Krämer Heidrun H, Stenner Christian, Seddigh Susann, Bauermann Thomas, Birklein Frank, Maihöfner Christian
Department of Neurology, University of Mainz, Mainz, Germany.
J Pain. 2008 Jun;9(6):543-51. doi: 10.1016/j.jpain.2008.01.340. Epub 2008 May 2.
Allodynia means that innocuous tactile stimulation is felt as pain. Accordingly, cerebral activations during allodynia or touch should markedly differ. The aim of this study was to investigate whether the imagination of allodynia affects brain processing of touch in healthy subjects. Seventeen healthy subjects divided into 2 subgroups were investigated: The first group (n = 7) was familiar with allodynia, based on previous pain studies, whereas the second group (n = 10) had never knowingly experienced allodynia. Using functional magnetic resonance imaging, 2 experimental conditions were investigated. In one condition the subjects were simply touched at their left hand, whereas during the other condition they were asked to imagine pain (allodynia) during tactile stimulation of the right hand and to estimate the imagined pain on a numeric rating scale. Data processing and analysis were performed with the use of SPM5. The group analysis of all subjects revealed that tactile stimulation activated contralateral somatosensory cortices (S1 [primary] and S2 [secondary]), but the imagination of allodynia led to an additional activation of anterior cingulate cortex and bilateral activation of S2, insular cortex, and prefrontal cortices. Subgroup analysis using rating-weighted predictors revealed activation of the contralateral thalamus, anterior cingulate cortex, and amygdala and a bilateral activation of S1, S2, and insular cortex and prefrontal cortices in allodynia-experienced subjects. In contrast, allodynia-inexperienced subjects only activated contralateral S1 and bilateral S2. Just the imagination that touch is painful is able to partly activate the central pain system, but only when the subject has previous experience of this. According to our results, the medial pain system is involved in the encoding of imagined allodynia.
This article reports that pain experience is able to alter central processing of sensory stimuli. Pain knowledge appears to be able to shift "normal" tactile processing to a different quality, resulting in modified brain activity. Therefore, our study may contribute to the current understanding of human pain and will promote future research on this field.
痛觉过敏是指无害的触觉刺激被感知为疼痛。因此，痛觉过敏或触觉过程中的大脑激活应该有显著差异。本研究的目的是调查痛觉过敏的想象是否会影响健康受试者对触觉的大脑处理过程。对17名健康受试者进行了研究，他们被分为2个亚组：根据之前的疼痛研究，第一组（n = 7）熟悉痛觉过敏，而第二组（n = 10）从未有意识地经历过痛觉过敏。使用功能磁共振成像，研究了2种实验条件。在一种条件下，简单地触摸受试者的左手，而在另一种条件下，要求他们在右手触觉刺激期间想象疼痛（痛觉过敏），并在数字评分量表上估计想象的疼痛程度。使用SPM5进行数据处理和分析。对所有受试者的组分析显示，触觉刺激激活了对侧体感皮层（S1[初级]和S2[次级]），但痛觉过敏的想象导致前扣带回皮层的额外激活以及S2、岛叶皮层和前额叶皮层的双侧激活。使用评分加权预测因子的亚组分析显示，有痛觉过敏经历的受试者中，对侧丘脑、前扣带回皮层和杏仁核激活，以及S1、S2、岛叶皮层和前额叶皮层的双侧激活。相比之下，没有痛觉过敏经历的受试者仅激活对侧S1和双侧S2。仅仅是触摸是疼痛的这种想象就能部分激活中枢疼痛系统，但只有当受试者有过这种经历时才会如此。根据我们的结果，内侧疼痛系统参与了想象性痛觉过敏的编码。
本文报道疼痛经历能够改变感觉刺激的中枢处理过程。疼痛知识似乎能够将“正常”的触觉处理转变为不同的性质，从而导致大脑活动的改变。因此，我们的研究可能有助于当前对人类疼痛的理解，并将促进该领域未来的研究。
