The Brain + Neurochemistry in Adolescence

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Understanding the Role of the Brain and Neurochemistry

During adolescence, our minds change in the way we remember, think, reason, focus attention, make decision and relate to others. From around age 10 to 24, there is a burst of growth and maturation taking place as never before in our lives. Getting a handle on the brain and what happens during adolescence provides an understanding of the behaviours that characterise this period of development.

During adolescence the brain undertakes two crucial processes - Myelination & Pruning.

Pruning is the process by which unnecessary neurons and synapses (grey matter) in the frontal lobe are eliminated. During childhood there is an over production of neurons and their synaptic connections and then during adolescence, as we learn and develop skills, the brain starts to ‘prune’ back on these, the ones we don’t seem to need anymore.

Myelination is happening at the same time. This is the process in which white matter envelopes connections to stabilise them, keeping the ones we have been using. This conversion of grey to white matter is critical to the brains operation becoming more efficient and the development of neural networks that regulate behaviour.

In fact, during this time there is a significant decline in the pre-frontal cortex, so maybe young people really are “losing their minds” after all! The more you use a circuit, the stronger it gets. The less you use a circuit, the more likely it may get pruned away during adolescence. These two fundamental changes – pruning and myelination – help the adolescent brain become more integrated – fine tune itself. Integration, the linking of different parts, creates more coordination in the brain itself.

What parts of the brain are most significant in adolescent development?

The pre-frontal cortex – executive functions

This is the brain region most closely associated with the executive functions and the regulation of behaviour. The pre-frontal cortex is restructured in the teenage years but is not fully developed until the early to mid-twenties. The brains executive functions enable people to:

Focus, organise and prioritise
Link actions to logical consequences
Control impulses, regulate emotions and moderate behaviour
Balancing short term rewards with long-term goals (motivation)

Ventral Striatum – reward-based decision-making

This is the reward centre in the brain where most of the adolescent functioning takes place. Linked to the Limbic System, it is where decisions are made based on rewards and emotions without the back-up of the cognitive strength of the pre-frontal cortex. The ventral striatum plays a major role in reward-motivated behaviour and is closely associated with the tendency of young people to engage more than adults in sensation seeking and risk taking behaviour that is often viewed as impulsive and instinctive.

The corpus callosum - integrating logic and creativity

Connecting the brains left and right hemispheres, the corpus callosum, carries traffic essential to many advanced brain functions. During adolescence it steadily thickens and stronger links also develop between the hippocampus (a sort of memory directory) and frontal areas that set goals and weigh different agendas. As this develops young people get better at integrating the two hemispheres, memory and experience into decisions and become more self-aware. Like the pre-frontal cortex, it reaches full maturity in the mid-twenties.

How can neuroscience help explain some of these common adolescent traits?

Young people are still learning to use their brain’s new networks. This is similar to the physical awkwardness teens sometimes display while mastering their growing bodies. Their brain is primed optimally for experiential learning but it takes time.

There are some common adolescent traits that can be understood through changes in the brain. These are sensation seeking and risk taking, a preference for the company of others and a concern about capacity.

Sensation-seeking and Risk-taking

Young people tend to hunt out experiences that are thrilling and novel. They are often attracted to the unusual and/or unexpected. This is known as seeking sensation. Again, from an evolutionary standpoint this makes sense. A love of novelty can lead directly to useful experiences that can broaden the horizons of a young person. Sensation-seeking experiences can be on impulse or planned. Impulsive sensation-seeking tends to gradually diminish after the age of 15.

Closely associated with sensation seeking is risk taking, which also peaks during adolescence.

While adults focus on the potential hazard associated with risk taking, young people tend to focus on the potential rewards. Therefore contrary to popular belief, young people’s tendency for risk taking has nothing to do with being stupid or irrational.

The Drive for Reward

There are many ways to understand how young people are ‘rewarded’ but from a neurological perceptive the neurotransmitter dopamine has the key role.

