Lecture 8 - Sex and the brain

Question 1

What is genotype?

Answer 1

the full set of genes that an organism possesses, different genes are organised into chromosomes

Question 2

How many chromosomes does an individual have?

Answer 2

• 46
• 23 from mother
• 23 from father
• a female has 2 X chromosomes and a male has 1 X and 1 Y

Question 3

Sex hormones?

Answer 3

• testosterone
• progesterone
• released in different proportions by both male and female reproductive organs
• all hormones come from cholesterol

Question 4

What are the 3 things we are a product of?

Answer 4

1. genotype (XX or XY)
2. action of sex hormones
3. proportion of sex hormones

Question 5

The male and female brain?

Answer 5

• certain regions of the brain are ‘sexually dimorphic’
• the pre-optic nucleus is bigger in adult males and is related to testosterone levels and sexual activity in males
• the ventromedial nucleus of the hypothalalmus is involved in female sexual behaviour etc.

Question 6

Genetic mutations that affect sexual identity?

Answer 6

• usually the genotype and phenotype sex of an individual are aligned
• however there are a variety of genetic mutations that result in an ambiguous sexual phenotype e.g.
  -> Turner’s syndrome
  -> Congenital adrenal hyperplasia
  -> Androgen insensitivity syndrome

Question 7

Female sexual behaviour in rats?

Answer 7

• mediated by the ventromedial region of the hypothalamus
• dependent on estradiol & progesterone

Question 8

Male sexual behaviour in rats?

Answer 8

• mediated by the pre optic area of the hypothalamus
• dependent on testosterone
• oxytocin release plays a role in pair bonding

Question 9

Women’s facial attractiveness and the fertile period?

Answer 9

• faces in fertile window and luteal phase are ranked as more attractive compared to faces in the follicular phase
• estradiol produces changes in face attractiveness

Question 10

What is the amygdala’s involvement in human sexual motivation?

Answer 10

• viewing erotic movies caused activity in the amygdala for men and women
• amygdala volume correlated with sexual interest in epilepsy patients who underwent temporal resection
• stimulation of amygdala in an epilepsy patient elicited sexual experience related sensations
• potentially related to amygdala’s processing of emotional arousal

Question 11

What is the role of the frontal lobe in sexual behaviour?

Answer 11

• amygdala and hypothalamus are both involved in sexual motivation and sexual behaviour
• lesions to frontal lobe cause:
  -> loss of inhibition about sexual behaviour
  -> erotomania = conditon in which people believe that another person is in love with them
• lesions to the dorsolateral prefrontal cortex (DLPFC) = aggressive sexual behaviour

Question 12

What happens when the DLPFC is stimulated?

Answer 12

• p’s reported less intent to commit physical/ sexual assault
• p’s reported an increase in immorality of the act
• the increase in immorality rating explained the decrease in intent

Question 13

Sexual reward?

Answer 13

• successful completion of sexual behaviour (orgasm) is accompanied by a reward
  -> dopamine release
  -> relaxation due to oxytocin release
• oxytocin may aid in pair bonding and is said to be involved in mother-infant bonds

Question 14

Differences in cognitive ability between sexes?

Answer 14

• women perform better on tests of verbal fluency
• men perform better on tests of spatial reasoning

Question 15

What are pheromones?

Answer 15

• they carry messages from 1 animal to the other and affect reproductive behaviour
• detected by olfactory receptors
• processed by the vomeronasal organ which activate the amygdala and the hypothalamus

Question 16

What to pheromones lead to in rats?

Answer 16

• acceleration of puberty when housed with a male
• restarting the esters cycle of female rats exposed to odour of a male
• termination of early pregnancy when exposed to a novel male

Question 17

What can pheromones lead to in humans?

Answer 17

• synchronisation of menstrual cycles
• higher pleasantness ratings of odour from females during the fertile period
• pheromones are detected by the normal olfactory system in humans

Question 18

Savic and Lindström (2008)?

Answer 18

• wanted to see whether homosexual men and women show sex atypical symmetry and connectivity
• results regarding symmetry:
  -> homosexual women and heterosexual men show asymmetrical brains
  -> heterosexual women and homosexual men show more symmetry
• results regarding amygdala connectivity:
  -> similar in heterosexual men and homosexual women
  -> sensorimotor systems and striatum regulating an action-related response
  -> similar in homosexual men and heterosexual women
  -> regions of the limbic system regulating stress, mood & anxiety related response