When people describe the period of adolescence, what word(s)/phrases do you think most readily come to mind? Hormones? Acne? The toxicity of the hookup culture? Freedom? How about change? Yes, change! The teenage years are notorious for the constant environmental changes that ensue during the age of 13-19: new friendships, relationships, and schools moving from junior high to high school, getting your driver’s’ license, graduating high school etc. But while teens’ external worlds are being jostled by the exciting novelties off teenage agency and freedom, their internal worlds—namely, their brains— are also experiencing a paradoxical stage of development and inability unique to these people on the precipice of adulthood.
In developmental neurobiology and psychology, it was previously thought that the most significant burst of neural development occurred during the early childhood years, but decades of research has shown that the teenage years are rife with neural blossoming and blooming. In fact, the brain is only about 80 percent developed in adolescents. (1) As brains mature, they do not grow larger, instead, they become more connected by myelination. Myelination is the process by which the axon, the part of a neuron that conducts electrochemical impulses from the soma to the dendrites of the cell, becomes coated in glial cells, which improve the insulation of a neuron and its speed in transmitting neural communications. Myelination occurs from the back of the brain to the front, which is why the prefrontal cortex (PFC), the brain’s crown jewel for rational decision-making and higher-order cognitive processes, is offline until a person’s mid-twenties, perhaps maybe until a person turns thirty years old. Because of their lack of a fully ripened PFC, teens rely on other brain structures and the amygdala, a brain structure implicated in aggression, anxiety, and fear, in order to make sometimes faulty choices. When the frontal cortex eventually fully develops, its aim is to promulgate a more efficient brain rather than the more physical brain.
Besides a fledgling prefrontal cortex, the teenage brain hosts many neuroanatomical wonders. The ventral tegmentum sends dopamine projects to the nucleus accumbens and the frontal cortex. These two pathways experience increased dopamine density and signaling during adolescence, which means that teens experience more potent bursts of dopamine than adults or children. Dopamine is a neurotransmitter which is often implicated in happiness and pleasure, but it mainly controls the anticipation of a reward. This probably is not shocking information, but teens have this habit of reacting emotionally to many things. This is chiefly because teens are more responsive to emotional signaling and are more susceptible to peer pressure than their adult or child counterparts. Because of better myelination, adolescent brains have greater capacities for neural plasticity, which is the brain’s ability to adapt to changes by forming new neural circuits during a person’s life. Neural plasticity can be useful in a myriad of situations, from stroke patients to people stricken with diseases that impair perception skills to teens who have synesthesia. A 2011 study states that IQ evolves as teens age. In 2004, teens aged 12-16 were IQ tested and then retested in 2008 when they were 15-20 years old. The study showed that as the frontal cortices of these teens packed on more external experiences, these adolescents’ IQs either increased or decreased. (2) Teens certainly are in a period of unimaginable neural potential.
For all its numerous marvels and wonders, the adolescent brain is not invincible and falls prey to various pathological predators. The frontal cortex is the region of the brain that is predominantly shaped by the experiences of adolescence more than any other part of the adult brain. A well-functioning frontal cortex is important for mastery of and control over personality, executive function, emotional regulation, and gratification postponement. In the words of Dr. Robert Sapolsky, Stanford primatologist and endocrinologist, “the frontal cortex makes you do the harder thing when it’s the right thing to do.” When a teen’s frontal cortex is damaged by a head injury or drug and alcohol abuse, there are repercussions for that teen’s burgeoning adult brain. More tragically, early adolescence is the onset of many mental illnesses like schizophrenia, bipolar, depression, and psychosis. (3) This period of cognitive exploration can also be a time of great vulnerability. This is the marvel of the teenage brain.
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