Sensory Processing Disorder and Children with Autism: Understanding the Problem

Abstract
The influx of students with autism spectrum disorders over the past twenty years is a major concern for educators, researchers, and policymakers. The prevalence of autism spectrum disorders has been calculated as high as 1 out of every 166 children born annually (Centers for Disease Control, 2006; Steuernagel, 2005). While the direct causes of autism are unknown at this time, researchers are able to define the effects of autism on children's behavior. However, dysfunctional sensory perceptions have been excluded from the diagnostic criteria for students with autism - but included for students with Pervasive Developmental Delay, Not Otherwise Specified (PDD-NOS) (Talay-Ongan & Wood, 2000). Common symptoms of Sensory Processing Disorder (SPD) include lack of balance; apraxia (problems in motor planning); clumsiness; a tendency to fall; odd body posturing; difficulty manipulating small objects (buttons, snaps); and resistance to new motor movement activities (Hatch-Rasmussen, 1995). This paper explores the following questions: What is sensory integration (SI)? What symptoms define sensory processing disorder (SPD)? How does sensory integration therapy (SIT) help the student overcome these challenges? Why should educators embrace and implement sensory techniques?

Introduction
As a special educator and a parent of two children with autism spectrum disorder, I am intensely interested in the effectiveness of the proposed therapies for children with autism. When my wife came home and told me that the occupational therapist (OTR) wanted us to perform "joint compressions and brushing every two hours" on our youngest son, my response was essentially, "That's the craziest thing I have ever heard." After overcoming my initial objections, I quickly became a believer when I observed the dramatic changes in our son's behavior and in his ability to adapt to various situations.
Our search for a cause...and a cure

Although there has been quite a debate about the validity of the mercury-autism linkage, our research into David's diagnosis of autism did not find any injections he received that contained thermiosol (the mercury-based preservative commonly included in multiple-use vaccine batches). We believed that David's case was either genetic or neuro-pathological in nature. Because we could not associate David's case with a vaccination, we did not find any consolation or hope in the chemical chelation treatment protocols (chemicals designed to remove heavy metals and toxins from the body) that were suggested for children with autism (Green, et al., 2006). David's limited diet choices (peanut butter crackers and chicken nuggets) made it impossible to remove gluten (wheat products) and casein (milk products, such as whey) from his diet completely - another suggested course of therapeutic treatment. We observed that David was lactose intolerant, so we were able to restrict his consumption of "raw" dairy products, such as butter, milk, and ice cream.

The focus of this paper
After all our efforts to follow treatment protocols to help our son, the only course of treatment that has offered demonstrably positive effects was sensory integration therapy (SIT), combined with speech therapy and discrete trials therapy based on applied behavioral analysis techniques. Therefore, this paper is designed both to share the hope that SIT has offered to us and to provide research and answers to the following questions which educators and parents of children with autism will want answered. What is sensory integration (SI)? What symptoms define sensory processing disorder (SPD)? How does sensory integration therapy (SIT) help the student overcome these challenges? Why should educators embrace and implement sensory techniques? Readers should gain a clear understanding of the challenges faced by students with SPD and a knowledge base that will help the reader implement sensory-friendly activities in the classroom and in the clinic.

What is sensation?
The human body is designed to function through the processing of sensory data. Humans have several sub-systems that allow us observe and interact with our environment. These sensory systems alert our brain to potential dangers in our surroundings, as well as providing us with the sensations of pleasure, pain, heat and cold, texture and pressure, body orientation, and body position. The overall process of accumulating and sorting out all of the sense-data we receive is known as sensory integration (SI).

As defined by Ayres (1972), SI is "the neurological process that organizes sensation from one's own body and from the environment and makes it possible to use the body effectively within the environment" (p. 11). The therapeutic systems that have arisen from this theory are known as sensory integration therapy (SIT). Ayres (1979) defines the goal of SIT to be improvement on "the way the brain processes and organizes sensations" (p. 184). However, as Jones, Quigney, and Huws (2003) caution, "The underlying principles of SI are not intended to explain neuromotor deficits associated with such problems as CP [cerebral palsy], Down syndrome, or stroke." And Mauer adds, "The underlying assumptions are that: (a) the brain operates holistically; (b) there is an interdependent relationship among the sensory systems, in terms of both development and function; and (c) portions of the brain interact with other portions for individuals to function (Ayres, 1972b; Fisher & Murray, 1991)" (Mauer, 1995).

