Chiara Baiano
email: chiara.baiano@unicampania.it

Xavier Job

Gabriella Santangelo

Malika Auvray

Louise P Kirsch

Interactions between interoception and perspective-taking: Current state of research and future directions

Keywords: interoception, interoceptive accuracy, interoceptive sensibility, interoceptive awareness, affective perspective-taking, cognitive perspective-taking, visuo-spatial perspective-taking, Theory of Mind, empathy

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Introduction

Our comprehension of the world is driven by both internal and external stimuli and the two influence each other. For a long time, research on human behaviour and perception has primarily concerned information coming from the external world (i.e. exteroception), neglecting the substantial amount of perceptual information arising from within the body. More recently, interest in the impact of afferent information arising from within the body on perception has grown considerably. Behaviour typically requires internal control mechanisms such as hormone release, adjustments of sympathetic or parasympathetic activity as well as motor commands [START_REF] Petzschner | Computational Models of Interoception and Body Regulation[END_REF]. Similarly, a strong integration of external and internal sensations is necessary for a unified perception. To allow for this, organisms must respond to the challenge of maintaining their physiological integrity in an ever-changing external environment [START_REF] Petzschner | Computational Models of Interoception and Body Regulation[END_REF].

Interoception refers to the sense of the physiological condition of the body [START_REF] Ceunen | On the Origin of Interoception[END_REF] and includes feelings such as pain, temperature, itch, affective touch, muscular activity, visceral sensations, vasomotor activity, hunger, thirst and air hunger [START_REF] Chen | The Emerging Science of Interoception: Sensing, Integrating, Interpreting, and Regulating Signals within the Self[END_REF]. More recently interoception has been defined as "the process by which the nervous system senses, interprets, and integrates signals originating from within the body, providing a moment-by-moment mapping of the body's internal landscape across conscious and unconscious levels" [START_REF] Khalsa | Interoception and Mental Health: A Roadmap[END_REF]. Interoceptive processing is crucial for the representation of the self as agentive, continuous and invariant over time [START_REF] Craig | The sentient self[END_REF]. For these reasons, interoception appears to be linked to mechanisms of embodiment [START_REF] Herbert | The body in the mind. On the relationship between interoception and embodiment[END_REF]. Embodiment refers to the idea that many aspects of cognition are shaped by our body, in particular, it implies that we use bodily experience to understand our own emotional experience and the experiences of others [START_REF] Ferrari | Mirror neurons, embodied emotions, and empathy[END_REF]. At the crossroad between spatial cognition and bodily sensation research, some scientists have proposed that the integration of various visceral/internal signals in the brain generates a body-centred reference frame [START_REF] Papageorgiou | Process and meta-cognitive dimensions of depressive and anxious thoughts and relationships with emotional intensity[END_REF][START_REF] Babo-Rebelo | Neural responses to heartbeats in the default network encode the self in spontaneous thoughts[END_REF], which is used to tag mental processes as being self-related [START_REF] Babo-Rebelo | Interoceptive signals, brain dynamics and subjectivity[END_REF]. For example, the amplitude of heartbeat-evoked responses (i.e. neural responses to heartbeats, [START_REF] Coll | Systematic review and meta-analysis of the relationship between the heartbeat-evoked potential and interoception[END_REF] differs between imagining oneself or someone else [START_REF] Babo-Rebelo | Neural responses to heartbeats distinguish self from other during imagination[END_REF].

The ability to perceive visceral changes in the body, referred to as Interoceptive Accuracy (IAcc), is typically assessed with cardiac detection or discrimination tasks. Heartbeat detection procedures usually require participants to count the number of times they feel their heart beating during different time periods (i.e. the "heartbeat counting task", [START_REF] Schandry | Heart beat perception and emotional experience[END_REF], while heartbeat discrimination procedures involve differentiating the timing of individual heartbeats from external stimuli [START_REF] Whitehead | Relation of heart rate control to heartbeat perception[END_REF]. More recently, [START_REF] Garfinkel | Knowing your own heart: Distinguishing interoceptive accuracy from interoceptive awareness[END_REF] distinguished three dimensions for the assessment of interoceptive abilities: (i) interoceptive accuracy (performance on objective behavioural tests of heartbeat detection or discrimination); (ii) interoceptive sensibility (subjective measure assessed using questionnaires); (iii) interoceptive awareness (metacognitive awareness of interoceptive accuracy). These three dimensions were found to be partially distinct and dissociable. In addition to the perception of one's own cardiac signals, interoception also includes the perception of internal bodily states such as gastric signals [START_REF] Van Dyck | The Water Load Test as a measure of gastric interoception: Development of a two-stage protocol and application to a healthy female population[END_REF], temperature, itching and pain [START_REF] Ceunen | On the Origin of Interoception[END_REF].

Interoception contributes to a feeling that our conscious experiences are bound to the self, referred to as 'bodily self-awareness'. Bodily self-awareness includes the perception of visceral signals coming from our own body (i.e. interoception), the identification with one's body (i.e. body-ownership), the feeling of the body in space and the sense of agency [START_REF] Blanke | Behavioral, neural, and computational principles of bodily self-consciousness[END_REF]. Recent studies highlighted the strong interaction between interoceptive and exteroceptive abilities [START_REF] Azzalini | Visceral Signals Shape Brain Dynamics and Cognition[END_REF][START_REF] Herman | Neural divergence and convergence for interoceptive and somatosensory attention and detection[END_REF], and in particular their importance for self-other distinction. Exteroceptive abilities include all the signals (e.g. tactile and visual cues) involving a human body or body parts normally presented in space and surrounding the person's body [START_REF] Blanke | Behavioral, neural, and computational principles of bodily self-consciousness[END_REF].

An example illustrating the crosstalk between exteroceptive and interoceptive abilities is the Rubber Hand Illusion (RHI). When synchronous exteroceptive visuo-tactile stimulation between a rubber hand and the participant's hidden hand is delivered, many report subjective feelings of ownership for the rubber hand [START_REF] Botvinick | Rubber hands 'feel' touch that eyes see[END_REF]. The RHI has now become a robust measure of the sense of body-ownership and self-other boundaries. Participants with lower interoceptive accuracy, as measured by the heartbeat counting task [START_REF] Schandry | Heart beat perception and emotional experience[END_REF], reported a greater experience of the RHI, compared to individuals with higher interoceptive accuracy [START_REF] Tsakiris | Just a heartbeat away from one's body: interoceptive sensitivity predicts malleability of body-representations[END_REF]; but for recent counter findings see [START_REF] Horváth | Proprioception but not cardiac interoception is related to the rubber hand illusion[END_REF]. This finding is in line with the hypothesis that those with higher interoceptive accuracy have a stronger sense of self, centered on their internal bodily states [START_REF] Palmer | Going at the heart of social cognition: is there a role for interoception in self-other distinction?[END_REF].

