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).

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Characteristics of the CT afferent fibers – core of the affective touch system:

  • Slow-conducting, unmyelinated, mechanosensitive peripheral nerve fibers
  • Abundant in hairy skin (e.g. forearm)
  • Optimal type of stimulation is gentle, moving touch
  • CT-optimal stroking velocities are 1-10 cm/sec (Löken et al., 2009; Ackerley et al., 2014)
  • CT-optimal velocities perceived as more pleasant as compared to slower or faster velocities (Löken et al., 2009; Ackerley et al., 2014)
  • Show a preference for a temperature around 32°C, which corresponds to interpersonal skin-to-skin contact (Ackerley et al., 2014)
  • Activate limbic cortical areas (e.g. insula).

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)

References:

Ackerley, R., Backlund Wasling, H., Liljencrantz, J., Olausson, H., Johnson, R. D., & Wessberg, J. (2014). Human C-Tactile afferents are tuned to the temperature of a skin-stroking caress. The Journal of Neuroscience, 34(8), 2879-2883

Björnsdotter, M., Löken, L., Olausson, H., Vallbo, Å. & Wessberg, J. (2009). Somatotopic organization of gentle touch processing in the posterior insular cortex. Journal of Neuroscience, 29, 9314-9320

Björnsdotter, M., Morrison, I. & Olausson, H. (2010). Feeling good: on the role of C fiber mediated touch in interoception. Experimental brain research, 207, 149-155

Cascio, C., McGlone, F., Folger, S., Tannan, V., Baranek, G., Pelphrey, K., & Essick, G. (2008). Tactile perception in adults with autism: A multidimensional psychophysical study. Journal of Autism and Developmental Disorders, 38, 127–137

Cascio, C.J., Moana-Filho, J., Guest, S., Nebel, M.B., Weisner, J., Baranek, G.T., & Essick, G.K. (2012). Perceptual and Neural Response to Affective Tactile Texture Stimulation in Adults with Autism Spectrum Disorders. Autism Research, 5, 231–244

Craig, A. D. (2002). How do you feel? Interoception: The sense of the physiological condition of the body. Nature Reviews Neuroscience, 3, 655-666

Craig, A. D. (2003). Interoception: The sense of the physiological condition of the body. Current Opinion in Neurobiology, 13, 500-505

Craig, A. D. (2008). Interoception and Emotion: a Neuroanatomical Perspective. In Handbook of Emotion, Third Edition, edited by Lewis, Haviland-Jones, and Barrett

Craig, A. D. (2009). How do you feel-now? The anterior insula and human awareness. Nature Reviews Neuroscience, 10, 59-70

Critchley, H. D., Wiens, S., Rotshtein, P., Öhman, A., & Dolan, R. D. (2004). Neural systems supporting interoceptive awareness.  Nature Neuroscience, 7, 189-195

Croy, I., Luong, A., Triscoli, C., Hofmann, E., Olausson, H., & Sailer, U. (2016). Interpersonal stroking touch is targeted to C tactile afferent activation. Behavioural brain research297, 37-40.

Crucianelli, L., Metcalf, N. K., Fotopoulou, A. K., & Jenkinson, P. M. (2013). Bodily pleasure matters: velocity of touch modulates body ownership during the rubber hand illusion. Frontiers in psychology, 4, 703.

Crucianelli, L., Cardi, V., Treasure, J., Jenkinson, P. M., & Fotopoulou, A. (2016). The perception of affective touch in anorexia nervosa. Psychiatry research, 239, 72-78.

Damasio A.  (2010). Self Comes to Mind: Constructing the Conscious Brain. Pantheon

Dijkerman, H.C. (2015). How do different aspects of self-consciousness interact?  Trends in cognitive sciences, 19(8), 427-428

Ebisch, S. J., Ferri, F., & Gallese, V. (2014). Touching moments: desire modulates the neural anticipation of active romantic caress. Frontiers in behavioral neuroscience8(60), 1-12

Ellingsen, D. M., Wessberg, J., Eikemo, M., Liljencrantz, J., Endestad, T., Olausson, H., & Leknes, S. (2013). Placebo improves pleasure and pain through opposite modulation of sensory processing. Proceedings of the National Academy of Sciences110(44), 17993-17998

Ellingsen, D. M., Wessberg, J., Chelnokova, O., Olausson, H., Laeng, B., & Leknes, S. (2014). In touch with your emotions: oxytocin and touch change social impressions while others’ facial expressions can alter touch. Psychoneuroendocrinology39, 11-20

Ellingsen, D. M., Leknes, S., Løseth, G., Wessberg, J., & Olausson, H. (2015). The neurobiology shaping affective touch: Expectation, motivation, and meaning in the multisensory context. Frontiers in Psychology6

Field, T. (2001). Massage terapy facilitates weight gain in preterm infants. Current Directions in Psychological Science, 10(2), 51-54

Gallace, A., & Spence, C. (2010). The science of interpersonal touch: an overview. Neuroscience and Biobehavioral Reviews, 34(2), 246-259

Gentsh, A., Panagiotopolou, E., Fotopoulou, A., 2015. Active interpersonal touch gives rise to the Social Softness Illusion. Current Biology, 25(18), 2392-2397

Hertenstein, M. J., Keltner, D., App, B., Bulleit, B. A., & Jaskolka, A. R. (2006). Touch communicates distinct emotions. Emotion, 6(3), 528-533

Hertenstein, M. J., Verkamp, J. M., Kerestes, A. M., & Holmes, R. M. (2006). The communicative functions of touch in humans, nonhuman primates, and rats: a review and synthesis of the empirical research. Genetic Social and General Psychology Monographs, 132(1), 5-94

Jönsson, E. H., Backlund Wasling, H., Wagnbeck, V., Dimitriadis, M., Georgiadis, J. R., Olausson, H., & Croy, I. (2015). Unmyelinated tactile cutaneous nerves signal erotic sensations. The journal of sexual medicine12(6), 1338-1345.