What constitutes a Sensory Disorder?
When the body's sensory systems are dysfunctional or damaged, our brain is unable to process sensory data correctly. "It should be underlined that a disruption of one domain of development...is likely to affect many other domains, each being an interrelated part of the whole" (Talay-Ongan & Wood, 2000). In The Out of Sync Child (2005), Kranowitz writes, "Touch aids vision, vision aids balance, balance aids body awareness, body awareness aids movement, and movement aids learning" (45). The brain may interpret a cigarette burn as a pleasant experience, or possibly not even register the event at all (hyposensitivity). On the other extreme, the brain may interpret the lightest touch as if it were a red-hot poker touching the skin (hypersensitivity). The dysfunction of sensory integration was first described by Ayres (1969) as "perceptual-motor dysfunction." In recent years, the terms "sensory integration dysfunction" and "sensory integration disorder" have been used in research literature and in popular media to refer to what is now classified as sensory processing disorder, or SPD. The description of SPD details a full range of symptoms, and uses vocabulary that is more user-friendly to the general public. Mauer (1995) gives a general medical diagnostic description: "To diagnose sensory integrative dysfunction (SPD), there must be evidence of central processing deficits involving vestibular, proprioceptive, or tactile sensory inputs." According to Kahmi (2004), "Behaviors associated with SID (Sensory Integration Disorder, or SPD) include hyperactivity, hypoactivity, poor fine-motor coordination, trouble learning to read and to do math, speech and language problems, short attention span, irritability, academic problems, social problems, emotional problems, and self-regulation problems."

In terms of medical diagnosis, the student with SPD suffers from a neurological deficit in the proprioceptive, vestibular, or tactile centers of the brain. "These aberrant sensory reactions are thought to reflect poor sensory integration and/or arousal modulation in the central nervous system." (Baranek, 2002) The symptoms and the description of the deficit indicate that while the necessary nerve receptor cells are present in the student's body, the brain is unable to process the sense-data correctly. A failure to process sense-data correctly influences how the student reacts to the environment. In general, these students are classified as either hyposensitive (very high threshold for sensation) or hypersensitive (very low threshold for sensation). Students with SPD may also have sensory defensiveness, a type of sensory modulation problem. Wilbarger and Wilbarger (1991) defined this as "'a constellation of symptoms related to aversive or defensive reactions to non-noxious stimuli across one or more sensory systems' (Wilbarger & Wilbarger, 2002a, p. 335). It can affect changes in the state of alertness, emotional tone, and stress (Wilbarger & Wilbarger, 2002a)" (DiMatties, 2004)

Students with SPD may also display a fascination with the sensory features of objects, distortions in perception, and paradoxical reactions to sensory stimuli. The prevalence rates of unusual sensory responses vary from 42 to 88% of students with autism (Baranek, 2002; Talay-Ongan & Wood, 2000). Auditory processing problems are also noted, with a 1997 study reporting that 100% of the subjects with autism demonstrated auditory processing difficulty (Baranek, 2002). "Tribe (1992)...claimed that 'there is enough evidence to suggest that sensory processing impairment is as central to autism as the impairments of social interaction, communication, and imagination' (p. 141) (Talay-Ongan & Wood, 2000)."

In their own words...
Autobiographical accounts by Temple Grandin (1996) and other people with autism spectrum disorders relate their daily struggle with a distorted sense of the world around them. "When I got accustomed to pants, I couldn't bear the feeling of bare legs when I wore a skirt. After I became accustomed to wearing shorts in the summer, I couldn't tolerate long pants" (Grandin, 66). "Understanding the paradigm that people perceive the world differently is vital for working successfully with people on the autism spectrum" (Shore, 2004). (For an insider's view of the sensations that students with ASD experience, see Table 1, The Outer Senses.) "O'Neill and Jones (1997) found that individuals with autism report both hypo- and hyper-sensitivity to the stimulation of the senses." (Jones, Quigney, & Huws, 2003) People with autism in the O'Neill and Jones study "were shown to experience discomfort and difficulties due to their unusual sensory experiences and in order to deal with these experiences, a number of coping strategies were employed." (Jones, Quigney, & Huws) One study participant writes, "It's disturbing to see a blot of lint disrupting the perfect plane of a rug bed cover." Another study participant wrote, "A more common problem is talking - the human voice is not painful, but horribly distracting - it ruins my concentration, and can be like Chinese water torture" (Jones, Quigney, & Huws).

