Forward modelling the rubber hand: illusion of ownership modifies motor-sensory predictions by the brain.

Laura Aymerich-Franch,Abderrahmane Kheddar,Gowrishankar Ganesh,Damien Petit

doi:10.1098/rsos.160407

Abstract

The question of how we attribute observed body parts as our own, and the consequences of this attribution on our sensory-motor processes, is fundamental to understand how our brain distinguishes between self and other. Previous studies have identified interactions between the illusion of ownership, and multi-sensory integration and cross-sensory predictions by the brain. Here we show that illusory ownership additionally modifies the motor-sensory predictions by the brain. In our preliminary experiments, we observed a new numbness illusion following the classical rubber-hand illusion (RHI); brushing only the rubber hand after induction of the RHI results in illusory numbness in one's real hand. Previous studies have shown that self-generated actions (like tickling) are attenuated by motor-sensory predictions by the so-called forward model. Motivated by this finding, here we examined whether the numbness illusion after the RHI is different when the rubber hand is brushed oneself, compared with when the brushing is performed by another. We observed that, all other conditions remaining the same, haptic perception in the real hand was lower (numbness higher) during self-generated brushing. Our result suggests that RHI reorganizes the forward model, such that we predict haptic consequences of self-generated motor actions on the rubber hand.

Highlights

Embodiment of limbs and the associated ownership are largely agreed to be a consequence of multi-sensory integration in the2016 The Authors
It is known that the rubber-hand illusion (RHI) can be elicited with active movements instead of touches applied by the experimenter [25,26,27] and that ownership is affected by agency [28]
RHI has been shown to induce changes in our body representations, both the body image that is utilized for perception [29,30] as well as the body schema, that is used for motor actions [30,31,32], such as during tool use [33,34,35]

Summary

Introduction

The motor-sensory predictions from forward models are known to modulate haptic perception in individuals resulting in differences between perceptions of self-induced haptic stimulations and those induced by others [19,20,21,22,23]—this, for example, is said to explain why we are tickled by others, but cannot tickle ourselves [22]. We exploit this observation to evaluate whether the rubber-hand illusion (RHI) reorganizes the forward model in the brain.

Experiment 1

Experiment 2

Findings

Discussion