Disturbances in our early motor and sensory development can impact us in many different ways
This is a huge field of study, that unfortunately little is known about even amongst many experienced teachers and practitioners. This article looks at our sensory development, and explores the concept of sensory integration.
Our senses are the medium through which we perceive the world. What we perceive is dependent on the relay of information from specialised receptors within the major sensory systems of the body to the central nervous system (CNS).
It is within the CNS that the information is then processed, interpreted and if necessary acted upon. Whilst everyone is familiar with the five direct senses of vision, hearing, touch, taste and smell, there are two other indirect sensory systems that are less well known. These are the vestibular and the proprioceptive systems. Whilst we are consciously aware of the direct senses, most of the time the work of the indirect senses goes on beneath our conscious awareness. It is primarily through these seven sensory systems that we are able to make sense of our experience, as well as the world we live in.
In order to operate at maximum efficiency, each of these systems need to work together in an integrated and co-ordinated way. This is known as sensory integration. Sensory integration provides a neurological foundation for the smooth development of complex motor skills, learning and behaviour.
Each of the senses begin their development in utero, with the vestibular system being the first to form and the only one that is fully myelinated at birth. Throughout the prenatal period, each of the sensory systems is particularly vulnerable, and can easily be damaged as a result of excessive stress, illness or a number of other factors that can occur during pregnancy.
During birth, each one of our senses is stimulated and activated to a high degree. The different forces experienced during the birth process can also damage the sense organs and their neurological connections. As the baby is born, he can all too easily experience sensory overwhelm due to his arrival into a world that is brightly lit, noisy and disorienting in comparison to his experience in the womb.
After birth, issues such as glue ear and repeated ear infections, the side-effects of vaccinations, as well as significant illnesses especially in infancy and early childhood can all lead to the development of sensory problems. Head injuries e.g. when playing sports and strokes can also be causative factors, as can the effects of stress and emotional issues.
Sensory dysfunctions can range from mild to severe. Unbeknownst to us, most people actually have a mild to moderate level of sensory dysfunction, and yet are able to adapt to it in order to function fairly well in life. Severe problems, however, are usually associated with some form of learning disability, behavioural problems, co-ordination problems and/or emotional difficulties. The term sensory integration disorder (or sensory processing disorder) is often used to describe those individuals at this end of the spectrum. Sometimes, problems are apparent immediately in terms of developmental issues. In other cases, problems may not present until extra demands are placed on the system as a result of schooling and/or physical activities. It is estimated that as many as 30% of school-aged children have some form of learning disability, and that the majority of these will have some form of sensory dysfunction.
Hypo- and Hyper-Sensitivity
Whilst the causes of sensory dysfunction lie in some aspect of our earliest experiences, their effects are to somehow damage and/or distort the normal function of our sense organs, sensory nerves and the sensory processing centres in the brain. As a result of this, any of our senses can end up receiving either too much or too little information.
Where a sense is under-responsive and experiences sensations less intensely than normal, it is referred to as hypo-sensitivity. A sense that is over-responsive and experiences sensations more intensely than normal is referred to as hyper-sensitivity. In many cases, a single sense can be both hyper- and hypo-sensitive, which creates a great deal of sensory stress and confusion. As well as this, there is a seemingly limitless combination of possibilities that can occur as a result of different sensitivities in each one of the senses. For example, someone can be hypo-sensitive to sound, hyper-sensitive to visual stimuli and both hypo- and hyper-sensitive to touch.
To add further complication, the degree to which we might be either hyper- or hypo-sensitive can vary throughout a day. For example, when we are stressed, tired or hungry, we may not be as tolerant of noise and visual stimuli as we would be if we were completely relaxed and at ease.
Hypo-sensitivity – a child who is hypo-sensitive to sound might have some form of hearing deficit, making it difficult for them to accurately hear and follow instructions at school. As a result they may get bored quickly, become fidgety and easily distracted. In many cases, they could eventually receive a diagnosis of ADD/ADHD. Hypo-sensitive children tend to over-compensate for this lack of sensory information reaching the brain. This could occur in a number of different ways. For example:
- Through constant movement (vestibular/proprioceptive),
- Talking loudly, shouting and needing the television turned up (auditory),
- Being overly physical, pushy, craving touch (tactile)
- Needing bright lights and constant visual stimuli (visual)
Hyper-sensitivity - in order to cope with the onslaught of sensory information, it is common to find one of two different ways in which individuals react to this situation. The first is to avoid or withdraw away from the source of agitation. Individuals who have this strategy have a tendency to isolate themselves, preferring to work or play alone, and also preferring quiet activities to more boisterous ones. The second way of reacting is through explosive, aggressive and/or violent behaviour as the sensory stimulus pushes the individual’s autonomic nervous system into a state of sympathetic overwhelm.
Examples of hyper-sensitivity include:
- Irritated by clothing e.g. labels, waistbands, collars, seams. Finds touch and closeness to others bothersome and annoying. Tactile defensive. (tactile),
- Easily gets sick/dizzy during playground activities and when travelling in cars, trains etc. (vestibular)
- Irritated, distracted and even overwhelmed by noise e.g. playgrounds, classrooms, shopping centres (auditory)
- Cannot tolerate bright lights, patterns and excessive visual stimulation (visual)
So, maybe see if you can become aware of any possible hyper- or hypo-sensitivities in one or more of your sensory systems (clue – visual and auditory are genrally the easiest ones to become aware of, whilst vestibular and proprioceptive are more challenging).
Next time, I’ll look at an aspect of our early motor development and explore ways in which this can effect us in later life. Until then, be well.