On the Science of Changing Sex

Mars and Venus in Conjunction…

Posted in Brain Sex by Kay Brown on March 30, 2017

Teenage-brainOr, Yes, We CAN Tell Men and Women Apart By Their Personalities

In my last post, we looked at the idea that though the brain is comprised of many areas that individually are only mildly sexually dimorphic the pattern of which adds up to a very sexually dimorphic brain mosaic.  It reminded me of an earlier study in which they found that personality traits were also only mildly sexually dimorphic when examined individually, but the overall personality, the matrix of traits, was also very sexually dimorphic.  That is to say, that men and women, on average, do have different personalities, but no one trait is all that different.

Given that brains and minds are intimately linked, that minds are the function of brains, the fact that both brain mosaic and personality are both individually only mildly sexually dimorphic, but collectively very dimorphic should not surprise us.

The idea that men and women have different personalities has been widely accepted for millenia, but recently has been seriously questioned by feminists and some social scientists and psychologists, most notably Prof. Janet S. Hyde.  But even she, in propounding the “Gender Similarity Hypothesis” did find obviously sexually dimorphic behaviors in humans, as Guidice, et Al remarked,

“Specifically, Hyde found consistently “large” (d between .66 and .99) or “very large” (d≥1.00) sex differences in only some motor behaviors and some aspects of sexuality; “moderate” differences (d between .35 and .65) in aggression”

“…some aspects of sexuality…” Yeah!  Duh!  As in sexual orientation, the single largest sexually dimorphic difference between men and women, also motor behaviors that are highly correlated with sexual orientation.  Finally, aggression; yes, men are more aggressive than women by nature.  But what of the more subtle areas of personality?

In this study, the authors chose to use a very well established personality inventory, the 16PF which underlie the more well known Big Five factor personality inventory.

First, we need to discuss the matter of looking at individual aspects of personality as single variables then averaging this difference between the sexes as the authors pointed out,

“The problem with this approach is that it fails to provide an accurate estimate of overall sex differences; in fact, average effect sizes grossly underestimate the true extent to which the sexes differ. When two groups differ on more than one variable, many comparatively small differences may add up to a large overall effect; in addition, the pattern of correlations between variables can substantially affect the end result. As a simple illustrative example, consider two fictional towns, Lowtown and Hightown. The distance between the two towns can be measured on three (orthogonal) dimensions: longitude, latitude, and altitude. Hightown is 3,000 feet higher than Lowtown, and they are located 3 miles apart in the north-south direction and 3 miles apart in the east-west direction. What is the overall distance between Hightown and Lowtown? The average of the three measures is 2.2 miles, but it is easy to see that this is the wrong answer. The actual distance is the Euclidean distance, i.e., 4.3 miles – almost twice the “average” value. The same reasoning applies to between-group differences in multidimensional constructs such as personality. When groups differ along many variables at once, the overall between-group difference is not accurately represented by the average of univariate effect sizes; in order to properly aggregate differences across variables while keeping correlation patterns into account, it is necessary to compute a multivariate effect size. The Mahalanobis distance D is the natural metric for such comparisons. Mahalanobis’ D is the multivariate generalization of Cohen’s d, and has the same substantive meaning. Specifically, D represents the standardized difference between two groups along the discriminant axis; for example, D = 1.00 means that the two group centroids are one standard deviation apart on the discriminant axis.”

Using Mahalonobis’ D allows us to see the real difference in personalities of men and women taking into account the global pattern of personality traits, rather than one at a time.  From this the authors found,

“We found a global effect size D = 2.71, corresponding to an overlap of only 10% between the male and female distributions. Even excluding the factor showing the largest univariate ES, the global effect size was D = 1.71 (24% overlap). These are extremely large differences by psychological standards.  The idea that there are only minor differences between the personality profiles of males and females should be rejected as based on inadequate methodology.”

‘Gee willikers Mr. Wilson’… that 10% overlap sounds awfully familiar – Oh yeah, that’s similar to that found for the global pattern of the sexually dimorphic mosaic of the brain.  And just as I suggested that this might represent the effect of the non-heterosexual population, I again hypothesize that we might see a larger effect size if all known LGBT folk were excluded from the study subjects.  If so, that would further support my hypothesis that humans don’t have sexually dimorphic brains so much as having androphilic vs. gynephilic ones.

Further Reading:

Essay on Sexually Dimorphic Brain Mosaic

Essay on Sexually Dimorphic Motor Behaviors

Reference:

Guidice, et Al, “The Distance Between Mars and Venus: Measuring Global Sex Differences In Personality”
http://dx.doi.org/10.1371/journal.pone.0029265

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Pink and Blue…

Posted in Brain Sex by Kay Brown on February 26, 2017

Teenage-brain… Brains

Or, Yes, We Now CAN Tell The Sex of a Person By Imaging Their Brain

Before recent developments in neuroimaging, I would have said that there was no way that we could determine the sex / gender of a person looking only at their brain.  In fact, I DID say exactly that.  But now, I don’t believe that that is an accurate statement, at least not wholely accurate, because a recent paper/letter has shown that with increased resolution and computer power we can determine the sex of a person that a particular brain resides in just from an analysis of the 3D image of their brains to 93% accuracy.  The mere fact that this can be done shows that the human brain is in fact highly sexually dimorphic, because if we were to simply guess, we would only be right 50% of the time.

The number, 93%, sounded suspiciously familiar to me.  That’s about the number of people who are not LGBT in the population.  Given that we also know that LGB people are likely to have sexually dimorphic features that as a population, are shifted towards that of the opposite sex, I’m proposing an hypothesis and a prediction.  If this analysis were redone excluding all known LGBT people, that the mathematical regression would result in greater predictive strength.  It would not reach 100% because there would still be those who due to social desirability bias would fail to disclose their sexual orientation and thus still be included in the heterosexual study group.  Increasing the accuracy in that instance will add evidence to a quip that I have made before, that humans don’t have male and female brains so much as androphilic and gynephilic brains.

There’s an important point that is missed by people with discussing the issue of whether the human brain is sexually dimorphic or not; The size and shape of any specific feature of the brain is to an extent only a very crude estimate of the number of neurons and the connection density of that region.  It does not tell us the functional differences, if any, that that difference represents.  As Cordelia Fine has pointed out, these differences, though they clearly exist, does not tell us what, if any, the differences may be in men’s and women’s minds.  Only additional research will help us determine these.

