Jewish Life Digital Edition October 2015 | Page 20

TEENS

Some things just weren’t meant to
go together I By Shirra Moch

Early
exposure to
psychoactive
substances
has serious
consequences
for later
substance usage
and addiction.

When we’re very young, evidence of brain
development is easy to see. We learn to respond to familiar faces, express displeasure at uncomfortable stimuli, sit, crawl,
walk, talk, etc. Many laboratory studies
have illustrated the changes that take
place during this development, as well as
the influences that differing circumstances
can have on this process. Far less has been
written about the brain changes that occur
from adolescence through to young adult-

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hood, perhaps because these seem less apparent. In reality, brain development during this age-span is extremely active, with
recent research explaining why adolescents tend to exhibit poor decision-making
capacity and why substance abuse in this
age-group is particularly harmful.
Although the brain is about 95% of its
adult size by the age of six, it continues to
mature and develop throughout the teenage years, reaching a more defined struc-

ture by about age 24. The term most frequently used is ‘plasticity’ – the ability of
the brain to ‘mould’ itself into functioning
pathways through repeated activity and reinforced thoughts and actions. The circumstances, activities, and experiences to
which we are exposed in our adolescent
years ‘sculpt’ our brains, influencing our
eventual brain trajectory and potential.
While there are some genetic aspects to
this process, the majority is influenced by
our environment. For example, identical
twins develop non-identical brain pathways
which diverge principally from adolescence.
(If you are wondering how this research is
conducted, much of the current knowledge
of brain functionality comes from hi-tech
imaging studies which can reveal density
and activity of groups of neurones.)
Of all the brain structures that undergo
this modelling during adolescence, there are
four areas that can give us insight into ‘typical’ teenage behaviours and help us to understand their brain development: the amygdala, nucleus accumbens, cerebellum and prefrontal cortex. A word of caution here, however. While experts have suggested several
hypotheses for neurodevelopment and behaviour on the basis of neuroanatomical
findings in adolescence and brain plasticity,
the research is still in progress, and is considered suggestive rather than definitive.
The amygdala is a structure deep in the
brain that lays down memory and integrates emotional responses to both enjoyable and aversive experiences. It is the
amygdala that prompts initial reactions to
circumstances, and so in teenagers with incomplete amygdalar maturity, they may exhibit excessive volatility or explosive reactions in the face of non-threatening situations. In addition, amygdalar immaturity
has been implicated in the tendency for adolescents to misread neutral facial expressions as a sign of anger, prompting unnecessary defensive or aggressive responses.
The nucleus accumbens, which forms
part of the ‘reward’ circuit in the brain, initiates activities that will result in pleasure;

photograph: BIGSTOCKPHOTO.COM

The teenage brain
ON DRUGS