WELLBEING
Where monsters roam
Andrzej Fanner Brzezina (Year 13) uncovers the development of the teenage brain and its impact on adolescent behaviour
I ndividual experience and public perception tells us that our emotions and behaviour patterns change during our teenage years as we progress from childhood to adult maturity. Equally, it is a long and widespread belief that these changes are due to hormonal fluctuations and environmental pressures. This explanation is partly true but far from the whole story. With the development of new techniques for investigating the brain, like functional magnetic resonance imaging (fMRI) and an increasing understanding of neuroscience, it is becoming clear that adolescence is a period of profound change in the complex biochemical circuitry in the brain. Despite this, there is still so much more to discover – this makes studying the brain, and particularly the teenage brain, so fascinating. In his article ‘The Strange Anatomy of the Brain’ for the New Scientist , David Bainbridge likened our current understanding of the brain to ‘a medieval map with the known world encircled by terra incognito where monsters roam’. Come and discover the adolescent brain if you dare – but beware of the potential monsters… Plasticity and critical periods in the teenage brain O ur teenage years are a period of great neurodevelopment in the brain. Adolescence is a time when our brains are most susceptible to change caused by the external environment. Scientists call this property ‘plasticity’. During a child’s life, there occur particular periods of heightened plasticity called critical periods, which may last months or years. Most happen in infancy, but some arrive as late as our teenage years. Between the ages of ten and twelve, there is a thick overgrowth of branch-like
structures at the end of neurons (elongated cells in the brain, which perform a similar function to wires by carrying electrical impulses). We call these structures dendrites. Where dendrites from different neurons meet, there is a microscopic gap called a synapse that cannot be crossed by a nerve impulse travelling along the neuron. Instead, the gap is bridged by a chemical messenger called a neurotransmitter (more on them later). Therefore, just before adolescence, we have far more synapses or ‘connections’ in our brain than we will need as adults. During the critical periods of adolescence, the dendrites are pruned according to which neural pathways are stimulated or ‘used’. The connections that the brain does not need just fall away. Obviously then, it is important during adolescence that the ‘right’ connections are maintained and strengthened. As Aristotle presciently observed more than 2,000 years ago, ‘The habits we form from childhood make no small difference, but rather they make all the difference’. Sleep (or reasons why school should start later in the morning) C ircadian rhythms are the patterns of waking and sleeping (and other physiological processes) that rule the body clock of all animals. By nine or ten years of age, a child has reached the adult human pattern of requiring, on average, eight hours of sleep within a 24-hour cycle. But as is the case with most other features of adolescence, everything goes haywire when puberty is reached. Now, a teenager requires just over nine hours of sleep a night. To compound matters, the chemical secreted by the brain that induces drowsiness (melatonin) is produced later in the evening – at about the same time as for adults (eleven o’clock).
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