Lloyd Donna, Morrison India, Roberts Neil
Magnetic Resonance and Image Analysis Research Centre, University of Liverpool, Liverpool, UK.
J Neurophysiol. 2006 Jan;95(1):205-14. doi: 10.1152/jn.00614.2005. Epub 2005 Sep 14.
The posterior parietal cortex of both human and non-human primates is known to play a crucial role in the early integration of visual information with somatosensory, proprioceptive and vestibular signals. However, it is not known whether in humans this region is further capable of discriminating if a stimulus poses a threat to the body. In this functional magnetic resonance imaging (fMRI) study, we tested the hypothesis that the posterior parietal cortex of humans is capable of modulating its response to the visual processing of noxious threat representation in the absence of tactile input. During fMRI, participants watched while we "stimulated" a visible rubber hand, placed over their real hand with either a sharp (painful) or a blunt (nonpainful) probe. We found that superior and inferior parietal regions (BA5/7 and BA40) increased their activity in response to observing a painful versus nonpainful stimulus. However, this effect was only evident when the rubber hand was in a spatially congruent (vs. incongruent) position with respect to the participants' own hand. In addition, areas involved in motivational-affective coding such as mid-cingulate (BA24) and anterior insula also showed such relevance-dependent modulation, whereas premotor areas known to receive multisensory information about limb position did not. We suggest these results reveal a human anatomical-functional homologue to monkey inferior parietal areas that respond to aversive stimuli by producing nocifensive muscle and limb movements.
众所周知，人类和非人类灵长类动物的后顶叶皮层在视觉信息与体感、本体感觉和前庭信号的早期整合中起着关键作用。然而，目前尚不清楚在人类中，该区域是否还能够辨别刺激是否对身体构成威胁。在这项功能磁共振成像（fMRI）研究中，我们测试了以下假设：在没有触觉输入的情况下，人类的后顶叶皮层能够调节其对有害威胁表征的视觉处理的反应。在fMRI过程中，当我们用尖锐（疼痛）或钝性（非疼痛）探针“刺激”放在参与者真实手上的可见橡胶手时，参与者进行观看。我们发现，顶叶上下区域（BA5/7和BA40）在观察到疼痛与非疼痛刺激时，其活动增加。然而，这种效应仅在橡胶手相对于参与者自己的手处于空间一致（相对于不一致）位置时才明显。此外，参与动机-情感编码的区域，如扣带中部（BA24）和前岛叶，也表现出这种相关性依赖的调制，而已知接收有关肢体位置的多感官信息的运动前区则没有。我们认为，这些结果揭示了与猴子顶叶下部区域的人类解剖-功能同源物，后者通过产生防御性肌肉和肢体运动来对厌恶刺激做出反应。
