BACKGROUND Chronic orofacial pain (COP) patients often perceive the painful face area as "swollen" without clinical signs; such self-reported illusions of the face are termed perceptual distortion (PD). The pathophysiological mechanisms underlying PD remain elusive. OBJECTIVE To test the neuromodulatory effect of repetitive transcranial magnetic stimulation (rTMS) on PD in healthy individuals, to gain insight into the cortical mechanisms underlying PD. METHODS PD was induced experimentally by injections of local anesthetic (LA) around the infraorbital nerve and measured as perceived size changes of the affected area. Participants were randomly allocated to inhibitory rTMS (n = 26) or sham rTMS (n = 26) group. The participants rated PD at baseline, 6 min after LA, immediately, 20 and 40 min after rTMS. The rTMS (inhibitory and sham) was applied to face (lip) representation area of primary somatosensory cortex (SI) as an intervention at 10 min after the LA, when the magnitude of PD is large. As inhibitory rTMS, continuous theta-burst stimulation paradigm (50 Hz) for 40s was employed to inhibit cortical activity. RESULTS We demonstrated a significant decrease in the magnitude of PD immediately and 20 min after the application of inhibitory rTMS compared with sham rTMS (P < 0.006). In two control experiments, we also showed that peripheral muscle stimulation and stimulation of a cortical region other than the lip representation area had no effect on the magnitude of the PD. CONCLUSIONS Inhibitory rTMS applied to a somatotopical-relevant cortical region modulates PD of the face in healthy individuals and could potentially have therapeutic implications for COP patients.

中文翻译：

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重复经颅磁刺激对改变自己面部感知的影响

背景慢性口面部疼痛(COP) 患者经常将疼痛的面部区域视为“肿胀”而没有临床症状；这种自我报告的面部错觉被称为知觉失真（PD）。PD 的病理生理机制仍然难以捉摸。目的 测试重复经颅磁刺激 (rTMS) 对健康个体 PD 的神经调节作用，以深入了解 PD 的皮层机制。方法通过在眶下神经周围注射局部麻醉剂 (LA) 以实验方式诱导 PD，并根据受影响区域的感知大小变化进行测量。参与者被随机分配到抑制性 rTMS (n = 26) 或假 rTMS (n = 26) 组。参与者在基线、LA 后 6 分钟、rTMS 后立即、20 和 40 分钟对 PD 进行评分。在 LA 后 10 分钟，当 PD 的幅度很大时，将 rTMS（抑制和假手术）应用于初级躯体感觉皮层 (SI) 的面部（唇部）表示区域作为干预。作为抑制性 rTMS，连续 40 秒的 theta-burst 刺激范式 (50 Hz) 被用于抑制皮质活动。结果我们证明，与假 rTMS 相比，应用抑制性 rTMS 后立即和 20 分钟 PD 的程度显着降低（P < 0.006）。在两个对照实验中，我们还表明，外周肌肉刺激和对嘴唇代表区域以外的皮层区域的刺激对 PD 的大小没有影响。