The Sensory Processing System
We all know that there are five main senses – visual, auditory, olfactory (smell), gustatory (taste), and tactile (touch), but we also have senses that are a bit less heard of that are known as somatic sensations or “internal” senses. These are proprioception (awareness of muscle movement) and kinaesthesia (sensation of motion) which work together, vestibular (balance/positioning of body), and interoception (interior senses such as hunger, thirst and the need to pee). Each of these senses send signals to our brains to be processed and our brain, in turn, sends out a response. In a neurotypical person, these messages that the brain receives are processed appropriately and given a typical response. In people with sensory disabilities, the messages received from incoming stimuli are scrambled and the body reacts in uncommon ways.
It has been said that our eyes are our “window to the world”. “We perceive shapes, distance, movement, colour, heat and depth by our sense of sight” (1). Our ability to see affects our balance, our hand-eye coordination and our depth perception. Without sight, we lose the awareness we need to navigate our world. If we are unable to process the information our eyes give us to orient ourselves in our environment, basic mobility can become extremely difficult as will other abilities such as reading, eating and bathing. When the information our eyes receive becomes jumbled, our brain is not able to discern properly what we are seeing, and, in turn, our body reacts incongruously. Sight can be affected by ailments including glaucoma, blindness, colour-blindness and many other eye-related problems.
Our ears are what take in the sounds around us. This is known as our auditory sense. “Auditory processing is a term used to describe what happens when your brain recognizes and interprets the sounds…” (2)
Once the brain evaluates the auditory input, it sends messages to the rest of the body to react to the sound. A loud bang might make you jump, or a person saying “Hello” elicits the return “Hello. How are you?” Have you ever been accused of having “selective hearing”? “It occurs when we unconsciously block out sounds while interacting with a stimulus that we have deliberately chosen to focus on…” (3). Hearing what is going on around us and being able to decipher what is important and what is not is helpful in determining if we are safe, unsafe, in a fun environment, a loud environment, even a quiet place. If our brains are unable to interpret the noises around us, we may not be able to act appropriately in a given situation, such as in a library, where we need to be quiet, and our brains are picking up every minute sound and magnifying it, we may become loud and disruptive in reaction.
Our noses are the organ that transmits smells to our brain. “The olfactory system is responsible for our sense of smell… involves the detection and identification of molecules in the air. …nerve signals are sent to the brain where the signals are processed” (4). “Olfactory information travels not only to the limbic system – primitive brain structures that govern emotions, behaviour, and memory storage – but also to the brain’s cortex, …where conscious thought occurs. In addition, it combines with taste information in the brain to create the sensation of flavour” (5). Knowing that the sense of smell is transferred to the same area of the brain that oversees emotion and memory explains why certain smells can bring back memories. But imagine if you couldn’t differentiate a good smell from a bad smell. If the area of your brain that translates your sense of smell is not functioning properly, you wouldn’t be able to tell that the smell of lilacs and magnolias is as sweet smelling as honey is tasting.
Speaking of taste, the gustatory system is next. “Taste is the sensation produced when a substance in the mouth reacts chemically with taste receptor cells located on taste buds in the oral cavity, mostly on the tongue” (6).
There are five basic tastes that our gustatory system differentiates. These are sweetness, sourness, saltiness, bitterness, and umami. The brain can distinguish between something that is good for you to eat versus something that may be poisonous by using these different tastes. Sweet generally indicates something good to eat whereas bitter tastes signify danger and an avoidance of the taste. The sense of taste and the sense of smell combine to translate unique flavours to your brain. This is why when you have a cold and your nose is stuffed up, some foods have no taste or are extremely bland.
The tactile sense, or sense of touch is relayed through the skin on your body. You can feel touch on every square inch of your body, making it the largest inputting sense we have. “The sense of touch is formed by a large number of… simple receptors… The receptors sense pressure on the skin, and that is how you can feel touch. … Without a sense of touch, you would have no physical self-awareness” (7). These receptors perceive touch, pain, pressure, temperature and vibration. Your brain deciphers all these types of touch and tells your body how to react to each. If you are hugged, you hug back; if you accidentally brush by a prickly shrub, you cry out in pain from a scratch from a thorn. If your nerves are misfiring or you have nerve damage, sensitivity can be diminished and cause delays or complete lack of responsiveness to anything coming in contact with your skin. The inability to sense touch could potentially be dangerous if you are unaware of your surroundings.
Two senses that are a bit hard to differentiate are proprioception and kinaesthesia. They somewhat relate to each other which is why I am grouping them together here. “Kinaesthetic awareness and proprioception work as partners to get us through the movements of our lives… Muscle memory is a kinaesthetic concept. So many things that we do without thinking — such as walking, …— is a kinaesthetic experience based on proprioception” (8). “…the difference between proprioception and kinaesthesia is that proprioception is the sense of the position of parts of the body, relative to other neighbouring parts of the body while kinaesthesia is sensation or perception of motion” (9). Proprioception refers messages to our central nervous system to control our movements whereas kinaesthesia is our awareness of how we move.
The vestibular system is in the inner ear and gives us our sense of balance. It also informs the brain if our body is upright or upside down. “The vestibular sense is important for development of balance, coordination, eye control, …being secure with movement…” (10). “It automatically coordinates the movement of one’s eyes, head and body. It helps maintain muscle tone, coordination of the two sides of the body and holding the head upright against gravity” (11). If your eyes are not able to track the path you are taking, your coordination is off or if you have vertigo, it is possible that there is an issue with your vestibular system.
The last, and least well-known sense is the interoception system. “Any sensations that originate from within the body, like the feeling of hunger and thirst, sickness, heart rate, and the feeling that one needs to use the bathroom all stem from the sense of interoception” (12). You can tell when you are hungry or if your heart is racing. These are interoception receptors telling your brain how your body feels. These receptors also let you know if your body is hot, cold, feeling pain or being tickled. People that suffer from sensory issues may not be able to tell if their bladder is full because their body isn’t translating the message to their brain properly. “…an individual with sensory processing isms is unsure how to compartmentalise or label interoceptive sensations and to differentiate them from the exteroceptive senses, perceptions from external sources” (13) The messages may get scrambled and a person may think they are still hungry even though they have just eaten a full meal. You can see where this could lead to problems.
These senses combine to create our Sensory Processing System. Our brain has many areas that relay messages to each other to let us know how to act and react in our world. A neurotypical person’s brain can process, interpret and react to sensory input, without hardly any conscious thought, in an appropriate fashion. If we are afflicted with a disability of some sort that changes the way our brains receive messages from our senses, our daily lives can become inhibited or hard to navigate. If we are under-sensitive or over-sensitive to our surroundings, it can cause emotional issues such as anxiety, fear or depression or have an opposite effect of being emotionless or indifferent to the world.
Disabilities that exhibit issues of the Sensory Processing System include Autism Spectrum Disorder (ASD), Sensory Processing Disorder (SPD), blindness, deafness, as well as Asperger’s Syndrome and Oppositional Defiant Disorder (ODD). Depending on the disability and the severity of the disability, therapy may or may not help to train the brain to understand the sensory input it receives and to act and react appropriately. Another factor that plays a role is if the person can communicate effectively. There are many aspects to consider when deciding which therapies to pursue to better the life of the afflicted person. When the final decision is made, it is important that all caregivers, therapists, counsellors, and all involved are aware of the treatment and not go against each other’s treatments because this could confuse or upset the patient.
“Autism is not a puzzle, nor a disease. Autism is a challenge, but certainly not a devastating one.”Trisha Van Berkel
“Children with autism are very observant so they will notice everything. Including your attitude towards them.”Trevor Pacelli