Paul MacLean

An interest in the brain requires no justification other than a curiosity to know why we are here, what we are doing here, and where we are going.

Summary

Paul D. MacLean (1913 - 2008) is an American physician who made significant contributions through his research to the fields of physiology, psychiatry, and brain research.

He was instrumental in proposing and defining the triune concept of the brain - that the human brain was in reality three brains in one; the R-complex, the Limbic system and the neocortex.

He also established that the Limbic System is the main regulating centre of the viscero-emotional functions (see Physiological Aspects of Biodanza).

Ideas

• MacLean became interested in the brain's control of emotion and behavior,
• After initial studies of brain activity in epileptic patients, he turned to cats, monkeys and other models, using electrodes to stimulate different parts of the brain in conscious animals,
• He then recorded the animals' responses and began to trace individual behaviors like aggression and sexual arousal to their physiological sources,
• He termed the brain's center of emotions the Limbic System, and described an area that includes structures called the Hippocampus and Amygdala,
• He proposed that the Limbic System had evolved in early mammals to control fight or flight responses and react to both emotionally pleasurable and painful sensations,
• He later enlarged his theory to address the human brain's overall structure and divided its evolution into three parts, an idea that he termed the Triune Brain,
• In addition to identifying the Limbic System, he pointed to a more primitive brain called the R-complex, related to reptiles, which controls basic functions like muscle movement and breathing. The third part, the Neocortex, controls speech and reasoning and is the most recent evolutionary arrival.