Thoughts: The Prefrontal Cortex, also known as the “thinking brain,” is the manager of executive functions. These include “memory, judgment, planning, sequencing of activity, abstract reasoning…impulse control, personality, reactivity to the surroundings and mood.” This area is what allows humans to solve math problems, develop abstract concepts, and ponder our own existence. It is also the area that military leaders use to balance risks in combat, develop courses of action, and create strategies to effectively lead units.
When the limbic system is heavily engaged, as it is during the high-threat stress of combat, it will quite literally steal fuel from the prefrontal cortex, thus handicapping a Soldier’s ability to combat the situation with cognition. The relationship is such that “the degree of activation of the limbic system is the degree of deactivation of the prefrontal cortex.” Brain research has also shown that there are many more neural connections that flow from the amygdale directly to the prefrontal cortex than vice versa. Therefore, it is easy for our emotions to guide or suppress our rational thoughts.
Emotions: Combat is full of stressful moments that will test our emotional resolve. They can occur during initial contact with the enemy, or when rushing to secure enemy terrain, or when reacting to an unexpected event. Soldiers will experience intense sensory input in the form of debilitating explosions, grotesque scenes, and threatening enemy movements. As it attempts to keep pace with the exciting environment, the limbic system will perform as it was designed to and starve the Soldier’s ability to maintain a clear mental framework. Coupled with the typically exhausting physical exertion of combat, he is at risk to suffer degraded cognitive processing, inaccurate decision-making, and reduced insight generation.
As combat will readily reveal, the body and mind will undergo rapid changes when reacting to stress. Heart rate, blood pressure, and breathing will all increase; digestion will slow and nausea may occur; speech may falter; and auditory and visual cues may diminish. All of these effects are natural, as the body emotionally reacts to the fight. However, optimal combat (or high-stress) performance requires the Soldier to control the effect of emotional energy and remain calm in the face of danger. While moderate levels of heightened stress improve functions like motor skills, stress can easily impair performance in cognitive areas, where today’s military typically operate.
Physiology: The limbic system is evolutionarily older than the prefrontal cortex, primitively old, in fact. It developed to survive the ancient, two-dimensional battlefield of predator versus prey that our forbearers faced. It has the “chemical authority” to initiate rapid responses to threats and is good at doing so. The amygdale ignites; adrenaline flows to the blood; the pulse races; the eyes zoom in and rapidly scan for a threatening movement. The body halts the unnecessary digestion process and tenses the major muscle groups in preparation for a clash. Then the brain, teeming with blood vessels, redirects the available supply of oxygen and glucose-rich blood to the limbic and motor areas that you will need to react quickly in the impending fight. At this point, the mind is in its most basic survival mode with no spare energy to devote to geometry or to philosophical dilemmas or to any extraneous thought. This biological decision to focus resources towards limbic areas during dangerous situations is what keeps us alive when a cerebral problem-solving approach would be fatally slow.
Emotion is an instinctive response aimed at self-preservation. It involves numerous bodily changes that are preparations for action. During a fear reaction, the amygdala, in concert with numerous other structures in the brain and body, help to trigger a staggeringly complex sequence of events, all aimed at producing a behavior to promote survival. When the reaction begins neural networks are activated, and numerous chemical compounds are released and moved around in the brain and body. The most well known among them is the so-called adrenaline rush. Adrenaline is a trade name for epinephrine…but it is norepinephrine that is largely responsible for the jolt you feel in the heart when startled. Cortisol (a steroid), which is released from the adrenal cortex, also amps up fear among other effects. The net result of all the chemicals that come streaming through your system once the amygdala has detected danger is that the heart rate rises, breathing speeds up, more sugar is dumped into the metabolic system and the distribution of oxygen and nutrients shifts so that you have the strength to run or fight. The knot in your stomach results from the redistribution (as well as from contractions of the smooth muscle in the stomach) in which the flow of blood to the digestive system is reduced so that it can be used elsewhere to meet the emergency. The blood changes its chemistry so that it can coagulate more rapidly and muscle tone alters. All of this happens to put you in a state of high readiness.