Adolescent Dev W05 Study

• By age 6: the brain is 90% to 95% of its adult size. 
• maximum brain-cell density: occurs between the third and sixth month of gestation 
• Rapid neural growth occurs: between the ages of 6 and 12 
• Peak of neural growth: when girls are about 11 and boys 12 ½ 
• Gray matter is thinned out at a rate of about 0.7% a year, tapering off in the early 20s 
• Cerebellum: area that coordinates both physical and mental activities & is particularly responsive to experience 
• Regions that reach maturation first: vision, hearing, touch and spatial processing 
• Brain areas that mature second: areas that coordinate vision, hearing & touch 
• Last part of brain to form: Prefrontal cortex 
• Prefrontal cortex: home of the so-called executive functions--planning, setting priorities, organizing thoughts, suppressing impulses, weighing the consequences of one's actions. 
• Androgens and estrogens: Released as pruning begins; directly influence serotonin and other mood-regulating neurochemicals, especially active in the limbic system 
• Limbic system: emotional center of the brain 
• Adolescents engage in high risk behavior, impulse control is not fully formed 
• MRI: reveals brain structure 
• FMRI: shows brain activity while subjects are doing assigned tasks 
• In identifying emotional expressions children and adolescents use more amygdala, while adults use frontal lobe. 
• Amygdala: a structure in the temporal lobes associated with emotional and gut reactions 
• Social influences: Teens have higher likelihood of risk behavior when in groups or emotionally charged situations, not after age 20  
• Abundance in dopamine-rich areas of the brain: an additional factor in teen vulnerability to substance abuse 
• nucleus accumbens: region in the frontal cortex that directs motivation to seek rewards 
• Motivation deficit: comes with propensity to engage in high excitement and or low effort behaviors, emphasis immediate payoff for best results 
• Melatonin levels: take longer to rise in adolescents than children or adults regardless of sun or activities 
• ADHD and Tourette's syndrome: typically appear by age 7; rapid growth of brain tissue may set the stage for the increase in motor activities and tics, symptoms recede as pruning begins  
• Schizophrenia: appears about the time the prefrontal cortex is getting pruned; typical cortical gray matter loss is 15% during adolescence, but 25% sometimes in schizophrenia cases. 
• Emerging adult age: The median onset for anxiety disorders, depression, bipolar disorder, and schizophrenia 
• Age 25: best estimate for when the brain is truly mature 
• How to help teens: providing structure, organizing their time, guiding them through tough decisions 
• Overproduction or Exuberance: considerable thickening of synaptic connections occurs during prenatal development through first 18 months of life, again around ages 10–12 peaking there 
• Overproduction: occurs in many parts of gray matter, but concentrated in frontal lobes 
• frontal lobes: involved in most of the higher functions of the brain: planning ahead, solving problems, making moral judgments. 
• Between the ages of 12 and 20: the average brain loses 7% to 10% of its gray matter 
• synaptic pruning is especially rapid: among adolescents with high intelligence 
• Myelination: creation of myelin sheaths 
• Myelin: a blanket of fat wrapped around the main part of the neuron, serves the function of keeping the brain’s electrical signals on one path and increasing their speed, continues through adolescence 
• Cerebellum: part of the lower brain, important for mathematics, music, decision making, and even social skills and understanding humor. It continues to grow through adolescence and well into emerging adulthood  
• the last structure of the brain to stop growing: Cerebellum  
• How brain structure changes in emerging adulthood: continued myelination, synaptic pruning, and the formation of new connections 
• gray matter: is composed of brain cells decreases through 20s and 30s 
• white matter: consists of myelinated axons and other connections between brain cells, increases through pruning until 40 when it declines rapidly 
• rapid synaptic pruning of the gray matter during emerging adulthood: implicated in the development of schizophrenia, anxiety, and depression 

\