Neural Mechanisms of the Embodied Self

What is it like to have a body? The unitary experience of the self and the body accompanied by unambiguous self-location and egocentric visuo-spatial perspective are essential aspects of the embodied self. They play a vital role for dynamic whole body human perception and interactions in our daily lives and help distinguish our body from others and the environment. In the current thesis, we used an amalgam of virtual reality techniques and cognitive neuroscience methods in combination with electrical neuroimaging to investigate multisensory, sensorimotor, and cognitive processes involved in mental own body imagery, visuo-spatial perspective taking, the feeling of ownership and agency and their contribution to different aspects of the bodily self and bodily processing.

Preventing Breaks in Embodiment in Immersive Virtual Reality

Thibault Serge Mario Porssut

Virtual reality (VR) is immersive not only because of visual integration, but because we can act and perform in a virtual environment (VE). Beyond the mere fact that a VR system provides images computed directly from the users' viewpoint in stereoscopy, it can also provide a natural way to interact within the VE using the entire body. Full-body motion capture allows the user's movement to be mapped to a virtual body. Such a mapping may let users feel in control of (sense of agency), own (sense of body ownership) and locate themselves inside this virtual body (sense of self-location), thus leading them to feel embodied in this virtual body whenever these conditions are met (sense of embodiment (SoE)). Hence the integration of a full body avatar in VR is essential, as it brings even more; experiencing being someone else, train to recover mobility or having superhuman abilities. Most importantly, the avatar mediates the virtual nature of the VE to make it seamless for the user. Thus, this thesis focuses on helping the users execute complex movements in VR by applying a distortion to their movements. However, such a distortion is efficient only if users, when assisted, do not experience a break in embodiment (BiE), i.e., do not abruptly lose their sense of embodiment. Moreover, the way the virtual body is perceived is not consistent between users and some users might accept or reject a virtual body more easily than others. Therefore, this thesis explores how to prevent a BiE while distorting users' movement and adapting the VR experience to each individual. To this end, we designed a system combining brain-computer interface and machine learning to detect when users experience a BiE, compute users' preferences, and adapt the VR application's parameters. We first identified the user`s threshold for perceiving a movement distortion in some critical contexts, such as articular limits. We designed a new distortion to help users execute a complex movement. We introduced a method based on machine learning to find users' preferences when using our new distortion. We also established a link between the brain's error monitoring mechanism and the cognitive process of embodiment. This link exposed a new implicit EEG marker indicating when users experience a BiE. Finally, we designed a system to calibrate the distortion implicitly based on users' preferences with all these elements. This system first consists of detecting a BiE during a continuous movement thanks to state-of-the-art brain-computer interface algorithms. Our machine learning method then computes users' preferences, and the distortion is adapted dynamically. This original approach demonstrates the use of an implicit feedback loop to help users while preventing any BiE. Our framework opens an exciting perspective for personalized and self-adapting embodiment systems.

EPFL2021

Self in time: imagined self-location influences neural activity related to mental time travel

Olaf Blanke

Conscious awareness of the self as continuous through time is attributed to the human ability to remember the past and to predict the future, a cogitation that has been called "mental time travel" (MTT). MTT allows one to re-experience one's own past by subjectively "locating" the self to a previously experienced place and time, or to pre-experience an event by locating the self into the future. Here, we used a novel behavioral paradigm in combination with evoked potential mapping and electrical neuroimaging, revealing that MTT is composed of two different cognitive processes: absolute MTT, which is the location of the self to different points in time (past, present, or future), and relative MTT, which is the location of one's self with respect to the experienced event (relative past and relative future). These processes recruit a network of brain areas in distinct time periods including the occipitotemporal, temporoparietal, and anteromedial temporal cortices. Our findings suggest that in addition to autobiographical memory processes, the cognitive mechanisms of MTT also involve mental imagery and self-location, and that relative MTT, but not absolute MTT, is more strongly directed to future prediction than to past recollection.

2008

Embodied space in architecture, cognitive neuroscience, and virtual reality

Isabella Maria Pasqualini

Recent findings in cognitive neuroscience enable improved understanding of embodiment and egocentric space in architecture. From a historical perspective the human body has been inferred as a reference in the debate of architectonic proportion. It was suggested that architectonic form moulds the subjective experience of the environment in contingency with skilful articulation of geometrical proportions in a three-dimensional construct. Modern science recalls several notions of how perception, thought and action are embodied. Embodiment and the sense of body ownership as such have been linked to multisensory and own-body processing, allowing for a relationship between aspects of the self to the conception of architectonic space and theory. Investigations about multisensory integration of architectonic space and its relation to own-body processing may therefore provide scientific insight to metaphorical and functional associations with the human bodily experience of architectonic space and its digital representation including perspective and immersive virtual reality. Attempts to sketch an interaction between architecture and cognitive neuroscience may bring about a design discipline based on multisensory own-body processing with permeable borders to contemporary science and technologies. This PhD thesis introduces digital space and cognitive neuroscience to the investigation of embodiment in architecture using techniques from immersive virtual reality and cognitive psychology. Here, three experimental studies using immersive virtual reality were based on the phenomenology of own-body perception introducing parameters from architecture. With such setups we tested whether bodily self-consciousness may be associated to architecture through a visuo-tactile conflict, and, whether changes in the architectonic space modulate bodily self-consciousness. Our results relate bodily self-consciousness with architecture specific perceptions, as well as bodily stability. Also, we observed perceptual changes related to visual perspective. We discuss such findings with regard to bodily feelings and perceived geometry through a critical confrontation with notions of embodiment in architecture.