Kanayama Noriaki, Morandi Alberto, Hiraki Kazuo, Pavani Francesco
Institute of Biomedical and Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami, Hiroshima, 734-8551, Japan.
Department of Psychology and Cognitive Science, University of Trento, Rovereto, Italy.
Brain Topogr. 2017 Jan;30(1):122-135. doi: 10.1007/s10548-016-0519-x. Epub 2016 Sep 12.
Rubber hand illusion (RHI) is an important phenomenon for the investigation of body ownership and self/other distinction. The illusion is promoted by the spatial and temporal contingencies of visual inputs near a fake hand and physical touches to the real hand. The neural basis of this phenomenon is not fully understood. We hypothesized that the RHI is associated with a fronto-parietal circuit, and the goal of this study was to determine the dynamics of neural oscillation associated with this phenomenon. We measured electroencephalography while delivering spatially congruent/incongruent visuo-tactile stimulations to fake and real hands. We applied time-frequency analyses and calculated renormalized partial directed coherence (rPDC) to examine cortical dynamics during the bodily illusion. When visuo-tactile stimulation was spatially congruent, and the fake and real hands were aligned, we observed a reduced causal relationship from the medial frontal to the parietal regions with respect to baseline, around 200 ms post-stimulus. This change in rPDC was negatively correlated with a subjective report of the RHI intensity. Moreover, we observed a link between the proprioceptive drift and an increased causal relationship from the parietal cortex to the right somatosensory cortex during a relatively late period (550-750 ms post-stimulus). These findings suggest a two-stage process in which (1) reduced influence from the medial frontal regions over the parietal areas unlocks the mechanisms that preserve body integrity, allowing RHI to emerge; and (2) information processed at the parietal cortex is back-projected to the somatosensory cortex contralateral to the real hand, inducing proprioceptive drift.
橡胶手错觉（RHI）是研究身体所有权以及自我/他人区分的一个重要现象。在假手附近的视觉输入与对真实手部的物理触摸之间的时空一致性会引发这种错觉。这一现象的神经基础尚未完全明晰。我们推测RHI与额顶叶回路有关，本研究的目的是确定与该现象相关的神经振荡动态。我们在对假手和真实手部进行空间匹配/不匹配的视觉触觉刺激时测量脑电图。我们应用时频分析并计算重归一化偏相干（rPDC），以检查身体错觉期间的皮层动态。当视觉触觉刺激在空间上匹配，且假手和真实手部对齐时，我们观察到在刺激后约200毫秒时，相对于基线，从内侧额叶到顶叶区域的因果关系减弱。rPDC的这种变化与RHI强度的主观报告呈负相关。此外，在相对较晚的时期（刺激后550 - 750毫秒），我们观察到本体感觉漂移与从顶叶皮层到右侧体感皮层的因果关系增加之间存在联系。这些发现表明了一个两阶段过程：（1）内侧额叶区域对顶叶区域的影响减弱，从而开启了维持身体完整性的机制，使RHI得以出现；（2）在顶叶皮层处理的信息被反向投射到与真实手部对侧的体感皮层，从而诱发本体感觉漂移。
