Wearable Haptics for Somatosensory Perception and Self-consciousness

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.

Cogno-Vest: A Torso-Worn, Force Display to Experimentally Induce Specific Hallucinations and Related Bodily Sensations

Olaf Blanke, Hannes Bleuler, Atena Fadaeijouybari, Masayuki Hara, Kenny Jeanmonod, Oliver Alan Kannape, Jevita Potheegadoo

Recent advances in virtual reality and robotic technologies have allowed researchers to explore the mechanisms underlying bodily aspects of self-consciousness which are largely attributed to the multisensory and sensorimotor processing of bodily signals (bodily self-consciousness, BSC). One key contribution to BSC, that is currently poorly addressed due to the lack of a wearable solution, concerns realistic collision sensations on the torso. Here, we introduce and validate a proof-of-concept prototype of torso-worn force display, the Cogno-vest, that provides mechanical touch on the user s back in a sensorimotor perception experiment. In a first empirical study, we characterized human finger poking (N=28). In order to match these poking characteristics and meet the wearability criteria, we used bi-directional, push-pull solenoids as a force actuator in the Cogno-vest. Subsequently, and based on an iterative design procedure, a body-conforming, unisex, torso-worn force display was prototyped. Finally, we conducted a behavioral study that investigated BSC in 25 healthy participants by introducing conflicting sensorimotor signals between their hand and torso (back). Using the final reiteration of the Cogno-vest we successfully replicated previous findings on illusory states of BSC, characterized by presence hallucinations (PH) and passivity symptoms, and achieved higher illusion ratings compared to static conditions used in prior studies.

2021

Multisensory and sensorimotor origins of the sense of self

Polona Pozeg

Cognitive neuroscience has increasingly focused on studying the subject, i.e. the self, of conscious experience. In order to be the subject of an experience, we generally experience owning a physical body, being located within that body, and being able to distinguish the body and its actions from others. These pre-reflective experiences are based on brain mechanisms of multisensory and sensorimotor integration. In this thesis I investigated how our sense of self, in particular the senses of body ownership and of agency, depend on multimodal bodily signals. I achieved this by using approaches developed by cognitive neuroscience to study how the sense of self relates to the processing of bodily signals: creating bodily illusions with multisensory conflicts through the use of virtual reality and robotics. The first part of this thesis describes the investigation of the sense of body ownership in healthy subjects and in spinal cord injury patients, achieved by inducing conflicts between tactile information and visual feedback. The research presented in the second part of the thesis is centered on the experience of self-touch. There, I have first investigated how the manipulation of reference frames influences the perception of the illusion of self-touch, and second, how active self-touch influences the sense of body ownership. Lastly, in the third part of the thesis, I investigated how experimentally induced multisensory and sensorimotor conflicts perturb the sense of self in healthy subjects and induce experiences similar to certain symptoms observed in neurological and psychiatric disorders. I show that particular conflicts between bodily signals not only affect body perception and sense of agency for motor actions but also propagate to higher levels and influence even the sense of agency for mental representations in healthy subjects. Finally, I discuss my results and their relation to existing knowledge on bodily self-consciousness and position them in a broader picture of our current understanding of the self.

EPFL2016

Distinct illusory own-body perceptions caused by damage to posterior insula and extrastriate cortex

Olaf Blanke, Lukas Heydrich

Recent research in cognitive neuroscience using virtual reality, robotic technology and brain imaging has linked self-consciousness to the processing and integration of multisensory bodily signals. This work on bodily self-consciousness has implicated the temporo-parietal, premotor and extrastriate cortex and partly originated in work on neurological patients with different disorders of bodily self-consciousness. One class of such disorders is autoscopic phenomena, which are defined as illusory own-body perceptions, during which patients experience the visual illusory reduplication of their own body in extrapersonal space. Three main forms of autoscopic phenomena have been defined. During autoscopic hallucinations, a second own body is seen without any changes in bodily self-consciousness. During out-of-body experiences, the second own body is seen from an elevated perspective and location associated with disembodiment. During heautoscopy, subjects report strong self-identification with the second own body, often associated with the experience of existing at and perceiving the world from two places at the same time. Although it has been proposed that each autoscopic phenomenon is associated with different impairments of bodily self-consciousness, past research on neurological patients and the development of experimental paradigms for the study of bodily self-consciousness has focused on out-of-body experiences and the association with temporo-parietal cortex. Here, we performed quantitative lesion analysis in the-to date-largest group of patients with autoscopic hallucination and heautoscopy and compared the location of brain damage with those of control patients suffering from complex visual hallucinations. We found that heautoscopy was associated with lesions to the left posterior insula, and that autoscopic hallucinations were associated with damage to the right occipital cortex. Autoscopic hallucination and heautoscopy were further associated with distinct symptoms and deficits. The present data suggest that the autoscopic hallucination is a visuo-somatosensory deficit implicating extrastriate cortex and is, despite the visual hallucination of the own body, not associated with major deficits in bodily self-consciousness. Based on the symptoms and deficits in patients with heautoscopy and the implication of the left posterior insula, we suggest that abnormal bodily self-consciousness during heautoscopy is caused by a breakdown of self-other discrimination regarding affective somatosensory experience due to a disintegration of visuo-somatosensory signals with emotional (and/or interoceptive) bodily signals. These brain mechanisms are distinct from those described for out-of-body experiences. The present data extend previous models of autoscopic phenomena and provide clinical evidence for the importance of emotional and interoceptive signal processing in the posterior insula in relation to bodily self-consciousness.

2013