Ackerley Rochelle, Carlsson Ida, Wester Henric, Olausson Håkan, Backlund Wasling Helena
Department of Physiology, University of Gothenburg Gothenburg, Sweden ; Clinical Neurophysiology, Sahlgrenska University Hospital Gothenburg, Sweden.
Clinical Neurophysiology, Sahlgrenska University Hospital Gothenburg, Sweden.
Front Behav Neurosci. 2014 Feb 19;8:54. doi: 10.3389/fnbeh.2014.00054. eCollection 2014.
Human skin is innervated with different tactile afferents, which are found at varying densities over the body. We investigate how the relationships between tactile pleasantness, sensitivity and discrimination differ across the skin. Tactile pleasantness was assessed by stroking a soft brush over the skin, using five velocities (0.3, 1, 3, 10, 30 cm s(-1)), known to differentiate hedonic touch, and pleasantness ratings were gained. The ratings velocity-profile is known to correlate with firing in unmyelinated C-tactile (CT) afferents. Tactile sensitivity thresholds were determined using monofilament force detection and the tactile discrimination level was obtained in the direction discrimination of a moving probe; both tasks readily activate myelinated touch receptors. Perceptions were measured over five skin sites: forehead, arm, palm, thigh and shin. The assessment of tactile pleasantness over the skin resulted in a preference for the middle velocities (1-10 cm s(-1)), where higher ratings were gained compared to the slowest and fastest velocities. This preference in tactile pleasantness was found across all the skin sites, apart from at the palm, where no decrease in pleasantness for the faster stroking velocities was seen. We find that tactile sensitivity and discrimination vary across the skin, where the forehead and palm show increased acuity. Tactile sensitivity and discrimination levels also correlated significantly, although the tactile acuity did not relate to the perceived pleasantness of touch. Tactile pleasantness varied in a subtle way across skin sites, where the middle velocities were always rated as the most pleasant, but the ratings at hairy skin sites were more receptive to changes in stroking velocity. We postulate that although the mechanoreceptive afferent physiology may be different over the skin, the perception of pleasant touch can be interpreted using all of the available incoming somatosensory information in combination with central processing.
人类皮肤由不同的触觉传入神经支配，这些神经在身体上的分布密度各不相同。我们研究了触觉愉悦度、敏感度和辨别力之间的关系在整个皮肤表面是如何不同的。通过用软刷以五种速度（0.3、1、3、10、30厘米/秒）在皮肤上轻抚来评估触觉愉悦度，这五种速度已知可区分享乐性触觉，并获得愉悦度评分。已知评分速度曲线与无髓鞘C触觉（CT）传入神经的放电相关。使用单丝力检测确定触觉敏感度阈值，并在移动探针的方向辨别中获得触觉辨别水平；这两项任务都能轻易激活有髓鞘的触觉感受器。在五个皮肤部位进行了感知测量：额头、手臂、手掌、大腿和小腿。对皮肤触觉愉悦度的评估结果显示，人们偏好中等速度（1 - 10厘米/秒），与最慢和最快速度相比，中等速度能获得更高的评分。除了手掌部位，在所有皮肤部位都发现了这种触觉愉悦度偏好，在手掌部位，较快的轻抚速度并没有使愉悦度降低。我们发现，触觉敏感度和辨别力在整个皮肤表面存在差异，额头和手掌的敏锐度更高。触觉敏感度和辨别水平也显著相关，尽管触觉敏锐度与触觉的感知愉悦度无关。触觉愉悦度在不同皮肤部位有细微差异，中等速度总是被评为最愉悦的，但多毛皮肤部位的评分对轻抚速度的变化更敏感。我们推测，尽管皮肤各处的机械感受性传入神经生理学可能不同，但可以结合所有可用的传入体感信息并通过中枢处理来解释愉悦触觉的感知。
