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| | Sensory Integration
by Cindy Hatch-Rasmussen, M.A.,
OTR/L
Therapy Northwest, P.C.
Beaverton, OR 97005
http://www.autism.org/si.html
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 from studies in the
neurosciences and those pertaining to physical development and neuromuscular
function. This theory is presented in this paper.
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. The three sensory systems will be discussed below.
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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.
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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 hyposensitive) and may lead to
self-imposed isolation, general irritability, distractibility, and
hyperactivity.
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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.
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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.
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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.
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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.
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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 and/or physical 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.
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