Sex Hormones, the brain and behavior

1. Sex Hormones, the brain and behavior

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

3. neural inputs Control of Sex Hormones 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, 225-251.

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. neural inputs Control of Sex Hormones 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 CRF (aka CRH) Short Loop 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. cholesterol 5-alpha reductase aromatase estradiol DHT Suppose there is a deficiency of either 21-hydroxylase or 11-β hydroxylase.

31. cholesterol

36. cholesterol aromatase 5-alpha reductase estradiol 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, 474-480.

48. Brain Laterality

50. Meta-analysis of data from 13 studies of unilaterally brain-damaged adult humans Data from: Inglis, J. & Lawson, J.S. (1981) Sex differences in the effects of unilateral brain damage on intelligence. Science, 212, 693-695.