Data from: Forward modeling the rubber hand: illusion of ownership modifies motor-sensory predictions by the brain

The question of how we attribute observed body parts as our own, and the consequences of this attribution on our sensory-motor processes, are fundamental to understand how our brain distinguishes between self and other. Previous studies have identified interactions between 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; brushing only the rubber-hand after induction of the classical rubber-hand illusion (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 if the numbness illusion after the RHI is different when the rubber hand is brushed oneself, compared to when the brushing is performed by another. We observed that, all other conditions remaining 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.

我们如何将所感知到的身体部位归为自身所有，以及该归属过程对感觉运动过程产生的影响，是理解大脑如何区分自我与他人的核心问题。既往研究已证实，躯体所有权（ownership）感知与大脑的多感觉整合、跨感觉预测之间存在交互作用。本研究证实，错觉性躯体所有权（illusory ownership）还会改变大脑的运动感觉预测机制。

在预实验中，我们观察到一种全新的麻木错觉：在诱发经典橡胶手错觉（rubber-hand illusion, RHI）后，仅对橡胶手进行毛刷刺激，会使被试的真实手部产生错觉性麻木感。既往研究表明，自主生成的动作（如搔痒）会通过所谓的前向模型（forward model）介导的运动感觉预测机制被感知减弱。基于这一发现，本研究探究了：在RHI诱发后，由被试自主对橡胶手进行毛刷刺激，与由他人实施毛刷刺激时，所产生的麻木错觉是否存在差异。

我们发现，在其余实验条件保持一致的情况下，自主实施毛刷刺激时，被试真实手部的触觉感知敏感度降低（麻木感更强）。本研究结果表明，RHI会重塑前向模型，使得大脑能够预测自主对橡胶手实施运动动作所带来的触觉后果。