Adolescent Brain
Development
Part 1
By Lori Hoisington
Family Impact Seminar
April 7, 2015
The goal of this presentation is to help you become a more
informed consumer of neuroscience research
The Brain the way we
see it with MRI
Basic components of the
brain include gray matter,
white matter, meninges
and cerebral spinal fluid.
Gray and white matter
The Neuron
Gray matter includes
cell bodies of neurons
along with fibers that
extend from them.
Communication
between neurons
occurs through
synapses (relays).
Use it or lose it
• As the brain develops, synapses that are “exercised” by
experience are strengthened, and synapses that are not
used are pruned.
Laboratory for Rehabilitation Neuroscience (DTI) University of Florida (2015)
The adolescent brain
• Gray matter volume is highest in early adolescence. This
is largely due to overproduction of synapses.
• Different parts of the cerebral cortex mature at different
rates
• Areas of the brain that control senses and movement
mature first
• Areas of the brain that control executive function (impulses,
planning ahead) mature last
• Development continues through the early-to-mid
twenties (including abilities for reasoning and judgment)
Myelination
• Fatty substance that coats the axons of nerve cells
• Occurs in the most primitive areas of the brain first, and the
frontal lobes last
• Increases the speed that signal transmits between neurons
(up to 100x)
Prefrontal Cortex
• The prefrontal cortex in adolescents is not fully
myelinated
• This area is responsible for executive function
• Incomplete myelination in the prefrontal cortex might
explain why adolescents are sometime impulsive and
unable to inhibit inappropriate behavior
• Excess synapses combined with incomplete myelination
may lead to inappropriate behavior and difficulty with
reasoning
Adolescent vs. adult brain
• The adolescent brain is less developed compared to
the adult brain. Adolescents process information
differently.
• Not as capable of understanding and processing mistakes or
learning from experience
• Reduced ability to engage in logical reasoning, control
impulses or accurately interpret reactions of others
• More susceptible to peer pressure and other environmental
influences
• Higher risk for reckless and sensation-seeking behavior
• More likely to become involved in criminal activity
The Adolescent Brain
The prefrontal cortex (“executive brain”) continues to develop
through early adulthood. Until then, other parts of the brain compete
for control of responses to sensory input. This often leads to
undesirable behavior and consequences for adolescents.
Prefrontal
Cortex
Corpus
Callosum
Ventral Striatum
Amygdala
Cerebellum
The reward system and risk taking
• The adolescent brain reflects competition between the
reward system vs. the cognitive system
• Reward system activates more rapidly
• Cognitive system continues to develop into the early to mid
twenties
• The presence of peers doubles the number of risks
teenagers take, but there is no impact in adult behavior
(Steinberg, The Daily Circuit)
Adolescent emotions
• The emotional center (amygdala) matures before the
cognitive center (frontal lobes) in the adolescent
• This may explain why adolescents respond more
emotionally to situations compared to adults
• Adult responses are more intellectual, while adolescent
responses are more reactive
Processing emotions
When processing emotions, adolescents rely more on the
Amygdala (left) while adults rely more on the frontal cortex (right)
Frontline” Inside the Teenage Brain (2002)
Dopamine
• Dopamine is a naturally-occurring substance in the
human brain
• It is necessary for focusing attention – even more so when
an individual is presented with conflicting options
• Without sufficient dopamine, it is difficult for adolescents
to reflect on available options and they often act on
impulse
• In early adolescence, dopamine levels in the frontal lobes
are low
• Dopamine levels in the frontal lobes increase throughout
adolescence
Question
• Do privileges afforded to youth match youth
competencies according to brain science?
• Youth Competency is a measure of whether youth can
contextualize their actions
• Competency is an assumed requirement in order for youth
to change the course of their behavior
Problem
• Historically, an estimated 364 juvenile offenders have
been executed in the U.S.
• Execution of juvenile offenders was ruled
unconstitutional in 2005 (Roper vs. Simmons)
• Numerous juvenile offenders still reside on Death Row
• Over 2500 juvenile offenders have been sentenced to
LWOP
• Sentencing practices are under examination to
determine the fate of these individuals
Landmark decisions
• Roper v Simmons (2005) abolished the death
penalty for juvenile offenders under 18
• Graham v Florida (2010) - juvenile offenders cannot
be sentenced to mandatory life without parole for
non-homicide offenses.
• Miller v Alabama and Jackson v Hobbs (2012) - high
court - a state cannot impose a life-without-parole
sentence for juvenile homicide offenders on a
mandatory basis.
• MI, MN, PA, LA have not applied the decision retroactively
Moving forward
• Developmental science should inform the way we
manage juvenile offenders
• Criminal culpability
• Competence to stand trial
• Consequences of punitive sanctions on adolescent
development and behavior
• Restorative justice
• Assumes culpability and focuses on restitution and
citizenship
• Juvenile offenders should not be managed the same as
adults in the criminal justice system
Thank You!
Contact Information
hoising1@hdfs.msu.edu
(517) 749-4233
http://hdfs.msu.edu/people/specialists-and-fixed-termfaculty/hoisington-lori-phd