ADOLESCENT BRAIN DEVELOPMENT

ADOLESCENT BRAIN DEVELOPMENT
“TIME OF TURMOIL AND TRIUMPH” BARBARA SULLIVAN, Ph.D. September 14 and 15, 2009

GOALS To increase participant understanding of:
the structures, functions, and stages of development of the brain how adolescence has changed over the last 150 years the differences between adult and adolescent thinking the impact of abuse and neglect on the brain current trends in adolescent alcohol use the impact of alcohol use on the brain what clinicians, prevention specialists, and communities can do to support healthy adolescent development

CAVEATS New discoveries — research is still in its infancy
Do NOT over-interpret or interpret too simplistically Research is not to the point that it can inform causal models Most research has been conducted on male animals — we assume the information transfers to people Behavior is the result of complex interactions among individual, environment, genetics, situation, cultural expectations, and numerous other factors

BRAIN STRUCTURES AND FUNCTIONS

BRAIN FACTS Brain weighs approximately 3 pounds
Brain has approximately 100 billion neurons and 1 trillion supporting cells Neurons grow and organize themselves into efficient systems that operate a lifetime Brain controls ALL activities Emotion and cognition are intertwined Neurons can re-route circuits Brain and environment involved in delicate duet Brain never stops adapting and changing

Illustration by Lydia Kibuik, 2003

EVOLUTION OF THE NEW BRAIN
Slide 2–11 Drawings of the evolution of the primitive and new brains. Although the new brain is much larger in human beings, the primitive brain is where basic cravings exist. These cravings can overpower the reasoning and common sense of the neocortex (the new brain). (pp. 48–49) Every mammal’s brain has the same basic structure- cortex, cerebellum, and brain stem– cortical surface area is key

CHALLENGE OF UNDERSTANDING THE BRAIN
What is the link between the anatomy of a brain and the workings of the mind—our thoughts, emotions, memories, and behaviors? There are no moving parts—it does not operate mechanically as our hearts, legs, hands, and lungs do. So what is going on in there?

BRAIN STRUCTURES Frontal Lobe Parietal Lobe Temporal Lobe
Occipital Lobe Cerebellum Corpus Callosum Brain Stem

INTEGRATION OF THE LOBES
The different lobes of the brain work together– like instruments in an orchestra to play music or letters in the alphabet to form words Each area makes specialized contributions to certain functions, but many brain regions participate in forming human thoughts and behaviors

FRONTAL LOBE Seat of personality, judgment, reasoning, problem solving, and rational decision making Provides for logic, understanding of consequences, and emotional/behavioral regulation Governs impulsivity, aggression, ability to organize thoughts, and plan for the future Controls capacity for abstraction, attention, cognitive flexibility, and goal persistence Undergoes significant changes during adolescence — not fully developed until mid 20’s (Geidd, 2002)

FRONTAL LOBE As the “prefrontal cortex” area of the frontal lobe matures, through experience and practice, teens can reason better, develop more impulse control, and make better judgments Prefrontal cortex is one of the last areas of the brain to fully develop (Sowell, 2001) Increased need for structure, mentoring, guidance

COMPONENTS OF EXECUTIVE FUNCTIONS AND SAMPLE BEHAVIORS
Goal Directedness Establishing and maintaining goals; evaluating progress, using strategies Initiation/Inhibition Initiating behavior independently, self-cueing, inhibiting inappropriate behaviors Flexibility/Perseverance Generating novel possibilities, flexibility, performing contingency based revisions, strategizing

COMPONENTS BEHAVIORS Abstract Reasoning
Using rule-guided thinking, forming concepts, using hierarchical and temporal relationships Reward Appraisal Evaluating reward likelihood, using reward appraisal to guide behavior Social Appraisal Understanding social norms and cues, incorporating social information into decision making Brown et al., 2008

TEMPORAL LOBES Responsible for hearing, understanding speech, and forming an integrated sense of self Responsible for sorting new information and for short term memory Contains the limbic-reward system (amygdala, hippocampus, nucleus acumbens, and vta) Developmental delays, deficits, or over-stimulation of the limbic area may increase vulnerability to high risk behaviors (Clark, Thatcher, & Tapert, 2008) Matures around ages 18-22

