Session Ten (Gender Differences in the Brain)

Question 1

What is the Tail Ratio Theory?

Answer 1

Theory explaining gender differences in men and women proposed by Darwin. Suggests that women cluster around the mean for characteristics, whereas men are more prevalent at either end of the spectrum.

Question 2

What evidence is there surrounding the Tail Ratio Theory?

Answer 2

Scottish IQ Survey study:

• Looked at a massive amount (90,000+ participants) of data for IQ in men and women
• Found there were in fact more men at the lower end of the spectrum, likely due to the higher rates of learning difficulties in men.
• Found slightly more men at the upper end of the spectrum, however very low significance of findings so remains unclear how true this is.

General criticism = it’s very questionable the extent to which IQ can be used in these cases, only tests a certain form of intelligence that may be biased towards men. Designed by men, therefore possibly mostly aimed at male intelligence

Question 3

What is the biggest criticism of the Tail Ratio theory in terms how how we understand real life gender differences?

Answer 3

Far more overlap than there are differences, and any difference in mean doesn’t actually affect the individual.

There are men and women represented everywhere on the scale, where one is more common than the other doesn’t matter as any one man/woman could find themselves anywhere.

Question 4

What two cognitive abilities do appear to show a very real differences in gender distribution?

Answer 4

Empathising = the drive to identify another person’s thoughts or emotions, and to respond to their mental states with an appropriate emotion. WOMEN broadly score higher.

Systemising = the drive to understand the rules governing the behaviour of a system and the drive to construct systems that are lawful. MEN broadly score higher.

However once again it is important to understand what this means, on average these differences exist, but both men and women are represented across the entire range of data.

Question 5

What gender differences appear to exist in terms of cognitive ability?

Answer 5

Men = better at mental rotation tasks.

Women = better at verbal fluency tasks.

Criticisms:

• Once again averages, have little bearing on an individuals ability
• These are artificial tasks in an artificial test environment, might well be totally irrelevant to real world function.

Question 6

What research has been done into gender differences in social play?

Answer 6

Hines et al:

• Gave a large group of children a number of different toys to play with
• Found boys played more with mechanical toys such as trucks and cars, whereas girls engaged best with toys relevant to social behaviour such as dolls or toy houses.
• Difference was very clear, highly significant
• Reflects the supposed systemising/ empathising split in functioning.
• Potentially suggests the immature brain developing along already distinct gender lines

Question 7

What criticism has been made about the Hines toy study and how was this counter-argued?

Answer 7

Social influence. Is it possible that even children as young as 2 understand what toys they are expected to play with? Unlikely but entirely possible.

However, chimp study found the exact same results. Unclear what a truck or toy chimp means to them but interesting nonetheless.

Question 8

What has research into the neurodevelopment of children and adolescent revealed about gender differences?

Answer 8

Normal pattern of teenage neural development = increase in white matter but decrease in grey matter.

This process appears to occur at an earlier age in girls, with drops in cortical grey matter occurring at an earlier age.

Question 9

What is Multivariate Pattern Classification and what has it shown re: gender differences in brain structure?

Answer 9

Researchers built a neural network by feeding in MRIs and telling the machine which are male and female, hoping it can learn to distinguish.

Findings: Was correct 70% of the time. Conclusion: better than chance so obviously there are some real differences in brain anatomy between men and women, however not 100% so clearly not entirely explained by differences such as cortical thickness. Suggested maybe the machine can pick up extremes, either very male or very female brains, but not ambiguous ones.

Indicates some differences, but outweighed by similarities

Question 10

What has Diffusion Tensor Imaging into the white matter of men and women shown about gender differences?

Answer 10

Study into the anatomy of the Arcuate Fasciculus:

• High variability in how unilateral language function is in people
• 60% uni, 20% somewhat bi, 20% very bi
• Found that the more bi people are, the better they perform on tests such as the California Verbal Learning Task
• Also found that women are significantly, significantly more likely to be bilateral
• Could explain why women are more likely to perform better at verbal learning tasks than men.

Question 11

What has evidence into the structural connectivity of the entire brain shown about the difference between men and women?

Answer 11

Ingalhalikara et al al:

• Male brains are structured to favour intra-hemispheric connectivity
• Female brains are structured to favour inter-hemispheric connectivity

Question 12

What have functional imaging studies shown about how male and female brains function in terms of language?

Answer 12

Confirm findings from DTI studies; male language activity is almost entirely unilateral, whereas female language processing is far more bilateral.

Question 13

How might sex chromosome evidence explain differences in male and female brains?

