mind-brain identity theory, ‘brain-sex’ theory of transsexualism and the dimorphic brain (Blog Post)

Description
mind-brain identity theory, ‘brain-sex’ theory of transsexualism and the dimorphic brain (Blog Post)

Please download to get full document.

View again

of 5
All materials on our website are shared by users. If you have any questions about copyright issues, please report us to resolve them. We are always happy to assist you.
Information
Category:

Slides

Publish on:

Views: 0 | Pages: 5

Extension: PDF | Download: 0

Share
Tags
Transcript
  Simon van Rysewyk  'think and wonder, wonder and think'  mind-brain identity theory, ‘brain-sex’ theory of transsexualism and the dimorphic brain April 27, 2013 in 'Brain-Sex Theory', Consciousness, Dimorphic Brain, Gender Identity, Mind-Brain Identity Theory,  Neuroscience   , phenomenal consciousness   , Philosophy   , Research, Science, Simon van Rysewyk    , Transsexualism | Tags: 'brain-sex' theory   , consciousness,dimorphic brain, neuroscience,  philosophy, research, science, simon van rysewyk , thinking (Edit   ) Introduction According to an influential neuroscientific theory, gender identity is encoded in the brain during intrauterinedevelopment. The brain is thought to develop in the male ‘direction’ through a surge of testosterone on nervecells; in the female ‘direction’ this surge is absent (e.g., Savic et al. 2011; Swab, 2007). Call this the ‘standardview of gender identity’. The standard view of gender identity offers a plausible explanation of transsexualism. Since sexual differentiation of the brain occurs in the second half of pregnancy, and sexualdifferentiation of the sexual organs occurs in months 1-2 of pregnancy, transsexuality may occur. The relativemasculinzation of the brain at birth may not reflect the relative masculinization of the genitals (e.g., Bao &Swab, 2011; Savic et al. 2011; Veale et al. 2010). According to the standard view, transsexualism is entirelydependent on, and thereby reduces to, specific neurophysiological changes that occur during intrauterine growthin two interconnected organ types (i.e., brain and genitals).The reductive nature of the standard view of gender identity is compatible with mind-brain identity theory in philosophy of mind and consciousness. Mind-brain identity theory claims that mental states are identical to brain states. Concerning gender identity, mind-brain identity theory claims that a person’s gender identity isidentical to neurophysiological mechanism. A strong and profound implication of this view is that a person’sindubitable sense of being a woman or a man is nothing more than the operations of neurophysiology encodedduring intrauterine growth. Mind-brain identity theory contrasts with philosophies of mind which propose thatminds are dependent but still somehow ‘more than’ the body on which they depend. Brain-Sex Theory of Transsexualism and Mind-Brain Identity According to the strong version of ‘brain-sex’ theory of transsexualism, transsexualism is nothing more than(one and the same as) a specific neuranatomical (i.e., structural) intersex type, in which one or more sexually  dimorphic brain areas are incompatible with bological sex. The theory therefore assumes that the relationship between transsexualism and neurophysiology is one of identity. Gender identity reduces to neurophysiology.Thus, there is a specific neuroanatomical type for female gender identity in male-to-female (MTF) transsexuals,and a specific neuroanatomical type for male gender identity in female-to-male (FTM) transsexuals. The mostcompelling neuroscientific evidence in support of an identity view of transsexualism comes from Kruijver et al.(2000) and Zhou et al. (1995). Neuroscientific Evidence for Brain-Sex Theory of TranssexualismZhou et al. (1995) Zhou et al. (1995) observed that a group of neurons in the hypothalamus, the central subdivision of the bednucleus of the stria terminalis (BSTc), was sexually dimorphic in humans. Zhou et al. found that the averagevolume of the BSTc in postmortem males was roughly 44% larger than in females. However, in 6 male-to-female (MTF) transsexuals who had feminizing hormone treatment, the average volume of the BSTc was withinthe typical female range. The authors found that the 6 transsexuals they investigated varied in their sexualorientations and inferred that there was no relationship between BSTc size and the sexual orientation of transsexuals. I assume that this assertion implies that transsexual sexual orientation and BSTc size are not typeidentical; that is, they are not the same