Anatomy of the Sensory Systems
To understand the challenges that SPD presents to the individual, we must have at least basic knowledge of human sensory anatomy. The human body has five main senses. These five senses are taste (gustatory), touch (tactile), smell (olfactory), hearing (auditory), and seeing (visual). The "hidden" senses are the interoceptive sense (sensations arising within the body, such as hunger); tactile sense (sensations arising from contact with the environment); haptic sense (the voluntary exploration of the environment through touch) (; proprioceptive sense (sense-data arising from the muscles and joints (Ayres, 1969)); and the vestibular sense (sense-data arising from the inner ear). Working in concert, these senses provide us with the information we need to survive in the world. To limit the scope of this paper, we will focus on the "hidden" senses related to external sensory stimuli - tactile sense, proprioceptive sense, and vestibular sense.

Tactile Sense
Very simply, the tactile sense refers to the body's ability to detect changes in pressure and touch on the surfaces of the skin. The tactile system uses nerve transduction to detect and pass on sense-data to the brain. The process of transduction is similar to squeezing an inflation bulb on a blood pressure cuff; too little pressure will not inflate the cuff. On the other hand, too much pressure will split the bulb in two. When you press an object against your skin, you are literally squeezing the nerve receptors to push the signal towards the brain (Mikulecky, 1999; see Figure 5).

Proprioceptive Sense
Proprioception, in general, refers to the sense of body position in space. Proprioception in medical literature refers to the sensations arising from the muscles, tendons, joints, and the related nerve endings (See Figure 1.) How does this system work? If humans rely solely on visual sense-data to keep us standing upright, how is it that students who are blindfolded are still able to stand up? The proprioceptive sense is responsible for maintaining our awareness of body position and keeps us upright, even when we cannot see our body position.
If you visit the Great Smoky Mountains Railroad (Dillsboro, NC), you can walk through a spiraling tunnel that produces an intense disorientation effect. The reality of the tunnel is that you are walking on a bridge that is level and travels approximately 30 feet from the entrance to the exit. Surrounding the bridge, however, is a rotating pipe that is painted with fluorescent stars, comets, and planets. The tunnel is illuminated by black lights, and the overall effect on the senses is extreme dizziness, vertigo, and disorientation. The illusion leaves the participant with no sense of direction. However, if you close your eyes and walk down the bridge (holding the handrail) you do not suffer the illusory effects. This ability to overcome visual illusion is a primary function of the proprioceptive system.

In students with SPD, proprioceptive errors cause a variety of symptoms, including lack of balance; inability to recognize items (when blindfolded) based on size, shape, and weight; lack of response to a two-point touch on the skin - see Figure 3 (Mikulecky, 1999); apraxia (problems in motor planning); clumsiness; an increased 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 (usually accompanied by tantrums) (Hatch-Rasmussen, 1995). These symptoms are evident across many environments and do not arise from visual stimuli.

Visual-Perceptual Sense
Closely related to proprioception is the visual-perceptual sense. However, a combined visual-perceptual dysfunction creates problems that proprioception alone cannot overcome. Consider a point in space located two feet in front of you, two feet to your right, and three feet above the ground. Expressed mathematically, this point is known as P (2, 2, 3) (where P represents "point", and each number corresponds to a geometric plane (horizontal (X), vertical (Y), and altitude (Z)). To observe this point in two-dimensional space, the point must be drawn as it relates to the X, Y, and Z planes to create the illusion of all three dimensions (See Figure 2). Notice that the point P lies in the Z-axis, not in the X- or Y-axis.