Answer 13

• Men = XY, Women = XX
• In women one of the X chromosomes ‘inactivates’ and the other takes over
• HOWEVER, not all genes on the second X chromosome become inactivated, and therefore are twice as active as in men
• Causing higher levels of some gene products in the cells of women than men
• These “dosage-sensitive” genes may be responsible for gender differences in neurodevelopment
• Influence would begin in the womb and carry on throughout life

Question 14

How can study into Turner’s syndrome aid in our understanding of the X chromosome’s influence on neurodevelopment?

Answer 14

• Women with Turner’s = XO
• Therefore similar to women but lack those doubly active genes
• Therefore any deficit they might experience could explain differences between men and women as well

Prominent ND differences seen in T’sS patients:

• Higher levels of autism
• Difficulty making eye contact
• Difficulty in reading facial expressions
• May even be afraid of faces

All traits associated with autism, which is also associated men.

Question 15

What is the main difference in the peri-natal environment of male and female foetuses?

Answer 15

Male foetuses experience a surge in testosterone in the second trimester of pregnancy

Question 16

What correlations exist between level of 2nd trimester free testosterone levels in the inter-uterine environment?

Answer 16

• Significant negative association between testosterone levels and empathic traits
• Significant positive association between testosterone levels and sub-clinical autism traits

Question 17

What is Congenital Adrenal Dysplasia, and what use is it to the study of male/female brain differences?

Answer 17

Deficiency in an enzyme involved in the adrenal hormone pathway, causes significantly reduced levels of cortisol and aldosterone, significantly increased levels of male androgens.

Useful because women with CAH are exposed to testosterone levels significant to men, therefore can usefully be compared to boys and girls.

Question 18

What did Pasterski et al (2005) find about young girls with CAH?

Answer 18

Looked into their play behaviour with boy/girl toys?

• Found they played with boys toys slightly more than unaffected girls but not as much as boys.
• Played with girls toys a lot less than unaffected girls but still more than boys.
• Suggested a mixed picture between boy/girl brain (in theory)
• Have to bare in mind social and cultural influence

Question 19

What did Kung et al (2016) find when meta-analysing the body of research into the link between androgen (CAH studies, amniotic testosterone) levels and male/female brain behaviour?

Answer 19

Nothing.

In contrast to other, older work in the field, found no association between androgen levels and autism traits.

Suggested androgen levels have zero influence on brain development, male/female, empathy/systemising…

Question 20

What gender differences exist in neurodevelopment disorders?

Answer 20

More common in men than women

Question 21

Autism is significantly more common in men than women (5 : 1), why could this be?

Answer 21

COULD be a fundamental difference in brain function, Baron-Cohen suggests the autistic brain is a more extreme version of normal male brain traits.

However could be much simpler than that, could be an under diagnosis issue.

Question 22

Why might an autism diagnosis be missed in a female patient?

Answer 22

Autism may present in a fundamentally different way in girls:

• Less co-morbid challenging behaviour
• Less abnormal special interests (men like trains, women like soap operas)
• Less stereotypical behaviour during play
• Better superficial social skills and language abilities
• Increased demand avoidance and extreme determination

Question 23

What patterns emerge when you compare men vs women vs autism patients along the Empathy-System classification?

Answer 23

• Syst: Women, Men, Autism
• Emp: Autism, Men, Women
• Quite a clear, significant difference noticeable delineation as well.
• Supports the notion that the autistic brain is just further along the male-female scale than the male brain.

However, as significant as the graphs appear, it is important to remember that once again the areas of overlap&raquo_space;»> areas of clear distinction.

People are mostly the same, distributed broadly across both scales BUT if you had to place people along them you’d do it on a clear pattern.

Question 24

How effective are neural network programmes at distinguishing men from women based on cortical thickness?

Answer 24

Neuro-typical subjects:

• 70% accuracy
• Quite high, suggests some clear difference but many people are ambiguous.

Autism Spectrum Disorder subjects:

• Bad
• 80% of women with autism classified as NT men

HOWEVER

• This may have been caused by a glitch in the programme
• Later versions of the programme where ablate correctly guess gender in 80% of cases

Question 25

Why might studies attempting to distinguish the male/female, NT/ASD brains be fundamentally flawed?

Answer 25

Most look at total grey matter volume, but in reality the differences are much more complex than simply more or less overall.

If you look at a detailed comparison you see a patchwork effect, some areas have greater volume in men, others have greater volume in women, ASD subjects have greater volume in some areas and less in others when compared to their NT counterparts.

Basically suggests the differences are immensely complex and should probably be studied region by region.

Question 26

What specific region has been shown to be significantly different between men and women with and without ASD?

Answer 26

The Frontal Lobe.