type. Finally, further postmortem investigations conducted in a smallnumber of nontranssexual patients with abnormal hormone levels, led Zhou et al. to reason that the smallvolume of the BSTc in MTF transsexuals cannot be explained by adult sex hormone levels” (p. 70). Thus, thereappears to be a relationship of identity between transsexualism and small BSTc volume. They are one and thesame. Kruijver et al. (2000) Kruijver et al. (2000) conducted a follow-up study in which they investigated the number of neurons in theBSTc rather than its volume. The authors examined tissue from the same 6 MTF transsexuals studied by Zhouet al. (1995). They also studied nerve tissue from one female-to-male (FTM) transsexual and from an 84-yr-oldman who “had very strong cross-gender identity feelings but was never . . . sex-reassigned or treated . . . withestrogens” (p. 2039). The authors found that BSTc neuron number was even more sexually dimorphic thanBSTc volume; namely, the average BSTc neuron number in males was 71% higher than in females. Once again,the 6 MTF transsexuals showed a sex-reversed identity pattern, with an average BSTc neuron number in thefemale range. BSTc neuron number was also in the female range in the untreated gender dysphoric male andwas in the male range in the FtM transsexual. Again, the putative sexual orientation of the MTF transsexualsappeared to make no difference. In contrast to the claims of the standard view of gender identity, data from thefew nontranssexual patients with abnormal hormone levels led Kruijver et al. (2000) to conclude that “hormonalchanges in adulthood did not show any clear relationship with the BSTc . . . neuron number” (p. 2039). Neuroscientific Objections to Brain-Sex Theory of TranssexualismChung et al. (2002) Brain-sex theory of transsexualism faces several neuroscientific challenges. Chung et al. (2002) found thatsignificant sexual dimorphism in BSTc size and neuron number does not develop in humans until adulthood.However, most MTF transsexuals self-report that their feelings of gender dysphoria began in early childhood(e.g., Lawrence, 2003). Since MTF transsexuals have not yet become sexually dimorphic by the time cross-gender feelings have become obvious, it is unlikely that BSTc volume and neuron number can be aneuroanatomical signature identifiable with gender identity. However, Chung et al. (2002) speculate that foetalor neonatal hormone levels could influence gender identity and could also produce changes in BSTc synapticdensity, neuronal activity, or neurochemicals that may not affect BSTc volume or neuron number immediately, but may do so during adulthood. I am not aware of any evidence in support of this hypothesis. In any event,mind-brain identity theory can agree with Chung’s et al. (2002) speculation. Mind-brain identity theory is  neutral on whether ‘brain characteristics’ will be macro or micro, or both, or what their specific developmentaleffects will be. Gender identity might be a state of the entire brain, synapses, or multiple, interacting physiological systems. Macro/microreductionism is optional, not required. Finally, Chung et al. (2002)speculate that inconsistency between an individual’s gender identity and biological sex might likely affect adultBSTc size and neuron number by some yet unknown mechanism or mechanisms. Given that neuroscience is ina very early stage of understanding gender identity, the implication that more time is needed to understandtranssexualism appears prudent. Joel (2011) Joel (2011) challenges an implicit assumption in the standard view of gender identity; namely, human brains areone of two types – ‘male’ or ‘female’ – and that the differences between these two types subserve subtypedifferences between men and women in gender identity and transsexualism. According to Joel (2011), thisassumption is true only if there is robust correspondence (i.e., high statistical correlation) between the‘male’/’female’ type of all of the brain characteristics in a single brain. It turns out there isn’t. As Joel pointsout, concerning most documented sex brain differences, there is overlap between the distributions of the twosexes (e.g., Juraska, 1991; Koscik et al. 2009). Neuroanatomical data also reveal that sex interacts with other factors during the intrauterine period and throughout life to determine brain structure (e.g., prenatal exposure to psychoactive drugs, early handling, rearing conditions, maternal separation, acute and chronic postnatal stress).Human brains therefore are a dynamic heterogeneous mosaic of ‘male’ and ‘female’ brain characteristics