During adolescence the body experiences a lot of transformation, both physical and mental. This includes the brain. At around the age of 6, a child’s brain will have reached 90% of its adult size and will reach its full-size during puberty. However, this does not mean that it is fully matured. The brain is not fully developed until we are in our mid 20s and most of that development takes place during our teenage years.
Advances in brain imagery have allowed researchers to monitor a teenager’s brain in much greater detail than ever before. These studies show that one of the changes that takes place during the teenage years is a change in sleep patterns. A teenager’s biological clock is shifted forward as the brain produces the sleep hormone, melatonin, later than in previous years. Melatonin, the “sleep hormone” that causes the feeling of sleepiness, is released in most adults around 22:00 but for most teenagers the hormone is not usually released until sometime around midnight and is still present in very high levels in the early hours of the day. This explains why teenagers prefer to stay up at night and are extremely sleepy in the morning.
Sleep is important since it is when we access our growth hormones and when we process all the information we come across during our waking hours. In clinical studies, lack of sleep has been clearly linked to moodiness, impulsivity and depression. There has been a movement in recent years to try to start Secondary School later than in the past. In October 2019, a law was passed in California to start high school no earlier than 8:30 in the morning.
Another major change in teenage growth is the development of the prefrontal cortex. The prefrontal cortex is universally agreed to be responsible for “higher-order cognition.” This represents things like planning, decision-making and evaluating risk. This part of the brain does not reach full maturity until well into adulthood. This is what makes teenagers known for acting impulsively and carelessly.
The limbic system is another part of the brain that includes various sections such as the amygdala. The amygdala deals with emotions and emotional responses. The limbic system also includes the hypothalamus system which regulates our hormone production. These structures are still in development during teenage growth and are the cause of mood swings, emotional responses and lead to emotions being felt a lot stronger and more overwhelming than those of a regular adult.
Another important section still in development in an adolescent brain is the increase of myelination. Myelin is a white matter that wraps itself around nerve cell’s axons like long thin tendrils that extends from the cell and transmit information. It's like the insulation on electrical wire. This myelination process is what forms a person's basic learning abilities. This process begins at the back of the brain during adolescence and works its way to the front hence leaving the prefrontal self-control, planning, decision-making area to last.
The increase of myelination, especially in areas of “higher order functions” means your neurons are sometimes communicating 3,000 times more effectively than before. This, in turn, means we learn things more rapidly when we are teenagers.
If you have ever read about brain development, you may have come across the term “pruning”, a term that usually applies to gardening. In neuroscience, pruning represents the way your brain controls its growth. Imagine your brain as a growing tree. At some point you control the growth of that tree by cutting off leaves and branches that you feel are unnecessary. This is what we do to our brains. Scientists call it the “use it or lose it” moment. Our brain, during adolescence, prunes itself by cutting weak connections and breaking down connections between neurons that are not used as much as others. We, ourselves, decide if we want to keep the neuron connections that help us to play an instrument or practice a sport by simply using them. Children learn everything around them, but teenagers decide on their passions and interests through pruning and the consequential neuroplasticity will drive their own brain development. As teenagers their synapses are being established continually in the brain and they themselves will decide on how their brain will develop. Neuroplasticity means what you do with your brain in this period changes the activity and the structure of your brain permanently.
The teenage brain is difficult to understand but even harder to control since all sections are at different rates and stages of development. However, with a fast-growing development in neurology, the future may see small changes in society that are better adapted for teenagers.
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