But still, anyone who still says that it is not possible to determine the sex of a human brain hasn’t been keeping up with the science.

(Addendum 3/4/2017:  I did a bit of calculation and found much to my amazement, that to “guess” the sex of the brain to 93% accuracy means that the effect size (Cohen’s d) would, if it were a single dimorphic feature, be a whopping 3.0 !!!!  That’s an over the top value.  Thus, as we get better imaging tools to see the fine details, we are learning that the human brain, in terms of multivariate statistics of multiple measurements at all points of the brain, is in fact extremely sexually dimorphic.  The problem is that no one area is all that dimorphic, but in aggregate, they are quite dimorphic.  That is to say, if one area is slightly dimorphic, giving a small statistical clue as to the sex of the individual, and a second area is also slightly dimorphic, giving a small clue as the sex of the individual, the two can be used together to give a medium sized clue to increase the accuracy… and with many many areas, each additively pointing towards one sex or the other, the accuracy gets quite good.)

Further Reading:

Book Review: Delusions of Gender by Cordelia Fine

Reference:

Chekrouda, et al., “Patterns in the human brain mosaic discriminate
males from females”  http://www.pnas.org/content/113/14/E1968.full.pdf

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Brainstorm

Posted in Brain Sex, Confirming Two Type Taxonomy, Female-to-Male by Kay Brown on July 2, 2016

critical-thinkingA new review paper has just been published on the current status of brain structure research in transsexuality.  Interestingly, it was submitted to the Archives of Sexual Behavior two full years ago.  This suggests that it went through a rather thorough peer review.  For myself, the first thing I do when reading a review paper is to see that the reference list is comprehensive to ensure that the authors aren’t cherry-picking.  In this case, they are not.  The paper looks to be very complete and scientifically honest.  You may wish to read it yourself, as it is not behind a paywall, thankfully.

The paper is written rather densely, with a great deal of information and discussion; so much in fact, that I will likely be writing several essays covering a number of topics from it.  At the high level, my regular readers will not be surprised at the primary conclusions drawn from the review, as I had already written about a fair number of the brain research papers.  The authors offer this chief conclusion at the end of the paper,

“The review of the available data seems to support two existing hypotheses: (1) a brain-restricted intersexuality in homosexual MtFs and FtMs and (2) Blanchard’s insight on the existence of two brain phenotypes that differentiate “homosexual” and “nonhomosexual” MtFs”

The review of all of the available brain structure research fully supports the Two Type Taxonomy.  In light of this, the authors recommend that future researchers take care to distinguish between the two types, lamenting that some studies in the review had not made this distinction, and further, that it is important that the control groups also be concordant with sexual orientation,

“The study of mixed samples implicitly assumes that transsexuals are a homogeneous group. This is far from the truth with respect to the onset of GD and sexual orientation.  …  These observations signify that control groups in studies of the transsexual brain must be homogeneous in regards to sexual orientation.”

The authors did find separate studies of androphilic “homosexual” MTFs and non-gender dysphoric gay men that used the same methods, such that a tentative comparison could be made,

“The only study on the CTh [cortical thickness] of homosexual persons that do not present gender dysphoria is by the Savic group (Abé et al.). If we compare this study with that of Zubiaurre-Elorza et al. on the CTh of homosexual MtFs, we see both studies report sex differences showing an F > M pattern in similar structures of the right hemisphere. But there is only one region, the pars triangularis, in which homosexuals and homosexual MtFs both present differences. However, these changes are in opposite directions. The pars triangularis of homosexual MtFs is thicker than in heterosexual male controls, while for homosexuals it is thinner than in heterosexual males. Thus, it seems that for transsexuals this region is feminized but demasculinized [i.e.: “different that straight men, but not in the heterosexual female direction” – K. Brown] in homosexual individuals. Interestingly, in both studies, the affected pars triangularis is in the right hemisphere. Nevertheless, confirming Blanchard’s prediction still needs a specifically designed comparison of homosexual MtF, homosexual male, and heterosexual male and female people.”

This is interesting, that there is a difference between gay men and androphilic transwomen?  But the right hemisphere pars triangularis of all things?  For left hemisphere dominant people, this region of the brain is believed to be involved in the understanding and production of prosody, emotionally nuanced speech modulation.  We know this because individuals who have serious lesions in this area have trouble with prosody.

For more information, read the Wikipedia page on prosody.

Before anyone gets too excited about the possible implications for a neurological marker for androphilic transsexuality that differentiates them from gay men, we need to note that the brain exhibits neuroplasticity.  That is to say, that like a muscle, exercise of particular skills causes the brain to increase in volume and neuron number in those regions used to supply that skill.  If this is about language and more particularly, about language production that imparts an emotional / sexual identity / gender identity through one’s voice, the difference in this part of the brain may be caused by experience and practice.

For more information, read my essays on feminine speech production and on voice recognition.

On the other hand, it just might represent a real difference.  We need more studies.

References:

Guillamon, A et al., “A Review of the Status of Brain Structure Research in Transsexualism” Arch Sex Behav (2016). doi:10.1007/s10508-016-0768-5

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Ripe Cherries…

Posted in Brain Sex, Science Criticism by Kay Brown on January 16, 2016

phrenology… or How the Science of Changing Sex is Distorted by the Transsexual Community
Funny how I have been carefully writing about the science regarding transsexuality and transgender sexuality and trying to be very careful about NOT cherry picking or distorting the evidence by either misstating or omitting key points?  Well… now I seem to have competition at The TransScience Project.  Of course, it appears that they are cherry picking or leaving out key data points.  For instance, lets examine an essay written by Sarah Lewis on “The Brain And Gender Dysphoria”:

“The first study of its kind was conducted by Zhou et al (1995). The study found sex a-typical differences in the stria terminalis of the brain stem when studying transgender subjects. A follow up study by Kruijver et al (2000) confirmed the findings and provided greater insight. The central subdivision of the bed nucleus of the stria terminalis (BSTc) is sexually dimorphic. On average, the BSTc is twice as large in men as in women and contains twice the number of somatostatin neurons. These numbers do not appear to be influenced by sexual orientation or hormone replacement therapy – and both were controlled for by Zhou and Kruijver. A paper by Chung et al (2000) studied how the volume of the BSTc varied with age in both male and female subjects. They found that the dimorphism was only prevalent in adulthood. Suggesting that the differences found by Zhou and Kruijver are not a cause of gender dysphoria but rather a result.”