TEMPORAL LOBE/LIMBIC SYSTEM
Limbic system regulates emotions and motivations— particularly those related to survival—such as fear, anger, and pleasure (sex and eating) Feelings of pleasure/reward are very powerful and self-sustaining. Pleasurable behaviors activate a circuit of specialized nerve cells in the limbic area that is devoted to producing and regulating pleasure called the reward system

REWARD SYSTEM Drugs of abuse activate the reward system in the limbic area of the brain—producing powerful feelings of pleasure Desire to repeat drug using behavior is strong Drugs of abuse can/do exert powerful control over behavior because they act directly on the more primitive, survival limbic structures— over-ride the frontal cortex in controlling our behavior

PARIETAL LOBES Integrate auditory, visual, and tactile signals
Right lobe– coordinates visual/spatial relationships Left lobe– coordinates spoken or written language Matures around ages 16-17

OCCIPITAL LOBES Primarily responsible for coordinating sight
Primary visual area where “pictures” are received from the eyes and relayed to other parts of the brain for interpretation Visualization requires more than “seeing”– the primary visual cortex processes information, temporal lobe recognize what we see, and the parietal lobes process information as we move through the space we see.

INFO FROM DANA BOOK Robert Finkbeiner, Dana Brain Book
The pathway used to recognize a familiar face starts with the eye sending info to the thalamus (yellow arrow) ; thalamus relays signal to the visual cortex (green arrow); which then signal superior temporal gyrus (blue arrow) which handles the emotional memories involved with recognizing friend or foe; all this takes less than one second Robert Finkbeiner, Dana Brain Book

CEREBELLUM Located at the base of the brain
Responsible for motor coordination Recent research suggests that it is involved in “coordinating” thinking processes– “mental clumsiness” (Geidd, 2002) Physical exercise is important for the development of the cerebellum – undergoes significant change during adolescence

CORPUS CALLOSUM Thick bundle of nerves that connects the two sides of the brain and relays information between the two cerebral hemispheres Involved in creativity and problem solving Influences language, learning, and associative thinking Changes significantly during adolescence (Geidd, 1999) Some studies have found that this area is thicker in girls—allowing for more communication between the left and right side of the brain Some studies have found that this area is smaller in people with autism

BRAIN STEM All nerve fibers pass through this area
Performs sensory, motor, and reflex functions Contains vital nerve centers that control breathing, heart rate, body temperature, and gastrointestinal activity Connects the brain with the body

BRAIN CIRCUITRY

Brain Circuitry NEURON —specialized cell designed to transmit information to other nerve cells and muscles Each neuron consists of a cell body, axon, and dendrite Axon– an electricity conducting fiber that carries information away from the cell body Dendrite– receives messages from other neurons Synapse– contact point where one neuron chemically “communicates” with another neuron Brain Facts, The Society for Neuroscience, 2002

(Illustration by Lydia Kibiuk, 1996)

BRAIN CIRCUITRY Neurons “communicate” by transmitting electrical impulses along their axons Axons send chemical neurotransmitter messages across a synapse to the receiving dendrite of the target neuron Each neuron has an average of 6,000 dendrite receptors Dendrite receptor sites are specialized areas— “lock and key” or “molecular handshake”

BRAIN CIRCUITRY A neuron may receive many different messages at the same time (Prioritize) Each neuron has to “interpret” incoming messages Neuronal communication is currently under intense study because it plays such a critical role in health and well being

BRAIN CIRCUITRY Electrical impulses travel along axon at speeds up to 250 mph (mylenation) Neurons forging connections with other neurons underpin learning Our brains are adaptable and can reflect on and learn from experience Neural connections are shaped by genetics and experience The more dendrites a neuron has, the more connections it will be able to make and the greater the circuitry underpinning a particular process or function. Just as a muscle grows with appropriate exercise, so selective circuits in the brain branch out and expand as they are worked. 100 billion nerve cells each of which branches out to hundreds of thousands of others –forming trillions of connections Everything we encounter will be interpreted in light of what we have seen before.