Furthermore, multisensory integration of exteroceptive and interoceptive signals modulates the experience of body ownership in the RHI [START_REF] Suzuki | Multisensory integration across exteroceptive and interoceptive domains modulates self-experience in the rubberhand illusion[END_REF]. By combining computer-generated augmented reality with feedback of cardiac information, [START_REF] Suzuki | Multisensory integration across exteroceptive and interoceptive domains modulates self-experience in the rubberhand illusion[END_REF] implemented a "cardiac rubber hand illusion task" in which a rubber hand appeared to be pulsing in synchrony with the cardiac rhythm of the participant. Synchronous cardio-visual feedback presented on the rubber hand induced an enhanced experience of ownership of the virtual hand.

To examine more implicit aspects of self-other boundaries and their relationships with interoceptive accuracy, [START_REF] Imafuku | Interoception is associated with the impact of eye contact on spontaneous facial mimicry[END_REF] focused on the phenomenon of spontaneous facial mimicry. Results showed that observing another person's facial expression led to involuntary facial movements that matched the perceived facial configuration. Participants with higher interoceptive accuracy showed higher spontaneous facial mimicry in a certain social context (direct eye gaze), suggesting a greater blurring of self-other boundaries. This implies that interoception is related not only to the perceived boundary of the self, but also to social cues. In regard to previous findings with the RHI [START_REF] Tsakiris | Just a heartbeat away from one's body: interoceptive sensitivity predicts malleability of body-representations[END_REF], these mixed results suggest that several mechanisms are involved when distinguishing our own feelings and behaviours from that of others, such as perspective-taking [START_REF] Steinbeis | The role of self-other distinction in understanding others' mental and emotional states: neurocognitive mechanisms in children and adults[END_REF].

Perspective-taking is a multidimensional construct referring to the ability to take another person's 'point of view' and is often characterized along three dimensions: (i) cognitive perspective-taking, defined as the ability to infer the thoughts or beliefs of another agent; (ii) affective perspective-taking, defined as the ability to infer the emotions or feelings of another agent [START_REF] Healey | Cognitive and Affective Perspective-Taking: Evidence for Shared and Dissociable Anatomical Substrates[END_REF]; iii) visuo-spatial perspective-taking, defined as the ability to understand the visuo-spatial experience of another agent [START_REF] Proulx | Where am I? Who am I? The Relation Between Spatial Cognition, Social Cognition and Individual Differences in the Built Environment[END_REF]. Cognitive, affective and visuo-spatial perspective-taking are all thought to interact in order to contribute to social cognition [START_REF] Hamilton | Perspective taking: Building a neurocognitive framework for integrating the "social" and the "spatial[END_REF].

Perspective-taking refers to how an individual perceives or interprets incoming information but can also refer to how the information can be imagined or remembered from different perspectives. For example, studies on autobiographical memory showed that events from an individual's life can be remembered using different viewpoints. An event may be recalled from a first-person perspective (i.e. field mode) or from the perspective of an external observer (i.e., observer mode; [START_REF] Rice | I can see it both ways: First-and third-person visual perspectives at retrieval[END_REF][START_REF] Robinson | Field and observer modes of remembering[END_REF]. Interestingly, reliving past events from an external observer perspective decreases bilateral insula and somatic motor activity that are central for monitoring our bodies' internal states (i.e. interoception, [START_REF] Eich | Neural systems mediating field and observer memories[END_REF].

Interoception provides a key mechanism for the representation of the self and could therefore also be important for cognitive, affective and visual-spatial perspective-taking. Indeed, the strong links between exteroceptive and interoceptive processing, and the relationship between perspective-taking and the sense of body ownership [START_REF] Tsakiris | The multisensory basis of the self: from body to identity to others[END_REF] suggest a role of interoception in perspective-taking [START_REF] Palmer | Going at the heart of social cognition: is there a role for interoception in self-other distinction?[END_REF].

Recent studies have started to investigate the links between interoception and perspective-taking, however the extent to which these two multidimensional constructs interact remains unclear. Bringing together the disparate findings collected so far may be crucial to better understand how perceiving internal sensations may affect the ability to take another's point of view, at both the emotional, cognitive and visuo-spatial levels; and how this can be affected in different psychiatric disorders. The present review aims to provide an overview of the current research on interoception and the different dimensions of perspective-taking. The possible commonalities in the underlying neural mechanisms, as well as how both abilities can be impaired in the same clinical populations, is presented. Finally, suggestions for future avenues of research are discussed.

It should be underlined here that in the perspective-taking literature, terminology and operational definitions can differ when referring to the same construct, or different constructs can also share the same terminology. For example, the terms perspective-taking and Theory of Mind (ToM) are often used interchangeably. ToM is defined as a person's cognitive ability to understand another person's mental states, such as thoughts, beliefs, desires and intentions (Happé et al., 2017), and requires both cognitive and affective perspective-taking abilities [START_REF] Hynes | Differential role of the orbital frontal lobe in emotional versus cognitive perspective-taking[END_REF]. Furthermore, there is a distinction between cognitive and affective empathy [START_REF] Zaki | The neuroscience of empathy: progress, pitfalls and promise[END_REF]. While affective empathy refers to the ability to adopt the emotional experience of others, cognitive empathy corresponds to the ability to understand what another agent feels [START_REF] Healey | Cognitive and Affective Perspective-Taking: Evidence for Shared and Dissociable Anatomical Substrates[END_REF]. Both cognitive and affective empathy require perspective-taking abilities, but the main difference between the two processes is that affective empathy not only concerns emotion recognition but also adopting another person's emotion [START_REF] Healey | Cognitive and Affective Perspective-Taking: Evidence for Shared and Dissociable Anatomical Substrates[END_REF].

Table 1

Characteristics of the studies investigating the links between interoception and perspective-taking, highlighting which dimensions of perspective-taking were investigated and which perspective-taking and interoceptive tasks were used. 1. Davis, 1983;2. Reniers et al., 2011;3. Baron-Cohen et al., 2001;4. Santiesteban et al., 2012;5. Dziobek et al., 2006;6. Dziobek et al., 2008;7. Baron-Cohen and Wheelwright, 2004;8. Parsons, 1987;9. Matsumoto and Ekman, 1988;10. Kaiya, 2009;11. Taylor et al., 1985;12. Terasawa et al., 2014;13. Kessler and Thomson, 2010;14. Schandry, 1981;15. Dunn et al., 2010;16. Aspell et al., 2013;17. Mehling et al., 2012. Due to the close similarity in the definition and in order to simplify the terminology, in this review, the term 'affective perspective-taking' is used to refer to affective empathy as well. A recent review concluded that empathy and 'cognitive perspective-taking' recruit distinct neural circuits and can be distinguished from each other even early during development and across the life span [START_REF] Stietz | Dissociating Empathy From Perspective-Taking: Evidence From Intra-and Inter-Individual Differences Research[END_REF] highlighting the need to dissociate empathy from the cognitive mechanisms of understanding others (i.e. 'cognitive perspective-taking').

