Sensory processing disorders (SPDs) are classified into three broad patterns:
- Pattern 1: Sensory modulation disorder. The affected person has difficulty in responding to sensory stimuli. They may be over-responsive, under-responsive, or crave stimuli.
- Pattern 2: Sensory-based motor disorder. The affected person has difficulty with balance, motor coordination, and performing skilled, non-habitual, and habitual motor tasks. For example, they may not be aware of how their limbs are positioned.
- Pattern 3: Sensory discrimination disorder (SDD). The affected person may have trouble understanding the stimuli. For example, they may not know how hard they must hold an object in order to avoid breaking it, or find it difficult to figure out which way to turn when walking.
What is a sensory processing disorder?
Sensory processing disorder is a condition affecting the way the brain processes sensory information, or stimuli. The disorder may affect one particular sensation (hearing, smell, taste, touch, or sight) or more than one sensation. In some people, sensory processing disorder may affect all the senses.
Touching, smelling, seeing, hearing, and tasting has an impact on mood and emotions. There is a continuous exchange of information between the senses and the brain, whether that’s feeling the warmth of a loving hug or the joy of eating a favorite meal.
Now, imagine a scenario where someone can’t enjoy or even respond appropriately to such sensations. This may take away the pleasant response soothing sensations as well as the ability to withdraw from a potentially harmful sensation, such as heat, cold, and pain. This is what may happen to a person with a sensory processing disorder.
By affecting the brain’s ability to perceive stimuli, sensory processing disorders may cause the following:
- Makes the person over-sensitive to stimuli. For example, the affected person may find the noise of rustling leaves unbearable, feel that their skin is getting chafed by the light touch of garments, or scream when their face gets wet.
- Makes the person under-sensitive to the stimuli. For example, the affected person may keep spinning without feeling dizzy or may not realize their hand is being burned.
What are the subtypes of sensory processing disorders?
The three patterns of sensory processing disorders may have further subtypes, which are described in the table below.
|Sensory modulation disorder|
|Sensory over-responsive||Predisposed to respond too much, too soon, or for too long to sensory stimuli that most people find tolerable.|
|Sensory under-responsive||Predisposed to be unaware of sensory stimuli, have a delayed response, have a muted response, or respond with less intensity compared to an average person.|
|Sensory craving||Predisposed to obtain sensory stimulation, but getting the stimulation results in disorganization and does not satisfy the craving for more.|
|Sensory-based motor disorder|
|Postural disorder||Difficulty in perceiving body position, as well as poorly developed movement patterns that depend on core stability. This causes weakness and poor endurance.|
|Dyspraxia||Difficulty in thinking, planning, and executing skilled movements, especially novel movement patterns.|
|Sensory discrimination disorder|
|Auditory discrimination disorder||Problem with interpreting stimuli that are heard. For example, the person may not know whether they hear “cap” or “pack”.|
|Visual discrimination disorder||Problem with interpreting stimuli that are seen. For example, the person may have trouble seeing the difference between the written words “was” and “saw”.|
|Tactile discrimination disorder||Problem with interpreting touch. For example, the person may not be able to tell by touch whether a coin is a nickel or a quarter.|
|Vestibular discrimination disorder||Problem with interpreting stimuli coming from the movement of the body through space or against gravity. For example, the person may not be able to tell whether they are turning left or right.|
|Proprioceptive discrimination disorder||Problem with interpreting or determining characteristics of sensory stimuli experienced using the muscles and joints. For example, the person may not know how hard they can squeeze an object without breaking it.|
|Gustatory discrimination disorder||Problem with interpreting or determining taste. For example, the person may not tell the difference between lightly sweet foods and those that are too sweet.|
|Olfactory discrimination disorder||Problem with interpreting or determining smell. For example, the person may not be able to tell if a piece of toast is burning although they may sense that something is wrong with it.|
|Interoception||Problem with interpreting or determining sensory messages from body organs. For example, the person may not feel the sensation of a full bladder or of being too full or hungry.|
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STAR Institute. Subtypes of SPD. https://sensoryhealth.org/basic/subtypes-of-spd