Filingeri Davide, Zhang Hui, Arens Edward A
Center for the Built Environment, University of California at Berkeley, Berkeley, California; and
Environmental Ergonomics Research Centre, Loughborough Design School, Loughborough University, Loughborough, United Kingdom.
J Neurophysiol. 2017 Apr 1;117(4):1797-1806. doi: 10.1152/jn.00845.2016. Epub 2017 Feb 1.
Skin temperature detection thresholds have been used to measure human cold and warm sensitivity across the temperature continuum. They exhibit a sensory zone within which neither warm nor cold sensations prevail. This zone has been widely assumed to coincide with steady-state local skin temperatures between 32 and 34°C, but its underlying neurophysiology has been rarely investigated. In this study we employ two approaches to characterize the properties of sensory thermoneutrality, testing for each whether neutrality shifts along the temperature continuum depending on adaptation to a preceding thermal state. The focus is on local spots of skin on the palm. Ten participants (age: 30.3 ± 4.8 yr) underwent two experiments. established the cold-to-warm inter-detection threshold range for the palm's glabrous skin and its shift as a function of 3 starting skin temperatures (26, 31, or 36°C). For the same conditions, determined a thermally neutral zone centered around a thermally neutral point in which thermoreceptors' activity is balanced. The zone was found to be narrow (0.98 to ~1.33°C), moving with the starting skin temperature over the temperature span 27.5-34.9°C (Pearson = 0.94; < 0.001). It falls within the cold-to-warm inter-threshold range (2.25 to ~2.47°C) but is only half as wide. These findings provide the first quantitative analysis of the local sensory thermoneutral zone in humans, indicating that it does not occur only within a specific range of steady-state skin temperatures (i.e., it shifts across the temperature continuum) and that it differs from the inter-detection threshold range both quantitatively and qualitatively. These findings provide insight into thermoreception neurophysiology. Contrary to a widespread concept in human thermoreception, we show that local sensory thermoneutrality is achievable outside the 32-34°C skin temperature range. We propose that sensory adaption underlies a new mechanism of temperature integration. Also, we have developed from vision research a new quantitative test addressing the balance in activity of cutaneous cold and warm thermoreceptors. This could have important clinical (assessment of somatosensory abnormalities in neurological disease) and applied (design of personal comfort systems) implications.
皮肤温度检测阈值已被用于测量人类在整个温度连续体上的冷觉和热觉敏感度。它们呈现出一个感觉区域，在这个区域内，热觉和冷觉都不占主导。人们普遍认为这个区域与32至34°C之间的稳态局部皮肤温度一致，但其潜在的神经生理学机制却很少被研究。在本研究中，我们采用两种方法来描述感觉性热中性的特性，并针对每种方法测试中性状态是否会根据对先前热状态的适应沿着温度连续体发生变化。重点是手掌上的局部皮肤点。十名参与者（年龄：30.3±4.8岁）进行了两项实验。实验确定了手掌无毛皮肤的冷到热的检测阈值范围及其作为三种起始皮肤温度（26、31或36°C）的函数的变化。在相同条件下，实验确定了一个围绕热中性点的热中性区域，在该区域内热感受器的活动是平衡的。发现该区域很窄（约0.98至约1.33°C），在27.5 - 34.9°C的温度范围内随起始皮肤温度移动（皮尔逊相关系数 = 0.94；P < 0.001）。它落在冷到热的阈值范围（约2.25至约2.47°C）内，但宽度只有其一半。这些发现首次对人类局部感觉性热中性区域进行了定量分析，表明它并非仅出现在特定的稳态皮肤温度范围内（即它会在温度连续体上移动），并且它在数量和质量上都与检测阈值范围不同。这些发现为热感受神经生理学提供了见解。与人类热感受中的一个普遍概念相反，我们表明局部感觉性热中性在32 - 34°C皮肤温度范围之外也是可以实现的。我们提出感觉适应是温度整合新机制的基础。此外，我们从视觉研究中开发了一种新的定量测试方法，用于解决皮肤冷、热感受器活动的平衡问题。这可能对临床（评估神经疾病中的躯体感觉异常）和应用（个人舒适系统设计）具有重要意义。
