What is Sensory Processing?
Sensory processing is our ability to combine and understand information coming in from our senses. Our brain continuously receives information from all of our senses. Our brain then filters through this information in order to decide which information is important to attend to and which isn’t. Sensory processing is an automatic process. The purpose of this process is to enable us to be able to attend, organise and move our bodies and manage our emotions as efficiently as possible. Autism can cause a more varied experience of sensory processing.
Within the DSM-5 criteria for Autism, sensory processing differences known as hypo or hyper sensitivity are categorised under section B “restrictive, repetitive patterns of behaviour”. Whilst this does reference the sensory processing difficulties somewhat in terms of engaging in self-regulatory behaviours/’stimming’ it doesn’t necessarily reflect the impact that sensory processing difficulties can have on an autistic individual’s participation in everyday activities. One of the most commonly reported explanation that autistic individuals give for having difficulty participating in everyday activities, school life or social situations are sensory processing difficulties/sensitivities and difficulty tolerating the sensory aspect of an environment.
It is common for autistic individuals to report difficulty tolerating every day sensations such as smells, background noise, or the sensation of clothes. We think autistic individuals may not have the same ability to filter through and get used to the information the brain is receiving. If this filtering isn’t happening efficiently, the brain can be flooded with sensory information which can make it difficult for the person to attend to other things in the environment (e.g. someone talking to them) and can be overwhelming emotionally too.
What are our senses and what do they control?
Most people will know our five basic senses – vision, hearing, smell, taste and touch. However, there are 3 other less known senses – the vestibular sense, proprioception and interoception. As mentioned in previous pages, it’s best to think of autism in the social model of disability. This means considering how the environment is disabling to an autistic individual. Autistic people may be described as having sensory issues, but sensory differences is more accurate in describing the variety of ways our community processes the environment around us.
Our eyes allow us to see and perceive what is going on around us as well as allowing us to form a sense of distance and depth. Our brain merges the information from both of our eyes to create our visual perception. Our eyes also work closely with the vestibular system which is our balance system to help us know in which direction we are moving and to keep our eyes and head steady, so our brain can make sense of the information more easily. Autistic individuals appear to gather a lot more detail from their environment visually than neurotypical people. In other words autistic individuals tend to notice more detail in their surroundings whereas neurotypical people may filter this information out.
Similarly to our vision, our brain combines the information it receives from both of our ears to perceive the sounds we are hearing. The way our brain processes these sounds allows us to interpret where the sound is coming from. This also contributes to our sense of body awareness, for example, if we hear a sound is becoming louder, we perceive that thing as getting physically closer to us. Our hearing system also filters out unimportant background noise. However, this appears not to be the case for autistic individuals and is one of the most well-known sensory differences they experience. Autistic people can often be very sensitive to sounds, particularly sounds coming from lots of directions like in busy places e.g. shopping centres or schools and lower frequency sounds such as handryers or hairdryers. This can present difficulty with perceiving where a sound is coming from, and an autistic individual may pay attention to all sounds in an environment at once making if difficult to concentrate or respond to someone talking to them or indeed sensory overload in some instances.
Our senses of taste and smell are highly connected. Our senses of taste and smell are important for keeping us safe and play a key role in our dietary and eating habits. Our body naturally dislikes bitter or sour tastes as a way of keeping us safe from eating foods that may not be safe for us to eat. Our bodies are naturally attracted to sweet and salty foods which the body finds comforting. It is common for autistic individuals to be sensitive to the smell, taste and texture of food which often impacts the range of foods they can tolerate.
Our sense of touch provides us with lots of different information. Without using our other senses we can understand where we are being touched, the pressure of the touch, and the temperature of touch. Two pathways deliver these touch messages to our brain to be interpreted, the first (known as the anterolateral system) carries information relating to pain and extreme temperatures and crude touch and the second (known as the dorsal column medial lemniscal pathway) carries information about deep pressure touch/proprioception, vibration and fine touch. We have all had the experience of getting a small cut (such as a paper cut) and applying pressure to it instinctively to stop the discomfort. This is because the 2 pathways intersect in the brain. When we apply pressure to the injured area, the pressure messages reach the brain first and block the brain from receiving any more pain messages.
In autistic individuals who are sensitive to touch, we think that the brain is mis- interpreting every-day touch, like the feel of clothes as uncomfortable or painful. Hence, many interventions to decrease sensitivity involve using deep pressure or proprioception.
Our vestibular sense tells us how and when we are moving. The receptors for the vestibular sense are in our inner ear. Three very small semi-circular tubes filled with fluid allow us to interpret what direction we are moving in and how fast. We can interpret this as the fluid in our vestibular system will move as we do, sending signals to the brain. Our vestibular system is able to perceive tiny movements of the head (that happen all the time-even when sitting still!) and instruct the body to make small adjustments to our muscle tone (the tightness of our muscles) to keep us upright and balanced. This is also important for keeping the head and eyes steady so the brain can interpret the information from the eyes more easily and not feel dizzy.
