University of Milano - Bicocca, Department of Psychology, Italy; NeuroMi, Milan Center for Neuroscience, Italy.
Politecnico di Milano, Department of Mechanical Engineering, Italy.
Neuroscience. 2021 Jun 1;464:59-66. doi: 10.1016/j.neuroscience.2020.07.007. Epub 2020 Jul 11.
The human tactile system is known to discriminate different types of touches, one of these termed 'affective touch', is mainly mediated by slow conducting tactile afferents (CT fibres), which are preferentially activated by slow and gentle strokes. Human infants experience self-generated tactile stimulation during prenatal life, and they receive a large amount of affectionate touches by their caregivers from birth. This early and extended experience with tactile stimulation may likely make infants particularly sensitive to affective touch, and increasing evidence shows that this may indeed be the case. However, infants commonly experience affective touch in the context of social interactions with familiar adults (e.g., while looking at their caregiver), and recent evidence suggests that this helps them assigning affiliative and communicative meaning to the touch they are perceiving. Here we investigated the presence of visual-tactile interactions in 4-5-month-old infants' physiological (i.e., skin conductance) and behavioural (i.e., visual looking times) responses to visual and tactile stimulation of affective/social nature when the sources of both stimulation are not familiar to the infant. To explore whether the modulation of physiological arousal elicited by the socially-relevant bimodal stimulation is specific to infants or extends into adulthood, we also tested a group of adults. Infants (N = 25) and adults (N = 25) were stimulated on their forearm through slow stroking (i.e. affective touch) or tapping (i.e. non-affective touch) during the observation of dynamic images of socially-relevant (i.e., an unfamiliar face) and non-socially-relevant (i.e., a house) stimuli. We found that the simultaneous presentation of socially-relevant visual-tactile stimuli significantly decreased infants' - but not the adults' - electrodermal response, suggesting that infants easily integrate low-level properties of affective touch with socially salient visual information, and that social experience may tune and change sensitivity to affective touch across the life-span.
人类触觉系统能够区分不同类型的触感，其中一种被称为“情感触觉”，主要由慢传导触觉传入纤维（CT 纤维）介导，这些纤维优先被缓慢而轻柔的笔触激活。人类婴儿在产前生活中会经历自身产生的触觉刺激，并且从出生起就会从照顾者那里获得大量的情感触摸。这种早期和广泛的触觉刺激体验可能使婴儿对情感触觉特别敏感，越来越多的证据表明情况确实如此。然而，婴儿通常在与熟悉的成年人进行社交互动的背景下体验情感触觉（例如，在看着照顾者时），最近的证据表明，这有助于他们将触觉与情感联系起来，并赋予其交流意义。在这里，我们研究了 4-5 个月大的婴儿在视觉和触觉刺激为情感/社交性质时，对视觉和触觉刺激的生理（即皮肤电导）和行为（即视觉注视时间）反应中是否存在视觉-触觉相互作用，当刺激源对婴儿来说都不熟悉时。为了探索由与社会相关的双模态刺激引起的生理唤醒的调制是否仅针对婴儿，还是扩展到成年期，我们还测试了一组成年人。婴儿（N=25）和成年人（N=25）在前臂上接受缓慢stroking（即情感触觉）或轻敲（即非情感触觉）刺激，同时观察与社会相关的（即不熟悉的面孔）和非社会相关的（即房子）动态图像。我们发现，同时呈现与社会相关的视觉-触觉刺激显著降低了婴儿的皮肤电反应，但没有降低成年人的皮肤电反应，这表明婴儿可以轻松地将情感触觉的低水平属性与社会相关的视觉信息整合在一起，并且社会经验可能会在整个生命周期中调节和改变对情感触觉的敏感性。