Ummm… “not a cause but rather a result.”  Yes… and not quite.  No, the BSTc was influenced by exogenous hormones as a result of treating gender dyshoria, not because of gender dysphoria.  Gotta hand it to her, Lewis did a great slight of hand trick there huh?  It almost sounded like the BSTc was related to gender dysphoria… but it’s not.  Ms. Lewis failed to explain that taking hormones causes changes in the brain toward the target sex.  Not quite saying a falsehood… just letting an unwary reader be mislead.  Which is what she continues to do in the paper:

“In Luders et al. (2009), 24 trans-women who hadn’t started hormone-replacement therapy were studied via MRI. While regional grey matter concentrations were more similar to men than women, there was a significantly larger volume of grey matter in the right Putamen compared to men. As with many earlier studies, they concluded that gender dysphoria is associated with a distinct cerebral pattern.  In contrast, Savic et al (2011) did not find any sex a-typical differences in the Putaman, or other investigated areas of the brain. They did however find differences between their trans-women group and both the male and female controls.”

She didn’t mention that this research, both studies, included only non-exclusively  androphilic (i.e. primarily gynephilic) transwomen.  In fact, throughout her essay, she fails to make this distinction, which allows data that supports Blanchard’s prediction that exclusively androphilic (transkid) MTF transwomen would show shifts toward a feminized brain, but the non-exclusively androphilic would not, though they would show non-sexually dimorphic differences from both men and women, to be falsely interpreted to suggest that evidence for brain feminization in MTF transkids to apply universally.  Actually, in this case the larger volume of grey matter in the right putamen was larger than men AND women, suggestive of a non-sexually-dimorphic brain marker for autogynephilic transwomen, exactly as predicted, as explained in my essay, “And the Beat Goes On”.

Had she compared the Savic (2011) paper to the Simon (2013) paper, especially if she had quoted Simon, she might have had a far different interpretation, as I did in my earlier essay, “Shades of Grey matter”

In that paper, Simon pointed out that their study used the same methods, but found quite different results, and noted that it was because of the issue of the two types of transwomen.  Looking at only androphilic MTF transwomen, they did find that they were similar to female controls and not to male controls.  But that would not have suited Lewis to have pointed that out.  In fact, Lewis failed to note that studies which did find sexually dimorphic shifts, were conducted on exclusively androphilic transwomen,

“Two studies by Rametti et al (2011) looked at white matter differences in both trans-men and trans-women.

In their study of trans-men they found that control males have significantly higher fractional anisotropy values (FA is a measure often used in diffusion imaging where it is thought to reflect fiber density, axonal diameter, and myelination in white matter) than control females “in the medial and posterior parts of the right superior longitudinal fasciculus (SLF), the forceps minor, and the corticospinal tract”.

Compared to control females in the study, trans-men “showed higher FA values in posterior part of the right SLF, the forceps minor and corticospinal tract. Compared to control males, trans-men showed only lower FA values in the corticospinal tract.”

The study concluded that there was evidence for an inherent difference in the brain structure of trans-men.

In their study of trans-women they found that trans-women “differed from both male and female controls bilaterally in the superior longitudinal fasciculus, the right anterior cingulum, the right forceps minor, and the right corticospinal tract.” The nature of these differences suggests that some fasciculi do not complete the masculinization process in trans-women during brain development.”

However, I did point out that this only applies to exclusively androphilic transkids in my essay, “Seeing the world in grey and white”.

Lewis is not a very critical reader of the scientific literature… especially if it suits her thesis.  In fact, she accepted at face value one paper, that purported to have shown that MTF transwomen (all non-androphilic, btw) responded to human male pheromones the same as control females.  (Which is strange, because if they did respond like straight women, why aren’t they attracted to men?)  Problem?  Ummmm… nothing…. except that there’s no such thing as human pheromones!!  I pointed that out in my essay, “False (Scent) Trail”.

And speaking (er… writing) of not being critical,

“Garcia-Falgueras and Swaab (2008) investigated the hypothalamic uncinate nucleus, which is composed of two subnuclei, namely interstitial nucleus of the anterior hypothalamus (INAH) 3 and 4. They showed for the first time that INAH3 volume and number of neurons of trans-women is similar to that of control females. The study also included analysis of a single trans-man who also had a INAH3 volume and number of neurons within the male control range.”

As I pointed out in my essay, “The Incredible Shrinking Brain”, this too was easily shown to be an effect of hormone therapy, just like Swaab’s earlier report about the BSTc, in fact, these were the same subjects who had been on HRT for years, sigh…  Had she read my essay, would Lewis have included my analysis?

She concludes with one paper which suggests a difference between control men and MTF transwomen with respect to the ability to mentally rotate images.  Looking at the subject’s ages, average 37, we can see that they are likely mostly non-androphilic.  This paper looks interesting, but is this really a sexually dimorphic difference?  Or a difference in IQ?  The transwomen were about IQ 107-109 and the control men, who performed better, were about IQ 123 (a significant difference at one standard deviation).  Me?  I’m going with IQ.

This isn’t the only example of cherry picking I’ve commented upon, as I wrote in an earlier essay, “Gender Allusions”.

So, we see that when looking at the scientific evidence and how it is presented, by and within, the transcommunity clearly wants to believe, and leave others with the impression, that it supports the notion that all transwomen have feminized brains and that there is only one kind of transwomen.  Sadly for them, neither is true.

Further Reading:

Essays on Brain Sex

Cherry Picking at Scientific American {Author uses only papers w/ exclusively androphilic subjects.}

 

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Brain Power…

Posted in Brain Sex, Confirming Two Type Taxonomy by Kay Brown on December 28, 2015

Teenage-brain

…I would while away the hours, confir’in with the flowers…. if I only had a brain…”  — Scarecrow, in the Wizard of Oz musical film.

After years of trying to explain the differences between the two types and the statistical evidence for the two type taxonomy of MTF transwomen, I’m now posting what should be the final clincher; solid biomedical laboratory evidence, “proof” even.

