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Hormones & Behavior > Chapters 4: Sex Differences in Animals & Humans > Flashcards

Chapters 4: Sex Differences in Animals & Humans Flashcards

1
Q

Sexual dimorphisms in human behavior

A 
Men are more likely to have:
Visuospatial abilities
Aggression
Schizophrenia
Autism

Females are more likely to have:
Verbal abilities
Nurturing behavior
Depression

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2
Q

Nature vs Nurture

A

Nature (genes, hormones)
vs
Nurture (social factors, learning, culture)

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3
Q

Sex matters: “60 Minutes” investigates men, women and drug dosage

http://www.amara.org/en/videos/
H2FdrVnvT8Mn/info/
sex-matters-60-minutes-investigates-men-women-and-drug-dosage/

A

Early last year, the FDA made a surprising announcement when it cut the recommended dose of the nation’s most popular sleep drug, Ambien, by half - but only for women. Lesley Stahl reports on how much different men and women are, when it comes to medicine.

Women metabolize the drug more slowly than men.

Male and female bodies are very different, and not just on a hormonal or gonadol level, most organs, including the heart and lungs are different between the sexes.

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4
Q

CO-ED LAB RATS study
on The Colbert Report

http://thecolbertreport.cc.com/
videos/el90zp/co-ed-lab-rats

A

Scientists discover that the tradition of testing medicine exclusively on male subjects can lead to negative side effects for women.

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5
Q

Patterns of play behavior

A

diferences in girl and boy play behavior.

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6
Q

Sex differences in the brain are Categorized as:

A

Volumetric: size differences of specific brain regions or nuclei

Connective: type or number of synapses or the size of a particular type of projection within the brain

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7
Q

Spinal Nucleus of the Bulbocavernosus (SNB)

A

Region of the spinal cord

Motorneurons that innervate muscles attached to the penis that control erection

Sex difference in neuron number and dendritic arbor

Onuf’s nucleus

During fetal development, androgens spare muscles and SNB

Aromatization NOT important for masculine development of this system

Environmental effects can also influence SNB sex difference, i.e. maternal licking

maternal licking of male pups can masculinize the circuit of the spinal cord

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8
Q

Sex differences in mammalian brain

A

Raisman & Field (1971, Science)

First report of sex difference in brain

Very small connective difference in rat hypothalamus (MPOA)

Used EM to count and categorize synapses in the MPOA

Males: more shaft synapses
Females: more spine synapses

Hormone manipulations immediately after birth can affect this pattern of connectivity

Males castrated 1 day after birth
had a feminine pattern of the dendritic spine activity

Females injected with T shortly
after birth had a masculine pattern

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9
Q

The SNB is larger and has more complex neurons in _______?

A

males

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10
Q

Onuf’s nucleus

A

human SNB

It’s a similar area, called SNB in rats and Onuf’s nucleus in humans

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11
Q

T/F:
The SNB in females, and the muscles that control erectile function, are diminished in size or completely absent in adult female rats.

A

true

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12
Q

SNB sex differences are much _____ pronounced in humans

A

much more pronounced

side note- in humans it contracts rhythmically during erection and ejaculation

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13
Q

What happens to SNB motorneurons in female rats?

A

the SNB neurons die in females around the time of birth.

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14
Q

What happens to SNB motorneurons in male rats?

A

androgen treatment spares the muscles and secondarily spares the SNB, this happens in fetal development

males will lose the spare muscles and SNB unless androgens save them

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15
Q

Is the SNB sex difference volumetric or connective?

A

volumetric

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16
Q

Does the SNB depend on androgens or estrogens?

A

androgens

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17
Q

T/F:

Aromatization is NOT important for masculine development of the SNB system

A

true

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18
Q

Environmental effects on SNB size:

A

maternal licking of male pups can masculinize the circuit of the spinal cord

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19
Q

Are androgen treatments effective once the muscles responsible for penile erection have atrophied?

A

No, once the muscles have regressed, androgen treatment cannot restore the muscle cells so the critical period of androgen effectiveness in sparing motoneurons in the SNB is defined by the rate of muscular atrophy.

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20
Q

______ prevent cell death in the SNB

A

Androgens

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21
Q

First reported sex difference in the mammalian brain?

