then consider the key role of uncertainty or precision and how this might translate into neuromodulation. We next examine the implications for understanding the functional anatomy of the emotional brain, surveying recent observations on agranular cortex. Finally, we turn to theoretical issues, namely, the role of interoception in shaping a sense of embodied self and feelings. We will draw links between physiological homoeostasis and allostasis, early cybernetic ideas of predictive control and hierarchical generative models in predictive processing. The explanatory scope of interoceptive inference ranges from explanations for autism and depression, through to consciousness. We offer a brief survey of these exciting developments.

This article is part of the themed issue ‘Interoception beyond homeostasis: affect, cognition and mental health’.

Not That Heart-Stopping After All: Visuo-Cardiac Synchrony Does Not Boost Self-Face Attribution

Recent experimental evidence and theoretical models suggest that an integration of exteroceptive and interoceptive signals underlies several key aspects of the bodily self. While it has been shown that self-attribution of both the hand and the full-body are altered by conflicting extero-exteroceptive (e.g. visuo-tactile) and extero-interoceptive (e.g. visuo-cardiac) information, no study has thus far investigated whether self-attribution of the face might be altered by visuo-cardiac stimulation similarly to visuo-tactile stimulation. In three independent groups of participants we presented ambiguous (i.e. morphed with a stranger's face) self-faces flashing synchronously or asynchronously with the participants’ heartbeat. We then measured the subjective percentages of self-face attribution of morphed stimuli. To control for a potential effect of visuo-cardiac synchrony on familiarity, a task assessing the attribution of a familiar face was introduced. Moreover, different durations of visuo-cardiac flashing and different degrees of asynchronicity were used. Based on previous studies showing that synchronous visuo-cardiac stimulation generally increases self-attribution of the full-body and the hand, and that synchronous visuo-tactile stimulation increases self-face attribution, we predicted higher self-face attribution during the synchronous visuo-cardiac flashing of the morphed stimuli. In contrast to this hypothesis, the results showed no difference between synchronous and asynchronous stimulation on self-face attribution in any of the three studies. We thus conclude that visuo-cardiac synchrony does not boost self-attribution of the face as it does that of hand and full-body.

Is that me in the mirror? Depersonalisation modulates tactile mirroring mechanisms

Our sense of self is thought to develop through sensory-motor contingencies provided, not only by observing one's own body, but also by mirroring interactions with others. This suggests that there is a strong link between mirroring mechanisms and the bodily self. The present study tested whether this link is expressed at early, implicit stages of the mirroring process or at later, more cognitive stages. We also provide, to the best of our knowledge, the first demonstration of how inter-individual differences in our sense of bodily self may affect mirroring mechanisms. We used somatosensory event-related potentials (SEPs) to investigate the temporal dynamics of mirroring highly self-related information (viewed touch on one's own face) compared to other-related information (viewed touch on a stranger's face), in individuals with low and high levels of depersonalisation, a mental condition characterised by feeling detached or estranged from one's self and body. For the low-depersonalisation group, mirroring for self-related events (P45) preceded mirroring for other-related events (N80). At later stages (P200), mirroring was stronger for other-related than self-related events. This shows that early, implicit and later, more cognitive processes play different relative roles in mirroring self- and other-related bodily events. Critically, mirroring differed in the high-depersonalisation group, specifically for self-related events. An absence of early, implicit mirroring for self-related events over P45 suggests that the associated processes may be the neural correlates of the disembodiment experienced in depersonalisation. A lack of differential mirroring for self- and other-related events over P200 may reflect compensatory mechanisms that redress deficiencies in mirroring at earlier stages, which may break down to give rise to symptoms of depersonalisation. Alternatively, or in addition, they may represent an attenuation of processes related to self-other distinction. Our study thus shows that mirroring, especially for events on one's own face, can be strongly affected by how connected the observer feels to their own bodily self.

Threat and the Body: How the Heart Supports Fear Processing

Mental processes depend upon a dynamic integration of brain and body. Emotions encompass internal physiological changes which, through interoception (sensing bodily states), underpin emotional feelings, for example, cardiovascular arousal can intensify feelings of fear and anxiety. The brain is informed about how quickly and strongly the heart is beating by signals from arterial baroreceptors. These fire in bursts after each heartbeat, and are quiet between heartbeats. The processing of fear stimuli is selectively enhanced by these phasic signals, and these inhibit the processing of other types of stimuli including physical pain. Behavioural and neuroimaging studies detail this differential impact of heart signals on the processing of salient stimuli, and add to knowledge linking rhythmic activity in brain and body to perceptual consciousness.

