Seeing and identifying with a virtual body decreases pain perception

Pain and the conscious mind (or the self) are experienced in our body. Both are intimately linked to the subjective quality of conscious experience. Here, we used virtual reality technology and visuo-tactile conflicts in healthy subjects to test whether experimentally induced changes of bodily self-consciousness (self-location; self-identification) lead to changes in pain perception. We found that visuo-tactile stroking of a virtual body but not of a control object led to increased pressure pain thresholds and self-location. This increase was not modulated by the synchrony of stroking as predicted based on earlier work. This differed for self-identification where we found as predicted that synchrony of stroking increased self-identification with the virtual body (but not a control object), and positively correlated with an increase in pain thresholds. We discuss the functional mechanisms of self-identification, self-location, and the visual perception of human bodies with respect to pain perception.

The Architectonic Experience of Body and Space in Augmented Interiors

Olaf Blanke, Maria Laura Blefari, Isabella Maria Pasqualini, Andrea Serino

The environment shapes our experience of space in constant interaction with the body. Architectonic interiors amplify the perception of space through the bodily senses; an effect also known as embodiment. The interaction of the bodily senses with the space surrounding the body can be tested experimentally through the manipulation of multisensory stimulation and measured via a range of behaviors related to bodily self-consciousness. Many studies have used Virtual Reality to show that visuotactile conflicts mediated via a virtual body or avatar can disrupt the unified subjective experience of the body and self. In the full-body illusion paradigm, participants feel as if the avatar was their body (ownership, self-identification) and they shift their center of awareness toward the position of the avatar (self-location). However, the influence of non-bodily spatial cues around the body on embodiment remains unclear, and data about the impact of architectonic space on human perception and self-conscious states are sparse. We placed participants into a Virtual Reality arena, where large and narrow virtual interiors were displayed with and without an avatar. We then applied synchronous or asynchronous visuotactile strokes to the back of the participants and avatar, or, to the front wall of the void interiors. During conditions of illusory self-identification with the avatar, participants reported sensations of containment, drift, and touch with the architectonic environment. The absence of the avatar suppressed such feelings, yet, in the large space, we found an effect of continuity between the physical and the virtual interior depending on the full-body illusion. We discuss subjective feelings evoked by architecture and compare the full-body illusion in augmented interiors to architectonic embodiment. A relevant outcome of this study is the potential to dissociate the egocentric, first-person view from the physical point of view through augmented architectonic space.

2018

Illusory own body perceptions: case reports and relevance for bodily self-consciousness

Olaf Blanke, Sebastian Dieguez Falcon, Lukas Heydrich

Neurological disorders of body representation have for a long time suggested the importance of multisensory processing of bodily signals for self-consciousness. One such group of disorders--illusory own body perceptions affecting the entire body--has been proposed to be especially relevant in this respect, based on neurological data as well as philosophical considerations. This has recently been tested experimentally in healthy subjects showing that integration of multisensory bodily signals from the entire body with respect to the three aspects: self-location, first-person perspective, and self-identification [corrected], is crucial for bodily self-consciousness. Here we present clinical and neuroanatomical data of two neurological patients with paroxysmal disorders of full body representation in whom only one of these aspects, self-identification, was abnormal. We distinguish such disorders of global body representation from related but distinct disorders and discuss their relevance for the neurobiology of bodily self-consciousness.

Elsevier2010

Wearable Haptics for Somatosensory Perception and Self-consciousness

Atena Fadaeijouybari

Recent research has highlighted the crucial role of the processing of somatosensory signals involving the torso for global aspects of Bodily Self Consciousness (BSC), i.e., the experience of the conscious "I" as embodied and localized within bodily space. Compared to advances in hand or finger-based haptic interfaces, current haptic technology for the torso is relatively underdeveloped as its operations are limited to stationary conditions and laboratory environments. My thesis aims to design, implement and validate novel torso-worn tactile displays to investigate BSC in healthy individuals with specific emphasis on robot-induced presence hallucination (PH, illusory experience of feeling someone behind) and tactile gait agency. First, I examined if torso-worn haptic interfaces can be used to induce specific alterations of BSC (passivity, self-touch, and PH) in healthy individuals by adapting a robotic system and paradigm previously established by our lab (Blanke et al. 2014) to the torso-worn haptic interface. In a feasibility study in healthy individuals, a torso-worn vibrotactile display (Study1) successfully induced the illusory sensations of being touched (passivity experience). Next, I developed CognoVest, a portable, torso-worn force interface that I designed to provide human-like poking stimuli on the user's back. Study 2 confirms the induction of illusory self-touch and passivity experiences by CognoVest and the induction of PH of mild to moderate intensity in healthy individuals. In Study 3, I extended the use of torso-worn haptic interfaces to the research on conscious action monitoring and investigated the sense of agency (SoA; a core aspect of BSC) for the entire body. To this aim, I developed the FeetBack system that examines the sensorimotor perception of tactile action consequences during locomotion, as previously tested by our lab for auditory and visual action consequences. Study 3 extends prior findings on the auditory or visual gait agency to the sense of touch and shows that delayed re-mapped tactile feedback systematically modulates SoA for walking. Finally, I examined and compared tactile spatial discrimination on the human back (Study 4) for force and vibrotactile stimulation, using interfaces realized in Study 2 and 3, thus providing a first direct (within-participant) evaluation of such interfaces. At the intersection of haptics and behavioral neuroscience, my thesis makes contributions by taking the first steps towards the design, and validation of torso-worn haptic interfaces as well as their applications in stationary/mobile sensorimotor experimentation settings. My findings for tactile perception on the back suggest that designers can use force stimulators to design the torso-worn tactile interface to provide more ecological touch feedback with an (almost) similar level of tactile spatial discrimination accuracy as observed in widespread vibrotactile interfaces. I applied this approach to the design of the CognoVest that induced systematic change in self-other distinctions. Results with CognoVest might have important implications for developing wearable therapeutic devices to down-regulate specific psychotic symptoms in patients with PH experiences. Moreover, I showed that healthy walkers had strong SoA for remapped tactile feedback, suggesting that the FeetBack system could potentially be used to enhance gait awareness in patients with gait deficits.