The world of senses: sensory stimulation and its disorders
Each of us gains knowledge through the senses. The first bits of information already reach us in our mother’s womb because we hear her heartbeat and the muffled sounds coming from the outside world, and the skin is surrounded with amniotic fluid, which provides tactile sensations. After birth, a newborn gains new sensor experience – this process then continues throughout our whole life.
Sensory Integration (SI) is a way of analysing sensual stimuli that can be received inside and outside of the body. For most people, perceiving comes automatically and effortlessly. We can distinguish basic senses: touch, smell, taste, sight and hearing, but there are more than just those five. There is also the vestibular sense which, thanks to the inner ear, gives us information about gravity and motion. The proprioceptive sense is based on the sensations coming from muscles and joints, informing us about our body’s position in space, and the interoceptive sense is focused on changes in pulse, body temperature, breathing, hunger and thirst, and sensations coming from the insides, e.g. bladder or intestines. All systems complement each other and cooperate to grant us the most accurate picture of reality, which helps us with reacting appropriately to given situations.
As we get older, we develop further and thus react better to sensory messages. Children quickly learn proper behaviours and how to differentiate between safe and dangerous situations. A perfect example is the sound of a vacuum cleaner that usually frightens them. But as time goes on, a child notices that – despite the loud noise – the vacuum cleaner is not dangerous and will not harm him. The life of a child is composed of constant testing of the sensory systems by trying out new activities and experiencing sight, smell, touch, taste and hearing sensations. Teenagers explore sensory stimulation and discover their comfort zones by checking the boundaries between pleasant and unpleasant sensory sensations. Sensory systems are very diverse and – depending on the person – they can react differently to the same stimuli. Some people love theme parks and fast roller coasters, whereas others feel sick at the very thought of such a ride. Our likes and dislikes are often tied to our personality, so we might say that sensory sensations influence our entire lives.
Each experience is multisensory, meaning each everyday activity affects all the senses simultaneously. Most people handle the stimulation of all sensory systems quite well, but if someone struggles with sensory integration, they might experience excessive stimulation and thereby feel overwhelmed by the amount of stimuli. Sensory stimulation threshold – that is, the threshold of sensitivity to specific stimuli, e.g. loud noises, bright and strong light, an unknown consistency, and intense flavour – is of huge importance when it comes to proper functioning. The stimulation threshold is tied to temperamental features, same as physical and motion activity levels, biological frequency, adaptability, mood, distraction and its scope.
Unfortunately, not everyone’s process of perceiving sensory stimuli is automated. Studies based on parents’ opinions suggest that 5-13% of preschool children have symptoms typical of SI disorders, and it has been proven that 16,5% of school-age children experience hypersensitivity to stimuli, which impacts their everyday life (Ben-Sasson, 2009). Sensory Integration disorders cause the senses to stop being compatible, which makes the data reaching the brain become distorted, and therefore it is difficult to receive a precise and accurate view of the world. People with unbalanced sensory stimulation might struggle with analysing everyday events and adjusting to certain situations. When the differences in sensory perception cause changes in the everyday life and the functioning of a child, it is worth getting a diagnosis for Sensory Integration disorders. Sometimes SI disorders involve unusual preferences and limitations, as well as pain and a mix-up of senses.
Sensory Integration disorders are a totality of three main classifications. The first one is Sensory Modulation Disorder, related to the process of neural transmission of stimuli. People with Sensory Modulation Disorder are characterised by inadequately reacting to a stimulus; their reactions are disproportionate, undesirable, or there is no reaction at all. Depending on the person’s reaction, we may distinguish hypersensitivity – that is excessive reacting, hyposensitivity – insufficient reacting, and mixed sensitivity.
Hypersensitivity is when a child complains about an overwhelming intensity of certain states. A perfect example is children who find many things to be too bright, too loud, or too uncomfortable. Their nerve system’s reaction threshold is very low, and therefore they react to weaker stimuli. A person with hypersensitivity may feel overwhelmed and uncomfortable much more often, as well as react with escape in the case of overstimulation. When that happens, their organism shuts one of the sensory channels off and prevents them from processing information, which distorts perception and may lead to dangerous situations.
People with hyposensitivity require stronger and more frequent stimuli for their body to react. Because of that, such people may seem sleepy and slow, and it is hard to make them be focused. Additionally, children might want to receive increasingly stronger stimuli and as a result, get into a state of excessive arousal.
Mixed sensitivity is when someone has strong reactions to one type of stimuli, but weak or no reactions at all to another type. A good example would be a child who experiences discomfort while wearing many types of fabric but enjoys playing and getting dirty in squidgy and sticky slush. In the case of mixed sensitivity, changes might also depend on the day – sometimes a child might love the taste of strawberries, only to wince and protest at the very sight of them another time. Inconsistency in a child’s reaction is typical of mixed sensitivity.
Next in the classification is Sensory-based Motor Disorder. People with this condition may have difficulties with movement and body posture, which should fulfil specific motor tasks. Other symptoms include imbalance, low muscle tone, low resilience, and problems with motor planning – decisions related to consecutive tasks that, in result, lead to doing specific activities. People with this type of disorder struggle with learning new motor activities such as riding a bike or running, but they might also perform worse when it comes to fine motor skills, e.g. using scissors or stringing beads. Additionally, this disorder affects the tongue and oral functions, so it is much more difficult for a child to learn how to speak and control their oral cavity and tongue while eating.
The last in the classification is Sensory Discrimination Disorder that manifests itself through having difficulties with perceiving the importance of sensory stimuli and differentiating their sources. For example, someone might not be able to identify objects through touch, or someone may struggle with determining the place and intensity of tactile stimulation on their body. Children with that type of disorder can be unaware of something physically disturbing them or that they are leaning against something.
We should keep in mind that SI disorders might reveal themselves differently, depending on the person. As time goes on, issues with sensory stimulation can deepen, but they might also fade – especially if proper treatment is applied. It is crucial to allow people with SI disorders to function as properly as possible, starting from the youngest ages. The most important thing is that children utilise their capabilities, so maybe sometimes it would be worth it to get rid of or at least minimise the stimulus that causes frustration and constant discomfort which decrease the quality of a child’s life.
Biel, L. (2015). Integracja sensoryczna. Skuteczne strategie w terapii dzieci i nastolatków. Kraków: Wydawnictwo UJ.
Stock Kranowitz, C. (2012). Nie-zgrane dziecko. Zaburzenia przetwarzania sensorycznego – diagnoza i postępowanie. Gdańsk: Harmonia Universalis
Image source: https://crello.com/
Author : Ewa Gizińska/ translated by Konrad