Cardio-visual integration modulates the subjective perception of affectively neutral stimuli

Interoception, which refers to the perception of internal body signals, has been consistently associated with emotional processing and with the sense of self. However, its influence on the subjective appraisal of affectively neutral and body-unrelated stimuli is still largely unknown. Across two experiments we sought to investigate this issue by asking participants to detect changes in the flashing rhythm of a simple stimulus (a circle) that could either be pulsing synchronously with their own heartbeats or following the pattern of another person's heart. While overall task performance did not vary as a function of cardio-visual synchrony, participants were better at identifying trials in which no change occurred when the flashes were synchronous with their own heartbeats. This study adds to the growing body of research indicating that we use our body as a reference point when perceiving the world; and extends this view by focusing on the role that signals coming from inside the body, such as heartbeats, may play in this referencing process. Specifically we show that private interoceptive sensations can be combined with affectively neutral information unrelated to the self to influence the processing of a multisensory percept. Results are discussed in terms of both standard multisensory integration processes and predictive coding theories.

Temperament and psychopathological syndromes specific susceptibility for rubber hand illusion

The aim of this study is to explore individual capacity for self-integration, susceptibility to the Rubber Hand Illusion (RHI) and the role of temperament factors in the emergence of body schema and body image dissociation. The RHI factors, proprioceptive drift, body ownership and body disownership were assessed in 48 university students. Personality and psychiatric vulnerability were measured by the Temperament and Character Inventory (TCI-R) and the Symptom Checklist-90-R (SCL-90-R). Our study pointed to the fact that the extent of behaviourally defined proprioceptive drift was associated with temperament factors, especially with Novelty Seeking and Harm Avoidance. Further, the ownership was associated with Symptom Checklist factors, especially with elevated Interpersonal Sensitivity and vulnerability to Schizotypy and Paranoid Ideation and elevated disownership score was found in the case of elevated Schizotypy, including a depersonalisation feeling when the RHI was induced. The RHI may be considered as a conflicting situation, in which a way to cope with incongruent multimodal, visual, haptic and proprioceptive stimulation provides an opportunity to test body integration and embodiment processes in healthy participants and patients without disadvantageous outcomes. The results support and replenish the two opposite processing models of the RHI with a third, temperament-based procedural mechanism.

The bodily self and its disorders: neurological, psychological and social aspects

PURPOSE OF REVIEW

The experience of ourselves as an embodied agent with a first-person perspective is referred to as 'bodily self'. We present a selective overview of relevant clinical and experimental studies.

RECENT FINDINGS

Sharing multisensory body space with others can be observed in patients with structurally altered bodies (amputations, congenital absence of limbs), with altered functionality after hemiplegia, such as denial of limb ownership (somatoparaphrenia) and with alterations in bodily self-consciousness on the level of the entire body (e.g. in autoscopic phenomena). In healthy participants, the mechanisms underpinning body ownership and observer perspective are empirically investigated by multisensory stimulation paradigms to alter the bodily self. The resulting illusions have promoted the understanding of complex disturbances of the bodily self, such as out-of-body experiences. We discuss the role of interoception in differentiating between self and others and review current advances in the study of body integrity identity disorder, a condition shaped as much by neurological as by social-psychological factors.

SUMMARY

We advocate a social neuroscience approach to the bodily self that takes into account the interactions between body, mind and society and might help close the divide between neurology and psychiatry.

Disentangling interoception: insights from focal strokes affecting the perception of external and internal milieus

Interoception is the moment-to-moment sensing of the physiological condition of the body. The multimodal sources of interoception can be classified into two different streams of afferents: an internal pathway of signals arising from core structures (i.e., heart, blood vessels, and bronchi) and an external pathway of body-mapped sensations (i.e., chemosensation and pain) arising from peripersonal space. This study examines differential processing along these streams within the insular cortex (IC) and their subcortical tracts connecting frontotemporal networks. Two rare patients presenting focal lesions of the IC (insular lesion, IL) or its subcortical tracts (subcortical lesion, SL) were tested. Internally generated interoceptive streams were assessed through a heartbeat detection (HBD) task, while those externally triggered were tapped via taste, smell, and pain recognition tasks. A differential pattern was observed. The IC patient showed impaired internal signal processing while the SL patient exhibited external perception deficits. Such selective deficits remained even when comparing each patient with a group of healthy controls and a group of brain-damaged patients. These outcomes suggest the existence of distinguishable interoceptive streams. Results are discussed in relation with neuroanatomical substrates, involving a fronto-insulo-temporal network for interoceptive and cognitive contextual integration.

