Brain Rules: 12 Principles for Surviving and Thriving at Work, Home, and School

BDNF stands for brain-derived neurotrophic factor. This molecule is a group of proteins in the hippocampus that preserves neurons in the hippocampus.

Also referred to as process C, the circadian arousal system is responsible for maintaining the wake portion of the sleep/wake cycle. This system includes brain cells, hormones, and other chemicals working together.

The cortex is sometimes referred to as the “human brain.” It is a thin layer that covers the rest of the brain and contains neurons that communicate to all parts.

Cortisol is a hormone released by the adrenal glands at the top of the kidneys. This hormone is released into the bloodstream when the individual is stressed and can have damaging effects to the health of a person’s body and brain.

Declarative memory is a system of long-term memory that allows for recall of particular facts. Declarative memory has four steps: encoding, storing, retrieving, and forgetting.

The hippocampus converts short-term memories into long-term memories. This portion of the brain plays a significant role in learning.

In contrast to the circadian arousal system is the homeostatic sleep drive, or process S. Like process C, this drive involves a complicated system of cells, hormones, and chemicals to maintain the sleep portion of the sleep/wake cycle.

Larks, or early chronotypes, is a term used for individuals who wake early, usually before their alarm clocks, and feel most productive in late morning and midday. Larks represent approximately one in 10 people.

The lizard brain, or brain stem, is so called because it resembles the functioning of a Gila monster’s brain. The brain stem controls the body’s most basic functions, such as breathing and sleeping.

The mammalian brain controls survival mechanisms, such as fighting or fleeing. This part of the brain contains the amygdala, hippocampus, and thalamus.

Owls, or late chronotypes, feel most productive in the evening and find it difficult to wake in the morning. Most owls would prefer to wake up at 10 in the morning and go to bed at around three at night. 

Medina describes the “performance envelope” as the purpose of cognitive function. Human brains are designed to solve problems to survive. These problems mostly exist in an outdoor environment that is unstable and requires continuous movement. Medina’s rules address the various aspects of the performance envelope. 

The prefrontal cortex is an area of the frontal lobe behind the forehead that helps humans control behaviors. The prefrontal cortex was famously discovered in the 19th century when a man named Phineas Gage suffered a brain injury during a work accident. After the incident, Gage’s behavior and personality altered drastically.

Symbolic reasoning refers to the human ability to imagine qualities and characteristics for things that do not possess them. Simply put, symbolic reasoning is the ability to make things up. It is also referred to as dual representational theory.

Theory of mind is the human capacity to consider and understand the mental states of others. Medina argues that theory of mind was an essential element in the evolution of humans because it enabled them to work together.