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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