The literature search was performed up to June 2021. Given the multitude of terminology used in the field, the search included terms associated with the different dimensions of perspective-taking (i.e. cognitive, affective and visuo-spatial) and interoception (i.e. interoceptive accuracy, interoceptive sensibility, interoceptive awareness), as well as empathy and ToM. This search was supplemented by manual searches of reference lists cited in the original and review articles. Only reports published in English were included. The final reference list was generated on the basis of relevance to the topics covered in this review. Characteristics of the studies found in this search are reported in Table 1.

The role of interoception in perspective-taking

Interoception, cognitive and affective perspective-taking

Interoception is thought to be involved in emotion processing as the physiological condition of the body may act as the basic substrate for feeling states and emotions [START_REF] Bechara | The somatic marker hypothesis: a neural theory of economic decision[END_REF]. In support of this hypothesis, functional neuroimaging studies have highlighted areas of overlap between the neural substrates of emotion and interoception [START_REF] Critchley | Interoception and emotion[END_REF]. Moreover, a possible link between interoceptive processing, affective (i.e. empathy) and cognitive (i.e. ToM) perspective-taking has been hypothesized.

Studies have investigated the role of interoception in empathy, both at the affective and cognitive levels. [START_REF] Terasawa | Interoceptive senstivity predcits sensitivity to the emotions of others[END_REF] examined whether interoception [measured by the heartbeat counting task [START_REF] Schandry | Heart beat perception and emotional experience[END_REF], followed by a time estimation task as a control] modulated emotional experience by using morphed facial expressions. In the task, participants saw morphed photos with the following facial expressions: angry, sad, disgusted, happy. They were asked to choose the most appropriate option for the emotion that had been elicited by the stimulus. Results indicated that participants with higher interoceptive accuracy were more sensitive to the emotions of others, especially for expressions of sadness. Furthermore, the false identification of sad faces was related to social anxiety. [START_REF] Grynberg | Perceiving one's body shapes empathy[END_REF] investigated whether interoception shapes affective and cognitive empathy for pain and other forms of affective responses in a sample of healthy participants. In that study, one hundred pictures showing both painful and non-painful situations were used. Participants had to: (i) report the valence of their feelings and the degree of arousal they felt in response to the person in pain or non-pain situations; (ii) estimate how painful the depicted situation was; (iii) rate how compassionate and how distressed they felt in response to the person in pain or non-pain depicted in the picture. Interoception was measured by using a heartbeat counting task [START_REF] Schandry | Heart beat perception and emotional experience[END_REF]. Higher interoceptive accuracy was associated with higher ratings of the intensity of the person's pain (cognitive empathy), with higher reports of compassion (affective empathy) and arousal, but not with distress, in response to painful pictures. According to the authors, these results are in line with reports of higher arousal in response to emotional stimuli in good heartbeat perceivers (i.e. high interoceptive accuracy; see also [START_REF] Pollatos | Heart rate response after emotional picture presentation is modulated by interoceptive awareness[END_REF]. However, [START_REF] Ainley | Heartfelt empathy? No association between interoceptive awareness, questionnaire measures of empathy, reading the mind in the eyes task or the director task[END_REF] reported contrasting results. Interoception was similarly measured using a heartbeat counting task, however no significant associations between interoception and empathy (both at the cognitive and affective levels) were found. These contrasting findings may be due to the fact that [START_REF] Terasawa | Interoceptive senstivity predcits sensitivity to the emotions of others[END_REF] and [START_REF] Grynberg | Perceiving one's body shapes empathy[END_REF] differentiate empathy linked to specific emotional states (e.g. pain, sadness), which was not done in [START_REF] Ainley | Heartfelt empathy? No association between interoceptive awareness, questionnaire measures of empathy, reading the mind in the eyes task or the director task[END_REF]. Thus, it might be the case that the link between interoception and empathy is stronger for specific emotional states (e.g. sadness and pain). To further investigate this hypothesis, Dirupo and colleagues (2020) studied whether individual interoceptive abilities influence the ability to understand another's affective state. In that study, participants watched video-clips of naturalistic facial expressions in response to painful (thermal) and disgusting (olfactory) events. Participants were required to classify the videoclips according to the emotional state they induce (pain, disgust, neutral) and to rate the unpleasantness felt by the person in the video. IAcc was measured with a heartbeat counting task [START_REF] Schandry | Heart beat perception and emotional experience[END_REF] and confidence ratings about their estimation (i.e. interoceptive awareness). Subsequently, participants underwent a control task to account for potential confounds related to personal beliefs about one's cardiac response and time estimation [START_REF] Desmedt | Contribution of Time Estimation and Knowledge to Heartbeat Counting Task Performance under Original and Adapted Instructions[END_REF]. Individuals with higher IAcc were more likely to judge facial expressions as more unpleasant. However, when asked to discriminate between pain and disgust, participants' performance was not influenced by their interoceptive abilities. Overall, this study supports the view from embodied accounts that interoception promotes individual receptivity to others' affect, especially with unpleasant emotions.

Studies on interoception and cognitive perspective-taking have focused on identifying how processing of internal visceral and autonomic information (interoception) could contribute to the understanding of another's intentions. [START_REF] Ondobaka | The role of interoceptive inference in theory of mind[END_REF] proposed that knowledge of the interoceptive causes of our own behaviour (motor and autonomic) helps us predict and infer another's behaviour (i.e. ToM). From the active inference perspective, the authors suggest that knowing the contents of another's mind could also be demystified based on the behaviour that we would have produced in a similar situation. These hypotheses were based on the 'Predictive Coding' framework, according to which the brain generates hypotheses about the world and tests their predictive validity against incoming sensory evidence [START_REF] Friston | A theory of cortical responses[END_REF]. [START_REF] Ondobaka | The role of interoceptive inference in theory of mind[END_REF] therefore proposed that not only are our own mental states inferred from interoceptive states, but also that understanding another's mental states (ToM) entails interoceptive predictions. In line with this framework, [START_REF] Shah | From heart to mind: Linking interoception, emotion, and theory of mind[END_REF] tested whether interoceptive accuracy predicts performance on the representation of mental states in general, or if it is linked only to those situations in which understanding emotion is crucial for accurate mental state representation. A sample of healthy participants completed the Movie for the Assessment of Social Cognition (MASC, [START_REF] Dziobek | Introducing MASC: a movie for the assessment of social cognition[END_REF] in which they watched a social event requiring accurate mental state inferences to understand the story. Performance was quantified separately for questions requiring representation of another's emotion (e.g., "What is Sandra feeling?") and for those which did not require the representation of emotional states (e.g., "What is Michael thinking?"). Interoceptive accuracy was assessed with the Heartbeat counting task [START_REF] Schandry | Heart beat perception and emotional experience[END_REF] followed by a time estimation task as a control measure. Results showed that greater interoceptive accuracy was associated with better performance on items requiring the representation of another's emotion, but not when representation of emotional states was not required. These findings thus suggest that interoception contributes to accurate representation of mental states in situations where this process is reliant upon emotional information. However, interoception seems to be not strictly necessary for the representation of mental states per se.

