THE ADOLESCENT NEURODEVELOPMENT – A WORK IN PROGRESS

INTRODUCTION

The process of adolescence is not synonymous with puberty. Adolescence includes the entire transition from childhood to adulthood; puberty is a more discrete phase during which the physiological and neuroendocrine alterations associated with sexual maturation occur. Puberty is only one of the ontogenetic alterations occurring during adolescence, with the timing of this phase within the broader framework of adolescence varying notably among human adolescents [1].

In humans, adolescence is commonly defined as the second decade of life, with ages up to 25 years considered late adolescence by some researchers [2,3].

Adolescence is a stage of life that must be cultivated carefully, brain changes in adolescence are vital transformations in development, allowing the formation of new skills. It is partly genetic information that we inherited and partly experiences of life in which we are involved. How we navigate the adolescent years has a direct impact on how we’ll live the rest of our lives.

The conventional wisdom had been that the adolescent brain is fully developed and functions similarly to an adult brain, but in fact, the brain doesn’t look like that of an adult until between ages twenty to twenty five. The more recent researches revealed that the high point of the volume of gray matter occurs during early adolescence.

Due to the transformations that taking place in the integrative areas of the frontal cortex during this period, the adolescents are becoming more aware of themselves and see life in conceptual and abstract ways. They begin to consciously and creatively explore deeper the meanings of life, of friendship, of family, of all things, the ability to reflect on their personality is formed now.

THE CHANGING BRAIN AND BEHAVIOUR IN TEENS

Much of what we now know about the adolescent brain is still developing. Brain development is a mix of expansion and regression, the adolescent brain is a brain in flux [4,5].

Basic science studies have revealed evidence for 4–5 times higher rates of formation of new neurons during adolescence than in adulthood. The teen’s life is shaped by factors such as family, friends, school, and community institutions, but there are also powerful neurological issues at play.

It is well known that two major changes in brain structure occur during adolescence:

1. The „pruning” of neurons (the brain’s basic cells) and their connections (synapses), which is the removal of previously laid down connections among neurons and even some neurons themselves, leaving behind the neural circuits the individual needs most.

Pruning during adolescence is highly specific and can be pronounced, resulting in a loss of approximately 50% of the synaptic connections in some regions, but with little decline in others [6]. Synapses „exercised” by experience survive and are strengthened, while others are pruned away.

2. Myelin formation. The processes of myelination and synaptic pruning help to reconfigure the brain into an adult form.

The most of the new insights into the adolescent brain have been gained using the brain-imaging techniques. Due to neuroimagistic, in some [7] studies, adolescents were found to exhibit greater amygdala activation to emotional faces than adults (and children, when studied), with data supporting.

The cognitive and behavioral functions of the prefrontal cortex: organization of multiple tasks; impulse inhibition; self control; setting goals and priorities; empathizing with others; initiating appropriate behavior; forming strategies; planning ahead; adjusting behavior when situation changes; stopping an activity upon completion; insight.

Research using many different approaches is showing that in adolescence take place the following transformations [8,9]:

the thinning of cortical “gray matter” is followed by increases in myelinated “white matter”.
the connections between different parts of the brain increase throughout childhood and well into adulthood.
the responses of teens to emotionally loaded images and situations are heightened relative to younger children and adults.
reproductive hormones shape not only sex-related growth and behavior, but overall social behavior. Hormone systems involved in the brain’s response to stress are also changing during the teens.
the capacity of a person to learn will never be greater than during adolescence
the parts of the brain involved in emotional responses are fully online, or even more active than in adults, while the parts of the brain involved in keeping emotional, impulsive responses in check are still reaching maturity.
amplifies the activity of neural circuits that use dopamine, the main neurotransmitter which plays an important role in the often reckless, sensation seeking behavior of adolescents.

THE ROLE OF DOPAMINE

The dopamine is released by something new. Nature likely has created this change in the reward system so that the teen as an individual is driven to try something new which means he will get away from his familiar, safe, comfortable home to mix it up with other members of species far away from family members.

Early in adolescent development levels are relatively low which may account for their reactive behavior. The good news is that dopamine inputs to the prefrontal cortex grow dramatically as the teen ages, resulting in an increased capacity for more mature judgment and impulse control. But until this system is mature, decisions are often made on impulse.

Teenagers show, simply, faster response, unfiltered by cortical judgment.

Studies suggest in fact, that the basic level of dopamine is low, but its secretion in response to experience is higher – which explains why teenagers claim to be bored unless they are not engaged in something new and stimulating.

The impulse of search satisfaction amplified in adolescence, manifests in adolescent’s life in three main ways:

• increased impulsivity, when the behavior occurs without prior reflection and impulses urges immediate action.
• greater predisposition to addiction. Studies show that high glycemic index foods, processed foods and even simple carbohydrates such as potatoes or bread, leading to a rapid rise in blood sugar and lead to a rapid increase in dopamine levels and activity of brain circuits satisfaction.

Some studies suggest that persons exposed to risk, especially during adolescence, ie ingesting of a specific substance activates a gene which is part of the motivational circuits in the brain. Once the gene is turned on, the dopamine circuit is set on a certain „chosen substance”. Alcohol, cocaine, amphetamines, barbiturates and heroin can turn all that circuit [10,11].

Studies argue that a sudden increase of dopamine is caused not only when we consume the substance, but when we plan to consume or when we think of it, when we are around people that have taken the substance, in a room that resembles with one in which we used it etc. This is the cycle of addiction.

