The sensory experience of touch provides a unique contribution to the formation and maintenance of social bonding, promoting affiliative, collaborative and sexual behaviour (Suvilehto et al., 2015). Similarly, interpersonal touch plays a crucial role in social communication, with gentle slow touch conveying social support. The beneficial effects of touch can be traced back to early life, where maternal touch has been found to shape the developing “social brain” of an infant (Brauer et al., 2016), and continue to be important throughout the lifespan.
Yet not all touch is the same. Research has shown that we have a specialised neurophysiological system that mediates the affective, rather than the discriminative properties of touch (Olausson et al. 2002; McGlone et al. 2007). This system, so called CT-afferent system, is tuned to comforting caress-like interpersonal touch (i.e. affective touch; Olausson et al. 2010).
Characteristics of the CT afferent fibers – core of the affective touch system:
- Slow-conducting, unmyelinated, mechanosensitive peripheral nerve fibers
- Found only in hairy skin (e.g. forearm) and not on the glabrous skin (e.g. palm of the hand)
- Optimal type of stimulation is gentle stroking
- Show a preference for a temperature of approximately 32°C, which corresponds to interpersonal skin-to-skin contact and very low indentation forces ranging from 3 to 2.5 mN (Ackerley et al., 2014)
- CT-optimal stroking velocities are 1-10 cm/sec (Löken et al., 2009)
- CT-optimal velocities perceived as more pleasant as compared to slower or faster velocities (Löken et al., 2009)
- Activate limbic cortical areas.
Some implications of affective touch
- Contributes to the send of body ownership, and by implication to the psychological self (Crucianelli et al. 2013, Lloyd et al. 2013; van Stralen et al. 2014)
- Patients with Anorexia Nervosa, a psychiatric disorder characterised by body image distortions and lack of awareness, show impairment in the perception of affective touch ( Crucianelli et al. 2016)
- Modulates pain (Krahé et al. 2016; Liljencrantz et al. 2016)
- Mediates erotic tactile stimulation (Jönsson et al. 2015).
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