1) The brain continues developing through adolescence and early adulthood, with significant changes occurring in brain structure and function during this period. 2) Puberty triggers a cascade of hormonal changes that influence brain development in both direct and indirect ways. Areas of the brain involved in self-regulation and risk-taking, such as the prefrontal cortex, are among the last to fully mature. 3) Adolescents tend to engage in more risk-taking behaviors than children or adults, which may be explained by an imbalance between the earlier maturation of the brain's reward system versus the later maturation of self-control regions.

1. The Teenage Brain “ Youth are heated by nature as drunken men by wine.” Aristotle

2. New Thinking 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 The brain has reached 90 percent of its full size by the age of 6 New research shows the brain continues to evolve through the teens & early twenties This may help explain why teens act the way they do.

3. The Chicken & The Egg: The Effect of Puberty Adolescent brain development is influenced by pubertal maturation Puberty is the onset of sexual maturation Includes changes in three separate neuroendocrine axes: Gonadal Adrenal androgens Growth

4. Neuroendocrine Changes Gonadarche: turning on the hypothalamic-pituitary-gonadal axis Leads to estrogen production & breast development in girls Testosterone production & maturation of male genitalia in boys. Adrenarche: turning on adrenal androgen production in both boys & girls Contributes to development of secondary sex characteristics Growth: growth hormone secretion Rapid physical growth Changes in body composition .

5. The Role of Puberty in Brain Development Brain changes that contribute to the cascade of hormone changes Pubertal brain changes that are caused by maturational hormonal increases Maturational brain changes that occur relatively independent of puberty Maturational processes linked to puberty in indirect ways e.g., new experiences that occur as a result of sexual maturation

6. Teen Brains Are Different Most of the new developments in the study of teenage brains comes from magnetic resonance imaging (MRI) Studies by Dr. Jay Giedd - Child Psychiatry Branch of NIMH 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. During the teen years, the brain trims back excess cells and connections

7. Adolescent Risk Taking Mortality rises during adolescence, then comes back down 32% of deaths during this period result from motor vehicle accidents mortality is 2 to 3 times greater in males than females. Some aspects of teenage behavior (e.g. mood swings & risk taking) may be explained by brain development

8. Risk Taking: It’s All in Your Head MRI shows one of the last parts of the brain to complete maturation is the prefrontal cortex This is the part of the brain responsible for planning, judgment and self-control Maturation of neural networks governing self-regulation doesn't occur until late in adolescence Sensitivity to rewards is different in adolescents than in adults Seek higher levels of stimulation to achieve the same feeling of pleasure Increased risk-taking during adolescence is normal and biologically driven

9. Other Important Developments White matter increases linearly during adolescence The cerebellum also grows in volume. Adolescence is the most efficient time for motor learning

10. Adolescence & Schizophrenic Brains Studies of adolescent brain development may lead to greater understanding of schizophrenia & vice versa David A. Lewis - University of Pittsburgh Schizophrenics show impaired maturation of the circuitry of the prefrontal cortex. working memory is impaired Connections regulating the transmission of dopamine must be intact for working memory to function properly.

11. The Connection A reduction in excitatory synapses occurs during adolescence This reduction is even greater in schizophrenia. The reduced number of excitatory synapses may explain the impairment of working memory in schizophrenia and the onset of its symptoms during adolescence.

12. MRI of Schizophrenic Brain Brain scan of Schizophrenic patient (right) and normal brain (left). The normal brain shows more activity in the frontal cortex.

13. Stress and Brain Development Changes in reproductive and stress hormones can influence behavior. Hormonal changes during adolescence can also trigger depression. Stress can cause hormone changes by increasing cortisol levels.

14. Brain Plasticity, Stress & Hormones Experiences and behaviors encountered early in life can effect how the brain changes to adapt to its environment. Repeated stress increases anxiety and aggression. Stress can cause physical changes in the brain that result in changes in behavior as well. Stress increases the size of the amygdala and causes shrinkage of the hippocampus. Brain changes can also be observed in studies of patients with major depression.