Decades ago, as I was researching our collective history and science (the two often go hand in hand), I came across a reference to studies that showed that gay men had feminized brains while MTF transsexuals did not.  SAY WHAT!?!?

Turns out, the study referenced made the false assumption that all MTF transsexuals are the same and had only included gynephilic older transitioners.  Other studies, being aware of, and accounting for the differences between the two MTF transsexual types found something quite interesting, as for example, from the Dörner (1983) abstract:

“In male rats, androgen deficiency during a critical period of sexual brain differentiation was shown to give rise to a predominantly female-differentiated brain. Such animals displayed “homosexual behaviour”, i.e., they were sexually attracted preferentially to partners of the same sex. In addition, they exhibited a sex-specific evocability of a positive oestrogen feedback effect. A positive oestrogen feedback effect on LH secretion was also induced in homosexual transsexual men, in contrast to hetero- or bisexual transsexual men. Thus in homosexual transsexual men, an intravenous injection of 20 mg Presomen (Premarin) produced a significant decrease of serum LH levels followed by a significant increase above the initial LH values. In hetero- or bisexual transsexual men, by contrast, intravenous oestrogen administration, while producing a significant decrease of serum LH levels, was not followed by an increase above the initial LH values. A positive oestrogen feedback effect on LH secretion was also found in homosexual non-transsexual men, in contrast to heterosexual men. These findings suggest that transsexual as well as non-transsexual homosexual men possess a predominantly female-differentiated brain which may be based, at least in part, on androgen deficiency during sexual differentiation of the central nervous system. Homosexual transsexual men also showed an increased LH and FSH response to LH-RH as compared to hetero- or bisexual transsexual men.”

Note that non-exclusively-androphilic (“heterosexual or bisexual”) transwomen did NOT have the female like positive estrogen feedback effect on LH serum levels.  Of course, according the Blanchard’s work, all “non-homosexual” MTF transsexuals should also be in the same taxon, so we would predict that so-called, asexual transsexuals should also show the lack of this positive feedback, and indeed, this too was found, as discribed in the Dörner’s (1976) earlier paper,

“In transsexual men with homosexual behaviour and intact testicular function, as well as in homosexual men with normal gender identity, following a negative oestrogen feedback effect a delayed positive oestrogen feedback action on LH secretion was evoked. By contrast, in transsexual men with hypo- or asexuality and intact testes or hypergonadotrophic hypo- or agonadism, as well as in heterosexual men with normal gender identity, a negative oestrogen feedback effect was not followed by a positive feedback action on LH release. In transsexual women with homosexual behaviour and oligo- and/or hypomenorrhoea, only a weak or at best moderate positive oestrogen feedback action on LH release was evocable, similarly as in castrated and oestrogen-primed heterosexual men. By contrast, in a transsexual woman with bisexual behaviour and eumenorrhoea, a strong positive oestrogen feedback action on LH secretion was evocable, as well as in heterosexual women with normal gender identity.”

Note that in this paper we see a mirror like difference between FtM “homosexual transsexuals” (gynephilic transmen) who respond more like heterosexual men and bisexual FtM transmen who respond more like heterosexual women.  Thus, this data would lend support for there being a taxonic difference between exclusively gynephilic and non-exclusively gynephilic transmen, mirroring the taxonic difference between the two types of transwomen.

Conclusion:

These papers, detailing a specific, repeatable, laboratory based test that can differentiate the two types of transsexuals described by Blanchard, “Homosexual” and “Non-Homosexual”, offers both supporting evidence for the two type taxonomy but potentially also a way of independently sorting the two types in future studies.  This difference is a classic medical biomarker for the two types.  Should anyone one doubt the weight of statistical evidence, we can also point to the biomedical evidence via laboratory tests.

References:

Dörner G, Rohde W, Schott G, Schnabl C., “On the LH response to oestrogen and LH-RH in transsexual men.” Experimental Clinical Endrocrinology (1983)
http://www.ncbi.nlm.nih.gov/pubmed/6317420

Dörner G., “Neuroendocrine response to estrogen and brain differentiation in heterosexuals, homosexuals, and transsexuals.” Archives of Sexual Behavior (1988)
http://www.ncbi.nlm.nih.gov/pubmed/3282489?dopt=Abstract

Dörner G, Rohde W, Seidel K, Haas W, Schott GS.”On the evocability of a positive oestrogen feedback action on LH secretion in transsexual men and women.” Endokrinology (1976)
http://www.ncbi.nlm.nih.gov/pubmed/1244197

 

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Gender Allusions

Posted in Brain Sex, Science Criticism by Kay Brown on February 24, 2015

critical-thinkingIs “Gender Identity” biological?  For most people, the answer is intuitively obvious, “duh!”.  Of course, for these people, they usually also insist that the markers for such identity is some privileged and testable characteristic, like genitalia, which is easy to observe, or karyotype (sex chromosome configuration) which requires a microscope.  But for people with Disorders of Sexual Development (DSD), these markers may not be all that clear.  Further, what are we to make of the gender identities of transsexual and transgendered people, people whose experienced / stated gender identity is at odds with all currently known sex markers?  IS there a biological etiology?  And is that etiology the same as that that gives rise to the gender identity of non-trans people? A recent review article attempts to answer these very questions.  Sadly, I believe that it falls far short of a conclusive answer.  In fact, as I will show, it invokes conclusions from several papers as evidence that are quite questionable.  Further, the authors failed to note the very probable multiple etiologies for Gender Dysphoria and their associated gender identity resolutions suggested by the Freund/Blanchard two type taxonomy of MTF transsexuality. First, they reviewed evidence for a biological basis for the phenomenological existence of “gender identity” in non-transfolk which comes from those with certain DSDs,

A seminal study by Meyer-Bahlburg et al involving outcomes of XY individuals raised as females due to severe non-hormonal, anatomic abnormalities of sex development has provided the most convincing evidence that gender identity is fixed. These congenital abnormalities include penile agenesis, cloacal exstrophy, and penile ablation. For many years, female gender assignment along with surgical feminization was the dominant approach for these patients. In this study, it was observed that 78% of all female-assigned 46 XY patients were living as females. While the majority of these patients did not initiate a gender change to male, none of the 15 male raised 46 XY patients initiated a gender change to female. Thus, risk of questioning gender identity was higher in those patients raised as females than in those raised as males among 46 XY subjects with one of these conditions. A study by the same group that examined the degree of satisfaction with surgical intervention reported by patients with 46 XY genotype also found that those subjects raised as boys were considerably more comfortable with their gender identity. – Another seminal study relevant to this topic was by Reiner and Gearhart in their review of 16 XY genotype subjects with cloacal exstrophy who underwent female gender reassignment surgery. Out of the 14 individuals raised as girls, 4 announced they were male and 4 later chose to live as boys when they became aware of their genotype. The 2 individuals who were raised as males identified as males throughout life. The sexual behavior and attitudes of all 16 subjects ultimately reflected strong masculine characteristics regardless of gender assignment. Thus, children who were born genetically and hormonally male identified as males despite being raised as females and undergoing feminizing genitoplasty at birth. Although cohort size in these studies is small, these data provide the strongest evidence for biological underpinnings of gender identity.  …  In a study of affected subjects, gender role changes were reported in 56-63% of cases with 5 alpha-reductase-2 and 39-64% of cases with 17-beta-hydroxy-steroid dehydrogenase-3 who were raised as girls (6). These data support the concept that gender identity might be attributed to hormone milieu during intrauterine development on some occasions.

These studies are indeed very strong evidence.  Looking at the data, we see that of those raised as girls, 22% of of these subjects in the first study and 57% in the second study, while in the third study, those with hormonal abnormalities, 56-63%, chose to socially transition from female-to-male.  Compare that to the very, very small number of 46XX individuals in the general population who experience severe gender dysphoria and choose to transition.  As an aside, the fact that not all chose to transition should not be taken as proof that gender identity is all that malleable, but should probably be taken as a demonstration that social transition has very high social costs and is not undertaken lightly. Strangely, this paper did not explicitly mention that the majority of these individuals, whether they experienced gender dysphoria or not, were exclusively gynephilic, but they did allude to it.  Also puzzling was their failure to include the converse situation of individuals with 46XY and complete androgen insensitivity syndrome (CAIS), all raised as female, who are extremely unlikely to experience gender dysphoria or sex reassignment, and are universally exclusively androphilic.  Or the even more interesting case of 46XX progestin influenced females raised as male, 50% of whom transitioned from male to female and all are exclusively androphilic.

Thus, they failed to explicitly show the very high correlation of brain sex with gender identity, gendered behavior, and sexual orientation. Having shown that there is indeed very strong evidence that “gender identity might be attributed to hormone milieu during intrauterine development on some occasions”, which supports the notion that gender identity has a basis in biology (as opposed to being purely a social construct overlain on observable sex differences), it is tempting to say that transsexuality, all transsexuality and transgender identity, is also the result of mismatched hormonal milieu.  In fact, many transsexuals hold to just such a position.

But they would be dead wrong.

The logical leap that all transsexuals have such an etiology is not supported by the above evidence.  In fact, given the very probable differing etiologies for Gender Dysphoria and their associated gender identity resolutions suggested by the Freund/Blanchard two type taxonomy of MTF transsexuality, at least one of these types must NOT have been caused by such.  Blanchard went on to predict that this would be born out by studies of the sexually dimorphic structures in the brain, predicting that the exclusively androphilic MTF transsexual would show shifts toward the female morphology, while the other type would not. It is here that this recent paper has its biggest failings, in that not only did they not discuss this issue, but included very problematic studies by Swaab that purported to have shown female like shifts in non-exclusively androphilic transwomen.  These papers did show the shifts in the BSTc and INAH3, but incorrectly concluded that they had existed prior to exogenous HRT and incorrectly concluded that these features in the brain were organization effects of endogenous hormones in utero, when the data clearly demonstrated the opposite, that these shifts were purely activational effects from exogenous estrogenic and anti-androgenic HRT.  To be fair, they did mention that the BSTc was potentially questionable, but completely failed with regards to the INAH3, which demonstrably is not evidence for a biological basis of gender identity.

In reviewing the recent grey and white matter studies, they failed to note that it fits and supports Blanchard’s prediction, which had they done so, would have strengthened their argument for a biological basis for a conventional gender identity in exclusively androphilic MTF transsexuals.  That is to say, that they experience the same feminine “gender identity” as females because their brains are female like.  Conversely, they would also have evidence for a biological underpinning to autogynephiles sexuality, a non-sexually-dimporphic one, which lead to an epiphenomically generated “female gender identity” later in adulthood.  (See my essay on the different origins of cross-gender identity in transsexuals.)

The authors reviewed the literature on possible genetic factors that could lead to transsexuality, noting that they were inconclusive. Totally absent in this paper was any mention of the papers that document the fraternal birth order effect found in exclusively androphilic MTF transsexuals. All in all, I was disappointed in this paper.

I found it shallow, lacking in both depth and breadth, and literally out of step with much of the literature on the cutting edge of the science.

(Addendum 7/7/2015:  I got suspicious of this paper as it reads like a cherry-picked list of papers that support the brain sex hypothesis for all transsexuals, including “late onset” transwomen, so I checked into the background of the authors.  Sure enough, one of the authors is transgendered.  While that alone is NOT damning (after all, so am I), it does explain why this paper only referenced the studies it did, and did not include those studies that when considered as a whole, would show that while one subset of the larger transsexual population could possibly be explained by the brain sex hypothesis, most transwomen could not.  This paper then can and should be considered part of the ongoing effort by some in the transgender community to deny the evidence of the two type taxonomy.)

Reference:

Aruna Saraswat, MD, Jamie D. Weinand, BA, BS; Joshua D. Safer, MD, “Evidence Supporting the Biological Basis of Gender Identity” (2015) DOI:10.4158/EP14351.RA

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Shades of Grey…

Posted in Brain Sex, Confirming Two Type Taxonomy, Female-to-Male by Kay Brown on February 23, 2015

shrinking brainShades of Grey… Matter

We live in exciting times – At least scientifically.  We can now peer into the heads of transsexuals to see if their brains exhibit sexually dimorphic features that match their natal sex or their preferred gender.  Years ago, Ray Blanchard made a prediction, based on early evidence that there was a taxonic difference between “homosexual” and “non-homosexual” transwomen in sexuality, natural gendered mannerisms, age of transition, etc, that the former would show sexually dimorphic features in the brain that were shifted in the female direction while the latter would not, but would show features that were different than controls, but that they would not be sexually dimorphic features, and definitely not shifted in the female direction.  We now have yet more evidence that that prediction is correct, giving more weight to the two type taxonomy of MTF transsexuality, namely exclusively androphilic vs. autogynephilic.

