The transformation from child to adult is complicated, to say the least. To begin with, puberty starts younger than ever, between the ages 8 and 12 for girls and 9 and 14 in boys.

As neuroscientists have discovered that a crucial part of the brain undergoes extensive growth and change during puberty, adolescence can make the terrible twos seem like, well, child’s play. For example, the same characteristics of a toddler-stubborn, impulsive, self-centered, emotional, rebellious-resurface in later years as a teenager.

Only this time when a teenager throws a temper tantrum, a timeout is no longer a valid discipline. Not only that, the consequences of their defiant actions are more serious, especially if they put their lives and the lives of others at risk by being sexually active or using drugs and alcohol. Of course not all teenagers engage in this high-risk behavior, but their unpredictable personalities are bizarre nonetheless.

With the aid of new technologies such as magnetic resonance imaging (MRI), researchers are finding evidence that the brain is actually under construction for decades. The vast majority of brain development takes place in two basic stages. The first stage is called “blossoming,” which occurs in utero and throughout the first several months of life. At that time the human brain grows at a lightning-quick pace and produces millions of brain cells.

The second wave occurs roughly between ages 10 and 13 and is quickly followed by a “pruning” process in which the brain breaks down its weakest and least used connections. A favorite phrase of neuroscientists is “neurons that fire together wire together,” explains David Walsh, a nationally renowned psychologist and author of the book, “Why Do They Act That Way?”

According to Walsh’s practical parent survival guide, “The more (neurons) fire together-pass on an electrical charge from one cell to another-the stronger the connections between the neurons become. By firing repeatedly, the neurons that do the work of thinking make the connection strong enough to hold, such as when we learn a foreign language. If we don’t use certain neurons, they don’t get wired into the networks and, as a result, they are expendable.”

For example, if teens are involved in music or sports or academics, those are the cells and connections that will be hardwired. If all they do is lie on the couch and watch television or play video games, those are the cells and connections that will survive. The brain cells used most during puberty and adolescence are the ones that will become hard wired and most used in adulthood, so unless their future career is inventing the latest video game for Nintendo, they’re wasting their time.

As adolescents physically grow into their adult bodies, their nervous systems are still very immature. So what exactly is going on inside a teen’s kepala? To start with, fireworks explode in the prefrontal cortex (PFC), which is the part of the brain located just behind the forehead and is key to understanding adolescents. The PFC, by the way, is the last brain area to develop.

“The PFC, or executive center of the brain, regulates how the brain and other parts of the body function. Think of it as the conductor of the symphony or the CEO of a company,” says Dan Weinstein, a St. Louis licensed psychologist who specializes in children, adolescents, and young adults struggling with difficult emotional, behavioral, and relationship issues. “This area is responsible for understanding cause and effect relationships, drawing from past experience to guide future behavior, planning, sequencing, making decisions, sustaining attention, controlling impulses, regulating mood, and other vital brain functions,” adds Weinstein, also known as “Dr. Dan” in our neck of the woods and a valuable local resource for families.

Another area of the brain that experiences rapid change is the amygdala, which is associated with emotional and gut responses. New imaging studies suggest that teens interpret emotional information with this reactive part of the brain whereas adults rely more heavily on the more thinking regions, the frontal cortex. Scientists speculate that this may explain why teens have trouble modulating their emotional responses.

Other brainstorms throughout adolescence occur in the corpus callosum, which is a cable of nerves that connects the two hemispheres of the brain and is believed to be involved in creativity and problem solving, and the cerebellum, which involves the coordination of thinking processes, as well as muscles and physical movement.

Still another puzzling aspect of adolescent behavior-sleep-really hits a nerve for many parents.

“During puberty the way the brain regulates sleep changes and the amount of required sleep starts to change,” says Weinstein. “Also the sleep/wake cycle makes a shift. Melatonin-the hormone that helps regulate sleep-changes in terms of when it activates and causes fatigue. Teenagers in general do not become tired until later in the evening and are less alert early in the morning. They also tend to stay up later in response to body cues, plus using social networking, chat rooms and playing video games late at night doesn’t help either. Consequently, they do not receive the nine to nine-and-a-half hours of sleep recommended, and yet they are expected to wake up early for school.”

In addition, Weinstein says that sleep deprivation can impair memory and compromise the immune system. Research shows that after we go to sleep the brain consolidates and practices what we learn during the day, which means for teens that sleep after a lesson is as important as a good night’s rest before a test or exam.

So what does all this mean to parents and, most importantly, how can we motivate our teens to throw their wet towels in the laundry basket as effortlessly as they dunk a basketball into a hoop?

Thousands of years before the positron emission tomography (PET) and other powerful machines were invented to study the brain, the wise Jewish scholars foresaw the best way to deal with teenagers. In the Talmud, for instance, the centuries-old advice on modern family dynamics is written, “Be it your way to thrust him off with the left hand and draw him to you with the right hand.” In other words, practice tough love, baby.

Despite all the new scientific advances, researchers suggest that the most beneficial thing for teenagers is family support and a loving relationship with their parents. Even though our teens seem to push us away, they want us to be there for them. The developmental task of a teen is to begin to separate from their parents and connect with us in a more adult way. It’s our job as parents to provide structure, guidance, and help keep them on the right track as their brain undergoes major construction. Weinstein suggests good communication is essential, and so is striking a balance between boundaries and freedom.

“Parents need to set firm and consistent limits and consequences, provide clear expectations, and follow through with those limits and consequences,” says Weinstein. “Logical consequences are best, and they also need to be realistic and enforceable, not just empty threats. For example, a teen can write a letter of apology after causing a serious insult or an injury to someone, lose text privileges for a period of time if homework is not complete, or lose the privilege of the car if an agreed upon curfew is broken.”

As parents we need to hang in there, keep our cool, and practice what we preach, says Weinstein. “Even though the changes in the teenage brain can be a strong contributor to behavioral and emotional disruption, parents are responsible to help their teenager gain better self-control,” says Weinstein. “How teenagers manage their own impulses, emotions, and behaviors later in life is strongly shaped by experience that occurs in adolescence.”