Hormones and Brain Development Before we begin… In your journal, write 3 questions that you have relating to hormones and brain development
Journal Entry #9: a) Read pages 228- 230- end before Injury and Brain Developmentb) Did the reading answer any of your questions? Explain.
Hormones and Brain Development • Testosterone (Androgren) • Stimulates development of male reproductive organs and the later development of male secondary sexual characteristics (e.g., facial hair) during puberty • Masculinization • Process by which exposure to androgens (male hormones) alters the brain, rendering it identifiably male
Hormones and Brain Development • The presence of testosterone and estrogen both affect the development of the brain • Can alter: • Number of neurons • Dendritic branching • Synaptic growth • Not just areas of brain related to sexual behavior: These hormones can affect “higher functions”such as cognition
Hormones and Brain Development Bachevalier and colleagues: Postnatal Effects • Monkeys (concurrent discrimination task and object reversal learning) • Male and females showed different patterns of performance on tests at 2.5 months old (males were better at reversal learning but females were better at concurrent discrimination) • Males that had testes removed at birth performed more like females
Concurrent-discrimination task Measures trial and error learning of specific object information- function of basal ganglia
Hormones and Brain Development Bachevalier and colleagues: Postnatal Effects • Humans • Similarly, males and females showed different patterns of performance around 15 to 30 months of age • Sex differences disappeared at 32 to 55 months of age
Hormones and Brain Development Bachevalier and colleagues: Postnatal Effects Conclusion: Testosterone influences the rate of early brain development in areas related to certain cognitive behaviors.
Hormones and Brain Development Juraska (1990): Postnatal Effects • Rats Reared in Complex Environments • Males showed more dendritic growth in the visual cortex than females • Females showed more dendritic growth in frontal lobes than males • Summary: • Sex differences in brain structure exist throughout development
A gynandromorph- exhibits physical characteristics of both sexes
Homework: Answer these questions in your journal (as part of entry #9) • How is the determination of sex genetic? • How does testosterone affect brain development? • At which periods throughout life do hormones have an effect on brain development? • Are male and female brains the same? Explain, using evidence to support your answer. • What is the author of the textbook’s perspective on the effects of nature vs. nurture on the sexual dimorphisms that exist in the brain? Do you agree?