A

Very small CONNECTIVE difference in rat hypothalamus (MPOA)

Males: shaft synapses are larger than spine synapses
Females: the opposite

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22
Q

Males castrated 1 day after birth had a ______ pattern

A

feminine pattern of the dendritic spine activity

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23
Q

Females injected with T shortly after birth had a ______ pattern

A

masculine pattern

24
Q

The SDN-POA (Sexually Dimorphic Nucleus of the Preoptic Area) is bigger in _____ than in _____ .

A

males than in females.

25
Q

The sex difference in the size of the SDN-POA is due to a _______ number of cells in females and castrated males; androgens, or more precisely their estrogenic metabolites, protect neurons from apoptosis, programmed cell death.

A

decreased

26
Q

Rats with complete androgen insensitivity syndrome (testicular feminization) exhibit what?

A

a deficiency in androgen receptors but normal estrogen receptors and display female typical genitalia but male-typical SDN-POA

27
Q

Gorski et al (1978)

A

Rat tissue sections stained with Nissl

Volumetric sex difference in SDN-POA

28
Q

SDN-POA

A

T permanently enlarges the SDN-POA but only if given during critical period in early life

Difference in cell number; cell death

Estrogens (aromatized from testosterone) protect neurons from cell death and masculinize the SDN-POA

Males who are castrated neonatally have an SDN that is female in size. Castrating male rats in adulthood does not alter the size of the POA.

29
Q

Gonadal hormones and developmental apoptosis:
regional specificity.

SDN vs. nearby AVPV

A

Giving testosterone to a fetal female rat caused them to develop this male-typical brain SDN

30
Q

MANY mechanisms produce organizational sex differences in the brain (and probably behavior)

A 
DNA Methylation
Histone Acetylation
Neurogenesis
Cell Death or Survival
Spinogenesis
Neuronal Migration.
31
Q

Regional specificity in synthesis (and receptors) produce a complex mosaic

A

Remember: Steroid hormones are synthesized in the brain!

32
Q

First reported that women have smaller brains than men

A

However – brain size relative to body size is not different !

33
Q

Sex differences in human brain

A

Increased folding of the brain surface in women

Global cerebral blood flow is greater in women

Women have a higher proportion of gray matter
men have a higher percentage of white matter

Neurochemical differences

Genetic/epigenetic differences

In some studies, nuclei of the human POA subdivided into interstitial nucleus of the anterior hypothalamus (INAH) 1-4

34
Q

Preoptic Area (POA)

A

…

35
Q

INAH-3 in humans

A

Cause or consequence?

36
Q

Organizational effects in humans

A

Hormones act to ‘prepare’ the brain to direct sex-specific reproductive behaviors
…so brain (and body) phenotype matches the sex-specific hormone levels the brain will experience later in life and sex-typical behavior will result

WHAT HAPPENS IF THERE IS A MIS-MATCH?

37
Q

Brenda / Bruce Reimer (David)

A

Sad resolution to a sad story

Evolving medical standards to deal with ambiguous genitalia in infants

38
Q

Disorders of Sexual Development:

Treatment and Intervention

A

New medical standards for dealing with disorders of sexual development and ambiguous genitalia:

DO NOT alter genitalia to ‘conform’ or make the problem go away. Wait until the child can decide

DO NOT conceal from child

DO Assign a gender AFTER appropriate genetic and hormonal tests
Diagnose 5-alpha reductase, AIS, etc and predict likely gender identity based on this

39
Q

Organizational effects on human behavior:


Androgens and Congenital Adrenal Hyperplasia

A

Adrenal dysfunction leads to under-production of cortisol and over-production of sex steroids

Females with CAH are exposed to high levels of androgens during early development

What about the brain and behavior of CAH females?

Prenatal androgens and sex-typical play: 
Evidence from CAH

40
Q

Not all sex differences in the brain relate to reproduction:

A

A majority occur in brain regions primarily related to reproductive behavior
Example: hypothalamus, spinal cord nuclei.

Others in brain regions related to reproductive and other behaviors

Amygdala: fear, territorial aggression, SEX
Periaqueductal gray: pain, SEX

…but maybe not. Sex differences in non-reproductive behaviors, too, such as spatial reasoning (hippocampus) and language (frontal cortex)

41
Q

Organizational effects on human behavior:


Art in girls and boys—nature or nurture or both?

