Sex and the brain

Question 1

sexual dimorphisms

Answer 1

characteristics that differ between males and females, ex. how they look (especially for birds), physiology, behavior

Question 2

flow of sexual development

Answer 2

genetic sex -> gonadal sex -> hormonal sex -> morphological sex

Question 3

determination of gonads

Answer 3

SRY gene on Y chromosome is responsible for changing the gonads into testis (ovaries are the default)

Question 4

role of hormones in development

Answer 4

testosterone: needed for male development estradiol: not needed for female development, ovaries don’t have to produce any hormones early in development for a fetus to become female because female is default

Question 5

the androgen receptor

Answer 5

largely responsible for morphological sex of males, androgrens include testosterone and DHT, the receptors are within the cell and work because the hormones are steroids which can go through membrane easily

Question 6

role of estrogen in development

Answer 6

brain has a lot of estrogen receptors. when activated in early development they “masculinize” the brain.

female fetuses produce alphafetoprotein which binds to mother’s estrogen to prevent it from interfering with child’s development

Question 7

hormone cycling

Answer 7

occurs in females

if you castrate males at birth: will cycle hormones, treat with testosterone within first 20 days they wont cycle but after 20 days they will

Question 8

organizational vs activational effects

Answer 8

organizational: happens early in development, permanent
activational: occurs after differentiation, temporary

Question 9

reproductive behavior

Answer 9

hormone based, lordosis v. mounting

Question 10

sexual dimorphisms in humans

Answer 10

neural structures: nuclei in the peroptic area of the hypothalamus larger in males?, more cortical interhemispheric connections in females and more cortical intrahemispheric connections in males, more cerebellar intrahemispheric connections in females and more cerebellar interhemispheric connections in males

mental illness: autism, anorexia

cognitive functions? : females generally perform better on verbal tasks while males perform better on spatial tasks

Question 11

challenges to studying neural basis of cognitive function/ behavioral sex differences in humans

Answer 11

hard to separate cultural/social/environmental influences from hormonal/genetic influences (practice, stereotype threat)

wide individual variation (distribution overlaps)

Question 12

evidence for biological basis of sexual orientation in humans

Answer 12

statistics based, introspection, family studies (fraternal birth order), pre-optic nucleus (INAH-3) of HIV+ homosexual men found to be the same average size as women and smaller than heterosexual men (questionable study, though)

Question 13

volves mating strategies

Answer 13

prairie voles: monogomous

meadow voles: permiscuous

observation: when prairie voles mate vasopressin levels rise in males and the expression of vasopressin receptors in teh ventral pallidum of prairie voles in comparison to meadow voles
hypothesis: increaed vasopressin signaling is important for monogous behavior

Question 14

volves LOF/GOF experiments

Answer 14

GOF (sufficiency):

increase expression of vasopressin receptors and provide vasopressin in meadow voles -> monogomous

give vasopressin to males without mating with females ->create pair bonding

LOF (necessity):

decrease vasopressin signaling (through genetics or drugs) -> look to see if praire wolves become permiscuous