According to a leading paper on the topic, sensory processing disorders can be categorized into three basic patterns:
- Sensory Modulation Disorder, including sensory over-responsivity, sensory under-responsivity, and sensory seeking/craving.
- Sensory Discrimination Disorder
- Sensory-Based Motor Disorder
My post entitled What is Sensory Processing? defines Sensory Modulation Disorder and Sensory Discrimination Disorder. This is a follow-up post about the third pattern: Sensory-Based Motor Disorder.
Simply put, some motor coordination difficulties are due, at least in part, to faulty sensory processing. There are two sub-types of Sensory-Based Motor Disorder: Postural Disorder and Dyspraxia.
To understand postural disorder, it’s important to first understand postural control. The terms for postural function vary somewhat among professionals and in the literature. Most experts agree, though, that there are two main functions of the postural control system:
- To keep you upright against gravity and help you maintain your balance, for which I prefer the term postural stability. This can be further broken down into static and dynamic functions. Static posture (meaning still, unchanging) is when you are upright against gravity without moving, and dynamic posture (meaning ever-changing) is when you work to keep your balance while moving.
- To keep the rest of your body still so you can use a part of the body to push, pull, reach and/or use force to complete a task. For this function, I like the term postural regulation. To conserve energy, you must be able to stabilize parts of your body and use isolated movements to carry out an action.
Postural control is a lot more complex than just standing and sitting up straight, which is what many equate with “good” posture. In addition to keeping us upright, research has shown postural control actually prepares the body to move, which is referred to as anticipatory or feedforward postural adjustments. Postural control also contributes to your body schema or internal map of where you and all your body parts are in relationship to gravity. This is crucial for maintaining joint and muscle alignment as well as determining your center of gravity. Additionally, reflexive postural reactions help you recover when you are bumped, jostled, or otherwise knocked off balance. And, perhaps most complex of all, motor coordination relies on the combination of posture and movement.
Postural skills are largely subconscious, meaning you probably do not pay much attention to them. However, you rely heavily on your posture to complete every day tasks such as brushing your teeth or typing at a computer. Staying upright against gravity and coordinating your movements actually requires integration of multiple sensory systems. The sensory systems that contribute most to your posture include your: proprioceptive, vestibular, tactile (touch), and visual systems.
So, what qualifies a posture problem as a sensory-based motor disorder? Just like all sensory disorders, a sensory-based posture disorder is caused by brain wiring differences that are either developmental (present from birth) or acquired by a brain injury or disease. Therefore, poor posture due to poor physical fitness or health would not be considered a sensory-based condition.
Symptoms of a postural disorder may include:
- Chronic muscle tension in the neck, shoulders, and back
- Unusually loose or tight muscles at rest
- Poor control of movements (i.e., clumsiness, poor body awareness)
- Core muscle imbalance, resulting in rounded or slouched posture (see Figure 3)
- Slow reflexes/reactions when knocked off balance (for example, you may not be able to catch yourself when tripping or falling)
- Inefficient or excessive/extraneous movements (such as motor overflow) resulting in fatigue
Motor praxis is perhaps even more complex than postural control. In sensory integration theory, the term “praxis” encompasses all of the processes involved in performing skilled movements. Briefly stated, praxis includes:
- Ideation–coming up with ideas; problem-solving; using the imagination to mime actions without objects (for example, “pretending” to brush your teeth)
- Planning–deciding what to do
- Sequencing–coming up with a logical sequence of actions
- Execution–carrying out your plan of action
- Feedback–reflecting on how well a plan of action is working
When a professional is assessing praxis abilities, some of the areas that may be examined are:
- Constructional praxis–building or copying configurations of materials or shapes from a model or instructions
- Oral motor praxis–coordinating the muscles of the mouth and jaw for speech production and facial expressions
- Imitation of movements–watching a demonstration of a complex movement or a series of motions before doing the same movement/motions
- Motor patterns–sustaining repetitive movement patterns (such as a rhythmic clapping pattern)
When praxis is optimal, it has three main functions:
- Completing familiar motor tasks automatically, often using the same pattern of movements without much thought. For example, you may shower or fix breakfast the same way every day without making any decisions about what action to take next. You just “go through the motions.” This automaticity of movements saves a lot of mental energy, which frees up energy for your brain to use on newer, more interesting functions. This process occurs at the base of the brain in the subcortical region.
- Coming up with ideas, making plans, thinking of ways to get organized, and problem-solving for actions you will take in the future. This includes reflecting on recent experiences and processing what you thought went well and what you wish had happened differently. These processes happens in the top and front area of the brain, primarily in the frontal lobe of the cerebral cortex.
- Monitoring your performance in the moment to sustain actions or make adjustments to improve your accuracy or speed. This process combines both of the previously functions as well as additional cortical functions.
When praxis skills are not fully functional, one or more of the above processes are impaired. This impairment is called dyspraxia. The literal definition of dyspraxia is “bad” or “difficult” action. Some people use the term dyspraxia interchangeably with or prefer other terms, such as apraxia (which is literally defined as “without” action), developmental coordination disorder, or motor planning problems. In the United States, occupational therapists commonly use the term dyspraxia as an umbrella term for praxis problems.
Praxis abilities are based on the sensory processing functions of modulation and discrimination of inputs, as well as in the cerebellar functions of sequencing and rhythmicity. Praxis problems can be either developmental in nature (as in developmental coordination disorder), or caused by illness or injury (such as a head injury or stroke). It should be noted that in the United States, rehabilitation professionals tend to prefer the term apraxia for praxis challenges brought on by illness or injury.
Some symptoms of dyspraxia are:
- Poor coordination, especially for complex tasks involving multiple body parts
- Difficulty learning complex motor skills, such as driving a car
- Struggling to come up with ideas or becoming distressed when answering simple open-ended questions, like, “What do you want to eat tonight?”
- Difficulty with multi-tasking
- Having trouble following multi-step instructions
- Always doing things “the hard way” or in an illogical way
- Having trouble planning ahead
- Difficulty managing time
- Poor organization
- Being overly rigid with plans and routines
As you can see, sensory-based motor disorders can be quite complex and affect many different aspects of daily life. Currently, best practice for addressing praxis challenges is to teach clients bottom-up (body and sensory-based) strategies in combination with top-down (cognitive) strategies to manage symptoms and improve quality of life.