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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

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  2. GOALS Toincrease participantunderstanding 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

  3. CAVEATS • Newdiscoveries — research is still in itsinfancy • Do NOTover-interpretor 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 ofcomplex interactionsamong individual, environment, genetics, situation, cultural expectations, and numerous other factors


  5. 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 BRAIN FACTS

  6. Illustration by Lydia Kibuik, 2003

  7. EVOLUTION OF THE NEW BRAIN Every mammal’s brain has the same basic structure- cortex, cerebellum, and brain stem–cortical surface area is key

  8. CHALLENGE OF UNDERSTANDING THE BRAIN • Whatis 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?

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

  10. 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

  11. FRONTAL LOBE • Seat ofpersonality, judgment, reasoning, problem solving, and rational decision making • Provides for logic, understanding of consequences, and emotional/behavioral regulation • Governsimpulsivity, 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)

  12. 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 isone of the last areas of the brain to fully develop (Sowell, 2001) • Increased need for struc- ture, mentoring, guidance


  14. Brown et al., 2008

  15. 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

  16. 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 cellsin thelimbic area that is devoted to producing and regulating pleasure called the reward system

  17. 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

  18. 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

  19. 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.

  20. INFO FROM DANA BOOK Robert Finkbeiner, Dana Brain Book

  21. 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

  22. 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)

  23. 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


  25. 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

  26. (Illustration by Lydia Kibiuk, 1996)

  27. BRAIN CIRCUITRY • Neurons“communicate”by transmitting electrical impulses along their axons • Axons send chemical neurotransmitter messages across asynapseto the receivingdendriteof the target neuron • Each neuron has anaverage of 6,000 dendrite receptors • Dendrite receptor sites arespecialized areas— “lock and key” or “molecular handshake”

  28. 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

  29. 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

  30. 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 onelectricwires—contributes to overall cognitive functioning (100x faster) • Myelin affects the speed and quality of brain activity (Paus, et al., 1999)

  31. 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

  32. 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

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

  34. 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)


  36. 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

  37. 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)

  38. 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 CRUCIALto brain development since their activities guide the structure of the brain (Geidd, 1999)

  39. 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.

  40. 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)

  41. 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)

  42. 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


  44. 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)

  45. 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

  46. 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)

  47. ADOLESCENCE • Awkward period between sexual maturation and the attainment of adult roles and responsibilities • Beginswith the domain of physical/biological changes related to puberty, but itends 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]

  48. 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

  49. 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)

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