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Sensory Integration 101

What is Sensory Integration? Sensory Processing? Sensory Modulation? A Sensory Diet?
What is the difference between Sensory Integration Disorder and Sensory Processing Disorder?
Sensory Modulation Dysfunction? Dysfunction of Sensory Integration? Somatosensory Dysfunction?
Threshold to Response? Tactile Defensiveness? Gravitational Insecurity? Dyspraxia? Somatodyspraxia?

First, let me say that I don't think it's appropriate or necessary to throw most of these terms around when working in schools as an OT. If you have a strong background in this area, that's great and you probably understand all of these terms better than I do. But school-based scope of practice very rarely requires this level of conversation. See more of my rambling about this here. This whole page is just here as an attempt to clarify some of the concepts we may be using in applying SI theory to our school practice.

These terms and others are used to mean different things by people in various locations or professions, and the meanings have changed over time so that they will also varied depending on when and with whom a professional was trained. Some aspects of sensory integration are based on medical and research-based facts, while others are theories which have yet to be proved or disproved. All of this can make it very confusing when someone is telling you that your child has a disorder you've never heard of and that swinging is going to help her! Is it a load of hooey? Is it medically sound?

To gain some perspective, let's start with a history of sensory integration. Within the occupational therapy world, sensory integration was born in the research and practice of A. Jean Ayres, an OT with advanced training in neuroscience and educational psychology. She was interested in the relationship between deficits in interpreting sensation from the body and environment with learning and motor difficulties. She popularized the term sensory integration, meaning,
"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." (Sensory Integration and Learning Disorders, 1972)

Jean Ayres continued to develop and change her ideas and practice relating to sensory integration up until her death in 1988. She developed the Sensory Integration and Praxis Tests as a means to assess the components of sensory integration and guide treatment. She developed theories about typical patterns of disability based on factor analyses from her testing and from observations of children. From these theories she developed methods of treatment for specific patterns of disability using "enhanced sensory experiences." Over time, the therapy itself became known as sensory integration. Therefore, the term sensory integration now refers to three things:

1. The neurological process as described in the quote above,
2. The theory regarding the integration of sensation and how it relates to motor and learning difficulties, and
3. The assessment and therapy guided by sensory integration theory used to address suspected deficits in the sensory integration process.

Got all that? That's only the beginning of the confusion, because after Jean Ayres, people who had worked with her, people who had worked with those people, and others continued to add their own theories and ideas to the mix. Advances in neurological science and educational research have also helped sensory integration theory develop. But as often happens, different groups of people working on research and ideas in any given area came up with a bunch of different terms. The American Occupational Therapy Association (AOTA) and Sensory Integration International - aka The Ayres Clinic ---(this organization shut down after lots of splits in the profession over what is and isn't SI, side-taking, financial problems etc. Here's a link to a news article on the final messy demise if you're interested)--- both made attempts at standardizing the terminology used when discussing SI theory.  They cleared up some terms and made suggestions on others. Still, it is confusing and other organizations continue to coin and use their own terms. In part, that is because these disorders are not diagnoses, such as would be made by a medical doctor or psychologist. They aren't diagnoses in the DSM-V or ICD-10 (though sensory problems are listed as part of the criteria for an Autism diagnosis).  They are currently terms primarily used by occupational therapists, parents, and some educational specialists and psychologists. I haven't sat in on any professional boards on this, but as best I can tell, here is a glossary of general SI terms you may hear bandied about:

Aversion or Aversive Response
a negative reaction to a sensory input, such as withdrawing from the input or protesting it. A more intense aversive response would be going into "fight, fright, flight" mode.

Aversion/Intolerance to Movement
similar to gravitational insecurity, but more specifically characterized by autonomic nervous system response (nausea, heart rate, sweating, that sort of thing) to movement that most people would consider non-noxious; thought to be the result of poor processing of vestibular input.

a condition in which the ability to plan unfamiliar motor tasks is impaired (see Motor Planning). Considered a developmental condition, since motor planning is a developmental skill. Speech therapists often refer to the same concept, as regards to articulation and oral motor, as Apraxia.

Gravitational Insecurity
thought to result from poor sensory modulation of vestibular (gravitational and movement) and proprioceptive input; manifested as fear of being out of upright position, having feet off of the ground, and/or fast movements through space. Responses to this input are out of proportion to any actual danger and also to any postural deficits the individual may have.

Heavy Work
this is activity that provides proprioceptive input through stretch receptors in active muscles and joints that are bearing a load. It is often a term used in sensory diets. It is, ideally, movements with large muscle groups (hamstrings, shoulder girdle, pecs, abdominals, etc) against resistance and is symmetrical and sustained. Think pushing a heavy box across the floor. Pedalling a bike up a steep hill. Playing tug-o-war. Holding yourself up on a chin-up bar. Even (in a less intense way) chewing on gum or squeezing a stress ball. For a link to many many such activities, click here.

