Scientific Institute, IRCCS E. Medea, 0-3 Center for the at-Risk Infant, Via Don Luigi Monza 20, 23842 Bosisio Parini (LC), Italy.
PhD Program in Neural and Cognitive Sciences, Department of Life Sciences, University of Trieste, Via Licio Giorgieri 5, 34127 Trieste, Italy.
Cereb Cortex. 2024 Nov 5;34(11). doi: 10.1093/cercor/bhae441.
Understanding observed interpersonal touch, particularly the so-called affective touch targeting the CT fibers, is essential for social interactions. Research has documented that observing other people being touched activates the same cortical areas involved in direct tactile experiences. However, observing interpersonal touch also activates an inner simulation of the movements in the observer's motor system. Given the social and affective significance of CT-optimal touch, the present study tested the hypothesis that observing stroking touches targeting or not targeting the CT fibers system might distinctly influence motor resonance to vicarious touch. With this aim, we used single-pulse transcranial magnetic stimulation and motor-evoked potentials recording while participants observed video clips of interpersonal touch events at different stroking velocities. We found a modulation of motor system activity, particularly a decrease in corticospinal excitability, when observing CT-optimal touch as opposed to non-CT-optimal velocities, a mechanism that might aid in understanding the touchee's feelings during vicarious interpersonal touch. Moreover, participants with higher reliance on bodily cues to be emotionally aware showed greater motor suppression for CT-optimal compared to non-CT-optimal velocities. These results shed light on the complex interplay between motor and somatosensory systems in social touch perception and emphasize the importance of affective touch in human social interactions.
理解观察到的人际触摸，特别是针对 CT 纤维的所谓情感触摸，对于社交互动至关重要。研究已经记录到，观察到其他人被触摸会激活与直接触觉体验相关的相同皮质区域。然而，观察人际触摸也会激活观察者运动系统内部的运动模拟。鉴于 CT 最佳触摸的社会和情感意义，本研究检验了以下假设：观察针对或不针对 CT 纤维系统的抚摸触摸可能会明显影响替代触摸的运动共鸣。为此，我们使用单脉冲经颅磁刺激和运动诱发电位记录，同时参与者观察不同抚摸速度的人际触摸事件的视频片段。我们发现，当观察 CT 最佳触摸时，运动系统的活动会发生调制，特别是皮质脊髓兴奋性会降低，而当观察非 CT 最佳速度时则不会，这种机制可能有助于理解替代人际触摸中被触摸者的感受。此外，对于情感意识更多地依赖身体线索的参与者，与非 CT 最佳速度相比，他们对 CT 最佳速度的运动抑制更大。这些结果揭示了运动和躯体感觉系统在社会触摸感知中的复杂相互作用，并强调了情感触摸在人类社交互动中的重要性。