• hiperrationality: how the teenager thinks in literal, concrete way. He examines only the surface details of a situation and doesn’t see the whole picture, neglects the circumstances or context in which theevents take place. Teenagers who think literally gives more importance for calculated benefits of an action than its potential risks. Assessment centers of the brain mitigate the negative meaning, while amplify the positive result of a situation. Research suggests that adolescence brings with it brain-based changes in the regulation of sleep that may contribute to teens’ tendency to stay up late at night. Along with the obvious effects of sleep deprivation, such as fatigue and difficulty maintaining attention, inadequate sleep is a powerful contributor to irritability and depression. Studies of children and adolescents have found that sleep deprivation can increase impulsive behavior; some researchers report finding that it is a factor in delinquency.

Sleep researcher, Mary Carskadon from Brown University’s Bradley Hospital, has discovered that teenagers need more sleep than they did as children and that their circadian rhythms appear to be set later than those of children or adults [10].

Carskadon has shown that teens, far from needing less sleep than they did as children, need more. In order to function well and remain alert during the day, they need 9 hours and 15 minutes, possibly because the hormones that are critical to growth and sexual maturation are released mostly during sleep.

A second finding from Carskadon’s research is that these teens’ biological clocks appear to be set later than those of children or adults. Most teenagers’ brains aren’t ready to wake up until 8 or 9 in the morning, well past the time when the first bells has sounded at most high schools. Teens who have to get up before their internal clock buzzes, miss out on an important phase of REM sleep that is important for memory and learning. The most visibly dramatic aspects of adolescence relate to the hormonally mediated changes of adolescence.

Much researches have examined the question of the developmental impact on adjustment of early versus late maturation in boys and girls [12,13].

For boys, early maturation is advantageous in terms of popularity, self-esteem and intellectual abilities, but does confer some increased risk for delinquent or problem behaviours [13].

For girls, the picture is more complex, with early maturing girls, tending to have more difficulties (including lower self-image and greater vulnerability to depression, anxiety and eating disorders), to engage in more risky behaviors, and to experience early sexual intercourse [13].

MYTHS ABOUT ADOLESCENCE

Our modern culture encourages deeply pervasive myths about adolescence. For example we hear all the time that teens are driven mad by “raging hormones,” that they are “just immature and need to grow up.”All of them are misconceptions that not only imprison how we as adults see adolescents, but also influence how adolescents themselves behave.

Dr. Dan Siegel, one of the most appreciated specialists in relational health, psychoterapist and a passionate researcher of the human brain in his book

“Brainstorm: The power and purpose of the teenage brain” tries to debunk these myths [14].

• Myth no.1: Adolescence is a period of immaturity.

Truth: Adolescence is a period of transformation in which brain is remodeling. Testing limits, passion to explore the unknown and the mysteries specific of this periode claims D.Siegel can pave the way for development of character traits that will allow adolescents to live adventurous and fulfilling lives. Giving up to label „immature”, the sooner the adolescent has the chance to discover his capabilities, skills and intellectual level. The teenager has the right to express his own point of view regarding the decisions of the family, his ideas have taken into account.

• Myth no.2: Hormones are making teenagers to react in an uncontrolled manner.

Truth: Recent studies show that changes in the structure and functioning of the brain are primarily responsible for the changes in thinking, emotions and behavior of adolescents. Studies suggest that in adolescence risky behaviors are less related to any hormonal imbalance and more related to obtain pleasure by releasing dopamine. Enhanced dopamine release directs us to reward and satisfaction, in the sense that our attention is directed to the arguments for, so we expose to the risk and diminish the importance of counter arguments during these years.

• Myth no.3: To grow up requires the transition from total dependence to adult independence.

Truth: healthy transition to adulthood is through interdependence, not by isolation from. It is true that friends are more important in this period, but teens still need the support of parents. Teens need to be away from their parents to be prepared to leave home and, at the same time they need in their lives other adults they can trust.

• Myth no.4: Teenagers make dangerous things because they are impulsive or uninformed.

Truth: changes in brain creates so called „hyperrational thinking” where teens choose to do risky things, without thinking too much about the possible dangers.

• Myth no. 5: Teens hate their family.

Truth: reactions to reject the family members are caused by the need of adolescents to have their own identity, to and delineate private space and personality, and in addition, the teenager can now realize and even to criticize the mistakes of their fathers. Studies show that teens who talk to their parents about their problems in this period will be more adapted to life later.

• Myth no. 6: Teenagers pass easier over problems.

Truth: It is said that teenagers pass more easily over the problems and difficult situations in life than adults. While adult has psychic structure needed to cope with any situation, the teenager hasn’t all the tools to adapt to the social environment and life.

CONCLUSIONS

Adolescence is a period of ups and downs which is characterized by: creative exploration, emotional intensity, looking for new things and create new friendships. Each of these four characteristics mentioned are given by the changes that occur in the brain and both presents risks and opportunities.

As parents and teachers, we have an opportunity and an obligation to educate adolescents about what is going on in their brains and the role they play determining the structure and functioning of their brains for the rest of their lives. At the same time, we can learn to communicate with and support adolescence, to understand them when they are irritable, when their moods can be very labile, emotions can come and go really fast and the overall mood cannot be within as you would expect.

As MD Siegel says: „Actually teach the adolescence what emotions are and how to ride the wave of their emotions. We need to teach adolescents to ride the wave, to surf those waves. I mean they learn that skill; it’s a scale of emotional intelligence, which is very useful throughout their life span.”

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