Touch – The Forgotten Sense with Professor Francis McGlone #45
Professor Francis McGlone, a world-leading researcher, explains how human touch is a biological necessity, not an indulgence. He discusses the critical role of C-tactile afferents in social brain development, stress resilience, and emotional well-being, highlighting the devastating consequences of touch deprivation in modern society.
Deep Dive Analysis
13 Topic Outline
Touch as a Biological Necessity and Two Types of Touch
The Fast Touch System vs. Slow C-Tactile Fibers
Insights from Patients Lacking Fast Touch Nerves
The Emotional Quality of Pain and Touch
Societal Implications of Decreased Touch
Early Life Touch, Epigenetics, and Stress Resilience
Impact of Lack of Touch on Preterm Infants and Autism
The 'Back in the Sack' Project for Preterm Infants
Historical Research on Attachment and Touch (Harlow's Monkeys)
Optimal Stroking Speed for C-Tactile Afferents
Modern Society's Disconnect from Affiliative Touch
Reversibility of Lack of Touch and Loneliness
Overcoming Societal Aversion to Appropriate Touch
9 Key Concepts
Fast Touch System
This system uses myelinated nerve fibers that conduct information rapidly (milliseconds) to the brain. It's responsible for immediate, discriminative touch, such as feeling an object slip or detecting a fly, and is crucial for tasks like reading Braille or knowing body position (proprioception).
C-Tactile Afferents (CTs)
These are a special class of slow-conducting, unmyelinated C-fibers found in the hairy skin of social mammals, but not in glabrous skin (palms, soles). They respond to gentle, stroking touch and are fundamental for nurturing, bonding, and regulating emotional affective states.
Glabrous Skin
This refers to the hairless skin found on the palms of the hands, soles of the feet, and to some extent, the lips. This skin is primarily involved in exploring the outside world, manipulating objects, and fine discriminative tasks, and does not contain C-tactile afferents.
Somatosensation
This is the scientific field dedicated to the study of body sensations, encompassing various forms of touch, temperature, pain, and proprioception. Most research in this area has historically focused on the fast, discriminative aspects of touch.
Neuronopathy
A condition that causes damage to nerve fibers, specifically mentioned in the context of patients who have lost all their fast-touch nerves below the neck. This condition severely impairs their ability to feel touch and proprioception, making movement extremely difficult without visual compensation.
Proprioception
The sense of knowing where one's body parts are in space without looking. This is mediated by fast-conducting myelinated nerve fibers located in muscles and joints, and its absence (as in neuronopathy) makes coordinated movement nearly impossible.
Epigenetics
This field recognizes that environmental factors can shape how certain genes are turned on and off, influencing development and traits. It highlights how early life experiences, such as the presence or absence of touch, can profoundly impact gene expression related to stress regulation.
Connectome
A complete map of how all neurons in a brain communicate with each other to control behavior. While mapping the human connectome is a massive ongoing project, the connectome of the simple worm C. elegans (302 neurons) took 12 years to fully map.
Perceived Norms
This concept describes how an individual's perception of a risk can be influenced and magnified by media reporting, even if the statistical risk remains minimal. This can lead to widespread anxiety or changes in behavior, such as increased wariness about social touch.
7 Questions Answered
There's a fast touch system, mediated by myelinated nerve fibers, that provides immediate, discriminative information about external objects and body position. The other is a slow touch system, mediated by C-tactile afferents, which responds to gentle, affiliative touch and plays a crucial role in emotional regulation and social bonding.
Research shows that specific nerve fibers (C-tactile afferents) have evolved in social mammals to respond to affiliative contact, playing a fundamental role in the development of the social brain, nurture, bonding, and even resilience to stress.
A lack of nurturing touch during critical developmental periods, such as seen in Romanian orphanages or preterm infants, can lead to severe behavioral, psychological, and cognitive deficits, impacting the normal functioning of the social brain and stress resilience throughout life.
C-tactile afferents are specifically tuned to respond most strongly to stroking velocities of about 3 to 5 centimeters per second, which is the instinctive speed humans use when stroking a baby or a loved one.
A touch-averse society, driven by fear of inappropriate touch and increased digital interaction, risks diminishing opportunities for essential affiliative and social touch. This can lead to decreased resilience, increased anxiety, and a potential void that individuals might try to fill with other reward-seeking behaviors like addiction.
Yes, due to the brain's plasticity, it is possible to re-prime the touch system at any stage. Children who experienced early neglect, like those from Romanian orphanages, showed stabilization and normalization of behavior when placed in loving, caring foster families, though some long-term consequences may persist.
Similar to touch, there are two types of pain: fast pain (pricking, immediate, protective) mediated by myelinated nerves, and slow pain (emotional, burning, longer-lasting) mediated by C-fibers. The emotional quality of pain is linked to the same C-fiber system that mediates emotional touch.
8 Actionable Insights
1. Nurture Child Brain Development
Provide close, deep, affectionate physical contact to infants and children, as it is a fundamental biological necessity for optimal brain development, social brain functioning, and resilience to stress later in life. A lack of such nurturing touch in early years can lead to severe behavioral and psychological problems and cognitive deficits.
2. Embrace More Human Touch
Actively increase regular, safe, and non-threatening physical touch with friends, family, and partners, giving it more priority in your life. This counteracts societal touch aversion and fulfills a primal human need for deep, meaningful connection, which is crucial for overall health and well-being.
3. Utilize Optimal Stroking Speed
When providing gentle, affectionate touch, aim for a stroking speed of approximately three to five centimeters per second. This specific velocity optimally stimulates the C-tactile afferent nerve fibers, making the touch most pleasant and effective for emotional regulation.
4. Re-engage Touch System
If you or someone you know experienced a lack of touch in early life, understand that the brain’s plasticity allows for the re-priming of the touch system at any stage through loving and caring interactions. This can help stabilize and normalize behavior, even if there are long-term consequences.
5. Resist Touch Aversion
Have the confidence to use your instinctive recognition that appropriate touch is valuable and meaningful, and don’t be scared by the societal ’touch police’ mentality. Collectively demonstrate that touch should be embedded in normal human behavior, not seen as inherently risky or contentious.
6. Limit News for Calm
Reduce your consumption of 24-hour news cycles, as constant exposure to magnified problems can lead to increased stress and anxiety. Watching less news can contribute to a calmer and happier state.
7. Read “The Stress Solution”
For a deeper understanding and practical strategies to increase human touch in your life, read “The Stress Solution” by Dr. Rangan Chatterjee. The book simplifies research and offers take-home strategies, including a chapter on touch informed by Professor McGlone’s work.
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Support the podcast by leaving a review on your listening platform, taking a screenshot to share on social media, or simply telling friends and family about the show. Your support helps spread the word and makes a difference.
6 Key Quotes
Touch is not just a sentimental human indulgence. It's a biological necessity.
Professor Francis McGlone
The worst thing you can do to a child from our research is not touch it.
Professor Francis McGlone
This isn't some hippie hugger hoodie type of thing that Cameron was going on about. This is a fundamental necessity in that developing brain to have close physical contact with the carer.
Professor Francis McGlone
We're touching technology a lot. We're touching our... We're touching these screens a lot, but we're not... I know, it's perverse. On a digital sense, we're more connected than ever before, but in terms of deep, meaningful human connection, have we ever been this isolated?
Dr. Rangan Chatterjee
We need to get this story out there.
Professor Francis McGlone
Knowledge is power.
Professor Francis McGlone