Motor Planning
The process of taking in sensory information about one's environment as well as one's own place in space, movement, force, and so on in order to successfully imagine and complete a motoric task. For more, click here

See motor planning. The terms dyspraxia and apraxia come from this word, and both mean difficulty with praxis. In my experience, speech therapists tend to use apraxia and OTs and PTs use dyspraxia.

from the Greek, meaning sense of self. The sensations derived from movement from sensors in muscles that are triggered by stretch and by contraction of the muscles, the deeper part of our skin, and a little bit from joint position that tell us where we are in space and how we are moving. See Heavy Work. Also, the term Kinesthesia is sometimes used interchangeably with Proprioception, but not usually by OTs. It tends to be used more in psychology, dance, and other fields. It puts more of an emphasis on movement and less on position-in-space.

Sensory Defensiveness
thought to result from poor sensory modulation of sensory input in any or all of the categories; strong aversive response to sensory input that most people would consider non-noxious. (Includes Tactile Defensiveness, below, and Gravitational Insecurity, above)

Sensory Diet
this refers to a set of sensory strategies for a particular child that are put together into a daily program or schedule. The term "diet" is used to stress that our bodies require minimal amounts of sensory input to thrive, just as they require food and drink.  Usually, an occupational therapist will work with the child's care-giving and/or educational and/or therapeutic team to find useful strategies and determine how often, for how many minutes, and how intensely the strategies are usually needed. These are then formalized into a daily sensory diet.
For a list of sensory strategies for home & school, click here.

Sensory Integrative Dysfunction (sometimes called Sensory Integrative Disorder or Disorder of Sensory Integration - DSI)
difficulty with central nervous system (brain, mostly) processing sensation, especially vestibular, tactile, or proprioceptive, which result in poor praxis, poor modulation, or both. See Sensory Processing Disorder, below.

Sensory Integrative-based Therapy
a program of intervention involving meaningful therapeutic activities that include enhanced sensation--especially tactile, vestibular, and proprioceptive--active participation, and adaptive interaction. Translation: the child is engaged in an activity that is meaningful to her that works on developing needed skills while the therapist sets up or guides the activity so that the child will be getting stronger or different sensory input that usual. That extra sensory input triggers reflexes and other neuromuscular connections that are meant to facilitate successful completion of the difficult motor skill. Example: a girl with poor balance and motor planning, suspected to be due to reduced awareness of body-in-space. In one therapy activity, she wears a weighted vest (enhancing proprioceptive input) while straddling a bolster swing (working on balance) and pulling a rope to make herself swing (working on motor planning while also providing herself extra vestibular input). The muscle work of pulling the rope also provides proprioceptive input.

Sensory Modulation
the ability to regulate and organize reactions to sensory input in a graded manner (jumping when you hear a loud bang, but not when the air conditioner cycles on). The balancing of excitatory and inhibitory inputs, and adapting to environmental changes (not jumping at every bang when your office is next to a large construction job).

Sensory Modulation Dysfunction
a pattern of dysfunction where a person under- or over-responds to sensory input from the body or environment. There are four types: gravitational insecurity, sensory defensiveness, aversive response to movement, and under-responsiveness.

Sensory Processing
this includes the responses of sensory receptor cells (such as touch receptors in the skin or light receptors in the back of the eyes), but more importantly it includes the process that takes place within the brain. It is making sense of the sensory input our brain receives from the rest of our body. There is a "clearinghouse" stage, where our brain decides what is worth paying any attention to at all and passes it on to the specific areas for processing sound, sight, touch, temperature, gravitational awareness, etc. Sensory processing includes  reception, modulation, integration, and organization of sensory stimuli. Some people also use this term to mean the behavioral responses to sensory input (aversion or attraction, for example).

Sensory Processing Disorder
O.K. this is a bit confusing. The terms sensory integration disorder or dysfunction of sensory integration are often heard (and abbreviated DSI to distinguish it from sudden infant death syndrome - SIDS).  Various specialists in the field of SI decided that it was time for a term that differentiated the theorized disorders involving sensory processing from the neurological use, the theory of, and the term for treatment, "sensory integration." So they came up with this term. It is an umbrella term covering all types of dysfunctions in processing sensory input. Here is a chart which may or may not clarify it for you.
One goal of the profession is to get some official diagnosis included in the DSM and the ICD at some point.

Sensory Registration
Noticing sensory stimuli in the environment; "tuning in" to a particular stimuli.

a relatively severe form of sensory-integrative-based dyspraxia (poor motor planning) characterized by difficulty with both easy and more difficult motor tasks; thought to be based in poor processing of tactile and likely vestibular and proprioceptive sensations. No musculoskeletal or neurological disabilities are present (spinal cord injury or muscular sclerosis with muscle wasting, for example).

Somatosensory Dysfunction
I believe this refers to the suspected poor processing leading to somatodyspraxia, above.

Tactile Defensiveness
The state of exhibiting an aversive response to tactile input, or types of tactile input (most often light touch), that most people would find non-noxious

Threshold to Response
this term is sometimes used to mean the same thing as sensory registration. However, it has been discouraged since threshold is typically a neurologically-used term when referring to the actual response of a single nerve to an input, or the amount of signaling that a muscle cell requires before firing.

sensation derived from stimulation to the vestibular mechanism in the inner ear (liquid-filled tubes, hair cells) from movement and positioning of the head; contributes to posture and the maintenance of a stable visual field.

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