Touch - The Primary Brain-Skin Connection
How does the skin communicate with the brain through the sense of touch? Touch involves sensory receptors that decode physical or chemical stimuli into electrical impulses that travel from the outer brain to the inner brain, along the central nervous system, at over 200 miles per hour. These receptors can identify changes in pressure, pain, heat and cold. They are located in every part of the skin, with the hands, face, and mouth having the most. The tongue has more than 9,000 sensory receptors, which is why babies first learn to explore their world with their tongues.
The brain has evolved two distinct but parallel pathways that process touch. The first is the sensory pathway, linking the skin to the primary somatosensory cortex. This is the region of the brain that decodes touch. The sensory pathway is also involved in creating memories from tactile experiences, which explains how touch not only conveys, but activates deep-seated emotions. Touch can be a powerful contributor to emotional well-being, and a lack of touch adds to the social isolation that goes hand-in-hand with epidemic depression. Each touch can play an important role in the development of self-esteem, or unfortunately with abuse, create a painful memory.
Why are certain touches experienced differently depending on the person or context of the interaction? For instance, a hug from your spouse or partner hopefully lights you up more than a hug from a casual acquaintance.
The second pathway that connects the brain with the skin is hormonal and is referred to as the neuroendocrine pathway. This brain pathway signals the brain to release oxytocin, the love hormone, and is associated with social bonding and sexual pleasure. It also is the mechanism that creates the feedback loop of stress-related skin conditions like acne, atopic dermatitis, psoriasis, melasma (brown spots) and alopecia (hair loss), which is first triggered through the mast cells in the skin.
As we age, the skin loses its ability to decode touch. Every year following adulthood, we lose one percent of our tactile sense as the density of nerve endings in the hands and feet decrease: the nerves die off and don’t come back. The insulating material in the brain, called myelin, also coats nerve fibers in the skin, and as we age myelin naturally breaks down, and the information that transfers from the skin to the brain along the two pathways moves more slowly. This is one of the reasons that the elderly are prone to falling: their brain is getting less information from the soles of their feet. A loss of touch perception also affects the elderly in other ways, especially those who are in bed for sustained periods of time. Because their brain does not receive the message of touch, it doesn’t prompt them to move or turn in their beds, creating injuries and subsequent infections, including pressure ulcers.
Stimulation to the skin, through touch, enhances neurogenesis, the proliferation of new brain cells and neuronal connections throughout life. A 1986 study noted that massaged preterm infants gained 47% more weight than non-massaged infants, were more socially responsive, and were discharged 6 days earlier from the hospital. Yet I have unfortunately witnessed the deleterious effects of poor parenting, with infants showing failure to thrive and other debilitating problems due to a lack of parental touch. I recall the story of one 4-month-old boy that I examined who had been abandoned by his parents. He was finally adopted by his grandparents, who doted on him through their gentle touch. When I saw him just a few weeks later he seemed to have gained a much greater sense of mental stability.
Some of the most powerful stories ever told about touch deprivation are included in the 2014 book Romania's Abandoned Children by Nelson, Fox and Zeanah. The book explores the implications of early experiences for children's brain development, behavior, and psychological functioning in the realm of the 1989 fall of Romania's Ceausescu regime “that left approximately 170,000 children in 700 overcrowded, impoverished institutions across Romania, and prompted the most comprehensive study to date on the effects of institutionalization on children's wellbeing.” The book details the devastating toll paid by children who are deprived of responsive care, social interaction, stimulation, and psychological comfort.
Launched in 2000, the Bucharest Early Intervention Project (BEIP) included a rigorously controlled investigation of foster care as an alternative to institutionalization. As noted, “Researchers included 136 abandoned infants and toddlers in the study and randomly assigned half of them to foster care created specifically for the project. The other half stayed in Romanian institutions, where conditions remained substandard. Over a twelve-year span, both groups were assessed for physical growth, cognitive functioning, brain development, and social behavior. Data from a third group of children raised by their birth families were collected for comparison. The study found that the institutionalized children were severely impaired in IQ and manifested a variety of social and emotional disorders, as well as changes in brain development. However, the earlier an institutionalized child was placed into foster care, the better the recovery.”
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For more information, look at my YouTube series on the Brain-Skin Connections:
