Trouble in Mind

A neuropsychologist muses on brains, books and being happy

Brilliant, Brazen, Teenage Brains

Teen brains, crazy behavior, and independence.

In their excellent article on Teenage Brains (October, 2011), National Geographic quoted Aristotle, who wrote that "the young are heated by Nature as drunken men by wine."

It is remarkable that the comparison between teenage and inebriated behavior was made 2300 years ago. Neuropsychologists and parenting advisors (at least those who have a knowledge of neuropsychology) often try and calm parents down when they are pulling their hair out over their teens' rude, moody, disorganized, risk-taking, impulsive behaviors. The frontal lobes (or more correctly, the prefrontal lobes) of the teenage brain, they tell the parents, are still developing. By the age of twenty to twenty-five, the frontal lobes will be fully mature and the impossible teenager will morph into a normal person—a fully functional, socially well-adapted adult.

This is not simply psychobabble, but backed by numerous brain and social behavior studies. Brain maturation occurs as axons-the long nerve fibers that allow the neurons or nerve cells to connect- are encased in a fatty substance called myelin. This insulates the axon, allowing more rapid transmission of signals down the axon and across the gap-synapse-to the next axon. The better myelinated our axons are, the faster and more efficiently we can think. Before myelination is complete, little branches off the axons—called dendrites—proliferate, allowing richer connections between neurons. Another process that speeds up in the frontal lobes during teenage years is synaptic pruning, where synapses that are frequently used strengthen and those that are rarely used lapse.

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In early childhood, synaptic pruning and myelination of the axons is concentrated in the posterior brain areas. These are the areas where our sensations are received and made sense of. We learn to recognize people and objects and understand how they fit into the world. Our memory develops. By the age of twelve our ability to comprehend language and speak is pretty much complete. Thus, brain maturation occurs in a sequence from back to front, with the frontal lobes last. Indeed, the frontal lobes were also the last areas of the mammalian brain to evolve—humans have by far the most developed frontal lobes of any living creature.

The frontal lobes are, in fact, on line and working hard from babyhood onwards, but they mediate numerous complex functions, and it is the more abstract and higher-level skills that take time to mature. Fifteen-year-olds have not yet fully developed the ability to understand the consequences of their actions and act accordingly. They have difficulty with planning and organization, and learning from their mistakes. They often act impulsively or inappropriately, they have roller-coaster emotions, and working towards distant goals rather than being unduly influenced by immediate rewards is a stretch for them.

The fact that your teenager doesn't have fully developed frontal lobes doesn't entirely excuse crazy risk-taking behavior or rudeness, as they can moderate their behaviors. It just takes them a lot more effort to do so. The trick to being a parent of teenagers is to know where to set boundaries, when to insist on mature behavior, and when to let it go. "Don't sweat the small stuff" is a good motto.

The brain evolved in this way for a good reason. Teenagers need to take risks in order to make the leap from home and reliance on parents to independence. At this stage, their primary alliance shifts to their peer group, the most important social group for young adults. Teenagers who do not develop mature frontal lobes because of some neurological or developmental problem often remain dependent on their parents, and are unable to live a fully adult life. No parent wants that.

Aristotle's comparison of youthful behavior with drunken behavior is apt in one sense: alcohol is an organic neurotoxic solvent and directly affects the brain, and in particular the efficiency of the frontal lobes. One or two drinks in an appropriate environment (ie: not at the wheel of a car) can act like a gentle release of the "behavior police," allowing a usually shy or inhibited person to enjoy themselves in a perfectly acceptable way. It is a different matter when someone is acutely intoxicated. With the frontal lobes dampened down by alcohol, the person behaves inappropriately, is unable to see the consequences of their actions, takes dangerous risks, drives recklessly and believes their driving is safe, and gets into fights quickly. But unlike the behavior of the normal teenager, this intoxicated behavior has no positive side, and in fact may also be causing gradual and permanent damage to the brain.

There are also many neurological disorders that result in frontal lobe damage. One of the most common is head injury. People who suffer severe head injuries are almost always left with some frontal lobe problems, and as difficulty learning from their errors is one of these problems, these people are notoriously difficult to rehabilitate. Many parents have their lives turned upside down when a teenage or adult son or daughter suffers a bad head injury in a car crash and comes home for good, in many respects a teenager for ever more. This time, however, the "teenager" has very few of the positive aspects of being a teenager, just the inappropriate behaviors and mood swings.

Normal teenagers, with their not-quite-mature frontal lobes, are particularly vulnerable to alcohol and drugs that target the frontal lobes. Their "normal" risk-taking behaviors become rapidly much worse, often after very little to drink. A parent's worst nightmare is the teen who gets drunk and drives home, has a car crash and sustains a head injury that results in permanent brain damage. Sadly this scenario is only too common, especially in the "silly" season, as Christmas is known in some countries.

So teens out there: you don't need excessive booze and drugs to enjoy yourselves—you already have frontal lobes that love parties! Look after your brain now, and it will give you—and your parents—a lifetime of good experiences.

 

Jenni Ogden, Ph.D., is a clinical neuropsychologist and author of Trouble in Mind: Stories from a neuropsychologist's casebook, and the text, Fractured Minds.

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