Sensory Dysfunction

We learn about the world through the five senses: sight, hearing, touch, smell, and taste. In addition, the development of our nervous system is also strongly influenced by proprioceptive (ability to orient our body parts in relation to our body) and vestibular function (ability to orient and balance ourselves).

Information that comes from the environment through the sensory organs (eyes, ears, skin…) is channeled through the afferent nervous system to various parts of the brain where it is received and processed. Sensory dysfunctions can occur because the sensory nervous system has failed to mature correctly due to a genetic predisposition, injury or lack of stimulation caused by insufficient experience or sensory organ damage. This is more fully explained under the section FUNCTIONAL, SENSORY AND DEVELOPMENTAL NEUROLOGY.

Because each person has a unique nervous system based on his or her genes and experience, it can be postulated that each of us has a different sensory experience of the world. For example, some of us are more ticklish than others or are more sensitive to light. In those individuals who have a nervous system that falls outside the “typical”, this difference can be exaggerated to the point that it interferes with normal functioning. For instance, when you pick up an orange, your senses communicate this information to your brain. Your vision identifies the colour and the appearance of the orange. Your touch senses the oiliness of the rind and the smoothness as well as the slight dimples in the skin. You perceive that there is weight to the object; it is not hollow. Your sense of smell distinguishes the distinctive citrus smell. It doesn't rattle or make noise, so your hearing helps you realize that it is a solid object. All of your senses combine to tell you that this is, in fact, an orange. What if our senses were dysfunctional? What if the orange felt like most of the other objects that you have encountered; that it didn't feel different? There was no heavy or light feeling, no texture that you could distinguish. What if you couldn't identify the citrus smell? Worse - what if your senses perceived the orange to feel mushy and overripe, and the pleasant citrus smell as a horrible stench? Perhaps, you might avoid the orange. If your senses were constantly giving you false information, your view of the world may be very different - most of all, it probably would be different from everyone else's point of view.

This is sensory dysfunction. Individuals with a broad range of disabilities ranging from mild learning disorders to severe neurological impairments can experience various degrees of sensory dysfunction. These include, but are not limited to people who experience: Acquired Brain Injury, Speech, Reading and Learning Disabilities including ADD and ADHD, Autistic Spectrum Disorders, Brain Injury at Birth, Cerebral Palsy, Developmental Disabilities, Down Syndrome, Fetal Alcohol Syndrome, Perceptual Problems, Sensory Motor Disabilities and Stroke.

There are two main types of sensory dysfunction: "hyper" (over-active) or "hypo" (under-active). Here are some examples in which the senses are not operating correctly. Children who are oversensitive to noise (hyper-auditory) distract very easily. The slightest noise disturbs them and they may have difficulty concentrating. The noises that we normally filter (the noise of a ventilation fan, the hum of fluorescent lights) can pose a significant problem for them. As a result, one of the ways they have to protect themselves from auditory overload is to disconnect themselves from their environment. Our objective is to reduce the child's sensitivity to noise, and enable them to connect with the world around them.

The hyper-visual person may have a low tolerance to sunlight and fluorescent lighting. For example, a child in a classroom under fluorescent lighting using white paper may experience glare from the paper, which may cause a visual distraction. Recommendations for this child may include visual exercises to reduce their sensitivity to light and thus normalize this sensory channel.

Hypo-tactile children tend to need to move around constantly. These children often have the need to feel pressure and they may lean on or over objects. They can have a high tolerance for pain and are often heavy walkers. Recommendations for these children may include the application of deep pressure to their limbs.

To view a list of some of sensory behaviours, click on “SENSORY BEHAVIOURS”