If the vestibular system is not working efficiently, this can cause difficulties with balance, low muscle tone and tolerating movement. The person might also seek out movement in order to stimulate their vestibular system or indeed have difficulty with balance and often coordination.
The vestibular system is also like a gate keeper or traffic warden for information coming in from the other senses. The vestibular system filters information from the senses as it enters the brain and ‘decides’ which information is passed up the brain so we are aware of it. Again, if the vestibular system is inefficient, the brain can be overwhelmed with sensory information. This is why many programmes or interventions to improve sensory processing involve movement e.g. swings, trampolines etc.
Proprioception is our sense of body awareness. Each time we move our bodies, receptors in our muscles and joints allow us to perceive where our body is even if our eyes are closed. If an individual’s proprioception system isn’t interpreting information from their proprioceptive system efficiently, they may need to use other senses such as vision, movement and touch in order to allow them to have a clear sense of body awareness/where there body is. For example, they may need to bump or touch objects whilst moving around a building, or wrap their legs around the legs of the chair they are sitting on, for example.
Interoception describes our sense of what is going on inside our body. This sense allows us to interpret our heartbeat, our breathing, our emotions, whether we are hungry and when we need to use the bathroom. While we are constantly perceiving what goes on inside of us we are not always alerted to these changes. We often only receive an ‘alert’ when our brain is letting us know that our body needs something or our status has changed, for example, when we get hungry. If an individual struggles with interoception they may not receive these alerts. For example, they may forget to eat as they are not automatically reminded that they need to eat or may not notice that they need the bathroom until it’s too late.
What is Sensory Overload and why is it so common with Autism?
The purpose of our sensory processing is to keep us calm but alert in relation to what is going on in our environment. If individuals are not able to filter through the sensory information in their environment it can be more difficult to remain calm or alert. This build up of sensory information is referred to as sensory overload. This can feel different for different people. An individual experiencing sensory overload may become irritable, anxious, upset or even completely shut down in their attempt to regulate their sensory environment. While sensory overload is not exclusive to Autism, it is experienced more acutely by autistic people.
Our bodies have a number of automatic reactions that occur when faced with a potentially threatening or dangerous situation. These reactions are called our ‘fight or flight’ reaction and are built into our bodies to enable us to escape quickly should that be necessary. Part of this ‘fight or flight’ reaction is that our senses become heightened or more sensitive.
This begins with our ear drums changing shape to allow in lower frequency sounds that we would usually filter out. Our eyes also become more alert and also scan the environment more frequently and rapidly. At a physiological level, our heart might begin to race, and our breathing might become quicker which pumps oxygen to our muscles so we are ready to run. Sometimes however, the ‘threat’ is not a physical one i.e. we are not actually in physical danger, rather we experience a psychological stress such as receiving unexpected bad news, having an exam or test or a falling out with a friend. But the reaction in our body can be the same .
Alongside the emotional upset, we will become more sensitive to sensation. For example, if we are feeling stressed and someone touches us we may jump because we have become more sensitive to sensory input. This in turn can make us more emotionally upset so it can become a cycle of sensory sensitivity and stress. For autistic individuals who tend to be naturally more sensitive to sensory input, minimising other stressors in the environment or routine is as important as sensory calming activities in preventing sensory overload.
What is Self Regulation?
Self-regulation is something that we all do in one way or another. It refers to using activities or behaviours to maintain a calm and alert state to help us manage the changing demands we experience in our environment. If we feel ourselves becoming anxious, irritated or overwhelmed we may take some deep breaths, have a cup of tea, play with a pet, turn to a hobby such art or writing or take a break from the environment. Similarly, if we feel ourselves getting distracted, bored or fidgety, we might stretch or go for a walk if possible, fidget, take a cold drink listen to loud music. All these activities could be considered self regulation strategies as they help us to return to a calm and alert state. Although similar, self-regulation is different to a sensory diet in that it is more intuitive i.e. depends on the person noticing when their body needs more or less sensory input rather than a planned schedule of sensory breaks.
What is Stimming?
Understanding stimming is crucial to encouraging coping strategies related to autism and sensory processing. Self stimulatory behaviours or “stimming” is a type of self-regulatory behaviour which often involves repetitive behaviours, movements or noises. Stimming may involve something like hopping from one foot to the other, repeating a word or phrase, flapping hands or something more subtle like playing with hair. In the past, stimming used to be something that people were trying to stop, mistaking it for ‘fidgeting.’
We now know that stimming is essential for autistic people to be able to do this. Unfortunately, people who are stimming in public can face judgement or stigma. It is important to remember that while this behaviour may seem unusual this behaviour is very important to the individual and serves a purpose for them in relation to regulating their emotions, environment and behaviour. It is important that we normalize stimming in schools, workplaces and public spaces to ensure that autistic people are able to regulate themselves and feel self to do so authentically.
Stimming can happen for a number of reasons. Sometimes it can be a way to express excitement or happiness, but it can also be a sign that the person is feeling overwhelmed and is trying to calm themselves. For example, an autistic person who is experiencing sensory overload may begin stimming to cope with their environment, especially if there is no quiet space available. This means stimming can be a vital mechanism for preventing meltdowns.
