Adolescent Brain Development

Part 1

By Lori Hoisington

Family Impact SeminarApril 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 BrainThe 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.

Ventral Striatum

Prefrontal Cortex

Amygdala Cerebellum

Corpus Callosum

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-term-faculty/hoisington-lori-phd