Funded Grants

Multisensory mechanism of body ownership and the projection of ownership onto artificial bodies

How do we come to experience that we own our body? And why do we experience that our centre-of-awareness is located inside a physical body? These fundamental questions have been discussed in theology, philosophy, and psychology for centuries, but have been considered inaccessible to experimental investigation until recently. In neurology, it is known that people with damage to their premotor or posterior parietal lobes can fail to recognize their own limbs. However, although this indicates that the frontal and parietal association cortices are somehow involved in a sense of body ownership, little was known about how this is achieved. The aim of our research programe is to identify the perceptual processes and neuronal mechanisms that mediate the feeling of ownership of one's body.

Our hypothesis is that parts of one's own body are distinguished from objects in the external world by the specific patterns of correlated signals from the different sensory modalities they produce. In this model ownership corresponds to the perceptual fusion of visual, tactile and proprioceptive information into a coherent object that is a body-part. This multisensory integration process is obeying precise temporal and spatial congruency principles, is limited to the space near the body, and is operating in body-part-centered reference frames. It is hypothesized that the integration is implemented by populations of neurons in the premotor cortex, intraparietal cortex and inferior parietal cortex, areas which in non-human primates contain cells with the capacity to integrate visual, tactile and proprioceptive signals.

To test this model, we will use perceptual illusions where people experience dramatic changes in ownership of their body. For example, healthy volunteers will perceive another individual's body as their own, rubber hands as being part of their own body, or 'out-of-body' illusions, where ownership is projected outside the real body. These illusions are triggered by specific patterns of multisensory stimuli, and the identification of these patterns informs us about the principles governing the elicitation of ownership. Importantly, we can use these illusions as experimental tools in conjunction with complementary neuroimaging and neurodisruptive techniques to test the specific neuronal hypotheses outlined above.

Our research program will lead to major advances in our understanding of how the brain represents one's own body and will have important clinical and industrial applications. Identifying the mechanisms of ownership will enable the investigation of its possible breakdown in neurological and psychiatric disorders with disturbances in body ownership (such as body neglect after stroke; anosognosia; bodily delusions and hallucinations). Further, it will allow the controlled projection of ownership to be extended to artificial and virtual limbs and bodies. For example, we have already initiated the development of novel prosthetic limbs that feel like real limbs even without invasive interfaces, and of virtual reality applications where the sense of body ownership is seamlessly projected onto virtual bodies.