Heartfelt empathy? No association between interoceptive awareness, questionnaire measures of empathy, reading the mind in the eyes task or the director task

Interoception, defined as afferent information arising from within the body, is the basis of all emotional experience and underpins the 'self.' However, people vary in the extent to which interoceptive signals reach awareness. This trait modulates both their experience of emotion and their ability to distinguish 'self' from 'other' in multisensory contexts. The experience of emotion and the degree of self/other distinction or overlap are similarly fundamental to empathy, which is an umbrella term comprising affect sharing, empathic concern and perspective-taking (PT). A link has therefore often been assumed between interoceptive awareness (IA) and empathy despite a lack of clear evidence. To test the hypothesis that individual differences in both traits should correlate, we measured IA in four experiments, using a well-validated heartbeat perception task, and compared this with scores on several tests that relate to various aspects of empathy. We firstly measured scores on the Index of Interpersonal Reactivity and secondly on the Questionnaire of Cognitive and Affective Empathy. Thirdly, because the 'simulationist' account assumes that affect sharing is involved in recognizing emotion, we employed the 'Reading the Mind in the Eyes Task' for the recognition of facial expressions. Contrary to expectation, we found no significant relationships between IA and any aspect of these measures. This striking lack of direct links has important consequences for hypotheses about the extent to which empathy is necessarily embodied. Finally, to assess cognitive PT ability, which specifically requires self/other distinction, we used the 'Director Task' but found no relationship. We conclude that the abilities that make up empathy are potentially related to IA in a variety of conflicting ways, such that a direct association between IA and various components of empathy has yet to be established.

The Contributions of Interoceptive Awareness to Cognitive and Affective Facets of Body Experience

Experience of one’s own body relies on signals arising within the body as well as on exteroceptive information, and on appraisal of cognitive and affective aspects of these signals. The present study investigated the impact of sensitivity to internal signals, that is, interoceptive awareness, on interindividual differences in cognitive and emotional aspects of body experience. Subjects with accurate (n = 30) versus poor (n = 30) interoceptive awareness, classified via a heartbeat perception task, completed the Body Consciousness Questionnaire and the Body Appraisal Inventory. Possible effects of emotional state on body experience were controlled for using measures of mood and anxiety. While the groups did not differ in their emotional state, individuals with accurate cardiac interoceptive awareness exhibited higher subjective sensitivity to bodily sensations and a more positive body image, characterized by stronger body-related self-confidence, greater satisfaction with physical appearance, greater perceived bodily self-control, as well as reduced hypochondriacal concerns, sexual discontent, and shame. The present findings extend earlier research on the importance of perception of physical cues for emotion, cognition, and behavior regulation. Our results underline the contribution of interoceptive information to body experience, where interindividual differences in the accessibility of such information modulate cognitive and affective facets of body image.

Interoceptive sensitivity, body image dissatisfaction, and body awareness in healthy individuals

Relationships among interoceptive sensitivity (IS), body image dissatisfaction, body mass index (BMI), and self-reported body awareness were investigated in a cross-sectional study. Eighty-two Norwegian high school students and 70 Hungarian undergraduate university students participated in the study. Subjects completed two questionnaires (Body Image Ideals Questionnaire - BIQ; Body Awareness Questionnaire - BAQ) followed by the assessment of interoceptive sensitivity using the Mental Tracking Method (MTM). An inverse, medium-level relationship between body image dissatisfaction and IS was found in both the Norwegian and the Hungarian samples. The relationships between IS and self-reported body awareness, and between body image dissatisfaction and BMI were uniformly non-significant in both samples. Predictors of body image dissatisfaction were resting heart rate, gender, and IS in the regression analysis after controlling for BMI, age, and nationality. The negative relationship between IS and body image dissatisfaction described in patients with anorexia nervosa also exists in healthy individuals. There is no direct connection between IS and self-reported body awareness.