The best evidence would be to use two populations of transwomen, one known to be exclusively androphilic and the other not, and test them for the same features, using the same type of measurement.  We now have that data for grey matter distribution in the brains of both types of transsexual.

In the earlier Savic and Arver paper, they compared grey matter distribution of 24 gynephilic transwomen, before HRT to that of heterosexual men and women.  (Remember, HRT itself causes a shift in sexually dimorphic features due to activational effects of sex hormones, and the lack of such hormones.)  The conclusion?

“The present data do not support the notion that brains of (gynephilic) MtF-TR are feminized.”

In the later Simon paper, they compared grey matter distribution of 10 exclusively androphilic transwomen, and 7 exclusively gynephilic FtM transmen, before HRT to that of heterosexual men and women.  The conclusion?

“Our findings support the notion that structural differences exist between subjects with GID and controls from the same biological gender. We found that transsexual subjects did not differ significantly from controls sharing their gender identity but were different from those sharing their biological gender in their regional GM volume of several brain areas, including the left and right precentral gyri, the left postcentral gyrus (including the somatosensory cortex and the primary motor cortex), the left posterior cingulate, precueneus and calcarinus, the right cuneus, the right fusiform, lingual, middle and inferior occipital, and inferior temporal gyri. Additionaly, we also found areas in the cerebellum and in the left angular gyrus and left inferior parietal lobule that showed significant structural difference between transgender subjects and controls, independent from their biological gender.”

The choice to explore only “homosexual” transsexuals in this study was informed by the researchers’ knowledge of the Freund/Blanchard taxonomy and of Blanchard’s prediction, as they explained,

“Both MTF and FTM patients were eligible for the study, but only those with homosexual orientation. The rationale for this choice was based on the Blanchard typology which considers two fundamentally different types of transsexualism: homosexual and nonhomosexual. Homosexual transsexual individuals are sexually attracted to the same biological gender, while nonhomosexual transsexual individuals are attracted to either the opposite gender or show no sexual orientation/attraction at all. According to Blanchard, homosexual transsexuals are usually younger at initial presentation of gender identity disorder and show more pronounced and frequent childhood femininity, as well as different anthropometric data. One might argue that mixing individuals from both transsexual groups in one study targeting the neurobiological background of transsexualism might bias the results by introducing heterogeneity in the sample. Thus, in our study, only homosexual transsexual individuals were included preventing our findings from the aforementioned bias.”

This points to growing recognition within the scientific community that the two type taxonomy is correct.  They went further, indirectly referring to the taxonomy and Blanchard’s prediction,

“In another study also limited to MTF transsexuals Savic and Arver, reported no “feminization” of any brain region with regard to structure. Nonetheless, certain brain areas (clusters ≥100 voxels) showed characteristic structural features in the transsexual group compared with both male and female control groups. Specifically, they found reduced thalamus and putamen volumes and increased GM volumes in the insular and inferior frontal cortex and in the right temporo-parietal junction (angular gyrus and superior temporal gyrus) in the transsexual group compared with both control groups. In our study, however only the angular gyrus (but in the left hemisphere) was affected among these areas, showing lower regional GM concentration in both FTM and MTF transgender subjects compared to controls, independent of their biological gender. When comparing the results reported by Savic and Arver to either our study or to other imaging studies in the literature of transsexualism, it has to be taken into consideration that their reported results were obtained from a solely nonhomosexual transsexual group of patients. The lack of real overlap between our and Savic and Arvers’ findings, despite the very similar methodology used, might at least in part be explained by the difference of the sexual orientation of the two samples.”

Truly, exiting times.

References:

Ivanka Savic, Stefan Arver, “Sex Dimorphism of the Brain in Male-to-Female Transsexuals”
http://cercor.oxfordjournals.org/content/early/2011/04/05/cercor.bhr032

Lajos Simon, Lajos R. Kozák, Viktória Simon, Pál Czobor, Zsolt Unoka, Ádám Szabó, Gábor Csukly, “Regional Grey Matter Structure Differences between Transsexuals and Healthy Controls—A Voxel Based Morphometry Study”
10.1371/journal.pone.0083947

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Autistic Sky

Posted in Brain Sex, Confirming Two Type Taxonomy, Female-to-Male by Kay Brown on September 21, 2014

shrinking brainFor the past several years, evidence has been accumulating that there is a fairly high comorbitity between transsexuality / transgenderism and the autism spectrum.  Interestingly, and perhaps not totally surprisingly, among MTF transwomen, it appears to be exclusively found in the non-exclusively androphilic population.  This fits the Freund/Blanchard taxonomy and more importantly, Blanchard’s prediction that “non-homosexual” (with respect to natal sex) MTF transwomen would exhibit neurological / brain differences from control males but these differences would NOT be a shift toward female like brains.

Autism and autism spectrum disorders are found in four to five  times as many men as women.  There are a number of theories as to why this happens, including the rather intriguing “hypermasculine brain hypothesis”, in which a link between the slight differences between men and women, as groups, having different cognitive and social behaviors and the apparent similarity, or rather, exaggeration of these differences between men and women, found in those on the autism spectrum.  If autism is a form of hypermasculinization, it would not surprise us to learn that FTM transmen were more autistic-like than most women… and that is what one group of researchers found.

Using a 50 item, Likert scored, instrument called the Autism Spectrum Quotient (AQ), Jones, et Al., found that FTM transmen as a group, scored 23.2, higher than control women AND men!  This puts about half of the FTM onto the high functioning autism spectrum!!   (The lower AQ cut-off for ASD is 23.)  Non-exclusively-androphilic transwomen scored essentially the same as the control men, while exclusively androphilic transwomen scored essentially the same as the control women, and definitely (statistically significant: p<0.03 ) below both the control men and non-androphilic transwomen.

