Vincent Hayward

Self-touch plays a central role in the construction and plasticity of the bodily self. But which mechanisms support this role? Previous accounts emphasize the convergence of proprioceptive and tactile signals from the touching and the touched body parts. Here, we hypothesise that proprioceptive information is not necessary for self-touch modulation of body-ownership. Because eye move- ments do not rely on proprioceptive signals as limb movements do, we developed a novel oculomotor self-touch paradigm where voluntary eye movements gener- ated corresponding tactile sensations. We then compared the effectiveness of eye versus hand self-touch movements in generating an illusion of owning a rub- ber hand. Voluntary oculomotor self-touch was as effective as hand-driven self- touch, suggesting that proprioception does not contribute to body ownership during self-touch. Self-touch may contribute to a unified sense of bodily self by binding voluntary actions toward our own body with their tactile consequences.

A physical model was utilized to show that the neural system can memorize a target position and is able to cause motor and sensory events that move the arm to a target with more accuracy. However, this cannot indicate in which coordinates the necessary computations are carried out. Turning off the lights causes the error to increase which is accomplished by cutting off one feedback path. The geometrical properties of arm kinematics and the properties of the kinesthetic and visual sensorial systems should be better known before inferences about higher levels of processing can be drawn.