Children and adults with autism, as well as those with other developmental disabilities, may
have a dysfunctional sensory system. Sometimes one or more senses are either over- or under-reactive to stimulation. Such
sensory problems may be the underlying reason for such behaviors as rocking, spinning, and hand flapping. Although the receptors
for the senses are located in the peripheral nervous system (which includes everything but the brain and spinal cord), it
is believed that the problem stems from neurological dysfunction in the central nervous system--the brain. As described by
individuals with autism, sensory integration techniques, such as pressure-touch can facilitate attention and awareness, and
reduce overall arousal. Temple Grandin, in her descriptive book, Emergence: Labeled Autistic relates the distress and relief
of her sensory experiences.
Sensory integration is an innate neurobiological process and refers to the integration and
interpretation of sensory stimulation from the environment by the brain. In contrast, sensory integrative dysfunction is a
disorder in which sensory input is not integrated or organized appropriately in the brain and may produce varying degrees
of problems in development, information processing, and behavior. A general theory of sensory integration and treatment has
been developed by Dr. A. Jean Ayres, Occupational therapist, from studies in the neurosciences and those pertaining to physical
development and neuromuscular function.
Sensory integration focuses primarily on three basic senses--tactile, vestibular,
and proprioceptive. Their interconnections start forming before birth and continue to develop as the person matures and interacts
with his/her environment. The three senses are not only interconnected but are also connected with other systems in the brain.
Although these three sensory systems are less familiar than vision and audition, they are critical to our basic survival.
The inter-relationship among these three senses is complex. Basically, they allow us to experience, interpret, and respond
to different stimuli in our environment
Tactile System: The tactile system includes nerves under the skin's surface that send information to the brain. This information
includes light touch, pain, temperature, and pressure. These play an important role in perceiving the environment as well
as protective reactions for survival.
Dysfunction in the tactile system can be seen in withdrawing when being touched,
refusing to eat certain 'textured' foods and/or to wear certain types of clothing, complaining about having one's hair or
face washed, avoiding getting one's hands dirty (i.e., glue, sand, mud, finger-paint), and using one's finger tips rather
than whole hands to manipulate objects. A dysfunctional tactile system may lead to a misperception of touch and/or pain (hyper-
or hypo sensitive) and may lead to self-imposed isolation, general irritability, distractibility, and hyperactivity.
Tactile defensiveness is a condition in which an individual is extremely sensitive to light touch. Theoretically, when
the tactile system is immature and working improperly, abnormal neural signals are sent to the cortex in the brain, which
can interfere with other brain processes. This, in turn, causes the brain to be overly stimulated and may lead to excessive
brain activity, which can neither be turned off nor organized. This type of over-stimulation in the brain can make it difficult
for an individual to organize one's behavior and concentrate and may lead to a negative emotional response to touch sensations.
Vestibular System: The vestibular system refers to structures within the inner ear (the semi-circular canals) that
detect movement and changes in the position of the head. For example, the vestibular system tells you when your head is upright
or tilted (even with your eyes closed). Dysfunction within this system may manifest itself in two different ways. Some children
may be hypersensitive to vestibular stimulation and have fearful reactions to ordinary movement activities (e.g., swings,
slides, ramps, inclines). They may also have trouble learning to climb or descend stairs or hills; and they may be apprehensive
walking or crawling on uneven or unstable surfaces. As a result, they seem fearful in space. In general, these children appear
clumsy. On the other extreme, the child may actively seek very intense sensory experiences such as excessive body whirling,
jumping, and/or spinning. This type of child demonstrates signs of a hypo-reactive vestibular system; that is, they are trying
continuously to stimulate their vestibular systems.
Proprioceptive System: The proprioceptive system refers to components
of muscles, joints, and tendons that provide a person with a subconscious awareness of body position. When proprioception
is functioning efficiently, an individual's body position is automatically adjusted in different situations; for example,
the proprioceptive system is responsible for providing the body with the necessary signals to allow us to sit properly in
a chair and to step off a curb smoothly. It also allows us to manipulate objects using fine motor movements, such as writing
with a pencil, using a spoon to drink soup, and buttoning one's shirt. Some common signs of proprioceptive dysfunction are
clumsiness, a tendency to fall, a lack of awareness of body position in space, odd body posturing, minimal crawling when young,
difficulty manipulating small objects (buttons, snaps), eating in a sloppy manner, and resistance to new motor movement activities.
Another dimension of proprioception is praxis or motor planning. This is the ability to plan and execute different motor tasks.
In order for this system to work properly, it must rely on obtaining accurate information from the sensory systems and then
organizing and interpreting this information efficiently and effectively.
Implications: In general, dysfunction
within these three systems manifests itself in many ways. A child may be over- or under-responsive to sensory input; activity
level may be either unusually high or unusually low; a child may be in constant motion or fatigue easily. In addition, some
children may fluctuate between these extremes. Gross and/or fine motor coordination problems are also common when these three
systems are dysfunctional and may result in speech/language delays and in academic under-achievement. Behaviorally, the child
may become impulsive, easily distractible, and show a general lack of planning. Some children may also have difficulty adjusting
to new situations and may react with frustration, aggression, or withdrawal.
Evaluation and treatment of basic sensory
integrative processes is performed by occupational therapists. The therapist's general goals are: (1) to provide the child
with sensory information which helps organize the central nervous system, (2) to assist the child in inhibiting and/or modulating
sensory information, and (3) to assist the child in processing a more organized response to sensory stimuli.