thatcannot be type identified on a simple continuum between a ‘male type brain’ and a ‘female type brain’ (Joel,2011). Thus, brains are not type sexed, but type intersexed; sexually multi-morphic rather than dimorphic.Joel’s theory is compatible with brain-sex theory of transsexualism since both theories claim that transsexualismis intersexual, but incompatible because it denies what brain-sex theory asserts; namely, in transsexualism, oneor more sexually dimorphic brain areas are incompatible with bological sex. Thus, Joel’s view rejects thestronger claim that gender is type identical with the sexually dimorphic brain. Accordingly, we cannot predictthe specific properties of ‘male/female’ brain characteristics of an individual based on her/his sex. However,Joel’s view implies the weaker consequence that, on average, we can predict that females will have more braincharacteristics with the ‘female’ type than with the ‘male’ type (vice versa for FTM transsexuals), and maleswill have more brain characteristics with the ‘male’ type than with the ‘female’ type (vice versa for MTFtranssexuals). Whether two individuals are similar or not is dependent on the similarity in the details of their  brain mosaic; not on the quantity  of ‘male’ and ‘female’ characteristics. This means that two similar individualsshare characteristics of the same ‘brain mosiac’ type – they have the same type. Brains of the same type must possess the characteristics and properties typical of the type, but that does not imply that they all be exactlysimilar to one another. This implication is compatible with mind-brain identity theory. References Bao, A. M., & Swaab, D. F. (2011). Sexual differentiation of the human brain: relation to gender identity,sexual orientation and neuropsychiatric disorders.  Frontiers in neuroendocrinology , 32 (2), 214-226.Chung, W. C., De Vries, G. J., & Swaab, D. F. (2002). Sexual differentiation of the bed nucleus of the striaterminalis in humans may extend into adulthood.  Journal of Neuroscience, 22 , 1027-1033.Hines M. (2004).  Brain Gender.  Oxford: Oxford University Press.Koscik, T., O’Leary, D., Moser, D. J., Andreasen, N. C., & Nopoulos, P. (2009). Sex differences in parietal lobemorphology: relationship to mental rotation performance.  Brain Cognition,   69 , 451–459.Kruijver, F. P., Zhou, J. N., Pool, C. W., Hofman, M. A., Gooren, L. J., & Swaab, D. F. (2000). Male-to-femaletranssexuals have female neuron numbers in a limbic nucleus.  Journal of Clinical Endocrinology and etabolism, 85 , 2034-2041.  1 comment Comments feed for this articleOctober 3, 2015 at 11:21 am doro (edit) interesting article! See more about thisin the neuroscience conference 2016:http://www.hauskreistag.de/drupal7/congressReplyJoel, D. (2011). Male or female? Brains are intersex.  Frontiers in integrative neuroscience , 5 , 57.Juraska J. M. (1991). Sex differences in “cognitive” regions of the rat brain. Psychoneuroendocrinology 16,105–109. doi: 10.1016/0306-4530(91)90073-3.Lawrence, A. A. (2003). Factors associated with satisfaction or regret following male-to-female sexreassignment surgery.  Archives of Sexual Behavior, 32 , 299-315.Savic, I., Garcia-Falgueras, A., & Swaab, D. F. (2010). 4 Sexual differentiation of the human brain in relation togender identity and sexual orientation.  Progress in Brain Research , 186  , 41-65.Swaab, D. F. (2007). Sexual differentiation of the brain and behavior.  Best Practice & Research Clinical  Endocrinology & Metabolism , 21 (3), 431-444.Veale, J. F., Clarke, D. E., & Lomax, T. C. (2010). Biological and psychosocial correlates of adult gender-variant identities: a review.  Personality and Individual Differences , 48 (4), 357-366.Zhou, J. N., Hofman, M. A., Gooren, L. J., & Swaab, D. F. (1995). A sex difference in the human brain and itsrelation to transsexuality.  Nature, 378 , 68-70. SHARE THIS:   Press ThisFacebookPinterestMore Occasionally, some of your visitors may see an advertisement here.Tell me more | Dismiss this message         Reblog Like 3 bloggers like this.   RELATED Links between the intrauterine theoryof gender identity, transsexualismand mind-brain-body identitymind-brain identity - evidence fromtranssexualismRobot Pain by Pentti Haikonen  LEAVE A REPLY Enter your comment here...
Related Search
We Need Your Support
Thank you for visiting our website and your interest in our free products and services. We are nonprofit website to share and download documents. To the running of this website, we need your help to support us.

Thanks to everyone for your continued support.

No, Thanks