Sensory-Motor Laboratory (SeMoLa), Jules-Gonin Eye Hospital/Fondation Asile des Aveugles, Department of Ophthalmology/University of Lausanne, Lausanne, Switzerland; Rehabilitation Engineering Laboratory (RELab), Department of Health Sciences and Technology, ETH Zurich, Zurich, Switzerland; Department of Child and Adolescent Psychiatry and Psychotherapy, University Hospital of Psychiatry Zurich, University of Zurich, Zurich, Switzerland.
Sensory-Motor Laboratory (SeMoLa), Jules-Gonin Eye Hospital/Fondation Asile des Aveugles, Department of Ophthalmology/University of Lausanne, Lausanne, Switzerland.
Neuroimage. 2024 Oct 15;300:120870. doi: 10.1016/j.neuroimage.2024.120870. Epub 2024 Sep 28.
Based on visuo-tactile stimulation, the rubber hand illusion induces a sense of ownership for a dummy hand. Manipulating the visibility of the dummy hand during the stimulation influences cognitive aspects of the illusion, suggesting that the related brain activity may be influenced too. To test this, we analyzed brain activity (fMRI), subjective ratings, and skin conductance from 45 neurotypical participants undergoing a modified rubber hand illusion protocol where we manipulated the visibility (high, medium, and low) of a virtual hand, not the brush (virtual hand illusion; VHI). To further investigate the impact of visibility manipulations on VHI-related secondary effects (i.e. vicarious somatosensation), we recorded brain activity and skin conductance during a vicarious pain protocol (observation of painful stimulations of the virtual hand) that occurred after the VHI procedure. Results showed that, during both the VHI and vicarious pain periods, the activity of distinct visual, somatosensory, and motor brain regions was modulated by (i) visibility manipulations, (ii) coherence between visual and tactile stimulation, and (iii) time of visuo-tactile stimulation. Accordingly, embodiment-related subjective ratings of the perceived illusion were specifically influenced by visibility manipulations. These findings suggest that visibility modifications can impact the neural and cognitive effects of illusory body ownership, in that when visibility decreases the illusion is perceived as weaker and the brain activity in visual, motor, and somatosensory regions is overall lower. We interpret this evidence as a sign of the weight of vision on embodiment processes, in that the cortical and subjective aspects of illusory body ownership are weakened by a degradation of visual input during the induction of the illusion.
基于视触刺激，橡胶手错觉会让人产生对假手的所有权意识。在刺激过程中操纵假手的可见性会影响错觉的认知方面，这表明相关的大脑活动也可能受到影响。为了验证这一点，我们分析了 45 名神经正常的参与者的大脑活动（fMRI）、主观评分和皮肤电导率，他们接受了一种改良的橡胶手错觉方案，在该方案中，我们操纵了虚拟手的可见性（高、中、低），而不是刷子（虚拟手错觉；VHI）。为了进一步研究可见性操纵对 VHI 相关次要效应（即替代性躯体感觉）的影响，我们在 VHI 程序之后记录了大脑活动和皮肤电导率，进行了替代性疼痛协议（观察虚拟手的疼痛刺激）。结果表明，在 VHI 和替代性疼痛期间，不同的视觉、躯体感觉和运动大脑区域的活动都受到以下因素的调节：（i）可见性操纵，（ii）视觉和触觉刺激之间的一致性，以及（iii）视触刺激的时间。相应地，对所感知的错觉的具身相关主观评分受到可见性操纵的具体影响。这些发现表明，可见性的改变可以影响虚幻身体所有权的神经和认知效应，即当可见性降低时，错觉的感知会变得更弱，视觉、运动和躯体感觉区域的大脑活动总体上也会降低。我们将这一证据解释为视觉对具身过程的影响的一个标志，即当诱导错觉时，视觉输入的退化削弱了虚幻身体所有权的皮质和主观方面。