Zeestraten et al (2017):

• It appears as if men with ASD have significantly less frontal lobe connectivity than NT men
• Whereas women with ASD have slightly more connectivity than their NT counterparts.
• Frontal love is vital to personality, communicative abilities and executive function, all at least somewhat relevant to Autism.

Question 27

What differences in Schizophrenia presentation can be observed amongst men and women?

Answer 27

Men tend to have their first episode far younger.

• Most common age for men is 20-24
• Most common ages for women is 25-39

Potential explanations:

• Male brain remains undeveloped far longer than female, could mean that men exposed to a precipitating factor (e.g. cannabis) at this age are at risk but women are not.
• Women experience a spike in diagnosis around pregnancy and menopause, some have suggested oestrogen might have a protective role in preventing women developing Sz. Once this is removed, risk increases.

Question 28

What evidence is there to support the protective role of oestrogen against Schizophrenia?

Answer 28

Kulkarni et al (2008):

• 102 Sz patients
• Gave them a course of treatment consisting of an Anti-psychotic + either estradiol or a placebo
• Women given the estradiol experienced a significant reduction in Psychotic symptoms

Question 29

Whats the difference in depression rates amongst men and women?

Answer 29

More common in women (2:1)

Possibly due to women being more likely to present, less likely to self-medicate with drugs than men. But could also be a biological, hormonal issue.

Question 30

What are the 3 times in a woman’s life she is at increased risk of developing depression, and what is the running theme between them?

Answer 30

3 Risky Periods, Reproductive Depression:

• Onset of menarche (Premenstrual Dysphoric Disorder)
• Pregnancy (Postnatal Depression
• Menopause (Peri-menopausal Depression)

Link: Hormone changes, critical variations in Oestrogen and Progesterone.

This is an often controversial aspect of mood research, as many women feel the term “reproductive depression” to be unhelpful or sexist, and in fact a reaction to a biological change in your brain’s ability to moderate mood isn’t pathological at all.

…however they still present as depressed, and are still at risk of harming themselves therefore still a useful term to use.

Question 31

What influence does Oestrogen have on the brain?

Answer 31

Significantly modulates rates of serotonin uptake in the frontal cortex (related to mood).

Any change in oestrogen levels will affect serotonin levels, will imbalance mood.

Question 32

What did Bloch et al (2000) show?

Answer 32

Women with greater hormone sensitivity are at an increased risk of post-natal depression.

Question 33

What tests have been done into attentional bias in women around their menstrual cycle?

Answer 33

Surguladze et al (2005):

• Looked at Parahippocampal / Amygdala complex activation in response to neutral face stimuli amongst women at various points in their menstrual cycle.
• Found they were more likely to interpret a neutral face as negative during times of the month associated with fluctuations in hormone levels.
• Attention biases are similar to those seen in depressed people

Question 34

What evidence is there to suggest Estradiol can be used to treat peri-menopausal depression?

Answer 34

Schmidt et al (2015):
- Women given estradiol around this age experienced significantly reduced depression symptom scores (inc. sub-clinical) than those given a placebo

Question 35

What evidence is there to suggest Estradiol can be used to treat post-natal depression?

Answer 35

Gregoire et al (1996):

• Women treated with Estradiol after giving birth displayed a significant reduction in depression symptoms than women given a placebo
• These effects were maintained 8 months after delivery
• Works for both prevention and treatment

Question 36

What difference exists in Alzheimer’s rates between men and women, and what could explain this?

Answer 36

Women at significantly increased risk.

Could just be that they live longer therefore are more likely to develop the condition, however the effects appear to persist when this was controlled for.

Question 37

What effect does HRT have on the grey matter of older women, and what could explain this effect?

Answer 37

Robertson et al (2009): Significantly reduced atrophy in areas of the brain associated with mood and memory.

Potential explanations:

• Oestrogen has a protective effect against neuro-degeneration
• Healthy user effect, women who take HRT are likely to be far healthier generally, have fewer risk factors for A’s D

However a large meta-analysis into HRT and A’s D seemed to confirm these effects

Question 38

What did the Ancillary study show about women who did and did not take HRT?

Answer 38

Appeared to show women who took HRT were at GREATER risk of dementia than those who did not.

However critics of the study have suggested the sample group was not representative (significant proportion were obese for some reason). Furthermore, they gave them prog + estradiol, may have confounded (i.e. Oes might be protective but Prog might be damaging).

Question 39

Outline the critical period hypothesis of HRT and dementia?

Answer 39

Oestrogen therapy confers optimal cognitive benefits when initiated closely in time to the menopausal transition

Question 40

What can be learned about dementia risk from women who’ve had Ovariectomies?

Answer 40

• Women who had both removed before the age of 46 showed an 80% risk of dementia
• However those who were given HRT subsequent showed reduced risk