1. Sex Hormones,
the brain
and behavior

2. Definitions of Sex Genetic Gonadal Hormonal Morphological
Behavioral (gender role behavior)
Identity

3. Control of Sex Hormones
neural inputs
Hypothalamus
Indirect
Loop
Short
Loop
GnRH
Adenohypophysis
LH, FSH
Direct
Loop
Testes or Ovaries
Testosterone
or Estrogen &
Progesterone
Target tissues

4. Sexual Dimorphisms Phenotypic differences between males and females
They can be:
anatomical
physiological
behavioral
cognitive
They can be:
qualitative
quantitative

5. Effects of Sex Hormones
Organizational Effects
structural
sensitive period
irreversible
masculinization/defeminization
Activational Effects
act on existing structure
no sensitive period
reversible

6. testes differentiate
ovaries differentiate

8. Bipotential tissues: Undifferentiated tissue
that can differentiate into either a male or
female form.
Sexual Dimophisms: Structures, functions
or behaviors that differ qualitatively or
quantitatively between the sexes.

9. Prototypical Experiment
(Males)
Castrate male hamster at birth
(before period of brain differentiation)
Test in adulthood
inject with testosterone
place with receptive female
male typical behavior low
mounting, intromission
(ejaculation not possible)
inject with estrogen and progesterone
place with male
female-typical behavior high
darting, ear-wiggling, lordosis

10. Prototypical Experiment
(Females)
Neuter female hamster at birth and
inject with testosterone
(before period of brain differentiation)
Test in adulthood
inject with testosterone
place with receptive female
male typical behavior high
(mounting)
inject with estrogen and progesterone
place with male
female-typical behavior low
(ear-wiggling, darting, lordosis)

14. Kelley, D.B. (1988) Ann. Rev. Neurosci.,
11,

15. ♂

16. ♀

17. Differentiation of the Brain
Two processes
both are dependent on fetal androgens
Masculinization
Induction of male characteristics
Defeminization
Suppression of female characteristics

18. Estradiol is the sex
hormone primarily
responsible for
masculinization of
the brain.

19. Why aren’t all females masculinized? α-fetoprotein
binds to estradiol extracellulary
and prevents entry into cell

24. Steroid Hormones

25. cholesterol

26. Control of Sex Hormones
neural inputs
Hypothalamus
Indirect
Loop
Short
Loop
GnRH
Adenohypophysis
LH, FSH
Direct
Loop
Testes or Ovaries
Testosterone
or Estrogen &
Progesterone
Target tissues

27. Control of Stress Hormones
neural inputs
(limbic system)
Hypothalamus
Indirect
Loop
Short
Loop
CRF
(aka CRH)
Adenohypophysis
Corticotrophin
(aka ACTH)
Direct
Loop
Adrenal Cortex
Cortisol or
Corticosterone
Target tissues
This is usually referred to as the “HPA axis,”
but is now often called the “LHPA axis.”

28. Suppose there is a deficiency of either
estradiol
aromatase
5-alpha
reductase
cholesterol
DHT
Suppose there is a deficiency of either
21-hydroxylase or 11-β hydroxylase.

31. cholesterol

36. estradiol
aromatase
5-alpha
reductase
cholesterol
DHT

37. Testosterone
5-α
reductase
Dihydrotesosterone

39. Sex differences in cognition
Studies of mathematically gifted
Effects of brain damage
Anatomical studies of brain laterality
Functional (fMRI) studies of brain laterality

40. ♂ ♀

41. Benbow 20 year follow-up Benbow, C.P., Lubinski, D., Shea, D.L. &
Eftekhari-Sanjani, H. (2000) Sex differences
in mathematical reasoning ability at age 13:
Their status 20 years later. Psychological
Science, 11,

48. Brain Laterality

50. Meta-analysis of data from 13 studies of unilaterally brain-damaged adult humans
Females
Males
Totals
Left Positive
15/111
(9%)
100/246
(41%)
115/357
(32)%
Right Positive
16/103
(16%)
120/276
(43%)
136/379
(36%)
31/214
(14%)
220/522
(42%)
Data from:
Inglis, J. & Lawson, J.S. (1981) Sex differences in the effects of unilateral brain damage on intelligence. Science, 212,

51. Cerebral Lateralization
Geshwind’s Theory of
Cerebral Lateralization
Geschwind, N. & Galaburda, A.S. (1987)
Cerebral lateralization. Cambridge, MA:
MIT Press

52. McManus, I.C. & Bryden, M.P. (1991) Geschwind’s theory of cerebral lateralization:
Developing a formal, causal model. Psych. Bull., 110,

53. Control of Sex Hormones
neural inputs
Hypothalamus
Indirect
Loop
Short
Loop
GnRH
Adenohypophysis
LH, FSH
Direct
Loop
Testes or Ovaries
Testosterone
or Estrogen &
Progesterone
Target tissues

54. Activational Effects of Sex
Hormones on Cognition
perform well on verbal and motor tasks
poorly on spatial tasks
perform well on spatial tasks,
poorly on motor and verbal tasks

55. de Lacoste-Utamsing, C. & Holloway, R.L. (1982)
Splenium
de Lacoste-Utamsing, C. & Holloway, R.L. (1982)
Sexual dimorphism in the human corpus callosum.
Science, 216,

58. Gladue, Green
& Hellman (1983)
Science, 225,

59. Gladue, Green & Hellman (1983) Science, 225, 1496-1499.

61. LeVay, S. (1991) Science, 253,

63. Size related to sexual identity
not sexual orientation