Interactions of Body Representations in Rubber Hand Illusion and Tool-Use Paradigms

For over a century in the neuropsychological literature, it is thought that there are (at least) two different body representations in the brain, one for perception, called body image, and one for action, called body schema. Rubber hand illusion and tool-use paradigms have been used frequently for the past twenty-five years to study body representations in the brain, but they have produced two distinct literatures that have progressed independently of each other. While the changes in the body representation resulting from the rubber hand illusion are often attributed to body image, it is widely accepted that the changes that occur due to tool-use are represented by body schema. The effects of rubber hand illusion are often measured by proprioceptive drift and subjective experience questionnaires. On the other hand, the effects of tool use are evaluated through kinematic measurements recorded during the movement of the limb using the tool, or by pointing the midpoint of this limb with the other hand (forearm bisection). Although these two experimental paradigms are thought to affect different body representations, interactions between these representations are inevitable, considering the common sensory modalities targeted by the techniques used to measure changes in these representations. The aim of this study is to show, for the first time in the literature, that the measurement made in one of these two experimental paradigms, which are theorized to be based on different body representations, can change with manipulations in the other method.