The Teenage Brain


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The Teenage Brain

  1. 1. The Teenage Brain “ Youth are heated by nature as drunken men by wine.” Aristotle
  2. 2. New Thinking <ul><li>Scientists once thought that all of the brain’s cells were present at birth and that all connections were established and “hard wired” in infancy and early childhood </li></ul><ul><ul><li>The brain has reached 90 percent of its full size by the age of 6 </li></ul></ul><ul><li>New research shows the brain continues to evolve through the teens & early twenties </li></ul><ul><li>This may help explain why teens act the way they do. </li></ul>
  3. 3. The Chicken & The Egg: The Effect of Puberty <ul><li>Adolescent brain development is influenced by pubertal maturation </li></ul><ul><li>Puberty is the onset of sexual maturation </li></ul><ul><li>Includes changes in three separate neuroendocrine axes: </li></ul><ul><ul><li>Gonadal </li></ul></ul><ul><ul><li>Adrenal androgens </li></ul></ul><ul><ul><li>Growth </li></ul></ul>
  4. 4. Neuroendocrine Changes <ul><li>Gonadarche: turning on the hypothalamic-pituitary-gonadal axis </li></ul><ul><ul><li>Leads to estrogen production & breast development in girls </li></ul></ul><ul><ul><li>Testosterone production & maturation of male genitalia in boys. </li></ul></ul><ul><li>Adrenarche: turning on adrenal androgen production in both boys & girls </li></ul><ul><ul><li>Contributes to development of secondary sex characteristics </li></ul></ul><ul><li>Growth: growth hormone secretion </li></ul><ul><ul><li>Rapid physical growth </li></ul></ul><ul><ul><li>Changes in body composition . </li></ul></ul>
  5. 5. The Role of Puberty in Brain Development <ul><li>Brain changes that contribute to the cascade of hormone changes </li></ul><ul><li>Pubertal brain changes that are caused by maturational hormonal increases </li></ul><ul><li>Maturational brain changes that occur relatively independent of puberty </li></ul><ul><li>Maturational processes linked to puberty in indirect ways </li></ul><ul><ul><li>e.g., new experiences that occur as a result of sexual maturation </li></ul></ul>
  6. 6. Teen Brains Are Different <ul><li>Most of the new developments in the study of teenage brains comes from magnetic resonance imaging (MRI) </li></ul><ul><ul><li>Studies by Dr. Jay Giedd - Child Psychiatry Branch of NIMH </li></ul></ul><ul><li>Images show thickening in gray matter on the outer part of the brain peaks at age 11 in girls and at age 12 in boys. </li></ul><ul><li>During the teen years, the brain trims back excess cells and connections </li></ul>
  7. 7. Adolescent Risk Taking <ul><li>Mortality rises during adolescence, then comes back down </li></ul><ul><ul><li>32% of deaths during this period result from motor vehicle accidents </li></ul></ul><ul><ul><li>mortality is 2 to 3 times greater in males than females. </li></ul></ul><ul><li>Some aspects of teenage behavior (e.g. mood swings & risk taking) may be explained by brain development </li></ul>
  8. 8. Risk Taking: It’s All in Your Head <ul><li>MRI shows one of the last parts of the brain to complete maturation is the prefrontal cortex </li></ul><ul><ul><li>This is the part of the brain responsible for planning, judgment and self-control </li></ul></ul><ul><li>Maturation of neural networks governing self-regulation doesn't occur until late in adolescence </li></ul><ul><li>Sensitivity to rewards is different in adolescents than in adults </li></ul><ul><ul><li>Seek higher levels of stimulation to achieve the same feeling of pleasure </li></ul></ul><ul><li>Increased risk-taking during adolescence is normal and biologically driven </li></ul>
  9. 9. Other Important Developments <ul><li>White matter increases linearly during adolescence </li></ul><ul><li>The cerebellum also grows in volume. </li></ul><ul><li>Adolescence is the most efficient time for motor learning </li></ul>
  10. 10. Adolescence & Schizophrenic Brains <ul><li>Studies of adolescent brain development may lead to greater understanding of schizophrenia & vice versa </li></ul><ul><ul><li>David A. Lewis - University of Pittsburgh </li></ul></ul><ul><li>Schizophrenics show impaired maturation of the circuitry of the prefrontal cortex. </li></ul><ul><ul><li>working memory is impaired </li></ul></ul><ul><li>Connections regulating the transmission of dopamine must be intact for working memory to function properly. </li></ul>
  11. 11. The Connection <ul><li>A reduction in excitatory synapses occurs during adolescence </li></ul><ul><li>This reduction is even greater in schizophrenia. </li></ul><ul><li>The reduced number of excitatory synapses may explain the impairment of working memory in schizophrenia and the onset of its symptoms during adolescence. </li></ul>
  12. 12. MRI of Schizophrenic Brain <ul><li>Brain scan of Schizophrenic patient (right) and normal brain (left). The normal brain shows more activity in the frontal cortex. </li></ul>
  13. 13. Stress and Brain Development <ul><li>Changes in reproductive and stress hormones can influence behavior. </li></ul><ul><li>Hormonal changes during adolescence can also trigger depression. </li></ul><ul><li>Stress can cause hormone changes by increasing cortisol levels. </li></ul>
  14. 14. Brain Plasticity, Stress & Hormones <ul><li>Experiences and behaviors encountered early in life can effect how the brain changes to adapt to its environment. </li></ul><ul><li>Repeated stress increases anxiety and aggression. </li></ul><ul><li>Stress can cause physical changes in the brain that result in changes in behavior as well. </li></ul><ul><li>Stress increases the size of the amygdala and causes shrinkage of the hippocampus. </li></ul><ul><li>Brain changes can also be observed in studies of patients with major depression. </li></ul>