Imagine for a moment that you are playing in the World Series, and the point in space is no longer a point, but a baseball. Due to a visual-perceptual error, you process the location of the ball incorrectly. Your perception of the ball's location is at the point PA (2, 2, 2) (See Figure 2). In this case, you fail to catch the ball and your team loses the World Series. If you had processed the sensory data correctly, you would have caught the ball and saved the game. This is a trivial example; however, it clearly illustrates an important concept regarding SPD. If you cannot evaluate the environment correctly, you cannot respond correctly. In very real terms, SI is an underlying component of personal, social, educational, athletic, and professional success. The student's ability to move body parts in concert to produce the desired effect is impaired by problems in sensory integration.
Baranek (2002) reports that several studies have revealed problems in subjects with autism that reflect overall slower preparation for movement, poor motor planning (resulting from attentional or motivational difficulties), and possibly, a reduced use of externally guided visual feedback. "Thus, perceptually challenging tasks that require smooth integration of visual with vestibular-proprioceptive information...may be difficult to perform and could result in poor quality of motor performance on complex tasks." (Baranek, 2002)

In the realm of education, we measure the student's ability to discriminate the shapes of letters and words; identify the sounds that each phoneme makes; fill in the correct bubble (to indicate the student's processing of these auditory and visual discriminations); and the student's ability to follow directions by placing the answer in the designated area. Have you ever "re-bubbled" an entire test because you skipped a question while taking the test? Perhaps you put your name in the wrong blank on an application form? These mistakes are caused by a visual-perceptual error. If you are unable to correctly process sensory data, then you will constantly make mistakes; this is how we determine that a dysfunction (or disorder) exists. The dysfunction's severity (or impact on learning) is measured by observing the prevalence of errors.

Vestibular Sense
The vestibular sense is responsible for measuring movement of the body. The vestibular system is located within the inner ear structure (see Figure 3). The cochlear labyrinth houses the three semi-circular canals, which are tubes filled with hair cells and nerve endings. Each semi-circular canal is designed to measure a different aspect of movement. The uppermost canal measures the head's roll position - the motion made by trying to lay your head on your shoulder. The middle canal measures the head's pitch, which is the movement you make by touching your chin to your chest or tilting your head backwards. The lowest canal measures the head's yaw, which is the twisting motion made as you turn your head from side to side. The utricle (which measures horizontal forces) and saccule (which measures vertical forces) are known as the otolith organs; they measure the body's acceleration with respect to gravity.

Damage from disease or injury to these sensory organs leads to persistent dizziness, vertigo, nausea and/or vomiting, and fear of movement. A defect in processing the sense-data collected may produce the same type of symptoms; coupled with the lack of communication skills in students with autism, the result may be tantrums or a refusal to move from a preferred body position. Ayres (1962) cites the example of a young girl who refused to move from the seat of the family car, but was quite at home riding on a ferris wheel. "In the ferris wheel, she needed only to sit quietly and let the Ferris wheel take over the job of relating to the earth, but stepping out of the car demanded that she know how to move in order to reach the ground without hurting herself." Hatch-Rasmussen (1995) describes the two extremes as hypersensitive (the child avoids movement, and may appear clumsy) hyporeactive (the child constantly seeks extremes in body movement - spinning, jumping, and body whirling).

Children with vestibular disorders may be unable to describe the sensations they experience, possibly because there are so few connections from the vestibular system to the cerebral cortex (Mehta & Stakiw, 2004). Children who experience vestibular disorders also tend to communicate the sense of disorientation through behavior, such as holding on to stationary objects; anxiety, anger, or fearfulness; and may appear to not understand verbal communication (Mehta & Stakiw). Children with vestibular disorders may also experience academic difficulty; they sometimes require extra help with tasks related to spatial concepts, memorization, and new concepts in general (Mehta & Stakiw, 2004).

What is Sensory Integration Therapy?
As discussed earlier, Ayres (1979) defines the goal of Sensory Integration Therapy to be improvement on "the way the brain processes and organizes sensations" (p. 184). With the goal of improving the symptoms of SPD in mind, the occupational therapist (OT) must first assess what adaptive skills are delayed, what sensations are sought after or avoided by the child, and what treatment options are best suited for the child. Based on this assessment (or series of assessments and interviews), the OT then prescribes a treatment regimen which can include the Wilbarger brushing technique (Wilbarger and Wilbarger, 1991) along with a combination of sensory diet activities and adaptive skills training.

