Active self-touch restores bodily proprioceptive spatial awareness following disruption by 'rubber hand illusion'.

Bodily self-awareness relies on a constant integration of visual, tactile, proprioceptive, and motor signals. In the 'rubber hand illusion' (RHI), conflicting visuo-tactile stimuli lead to changes in self-awareness. It remains unclear whether other, somatic signals could compensate for the alterations in self-awareness caused by visual information about the body. Here, we used the RHI in combination with robot-mediated self-touch to systematically investigate the role of tactile, proprioceptive and motor signals in maintaining and restoring bodily self-awareness. Participants moved the handle of a leader robot with their right hand and simultaneously received corresponding tactile feedback on their left hand from a follower robot. This self-touch stimulation was performed either before or after the induction of a classical RHI. Across three experiments, active self-touch delivered after-but not before-the RHI, significantly reduced the proprioceptive drift caused by RHI, supporting a restorative role of active self-touch on bodily self-awareness. The effect was not present during involuntary self-touch. Unimodal control conditions confirmed that both tactile and motor components of self-touch were necessary to restore bodily self-awareness. We hypothesize that active self-touch transiently boosts the precision of proprioceptive representation of the touched body part, thus counteracting the visual capture effects that underlie the RHI.

[To experience one's physicality through the "bizarre" experience of touching oneself]. / Éprouver sa corporéité par l'expérience "bizarre" de se toucher.

The touch of oneself is essential in the construction of a conscious self. It contributes to the feeling of ownership of the body. Feeling touched and touching reveals the subject in a being-self inscribed in its environment. This sensory experience can be disturbing for the subject. A study conducted with adolescent girls with obesity has shown that this haptic experience, during a postural session, can generate a feeling of strangeness. This singular discovery of oneself reveals the opening towards new exploratory fields of the body self-consciousness, during our care.

The Perceived Match Between Observed and Own Bodies, but Not Its Accuracy, Is Influenced by Movement Dynamics and Clothing Cues.

Own-perceived body matching - the ability to match one's own body with an observed body - is a difficult task for both general and clinical populations. Thus far, however, own-perceived body matching has been investigated in situations that are incongruent with how we are used to experience and perceive our body in daily life. In the current study, we aimed to examine own-perceived body matching in a context that more closely resembles real life. More specifically, we investigated the effects of body movement dynamics and clothing cues on own-perceived body matching. We asked participants to match their own body with an externally perceived body that was a 3D-generated avatar based on participants' real bodies, fitted with a computer-generated dress. This perceived body was (1) either static (non-walking avatar) or dynamic (walking avatar), (2) either bigger, smaller, or the same size as participants' own body size, and (3) fitted with a dress with a size either bigger, smaller, or the same as participants' own dress size. Our results suggest that movement dynamics cues did not improve the accuracy of own-perceived body matching, but that confidence about dress fit was higher for dynamic avatars, and that the difference between dynamic and static avatars was dependent on participants' self-esteem. Furthermore, when participants were asked to rate the observed body in reference to how they wanted to represent themselves to others, dynamic avatars were rated lower than static avatars for the biggest-sized bodies only, possibly reflecting the influence of movement cues on amplifying socio-cultural stereotypes. Finally, while smaller body/dress sizes were systematically rated higher than bigger body/dress sizes for several self-report items, the interplay between body and dress size played an important role in participants' self-report as well. Thus, while our research suggests that movement and garment dynamics, allowing for realistic, concrete situations that are reminiscent of daily life, influence own-body perception, these cues did not lead to an improvement in accuracy. These findings provide important insights for research exploring (own-) body perception and bodily self-awareness, with practical (e.g., development of online avatars) and clinical (e.g., anorexia nervosa and body dysmorphic disorder) implications.

Neuropharmacological modulation of the aberrant bodily self through psychedelics.

As a continual source of sensory input and fundamental component of self-referential processing, the body holds an integral modulatory role in cognition. In a healthy state, predictive coding of multisensory integration promotes the construction of a coherent self. However, several psychiatric disorders comprise aberrant perceptions of the bodily self that are purported to involve discrepancies in the integration and updating of multisensory systems. Changes in functional connectivity of somatomotor and high-level association networks in these disorders could be successfully remediated through 5-HT2A receptor agonism via psychedelics. Reported alterations of bodily self-awareness during psychedelic experiences allude to a potentially central role of the bodily self. In this article, we bridge the domains of (aberrant) bodily self-awareness and psychedelics by discussing the predictive coding mechanisms underlying the bodily self and psychedelics. Furthermore, we propose that psychedelically-induced desynchronization of predictive coding might involve modulation of somatomotor, sensorimotor, and high-level association networks that could remediate aberrant perceptions of the bodily self.

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'.

Interoceptive influences on peripersonal space boundary.

Integration of body-related signals within the peripersonal space (PPS) contributes to bodily self-awareness. Whereas several studies have shown how individual PPS extension is shaped by external factors, e.g. during interactions with people and objects, no studies have looked at interoceptive influences on PPS extension. We exposed participants to an audio-tactile interaction task, to measure their PPS boundary (Session 1), and to a heartbeat counting task and a time estimation task, to specifically assess their interoceptive accuracy (Session 2). Participants' traits of private self-consciousness and social anxiety were also evaluated, to account for their possible effect on the relation between interoception and PPS representation. We found that higher interoceptive accuracy specifically predicts narrower PPS boundary. Moreover, this relation is moderated by individual traits of private self-consciousness, but not social anxiety. Extending the concept of interoceptive influences on exteroceptive body representations to PPS, our results, first, support the idea that a dynamic balance between intero-exteroceptive processing might represent a general principle underlying bodily self-awareness; second, they shed light on how interoception may affect also the way we interface with the external world. Finally, showing that, in order for interoceptive accuracy to be effective on the intero-exteroceptive balance, it is important that individuals tend to focus on inner sensations and feelings, our results suggest that a comprehensive intero-exteroceptive model of bodily self-awareness should be (at least) a three-dimensional model that includes individual self-consciousness traits.

I know you can see me: Social attention influences bodily self-awareness.

It has recently been demonstrated that eye contact influences bodily self-awareness. Here, we investigated if the belief of being the target of another person's attention may also induce such influence. We created videos of an individual wearing two different pairs of sunglasses. We manipulated the participants to believe that they were in on-line connection with the individual and that one of the pairs of sunglasses was obstructed so that the individual could not see them through it. We demonstrated that the perception of an individual wearing see-through sunglasses, as compared to obstructed sunglasses or a low-level baseline condition, led to a greater correlation between the participants' rating of the intensity of their bodily reactions and their skin conductance response to emotional pictures. This shows that the belief to be watched by another social agent increases bodily self-awareness and further suggests that such belief is embedded in direct gaze perception.