Department of Clinical, Educational and Health Psychology, University College London, UK.
Department of Psychology, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, UK.
Neuropsychologia. 2018 Jul 31;116(Pt A):136-149. doi: 10.1016/j.neuropsychologia.2017.05.024. Epub 2017 May 29.
Touch is central to interpersonal interactions. Touch conveys specific emotions about the touch provider, but it is not clear whether this is a purely socially learned function or whether it has neurophysiological specificity. In two experiments with healthy participants (N = 76 and 61) and one neuropsychological single case study, we investigated whether a type of touch characterised by peripheral and central neurophysiological specificity, namely the C tactile (CT) system, can communicate specific emotions and mental states. We examined the specificity of emotions elicited by touch delivered at CT-optimal (3cm/s) and CT-suboptimal (18cm/s) velocities (Experiment 1) at different body sites which contain (forearm) vs. do not contain (palm of the hand) CT fibres (Experiment 2). Blindfolded participants were touched without any contextual cues, and were asked to identify the touch provider's emotion and intention. Overall, CT-optimal touch (slow, gentle touch on the forearm) was significantly more likely than other types of touch to convey arousal, lust or desire. Affiliative emotions such as love and related intentions such as social support were instead reliably elicited by gentle touch, irrespective of CT-optimality, suggesting that other top-down factors contribute to these aspects of tactile social communication. To explore the neural basis of this communication, we also tested this paradigm in a stroke patient with right perisylvian damage, including the posterior insular cortex, which is considered as the primary cortical target of CT afferents, but excluding temporal cortex involvement that has been linked to more affiliative aspects of CT-optimal touch. His performance suggested an impairment in 'reading' emotions based on CT-optimal touch. Taken together, our results suggest that the CT system can add specificity to emotional and social communication, particularly with regards to feelings of desire and arousal. On the basis of these findings, we speculate that its primary functional role may be to enhance the 'sensual salience' of tactile interactions.
触摸是人际互动的核心。触摸传达了触摸提供者的特定情感，但目前尚不清楚这是一种纯粹的社会学习功能，还是具有神经生理学特异性。在两项针对健康参与者（N=76 和 61）和一项神经心理学个案研究的实验中，我们研究了一种具有外周和中枢神经生理学特异性的触摸类型，即 C 触觉（CT）系统，是否可以传达特定的情感和心理状态。我们研究了在不同身体部位（包含 CT 纤维的前臂与不包含 CT 纤维的手掌）以 CT 最佳（3cm/s）和 CT 次佳（18cm/s）速度传递的触摸所引起的情感的特异性（实验 1），并研究了 CT 最佳速度（缓慢、轻柔地触摸前臂）和其他类型的触摸在传达唤醒、欲望或性冲动方面的差异。与 CT 最佳速度相关的爱意和社交支持等亲和性情感，无论 CT 最佳速度如何，都能可靠地被轻柔触摸所引发，这表明其他自上而下的因素也会影响触觉社交沟通的这些方面。为了探索这种沟通的神经基础，我们还在一名右大脑外侧裂损伤的中风患者中测试了这一范式，包括被认为是 CT 传入纤维主要皮质靶区的后岛叶皮质，但不包括与 CT 最佳速度相关的更亲和性方面有关的颞叶皮质参与。他的表现表明，他在基于 CT 最佳速度的触摸来“解读”情绪方面存在障碍。总的来说，我们的研究结果表明，CT 系统可以为情感和社交沟通增加特异性，特别是在欲望和唤醒方面。基于这些发现，我们推测其主要功能作用可能是增强触觉互动的“感官显著性”。
