Multisensory processing and agency in VR embodiment: Interactions through BCI and their therapeutic applications

Abstract

Body ownership refers to the experience that this body is my body and is closely linked to consciousness. Multisensory integration processes play an important role in body ownership as shown in the rubber hand illusion, which induces the illusory experience that a rubber hand is part of one's own body. Illusions of body ownership can also be experienced in immersive virtual reality (VR), which was used in all three experiments of this thesis. The first experiment of this thesis aimed at investigating some of the underlying mechanisms of body ownership. Specifically we were interested whether the body ownership illusion fluctuates over time and if so, whether these fluctuations are related to spontaneous brain activity. The second experiment aimed at investigating the relation between body ownership illusions and pain perception. Looking at one's own body has been demonstrated to have analgesic properties. This well-known effect in people's real hand has been studied in illusory owned hands with contradictory results. It has been replicated in VR-embodiment, but there are controversial findings in the rubber hand illusion. One crucial difference between the rubber hand illusion and VR-embodiment is that in VR real and virtual hand can be colocated while this is not possible in the rubber hand illusion. We were interested whether the distance between real and surrogate hand can explain controversial findings in the literature. When people experience high levels of body ownership over a virtual body, they can also feel agency over the actions of that virtual body. Agency has been described as result of a matching between predicted and actual sensory feedback of a planned motor action, a process involving motor areas. However, situations in which strong body ownership gives us the illusion of agency, raise the question of the involvement of motor areas in the sense of agency. In the third experiment of this thesis we explored this question in the context of brain computer interfaces (BCI). All together these experiments investigated underlying processes of body ownership and its influences on pain perception and agency. The findings have implications in pain management and neurological rehabilitation.