Brain Function, Hormones and Behavior

There are three parts of the human brain, referred to as the “triune brain”. Paul D. MacLean, an early research director for the National Institute of Mental Health, postulated his Triune Brain Theory which states that the human brain is a product of three stages of evolution and is actually three separate brains which have evolved into one brain over long periods of time.

The first section [the lowest portion of the brain] which is comprised of the top part of the spinal cord, the medulla oblongata, the pons, and the cerebellum, MacClean calls “the reptilian brain” as he stated “at its base [the human brain] was a variation in the elaboration of the reptilian brain.”

The limbic system [located in the mid-portion of the brain] states MacClean, “was an elaboration of the new mammalian brain from the Jurassic period”. He termed it the “mid-brain” or the neo-mammalian brain (new mammal).

The upper most and largest part of the human brain, the cerebral cortex, encompasses our logic centers, our “intellect”. MacClean termed this portion “the neo-cortex” (new cortex).

Viewed through the perspective of MacClean’s “Triune Brain” theory, this is the time line on which the human brain evolved:

1. Reptilian portion = Triassic period – 248 to 206 million years ago. Regulates hunger, body temperature control, fight or flight responses; is shared with reptiles

2. Limbic Portion = Jurassic period – 206-144 million years ago. Regulates mood, memory, hormone control; is shared with older mammals = dogs, cats, mice.

3. Neocortex = Eocene & Oligocene Epochs – 55 -24 million years ago. Regulates logic and thought required for complex social situations, etc; is shared with monkeys and chimpanzees.

The Reptilian or “vegetable brain” [recall the autonomic nervous system functions], is fundamentally concerned with homeostasis, which is involved in regulating all of the body functions that allow each of us to be human, get up every day and live our lives. If you do not have a well-functioning lower brain, if you have a tumor, if you have a trauma, if you’re in an accident, if something happens to your brain stem, you may no longer have the capacity to control the day to day homeostatic functions to maintain your life.

Embedded inside the Limbic System is a structure identified as the Reticular Activating System which has pathways as well as neurons traveling throughout the lower brain, up through the medulla oblongata, across the Limbic System into the Neo-Cortex or the “thinking brain”.

The Limbic System and Reticular Activating System interpret sensory motor messages that are “incoming” from the person’s environment and it is in this portion of the brain that we not only interpret the “incoming stimuli and information” but we also select methods for survival and adaptation.

Here is where it gets exciting to put the anatomy and physiology of brain function and the psychology of personality together!

We know the neo-cortex is our thinking, intellectual brain – our “smart brain” and most of us know individuals who are brilliant academically or intellectually yet they are emotionally dysfunctional in the extreme.

Our thinking brain would presume that being “smart” or intellectually capable would exercise dominion over one’s emotions, however, the missing piece of information here is that our emotions actually are a survival adaptation mechanism that each of us individually develops as we process our early environment and social conditioning. Nothing is more powerful in the human being than its drive to survive! Hence, our emotions win the day in the battle between thinking and feeling.

It is critically important for each of us to understand that our emotions represent how we learned to adapt in our surroundings and environment, especially during the first 0-5 years of our development. Our familial “input” taught us, as did Pavlov with his dogs, how to respond to the stimuli we received as infants and toddlers.

This embedded neurological conditioning is not overcome by the thought process, as the thought process for humans is the “newest” component to our primordial brain. It is in the survival adaptive portion of our brain where we form our “personality” and where we become conditioned to create and interact within relationships.

When we understand the possibility that interpersonal issues which frustrate us may come not from “being difficult” or “bad intent” but rather from our drive to survive and our interpretation of the stimulation and environment we were conditioned by, then we can begin to be “kinder and gentler” towards ourselves and others.

In summary, our emotions are the way we learn to live, behave and survive in our world. We cannot “think them” into changing, but we can step back and appreciate the service and challenge they offer us in our daily lives.

With all good wishes,

Copyright 2010 G. Donadio