Cerebral Transformation
Understanding adolescence: a fundamental shift
Do you believe—as many do—that any important
brain development is over by the time a child is 3? Evidence
points to a contrary reality, one that helps explain teenagers’
zigzagging pathways to adulthood. Groundbreaking scientific
work shows that the human brain dramatically transforms
itself over the adolescent years.
Aided
and stimulated by current technology that allows them to
view the workings of the living brain, neuroscientists around
the world have gathered evidence that extensive remodeling
and reorganization—over roughly a 10-year period—transitions
young people toward what we would call a stable maturity.
Barbara Strauch, who chronicles the ongoing scientists’
work in her book Primal Teen, calls the teenage brain “a
work in progress, a giant construction project. Millions
of connections are being hooked up; millions more are swept
away. Neurochemicals wash over the teenage brain giving
it a new paint job, a new look, a new chance at life. The
teenage brain is raw, vulnerable. It’s a brain that’s
still becoming what it will be.”
In her book Ms. Strauch reviews the work
of Dr. Jay Giedd, among others, who has been scanning and
rescanning the brains of hundreds of children and teenagers
over the past 10 years, at the National Institutes of Health.
He has documented thickening of the brain’s gray matter
(“tiny branches of brain cells bloom madly, a process
neuroscientists refer to as over-production, or exuberance”)
in early adolescence, followed ultimately by a dramatic
thinning down. During this period of “exuberance,”
the brain may be “highly receptive to new information,
or primed to acquire new skills, particularly those related
to basic survival.” Finding exuberance in the teenage
brain was the new development.
According to Ms. Strauch, Dr. Giedd found
growth in teenagers’ cerebral cortex (gray matter),
including the parietal lobes (associated with logic and
spatial reasoning); the temporal lobe (associated with language);
and, most importantly, the frontal lobes (the area that
helps us plan ahead, understand consequences, and resist
impulses). “The frontal lobes, the very area that
helps make teenagers do the right thing, are one of the
last areas of the brain to reach a stable, grown-up state,
perhaps not reaching full development and refinement until
well past age twenty.” All elements of the gray matter—
neurons, dendrites, synapses, are active in brain development
during adolescence, and the full picture includes neurochemicals
coursing through the brain, their receptors, as well as
new efficiency in connections between neurons.
Have you found yourself stunned, or incredulous,
at teenagers’ impulsive, often dangerous behavior,
or their clannish dress—or in contrast, at their precise
insights? The restructuring of the teenage brain involves
an extensive web of systems, affecting their logic, language,
impulses and intuition. It reflects a dynamic interaction
in which brain biology, genes and environment are role players.
These research advances have fundamentally changed our understanding
of what goes on during the adolescent years; we formerly
looked to genes and environment for the whole, if insufficient,
explanation of the course of development.
A key realization is that the prefrontal
cortex—home of the limiting, judging, reasoning functions
of the brain—is not yet developed and stable, nor
are the connections between that center and the impulse
or action center. During adolescence, and the restructuring
of the frontal lobes, cognition steadily grows: Teenagers
become capable of abstract thinking, complex reasoning,
planning, conceptualizing the self and social relationships.
The open-endedness of this process is both
ominous and fortuitous. In an interactive dynamic, behavior
and experiences shape the shifting structure of the brain
and the structure of the brain shapes behavior and experience.
Teenagers’ brains, as they remodel, are exposed and
vulnerable. At the same time, the desire to take risks and
experience new things is developmentally necessary. What
they choose to do may have profound effects, as may elements
in their environment. There is evidence, for instance, that
the effects of alcohol and nicotine, or lack of sleep, on
teenage brains can have far more complex and damaging effects
than on adult brains. The silver lining is that adults can
help stimulate the foresight not yet available to teenagers,
or help with the effects of big mistakes, emotional difficulties,
or negative patterns, and shift the development of the brain
as it reaches for maturity and stability.
Ms. Strauch quotes neuroscientist Deborah
Yurgelun-Todd at McLean Hospital in Belmont, Massachusetts,
as saying, “Adolescent behavior is a necessary, built-in,
and temporary phenomenon,” awe-inspiring in its complexity.
Cultures for all time have recognized, in various ways and
with diverse ritual, this developmental transition.
Upperclass students at Milton are quite
aware of the journeys they have made thus far. Individually
and collectively they verify the touch points Barbara Strauch
describes in her book. Many of them welcomed the opportunity
to share (on the following pages) the experiences that figured
powerfully in shaping the self they now bring to the next
phase of their lives.
Cathleen Everett
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