Humans have eight senses: touch, smell, vision, hearing, taste, proprioception, vestibular and the interoceptive sense.* We take in information about our environment through our 8 senses. When our sensory system is compromised either due to sensory processing disorder or temporary illness such as a head cold this impacts our ability to adequately respond to and engage with our environment. The ability of the brain to organize sensory input varies from individual to individual. For most sensory processing is done automatically and taken for granted. For those with SPD sensory processing is impaired.
Sensory processing disorder (SPD) is a condition where the sensory signals don’t get organized into appropriate responses. A. Jean Ayres- an occupational therapist who developed the theory of SPD and created evaluation procedures and intervention strategies for SPD- described SPD as a neurological traffic jam that prevents certain parts of the brain from receiving the information needed to interpret sensory information from the environment correctly. Thus, an individual with SPD has difficulty processing and acting upon information received through the 8 senses, which creates challenges in preforming everyday tasks. If the brain does not correctly process and respond to sensory information then the individual will not be able to perceive and properly make use of the information from their senses and will not be able to interact with their environment optimally. “Motor clumsiness, behavioral problems, anxiety, depression, school failure, and other impacts may result if the disorder is not treated effectively. One study (Ahn, Miller, Milberger, McIntosh, 2004) shows that at least 1 in 20 children’s daily life is affected by SPD. Another research study by the Sensory Processing Disorder Scientific Work Group (Ben-Sasson, Carter, Briggs-Gowen, 2009) suggests that 1 in every 6 children experiences sensory symptoms that may be significant enough to affect aspects of everyday life functions. Symptoms of Sensory Processing Disorder, like those of most disorders, occur within a broad spectrum of severity. While most of us have occasional difficulties processing sensory information, for children and adults with SPD, these difficulties are chronic, and they disrupt everyday life.” http://www.spdfoundation.net/about-sensory-processing-disorder/
The signs of sensory dysfunction are numerous and often overlap with other conditions. Some common ones include avoidance of certain textures/sounds/games etc., being clumsy, tiring easily, hyperactivity/hypoactivity, spinning and other repetitive purposeful movements, anxiety, aggression, having difficulty interpreting sensory information and responding appropriately to it, difficulty with social interaction, fear of everyday objects or activities such as stairs or swings, and difficulty with concentration. http://sensoryprocessingchallenges.com/images/Sensorytoolhome.pdf
To better understand sensory dysfunction imagine you’re trying to study for a difficult exam at a rock concert while wearing a really itchy wool sweater. How much learning are you actually doing? How receptive to touch and socializing would you be during or after this experience? How might you react if this was how you felt 24/7? http://www.sensory-processing-disorder.com/sensory-processing-disorders.html
One theory on autism, the intense world theory, postulates that sensory overload shuts down the brain during crucial periods of development resulting in the social and emotional delays present in autism. This is not to say that autism would not be present if this sensory overwhelm had not occurred rather the idea is that “early intervention to reduce or moderate the intensity of an autistic child’s environment might allow their talents to be protected while their autism-related disabilities are mitigated or, possibly, avoided.” https://medium.com/matter/the-boy-whose-brain-could-unlock-autism-70c3d64ff221
*Proprioceptive is the body awareness sense. It tells the mind where the body begins and ends and is linked to the tactile and vestibular system. This sense gives us information about how much force to use and through which line of motion to move while doing activities such as picking up a glass of water.
Vestibular is the movement and balance sense which gives us information about where our head and body are in space and allows us to stay upright while we sit, stand, and walk. This sense is involved in the body’s sense of balance and awareness of space, gravity and movement. A malfunctioning vestibular system creates the feeling of being “lost in space”.
Interoception is an internal body sense that senses essential regulation responses such as hunger, breathing, heart rate, and respiration in the body. If the interoception system is impaired this can make it difficult to understand emotional reactions- a well-known example would be when people mistake the symptoms of a panic attack for a heart attack. Their brain can’t explain the sensory input-racing heart etc.- so it thinks its dying and freaks out even more.