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Tags: Reverted Mobile edit Mobile web edit |
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| ==Neuroscience==
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| *''[http://www.sciencedirect.com/science/article/pii/S030698771200062X Alternating gender incongruity: A new neuropsychiatric syndrome providing insight into the dynamic plasticity of brain-sex]'' - [http://www.researchgate.net/profile/Laura_Case2 Case, L.K.] & [http://en.wikipedia.org/wiki/Vilayanur_S._Ramachandran Ramachandran, V.S.], 2012.
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| ::;Summary:
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| <blockquote>An online survey of 32 [[bigender]] individuals was conducted. Questions concerned whether they had ever been diagnosed with a psychiatric disorder, whether or not they could predict their cycles in gender, how often they switched between genders, and whether or not they experienced the sensation of 'phantom' breasts or genitalia that cycled along with gender.</blockquote>
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| ::;Key Findings:
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| ::*A higher than expected rate of [http://en.wikipedia.org/wiki/Bipolar_disorder bipolar disorder] was found among participants; however, this was not sufficient to explain experiences of cycling gender, nor was any other psychiatric disorder.
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| ::*10 of 32 participants reported that their switches were predictable.
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| ::*Of those surveyed, 14 switched daily, or multiple times a day; 9 switched weekly or several times a week; 6 switched monthly or several times a month; and 3 switched several times a year.
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| ::*21 of 32 participants reported experiencing phantom body parts that matched their current gender state.
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| ::;Limitations:
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| ::*There is currently no evidence for or against the theories proposed here; this paper appears to be the first formal scientific investigation of bigender identity, and as a result, the discussion section is highly speculative.
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| ::;Implications for Future Research:
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| ::*The authors propose several speculative theories of a neurological basis for bigender identity (or 'alternating gender incongruity', as they refer to it):
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| :::*Bigender people may have unusually amplified functional [http://en.wikipedia.org/wiki/Lateralization_of_brain_function hemispheric dominance] patterns; cycling of dominance between hemispheres may lead to the alternate expression of cognitions and emotions that are traditionally considered to be 'male' or 'female'.
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| :::*Alternatively, these alternating patterns of hemispheric dominance may lead to different patterns of [http://en.wikipedia.org/wiki/Sympathetic_nervous_system sympathetic] and [http://en.wikipedia.org/wiki/Parasympathetic_nervous_system parasympathetic nervous system] control, which in turn could result in different patterns of emotional reactivity.
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| :::*Bigender people may have atypical [http://en.wikipedia.org/wiki/Somatosensory_cortex somatosensory body maps], resulting in two or more differently gendered body maps that vie for sensory input.
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| :::*Bigender identity could also be a result of a combination of these causes.
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| ::*More broadly speaking, they acknowledge that there are many levels at which gender and sex can differ - including chromosomes, physical morphology, body image, and "sense of being a man or woman in society" - and that differences in any one of these could underlie a trans* or nonbinary gender identity.
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| ::*The authors also wonder whether alternation of gender states might reflect changes in hormone profiles.
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| ::'''Published In:''' ''[http://www.journals.elsevier.com/medical-hypotheses/ Medical Hypotheses]''
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| ::'''Access:''' Institutional login available
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| ::'''Content Note:''' Contains some problematic language (medicalisation of bigender indentity).
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| *''[https://web.archive.org/web/20170601162157/http://avitale.com/etiologicalreview.htm Current Thinking on the Etiology of Gender Dysphoria]'' - [http://www.avitale.com/ Vitale, A.], 2011.
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| ::;Summary:
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| <blockquote>A very brief review of the evidence for a neurological basis for [[gender dysphoria]], and some informed but speculative discussion of how this neurological basis might emerge during [http://en.wikipedia.org/wiki/Fetal_development fetal development]. The specific findings discussed involve binary trans* participants, but they are potentially relevant to anyone who experiences gender dysphoria.</blockquote>
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| ::;Key Points:
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| ::*There is evidence to suggest that, in the brains of transsexual women, the[http://en.wikipedia.org/wiki/Bed_nucleus_of_the_stria_terminalis#Bed_nucleus_of_the_stria_terminalis bed nucleus of the stria terminalis] (aka BSTc; a region which differs in size between cisgender males and females) is sized within the range typically found in cisgender females.
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| ::*Evidence also shows that, for transsexual women, the number of [http://en.wikipedia.org/wiki/Somatostatin somatostatin]-expressing [http://en.wikipedia.org/wiki/Neuron neurons] in this region of the brain is within the range expected of cisgender females. Conversely, for transsexual men, the number of somatostatin-expressing neurons in this area was more similar to the range found in cisgender males.
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| ::*These findings support the idea that, in people who experience gender dysphoria, the sex characteristics of the brain may be incongruent with other sex characteristics.
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| ::*The development of [http://en.wikipedia.org/wiki/Sexual_dimorphism sexual dimorphism] in utero is highly complex, and there are many stages at which one or many aspects of an individual's sex may become incongruent with the rest:
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| <blockquote>"Once in the fetal brain, testosterone is either metabolized into dihydrotestosterone by an enzyme named 5 alpha reductase or converted to estradiol by an enzyme called aromatase. Counterintuitively, increased estrogen receptor activation is responsible for defeminization while increased androgen receptor activation seems to be responsible for masculinization. All this makes clear that there is nothing straightforward about an individual being born with a gender identity that matches their biological sex."</blockquote>
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| ::*For an individual's brain to develop with a representation of their body as predominantly male, they must not only be exposed to sufficient [http://en.wikipedia.org/wiki/Testosterone testosterone], but this testosterone must also be released with the correct timing, as there is a relatively short time frame in which the brain is susceptible to defeminisation. If this does not occur, the gender map may be "partially imprinted as male". Possible causes of disruption include disorder in the mother's [http://en.wikipedia.org/wiki/Endocrine_system endocrine system], maternal stress, medication, or potentially other substances and/or adverse events. Female gender is less complex to produce, but still potentially vulnerable to disruption.
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| ::*"Gender identity, far from being absolute, appears to occur on a continuum, with most people gathered at either end, the rest being somewhere in between. Feelings of discomfort or complete inappropriateness about one's assigned sex do not mean the individual is wrong or ill. It simply means that the assignment made at birth almost universally on the shape of one's genitals can, on occasion, differ from the unseen brain imprint."
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| ::;Limitations:
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| ::*Only two studies were cited in support of points relating to the BSTc.
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| ::*The samples used in these studies were very small, and there was considerable overlap in the participants used in the two studies.
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| ::*Both studies examined postmortem brains, and the majority of trans* participants had been on hormone replacement therapy during their lifetimes. Findings relating to the BSTc may, therefore, have been due to hormone use rather than an innate marker of gender dysphoria.
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| :::*The authors did attempt to control for this by including a control group of cisgender males with hormonal disorders; however, this control sample was also very small, consisting of only two brains.
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| ::*Only a single transsexual man was studied, so firm conclusions about the brains of transsexual men cannot be drawn from the study described.
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| ::*The discussion of fetal development is purely speculative; no research is cited to support the idea that a neural correlate of gender identity develops in the womb.
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| ::'''Published In:''' ''[https://web.archive.org/web/20170708040718/http://www.thegenderedself.com/ The Gendered Self ''by Anne Vitale'']''
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| ::'''Access:''' Introduction available as a free download; full book available for purchase in physical and ebook formats.
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| ==Law== | | ==Law== |
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