Your Brain

• Posted by Cristine Jennifer Shye. BL. B/acc March 27, 2020 Filed in Member's Blogs 2,387 views
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  1. Introduction The role of the androgen receptor in CNS masculinization or the absence of same in male feminisation
  
  The medial posterior region of the bed nucleus of the stria terminalis (BSTMP) and the locus coeruleus (LC) show opposite patterns of sexual dimorphism. The BSTMP in males is greater in volume and number of neurons than in females (male N female) while in the LC, the opposite is true (female N male). To investigate the possible role of the androgen receptor (AR) in the masculinization of these two structures, males with the testicular feminization mutation (Tfm) were compared to their control littermate males. No differences were seen in the number of neurons of the BSTMP between Tfm and their control littermate males, while in the LC, Tfm males have a greater number of neurons than their control littermate males. These results show that the AR is involved in the control of neuron number in the LC but not in the BSTMP. Results based on the LC suggest that when females have a larger brain area than males, masculinization in males may be achieved through the AR, with androgens perhaps decreasing cell survival.
  
  Sex differences in the mammalian brain have two main characteristics: they often occur in neural circuits related
  to reproductive physiology and behavior and they are seen in two opposite morphological patterns In one
  pattern, males have greater volumes and/or number of neurons than females (male N female), while in the other, the opposite is true (female N male) Existing evidence suggest that gonadal androgens are involved in the development of sex differences in structures that are larger in males than in females,

   Cristine:- So is it safe to say the percentage difference between the number of neurons BSTMP M to F and F to male affect the degree of GID and could possible it result in dual gender identity when more or less balanced? with no predominate influence.

   The scientific literature has already come to a consensus on the existence of cognitive sex differences, especially with regard to spatial ability. Both neural/hormonal and social factors contribute to those differences. See Diane Halpern's "Sex Differences in Cognitive Abilities".

  Stereotypes, including gender stereotypes, are mostly accurate. So saying that some view or conclusion is a gender stereotype is not a real criticism. See Lee Jussim's "Social Perception and Social Reality: Why Accuracy Dominates Bias and Self-Fulfilling Prophecy".

  Finally, let's assume the real reason why women have bigger corpus callosums is that they have smaller brains. Does the relation between sex and corpus callosum size cease to exist? No. Women on average will still have larger corpus callosums and all the (presumed) behavioural/cognitive characteristics associated with it.

   If you look at the sexual dimorphism from an evolutionary perspective, this makes perfect sense. In early human societies, men went out to hunt while women stayed in the village (with very few exceptions).

  The traits that made men more successful were those that allowed them to be better hunters and warriors: so coordinated action, perception of environmental opportunities and dangers. For the women in the village, their success is more dependent on "politics" and relationships. Instead of organizing hunts, the successful woman is one who is well liked by people and use strong communication skills and wits to solve problems (and not braun since they will lose to the stronger males).

  Thus over time, as the traits that marks a successful man and woman differs, it makes sense that there should be sexual dimorphism in brain structures.

   Which in turn is a probable and logical cause for some brain structure difference in male to female transexuals.

   

   

   Garcia-Falgueras A, Swaab DF Endocr Dev. 2010;17:22-35

   The fetal brain develops during the intrauterine period in the male direction through a direct action of testosterone on the developing nerve cells, or in the female direction through the absence of this hormone surge. In this way, our gender identity (the conviction of belonging to the male or female gender) and sexual orientation are programmed or organized into our brain structures when we are still in the womb. However, since sexual differentiation of the genitals takes place in the first two months of pregnancy and sexual differentiation of the brain starts in the second half of pregnancy, these two processes can be influenced independently, which may result in extreme cases in trans-sexuality. This also means that in the event of ambiguous sex at birth, the degree of masculinization of the genitals may not reflect the degree of masculinization of the brain. in fact in the examination of male to female transexuals the brain composition would suggest varying degrees  uf under masculisation vegring on the near total feminisation. There is no indication that social environment after birth has an effect on gender identity or sexual orientation