BRAIN CIRCUITRY Gray matter contains neurons that are responsible for “thinking” (100 billion) White matter contains suportive cells with nutritive roles (dendrites—1 trillion) Myelin is a layer of insulation that progressively insulates these supportive cells and is whitish in color Myelin makes white matter more efficient—just like insulation on electric wires—contributes to overall cognitive functioning (100x faster) Myelin affects the speed and quality of brain activity (Paus, et al., 1999)

NEUROTRANSMITTERS All messages are passed to connected neurons through a form of chemicals called neurotransmitters Neurotransmitters are released from the end of the axon, cross the synapse, and bind to the specific receptors on the dendrites of the targeted neuron Neurotransmitters bind with specific receptor sites on the receiving dendrite

MAJOR NEUROTRANSMITTERS
Acetylcholine —regulates memory Dopamine —produces pleasure through the “reward system”; multiple functions including controlling movement, regulates hormonal responses, important to cognition and emotion; abnormalities in dopamine levels have been implicated in schizophrenia Serotonin —plays a role in sleep; involved in sensory perception; and involved in controlling emotional states such as anxiety and depression

MAJOR NEUROTRANSMITTERS
Glutamate — excites the firing of neurons, aids process of memory Gamma-aminobutyric (GABA) — inhibits the firing of neurons

DEVELOPMENTAL VULNERABILITY
During adolescence, the prefrontal cortex (PFC), limbic system areas, and the white matter myelin are undergoing many changes (Chambers, 2003; Spear, 2000) These areas serving cognitive, behavioral, and emotional regulation may be particularly vulnerable to adverse alcohol effects Deficits or developmental delays in these structures and their functions may underlie vulnerabilities to alcohol use/abuse (Clark, Thatcher, & Tappert, 2008)

OVERPRODUCTION AND PRUNING
CRITICAL PEAKS OF BRAIN DEVELOPMENT

OVERPRODUCTION AND PRUNING
Brain development occurs in 2 basic stages– growth spurts/overproduction of neurons and pruning Critical phases: in utero 0-3 years overproduction 10-13 years Overproduction results in significant increase in the number of neurons and synapses Exuberant growth during these 3 phases gives the brain enormous potential Begley, 2000; Geidd, 1999

PRUNING These 3 critical phases are quickly followed by a process in which the brain prunes and organizes its neural pathways LEARNING is a process of creating and strengthening frequently used synapses (brain discards unused synapses) Brain keeps only the most efficient and “strong” synapses Children/teens need to understand that they decide which synapses flourish and which are pruned away (Geidd, 1999)

PRUNING “USE IT OR LOSE IT”– Reading, sports, music, video games, x-box, hanging out—whatever a child/teen is doing—these are the neural synapses that will be retained How children/teens spend their time is CRUCIAL to brain development since their activities guide the structure of the brain (Geidd, 1999)

What sorts of media are young people consuming?
Every year young people will see about 1,000 commercials advertising beer. 2/3 of young people have a TV in their room, 61% have no parental guidelines. Annually alcohol manufactures spend over $1 BILLION in TV, radio, print, and internet advertising. Young people sped an average of 1-2 hours daily listening to music. 63% of rap songs make reference to drug use, as do 10% of songs in other genres. Young people spend an average of 10 hours per week on the internet. 58% of young people have accessed websites of a violent or sexual nature. 82% of websites target youth.

BRAIN DEVELOPMENT Continued synaptic pruning, neural connection/integration, capacity to process information, and mylenation (driven by experience and practice)– these structural changes are believed to underlie the functional integration of frontal regions with the rest of the brain – adolescent into adult (Luna & Sweeny, 2004)

BRAIN DEVELOPMENT White matter development may underlie advancing executive functioning (Luna and Sweeney, 2004; Luna et al., 2001) Delays or deficits in the development of PFC may result in “neurodevelopmental dysmaturation” which can lead to “psychological dysregulation” Psychological dysregulation is a deficiency in the ability to regulate attention, emotions, and behavior in response to environmental challenges (Clark and Winters, 2002)

PSYCHOLOGICAL DYSREGULATION
Alcohol Use Disorders (AUD) typically do not happen in isolation– instead they appear to be correlated with persistent behavioral characteristics including: * attentional deficits; ADD, ADHD * conduct disorders; anti-social * irritability; aggression, diminished constraint * major depressive disorder; depression, anxiety Clark et al., 2005; Tappert et al., 2002; Chassin et al., 1999; Tarter et al., 1999

