Separate multisensory integration processes for ownership and localization of body parts.

The experiences that body parts are owned and localized in space are two key aspects of body awareness. Although initial work assumed that the perceived location of one's body part can be used as a behavioral measure to assess the feeling of owning a body part, recent studies call into question the relationship between localization and ownership of body parts. Yet, little is known about the processes underlying these two aspects of body-part awareness. Here, I applied a statistically optimal cue combination paradigm to a perceptual illusion in which ownership over an artificial hand is experienced, and found that variances predicted by a model of optimal cue combination are similar to those observed in localization of the participant's hand, but systematically diverge from those observed in ownership of the artificial hand. These findings provide strong evidence for separate processes between ownership and localization of body parts, and indicate a need to revise current models of body part ownership. Results from this study suggest that the neural substrates for perceptual identification of one's body parts-such as body ownership-are distinct from those underlying spatial localization of the body parts, thus implying a functional distinction between "who" and "where" in the processing of body part information.