What is Sensory Processing Disorder?

Sensory processing is a concept used to describe the way in which our central nervous system (brain and brain stem) receives sensory input from the environment and the body, organizes it, assigns meaning to it, and initiates a response to it. For the majority of people this is an automatic, subconscious process that we are not aware of performing. How we process sensory information determines how we experience and interpret the world around us.

 “Sensory Processing Disorder” (SPD) refers to the set of symptoms and behaviors that result from inefficient or poorly processed sensory signals. It is a complex disorder of the brain that affects both children and adults.

Dr. A. Jean Ayres, an Occupational Therapist, is credited with developing the theory of SPD, which she originally called “Sensory Integrative Dysfunction.” New terminology has been recently recommended, identifying six subtypes of this dysfunction and using the umbrella term Sensory Processing Disorder to encompass all of them. Many people have a combination of more than subtype.

People with SPD misinterpret everyday sensory information, such as touch, sound, and movement. Some feel bombarded by sensation, while others may be unaware of sensations and may seek out intense sensory experiences. Those with SPD may also show sensory-motor deficits or delays such as weak muscles or a “floppy” body, clumsiness and awkwardness, or delayed motor skill development.

Sensory Over-Responsivity
These individuals are more sensitive to sensory stimulation than most people. Consequently, they often display a "fight or flight" response to sensory input, e.g. to the touch of clothing, or being touched unexpectedly. Sudden or loud noises are also intolerable. This condition is sometimes referred to as being "sensory defensive."

Sensory Under-Responsivity
This describes those who are under-responsive to sensory stimuli, and do not respond to the intensity of stimulus that typical people would respond to. For example, they may be unaware of someone calling their name or when someone enters the room. They may appear withdrawn, difficult to engage, or self absorbed because they do not detect the sensory input in their environment. They may also exhibit poor body awareness, clumsiness or movements with poorly controlled force. They often have a high pain tolerance, and do not react to bumping into things, falling, or scraping their skin.

Sensory Seeking
Individuals with this subtype crave sensory stimulation and seem to have an almost insatiable desire to receive sensory input. They tend to be constantly moving, crashing, bumping, and/or jumping. They often touch everything they see, are overly affectionate, and are not aware of personal space. This subtype is often misdiagnosed as ADHD, which may or may not be a concurrent condition.

Postural Control Disorder
As a result of inefficient sensory processing, many people with SPD have some degree of a postural control disorder. They have difficulty stabilizing their body to sit or stand still, or with coordinated adjustment while moving. They often have low muscle tone and appear “floppy,” and/or have loose joints and excessive flexibility. They fatigued quickly and may often complain that they need to rest. They may use excessive force at times, such as breaking pencils or crayons, or hitting others without intending to.

Dyspraxia/Motor Planning Problems
SPD may result in problems planning and performing new motor actions. They may have difficulty in one or more of the following categories:
a) learning or performing new motor tasks, b) mentally projecting into the future to form a goal or idea, c) planning a sequence of actions. These individuals are often uncoordinated, awkward, and accident prone. They usually have poor gross motor skills for ball games or other sports, and/or trouble with fine motor activities. They may prefer sedentary, mental activities to avoid motor planning challenges, and engage in excessive verbalization or fantasy play.

Sensory Discrimination Disorder
Sensory discrimination is the ability to differentiate between the quality of sensory stimuli, e.g. smooth/sharp, loud/quiet, red/blue. It enables accurate understanding of what is seen, heard, felt, tasted, or smelled. Difficulty determining the characteristics of sensory stimuli results in poor interpretation of the specific qualities of stimuli (Do I see a “p” or a “q”? Do I hear “cat” or “cap”? Do I feel a quarter or a dime in my pocket? Am I falling to the side or backwards?). Individuals with poor sensory discrimination may process information slowly, appear awkward in both gross and fine motor abilities and/or inattentive to people and objects in their environment. They may take extra time to process the important aspects of sensory stimuli.

Traditionally, SPD has been treated by Occupational Therapists who are specifically trained in this sub-specialty area. Occupational Therapy is always concerned with how people function in their daily life tasks and roles. Since one of a child’s most important roles is play, sensory integration therapy takes place in a setting that invites play. During therapy sessions, controlled sensory experiences and stimulation are used to help children learn to manage these experiences and gradually tolerate more difficult challenges.

During each session, the child is guided through activities that challenge his or her ability to respond successfully to the environment. These activities are generally chosen by the child, with the therapist’s guidance, to provide the right mix of tactile, proprioceptive and vestibular sensory input to meet the child’s specific developmental needs. The activities are carefully structured by the therapist, with the difficulty gradually increasing such that the challenge is always at the best level to promote growth and mature responses.

The child's active participation, motivation, and exploration are important aspects of therapy. By allowing them to be actively involved, and explore activities that provide sensory experiences most beneficial to them, children become more mature and efficient at organizing sensory information. This improves functional responses to the daily challenges of life. In addition to clinic treatment, OTs will often suggest home activities, sometimes referred to as a "sensory diet," to reinforce and enhance the effects of treatment.