Dr. Mary Mollway, Ed.D.
The Underactive Tactile System
At birth, an infant processes 80% of the environment through the sense of touch (tactility). The part of the brain that processes touch is called the somatosensory cortex.When a child is massaged, caressed, or cuddled, the brain is activated in the brain stem, the thalamus (mid-brain), and the sensory cortex. The tactile sense is the first to develop and much of our brain organization is dependent on this early input.
Many of us are familiar with the term “tactile” because we relate it to touch. Maybe your child has been diagnosed with “tactile defensiveness” or “tactile seeking”. However, tactility is about far more than what we feel with our fingers or when something touches us. It is a complex system (see the image below).
There are many different types of receptors in our tactile system. Some are more defensive, like the tactile receptors in our hair follicles. They actually respond to not only sound but vibration as well. Children who can’t stand to have their hair combed most likely have underdeveloped tactile receptors. Other receptors are distinguishing and help us determine whether something is hot or cold, hard or soft, safe or dangerous, etc. These receptors are in the derma of the skin. When defensive receptors are on, the distinguishing ones are off; once a child or person is touched in safety, the defensive receptors shut off and the distinguishing ones turn on.
Challenges can arise when this system is either hypo-active or hyperactive. This week, we are focusing on the hypo-active system. In a hypo-active tactile system, the receptors are not providing the correct input to the brain about touch stimulus. A person may have a very low pain sensitivity but crave physical input. They may have challenges with balance and understanding where they are in space nor can they necessarily control or read the strength of their own touch. Individuals may seek out input through very vigorous physical activity, extreme sports, fighting, constantly touching each other, or horseplay.
Individuals with hypo-active tactile systems may be described as hyperactive, aggressive, and/or clumsy. They simultaneously seek out touch and proprioceptive input and yet cannot judge the force and strength of either the input or their response. They may present as “having no fear” or being “reckless.” An “adrenaline junkie” may, in fact, be trying to constantly feed an underactive tactile system so that his brain gets the input it is craving and feels safe in the world.
This state can also manifest as having very poor interoception, or an inability to notice one’s own body and state of physical well-being. A child may not recognize they are tired until the meltdowns have begun, or may not even notice they’ve wet their pants. A person who forgets to eat because they didn’t notice they were hungry or can’t feel their emotions starting to dysregulate may be dealing with issues in the tactile system.
What causes this? Trauma, including birth trauma, can be one cause. Trauma en utero or at birth may prevent the tactile system from develping fully or from being stimulated in the birth canal. Trauma after birth, even as an adult, dampens our tactile receptors as a protective mechanism so that we cannot feel pain. Other causes can be complications during pregnancy, missing key developmental steps, not having enough movement or cuddling as an infant, and/or genetics.
What to do about it? In traditional therapy, therapists will provide input through activities like brushing, joint compressions, or “heavy work” which all provide proprioceptive input. This can be an effective approach for mild deficits that just need some nudging to mature.
In a developmental approach, the tactile system is turned on through a very specific pattern of movements and touch that educate the system and help it myelinate and thus mature. This approach is much more effective for more immature systems and thus for people experiencing more dysregulation.
You can learn more at www.brain-works.org