DEFINING ADOLESCENCE

ADOLESCENCE HAS ALWAYS BEEN CHALLENGING…
“Youth are heated by nature as drunken men by wine” Aristotle (350 B.C.) “I would that there were no age between 10-23, for there’s nothing in between but getting wenches with child, wronging the ancientry, stealing, fighting…” Shakespeare “The Winter’s Tale”, Act III (..1594)

DISPARITIES OF ADOLESCENCE
Adolescence is a time of triumph, high energy, great potential, resilient health, new found skills, creativity, humor….. Adolescence is also a time of turmoil often associated with high risk behaviors, impulsivity, and poor decision making Dramatic increase in death, disability, suicide, homicide, serious accidents, aggression, violence, emotional disorders, substance use, and risky sexual behaviors ¾ of deaths among adolescents are preventable Death and disability related to difficulties in control of behavior and emotion!!!!

REWARD SENSITIVITY Changes in reward sensitivity that occur at puberty lead adolescents to seek more novelty and require a higher level of stimulation to achieve the same subjective feeling of pleasure Changes in the limbic system, neuro- endocrinology, and an immature self regulatory system are implicated (Steinberg, 2004)

ADOLESCENCE Awkward period between sexual maturation and the attainment of adult roles and responsibilities Begins with the domain of physical/biological changes related to puberty, but it ends in the domain of social roles Encompasses the transition from the status of a child (one who requires monitoring) to that of an adult (responsible for behavior) [Dahl, 2003] Need to understand the NEUROBIOLOGICAL UNDERPINNINGS to adolescent behavior Some of these behaviors are universal across cultures Encourage young to “move out of the nest”—important for reproduction 80% of youth have little to no trouble navigating the transition of adolescence---need to identify what helps these kids be successful

STUDY OF ADOLESCENTS G. S. Hall, psychologist, began the modern study of adolescence about 100 years ago Increase in adolescent-related research in the early 1990’s; second increase began focusing on adolescent brain development in 1998 Most research is conducted on babies and toddlers Babies and toddlers have DRAMATIC changes While adolescents have significant changes—but they are subtle— improvement in existing capacities rather than the acquisition of new abilities

ADOLESCENCE Adolescence is much broader and longer than the teenage years alone (has changed significantly over the past 150 years) Adolescence now stretches across more than a decade, with pubertal onset often beginning by age 9-12 and adult roles delayed until mid twenties (Worthman, 1995)

ADOLESCENCE In the early 1900’s, the interval between puberty and achieving adult status was typically 2 years for girls and 4 years for boys (Schlegel and Barry, 1991) While puberty is occurring earlier in many industrial societies, marriage and other adult roles are often delayed; in the U.S. the average age of menarche is 12 and average age of 1st marriage is 26 (Dahl, 2004)

ADOLESCENCE Most elements of cognitive development show a trajectory that follows age and experience rather than the timing of puberty (Dahl, 2004) Research conducted by Martin, 2003, demonstrates a significant positive correlation between pubertal maturation and sensation seeking

ADOLESCENCE PUBERTY Romantic motivation Sexual interest
Emotional intensity Sleep cycle changes Appetite Risk for affective disorders (girls) Increase in risk taking, sensation seeking, and novelty seeking AGE/EXPERIENCE Planning Logic, reasoning Inhibitory control Problem solving Understanding consequences Affect regulation Goal setting and pursuit Judgment and abstract thinking Dahl, 2004

ADOLESCENCE VS. ADULTS Being a responsible adult requires developing self-control over behavior and emotions– must be able to appropriately inhibit behaviors despite STRONG FEELINGS The ability to integrate these multiple components of behavior, cognition, and affect in the service of long term goals involves neurobehavioral systems that are among the last regions of the brain to fully mature (Dahl, 2004)

NAVIGATING ADOLESCENCE
The most widely implicated factor associated with maladaption vs. resilience in adolescence is REGULATORY CAPACITY (RC) [Kupfer & Woodward, 2004] Behavioral control (RC) requires tremendous effort; adolescents need practice being consistent and integrating RC PFC and white matter development are needed for regulatory capacity

