Humans use touch to maintain their social relationships, and the emotional qualities of touch depend on who touches whom. However, it is not known how affective and social dimensions of touch are processed in the brain. We measured haemodynamic brain activity with fMRI from 19 subjects (10 males), while they were touched on their upper thigh by either their romantic partner, or an unfamiliar female or male confederate or saw the hand of one of these individuals near their upper thigh but were not touched. We used multi-voxel pattern analysis on pre-defined regions of interest to reveal areas that encode social touch in a relationship-specific manner. The accuracy of a machine learning classifier to identify actor for both feeling touch and seeing hand exceeded the chance level in the primary somatosensory cortex, while in the insular cortex accuracy was above chance level only for the touch condition. Restricting the task to classify the relationship (partner or stranger), while keeping the toucher sex fixed, amygdala, orbitofrontal cortex, and primary and secondary somatosensory cortices were able to discriminate toucher significantly above chance level.

These results suggest that information on the social relationship to the toucher is processed in a consistent manner in several regions. More complex information about toucher identity is processed in the primary somatosensory and insular cortices, both of which can be considered early sensory areas. More research is needed to understand the temporal order of these effects and the impact of contextual factors.

人类使用触摸来维持他们的社会关系，而触摸的情感品质取决于谁触摸了谁。然而，目前尚不清楚大脑中如何处理触觉的情感和社会维度。我们使用 fMRI 测量了 19 名受试者（10 名男性）的血流动力学大脑活动，他们的恋人或陌生的女性或男性同伙触摸了他们的大腿上部，或者在大腿上部附近看到了其中一个人的手，但没有被触动。我们对预定义的感兴趣区域使用多体素模式分析，以揭示以特定关系方式编码社交接触的区域。机器学习分类器识别演员的感觉触觉和视觉手的准确性超过了初级体感皮层的机会水平，而在岛叶皮层中，仅在触摸条件下的准确性高于机会水平。限制对关系（伴侣或陌生人）进行分类的任务，同时保持接触者的性别固定，杏仁核、眶额皮层以及初级和次级躯体感觉皮层能够明显高于机会水平区分接触者。

这些结果表明，与接触者的社会关系有关的信息在多个区域以一致的方式处理。关于接触者身份的更复杂的信息在初级体感和岛叶皮质中处理，这两个区域都可以被认为是早期的感觉区域。需要更多的研究来了解这些影响的时间顺序和背景因素的影响。