The human brain is comprised of 100 billion neurons organized to sense, process, store, and perceive. These neurons and our brain tissue are designed to continually change in response to external and internal stimuli. They process colossal amounts of incoming information, simultaneously, instantaneously, with one purpose that overrides all others: SURVIVAL.
The way we understand and make sense of our lives involves the creation of internal representations of the external world, a process which depends on the patterns, amount, and frequency of neural activity. The more often a certain pattern of brain activity occurs, the more encoded the internal representation. This information is then sorted and stored according to how much we need it. It is therefore use-dependent: the more we reference certain types of information, the more available they are.
A key concept in understanding why we do the things we do is this:
Activation of a neural network over and over again creates a template through which all input is filtered. Therefore neurons that fire together become wired together.
The most used synapses will survive, explains Dr. Gerald Edelman, Nobel prizewinning neuroscientist. He terms this use-it-or-lose-it principal neural Darwinism—survival of the fittest, or most used, synapses. This explains why cab drivers, who memorize city streets, often have an unusually large hippocampus, a part of the brain that stores memory.
If we, as children, frequently experience fear or discouragement, then it follows that we, as adults, would more frequently repeat these same chemical and thought patterns. The experience of anxiety and/or depression can be the result of genetics or environment or a mix of both. By the age of three, our brains are 80% of their full size and 90% by age five, at which point we have all the neurons we will ever have. It is no wonder, then, that if we look back to childhood events and the ways our families interacted, we will find reasons why we think and act in the here-and-now. (Also see: Triggers and the Window of Tolerance)
Disruption of brain development can have different outcomes, depending on the child’s age and developmental stage. Trauma in early childhood can change the way we process information and experience emotion. This may limit our ability to risk and/or navigate intimate relationships. In teen years, the brain goes through another period of accelerated development, pruning unused neurological pathways to provide more efficiency in the prefrontal cortex, home of the executive functions. This is why teenagers get sleepy. More sleep allows their brains to reach adult dimensions and further develop the ability to: plan, set priorities, organize thoughts, suppress impulses, and weigh the consequences of one’s actions.
A few specifics about brain development in adolescence help us further understand the importance of protecting our teens. Protection includes actionable steps like: simplifying scheduling demands to protect down time; providing help with planning and prioritizing; talking and reasoning through the possible outcomes of complex decisions that might be life-changing.
Fledgling neurology may explain why adolescents so frequently misread emotional signals, seeing anger and hostility where none exists; example: “That teacher hates me!” (Deborah Yurgelun-Todd, Harvard neuropsychologist at McLean Hospital, Belmont, Mass)
Rapid changes in dopamine-rich areas of the teen brain may be a factor in making teens vulnerable to the stimulating and addictive effects of drugs and alcohol. Dopamine, abundant and active in the teen years, is the brain chemical involved in motivation and in reinforcing behavior.
An immature nucleus accumbens may be why it is hard to get a teenager off the couch. It also explains why immediate rewards are still essential in adolescence. This region, in the frontal cortex, directs motivation to seek rewards. Less activity in the nucleus accumbens may explain why teens have less motivation than adults, making them more prone to high excitement and low effort activities. (James Bjork at the National Institute on Alcohol Abuse and Alcoholism)
Getting a teenager to go to bed and wake up on a regular schedule may have less to do with frontal lobe reasoning than with the pineal gland at the base of the brain which produces melatonin, a chemical that signals the body to begin shutting down for sleep. Studies are showing that because it takes longer for melatonin levels to rise in teenagers regardless of exposure to light or stimulating activities, the brain’s program for sleep is later. (Mary Carskadon at Brown University)
As we review critical neurological development during adolescence, we can also see that challenges during these roller coaster years may have left us all with unfinished tasks as we continue to grow into our most mature and capable selves.