Pain thresholds vary considerably across individuals and are influenced by a number of behavioral, genetic and neurobiological factors. However, the neurobiological underpinnings that account for individual differences remain to be fully elucidated. In this study, we used voxel-based morphometry (VBM) and graph theory, specifically the local clustering coefficient (CC) based on resting-state connectivity, to identify brain regions, where regional gray matter volume and network properties predicted individual pain thresholds. As a main finding, we identified a cluster in the left posterior insular cortex (IC) reaching into the left parietal operculum, including the secondary somatosensory cortex, where both regional gray matter volume and the local CC correlated with individual pain thresholds. We also performed a resting-state functional connectivity analysis using the left posterior IC as seed region, demonstrating that connectivity to the pre- as well as postcentral gyrus bilaterally; that is, to the motor and primary sensory cortices were correlated with individual pain thresholds. To our knowledge, this is the first study that applied VBM in combination with voxel-based graph theory in the context of pain thresholds. The co-location of the VBM and the local CC cluster provide first evidence that both structure and function map to the same brain region while being correlated with the same behavioral measure; that is, pain thresholds. The study highlights the importance of the posterior IC, not only for pain perception in general, but also for the determination of individual pain thresholds.

中文翻译：

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岛叶皮质的网络特性和区域脑形态与个体疼痛阈值相关

疼痛阈值因人而异，并受许多行为、遗传和神经生物学因素的影响。然而，解释个体差异的神经生物学基础仍有待充分阐明。在这项研究中，我们使用基于体素的形态计量学 (VBM) 和图论，特别是基于静息状态连通性的局部聚类系数 (CC) 来识别大脑区域，其中区域灰质体积和网络特性可以预测个体疼痛阈值。作为一个主要发现，我们在左侧后岛叶皮层 (IC) 中发现了一个簇，该簇延伸到左侧顶叶盖，包括次级躯体感觉皮层，其中区域灰质体积和局部 CC 都与个体疼痛阈值相关。我们还使用左后 IC 作为种子区域进行了静息状态功能连接分析，证明了与双侧中央前回和中央后回的连接；也就是说，运动和初级感觉皮层与个体疼痛阈值相关。据我们所知，这是第一项在疼痛阈值的背景下将 VBM 与基于体素的图论相结合的研究。VBM 和本地 CC 集群的共同定位提供了第一个证据，证明结构和功能都映射到相同的大脑区域，同时与相同的行为测量相关；也就是痛阈。该研究强调了后部 IC 的重要性，不仅对于一般的疼痛感知，而且对于确定个体疼痛阈值。