A

motifs in coloring

42
Q

A sampling of human sex differences in cognition:

A

Males better:
Spatial
Aiming
If only 60 percent of seedlings will survive, how many must be planned to obtain 660 trees?

Females better:
Matching
Words
2 (15 + 3) + 12 – 15/3 = ?

43
Q

Men and women use different parts of their brains to solve similar language tasks (rhyming)

A

Female pattern is bilateral; greater lateralization in males

44
Q

Activational Effects in Humans

A

Individual differences in androgen levels (activational) predict performance on some tasks

There seems to be a bell curve of how much testosterone and how well they do the SPATIAL task

And there’s a line slope with PERCEPTUAL speed, where the lower the testosterone, the better they do

45
Q

Studying sex differences in humans is difficult because:

A

1) Overlap and effect size
2) Ethics of manipulating hormones

Must take advantage of hormone manipulations for other reasons

Transexual transition….
Male to female: administered androgen receptor blockers or estrogens
Female to male: administered androgens

46
Q

Female to male transexuals

A

Female to male transexuals taking testosterone during transition.

fMRI during transition to see brain structure changes over 4 weeks

Decrease volume due to testosterone

47
Q

Transexual studies

A

Increased inter-hemisphere connectivity in Male to Female transexuals

Increased intra-hemisphere connectivity in female to male transexuals

Total brain volume—down in male to female transexuals on HRT

Ventricular volume—up in male to female transexuals; down in female to male transexuals

Hypothalamus size- down in male to female transexuals (match females)

48
Q

MALE –> FEMALE transexuals

A

on anti-androgen or estrogen treatment

49
Q

Animal Models for Sexually Dimorphic Behaviors

A

Play behavior in primates
Birdsong
Urinary posture in canines

50
Q

Sex differences in play in non-human primates are Very similar patterns to those seen in CAH and in human girls and boys

A

Rough-and-tumble play is more common with young male primates

51
Q

Rough-and-Tumble Play in Primates

A

Males engage in more play behavior than females, a larger proportion of their play involves simulated fighting or rough-and-tumble play

Sex difference in play is behavior organized prenatally and is not dependent on the activational effects of hormones

Pseudohermaphrodites were females treated in utero with androgens

52
Q

Birdsong

A

Song is a learned vocalization

Stages of song learning:
1. Sensory stage
(listen)
2. Sensory motor stage
(Listen and try)
3. Crystallization
(Become proficient)

Sex difference in amount of singing is species specific

Sex differences in birdsong reflect sex differences in brain regions that control singing

53
Q

Song circuit

A

AREA X: Like the Basal Ganglia

HVC: PreMotor Cortex

Efferent motor pathway: song production

Anterior forebrain pathway: song learning

54
Q

Zebra finch

A

In species where there is a large sex difference in the amount of song, brain structures involved in song are sexually differentiated.

Area X can’t be discerned in females

HVC & RA: males > females

Due to larger, more numerous and scattered neurons in these nuclei

Sex differences in brain and singing are either organized by estrogen or activated by androgens

Gurney & Konishi (1980, Science)
If females treated with estradiol after hatching, and with T in adulthood:
RA and HVC almost the size of untreated males
They sing!

Organizational /activational hypothesis in action

55
Q

But…

A

Castration after hatching does not demasculinize the song system or singing behavior

Treating hatchling males with antiestrogens, antiandrogens or aromatase inhibitors does not demasculinize males

No consistent sex differences in chick plasma estradiol or testosterone (but brain?)

No sex differences in brain estrogen receptors or brain aromatase

Treating genetic females with an aromatase inhibitor during development will produce a genetic female with testes…

…testes insufficient to masculinize female brain!

56
Q

Perhaps a gene on the sex chromosomes play a role ?

A

Both sides of brain exposed to same hormonal milieu

Perhaps the sex chromosomes compensate for some hormone issues

Normal male song and copulation

57
Q

Urinary posture in canines

A

Sexually dimorphic

Female dogs treated with T in utero and immediately after birth –> had masculinized genitalia and male urinary posture

Males castrated as puppies still shift from the juvenile to male position when normal males do

Male typical posture organized by perinatal androgen exposure but does NOT require hormones for activation

Changes in perceptual processing of environment too, seem to be organized. Male adults prefer to urinate on things in vertical orientation of at least a certain height

Hormones & Behavior (6 decks)

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