The role of our skin in reading emotion
The giving of caring and emotionally present touch is foundational to my practice as a bodyworker. In fact, I’ve previously written about the importance of caring touch from my own experience as a massage therapy client, in a blog post called A Tale of Two Lomis. So, when I first learned of a special kind of nerve fibre in the skin that discerns the emotional aspect of touch, I was eager to find out more.
Our skin is a sensory wonder
Skin is the largest organ of the human body. One square inch of our skin has approximately 19 million skin cells, 650 sweat glands, 20 blood vessels, and more than 1,000 nerve endings. These nerve endings sense:
Temperature (thermoception).
Pain (nociception).
Pressure, vibration, muscle stretch, and the movement of hair (mechanoreception).
Balance (equilibrioception).
Position and movement of the body (proprioception).
This information is sent to the brain by a range of sensory nerve fibres including A-fibres and C-fibres. A-fibres convey information to the brain quickly, such as at the point of touching a very hot surface, when we need to respond immediately to avoid damage to the body. C-fibres convey information to the brain more slowly, such as the kind of dull or aching pain that occurs with a delay after accidentally whacking your thumb with a hammer. The primary destination for all these signals is the brain’s somatosensory cortex, where sensory information from the body is processed.
A nerve fibre with a unique job
In addition to A-fibres and C-fibres that convey factual aspects of the body’s experience, the C-fibre group has another kind of nerve fibre called C-Tactile afferents (C-T fibres), which have an entirely different job and a different destination for their signals. C-T fibres discern and convey the emotional tone of interpersonal touch. Under the right conditions, these signals of care and psychological safety are activated and are sent to the insular cortex region of the brain, which is linked with the processing of emotion.
The C-T fibre and its unique function was identified and described in 1993 by Swedish physiologist, Åke Vallbo and team. Vallbo’s and other teams’ research since has shown that C-T fibres:
Cover most of the body, in the skin that has hair (including skin with the tiniest of hairs such as the inside of the arms or behind the knees). They are not present in the highly sensory glabrous skin of e.g. the lips, palms of the hands, and soles of the feet.
Activate most in response to slow, lighter touch, which is associated with the formation and strengthening of social bonds.
Can produce a diffuse sense of wellbeing.
May be accompanied by lowered heart rate, lowered blood pressure, slower breathing rate, and reduced pain.
May support body self-awareness and sense of autonomy by producing higher levels of subjective ‘body ownership’ feelings and sensations.
Further research has indicated that the activation of C-T fibres is significantly affected by interpersonal context, suggesting a physiological underpinning to what most of us know from experience. For example:
Touch will feel different if delivered by a person we know and trust compared with touch delivered by a stranger.
Touch by a partner, friend or family member will feel different if it occurs when the relationship is in harmony compared with when there is an unresolved disagreement.
Whether touch is wanted or not will significantly affect how it is experienced.
Trust, harmony and consent are therefore fundamental to our positive experience of touch – no surprises there! But, the C-T fibre research tells us of an identified neurobiological component to this emotionally warm experience.
The joy of continuous discovery
As mentioned above, the research has identified an optimal speed and pressure for the maximum activation of C-T fibres – touch that is both slow and light. I have intuitively slowed the speed of my bodywork over the years, especially with holistic massage, but the pressure is definitely medium or firm depending on client preference – that’s the nature of most massage therapy! However, the research indicates that C-T fibres do respond to slow touch that is firmer, albeit less intensively than lighter touch generates.
As a massage therapist, it has been fascinating to dig into this research and learn that there are special sensory nerve fibres that play a part in the discerning of emotional tone, alongside the body’s other interconnected mechanisms of perception. I hope readers find it interesting too, and that it may bring useful awareness to how you touch the people in your life.
This exercise has served to remind me of the kaleidoscopic interoperability of the systems of the human body. I’m more humbled than ever by the multi-system complexity and brilliance of our bodies. Studying and working with the universe of the body (and mind) to support my clients in their journeys of healing, development and wellbeing is a privilege – and a voyage of discovery without end.
References
Gentsche, A., Crucianelli, L., Jenkinson, P., & Fotopoulou, A. (2016). The Touched Self: Affective Touch and Body Awareness in Health and Disease. In H. Olausson, J. Wessberg, I Morrison & F McGlone (Eds.), Affective Touch and the Neurophysiology of CT Afferents (pp 355-384). New York: Springer Nature.
Linden, D. (2015). Touch: The Science of the Sense that Makes Us Human. Great Britain: Viking.
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. Front Behav Neurosci, 7, 207.
Löken, L. S., Wessberg, J., Morrison, I., McGlone, F., & Olausson, H. (2009). Coding of pleasant touch by unmyelinated afferents in humans. Nat Neurosci, 12(5), 547-548.
Subramanian, S. (2021). How to Feel: The Science and Meaning of Touch. India: Harper Collins.
Vallbo, Å.B., Olausson, H., Wessberg, J., & Norrsell, U. (1993). A system of unmyelinated afferents for innocuous mechanoreception in the human skin. Brain Research 628(1-2), 301-304.
Vallbo, Å.B., Olausson, H., & Wessberg, J. (1999). Unmyelinated afferents constitute a second system coding tactile stimuli of the human hairy skin. J Neurophysiol, 81(6), 2753-2763.
Photo by Robin Sherman