Neuro-biology of trans-sexuality : Prof. Robert Sapolsky

Step-by-Step Tutorial: Understanding the Neurobiology of Sexual Orientation and Transsexuality

1. Introduction to the Neurobiology of Sexual Orientation:

   • The neurobiology of sexual orientation in women is a less studied area compared to men.
   • Two endpoints have been identified so far: finger ratio and the auto-acoustic reflex.

2. Finger Ratio and Sexual Orientation:

   • Gay women tend to have a finger ratio more typical of straight men.
   • The ratio of the second to fourth finger is often used as an indicator.

3. Auto-acoustic Reflex and Sexual Orientation:

   • Another indicator is the auto-acoustic reflex, which shows differences between gay and straight individuals.

4. Evolution of Views on Transsexuality:

   • Transsexuality was previously considered a domain of psychopathology.
   • Similarly to homosexuality, it was classified as a psychiatric disorder until the early 1970s.

5. Neurobiology of Transsexuality:

   • Studies have shown differences in brain regions such as the bed nucleus of the striae terminalis.
   • Gender differences in neurotransmitter levels have been observed, with males having higher levels.

6. Brain Differences in Transsexuals:

   • Research has shown a reliable difference in brain regions in transsexual individuals.
   • The size of certain brain regions aligns more with the gender they identify with rather than their birth sex.

7. Hormones and Brain Changes in Transsexuals:

   • Studies have looked at brain changes in transsexuals who underwent gender reassignment surgery.
   • Brain differences were not solely attributed to hormone treatments but rather to the individual's persistent gender identity.

8. Landmark Study on Transsexuality:

   • A study by Dutch scientists highlighted that transsexualism is about individuals having the wrong gendered body.
   • This challenges previous notions of transsexualism being a different gender than what individuals truly are.

9. Implications of the Study:

   • The study suggests that transsexual individuals may chromosomally align with their identified gender in various aspects.
   • The study has implications for understanding gender identity and the neurobiology of transsexuality.

10. Phantom Limb Sensations in Transgender Individuals:

    • Comparisons have been made between phantom limb sensations in cisgender men and transgender individuals.
    • Transgender individuals who undergo gender confirmation surgery show a lower rate of phantom sensations compared to cisgender men who lose their penis due to cancer.

11. Moving Forward:

    • The research on the neurobiology of sexual orientation and transsexuality provides insights into understanding fixed action patterns of sexual behavior.
    • Further exploration is needed to understand the environmental triggers that influence neural responses in different brain regions.

By following these steps, you can gain a comprehensive understanding of the neurobiology of sexual orientation and transsexuality as discussed in the video by Prof. Robert Sapolsky.