Sensory Overload Sensory overload occurs when the nervous system is bombarded by too much, or too intense stimulation for it to process effectively. Although sensory defensiveness can influence sensory overload directly, sensory overload can also occur from the inability of the brain to filter, or turn down, the stimulation coming into the brain. For many of us who do not have sensory processing problems, our brain stems filter out much of the stimulation bombarding the nervous system. It filters out much of the background noise (sensory distraction) that is irrelevant for us to be aware of, so we can concentrate on the task at hand. This allows our brains to comfortably integrate the important information so we can process it smoothly and effectively. We can attend to what we need to because we block out what is irrelevant at the moment. However, for some people with sensory processing problems, this filter does not function effectively, and allows too much stimulation into the brain; taxing and overloading it. The individual is not able to block out the background noise (feels their clothes scratching them, sound of the refrigerator turning on and off, smell of the perfume or deodorant people near them, flickering of sunlight coming through the blinds, conversation going on nearby, the scratching sound of the pencil, etc.) Their nervous system is unable to filter out, or tone down the stimulation. Too much stimulation coming into the brain, at too high of intensity, results in sensory overload. Rather than necessarily being defensive to one sense, as in sensory defensiveness, overload can come from too much stimulation bombarding the brain at one time. For these children the average day at school can be full of sensory assaults. They cannot adequately filter out all the conflicting sensory stimulation. The bright lights may give them a headache, or humming of the lights distract them. Their seat may be too hard and they cannot avoid attending to it. Their clothes may irritate them, sound of the chalk on the board screeching in their head, the whispering of other students distracting them, smells of the markers and glue may be nauseating, and the sound of the bell overwhelming. With all these sensory distractions and irritations, the nervous system is in an escape/avoidance mode, making learning almost impossible. When the brain feels insecure, it goes into survival mode, focusing on protection, not learning. If the stress chemicals build slowly the brain will often start to shut down; to avoid being overwhelmed. During shut down the child may look “out of it”, unresponsive, and sometimes lie his head down and fall asleep. This shut down is the way the brain protects itself from sensory overload. If the stress chemicals build too fast, the child may meltdown, acting out to escape and avoid the assaulting stimulation, as well as releasing the stress chemicals. Either response is the result of the “fight or flight” stress response kicking in. The brain is in “survival mode”, not in a learning readiness mode. This series on sensory issues can be found in the blue book, Autism Discussion Page on the Core Challenges in Autism.
Posted on: Tue, 20 Jan 2015 02:01:14 +0000
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