Ghost hand: My hand is not mine

Abstract

Synchronous visuo-tactile stimulation of the type in the rubber hand illusion (RHI)^1-3^ and in out of body experience (OBE)^4,5^ can induce the brain to incorporate external objects or images into a part or whole of body image. Whether in the context of RHI or OBE, since the participant passively receives visuo-tactile stimulations, body image appears only with the sense of ownership (SoO), not with the sense of agency (the registration that we are the initiators of our actions; SoA)^6,7^. Insofar as self-consciousness as a body image is a unity acting in its environments, body image has to be investigated in the relationship between SoO and SoA^8,9^. It requires an experimental condition in which SoO and SoA can be independently separated in an active condition. However, no experimental condition that is opposite to RHI and OBE in which a subject can feel SoA but not SoO has been proposed to date^10^. Here, we show that a person loses SoO for his own hand that he can freely move by his own will when he sees himself in a lateral view through a head mounted display. It was previously thought that SoO can be represented by synchronous inter-modal stimulations^10^, and that SoO appears to be complemented by SoA11. Our findings show that SoO can be lost under a synchronous visuo-proprioceptive condition while SoA can be maintained. SoO and SoA are two aspects of body representation, and similar dissociations have been proposed in various contexts, such as body image and body schema^12,13^, and 'Acting I' and 'Mine'^14^. Our result suggests that the two-centric-self consisting of SoA and SoO can enhance dynamically robust self-consciousness.