3 - BRAIN DEVELOPMENT

Question 1

statement:

brain requires hormones to develop in male-typical form

(rodents)

Answer 1

-

Question 2

what hormone is required to masculinise the brain?

Answer 2

estrogens (female sex hormone)

Question 3

experimental (behavioural) evidence of how estrogens affect brain development (rodents)

Answer 3

• treating new-born female rats with estrogens will cause them to show male-typical sexual behaviour as adults

Question 4

what does SDN-POA stand for?

Answer 4

sexually dimorphic nucleus of the preoptic area of the hypothalamus

Question 5

problem with the hormonal influence on brain development (rodents)

+

what solves it?

Answer 5

problem: all rat embryos are exposed to maternal estrogens
- so why do not all rats show male-typical sexual behaviour? (large SDN-POA)
- how do brains then develop differently?
solution: aromatisation hypothesis

Question 6

what is the aromatisation hypothesis?

rodents

Answer 6

• the mother’s estrogen is inactivated (by a-fetoprotein)
• but androgens (produced by newly developed testes of male rat embryo) can enter the brain
• in the brain - aromatase converts androgens to estrogens
• this then masculinises the brain

Question 7

human brain development

Answer 7

• male and female brain assumed to develop differently (assumed to be similar as in rats)
• no influence of maternal estrogens as they can’t cross the placenta
• thought maybe aromatisation?

Question 8

evidence supporting the aromatisation hypothesis in humans

Answer 8

• synthetic estrogens can cross the placenta (given to support pregnancy if women has has previous complications)
• daughters may then show male-specific behaviour?
• but male-specific behaviour in humans is not clear in humans

Question 9

which type of developmental disorder is used as evidence against the aromatisation hypothesis in humans

Answer 9

androgen-insensitive XY individuals

• normal levels of androgens
• normal levels of aromatase
• normal estrogen receptors in brain
• should develop ‘male-typical’ brains
• but show ‘female typical’ behavioural patterns instead
• could be because they don’t have working androgen receptors so androgens cannot convert into estrogens, so therefore the brain isn’t masculinised
• therefore androgen receptors play a role in human male brain development (not clear what a human male brain even is)

Question 10

are differences between males and females categorical or gradual?

Answer 10

gradual!

no clear categorical differences between them