Lecture 16 - Genetics of Sex Differences in Behaviour Flashcards
1
Q
Why study sex differences?
A
- Relevant to all
- Relevant to many areas of psychology
- Most brain disorders show some sort of sex bias
2
Q
Define sex differences:
A
- Variations in biology between men and women
3
Q
Describe gender differences:
A
- Differences between men and women in terms of biology and self-representation as shaped by the environment
4
Q
What are notable sex differences?
A
- Language acquisition: female vocab is 2x larger
- Physical aggression/behavioural disinhibition
- Sexual preferences
5
Q
When do females outperform males?
A
- Memory for phonological and semantic
- Prose production and comprehension
- Fine motor skills assessment
- Assessing perceptual speed
- More cross talk among hemispheres e.g unilateral stroke = females are better at coping
6
Q
When do males outperform females?
A
- Motor skills in aiming
- Transformations in visuospatial working memory
- Fluid reasoning
- Spatiotemporal responding
7
Q
What about IQ?
A
- Average is roughly the same but men have more variability
8
Q
Sex differences in brain structure:
A
- Male brain bigger from 2 weeks but female brain has more developed neuropil
- Females mature more rapidly
- Females have a larger Wernicke’s area, orbitofrontal cortex, corpus collosum, hippocampus.
- Men have larger amygdala, fronto-medial cortex
- Male brains are wired back to front
- Female brains wired left to right
- Can be seen through fMRI
9
Q
What are differences in brain structure related to?
A
- Regulate sex-specific physiology/behaviour e.g ovulation
10
Q
What are key issues in sex differences research?
A
- Small effect sizes with lots of overlap
- Temporal specificity = children level out vocab after a certain age but females develop it faster
- Effects of menstrual cycle
- Differences in test performance modulated by context = telling people you are testing by gender affects results
- Studies in model organisms use males
- Difference in brain structure do not predict behavioural differences
- Differences are not deficiencies
- Most studies are performed in WEIRD populations
- Differences supported by evidence can be used for prejudice
- Differences may arise due to social conditioning or selection bias
11
Q
Why are sex differences more nature than nurture?
A
- Differences in genes and brain
- Differences in male/female toys when given to Rhesus monkeys and other animals.
12
Q
What are the GENERAL sex differences in neurodevelopmental and psych disorders?
A
- Prevalence e.g more females have anorexia
- Age-at-onset
- Disorder subtypes and co-morbidity
- Clinical course e.g males are more likely to get more addictive disorders
- Underlying neurobiology e.g ADHD & Autism
- Response to therapy.
13
Q
How are different rates of diagnosis affecting the sexes?
A
- More overt and disruptive behaviours
- Closer conformation to diagnostic form
- More abstract obsessions
- More effective masking strategies in females
14
Q
What are mechanisms underlying sexual differentiation of the brain
A
- Due to chromosome complement
- Males have a Y chromosome
- Females have two X
- Which X do they get from which parent
15
Q
Describe the difference between X and Y chromosome?
A
- X is larger
- Contains genes involved in neurodevelopment
- Y is smaller and contains pseudo genes
- Most genes are involved in sperm production - some expressed in brain
16
Q
What is SRY and what does it influence?
A
- Influences brain development indirectly via gonadal hormones
- Identified as testis-determining factor in the early 1990s
- XY, XXY, XXXY subjects = male
- Sry-transgenic XX mice sterile males
- Translocation of part of Y chromosome containing SRY to X chromosomes can cause XX male syndrome
- Rare XY females with mutations of SRY (Swyer syndrome)
17
Q
What does the SRY gene do?
A
- Causes would be ovaries to turn into testes
- Releases androgens: highly concentrated in sexually dimorphic development
18
Q
How do androgens affect masculinisation?
A
- Critical pre/perinatal periods
- Genital virilization
- Gender determination
- Increase under 4-6 mo. Postnatally
- Later life e.g puberty
19
Q
What is the extreme male brain theory?
A
- Males and females differ with regard to systemising and empathising behaviours
- Individuals with autism have more systemising behaviours than empathising
- Suggested people with autism have been exposed to high levels of androgens in their life
- Tested that in utero testosterone correlates to later male/autistic traits
- Indirect methods: finger length e.g ring finger longer than index
People with autism have genes changes with X
20
Q
What experiments took place in guinea pigs?
A
- Female GPs and gave them testosterone and acting more aggressive
- Male GPs and removed testes and became more passive
21
Q
What do Gynandromorphic birds show?
A
- Left side = testicle, right = ovary
- Every cell in body is covered by same hormones
22
Q
How does SRY influence brain function?
A
- Highly expressed in dopaminergic activity
- Many male-biased disorders exhibit dopaminergic disorders
- Other Y-linked genes may confer risk in males
23
Q
What does higher expression of X-linked genes do?
A
- One X is switched off to ensure equal activity with males
- 20% of all linked genes are more highly expressed in female brain as they are expressed from both X chromosomes
- Could confer protection against disorders
24
Q
What is the parental origin of the X chromosome?
A
- Turner syndrome inherit single chromosome from mum/dad
- Compare brain structure
- The maternal one is more likely to show deficits in social cognition
- Protective effect of paternal X = better at social processes
