Our Three Brains

OUR THREE BRAINS

Paul MacLean says that we have three brains.

MacLean called the first, most primitive, brain the reptilian brain. It is focused on individual survival and knows neither friend nor family nor fun.  In humans this consists of the brain stem, which maintains the vital functions of life, including heartbeat, breathing, metabolic activity, and the cerebellum. Even when extensive brain injury occurs, if these areas are preserved, life can continue.  The behaviors of this part of the brain are very resistant of change, tend to be grounded in fear, and are not capable of learning. This part of the brain is quite limited in its response to challenges. - Reptiles (or human operating in the reptilian mode), when perceiving threat, only attack, flee or freeze.

MacLean called the second brain the mammalian brain. It includes the amygdala, a more refined sentry for danger than exists in the reptilian brain. The amygdala joins with the hypothalamus, the pituitary and the adrenal glands to coordinate our most basic fight-flight-freeze responses to protect us from harm. The amygdala is activated automatically, without thought.  For example, you walk out your front door, and you see a shape on the grass that looks like a snake. You immediately jump back with fear.  Then you look more closely and you see the shape is actually a garden hose. You relax, laugh, and go on your way.  The initial reaction was the instinct of the early mammalian brain, including the amygdala.  If that’s all you had, you might have attacked or run away from the garden hose.

Our more evolved mammalian brain has a more sophisticated sentry, the hippocampus, capable of refined perceptions and feelings.  It was the hippocampus that helped you realize the garden hose was not a snake.  The hippocampus has the capacity for learning and memory, which gives mammals additional abilities.  Unlike a reptile, your pet dog recognizes and responds to you, and obviously makes the distinction between you and a stranger.

The third, highest, component is the human brain, which includes the large cerebral cortex, making up five-sixths of the brain.  This is our thinking brain, with numerous connections between the hippocampus and the prefrontal cortex.  The prefrontal cortex connects many large neural networks that allow for the various qualities of human thought, reflection, and wisdom.

The cerebral cortex is involved with most advanced mental activities including speech, rational thought, memory, understanding fine motor control, creativity, musical ability, writing, empathy, kindness, the ability to be part of a family or group and still be an individual, awareness of the story of your own life, and the recognition of time.

Most of the stress we experience cannot be handled well by the primitive brain, with its fight-flight-freeze reactions, or by the ancient or more advanced mammalian brains, with their limited capacities governed by instinct, group conformance, and pecking order.

 Only by accessing our human brain can we step back, reflect, and take conscious action. 

Taken from The Inner Game of Stress, W. Timothy Gallwey, pages 50-53.