Recently, von Mohr et al. ( 2019) went one step further and investigated how cardiac interoceptive accuracy modulates the tendency to use one's own emotional state when judging the emotional state of others (emotional egocentricity bias); as well as how manipulating the presentation of affective stimuli across different phases of the cardiac cycle (cardiac interoceptive impact) influences this relationship. Results showed that healthy participants with higher interoceptive accuracy displayed an increased emotional egocentricity bias when another's emotional state was presented at the point of maximum interoceptive impact (i.e., at systole, [START_REF] Garfinkel | Fear from the heart: sensitivity to fear stimuli depends on individual heartbeats[END_REF], whereas the opposite effect was observed for individuals with lower interoceptive accuracy. Taken together, these findings are in line with the hypothesis that individuals with lower interoceptive accuracy are more likely to switch to another person's emotional perspective given their tendency to blur self-other boundaries [START_REF] Palmer | Going at the heart of social cognition: is there a role for interoception in self-other distinction?[END_REF]. Therefore, interoception may be more relevant for emotional aspects of social cognition which influence the ability to empathise with others.

Interoception and visuo-spatial perspective-taking

In addition to the emotional aspects linked to understanding another's perspective, interoception may also shape the ability to distinguish between one's own and another's visualspatial perspective. Visuo-spatial perspective-taking (VPT) has been described as the ability to understand the visuo-spatial and mental experience of another agent [START_REF] Proulx | Where am I? Who am I? The Relation Between Spatial Cognition, Social Cognition and Individual Differences in the Built Environment[END_REF]. VPT is often characterized as having two levels [START_REF] Flavell | Young children's knowledge about visual perception: Further evidence for the Level 1-Level 2 distinction[END_REF]: (i) level-1 VPT is the ability to understand that another agent can see things differently compared to one's own point of view; (ii) level-2 VPT is the ability to judge what a visual scene looks like from another's point of view. Level-1 VPT can involve implicit, automatic processing of a target's perspective as well as effortful and controlled ascription of a target's mental state [START_REF] Todd | Dissociating processes underlying level-1 visual perspective taking in adults[END_REF]. Level-2 VPT is thought to be an embodied process during which the perspective-taker mentally simulates a movement of his or her body into the location of the target [START_REF] Kessler | The Two Forms of Visuo-Spatial Perspective Taking are Differently Embodied and Subserve Different Spatial Prepositions[END_REF][START_REF] Surtees | Similarities and differences in visual and spatial perspective-taking processes[END_REF]. VPT processes are differently used depending on the tasks and goals at hand. In particular, some underlying VPT mechanisms allow us to transform our perspective to describe the visuospatial aspects of a scene perceived from a different viewpoint, while others allow us to compute the line of sight of a third agent [START_REF] Michelon | Two kinds of visual perspective taking[END_REF].

The first study investigating the potential relationship between VPT and interoceptive accuracy used a level-1 VPT task [START_REF] Ainley | Heartfelt empathy? No association between interoceptive awareness, questionnaire measures of empathy, reading the mind in the eyes task or the director task[END_REF], assessing the ability to understand what another can and cannot see. This task, named the "Director Task" [START_REF] Santiesteban | Training social cognition: From imitation to theory of mind[END_REF], requires participants to move objects around a grid of shelves according to verbal instructions from a 'Director'. Sometimes, the grid display affords two competing perspectives: the participants' viewpoint from the front of the display differs from the Director's vantage point from the rear. Under these conditions, the participants must ignore their own self-perspective and act according to their inference of the Director's perspective. Interoceptive accuracy was assessed using the heartbeat counting task [START_REF] Schandry | Heart beat perception and emotional experience[END_REF]. Contrary to their expectations, [START_REF] Ainley | Heartfelt empathy? No association between interoceptive awareness, questionnaire measures of empathy, reading the mind in the eyes task or the director task[END_REF] did not find any associations between interoceptive accuracy and the results obtained in the Director task.

The possible relationships between interoceptive accuracy, level-1 VPT and other dimensions of perspective-taking were investigated by [START_REF] Shaw | You ≠ me: individual differences in the structure of social cognition[END_REF]. Similarly to [START_REF] Ainley | Heartfelt empathy? No association between interoceptive awareness, questionnaire measures of empathy, reading the mind in the eyes task or the director task[END_REF], level-1 VPT was assessed using the "Director Task" [START_REF] Santiesteban | Training social cognition: From imitation to theory of mind[END_REF] and interoceptive accuracy was investigated with the heartbeat counting task [START_REF] Schandry | Heart beat perception and emotional experience[END_REF]. Structural equation modelling analysis showed that a hierarchical pattern of relationships among various components of social cognition (e.g., self-other distinction and visual perspective-taking) may influence socioemotional processes (e.g., affective empathy, emotion regulation and interoception). However, no direct associations between level-1 VPT and interoception were found. Furthermore, Erle (2019) investigated how interoception is related to a level-2 VPT test, assessing the ability to understand how someone else sees things. Participants completed a behavioural level-2 VPT task in which they saw a person (the "target") sitting at a table with two objects on a computer screen. They had to mentally "grab" one of the objects from the target's perspective, using two response keys. Interoceptive accuracy was quantified by the heartbeat counting task [START_REF] Schandry | Heart beat perception and emotional experience[END_REF]. Moreover, interoceptive sensibility was measured by the subjective confidence in the estimated number of heartbeats. Faster VPT performance was related to higher interoceptive accuracy but was unrelated to interoceptive sensibility. Thus, the relationship between interoception and non-emotional forms of perspectivetaking appears to be more controversial. Some findings suggest that interoceptive accuracy is not related to understanding the non-emotional contents of another's thoughts [START_REF] Shah | From heart to mind: Linking interoception, emotion, and theory of mind[END_REF] or to ignoring one's own visual point of view in favor of another's [START_REF] Ainley | Heartfelt empathy? No association between interoceptive awareness, questionnaire measures of empathy, reading the mind in the eyes task or the director task[END_REF]. However, other findings [START_REF] Erle | Level-2 visuo-spatial perspective-taking and interoception -More evidence for the embodiment of perspective-taking[END_REF] suggest that visual perspective-taking is indeed related to interoceptive accuracy, supporting an embodied cognition account of visual perspective-taking. The disparate findings may relate to the requirement of level-1 vs. level-2 perspective-taking in the tasks used. The task of [START_REF] Ainley | Heartfelt empathy? No association between interoceptive awareness, questionnaire measures of empathy, reading the mind in the eyes task or the director task[END_REF] as well as [START_REF] Shaw | You ≠ me: individual differences in the structure of social cognition[END_REF] assessed level-1 perspective-taking, while Erle (2019) measured level-2 perspective-taking. Only level-2 perspective-taking is thought to be an embodied process, which suggests that interoceptive processes may interact with perspective-taking only when there is a requirement to engage in embodied transformations of one's body in space (i.e. imagined self-rotation).