Increased functional connectivity between superior colliculus and brain regions implicated in bodily self-consciousness during the rubber hand illusion

Bodily self-consciousness refers to bodily processes operating at personal, peripersonal, and extrapersonal spatial dimensions. Although the neural underpinnings of representations of personal and peripersonal space associated with bodily self-consciousness were thoroughly investigated, relatively few is known about the neural underpinnings of representations of extrapersonal space relevant for bodily self-consciousness. In the search to unravel brain structures generating a representation of the extrapersonal space relevant for bodily self-consciousness, we developed a functional magnetic resonance imaging (fMRI) study to investigate the implication of the superior colliculus (SC) in bodily illusions, and more specifically in the rubber hand illusion (RHi), which constitutes an established paradigm to study the neural underpinnings of bodily self-consciousness. We observed activation of the colliculus ipsilateral to the manipulated hand associated with eliciting of RHi. A generalized form of context-dependent psychophysiological interaction analysis unravelled increased illusion-dependent functional connectivity between the SC and some of the main brain areas previously involved in bodily self-consciousness: right temporoparietal junction (rTPJ), bilateral ventral premotor cortex (vPM), and bilateral postcentral gyrus. We hypothesize that the collicular map of the extrapersonal space interacts with maps of the peripersonal and personal space generated at rTPJ, vPM and the postcentral gyrus, producing a unified representation of space that is relevant for bodily self-consciousness. We suggest that processes of multisensory integration of bodily-related sensory inputs located in this unified representation of space constitute one main factor underpinning emergence of bodily self-consciousness.

Effect of a reversal mirror condition on orofacial mechanical sensitivity

The aim of this study was to investigate whether watching one's own face being touched in a reversal mirror condition modulates orofacial somatosensory sensitivity. A total of 37 healthy volunteers participated in a pilot study, the main study, and a control experiment. In the main experiment, 16 participants received seven different intensities of pinprick stimuli in the right infraorbital region. The perceived stimulus intensity was rated on a 0-50-100 numerical rating scale (NRS). In addition, the pinprick threshold (PiPT) was evaluated in the same region using an electronic von Frey device. During stimuli, participants were watching their own face in two different conditions (normal and reversal mirror) in randomized order. Subjective experiences during each condition were assessed with a questionnaire containing nine statements. The participants rated their level of agreement with the statements using a 7-item Likert scale. There were significant main effects on NRS scores of stimulus forces (p < 0.001) and experimental condition (p < 0.001). Post hoc analyses showed that stimulation with higher force levels induced significantly higher NRS scores (p < 0.001), but interestingly, there were significantly lower NRS scores in the reversal mirror condition than in the normal mirror condition (p < 0.001). There was no significant main effect of experimental condition on PiPT (p = 0.184). The experimental condition influenced the response to several statements significantly (p < 0.001). The somatosensory sensitivity may be impaired when the location of stimulation is not in accordance with the perception. In conclusion, hypoesthetic effects of a reversal mirror were present for fixed force measures but not for threshold measures. Further studies are now needed to describe the potential implications for other somatosensory modalities and orofacial pain conditions.

Closing the gap between the inside and the outside: interoceptive sensitivity and social distances

Humans' ability to represent their body state from within through interoception has been proposed to predict different aspects of human cognition and behaviour. We focused on the possible contribution of interoceptive sensitivity to social behaviour as mediated by adaptive modulation of autonomic response. We, thus, investigated whether interoceptive sensitivity to one's heartbeat predicts participants' autonomic response at different social distances. We measured respiratory sinus arrhythmia (RSA) during either a Social or a Non-social task. In the Social task each participant viewed an experimenter performing a caress-like movement at different distances from their hand. In the Non-social task a metal stick was moved at the same distances from the participant's hand. We found a positive association between interoceptive sensitivity and autonomic response only for the social setting. Moreover, only good heartbeat perceivers showed higher autonomic response 1) in the social compared to the non-social setting, 2) specifically, when the experimenter's hand was moving at boundary of their peripersonal space (20 cm from the participant's hand). Our findings suggest that interoceptive sensitivity might contribute to interindividual differences concerning social attitudes and interpersonal space representation via recruitment of different adaptive autonomic response strategies.