Psychology – Human Tripartite Brain – Paul MacLean

Posted in Psychology on the 07.02.2012

Be able to tell which three parts MacLean has divided the brain into.

Paul MacLean (1913 – 2007) was an American neuropsychologist.   He was the first who presented the tripartite brain. This is a theory that locates the psychological functions to specific brain areas.  It also violates the considerable interest in how our emotions and reason interact, which one has been interested in neuro-psychology since 1990 – s. According to MacLean the brain has evolved in step with the long evolutionary development of man from animals to humans.  He believes that the brain is mainly made up of three different  areas, each of which corresponds to a stage of development in evolution, and each area has, according to MacLean’s own intelligence, its own memory and its own very special way to respond to the pressures it is subjected for.

MacLean divided the brain into three parts:

Reptiles brain:

Is the brain stem, cerebellum and basal time lines, the most primitive part of our brain that is more than 500 million years of evolution. This part of the brain controls our most vital functions such as sleep, heart rate, breathing and the like. Moreover, this part of the brain active in connection with the experiences of stress and fear through their connection to the pituitary gland. In other words, made this part of the brain of a collection of innate and reflex control programs that ensure individual survival by keeping an eye on the body acts and reacts as it should, and by ensuring that certain external influences are avoided.

The former mammalian brain:

MacLean said that the former mammalian brain consisted of brain structures like the hippocampus, amygdala and hypothalamus, which together constitute what we call the limbic system. While the reptilian brain relies more on instinctive behavior and innate reflexes, the brain through the limbic system added an emotional dimension. So emotions are the brain’s way of remembering how different situations affect our organism. It is in this part of the brain that emotions such as anger, sadness and surprise are capitalized and recognized.

The newer mammalian brain:

If two or more layers of brain cells that grew on top of the earlier mammalian brain only two layers thick cortex, MacLean called this here neokorteks (new cortex).  This part of the brain is much larger in humans than other mammals, and it is the one that helps with what one might call the special human traits such as language, thought and impulse control. It’s actually this part of the brain that enables us to do much:

It enables us to move from reaction to reaction, so that we not only respond to external stimuli, but also is able to take action to get something to happen. It also gives us the ability not to take action in specific situations.  Equipping people with the opportunity to reflect on their feelings and thus suppressing or inhibiting more impulsive reactions that are activated in the brain’s older parts, gives people an actual free will, and this area is where we maintain our awareness of ourselves.

Some damage in the cortex means that you suddenly lose the ability to control the tears – and laughter attack.  In other words, the cortex is an important inhibitory function of the brain’s older parts.