You mean I have to put the child on a diet?
Well, yes - a sensory diet. Just as runners train in various climates and altitudes while preparing for future events, the student with SPD needs to experience a full range of sensations - and learn to interpret, modulate, tolerate, and respond to them appropriately. Kranowitz (2005) describes three types of sensory input involved in a sensory diet: alerting activities (to benefit the underresponsive child), calming activities (to assist the child decrease sensory overload and organizing activities (to benefit the child's regulation of sensory responses) (Kranowitz, 229).

In the case of an average student with SPD, the sensory diet would include specific gross motor activities, such as walking around in weighted garments; lying under weighted blankets; playing in a ball pit, water tub, or sandbox; jumping jacks, push-ups, swinging activities, spinning activities, balance beam and tumbling activities.
In addition to gross motor skills, chewing exercises provide proprioceptive input from the jaw and acts as a calming activity; oral-motor exercises provide a combined tactile/gustatory sense benefit - encouraging the student to try new food items and new textures, including chewing on food items and blowing bubbles. Interaction with vibrating toys, pillows, and chairs have a calming effect; and even fine motor skill activities, such as threading a bead on a string, tying shoelaces, or tracing letters can be used as part of the therapy. (Willis, 2006; Kranowitz, 2005)

Criticism of Sensory Integration Therapy
There are many studies that document the effect of vestibular rehabilitation on patients with vertigo and balance recovery problems (Cohen & Kimball, 2004; Miedaner, Shea, Grove, & Pyle, 2005; Gresham, Beebe-Frankenberger, & MacMillan, 1999). However, most of these studies are focused on an adult population, and there is even among the researchers a seeming misunderstanding of sensory integration therapy. In the case of SPD, however, the specificity of the disorder and the limited population make large-scale studies impractical at best. The lack of such large-scale studies has caused many researchers to question the validity of the theory and the therapy (Dawson & Watling, 2000; Baranek, 2002; Rimland & Edelson, 1995).

Single-subject research is still the prevailing mode of exploration into the effectiveness of sensory integration therapy (SIT). In many cases, the implementation of SIT is in concert with speech therapy and other therapeutic regimens - which begs the question: Which therapy is working? Is progress being made because of the quantity of approaches, the intensity of each, or is it simply the effect of personal contact that is the deciding factor?
The difficulties in designing scientific studies of Sensory Integration Therapy on a large-scale basis are numerous. Within the framework of student outcomes, however, is it ethical to deny a child the possibility that something can help him/her overcome some of the challenges that SPD presents? Multiple studies demonstrate that the more time a student spends in early intervention therapy, the more positive the results and long-term prognosis. Ayres (1969) concedes that scientific evidence for her theory is scant. However, Ayres also defends her work with the fact that many of the perceptual errors described are evidenced in adults with nervous system injuries. The focal shift in American medical research and psycho-educational approaches after World War I forever altered the treatment approaches for people with brain injuries or developmental delays. Doctors realized that soldiers returning home with head injuries displayed the same behaviors as patients in mental institutions - and that there were effective therapies that offered these patients a higher quality of life.

As an occupational therapist, Shelly Richard has first-hand experience with Sensory Integration Therapy (SIT) and SPD. In an interview conducted November 17, 2006, Ms. Richard says that SIT "helps the student process sense-data and then provide an adaptive response - like handwriting and other fine motor skills - or to sit still for 20 minutes of circle time. It is not a magic bullet or a stand-alone therapy; SIT was always intended as a supportive therapy for other programs, such as speech and educational training." Ms. Richard indicates that she has run into her share of resistance to the idea of SIT; the author has encountered fellow educators who refuse to consider the possibility that such a disorder exists. In her personal experience, teachers and doctors who established their credentials more than 15 years ago have the most difficulty accepting and implementing SIT.
Ms. Richard relates that her case observations validate the research that older children derive some benefit from SIT, but younger children show the most progress in terms of their adaptive and fine motor skills. Ms. Richard is concerned that the State of Tennessee does not recognize SPD as a valid disability and neither do most insurance companies. However, the state does recognize the existence of developmental delay in the domain of fine motor skills, so students who have fine motor problems related to SPD are able to receive occupational therapy under that category, and SIT is simply one approach to dealing with the student's problems.