Krahé, C., Drabek, M. M., Paloyelis, Y., & Fotopoulou, A. (2016). Affective touch and attachment style modulate pain: a laser-evoked potentials study. Phil. Trans. R. Soc. B, 371(1708), 20160009.

Lloyd, D.M., Gillis, V., Lewis, E., Farrell, M.J., & Morrison, I. (2013). Pleasant touch moderates the subjective but not objective aspects of body perception. Frontiers in Behavioral Neuroscience, 7, 207

Löken, L. S., Wessberg, J., Morrison, I., McGlone F. & Olausson, H. (2009). Coding of pleasant touch by unmyelinated afferents in human. Nature Neuroscience, 12, 547-548

McCabe, C., Rolls, E. T., Bilderbeck, A., & McGlone, F. (2008). Cognitive influences on the affective representation of touch and the sight of touch in the human brain. Social Cognitive and Affective Neuroscience, 3(2), 97-108

McGlone, F., Vallbo, Å. B., Olausson, H., Löken, L. & Wessberg, J. (2007). Discriminative touch and emotional touch. Canadian Journal of Experimental Psychology, 61, 173-183

McGlone, F., Olausson, H., Boyle, J. A., Jones-Gotman, M., Dancer, C., Guest, S. & Essick, G. (2012). Touching and feeling: Differences in pleasant touch processing between glabrous and hairy skin in humans. European Journal Neuroscience, 35, 1782-1788

McGlone, F., Wessberg, J., & Olausson, H. (2014). Discriminative and affective touch: sensing and feeling. Neuron82(4), 737-755

McGlone, F., Cerritelli, F., Walker, S., & Esteves, J. (2017). The role of gentle touch in perinatal osteopathic manual therapy. Neuroscience & Biobehavioral Reviews72, 1-9.

Montagu, A. (1971). Touching: The human significance of the skin.

Morrison, I., Löken, L., & Olausson, H. (2010). The skin as a social organ.  Experimental  Brain Research, 204, 305–314

Morrison, I., Björnsdotter, M., & Olausson, H. (2011). Vicarious responses to social touch in posterior insular cortex are tuned to pleasant caressing speeds.  Journal of Neuroscience, 31, 9554-9562

Olausson, H., Lamarre, Y., Backlund, H., Morin, C., Wallin, B. G., Starck, G., Ekholm, S., Strigo, I., Worsley, K., Vallbo, Å.B., & Bushnell, M. C. (2002). Unmyelinated tactile afferents signal touch and project to insular cortex. Nature Neuroscience, 5, 900-904.

Olausson, H.W., Cole, J., Vallbo, Å., McGlone, F., Elam, M., Krämer, H.H., Rylander, K., Wessberg, J., & Bushnell, M.C. (2008). Unmyelinated tactile afferents have opposite effects on insular and somatosensory cortical processing. Neuroscience Letters, 436, 128–132

Olausson, H., Wessberg, J., McGlone, F., & Vallbo, Å. (2010). The neurophysiology of unmyelinated tactile afferents. Neuroscience & Biobehavioral Reviews34(2), 185-191

Sharp, H., Pickles, A., Meaney, M., Marshall, K., Tibu, F. & Hill, J. (2012). Frequency of infant stroking reported by mothers moderates the effect of prenatal depression on infant behavioural and physiological outcomes. PLoS One, 7 (10

Vallbo, Å. B., Olausson , H., & Wessberg, J. (1999). Unmyelinated afferents constitute a second system coding tactile stimuli of the human hairy skin. Journal of Neurophysiology, 81, 2753

Van Stralen, H.E., van Zandvoort, M.J.E., Hoppenbrouwers, S.S., Vissers, L.M.G., Kappelle, L.J., & Dijkerman, H.C. (2014). Affective touch modulates the rubber hand illusion. Cognition, 131, 147–158

Voos, A.C., Pelphrey, K., & Kaiser, M.D. (2013). Autistic traits are associated with diminished neural response to affective touch. Social Cognitive and Affective Neuroscience, 8, 378–386

Walker, S., Trotter, P., Swaney, W., Marshall, A., & Mcglone, F. (2017). C-tactile afferents: Cutaneous mediators of oxytocin release during affiliative tactile interactions?. Neuropeptides.

Walker, S. C., Trotter, P. D., Woods, A., & McGlone, F. (2017). Vicarious ratings of social touch reflect the anatomical distribution & velocity tuning of C-tactile afferents: A hedonic homunculus?. Behavioural Brain Research320, 91-96.