During adolescence there is an increase in the activity of the neural circuits utilizing dopamine, central in creating our drive for reward.

The brains increased drive for reward in adolescence manifests in young people’s lives in three important ways:

Increased impulsiveness, where behaviours occur without thoughtful reflection.
Increases susceptibility to addiction due to enhanced dopamine response
Hyper rationality – young people examine just the facts and miss the context or big picture

Starting in early adolescence and peaking midway through, this enhanced dopamine release causes adolescents to gravitate toward thrilling experiences and exhilarating sensations. It has even been suggested that the baseline level of dopamine is lower during adolescence but its release in response to experiences is higher – this can explain why young people may report feeling “bored” unless they are engaging in something stimulating and novel.

The sensitivity to dopamine helps explain why young people are so quick in learning and are especially receptive to rewards. This often will lead young people focusing solely on the positive rewards that they know are in store for them, while failing to give value to the potential risks and downsides.

Adolescents are often fully aware of the risks and even at times overestimate the chance of something bad happening, but simply put more weight on the benefits/rewards of their actions. Young people may take more chances than adults but they:

Recognise risk just as well
Use the same basic cognitive strategies
Fully recognise they are mortal
Usually reason their way through problems just as well
Tend to overestimate risk

So, it is not that adolescents take more risks because they don’t understand the danger but because they weigh risk vs reward differently to adults. In situations where risk can get them something they want, they value the reward more heavily than adults do.

A preference for the company of other young people

The neural networks and dynamics associated with general reward and social interactions overlap heavily. The adolescent brain is similarly attuned to oxytocin (a neural hormone) that makes connecting with others more rewarding.

Peers of a similar age offer young people far more novelty than those who are familiar and most other adults. This is great when the relationships are supportive however if young people are only surrounded by other teens that have increased risk behaviours and no positive adults in their lives their risk is increased.

Sarah Jayne-Blakemore, a leading social neuroscientist of adolescent development, explores the effects that peers have on adolescent decision-making. She suggests that while it is well known that young people take a disproportionate number of risks, if you give them an optimal situation and environment this is not necessarily the case. In fact, the influence of having some motivational context such as the presence of a couple of friends around, heightens the risk-taking by young people. This is reflected in our understanding about car accidents involving young people and that they usually occur when they have a peer in the car with them.

Similarly, when adolescents are excluded by peers, their mood drops and anxiety increases more than adults. This suggested hypersensitivity to exclusion will obviously impact on decision making for young people.

Concern about capacity

Some of the revelations from neuroscience have led to concern being expressed over whether young people lack the judgement to make decisions about potentially harmful behaviours such as substance use. However, we need to be careful about overprotecting young people as

“Some young people are sometimes at risk, not because brains are different but because they have not had experience or opportunity to develop skills and judgement that engagement in those activities and experiences supply” – Judith Bessant (2008)

It seems that it is imperative to create conditions in which young people can seek sensations and take risk in a constructive way, where the extreme risks are minimized. This points to a form of guided experience that acknowledges the reality that young people are biologically set up to seek sensations and take risks; even if it makes some of the adults in their lives uncomfortable.

Increased Emotional Intensity

Emotions rather than reason rule the brain of a young person. During adolescence the lower brain areas below your cortex are more active – which means emotions can arise rapidly and intensely without the frontal lobe saying “hang on a minute, this may not be such a good idea”. For young people, information sent to the amygdala bypasses the higher cortex via the fast route meaning that the intense emotions of a pure amygdala response are felt without filtering by cortical reasoning. Reflection is not a strong feature of a young person’s brain and when heated, these skills disappear completely.

Therefore, when you are caring for a young person in an intense mood, whether it be anger, jealousy, sadness, hostility, happiness or worry, it is useful to know that the full repertoire of behaviours are not accessible to them. Therefore, when they are in a powerfully negative mood they don’t have much chance of seeing your perspective and being convinced. These moods usually have nothing to do with their day, what you may have done or even something they understand but rather to do with all the chemical in the brains and bodies.

Adolescent Development