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

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.

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.

EPFL2021

Application of Tactile Perception Enhancement

Sylvain Cardin

Surrounding environment is mainly perceived through sight and hearing. Our sense of touch is mostly dedicated to explore the surface of objects using hands and fingers. Tactile sensitivity of the body skin is rather limited in common life, however this represents a viable channel to pass information. The goal of this thesis is to study the added value of tactile stimulation to increase perception in specific application contexts. First, we define our motivation and approach regarding existing tactile systems and scientific knowledge available. In order to study tactile influence in different applications, we decided to build our own hardware and software blocks based on vibrotactile actuators driven by embedded electronics communicating with an external computer. Our objective was to explore different research directions by assessing added value in term of perception for tactile stimulation. The first topic we study tends to replace one of our senses, sight, by a metaphorical vibrotactile feedback representing the distance to close range object. We developed an electronic travel aid for visually impaired people, based on vibration motors and sonar. We assessed its ability to evolve and avoid obstacles in our surrounding environment. The next step consists in determining if such a principle can be applied to pass information about the environment within the field of teleoperation. Indeed, controlling a distant unmanned aerial vehicle is a difficult task due to limited visual feedback and absence of proprioceptive cue to feel the motion of the aircraft. Applying vibrotactile feedback that represents the effect of the wind seems to be an interesting approach for mental perception of the behavior of a remote controlled blimp. Wind is a natural phenomenon that we feel through our somatosensory system. At this point we wondered about the need of a metaphorical representation using vibrotactile stimulation. Even if it is rather easy to recreate wind using a fan, there is a lack of proper hardware to recreate directional wind. We built the first "wearable" haptic wind device for virtual reality enhancement and proved its usability to pass relevant directional information. Giving a direction in 3D space requires that the actuators are not located on the same plane as in our previous systems. We developed a wireless vibrotactile jacket containing 32 vibration motors and present its added value for a 3D searching space exercise in virtual environment, in correlation with visual and auditory cues. The second half of this document treats about development and application of a vibrotactile system in the challenging "Solar Impulse" project, aiming at performing a flight around the world relying only on renewable energy. A prototype aircraft has been built pushing forward the limits of the feasible in solar energy, composite materials, power management and human factor. As scientific consultant, our mission was to build an intelligent jacket in order to achieve symbodic relation between man and machine. A Symbodic system (SYMbiotic BODies) is a wearable device that supports symbiotic communication between the bodies of the pilot and of the machine. We proposed then a promising concept on how to improve awareness of the aircraft behavior. Passing from research concept to a concrete flying prototype is not an easy task, especially in terms of end-user acceptance: habits are strong for experienced pilot. But such an extraordinary airplane leads to some extraordinary aerodynamical behavior and the need of new visualization instruments. We developed an alert system for long flight duration based on the principle of the rumble strip installed on side of worldwide motor ways. Extensive tests have been performed by putting a subject in command of a highly realistic flight simulator for 48 hours straight. We showed that such system produces significant improvements of piloting performance under heavy sleep deprivation constraints.

EPFL2010

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