Pain demands attention, yet pain can be reduced by focusing attention elsewhere. The neural processes involved in this robust psychophysical phenomenon, attentional analgesia, are still being defined. Our previous fMRI study linked activity in the brainstem triad of locus coeruleus (LC), rostral ventromedial medulla (RVM) and periaqueductal grey (PAG) with attentional analgesia. Here we identify and model the functional interactions between these regions and the cortex in healthy human subjects (n=57), who received painful thermal stimuli whilst simultaneously performing a visual attention task. RVM activity encoded pain intensity while contralateral LC activity correlated with attentional analgesia. Psycho-Physiological Interaction analysis and Dynamic Causal Modelling identified two parallel paths between forebrain and brainstem. These connections are modulated by attentional demand: a bidirectional anterior cingulate cortex (ACC) - right-LC loop, and a top-down influence of task on ACC-PAG-RVM. By recruiting discrete brainstem circuits, the ACC is able to modulate nociceptive input to reduce pain in situations of conflicting attentional demand.

中文翻译：

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注意镇痛的平行皮质-脑干通路

疼痛需要注意，但可以通过将注意力集中在其他地方来减轻疼痛。这种强大的心理物理现象所涉及的神经过程，即注意力镇痛，仍在定义中。我们之前的 fMRI 研究将蓝斑 (LC)、延髓腹内侧 (RVM) 和导水管周围灰质 (PAG) 脑干三联体的活动与注意力镇痛联系起来。在这里，我们识别并模拟这些区域与健康人类受试者（n = 57）的皮层之间的功能相互作用，他们在接受痛苦的热刺激的同时执行视觉注意任务。RVM 活动编码疼痛强度，而对侧 LC 活动与注意力镇痛相关。心理生理交互分析和动态因果建模确定了前脑和脑干之间的两条平行路径。这些连接由注意力需求调节：双向前扣带皮层 (ACC) - 右 LC 环，以及任务对 ACC-PAG-RVM 的自上而下影响。通过招募离散的脑干回路，ACC 能够调节伤害性输入，以减少注意力需求冲突情况下的疼痛。