NAVIGATING ADOLESCENCE
What makes this possible? Driven by experience and practice Psychological regulation of attention, emotions, and behavior Continued synaptic pruning and mylenation Mentoring appropriate response patterns in the face of everyday life and decision making

Critical Differences Between Adult and Adolescent Thinking

Why is it that a young person is not able to drive a car until 16, vote until 18, drink alcohol until 21, rent a car from a commercial agency until 25, but in some states, can stand trial for murder at age 12 or 13? (Dahl, 2004)

DISPARITIES OF ADOLESCENCE
Adolescence is a TRANSITIONAL period during which a child is becoming, but is not yet, an adult Adolescent brains are far less developed than we previously believed Normal adolescent development includes conflict, risk taking, facing insecurities, creating an identity, mood swings, self-absorption, etc.

Underdevelopment of the frontal lobe/prefrontal cortex and the limbic system make adolescents more prone to “behave emotionally or with ‘gut’ reactions” (Yurgelun-Todd, 1999) Adolescents tend to use an alternative part of the brain– the AMYGDALA (emotions & aggression) rather than the prefrontal cortex (reasoning) to process information

Illustration by Lydia Kibiuk, 2003

Amygdala and nucleus acumbens (limbic system within the temporal lobes) tend to dominate the prefrontal cortex functions– this results in a decrease in reasoned thinking and an increase in impulsiveness Because of immature brains, adolescents do not handle social pressure, instinctual urges, and other stresses the way adults do A major part of adolescence is learning how to assess risk and consequences — adolescents are not yet skilled at these tasks (Dahl, 2004)

HOT AND COLD COGNITION Thoughts and emotions are intertwined – teens need to develop a balance between cognitive and affective systems of the brain “COLD” cognition refers to thinking under conditions of low emotions and/or arousal “HOT” cognition refers to thinking under conditions of strong feelings or arousal Decisions made under conditions of strong affect are difficult to influence by cool rational thought alone

HOT AND COLD COGNITION Decision making in teens cannot be fully understood without considering the role of emotions and the interaction between thinking and feeling (Dahl, 2003) Teen decisions are unlikely to emerge from a logical evaluation of the risk/benefits of a situation – rather decisions are the result of a complex set of competing feelings – desire to look cool, fear of being rejected, anxiety about being caught, excitement of risk, etc.

HOT AND COLD COGNITION Adolescent brain is a “vulnerable” system that could fail under “hot” high demanding situations – where the circuitry is not sufficiently established to sustain adult level cognitive control of behavior in the face of heightened states of emotion, motivation, distracting stimuli, or competing tasks (Luna & Sweeny, 2003)

ADOLESCENT BRAIN DLPFC is linked to the ability to inhibit impulses, weigh consequences, prioritize, and strategize – this area is still “under construction” until late 20’s (Giedd, 1999) Wernicke’s area (reception of speech) and Broca’s area (production of speech) undergo substantial changes during the teen years – impacts ability to listen and express oneself

Adolescents are not very skilled at distinguishing the subtlety of facial expression (excitement, anger, fear, sadness, etc.)—results in a lot of miscues—leads to lack of communication and inappropriate behavior Differences in processing, organization, and responding to information/events leads to misperceptions and misunderstanding verbal and non-verbal cues

Adult Brain Adolescent Brain YURGELUN-TODD, 1999

To appreciate consequences of risky behavior, one has to have the ability to think through potential outcomes and understand the permanence of consequences, due to an immature prefrontal cortex, teens are not skilled at doing this Teens do not take information, organize it, and understand it in the same way that adults do—they have to learn how to do this

Important to understand that teens often fail to heed common sense or adult warnings because they simply may not be able to understand and/or accept reasons that seem logical and reasonable to adults (difference in evaluating positive & negative consequences {Fromme et al., 1997}) Adolescents may know “right from wrong”, but they may not be able to prioritize when stressed with social/peer pressure NEVER assume that you and a teen are having the same understanding of a conversation

ADOLESCENT BRAIN DEVELOPMENT

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