More recently, [START_REF] Heydrich | Interoception and Empathy Impact Perspective Taking[END_REF] investigated how embodied transformations of one's body are influenced by interoceptive cues as well as empathic abilities. A cardio-visual paradigm [START_REF] Aspell | Turning body and self inside out: visualized heartbeats alter bodily self-consciousness and tactile perception[END_REF] was used to assess whether VPT abilities are affected by systematic manipulations of interoceptive cues as well as an individual's empathic ability. In an adapted version of the own-body transformation task, participants were instructed to mentally adopt the perspective and position of a virtual body presented on a computer screen (see [START_REF] Parsons | Imagined spatial transformation of one's body[END_REF]. The virtual body was surrounded by a flashing silhouette which appeared either synchronously or asynchronously with the timing of participants' heartbeats. Participants with high empathy had better performance in the VPT task during synchronous versus asynchronous cardio-visual stimulation. Moreover, empathy was positively associated with the difference in reaction times between the asynchronous and synchronous conditions (i.e. the synchrony effect). These results suggest that synchronous cardio-visual stimulation facilitates adopting the virtual body's perspective. Moreover, this effect was influenced by empathy (i.e. affective perspective-taking), thus suggesting that interoception and both emotional and nonemotional perspective-taking abilities are strongly linked.

Do interoception and perspective-taking share neural correlates?

In a meta-analysis of functional Magnetic Resonance Imaging (fMRI) studies of cardiac interoception, Schulz (2016) corroborated the involvement of an extended network including the posterior right and left insula, right claustrum, precentral and medial frontal gyri. Functional neuroimaging data also indicate that the anterior insula could represent a hub between brain networks involved in externally directed attention to stimuli in the environment and internally directed attention to one's body [START_REF] Menon | Saliency, switching, attention and control: a network model of insula function[END_REF]. Thus, the anterior insula could not only be an area of body awareness, but it may mediate representations of the outside world and the body's internal state [START_REF] Farb | Attentional modulation of primary interoceptive and exteroceptive cortices[END_REF]. Moreover, a right-hemispheric dominance of interoceptive processing has been reported, with the posterior insula presumably serving as the major gateway for cardiac interoception [START_REF] Critchley | Neural systems supporting interoceptive awareness[END_REF]. In particular, the posterior insula first supports the convergence of sensory and affective signals about the body that are then represented in the mid and anterior insula, which integrate interoceptive information with other contextual information [START_REF] Critchley | Neural systems supporting interoceptive awareness[END_REF][START_REF] Evrard | Insular cortex[END_REF]. The anterior insula-cingulate network is also credited with the specific function of self-recognition [START_REF] Devue | Here I am: the cortical correlates of visual self-recognition[END_REF]) and it is crucial for integrating all subjective feelings related to the body, especially to its homeostatic conditions, into emotional experiences and conscious awareness of the environment and the self [START_REF] Craig | How do you feel--now? The anterior insula and human awareness[END_REF].

Regarding perspective-taking, studies on functional lateralization emphasize the importance of right temporo-parietal junction (TPJ) activation in ToM tasks (e.g. [START_REF] Saxe | Making sense of another mind: The role of the right temporoparietal junction[END_REF]. Furthermore, [START_REF] Wang | Rhythm makes the world go round: An MEG-TMS study on the role of right TPJ theta oscillations in embodied perspective taking[END_REF] concluded that the right TPJ is a crucial network hub for transforming the embodied self into another's viewpoint. However, [START_REF] Jenkins | Mentalizing under uncertainty: Dissociated neural responses to ambiguous and unambiguous mental state inferences[END_REF] reported bilateral activation of the TPJ and [START_REF] Santiesteban | Functional lateralization of temporoparietal junction -imitation inhibition, visual perspective-taking and theory of mind[END_REF] reported a bilateral TPJ involvement in a MEG-TMS study. Thus, the functional lateralization of perspective-taking is not well defined. Moreover, the TPJ is a multimodal cortical region, receiving inputs from thalamic, limbic, somatosensory, visual and auditory areas [START_REF] Bzdok | Characterization of the temporo-parietal junction by combining data-driven parcellation, complementary connectivity analyses, and functional decoding[END_REF]. Transient changes in brain activity locked to heartbeats (Heartbeat-evoked potentials, HEPs) can also provide information about the mechanisms of self-other distinction. To test the hypothesis that an internal mechanism based on the neural monitoring of heartbeats could distinguish between self and another, [START_REF] Babo-Rebelo | Neural responses to heartbeats distinguish self from other during imagination[END_REF] showed that the amplitude of heartbeat-evoked responses, in the precuneus and bilateral mid/posterior cingulate regions, differed between imagining oneself and imagining a friend [START_REF] Babo-Rebelo | Neural responses to heartbeats distinguish self from other during imagination[END_REF]. Furthermore, neural responses to heartbeats in the posterior cingulate cortex were found to vary with changes in bodily self-consciousness induced by a body illusion (Park and Tallon-Baudry, 2014).

To date, few studies have simultaneously investigated a possible relationship between the neural correlates of interoception and perspective-taking. In [START_REF] Ernst | Interoceptive Awareness Enhances Neural Activity During Empathy[END_REF], the participants had to judge if they could empathize with pictures showing facial expressions. Completing an interoceptive accuracy task before an empathy task significantly enhanced neural activity of the bilateral anterior insula, anterior and posterior midline regions such as the cingulate cortex and the precuneus, suggesting a close relationship between interoception and empathy. However, the empathy task used by the authors did not assess the ability to understand what another agent feels, but it required participants to judge if they could empathize with pictures of facial expressions. Recently, Stoica and Depue (2020a) found that resting-state fMRI spatial connectivity and temporal variability data were correlated with participants' self-reported empathy levels and interoceptive sensibility. Interestingly, improved processing between brain regions part of the 'salience network' (e.g. anterior insula, anterior midcingulate cortex) was related to an improved ability to take someone's perspective. Stoica and Depue (2020b) also investigated which dimension of empathy (i.e. cognitive or affective) shared resting-state functional connectivity with self-reported interoceptive sensibility (as defined by [START_REF] Garfinkel | Knowing your own heart: Distinguishing interoceptive accuracy from interoceptive awareness[END_REF]. They found that affective empathy and interoceptive sensibility were inversely related to increased resting-state functional connectivity within the right inferior frontal operculum, and also inversely related to blood oxygenation variability between brain regions of an interoceptive network. On the other hand, cognitive empathy and interoceptive sensibility shared only blood oxygenation variability. According to the authors their results suggest a relation between the ability to feel and understand another's emotional state and one's awareness of or sensibility towards internal body changes, which is reflected in the brain's intrinsic neuroarchitecture.

