Q. Michael Gurian wrote about brain layers. Layers of what?

A. There are many ways to describe the human brain, that mass of tissue inside your bony skull (e.g., by structure, by anatomy, by individual organs). With the advent of brain imaging technologies, the science of brain function emerged, along with a way to describe the brain in terms of function.

Gurian and others describe the brain in terms of three functional layers, somewhat analogous to Paul McLean’s “Triune Brain” model. Others are now saying there are really four functional layers, labeling the prefrontal cortex (the tissue directly behind the forehead) as the fourth layer that contains high-level cognitive executive functions (e.g., ethics, morality, conscience, complex decision making, planning, managing emotions). Each layer is known for distinct functions, though all functional systems constantly interact.

I find it very helpful to discuss the brain in terms of functional layers, especially when attempting to share complex information in an easy-to-understand format. You can compare these brain layers to gears in a vehicle. To travel most effectively along the freeway of life, you want to be in third gear most of the time.

• Thinking brain layer or 3rd gear – orchestrates conscious rational/logical thought, provides for a variety of executive functions, and is associated with the processing/expressing of emotions. Processes the past, present, and future tenses. Can be compared to the super-ego.
• Emotional brain layer or 2nd gear – includes the pain/pleasure center, generates emotional impulses, and contains selected memory functions (more connections to right hemisphere). Processes the past and present tenses. Can be compared to the ego.
• Action brain layer or 1st gear – houses automatic/instinctual behaviors, protective reflexes, survival mechanisms, and automatic responses to stressors. Processes the present tense only. Can be compared to the id.