All day, every day, we receive information from our senses-touch, hearing, sight, taste, smell, body position, and movement and balance. Our brains must organize this information so that we can successfully function in all aspects of daily life-at home, at school, at play, at work, and during social interactions.
The tactile system provides information about the shape, size, and texture of objects. This information helps us to understand our surroundings, manipulate objects, and use tools proficiently. When you put your hand in your pocket and select a quarter from an assortment of change, you are using tactile discrimination.
We use our auditory system to identify the quality and directionality of sound. Our auditory sense tells us to turn our heads and look when we hear cars approaching. It also helps us to understand speech.
Our visual system interprets what we see. It is critical to recognizing shapes, colors, letters, words, and numbers. It is also important in reading body language and other non-verbal cues during social interactions. Vision guides our movements, and we continually monitor our actions with our eyes in order to move safely and effectively.
Taste and Smell
The gustatory and olfactory systems are closely linked. They allow us to enjoy tastes and smells of foods and cause us to react negatively to unpleasant or dangerous sensations.
Proprioception, or information from the muscles and joints, contributes to the understanding of body position. This system also tells us how much force is needed for a particular task, such as picking up a heavy object, throwing a ball, or using a tool correctly.
Movement and Balance
Located in the inner ear, the vestibular system is the foundation for the development of balance reactions. It provides information about the position and movement of the head in relation to gravity and, therefore, about the speed and direction of movement. The vestibular system is also closely related to postural control. For example, when the brain receives a signal that the body is falling to the side, it, in turn, sends signals that activate muscle groups to maintain balance.
Integrating Information from the Senses
Considering all of the sensory modalities involved, it is truly amazing that one brain can organize all of the information flooding in simultaneously and respond to the demands of the environment. The complex nature of this interaction is illustrated in the following example:
Michael receives the instruction “Please put on your coat.” In order to comply, he must focus his attention on the speaker and hear what that person says:
- Screen out incoming information about other things going on around him
- See the coat and adequately make a plan for how to begin
- See the armholes and sense muscle and joint positions in order to put his arms into the openings
- Feel, with touch awareness, that the coat is on his body correctly
- Use motor planning, touch awareness, and fine motor skills to zip or button the coat
In order to accomplish this seemingly simple task, the nervous system must integrate (focus, screen, sort, and respond to) sensory information from many different sources. Imagine the amount of sensory integration needed to ride a bicycle, participate in a soccer game, or pay attention in an active classroom. Individuals who have difficulties with all or part of this process face significant challenges when engaging in daily functional activities.
Sensory Integration Dysfunction
Individuals with sensory integration dysfunction are not able to effectively process information from their senses and, therefore, have difficulties with tasks such as putting on their coat. Imagine yourself in a world where something as basic as the pull of gravity or the touch of other people is perceived as unreliable, inconsistent, or threatening. You would not feel secure and safe, you might not be able to have fun, and your self-esteem might be compromised as you realized that you were not able to do things as well as your peers.
Sensory integration dysfunction can result in delays in motor skills and problems with self-regulation, attention, and behavior that can affect performance in school, at home, with peers, and during leisure and work activities.
How Do I Know if an Individual Has Sensory Integration Dysfunction?
An individual may need to be referred for an occupational therapy evaluation if difficulties are seen in several of these areas or if one area causes major functional problems.
- Was unusually fussy, difficult to console, or easily startled as an infant
- Has difficulty regulating sleep/wake cycle—settling for sleep, staying asleep, and waking without irritability
- Is over-sensitive to stimulation—over-reacts to touch, taste, sounds, or odors
- Strongly dislikes baths, haircuts, or nail cutting
- Uses an inappropriate amount of force when handling objects, coloring, writing, or interacting with siblings or pets
- Has poor muscle tone, fatigues easily, leans on people, or slumps in a chair
- Was slow to roll over, creep, sit, stand, or walk, or to achieve other motor milestones
- Is clumsy, falls frequently, bumps into furniture or people, and has trouble judging position of body in relation to surrounding space
- Has difficulty learning new motor tasks; experiences frustration when attempting to follow instructions or sequence steps for an activity
- Avoids playground activities, physical education class, and/or sports
- Does not enjoy age-appropriate motor activities such as jumping, swinging, climbing, drawing, cutting, assembling puzzles, or writing
- Finds it difficult to make friends with peers; prefers to play with adults or younger children