Studies of stroke patients can also help to better understand the possible overlap between the neural networks involved in interoception and perspective-taking. Impaired performance on a task of interoceptive accuracy correlated with damage to the left anterior cingulate cortex and fronto-insular cortex in patients with non-hemorrhagic fronto-insular stroke (Garcìa-Cordero et al., 2016). Similarly, lower scores on an interoceptive sensibility questionnaire were associated with insula lesions and its connections to the amygdala and putamen [START_REF] Grossi | The brain network for self-feeling: a symptom-lesion mapping study[END_REF]. Lesions of the posterior insula, inferior and middle frontal gyri and of dorsal frontal white matter were also associated to impaired performance in cognitive (i.e. ToM) and visual perspective-taking tasks in patients with anosognosia for hemiplegia following right-hemisphere strokes [START_REF] Besharati | Mentalizing the body: spatial and social cognition in anosognosia for hemiplegia[END_REF]. A recent study by [START_REF] Terasawa | Effects of insular resection on interactions between cardiac interoception and emotion recognition[END_REF] examined the change in interoception and emotion after insular resection and found that removal of the insula affects the recognition of emotions such as anger and happiness through interoceptive processing. However, no lesion study to date has investigated the possible interconnection between interoceptive and perspective-taking networks. Some evidence with healthy participants has shown that performing an interoceptive accuracy task increases cortical activity in areas associated with empathy (i.e. the anterior insula and the anterior cingulate cortex; [START_REF] Ernst | Interoceptive Awareness Enhances Neural Activity During Empathy[END_REF] and the TPJ is functionally connected to the insular cortex [START_REF] Araujo | Neural correlates of different self domains[END_REF][START_REF] Kucyi | Hemispheric asymmetry in white matter connectivity of the temporoparietal junction with the insula and prefrontal cortex[END_REF]. Studies specifically examining brain damage and its ensuing effects on both interoception and perspective-taking are necessary in order to determine crucial networks involved in both processes.

Interoceptive and perspective-taking specificities in clinical populations

Interoceptive and perspective-taking abilities may be simultaneously impaired in many psychiatric, neurodevelopmental and neurodegenerative conditions, but no study to date has investigated the impact of these two constructs together in clinical samples.

For example, there is a growing interest in interoceptive alterations in anxiety disorders as well as in trait anxiety (for a review see [START_REF] Paulus | Interoception in anxiety and depression[END_REF]. Most studies of trait anxiety reported an association between higher cardiac interoceptive accuracy and higher levels of anxiety assessed with self-reported questionnaires [START_REF] Domschke | Interoceptive sensitivity in anxiety and anxiety disorders: an overview and integration of neurobiological findings[END_REF]. Moreover, interoceptive accuracy, assessed with the Heartbeat Discrimination Task [START_REF] Whitehead | Relation of heart rate control to heartbeat perception[END_REF], was positively associated with individual trait anxiety and other related traits such as negative affect, emotional intensity, introversion and behavioural inhibition [START_REF] Lyyra | Behavioral Inhibition Underlies the Link Between Interoceptive Sensitivity and Anxiety-Related Temperamental Traits[END_REF].

A recent study (Palser et al., 2018a) found that the positive association between interoceptive sensibility and trait anxiety was partially mediated by alexithymia, a personality trait characterized by a subclinical difficulty in identifying and describing one's own emotions [START_REF] Nemiah | Alexithymia: a view of the psychosomatic process[END_REF]. Therefore, those most at risk for clinically significant levels of trait anxiety have both significantly higher levels of interoceptive sensibility and alexithymia. It has been also hypothesized that trait anxiety may influence empathic responses with an inverse relationship between empathy and anxiety, as empathy requires sensitivity to another's needs, while anxiety may be more associated with self-focused worry [START_REF] Deardorff | Empathy, locus of control and anxiety in college students[END_REF]. In line with this, [START_REF] Negd | The role of anxiety and perspective-taking strategy on affective empathic responses[END_REF] experimentally induced anxiety through an unpleasant electrotactile stimulus and found that it was associated with decreased empathy-related feelings.

Similar results were found for level-1 visual perspective-taking, where experiencing anxiety impaired the spontaneous calculation of what another social agent can see [START_REF] Todd | Anxiety impairs spontaneous perspective calculation: Evidence from a level-1 visual perspective-taking task[END_REF]. Similarly, adolescents with higher social anxiety traits were less accurate at taking another's perspective in the Director Task [START_REF] Santiesteban | Training social cognition: From imitation to theory of mind[END_REF] compared to those with low social anxiety traits [START_REF] Pile | Young people with higher social anxiety are less likely to adopt the perspective of another: Data from the Director task[END_REF]. A strong grounding in one's natural spatial perspective was also found to be associated with lower interpersonal anxiety and higher social intelligence [START_REF] Job | Spatial perspective taking is related to social intelligence and attachment style[END_REF]. Together these findings suggest that trait anxiety could be associated with higher levels of interoception and an impaired ability to take another person's point of view. However, studies on anxiety disorders including generalized anxiety disorder, panic disorder, social anxiety, specific phobias and agoraphobia showed findings as heterogeneous as the differentiation of anxiety conditions [START_REF] Domschke | Interoceptive sensitivity in anxiety and anxiety disorders: an overview and integration of neurobiological findings[END_REF]. For example, anxiety disorder patients who experienced panic attacks, did not show differences in interoceptive accuracy compared with healthy controls but exhibited more worries and catastrophic thoughts about somatic sensations [START_REF] Yoris | The roles of interoceptive sensitivity and metacognitive interoception in panic[END_REF]. No evidence for higher interoceptive accuracy was found in patients with pathological health anxiety either [START_REF] Krautwurst | Interoception in pathological health anxiety[END_REF].

Dysfunctional perspective-taking abilities in anxiety disorders were found for cognitive and affective perspective-taking [START_REF] Hezel | Theory of mind impairments in social anxiety disorder[END_REF]. [START_REF] Tone | Empathy as a "risky strength": a multilevel examination of empathy and risk for internalizing disorders[END_REF] proposed a model in which an excessive empathic sensitivity, together with interpersonal guilt, contributed to increased risk of developing internalizing psychiatric disorders, such as anxiety. Moreover, a study on autobiographical memory showed that individuals with social anxiety are more likely to take an external observer perspective compared to control participants when recalling anxious situations (Wells and [START_REF] Papageorgiou | Process and meta-cognitive dimensions of depressive and anxious thoughts and relationships with emotional intensity[END_REF], in line with the view that social phobics are prone to generating negative impressions of how they appear to others. Taking an external observer perspective in recalling past events is also associated with insular deactivation, a key area for interoceptive processing [START_REF] Eich | Neural systems mediating field and observer memories[END_REF]Craig et al., 2002). However, no studies to date have investigated the possible alteration of visual perspectivetaking in anxiety, so this deserves further investigation.

