We tend to have a narrow view of our senses. Very early in our education we are taught about the five senses (there are more!) and how these help us take in the world around us.
For many of us, simplistic environmental perception remains how we think about our sensory system. The more we learn about senses, however, the more inadequate this explanation becomes. Because our senses do far more than just help us to perceive; our nervous and sensory system may be the essence of who we are…
Or in the words of a documentary series Human: The World Within (Nseries, Netflix 2021) Episode 1, React “…but there is one system that controls all the others, and it might be the one that truly makes you, you…the nervous system.” The nervous system receives information from our senses and processes it in the brain. Sensory processing (and sensory processing impairments) play a major role in the way we live our lives, how we react to everything and everyone around us, and ultimately the kind of person we become due to all our sensory experiences.
When considering the enormous influence of sensory processing, a condition like sensory modulation disorder should receive the attention it deserves. Writing off sensory impairments as fussiness or being too sensitive is one of the reasons so many people (especially children) suffer in silence.
This may be even more relevant for those with both autism and sensory modulation disorder—the communication difficulty associated with autism makes it challenging for children to express their discomfort concerning the amount and nature of sensory stimuli in their environment.
Sensory modulation disorder defined
Modulation according to Merriam-Webster.com is concerned with regulating according to measure or proportion. Those with sensory impairments struggle with regulation, and their reaction to sensory stimuli is often not in proportion to the measure of sensory input or stimuli received.
Discussing sensory modulation Miller, Reisman, McIntosh & Simon (2001) explain that: “…the capacity to regulate and organize the degree, intensity and nature of responses to sensory input in a graded and adaptive manner. This allows the individual to achieve and maintain an optimal range of performance and to adapt to challenges in daily life.”
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A paper aiming to clarify the concept of sensory modulation for application by occupational therapists examined the evolution of the term (Brown et la., 2018). A contemporary definition of sensory modulation was summarized by the authors: “Sensory modulation is considered a twofold process. It originates in the central nervous system as the neurological ability to regulate and process sensory stimuli; this subsequently offers the individual an opportunity to respond behaviourally to the stimulus.”
Looking at these explanations we see a picture of sensory modulation disorder emerging; one where an individual may have difficulty not only with regulating, but also organizing appropriate responses to sensory input. Their (behavioral) response may be too intense or alternatively an under-reactive response may be displayed. Furthermore, adapting to the stimuli may also be problematic for those with sensory modulation difficulties.
Is there a difference between sensory modulation disorder and sensory processing disorder?
To many, the term sensory modulation disorder may not be as familiar as the more frequently used sensory processing disorder (SPD). Sensory modulation disorder (SMD) is actually a subtype of SPD. This condition manifests as a type of sensory processing impairment where an individual has difficulty regulating hs/her responses to sensory input.
This subtype (SMD) can be divided into three further categories, according to response to stimuli displayed by the individual:
1. Sensory over-responsiveness
This is characterized by an overreaction or a really intense reaction to stimuli which others may find neutral or tolerable. For children on the spectrum this can be seen in their reaction to tags on clothing, or texture of food
2. Sensory under-responsiveness
In contrast, individuals may also under-react or take a long time before responding to stimuli compared to their peers. For example, children with this condition may display muted responses (or behavior) and appear lethargic and withdrawn
3. Craving sensory input
Seeking sensory input is a way to get feedback from the environment, but this condition can be distinguished from sensory under-responsiveness by observing disorganization—the more sensory input the person craves and obtains the more disorganized he/she becomes. For children on the spectrum this behavior can manifest in compulsive spinning. Sensory seeking behavior is sometimes also observed in children with attention deficit hyperactivity disorder, seeking input through vigorous movement in class may often get them in trouble
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Not everyone agrees with the various terms used to describe sensory processing and integration conditions. These terms are used according to preference and how and where the therapist was trained. Sometimes SMD is referred to as sensory reactivity. Despite all the differing terminology, most experts agree that sensory modulation deficits negatively influence children’s ability to match their response (or corresponding behavior) to the degree and nature of sensory stimuli in their environment.
Children with autism and sensory modulation disorder
Many researchers have mused about the precise impact of sensory processing impairments on symptoms and severity of autism spectrum disorder (ASD). For example if a child is highly sensitive to auditory and tactile input, to a degree where most people and social situations are avoided, what will the impact be on language learning? Without opportunities to observe and participate in a variety of social communication scenarios, the child’s language abilities may develop differently. Whether language learning deficits are aggravated by autism symptoms, SMD or other circumstances is of course debatable.
What we do know is almost every child on the spectrum has some sort of sensory processing difficulty or difference. What would happen if these sensory differences were taken into account to restructure learning and social environments? Would a child with SMD, more particularly sensory over-responsiveness, learn and communicate better in an environment where sensory input is muted to his/her preference? How would a different, more suitable environment affect learning and development?
Sensory issues acknowledged by the DSM-5
Atypical responses to sensory input is a criterion for an autism diagnosis that was added to the latest edition of The Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM–5; American Psychiatric Association, 2013). The DSM-5 defines sensory issues as a feature of restricted or repetitive behavioral symptoms, stating: “hyper or hypo reactivity to sensory input or unusual interest in sensory aspects of the environment.”
This addition to autism diagnostic criteria may be the reason some therapists refer to SMD as sensory reactivity as mentioned above. There is clearly a link between autism spectrum disorder and SMD, with many kids on the spectrum displaying over- or under-reactivity to sensory stimuli. Sensory seeking behavior is also frequently displayed by children on the spectrum and children with ADHD.