Group:               Men                  Women       FTM                 Non-Androphilic           Androphilic
.                                                                                                     MTF  N=129                   MTF N=69

Score (SD):       17.8 (6.8)        15.4 (5.7)     23.2 (9.1)        17.4 (7.4)                         15.0 (5.6)

The implication is clear, FTM’s are masculine, perhaps even hypermasculine, while the data also supports the Freund/Blanchard two type taxonomy for MTF transwomen.  In the discussion section of the paper, the authors remarked,

“Interestingly, with the 198 transwomen group, there were 6 individuals (i.e. 3%) with a diagnosis of AS. This rate is about 3 times as many as in the general population.”

These authors didn’t state what the sexuality of the six AS individuals were; but if they conform to the greater likelihood that they were non-androphilic, found in other papers, the incidence rate for such non-androphilic transwomen would be closer to five times the rate found in the general population, however, that is only about twice as high as that found in the male population.

(Addendum: 1/21/2017:  Looking at the data again, this time from the perspective of effect sizes with respect to men vs. women and non-androphilic vs. androphilic aids us in understanding how important this difference is.  First, the effect size between men and women is 0.38 a modest but still very noticable difference in the populations.  Now, let’s look at the diffence between non-androphilic and androphilic at 0.37, nearly identical to the difference between men and women.  So, lets compare the difference between men and non-androphilic tranwomen at 0.06 which is tiny.  And similarly, when we compare between women and androphilic transwomen it is only 0.07 which again is very tiny.  That is to say, these statistical tests shows that the difference between men and women is the same size as between non-androphilic and androphilic transwomen, while there is effectly no difference between men & non-androphilic and women & androphilic transwomen respectively.  That is to say, that non-androphilic transwomen are identical to men in general, while androphilic transwomen are essentially the same as women in general.  Further the difference between the two types of transwomen exactly matches the difference between men and women, which strongly supports the Two Type Taxonomy.)

References:

Jones, et Al, “Female-To-Male Transsexual People and Autistic Traits”, J. Autism Dev. Discord. DOI: 10.1007/s10803-011-1227-8

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Drum keeps pounding… ♫♫

Posted in Brain Sex, Female-to-Male by Kay Brown on April 13, 2013

♫♫…rhythm to the brain…♫♫

shrinking brainData keeps coming in regarding brain imaging studies showing differences between MTF and FtM transsexuals and control males and females.  The question still remains, what does it mean?  Two studies, by two different groups, have measured the cortical thicknesses of transwomen before beginning HRT, to ensure that they are measuring potential organizing effects of endogenous hormones, or other effects, without the confounding activational effects of HRT.  However, the two studies looked at the two different MTF populations.  One, the Zubiaurre-Elorza paper examined only androphilic transwomen (N=18). Given that this group came from Spain, which, as Lawrence demonstrated, has a very low Hofstede Individualism index which is correlated with low percentage of gynephilic transwomen, these 18 were likely to have accurately reported their sexuality as exclusively androphilic.   While the Luders study, as an earlier study reported, examined both gynephilic (N=18) and self reported androphilic (N=6) transwomen.  Given that we know from many other studies of transwomen in high Hofstede Individualism societies, and the fact that the youngest of the Luders group was 23, we would expect that not all six of those who reported that they were androphilic were exclusively so.  In fact, I doubt that more than one or two at most is exclusively androphilic, if any.  Thus arises the question, can we use these two studies to get an early test of Blanchard’s prediction that “non-homosexual” transwomen would show brain difference from controls, but not a shift towards the female typical while the “homosexual” will show just such a shift?

First, some background, since I know that not all readers will be thoroughly up to date on the hypothesis being tested, nor the relevant data supporting it.  I recommend reading the FAQ on the is blog before continuing to read this blog entry, as a starting point.  Given that there is now mountains of data supporting the hypothesis that there are two types of MTF tranwomen, one autogynephilic (AGP) and non-homosexual (with respect to natal sex) and one that is non-autogynephilic and exclusively homosexual (HSTS); and that AGP transsexuals were behaviorally masculine since early childhood, and often even after transition and SRS, while HSTS transwomen had been remarkably feminine in behavior, and often in appearance, since early childhood, Blanchard made the prediction that brain studies would show that BOTH populations would be different than control males, but in different ways.  He further made the prediction that HSTS brains would be shifted toward the female morphology in sexually dimorphic areas of the brain, while AGP transsexuals would not.

This prediction is in opposition to the so called, “feminine essence” hypothesis, which is generally popular among AGP transsexuals, in which they posit that despite their obvious lack of naturally feminine behavior, they are still neurologically “female-like”, at least in some important way.

So far, the very limited data supports Blanchard’s hypothesis and NOT the “feminine essence” hypothesis.  Also so far, no formal study has been conducted that would specifically test these two hypothesis together.

I stated earlier that I didn’t believe that the Luders study group contain many exclusively androphilic (HSTS) individuals.  The reasons I believe this are several fold.  First, they collected most of their group by soliciting via transgender organizations.  As was shown in the Veale study on transsexual sexuality, soliciting through such organizations tends to reach only AGP individuals, as HSTS youth do not tend to be members of such.  Second is the age range of the study entire group.  The youngest was 23.  This would be very unusual for a group of that had a sizable portion of HSTS individuals, given that the median age of transition is 20 years old and the top end is typically 25 years old, and even that old is very rare.  If all six HSTS individuals were 23 to 25, this would be odd.  Also given that the mean age of the entire group is 45, which is a bit higher than the typical mean transition age for a group consisting of only AGP transwomen, this would suggest that there were not many of the total group that was in their early 20’s, certainly not six out of 24 individuals.  Thirdly, as Lawrence has shown, in two different study groups, significant numbers of individuals who claim to be androphilic are inaccurately reporting their sexuality.  Added together, I don’t believe that more than one or at most two, of the Luders study group was actually exclusively androphilic.  I suspect that none of them were.

As we explore the data from these two papers, we need to keep in mind that brains, like bodies, come in different shapes and sizes, more or less.  That is to say, although there are differences between male and female brains, on average, it is difficult to point to a part of the brain and say with absolute certainty, this is a male brain vs. a female brain.  Another thing to keep in mind, if we have a mix of two populations, both may have differences unique to each population… and that when mixed, both of those differences will be detected when we average the data, blurring and blunting the differences, but we should still be able to statistically see a signal in the data, provided we have enough data.

