Page 420 - Total War on PTSD

through eyesight, but also through luminance (external light) dispersed across the retina. Concurrently, the retina receives feedback signals from the body through informational pathways in the brain. This continuing process of feeding forward signals to the brain from the environment and receiving feedback signals from various brain structures makes the retina a two-way portal for influencing and monitoring body functions and thought processes, primarily below the level of consciousness.
Each eye contains approximately 126 million light-sensitive receptors. Input information from these receptors move through a sophisticated filtering system, resulting in some 1.2 million signals traveling across and radiating out from the optic nerve into electrical and chemical pathways inside the brain. In fact, the retina connects with many systems other than eyesight, including structures in the brain’s cortex, cerebellum, and limbic system, as well as midbrain and brainstem. These structures affect the body’s physiological, biochemical, behavioral, and emotional responses, including endocrine, respiratory, circulatory, circadian, digestive, and musculoskeletal systems.
As a result, the body’s survival and the mind’s executive functions are greatly influenced by changes in external sensory inputs. For example, if we are crossing a busy street and see or sense traffic speeding in our direction, we automatically, almost unconsciously, hasten our step or run. Conversely, external attention and awareness are altered by shifts in the body or mind. For example, if we are concerned or thinking we might be late for an important conference or a scheduled appointment we hasten to the meeting location with singular, focused attention on timely arrival. In those moments, we have limited spatial or environmental awareness of other people and activities around us, including busy traffic. Our only goal in that moment is to reach our desired destination on time. As such, selected stimuli is processed — those directly related to the goal of arriving on time. Environmental details that an individual would normally notice and process are passed by obliviously. In patients with PTSD, this type of constriction is an everyday
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