MR Center of Excellence, Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Waehringer Guertel 18-20, 1090, Vienna, Austria.
Social, Cognitive and Affective Neuroscience Unit, Department of Cognition, Emotion, and Methods in Psychology, Faculty of Psychology, University of Vienna, Vienna, Austria.
Sci Rep. 2021 Nov 25;11(1):22929. doi: 10.1038/s41598-021-01881-4.
Pain habituation is associated with a decrease of activation in brain areas related to pain perception. However, little is known about the specificity of these decreases to pain, as habituation has also been described for other responses like spinal reflexes and other sensory responses. Thus, it might be hypothesized that previously reported reductions in activation are not specifically related to pain habituation. For this reason, we performed a 3 T fMRI study using either painful or non-painful electrical stimulation via an electrode attached to the back of the left hand. Contrasting painful vs. non-painful stimulation revealed significant activation clusters in regions well-known to be related to pain processing, such as bilateral anterior and posterior insula, primary/secondary sensory cortices (S1/S2) and anterior midcingulate cortex (aMCC). Importantly, our results show distinct habituation patterns for painful (in aMCC) and non-painful (contralateral claustrum) stimulation, while similar habituation for both types of stimulation was identified in bilateral inferior frontal gyrus (IFG) and contralateral S2. Our findings thus distinguish a general habituation in somatosensory processing (S2) and reduced attention (IFG) from specific pain and non-pain related habituation effects where pain-specific habituation effects within the aMCC highlight a change in affective pain perception.
痛觉习惯化与与疼痛感知相关的大脑区域的激活减少有关。然而，对于这些减少与疼痛的特异性知之甚少，因为习惯化也已经被描述为其他反应，如脊髓反射和其他感觉反应。因此，人们可能假设以前报道的激活减少与疼痛习惯化无关。出于这个原因，我们使用连接到左手背面的电极进行了 3T fMRI 研究，分别使用疼痛或非疼痛的电刺激。对比疼痛与非疼痛刺激显示出与疼痛处理相关的区域中的显著激活簇，例如双侧前岛叶和后岛叶、初级/次级感觉皮层（S1/S2）和前扣带皮层（aMCC）。重要的是，我们的结果显示出疼痛（在 aMCC 中）和非疼痛（对侧屏状核）刺激的明显习惯化模式，而在双侧额下回（IFG）和对侧 S2 中则发现了两种刺激的相似习惯化。因此，我们的研究结果区分了躯体感觉处理（S2）和注意力降低（IFG）的一般习惯化，以及特定的疼痛和非疼痛相关的习惯化效应，其中 aMCC 中的疼痛特异性习惯化效应突出了情感疼痛感知的变化。