Changes in affective, cognitive and visual perspective-taking have been found in Autism Spectrum Disorders (ASD; [START_REF] Harmsen | Empathy in Autism Spectrum Disorder[END_REF][START_REF] Conson | Put Myself Into Your Place": Embodied Simulation and Perspective Taking in Autism Spectrum Disorders[END_REF][START_REF] Cardillo | Spatial Perspective-Taking in Children With Autism Spectrum Disorders: The Predictive Role of Visuospatial and Motor Abilities[END_REF]. ASD is a neurodevelopmental condition characterized by lifelong difficulties in social and emotional functioning with restricted and stereotyped patterns of behaviour, interests and activities [START_REF] Frith | The neural basis of mentalizing[END_REF]. Recent studies suggested that interoceptive abilities are impaired in both autistic children and adults (Palser et al., 2018b;[START_REF] Garfinkel | Discrepancies between dimensions of interoception in autism: Implications for emotion and anxiety[END_REF]. Specifically, [START_REF] Garfinkel | Discrepancies between dimensions of interoception in autism: Implications for emotion and anxiety[END_REF] found a dissociation between a reduced interoceptive accuracy (quantified using heartbeat counting and detection tasks) and an exaggerated interoceptive sensibility (subjective sensitivity to internal sensations measured with self-report questionnaires) in ASD participants. Interestingly, socio affective ASD features appeared to be related to interoceptive sensibility, while repetitive restricted behaviors to interoceptive accuracy in ASD children [START_REF] Palser | Dissociation in How Core Autism Features Relate to Interoceptive Dimensions: Evidence from Cardiac Awareness in Children[END_REF]. Moreover, a lower interoceptive accuracy was related to autistic traits, lower empathy and alexithymia in a sample of autistic adults compared to those with typical development [START_REF] Mul | The Feeling of Me Feeling for You: Interoception, Alexithymia and Empathy in Autism[END_REF].

Disturbed interoceptive and perspective-taking abilities can also be found in some neurodegenerative disorders. For example, lower performance on interoceptive accuracy tasks was found in non-demented Parkinson's disease patients [START_REF] Ricciardi | Know thyself: Exploring interoceptive sensitivity in Parkinson's disease[END_REF][START_REF] Santangelo | Interoceptive processing deficit: A behavioral marker for subtyping Parkinson's disease[END_REF]). Parkinson's disease is characterized by a large spectrum of non-motor symptoms ranging from cognitive to behavioural disturbances [START_REF] Chaudhuri | Non-motor symptoms of Parkinson's disease: diagnosis and management[END_REF]. Alterations of affective and cognitive perspective-taking (i.e. empathy and ToM) are typically reported in Parkinson's disease patients (for a meta-analysis see [START_REF] Coundouris | Empathy and theory of mind in Parkinson's disease: A meta-analysis[END_REF], but no study to date investigated a possible dysfunction of visual perspective-taking.

Finally, interoceptive dysfunctions have been reported in anorexia nervosa and other body image disturbances (for a review see [START_REF] Badoud | From the body's viscera to the body's image: Is there a link between interoception and body image concerns?[END_REF]. For example, [START_REF] Pollatos | Normal interoceptive accuracy in women with bulimia nervosa[END_REF] demonstrated a link between reduced IAcc and negative body image (i.e. higher body dissatisfaction) in anorexic patients; while [START_REF] Khalsa | Altered interoceptive awareness in anorexia nervosa: Effects of meal anticipation, consumption and bodily arousal[END_REF] suggested that in anorexia nervosa there is a dysregulated ability to adequately predict and cognitively represent and regulate what is happening in the physiological state of the body. Anorexia nervosa is also characterized by cognitive perspective-taking deficits that can contribute to poor insight, treatment resistance, and social impairment [START_REF] Bora | Meta-analysis of theory of mind in anorexia nervosa and bulimia nervosa: A specific İmpairment of cognitive perspective taking in anorexia nervosa?[END_REF]. However, many inconsistent findings remain, and no study to date investigates both deficits simultaneously.

Taken together, the circumstantial evidence to date suggests the need to directly investigate the common processes and neural mechanisms underlying the various dimensions of interoception and perspective-taking in non-clinical as well as in clinical populations.

Areas of investigation and future perspectives

The aim of this review was to clarify how the perception of signals originating from within the body (i.e. interoception) underlies different levels of perspective-taking and to provide new perspectives about the embodied nature of the two processes. A summary graphic of the possible interactions between dimensions of interoception and perspective-taking is shown in Figure 1. Interoceptive abilities appear to be closely connected to affective aspects of perspective-taking (e.g. empathy, [START_REF] Dirupo | The role of interoception in understanding others' affect. Dissociation between superficial and detailed appraisal of facial expressions[END_REF][START_REF] Grynberg | Perceiving one's body shapes empathy[END_REF][START_REF] Shah | From heart to mind: Linking interoception, emotion, and theory of mind[END_REF]Terasawa et al., 2015). The perception of internal signals appears to be associated with a greater ability to share and understand another person's emotional states (i.e. empathy).

In particular, greater interoceptive accuracy appears to be linked to empathy for specific emotional states, such as pain, sadness or disgust [START_REF] Dirupo | The role of interoception in understanding others' affect. Dissociation between superficial and detailed appraisal of facial expressions[END_REF][START_REF] Grynberg | Perceiving one's body shapes empathy[END_REF]. Regarding cognitive perspective-taking (e.g. ToM), the ability to infer the mental states of others appears to be biased in individuals with higher interoceptive accuracy (von Mohr et al., 2019). This is in line with the hypothesis that individuals with higher interoceptive accuracy may be less able to update beliefs about another person's emotional state given their stronger perceived boundaries between internal states and the external world [START_REF] Palmer | Going at the heart of social cognition: is there a role for interoception in self-other distinction?[END_REF].

An involvement of interoceptive processes in visual perspective-taking is largely unknown, with only one study [START_REF] Erle | Level-2 visuo-spatial perspective-taking and interoception -More evidence for the embodiment of perspective-taking[END_REF] identifying a significant relationship. More efficient level-2 visual perspective-taking could be linked to higher interoceptive accuracy as both are embodied processes. Thus, the ability to perceive one's own body from within (IAcc) might benefit from the ability to distinguish between one's own and another's visual perspective. Moreover, [START_REF] Heydrich | Interoception and Empathy Impact Perspective Taking[END_REF] suggested that interoception and both emotional and nonemotional aspects of perspective-taking are strongly linked, suggesting that perspective-taking strongly depends on the activation of multisensory signals from one's own body. The functional interactions between neural networks related to interoception (e.g. insular and cingulate cortex) and perspective-taking (e.g. bilateral TPJ) could also support the abovementioned hypothesis.