The effect of SMD on an autistic child’s daily life
Autism affects communication, social interaction and daily living. Sensory modulation or how we react to sensory stimuli may influence all these factors too.
A study (Schaaf et al. 2010) provides preliminary evidence that children with severe SMD may have different physiological activity (compared to children without SMD) and that the behavioral way in which SMD manifests may influence a child’s ability to engage in social, communication and daily living situations.
Both conditions may negatively affect a child’s life. Parents with children on the spectrum often advocate for studies to show how addressing sensory difficulties may influence severity of symptoms associated with autism. Parents also share that changing or fixing the world to make it a “softer” sensory environment would mean society can stop with their attempts to fix autistic children—in the right circumstances many on the spectrum would thrive.
An inside perspective
Research and clinical studies may educate us about the biological factors involved in sensory modulation, but how do children feel when their bodies over (or under) react to sensory stimuli that their peers seem almost oblivious to?
Parents often share stories of the daily pain—physical and emotional—experienced by their children on the spectrum, whose brains were not wired to process the overwhelming world they live in. I realized the extent of the effect of sensory processing difficulties when speaking to an autism advocate Katrina Hayes from SpeakUp during a session for the upcoming Autism Parenting Summit (September, 2021).
She shared her story of taking her autistic son for his Covid shot. Advocating to the medical staff to make her son comfortable, extensive preparation with visuals before the appointment, and sensory toys brought along for comfort—her son’s aversion to needles still proved too much. Trying to be strong while sharing details about the ordeal, it was obvious that parents and their children on the spectrum face mountains most of us bypass with oblivion.
While getting a shot may be a little uncomfortable for most older children, the sensation and all the surrounding sensory stimuli of going to the doctor may be too much for many kids on the spectrum. Interestingly, research also suggests abnormal pain perceptions in children and adults with SMD (Bar-Shalita et al., 2019).
Talking to adults on the spectrum allows us a glimpse into the overwhelming and sometimes painful reality of sensory over-reactivity. I asked YouTuber and influencer Daniel Morgan Jones (The Aspie World) about sensory overload. Daniel was diagnosed with asperger’s at 26, and shares content on his various platforms focusing on understanding and learning about autism.
He tried to make the feelings of those on the spectrum more accessible by comparing it to trying to read a book, giving everything to try and focus but someone tries to pull the book out of your hands. Simultaneously, he continued, another person is screaming in your left ear and yet another is blasting music in your right ear. The overwhelm is palpable from his vivid description—imagine a child trying to react appropriately to the environment with a sensory system that won’t cooperate.
Sensory modulation strategies
Acknowledging that your child may face daily challenges because their nervous system is processing sensory stimuli differently is only the beginning. You may need the help of an occupational therapist to address your child’s unique sensory processing challenges. If your child is ready to participate in these strategies, you can ask them to help identify their optimum level of arousal.
If they need total silence to concentrate and focus, noise cancelling headphones may help. You may feel your child’s bedroom is quiet, but the ticking clock downstairs (or next door!) may well be distracting enough to render concentration impossible for someone with sensory over-responsiveness to auditory input.
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If the arousal level is too low, on the other hand, your child may appear lethargic. Sometimes crunchy snacks or fidget toys are needed to provide enough sensory stimulation or input for your child to participate. Your occupational therapist will evaluate your child and formulate strategies to address the particular sensory needs of your child.
Living with sensory processing difficulties unfortunately means many of our children are simply withdrawing from a world they find bewildering. Add sensory processing differences to an autism spectrum disorder and bewildering may be too mild a term. Fortunately an occupational or physical therapist trained in sensory integration therapy may be able to help children with strategies to not only cope but hopefully thrive.
American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders (5th ed.). https://doi.org/10.1176/appi.books.9780890425596
Bar-Shalita, T., Granovsky, Y., Parush, S., & Weissman-Fogel, I. (2019). Sensory Modulation Disorder (SMD) and Pain: A New Perspective. Frontiers in integrative neuroscience, 13, 27. https://doi.org/10.3389/fnint.2019.00027
Brown, Anahita & Tse, Tamara & Fortune, Tracy. (2018). Defining sensory modulation: A review of the concept and a contemporary definition for application by occupational therapists. Scandinavian Journal of Occupational Therapy. 26. 10.1080/11038128.2018.1509370.
Merriam-Webster. (n.d.). Modulation. In Merriam-Webster.com dictionary. Retrieved July 22, 2021, from https://www.merriam-webster.com/dictionary/modulation
Miller, L. J., Reisman, J., McIntosh, D. N., & Simon, J. (2001). An ecological model of sensory modulation. In S. Smith- Roley, E. Imperatore-Blanche, & R. C. Schaaf (Eds.), The nature of sensory integration with diverse populations (pp. 57–88). San Antonio, TX: The Psychological Corporation.
Schaaf, R. C., Benevides, T., Blanche, E. I., Brett-Green, B. A., Burke, J. P., Cohn, E. S., Koomar, J., Lane, S. J., Miller, L. J., May-Benson, T. A., Parham, D., Reynolds, S., & Schoen, S. A. (2010). Parasympathetic functions in children with sensory processing disorder. Frontiers in integrative neuroscience, 4, 4. https://doi.org/10.3389/fnint.2010.00004
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