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Hormones & Sexual Behavior

Hormones & Sexual Behavior. Lecture 26. Sexual Behavior: Rats. Controlled by sex hormones Female Proceptive ear wiggling, darting, hopping Receptive - lordosis Male mounts copulates ~. Organizational Effects of Hormones. SDN & SNB Critical periods Humans - prenatal

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Hormones & Sexual Behavior

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  1. Hormones & Sexual Behavior Lecture 26

  2. Sexual Behavior: Rats • Controlled by sex hormones • Female • Proceptive • ear wiggling, darting, hopping • Receptive - lordosis • Male • mounts • copulates ~

  3. Organizational Effects of Hormones • SDN & SNB • Critical periods • Humans - prenatal • Rats - Perinatal • easily manipulated ~

  4. Hormones: Sexual Behavior • Gonadectomy • at birth • Adult males • testosterone  no male behavior • estrogen  lordosis • Adult females • estrogens  no female behavior • testosterone  male behavior ~

  5. Human Sexual Behavior • No stereotypical M & F behaviors • Men are like rats • Testosterone: activational role • Women • Estrogens no activational effects • Testosterone levels correlated with frequency of intercourse ~

  6. Homosexuality • Sex hormones role? • rats - yes • Humans? • no difference in circulating hormones • Learning experiences? • or biologically determined?

  7. Homosexuality • Simon LeVay • Brains of male AIDS victims • Anterior Hypothalamus • Anterior Commissure • Suprachiasmatic nucleus • SDN (rats) • Humans: 3rd interstitial nucleus of the Anterior Hypothalamus • INAH-3 ~

  8. 3d interstitial nucleus • Anterior commissure larger in females • Similar relationship ~ .15 .10 .05 Volume mm3 F H-M M

  9. Homosexuality: 2 Hypotheses • 1. Prenatal androgen levels • low in XY fetuses that gay • high in XX fetuses  lesbian ~

  10. Homosexuality 2 Hypotheses 2. Inherited Genes • MZ twin concordance approx. 50% • DZ twins approx. 20% • Xq28- tip of the X chromosome • 33 of 40 pairs of gay brothers • fetal brain response to androgens ~

  11. Nature vs. Nurture • John/Joan • penis destroyed during circumcision • 1960s - Gender deemed neutral at birth • constructed female genitalia • hormone treatment • 12 yrs old: positive results reported ~

  12. Nature vs. Nurture • By 14 yrs old: living as male • reconstructive surgery • male hormone treatment • married by 25 • Reassessment in 1996 • rejected female role much earlier • Pendulum swings back toward nature • sex/gender not so malleable ~

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