Abstract：
Paradoxical heat sensation (PHS) and the thermal grill illusion (TGI) are both related to the perception of warmth or heat from innocuous cold stimuli. Despite being described as similar perceptual phenomena, recent findings suggested that PHS is common in neuropathy and related to sensory loss, while TGI is more frequently observed in healthy individuals. To clarify the relationship between these two phenomena, we conducted a study in a cohort of healthy individuals to investigate the association between PHS and TGI. We examined the somatosensory profiles of 60 healthy participants (34 females, median age 25 years) using the quantitative sensory testing (QST) protocol from the German Research Network on Neuropathic Pain. The number of PHS was measured using a modified thermal sensory limen (TSL) procedure where the skin was transiently pre-warmed, or pre-cooled before the PHS measure. This procedure also included a control condition with a pre-temperature of 32 °C. The number of TGI responses was quantified during simultaneous application of warm and cold innocuous stimuli. All participants had normal thermal and mechanical thresholds compared to the reference values from the QST protocol. Only two participants experienced PHS during the QST procedure. In the modified TSL procedure, we found no statistically significant differences in the number of participants reporting PHS in the control condition (N = 6) vs. pre-warming (N = 3; min = 35.7 °C, max = 43.5 °C) and pre-cooling (N = 4, min = 15.0 °C, max = 28.8 °C) conditions. Fourteen participants experienced TGI, and only one participant reported both TGI and PHS. Individuals with TGI had normal or even increased thermal sensation compared to individuals without TGI. Our findings demonstrate a clear distinction between individuals experiencing PHS or TGI, as there was no overlap observed when using identical warm and cold temperatures that were alternated either temporally or spatially. While PHS was previously related to sensory loss, our study revealed that TGI is associated with normal thermal sensitivity. This suggests that an efficient thermal sensory function is essential in generating the illusory sensation of pain of the TGI.
摘要：
矛盾的热感觉（PHS）和热格栅错觉（TGI）都与无害的冷刺激对温暖或热量的感知有关。尽管被描述为类似的感知现象，最近的发现表明，PHS在神经病变中很常见，与感觉丧失有关，而TGI在健康个体中更常见。为了弄清这两种现象之间的关系，我们在一组健康个体中进行了一项研究,以调查PHS与TGI之间的关联.我们检查了60名健康参与者(34名女性，中位年龄25岁），使用德国神经性疼痛研究网络的定量感觉测试（QST）方案。使用改良的热感觉石灰（TSL）程序测量PHS的数量，其中皮肤暂时预热，或在PHS测量前预冷。该程序还包括预温度为32°C的控制条件。在同时施加热和冷无害刺激期间量化TGI反应的数量。与QST方案的参考值相比，所有参与者都具有正常的热阈值和机械阈值。在QST过程中，只有两名参与者经历了PHS。在修改后的TSL程序中，我们发现在对照条件下报告PHS的参与者数量（N=6）与预热(N=3；min=35.7°C，max=43.5°C)和预冷(N=4,min=15.0°C,max=28.8°C)条件。14名参与者经历了TGI，只有一名参与者同时报告了TGI和PHS。与没有TGI的个体相比,具有TGI的个体具有正常或甚至增加的热感觉。我们的研究结果表明，经历PHS或TGI的个体之间存在明显的区别，因为当使用时间或空间上交替的相同的温暖和寒冷温度时，没有观察到重叠。虽然小灵通以前与感觉丧失有关，我们的研究表明，TGI与正常的热敏感性有关。这表明有效的热感觉功能对于产生TGI的疼痛的虚幻感觉至关重要。
