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general population. Most individuals have large ranges of comfort and tolerance and can readily adapt to change. However, such adaptation is oftentimes difficult for people who have sustained brain injuries or experienced shocking circumstances. Their protective mechanisms take over and hinder cognitive processing. The nervous system becomes hyper-sensitized.
External environmental signals affect a person’s internal systems. Similarly, internal signals can influence the filtering abilities of external sensory systems. For example, exposure to noise impacts retinal sensitivity. Running with a peaceful water scene in the background elicits different stress chemicals than running while being chased by wild dogs. Sudden, unexpected movement caught out of the corner of one’s eye can cause internal chemical and muscular systems to react. These internal systems, which are beyond conscious control, are triggered simply by a moving shadow on the peripheral retina. When we consider PTSD in this light, we can begin to see the solutions.
Humans have built-in protective mechanisms, and these mechanisms are stronger in patients with PTSD. When they pass their individualized comfort range and go into a tolerance range, some attention and mental energy are diverted to whatever is causing discomfort or an imbalance. Patients with fragile sensory integration or hypersensitive peripheral retinas, such as our patients with PTSD, may exhibit abnormal behavior by reacting internally, below conscious level, to the movement of normal, everyday objects in their environment.
Every system, external and internal, has its own comfort and stress levels as the mind and body react and respond to environmental changes. Constant interaction occurs between internal and external stimuli, involving shifts in eye movement. Shifting light
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