Links between interoception and perspective-taking can also be found in studies with clinical populations. For example, high interoception was found to be positively associated with levels of arousal and anxiety, which could be characterized by an excessive and maladaptive empathic sensitivity [START_REF] Tone | Empathy as a "risky strength": a multilevel examination of empathy and risk for internalizing disorders[END_REF]. Moreover, dysfunctions in both constructs might be also found in psychiatric, neurological and developmental disorders (e.g. Anorexia nervosa, Parkinson's disease, Autism Spectrum Disorders). This suggests that interoceptive training could have a positive impact on patients' quality of life, where an improved ability to represent the interoceptive states of oneself and of others could result in more accurate mental state inferences and in a better understanding of another's point of view (i.e. improved perspective-taking). However, direct evidence to support these assumptions is needed due to the lack of studies and poor consistency between them.

Several limitations can be highlighted. Firstly, most of the studies taken into account for this review used a unidimensional approach to assess interoceptive abilities. As suggested by [START_REF] Garfinkel | Knowing your own heart: Distinguishing interoceptive accuracy from interoceptive awareness[END_REF], a differentiation between objective, subjective and metacognitive aspects of interoception is needed. In fact, different dimensions of interoception may be independent and could contribute differently to cognitive and affective processes [START_REF] Garfinkel | Interoception, emotion and brain: new insights link internal physiology to social behaviour. Commentary on: "Anterior insular cortex mediates bodily sensibility and social anxiety[END_REF]. Currently, studies focusing on interoception and perspective-taking have exclusively used the heartbeat counting task as a measure of cardiac interoceptive accuracy [START_REF] Schandry | Heart beat perception and emotional experience[END_REF]. Only two studies [START_REF] Dirupo | The role of interoception in understanding others' affect. Dissociation between superficial and detailed appraisal of facial expressions[END_REF][START_REF] Erle | Level-2 visuo-spatial perspective-taking and interoception -More evidence for the embodiment of perspective-taking[END_REF] assessed confidence ratings in heartbeat counting task performance (to measure interoceptive awareness), without significant results.

Moreover, the validity of the heartbeat counting task was recently questioned [START_REF] Ring | Heartbeat counting is unrelated to heartbeat detection: A comparison of methods to quantify interoception[END_REF]. Participants may perform the task by estimating, rather than counting, their felt heartbeats or just estimate the seconds elapsed in the time intervals [START_REF] Desmedt | Contribution of Time Estimation and Knowledge to Heartbeat Counting Task Performance under Original and Adapted Instructions[END_REF]. Therefore, the need to use adequate control measures (e.g. time estimation) and adapted instructions has been recently highlighted [START_REF] Desmedt | Contribution of Time Estimation and Knowledge to Heartbeat Counting Task Performance under Original and Adapted Instructions[END_REF]. However, a time estimation control task was administered in only three of the studies presented in this review [START_REF] Dirupo | The role of interoception in understanding others' affect. Dissociation between superficial and detailed appraisal of facial expressions[END_REF][START_REF] Shah | From heart to mind: Linking interoception, emotion, and theory of mind[END_REF]Terasawa et al., 2015). Future studies should seek to address these criticisms as well as to include measures of all aspects of cardiac interoception.

Future studies should investigate further the relationships between interoception and spatial perspective-taking (defined broadly as the ability to understand where something is located relative to someone else, [START_REF] Surtees | Similarities and differences in visual and spatial perspective-taking processes[END_REF], including but not limited to visuo-spatial perspective-taking. Indeed, studies to date have focused on the visual domain, but one should also explore other modalities, such as touch. One potential avenue is to use the Graphesthesia task [START_REF] Arnold | Taking someone else's spatial perspective: Natural stance or effortful decentring?[END_REF][START_REF] Arnold | A unity of the self or a multiplicity of locations? How the graphesthesia task sheds light on the role of spatial perspectives in bodily selfconsciousness[END_REF], which provides an ideal tool to investigate the embodied nature of spatial perspective-taking, in the tactile domain.

A further possible link with embodiment might be found by investigating the role of the vestibular system in the relationship between interoception and perspective-taking. Recent studies highlighted the role of the vestibular system in multisensory integration and embodiment [START_REF] Lenggenhager | Vestibular contributions to the sense of body, self, and others[END_REF]. At a functional level, both vestibular and interoceptive systems provide information about self-motion and gravitational forces exerted on the body and both appear to be involved in emotional processes and our sense of a bodily self [START_REF] Nakul | Interoception and embodiment in patients with bilateral vestibulopathy[END_REF]. In particular, one study suggested a possible role of the vestibular system in the integration between interoceptive and exteroceptive information [START_REF] Ponzo | Balancing body ownership: Visual capture of proprioception and affectivity during vestibular stimulation[END_REF]. However, no difference has been found between patients with bilateral vestibulopathy and controls regarding interoceptive accuracy, confidence and body awareness [START_REF] Nakul | Interoception and embodiment in patients with bilateral vestibulopathy[END_REF]. Moreover, possible vestibular contributions to several sensorimotor bases of social cognition has been suggested, but they need further investigation [START_REF] Deroualle | Toward a vestibular contribution to social cognition[END_REF].

Finally, studies on non verbal self-referential processing, which includes somatic and inner bodily self-consciousness, suggested that the TPJ, together with the anterior insula and the extrastriate body area, plays a key role in embodiment and self-awareness [START_REF] Salgues | To the self and beyond: Arousal and functional connectivity of the temporoparietal junction contributes to spontaneous sensations perception[END_REF]. Interestingly, right posterior TPJ was found to be involved during emotional contexts requiring perspective-taking abilities, whereas a more anterior region seems to be involved during third-person perspective-taking in neutral contexts [START_REF] Frewen | Neuroimaging the consciousness of self: Review, and conceptual-methodological framework[END_REF][START_REF] Ruby | How would you feel versus how do you think she would feel? A neuroimaging study of perspective-taking with social emotions[END_REF]. For these reasons, future studies should also investigate the links between interoception and perspective-taking taking into account self-referential mechanisms.

In conclusion, the findings reviewed here highlight that interoception may be more relevant for emotional aspects of perspective-taking, which influence the ability to empathise with others. Despite the relatively few studies, a view is emerging that interoceptive information may be important for those aspects of perspective-taking that require embodied processes. These possible interactions have several implications for future research and clinical applications, such as the possibility to implement tailored interventions (e.g. biofeedback paradigms, [START_REF] Sugawara | Effects of interoceptive training on decision making, anxiety, and somatic symptoms[END_REF] with a positive impact on patients' quality of life.

Figure 1 .

 1 Figure 1. Schema of the possible links between interoception and perspective-taking (PT) taken from existing literature. The solid line indicates a strong relationship (Grymberg and Pollatos, 2015; Shah et al., 2017; Terasawa et al., 2015); the dashed lines indicate possible bonds that require further