Perceived pleasantness of gentle touch in healthy individuals is related to salivary oxytocin response and EEG markers o
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RESEARCH ARTICLE
Perceived pleasantness of gentle touch in healthy individuals is related to salivary oxytocin response and EEG markers of arousal Galina V. Portnova1,5 · Elena V. Proskurnina2 · Svetlana V. Sokolova3 · Ivan V. Skorokhodov4 · Anton A. Varlamov4,5 Received: 22 April 2020 / Accepted: 21 July 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Affective touch plays an important role in human social bonding, affiliative behavior, and in general emotional well-being. A system of unmyelinated low-threshold mechanosensitive C-type afferents innervating hairy skin (C-tactile or CT system) is postulated to provide the neurophysiological background of affective touch perception. C-tactile afferents respond optimally to soft and slow strokes, and this response correlates positively with pleasure ratings of tactile stimuli. As gentle touch is consistently associated with oxytocin release further promoting prosocial behavior, it has been suggested that this effect is mediated by the response of C-tactile afferents. This study assesses a possible link between CT-optimal touch, its subjective pleasantness, EEG indices of cortical arousal, and peripheral oxytocin response. EEG was recorded in 28 healthy volunteers during resting state and tactile stimulation[gentle slow brush strokes on forearm (CT-targeted touch) and palm (non-CTtargeted touch)]. Saliva samples were collected before and after the touch stimulation. Oxytocin concentration increase was significantly associated with greater subjective ratings of CT-targeted touch but not of non-CT-targeted touch, and with lower peak alpha frequency values indicating decreased cortical arousal. The findings suggest that CT-targeted stimulation triggers oxytocin release but only when the touch is perceived at an individual level as having clearly positive affective salience. This corresponds to previous studies reporting that oxytocin response to touch can be related to different personality factors, and bears important implications for planning touch-based interventions in social and medical care. Keywords Affective touch · C-tactile afferents · EEG · Alpha rhythm · Salivary oxytocin · Pleasure
Introduction Social touch plays a vital role in human communication and is important for emotional well-being. The affective component of touch is perceived via C-tactile system—a system of unmyelinated low-threshold mechanosensitive C-type afferents (CT afferents) innervating hairy skin in human and other Communicated by Francesco Lacquaniti.
mammals and providing positive emotional response to slow gentle touch (Olausson et al. 2010; McGlone et al. 2014). CT afferents have been found only in hairy skin in human and other mammals, and they responds optimally to low force stroking touch delivered with velocities of 1–10 cm/s (Löken et al. 2009; McGlone et al. 2014). The information is transmitted via spinothalamic tract and processed in insular cortex in a labelled-line fashion (Björnsdotter et al. 2009), with further forward projections including
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