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What is the Tactile System?
“Tactile” refers to touch and the skin is the tactile system’s sensory receptor. The tactile system system enables us to point to where we have been touched (with vision occluded) and determine whether we were touched in one, two or more spots. Tactile discrimination tells us whether objects are cold, sharp, wet or scratchy. Primitive animals respond to touch mainly as a warning system. But as higher animals evolved the tactile system become more detailed enabling people to discriminate many types of sensory stimulation to the skin and use that information during fine-motor tasks.
Humans use two types of tactile systems. The defensive or protective system responds to light touch and lets an animal run away from danger or tells a child to swat a mosquito. The discriminative system enables the child to determine whether the touch involved light or deep pressure and how to perceive attributes of objects such as shape, size or texture.
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Sensory Integration and the Tactile System
The tactile system plays an important role in the brain’s organization of sensory information. After all, the skin is the largest sensory organ and the first sensory system to develop in the womb.Tactile along with vestibular (i.e. movement) and propioception (deep pressure) stimulation promotes good sensory integration. The brain tells the child with good sensory integration that grasping objects feels good and sensations from the skin tell her where her body begins and where it ends. Children who have poor sensory integration will often have poor tactile discrimination and appear clumsy.
Babies benefit from the firm touch provided by being wrapped up in a blanket and/or held tightly. Children in orphanages or other institutions who have not received enough early holding and touch may develop what is called “tactile defensiveness.” These children may find ordinary touch such as a pat on the shoulder to be frightening or irritating. Children with disabilities such as autism seem to have difficulties processing sensory information- from birth and also find touch aversive. Common behaviors that may indicate tactile defensiveness include:
- Excessive crying and sensitivities
- Avoids being barefoot on grass
- Hates wearing clothes
- Avoids certain textures, including foods
- Prefers lots of clothing to avoid skin exposure
- Hates haircuts, trimming nails, kisses
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Children with Autism and Dysfunction in Sensory Integration
Children with autism disorders often have difficulty with both the protective and discriminative tactile systems. they struggle to interpret touch and are often picky in what they will eat or touch and this impacts the development of oral motor and fine-motor skills. Occupational therapy treatment and a sensory diet center around providing deep touch experiences such as
- Rolling up inside a blanket
- Manipulating clay and squeeze toys
- Crawling through a cloth tunnel
- Crashing into pillows and other soft objects
As the child develops a tolerance for deep pressure tactile stimulation he may begin expanding the repertoire of textures and objects he will touch and manipulate-leading to the development of tactile discrimination and fine-motor skills.