Binding body and self in visuo‐vestibular conflicts

Abstract

Maintenance of the bodily self relies on the accurate integration of multisensory inputs in which visuo-vestibular cue integration is thought to play an essential role. Here, we tested in healthy volunteers how conflicting visuo-vestibular bodily input might impact on body self-coherence in a full body illusion set-up. Natural passive vestibular stimulation was provided on a motion platform, while visual input was manipulated using virtual reality equipment. Explicit (questionnaire) and implicit (skin temperature) measures were employed to assess illusory self-identification with either a mannequin or a control object. Questionnaire results pointed to a relatively small illusion, but hand skin temperature, plausibly an index of illusory body ownership, showed the predicted drop specifically in the condition when participants saw the mannequin moving in congruence with them. We argue that this implicit measure was accessible to visuo-vestibular modulation of the sense of self, possibly mediated by shared neural processes in the insula involved in vestibular and interoceptive signalling, thermoregulation and multisensory integration. ABSTRACTMaintenance of the bodily self relies on the accurate integration of multisensory inputs wherebyvisuo-vestibular cue integration is thought to play an essential role.Here, we tested in healthy volunteers how conflicting visuo-vestibular bodily input might impact on body-self coherence in a full body illusion set-up. Natural passive vestibular stimulation was provided on a motion platform, while visual input was manipulated using virtual reality equipment.Explicit (questionnaire) and implicit (skin temperature) measures were employed to assessillusoryself-identification with either a mannequin or a control object. Questionnaire results pointed to a relatively small illusion,but thehand skin temperature, plausibly an index of illusory body ownership,showed the predicted drop specificallyin the condition when participants saw the mannequin moving in congruence with them. We argue that this implicit measure was accessible to visuo-vestibular modulation of the sense of self, possibly mediated by shared neural processes in the insula involved in vestibular and interoceptive signaling, thermoregulation and multisensory integration.3

Visual appearance of a virtual upper limb modulates the temperature of the real hand: a thermal imaging study in Immersive Virtual Reality

“…We also build on our previous observations (Tieri et al ., ,b) by showing that experiencing conscious FO over a passively observed virtual hand is a slow process that develops over many seconds (~ 44.3 s from the start of the virtual hand's observation). Moreover, we expanded on previous evidence for the existence of a link between skin temperature and bodily illusions (Moseley et al ., ; Hohwy & Paton, ; Llobera et al ., ; Salomon et al ., ; Macauda et al ., ) by reporting that changes in strength of FO and VA over the virtual body were reflected by somato‐topic changes to the real body's skin temperature regulation. Analyses of thermal images showed (i) a significant modulation in skin temperature of both right and left hand, with a large temperature increase during the observation of m‐Wrist, Full‐Wood and m‐Wood (mean Δ T = ~ 0.14 °C) conditions and only a slight increase during the Full‐Limb condition (mean Δ T = ~ 0.02 °C) that had produced maximal embodiment scores; and (ii) that such effects occurred ~ 79 s after the start of the virtual hand's observation (~ 35 s after the conscious experience of illusory ownership had begun).…”

“…Studies indicate that acquiring SoE over an external object requires the convergence of two main sources of information: (i) the on‐line integration of bottom–up, congruent multisensory visuo‐tactile (Botvinick & Cohen, ; Ehrsson et al ., , ; Costantini & Haggard, ), visuo‐motor (Tsakiris et al ., ; Sanchez‐Vives et al ., ; Kalckert & Ehrsson, ), visuo‐spatial (Lloyd, ) and visuo‐vestibular (Lopez et al ., ; Macauda et al ., ) information; and (ii) the modulation of top–down information based on an internal body representation (Graziano & Botvinick, ; Makin et al ., ; Tsakiris, ). Here we showed that simple passive observation in 1PP is a sufficient condition for eliciting SoE over a virtual body even in the absence of multisensory stimulation and without any alteration of the peripersonal space.…”

“…Rubber Hand Illusion studies demonstrate that the illusory SoE over an external body part can occur at both explicit (as indexed by subjective ratings in questionnaires) and implicit levels [as indexed by changes in physiological (Armel & Ramachandran, ) and neural reactivity (Ehrsson et al ., ; Arzy et al ., )]. These studies highlighted the importance of a variety of factors in eliciting SoE, including the congruency between multisensory visuo‐tactile (Botvinick & Cohen, ), visuo‐motor (Tsakiris et al ., ; Kalckert & Ehrsson, , ), visuo‐spatial (Lloyd, ) and visuo‐vestibular information (Macauda et al ., ), as well as the external object's shape (Haans et al ., ; Tsakiris et al ., ) and its anatomical and postural appearance (Pavani et al ., ; Ehrsson et al ., ; Costantini & Haggard, ; Ide, ).…”

“…Importantly, recent studies have highlighted a relationship between FO and the physiological mechanism of skin temperature regulation (Moseley et al ., ; Hohwy & Paton, ; Salomon et al ., ; Macauda et al ., ). Moseley et al .…”

Motion Instruction Method Using Head Motion-Associated Virtual Stereo Rearview

“…They indicated an unbiased perception in the HMD view-based pose reproduction, which showed reliance on both visual and proprioceptive feedback. As for visuo-vestibular conflicts, Macauda et al employed questionnaire and skin temperature measures to assess illusory self-identification with either a mannequin or a control object [22]. They suggested an importance of congruence of the visual sense with the vestibular sense as in the HMAR.…”