Discuss the brain development that occurs during adolescence in point form
As we have mentioned in Chapter 3, scientific advances in especially neuroimaging
over the past few decades have contributed to a much greater understanding of the growth
of the human brain from before birth to adulthood. Until quite recently, there had been a
general assumption in developmental psychology and neuroscience that major changes
in the architecture and functioning of the brain were limited to the prenatal period and
the first five or six years of life. However, neuroimaging has revealed that brain structure
develops until early adulthood (about 25 to 30 years of age) (American Academy of Child
and Adolescent Psychiatry, 2021; Dumontheil, 2016).
6.2.2.1 Structural and functional changes in the brain during
adolescence
During adolescence, the brain undergoes significant maturational processes in both
structure and function. These developments change the way in which adolescents think
and process information, as well as how they interact with others. These changes involve
the following (see Chapter 3 for the explanation of concepts; also see; Braams et al., 2015;
Hauser, 2021; Konrad, 2013; Santrock, 2019; Steinberg, 2011, 2020):
During adolescence, the brain is 'remodelled' through two processes: synaptic
pruning and continued myelination in certain brain regions. These processes are
important for sophisticated thinking abilities and increased connectivity between brain
regions. For example, the corpus callosum thickens in adolescence and improves
adolescents' ability to process information.
Because the brain does not mature at the same rate in all its regions (for example,
as we have seen with young children, the motor and sensory regions develop before the
higher-level executive functions do), this has profound effects on adolescents' functioning.
For example, the limbic system matures early in adolescence, while the frontal
lobes (or prefrontal cortex) (see Figure 6.1 for the position of these structures in the
brain), which control impulses, planning, higher-order thinking, and engaging in longer�term perspectives, mature only in later adolescence and early adulthood (at about 25
to 30 years). Therefore, although adolescents are capable of very strong emotions, the
prefrontal cortex has not developed adequately to control these passions. This may explain
why younger adolescents may take more risks than older adolescents and adults do. This
coincides with the fact that the frontal regions are the last to become myelinated. Some
authors explain this difference in the rate of brain maturation as starting the engines with
an unskilled driver while the braking systems are not working properly yet.
In addition, certain neurotransmitters such as dopamine and serotonin, and
changes partly caused by puberty, make adolescents more emotional, more responsive to 6.2.2.2 Biology, experience, and plasticity: Influences on brain
development in adolescence
A topic of controversy involves which comes first — biological changes in the brain
or experiences that stimulate these changes. It seems that this nature-nurture issue
is difficult to tease apart. For example, does the prefrontal cortex thicken because
adolescents can resist peer pressure, or can adolescents resist peer pressure because
the prefrontal cortex thickens?
Neuroscientific research is integral to improving our understanding of the brain
developments that take place during this time and how these transformations are
influenced by interactions between the evolving adolescent brain and the environment in
which it develops (UNICEF, 2017).
Researchers have known for some time that the brain is particularly malleable or
plastic during the first three years of life. This means that the brain has the capacity to
change in response to environmental experiences. In other words, the developing brain
is influenced both by passive exposure (experiences of which we are not even aware) and
active experiences (such as learning). A fairly recent discovery is that a second period of
plasticity occurs in adolescence (Fuhrmann et al., 2015). Therefore, extensive remodelling
of the brain's circuitry occurs while the brain is still maturing. Because the brain is so much
more malleable during this time, it can be affected in potentially permanent ways, by every
experience, whether positive or negative. For example, plasticity allows adolescents to
learn from experience and adapt to the environment, while the continuing development of the prefrontal cortex allows adolescents to benefit considerably from education (Dahl et
al., 2018). No wonder Steinberg (2020, p. 53) calls adolescence an "age of opportunity".
However, this malleability poses some risks as well: during this time of heightened
sensitivity, the brain is also more vulnerable to damage from physical harms such as drugs
(including nicotine and alcohol) and injuries, or psychological harms, such as trauma and
stress. Damage done during this time may even be permanent, or cause trouble into
adulthood. (See also Box 6.1 on the effects of contact sports on the adolescent brain.)6.2.2.3 The influence of gender on brain development
Sometimes, it is claimed in the media that important differences exist between the
brains of adolescent boys and girls (and, for that matter, also between adult men and women). Steinberg (2020) provides a summary of existing research: Studies indicate
that differences between the genders in brain structure and function are very small
and unlikely to explain differences between males and females in the way they behave
or think. Furthermore, there are few consistent gender differences in the size of specific
brain regions or structures — some parts of the brain are slightly larger in females, and
some are slightly larger in males. In general, however, the similarities between males and
females in brain structure and function — before, during, and after adolescence — are far
more striking than the differences. Researchers have looked specifically for connections
between adolescent hormone and brain development because male and female brains
are exposed to different levels of sex hormones. It is clear that structures in the brain
are changed by exposure to sex hormones. However, the ways in which the brains of
adolescent boys and girls differ because of sex hormones, as well as the possible effect of
these differences on their behaviour or cognition are still not well understood.
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Brain Development During Adolescence: Key Points
Structural Changes
Synaptic Pruning: The brain eliminates unnecessary synapses, enhancing efficiency in neural connections.
Myelination: Increased myelination occurs in certain brain areas, improving the speed and efficiency of neural communication.
Thickening of the Corpus Callosum: Facilitates better communication between the left and right hemispheres, enhancing information processing capacity.
Maturation of Brain Regions
Limbic System Development: Matures early in adolescence, leading to heightened emotional responses and risk-taking behavior.
Delayed Prefrontal Cortex Maturation: The prefrontal cortex, responsible for impulse control, planning, and decision-making, matures later (around 25-30 years), contributing to impulsive behavior in adolescents.
Neurotransmitter Changes
Dopamine and Serotonin: Increased levels result in greater emotional intensity and motivation, influencing behavior and social interactions.
Plasticity and Experience
Adolescent Plasticity: The brain remains highly malleable, allowing significant changes in response to experiences, both positive and negative.
Critical Learning Phase: This period of plasticity enables adolescents to learn effectively and adapt to their environment, but also increases vulnerability to negative experiences (e.g., trauma, substance abuse).
Nature vs. Nurture Debate
Biological vs. Environmental Influence: Ongoing discussions about whether brain changes drive behavioral adaptations or vice versa, indicating a complex interplay between biology and experience.
Gender Differences
Minimal Structural Differences: Research shows that differences in brain structure and function between adolescent boys and girls are minor, with more similarities than differences.
Effect of Sex Hormones: Exposure to different levels of sex hormones influences brain development, but the implications for behavior and cognition remain poorly understood.
Risks Associated with Developmental Changes
Heightened Sensitivity: Increased malleability of the adolescent brain makes it more susceptible to physical and psychological harm.
Long-term Consequences: Negative impacts during adolescence may lead to lasting difficulties into adulthood, underscoring the importance of positive experiences during this critical period.
These points summarize the significant processes that characterize brain development during adolescence, highlighting the complex interplay between structural changes, maturation, environmental influences, and potential risks.
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