Sensory Integration and Education: Discussion
Baranek (2002) has compiled a comprehensive list of studies that show the efficacy of sensory integration therapy as a supportive therapy in the school. She suggests that schools should develop a "best practices" approach to remedying the various sensory conflicts that exist in schools, such as replacing fluorescent lights, adding soundproofing to echoing hallways, and providing alternates to unbearably loud fire alarms. In addition to these environmental changes, schools can view SIT as part of the foundation for academic success for children who suffer with the disorder.

As the original research into sensory integration was focused on learning disabilities, it is of some interest that autism spectrum disorders, SPD, and ADD/ADHD seem to have some common neurological and behavioral linkages. If a school were to implement sense-friendly remediation of the lighting, for example, it is quite possible that some of the disruptive behaviors that students with ADD/ADHD exhibit might simply fade away. Williams and Shellenberger (1996) formalized the pyramid of learning in sensory integration literature and offer a graphic representation of sensory integration theory and how it relates to the learning process (see Figure 6).

As an educator, I find that the sensory integration theory meshes nicely with both Maslow's and Gardner's Theories of basic human needs. We first learn through sensation; it makes sense that a defect in sense-data processing would affect other systems and interfere with learning on the cognitive level. In the same manner, a student who is hungry is unable to concentrate on studying until that hunger is satisfied. As the student's most basic needs are met, the student feels free to take on new challenges.

A student who is uncomfortable and shifting around in their seat is likely going to disturb another student; it is only practical to provide some help for the student who needs it. Teachers can provide help to all the students in the classroom by making environmental changes (lighting, sounds, and seating) and through implementation of sensory diets (structured programs of varied sensory activities that provide needed stimulation to the child). My favorite activity to use in the classroom is the 2 minute stress break; I allow the students 2 minutes to stretch, jump up and down, or just talk to their friends. After 2 minutes, we return to our work. Using this type of intervention, no student is singled out for "therapy" and students tend to have better instructional focus when they are allowed a break during the class period.

Teachers can also be silent partners with the occupational therapist in making sure that the student with SPD is sent on errands, allowed to have comfort or fidget items (such as "koosh" balls or fuzzy pencils), and is allowed to go to a safe place in the school when the student is overstimulated. The focus of SIT is on younger students in the lower grades; however, the benefits of the interventions prescribed by an occupational therapist can be seen in the classroom at all levels of education.

In teacher training programs at East Tennessee State University, teacher candidates learn about the auditory, visual, and kinesthetic learner. The activities and learning strategies for each of these learning styles are simply an extension of the sensory experience into the cognitive realm. For the teacher, SIT techniques for the child with autism should be analogous to a hearing aid for a child who is hearing impaired. A teacher would not deprive a student who is hearing impaired from the use of his hearing aid; why, then, do teachers dismiss SIT techniques as "nonsense" or "not existent?"

Overall, there is a general lack of knowledge of sensory techniques in the educational setting. While occupational therapists may implement the Wilbarger brushing technique (Wilbarger & Wilbarger, 1991) and other intensive therapies, the classroom teacher is only requested to be aware of the levels of sensory stimuli and make adjustments to the classroom to better accommodate the student with SPD. Teachers need to be aware of the symptoms of overstimulation, such as aggression, anxiety, and self-stimulation, and be prepared to intervene in a positive manner, rather than punishing a student for exhibiting a coping behavior.

Conclusion
To review, sensory integration refers to the body's ability to organize and process sense-data. The successful processing of these stimuli allows the student to interact appropriately in the environment. When sensory integration is unsuccessful, the student will exhibit improper and sometimes bizarre behaviors in an effort to modulate the sensory input and re-order the sensory processing function of the body. Failure to process sensory data correctly is known as SPD.

SIT is an intervention-based protocol that helps the student accept sensory input at a comfortable level and allows them to concentrate on the required task. SIT is not designed to be a cure-all or a stand-alone therapy; it works best in concert with speech therapy and psycho-educational strategies. Teachers, students, parents, and clinicians will benefit from the use of sensory diets and intervention techniques prescribed and supervised by an occupational therapist. If you want to learn more about SPD, the author recommends The Out-of-sync Child (Kranowitz, 2005).

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