Odor modulates the experience of pain, but the neural basis of how the two sensory modalities, olfaction and pain, are linked in the central nervous system is far from clear. In this study, we investigated the mechanisms by which the brain modulates the pain experience under concurrent odorant stimulation. We conducted an fMRI study using a 2 × 3 factorial design, in which one of two temperatures (warm, hot) and one of three types of odors (pleasant, unpleasant, no odor) were presented simultaneously. “Hot” temperatures were individually determined as those perceived as painful (mean temperature = 46.9 °C). The non-painful “warm” temperature was set to 40 °C. Participants rated hot compared to warm stimuli as more intense and unpleasant, especially in the presence of an unpleasant odor. Parametric modeling on the intensity ratings activated the pain network, covering brain regions activated by the hot stimuli. The presence of an odor, irrespective of its valence, activated the amygdalae. In addition, the amygdalae showed stimulus-dependent functional couplings with the right supramarginal gyrus and with the left superior frontal gyrus. The coupling between the right amygdala and the left superior frontal gyrus was related to the intensity and unpleasantness ratings of the pain experience. Our results suggest that these functional connections may reflect the integrating process of the two sensory modalities, enabling olfactory influence on the pain experience.

气味调节疼痛体验，但嗅觉和疼痛这两种感觉方式如何在中枢神经系统中联系起来的神经基础尚不清楚。在这项研究中，我们调查了大脑在并发气味刺激下调节疼痛体验的机制。我们使用 2 × 3 析因设计进行了一项 fMRI 研究，其中同时呈现了两种温度（温暖、炎热）中的一种和三种气味（愉快、难闻、无气味）中的一种。“热”温度被单独确定为感觉疼痛的温度（平均温度 = 46.9 °C）。无痛的“温暖”温度设置为 40 °C。与温暖的刺激相比，参与者认为热刺激更强烈、更令人不快，尤其是在有难闻气味的情况下。强度等级的参数化建模激活了疼痛网络，覆盖了被热刺激激活的大脑区域。气味的存在，无论其价态如何，都会激活杏仁核。此外，杏仁核显示出与右侧缘上回和左侧额上回的刺激依赖性功能耦合。右侧杏仁核和左侧额上回之间的耦合与疼痛体验的强度和不愉快等级有关。我们的结果表明，这些功能连接可能反映了两种感觉方式的整合过程，从而使嗅觉对疼痛体验产生影响。杏仁核显示出与右侧缘上回和左侧额上回的刺激依赖性功能耦合。右侧杏仁核和左侧额上回之间的耦合与疼痛体验的强度和不愉快等级有关。我们的结果表明，这些功能连接可能反映了两种感觉方式的整合过程，从而使嗅觉对疼痛体验产生影响。杏仁核显示出与右侧缘上回和左侧额上回的刺激依赖性功能耦合。右侧杏仁核和左侧额上回之间的耦合与疼痛体验的强度和不愉快等级有关。我们的结果表明，这些功能连接可能反映了两种感觉方式的整合过程，从而使嗅觉对疼痛体验产生影响。