:Analogies for Sustainable Development/Brain as onion

The Triune brain model: a simplified model of the evolutionary layers of the human brain

Quote Bank

Baler (2016):

"If we zoom into the neuronal circuits and clusters that make up the brain’s systems, we’ll find them laid out like the concentric layers of an onion, functional layer upon functional layer. This arrangement is the result of the relentless evolutionary push to continuously improve on an animal’s ability to navigate its complex and ever-changing environment."

"The core of the onion: autonomous systems... They are in charge of the most basic survival routines like swallowing, vomiting, heart beating and respiration, which are so indispensable that they run, for the most part, on autopilot. Accordingly, they are very hard, though not impossible, to modulate voluntarily. Our human species shares these circuits with fish and reptiles."

"Next layer of the onion to grow: instinct. Our chances of survival were greatly enhanced with the arrival of instincts. Vertebrates benefited tremendously from these pre-programmed circuits that expanded their behavioral repertoire and increased their fitness.... Instincts mediate behaviors so crucial to survival that they are encoded as such in the genes themselves, hard-wired in the brain during an animal’s development and not changed by later experience."

"Let’s examine the next layer: emotion. An amazing breakthrough happened in mammals, with the laying out of a new set of neural substrates capable of generating emotions....it surrounds in its embrace the more primitive survival and instinctual regions of the brain, affording us primates a whole new set of behavioral tools for interacting with the world."

"For example, the instinctual drives to have sex and to run away from danger would be inextricably linked to powerful feelings of affection and fear, respectively. The influence that this new circuitry exerts over our decisions and behaviors is enormous. The neural substrates of emotions are strongly influenced by developmental factors. Perhaps because of its more recent origins, the emotional circuitry is even more flexible and responsive to external influeces than earlier circuits."

"The outermost peel (aka, the neocortex) was overlaid atop an already crowded swarm of networks. In primates, it exploded into two huge hemispheres that completely enveloped the older parts of the brain. This new shell serves as the testing grounds for our still developing reasoning abilities. Because they are so recent, neocortical functions are the most flexible and sensitive to the impact of social and environmental experience."

"it is hard to recognize that the neocortex is constantly competing against earlier webs of well-established brain circuitry, and that its contribution to our motivations and actions are likely less than what we’d expect."

Further Resources

• Wikipedia: Triune brain
• The Brain from Top to Bottom. The evolutionary layers of the human brain

Analogies for Sustainable Development