Somatosensory activations during the observation of touch and a case of vision-touch synaesthesia
Somatosensory activations during the observation of touch and a case of vision-touch synaesthesia
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DOI：
10.1093/brain/awh500
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发表时间：
2005-07-01
期刊：
影响因子：
14.5
通讯作者：
Ward, J
中科院分区：
文献类型：
--
作者：
Blakemore, SJ;Bristow, D;Ward, J
在这项研究中，我们描述了一种新的联觉形式，即对触摸的视觉感知会在感知者身上引发有意识的触觉体验。我们描述了一位女性受试者（C），对她而言，看到他人被触摸会在自己身体的相应部位产生触觉刺激的体验。除了这种明显异常的联觉体验外，C在其他各个方面都健康正常。在这项研究中，我们探究C的“镜像触摸”联觉体验是否是由对触摸观察有反应的神经系统过度活跃所导致。我们设计了一个功能性磁共振成像实验，以研究12名非联觉对照受试者和C在触摸感知中所涉及的神经系统。我们研究了观察人脸或颈部被触摸时的神经活动，并与观察物体上相应区域被触摸时的情况进行了比较。此外，为了研究触摸观察过程中激活的躯体感觉拓扑结构，我们比较了观察人脸或颈部被触摸时的激活情况以及受试者自己脸部或颈部被触摸时的激活情况。结果表明，非联觉受试者仅仅通过观察触摸就会激活躯体感觉皮层，而且这种激活是按躯体定位组织的，即观察脸部被触摸会激活初级躯体感觉皮层的头部区域，而观察颈部被触摸则不会。此外，在非联觉受试者中，大脑的镜像系统——包括前运动皮层、颞上沟和顶叶皮层——在观察他人被触摸时比观察物体被触摸时更易被激活。C的激活模式在三个方面与非联觉对照组不同。首先，C在观察触摸时躯体感觉皮层的激活程度明显更高。其次，C的左侧前运动皮层的一个区域被激活的程度比非联觉组更大。第三，C的双侧前岛叶皮层被激活，而非联觉组中没有这种激活的迹象。结果表明，在C中，触摸的镜像系统过度活跃，超过了有意识触觉感知的阈值。
In this study, we describe a new form of synaesthesia in which visual perception of touch elicits conscious tactile experiences in the perceiver. We describe a female subject (C) for whom the observation of another person being touched is experienced as tactile stimulation on the equivalent part of C's own body. Apart from this clearly abnormal synesthetic experience, C is healthy and normal in every other way. In this study, we investigate whether C's 'mirrored touch' synesthetic experience is caused by overactivity in the neural system that responds to the observation of touch. A functional MRI experiment was designed to investigate the neural system involved in the perception of touch in a group of 12 non-synesthetic control subjects and in C. We investigated neural activity to the observation of touch to a human face or neck compared with the observation of touch to equivalent regions on an object. Furthermore, to investigate the somatosensory topography of the activations during observation of touch, we compared activations when observing a human face or neck being touched with activations when the subjects themselves were touched on their own face or neck. The results demonstrated that the somatosensory cortex was activated in the non-synesthetic subjects by the mere observation of touch and that this activation was somatotopically organized such that observation of touch to the face activated the head area of primary somatosensory cortex, whereas observation of touch to the neck did not. Moreover, in non-synesthetic subjects, the brain's mirror system-comprising premotor cortex, superior temporal sulcus and parietal cortex-was activated by the observation of touch to another human more than to an object. C's activation patterns differed in three ways from those of the non-synesthetic controls. First, activations in the somatosensory cortex were significantly higher in C when she observed touch. Secondly, an area in left premotor cortex was activated in C to a greater extent than in the non-synesthetic group. Thirdly, the anterior insula cortex bilaterally was activated in C, but there was no evidence of such activation in the non-synesthetic group. The results suggest that, in C, the mirror system for touch is overactive, above the threshold for conscious tactile perception.