Department of Psychology, University of Milano-Bicocca, Piazza dell'Ateneo Nuovo 1, 20126 Milano, Italy; Laboratory of Neuropsychology, IRCCS Istituto Auxologico Italiano, Via Mercalli 32, 20122 Milano, Italy.
Department of Psychology, University of Milano-Bicocca, Piazza dell'Ateneo Nuovo 1, 20126 Milano, Italy; Laboratory of Neuropsychology, IRCCS Istituto Auxologico Italiano, Via Mercalli 32, 20122 Milano, Italy.
Curr Biol. 2014 Jul 7;24(13):1513-7. doi: 10.1016/j.cub.2014.05.025. Epub 2014 Jun 19.
Touch has an emotional and communicative meaning, and it plays a crucial role in social perception and empathy. The intuitive link between others' somatosensations and our sense of touch becomes ostensible in mirror-touch synesthesia, a condition in which the view of a touch on another person's body elicits conscious tactile sensations on the observer's own body [1]. This peculiar phenomenon may implicate normal social mirror mechanisms [2]. Here, we show that mirror-touch interference effects, synesthesia-like sensations, and even phantom touches can be induced in nonsynesthetes by priming the primary somatosensory cortex (SI) directly or indirectly via the posterior parietal cortex. These results were obtained by means of facilitatory paired-pulse transcranial magnetic stimulation (ppTMS) contingent upon the observation of touch. For these vicarious effects, the SI is engaged at 150 ms from the onset of the visual touch. Intriguingly, individual differences in empathic abilities, assessed with the Interpersonal Reactivity Index [3], drive the activity of the SI when nonsynesthetes witness others' tactile sensations. This evidence implies that, under normal conditions, touch observation activates the SI below the threshold for perceptual awareness [4]; through the visual-dependent tuning of SI activity by ppTMS, what is seen becomes felt, namely, mirror-touch synesthesia. On a broader perspective, the visual responsivity of the SI may allow an automatic and unconscious transference of the sensation that another person is experiencing onto oneself, and, in turn, the empathic sharing of somatosensations [2].
触摸具有情感和交流的意义，它在社会感知和同理心方面起着至关重要的作用。在镜像触摸联觉中，他人的躯体感觉和我们的触觉之间存在直观的联系，这种情况是指看到别人身上的触摸会引起观察者自身身体的有意识触觉。这种奇特的现象可能暗示着正常的社会镜像机制。在这里，我们通过在观察触摸时直接或间接地对初级体感皮层（SI）进行促进性成对脉冲经颅磁刺激（ppTMS），在非联觉者中诱导出镜像触摸干扰效应、类似联觉的感觉，甚至是幻影触摸。这些结果是通过触观诱发的易化性成对经颅磁刺激获得的。对于这些替代效应，SI 在视觉触摸开始后 150 毫秒时被激活。有趣的是，个体差异在同理心能力方面，通过人际反应指数进行评估，当非联觉者见证他人的触觉时，会驱动 SI 的活动。这一证据表明，在正常情况下，触摸观察会在感知阈下激活 SI[4]；通过 ppTMS 对 SI 活动的视觉依赖性调整，所见即所感，即镜像触摸联觉。从更广泛的角度来看，SI 的视觉反应性可能允许将他人正在经历的感觉自动而无意识地转移到自己身上，并且反过来又可以分享躯体感觉。
