The Lower Brain: Fast Track and Unconscious



From Bouncing Back by Linda Graham:


The lower brain controls our hard-wired responses to any stressor. In evolutionary terms, these were our earliest survival strategies.


Our initial perceptions of and reactions to safety or danger are always processed first by the limbic system (the five structures of the midbrain), especially by the amygdala, our brain’s 24/7 alarm center, located just below the orbitofrontal area of the prefrontal cortex.


This tiny structure constantly scans signals from the environment (filtered by the thalamus) and assesses them for safety or danger — assigning them an initial appraisal of good or bad.



The amygdala, like all structures of the lower brain, operates entirely without conscious awareness and draws on its own implicit memories — those stored outside our awareness — to distinguish between safe situations (“good”) and potentially dangerous ones (“bad”) that require an immediate reaction.


Signals from the body that a situation is safe are also processed by the vagus nerve in the brain stem: the “vagal brake” keeps the nervous system calm and relaxed.


But when the amygdala evaluates a person or situation as dangerous, within milliseconds it sends electrical and chemical signals along neural pathways to the prefrontal cortex.


The signal “Do something!” is our first automatic survival response.


It involves an immediate reaching out for connection and help and further assessment of danger.


This is the neurobiological process behind the drive to seek connection and reassurance when we experience fear.



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