Lecture 6 - Sex Differences 2 Flashcards Preview

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1

Outline sex difference in behaviour and relevant neural substrates Arnold 2009 XX chromosome

XX -> ovaries -> feminisation -> estradiol and progesterone activation

2

Outline sex difference in behaviour and relevant neural substrates Arnold 2009 XY chromosome

XY -> testes, testosterone estradiol -> masculinisation defeminisation -> testosterone activation

3

Introduction sex differences

Overlap behaviours male and female

Identification sex differences acknowledges mean differences
Predict very little specific individuals

Sex differences other behaviours less marked those in core sexual identity and orientation

4

Where are the largest differences found in sex differences

Range differences within each sex larger differences between sexes
Largest behavioural sex differences seen in sexual orientation and core sexual identity
Differences not absolute

5

Determinants of sex differences in behaviour and cognition

Sex genes activity different sex hormones and environment/experience all factors differ between males and females factors interact effects on brain result sex differences
Partly mediated sexual dimorphisms in brain or CNS
Result from exposure identical (sexually homomorphic) brain substrates to female or male sex hormones/experiences

6

Outline mating behaviour

Sexually dimorphic
Only act that way
No fluidity
Lordosis response
Hormonal control and relevant neural sexual dimorphisms

7

What are the 3 factors required for heterosexual mating behaviour in mammals

Sufficient level attraction both sides

Sufficient level porceptivity - willingness to mate

Sufficient receptivity - ability mate

Not met no mating

8

What occurs in heterosexual mating behaviour mammals once 3 factors required

Appetitive phase behaviour - courting
Enter consummation phase compilation - enter mounting, intro mission, ejaculation
Lordosis response

9

How is heterosexual mating activation controlled by sex hormones

Testosterone necessary for males
Castrated can’t mate
Female mating isn’t as hormonal dependent
Females dependent attractivity proceptivity and receptivity under control hormonal cycle - menstrual

10

How important is the role of the reproductive and hormonal cycle in female mammals

Important determining sexual behaviour
Particularly in rodents
But gets weaker in primates and weak in humans

11

What are reproductive and hormonal cycles in female mammals controlled by

Hormone release by anterior pituitary gland
Folic stimulating hormone to ovary and growth of follicle triggering cycle
Only 1 point around ovulation animal can procreate
Cycle accompanied changes in hormones

12

When is pregnancy possible in reproductive and hormonal cycles in female mammals

Pregnancy only possible during certain time of cycle around ovulation
Oestrogen and progesterone levels are high
Around ovulation - behavioural Estella
Except for primate females who can mate any time

13

How are female behaviours linked repductive chcle

Linked reproductive cycle and controlled by hormonal fluctuations

14

Are primates still influenced by reproductive and hormonal cycles

Even primates attractiveness receptivity and proceptivity appear be modulated by hormonal cycle

15

What else May hormonal cycles influence

Influence behavioural cognitive and affective functions that not directly related to reproductive behaviour

16

Outline spinal mechanisms relevant to make copulating behaviour in rats - Breedlove and Arnold 1980

Spinal nucleus of bulbocavernosurs - SNB
Collection motor neurons in lower lumbar spinal cord; controls bulbocavernosus muscle at base of Lenin’s

17

Why are motorneurons and muscles necessary in spinal nucleus of bulbocavernosurs Breedlove and Arnold 1980

Motor neurons and muscles necessary for normal penile reflexes important successful copulation

18

What are the direct masculinising effects testosterone

Organisational effects testosterone way effects indirect
Testosterone receptors muscle cells then release trophies factored
Support neurons from spinal cord
Don’t have testosterone these neurons and fibres wither away

19

Interaction nature and nurture testosterone exerts some masculinising effects SNB and sexual behaviour via rat mother - Moore 1992

Rat Mother’s are stimulated lick their male pups more often than females because of testosterone in urine
Licking contributes normal male sexual behaviour and normal number SNB neurons

20

Sex circuits relevant to mating behaviour in rodents

Sex circuits constrain sex hormone receptors
Critical sexually dimorphic mating testosterone for male
Estradiol and progesterone for female

21

Outline sexually dimorphic nucleus of preoptic area SDN-POA relevant mating behaviours in rodents

SDN POA and posterodorsal media amygdala and medial proptic area
Parts bigger in males
Destroy it males don’t copulate
Activated by mating supported increase production in gene association between these areas influence testosterone in copulation mediation

22

Outline ventral nucleus of hypothalamus relevant mating behaviours in rodents

Important females
Medial amygdala both males and females
Dimorphism acts different males to females

23

Outline sexually dimorphic components relevant mating behaviours in rodents

SDN POA - masculinised testosterone during critical perinatal period

MePD volume and cell size depend testosterone action adulthood - activational effect

24

Outline sexual dimorphisms in humans to rodent SNB

Ventrolateral cell group of Onufs nucleus in human spinal cord
Bigger males higher motor neuron count

25

Outline Fliers and Swaab 1985 study sexual dimorphisms in human preoptic area of hypothalamus

One nucleus in POA hypothalamus larger in volume and cell number in males
Nucleus SDN sexually dimorphic. Declines with age

26

Outline Allen et al 1989 study sexual dimorphisms in human preoptic area of hypothalamus

4 nuclei in POA
INAH 1-4
INAH1 correspond SDN Fliers 1985
Not differ between sexes
INAH4 not differ
INAH2-3 not differ between homosexual men and heterosexual women

27

What does INAH stand for according to Allen et al 1989

Interstitial nuclei of anterior hypothalamus

28

What occurs result INAH2-3 according to Allen et al 1989

INAH2-3 not differ between homosexual men and heterosexual women

29

Outline LeVay 1991 study on sexual dimorphisms in human preoptic area hypothalamus

Relationship between size nuclei and sexual preference no significant sex differences INAH1,2,4
INAH3 larger heterosexual men than women
Did not differ between homosexual men and heterosexual women

30

What are the effects of INAH3 according to LeVay 1991

INAH3 larger heterosexual men than women
Did not differ between homosexual men and heterosexual women