The Adolescent Brain: Why Gray Matters

The adolescent brain fascinates scientists and scares the living daylights out of parents of teens, everywhere. The scientists are excited because they can now actually see what is happening inside the brain, thanks to better imaging techniques. Parents are terrified because they suspect that the difference between a teenager’s brain and an adult’s brain can be deadly.

Parents don’t need statistics to understand that teenagers are prone to rash and extreme behavior. But if you really want to know, the stats are there. The rate of death by injury between the ages of 15-19 is six times that of kids between the ages of 10 and 14. The overall mortality rate in teens is higher. Crime rates are higher. And finally, alcohol abuse is rampant in teens compared to any other age.

Researchers began studying the adolescent brain in a quest for understanding how mental illness develops. Many serious mental illnesses, such as schizophrenia in which voices and hallucinations are experienced, begin during adolescence. Thanks to Imaging techniques such as fMRI, researchers were at last able to track brain growth and the connection between the brain’s function, development, and human behavior. All in real time.

Adolescent Brain Assumptions

Over the past two decades, scientists found they’d been wrong in many of their earlier assumptions about the adolescent brain. Researchers used to think that the adolescent brain was just an adult brain, if slightly immature. Instead they discovered that the adolescent brain is unique and that the brain is not fully “adult” until the teenage years are but a memory.

Scientists wanted to get to the bottom of an apparent contradiction: adolescents are at the peak of their mental ability, their health and strength. And yet—those crazy mortality rates are through the roof. What makes adolescence so hazardous? Is it something to do with the adolescent brain? Is there anything we can glean from studying the adolescent brain that can help parents guide their teens safely through those years into adulthood?

One clue to understanding teens has to do with how the adolescent brain deals with gray matter. Gray matter is the thin, folding, outer layer of the brain, known as the cortex. The cortex is where we form thoughts and memories. The amount of gray matter increases during childhood and then declines.

Scientists thought that the amount of gray matter was highest in very young children, and that the volume of gray matter fell as the child grew. Imaging scans found something very different. Early adolescence is when peak volume in the brain’s gray matter is reached.

Pruning Gray Matter

What this means is that the brain is still not mature at this time. We know this because the adolescent brain’s gray matter must be pruned away over time to reveal the finalized adult brain in its full glory. We won’t see this adult brain (in imaging scans) until the person reaches his or her early 20’s.

The process of brain maturation is, of course, more complicated than this suggests. Imaging scans show us that different parts of the adolescent cortex are maturing at different speeds and times. The parts of the cortex that control our most basic functions develop first. Our senses, and our ability to control movement, for instance, are primed to mature first. Meantime, the parts of the cortex that help us adults plan and control our impulses (surprise, surprise), mature only much later.

So what is gray matter, anyway? Gray matter consists of the cell bodies that make up the neurons, the nerve fibers they sprout, and the cells that support them. A baby’s brain is distinguished by having lots and lots of synapses, the “wires” that connect the brain cells. Through these synapses, the circuitry of the brain, the neurons can communicate with each other.

A baby is born with more synapses than an adult and these synapses continue to multiply quickly over the first several months of life. A toddler of two has one and a half times as many synapses as his parent. This is no small matter: a 1 millimeter cube of brain matter can hold anywhere from 35-70 million neurons and around 500 billion synapses.

More Efficient, More Elegant

Scientists think that when children lose their synapses, it’s like pruning a tree. Cutting back on the synapses makes the brain a more efficient machine, more elegant. At any rate, now there is no doubt: the adolescent brain’s main feature is that it is in the process of losing gray matter.

The loss of gray matter during the teenage years happens in specific ways, which explains some of the behavior we’ve long noticed in teens. Teens have a stronger reaction to emotions and situations than do adults. This has to do with the signaling of the reward system of the brain that motivates our behavior. Teens feel and react more intensely and sense greater urgency in situations adults may not see as needing immediate attention at all.

The hormonal upheaval going on inside the adolescent brain affects not only sexual behavior but social behavior. The adolescent brain’s response to stress is complicated and can result in bizarre or even dangerous behavior.

The adolescent brain is the equal in intellectual power to that of the adult. The ability of the adolescent to learn is actually greater than that of the adult in terms of taking in, processing, and retaining information. Somewhat offsetting this ability, however, is the still immature impulse control and planning of the adolescent brain, compared to the adult’s. The upshot:  adolescents and adults use different parts of their brains for various mental tasks and to process emotions.

The Adolescent Brain And Sleep

The adolescent brain has trouble regulating the sleep-wake cycle, which explains teenagers who want to stay up late at night and who then cannot wake up in time for school in the morning. Forcing them to get to school on time means they are being educated in a state of fatigue, which makes it hard to pay attention, may lead to depression, and may also explain irritable behavior. Sleep deprivation has, in addition, been found to increase impulsive behavior and even delinquency.

The adolescent brain, in essence, is fully operational, with some of the parts perhaps overshooting the mark for impulse control, planning, and keeping emotions well-checked. The inability to plan ahead or check an impulse, and the strength of the feeling and desire to do something, can cause a teenager to do some mighty risky things. They can’t see the predictable outcome. They feel impelled to do the dangerous, without knowing the full danger. Their brains just don’t see what our brains see.

But you knew all that without any fancy imaging machines.

One Of A Kind Brain

Some scientists are looking at the adolescent brain with new eyes in light of these recent discoveries. Maybe we shouldn’t look at the adolescent brain as “immature” but as a unique and exciting specimen. Something one of a kind.

More pragmatic researchers are hoping to use this greater understanding of the adolescent brain to provide teens with an environment that allows them to explore life while keeping them safe from behavior that could hurt them or others. Part of getting to that point is pinpointing the differences between adolescent behavior and adult behavior to get to a better place of understanding these behaviors.

Take, for instance, the difference between the way teens drink compared to the way adults drink. Adults drink more often than teens. But when teens drink, they consume larger quantities of alcohol. There’s also scientific evidence that the adolescent brain has a different response to alcohol than the adult brain. These differences may help us understand how to protect our teens from binge drinking and from developing an addiction to alcohol as adults.