So, lets examine the data.  First, if we look at the high level view, it would appear that there are indeed differences between the control men and women and androphilic transwomen.

Zubiaurre Brain ScansIn general, female brains have thicker cortices (CTh), at least in some areas, as the comparison between male and female controls shows.  As we had expected, MTF  transfolk are different than male controls, but FtM are not that different from female controls.  The authors described the results thus,

“We have found that control females have greater CTh compared with control males in the frontal and parietal regions; in contrast, males have a larger putamen volume than females. With respect to the transsexual groups, we observed that FtMs have greater CTh compared with control males in the parietal and temporal cortices and did not differ from control females. However, FtMs have a larger right putamen than female controls. On the other hand, MtFs did not differ from control females in CTh and had greater CTh than control males in the frontal and occipital regions. In this group, no differences were found in the putamen. All these findings suggest that FtMs have a defeminized putamen, while MtFs have a feminized CTh.

With respect to the CTh of MtFs, we found that this group did not differ from female controls but did from male controls.  These findings suggest that MtFs follow the pattern of cortical thinning typically described for females. Whether the cortical feminization of MtFs depends on a differential cortical androgen receptor distribution, a different efficiency in the androgen receptors or other causes remains to be elucidated.  But what seems clear is that in MtFs the cortical developmental process is affected and follows the direction expected for females. This points out that the developmental approach could help to understand the etiology of transsexualism.”

Let’s compare these results with that of the Luders study, which is mostly (and perhaps entirely) non-exclusively androphilic, which being autogynephilic, Blanchard had previously predicted would show differences from control males, but not in the female like direction:

Luders Brain ScansAt first blush, we see that they are indeed, as predicted, different than control males.  Some areas of the cortices are thicker, but not the same regions as control females nor androphilic transwomen.  So, it would seem unlikely that these brain difference are caused by a feminization of the brain, given that the regions are not those found in control females.  But what does cause these particular differences?  While we might be tempted to conclude that this is caused by autogynephilia, it could also be caused by another attribute that is common in this population, higher IQ.  It has been noted that higher IQ is correlated with thicker cortices.

So where to do we go from here?  This visual comparison of the two studies can only be described as tentative.  But the need for such comparisons are clearly understood by these researchers, as the Zubiaurre-Elorza paper explained,

“On the basis of chromosomal sex and behavior, Blanchard and co-workers (Blanchard et al. 1987, 1989, 1996; Blanchard 1989; see also Smith et al. 2005) have proposed the existence of 2 types of MtFs: 1) MtFs that are attracted to males (“homosexual” transsexuals in Blanchard terminology), and 2) MtFs that are attracted to women (“heterosexual” transsexuals according to Blanchard). Further, Blanchard (2008) hypothesized that homosexual MtFs would differ from heterosexual males in brain sexually dimorphic structures, while in the heterosexual MtFs, the differences might not implicate sexually dimorphic structures. More recently, Cantor (2011) has noted that our findings on the white matter microstructure of (homosexual) MtFs (Rametti, Carrillo, Gómez-Gil, Junque, Zubiarre-Elorza et al. 2011) and that of Savic and Arver (2011) on the cortical volume of (heterosexual) MtFs would support Blanchard’s hypothesis. In the present report, we studied MtF transsexuals erotically attracted to males that show a feminization of CTh but not in the putamen.  …  Consequently, to verify Blanchard’s hypothesis would require a specific design that is beyond the scope of the present study.”

For more essays on trans-brains see Brain Sex.

References:

Eileen Luders, et al., “Increased Cortical Thickness in Male-to-Female Transsexualism”
Journal of Behavioral and Brain Science, July 2011
http://dbm.neuro.uni-jena.de/pdf-files/Luders-JBBS11.pdf

Leire Zubiaurre-Elorza et al, “Cortical Thickness in Untreated Transsexuals”
Cerebral Cortex, August 2012
http://cercor.oxfordjournals.org/content/early/2012/08/30/cercor.bhs267.abstract

Katherine Narr, et al., Relationships between IQ and Regional Cortical Gray Matter Thickness in Healthy Adults
Cerebral Cortex, November 2006
http://cercor.oxfordjournals.org/content/17/9/2163.abstract

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And the Beat Goes On…♫♫

Posted in Brain Sex, Confirming Two Type Taxonomy by Kay Brown on December 8, 2011

♫…Drum keeps pounding rhythm to the brain… La di da di dee…♫

shrinking brainJames Cantor recently published a letter to the editor in the Archives of Sexual Behavior pointing out nearly the same point that I had made earlier, that recent MRI scans of transsexual brains show clear evidence that Blanchard’s two type hypotheses is supported.  One of the papers he referenced is one that I had earlier referenced; The Rametti study in Spain, which showed that MTF  transkids have partially feminized brain structures.  The other paper is new to me; The Savic paper clearly adds yet another confirming MRI study that when combined with the Luders MRI study, shows that gynephilic MTF transsexuals do not have feminized brains.  On top of it, true to another speculative prediction that Blanchard made, the new study confirms the other paper’s finding that gynephilic (AGP) MTF transsexuals show other, non-sexually dimorphic structures, are different from both non-transsexual men and women!

These two papers both noted that the putamen of gynephilic MTF transsexual are different from both non-TS men and women.  This may be the main area to research in the future?

For more essays on trans-brains see Brain Sex

References:

Cantor, James, “New MRI Studies Support the Blanchard Typology of Male-to-Female Transsexualism”
http://www.springerlink.com/content/b52p04306u076623/

Reply to Italiano’s (2012) Comment on Cantor (2011)
JamesM. Cantor  http://link.springer.com/content/pdf/10.1007%2Fs10508-012-0011-y

Rametti G, Carrillo B, Gómez-Gil E, Junque C, Zubiarre-Elorza L, Segovia S, Gomez A, Guillamon A., “The microstructure of white matter in male to female transsexuals before cross-sex hormonal treatment. A DTI study.”
http://www.ncbi.nlm.nih.gov/pubmed/21195418

Ivanka Savic, Stefan Arver, “Sex Dimorphism of the Brain in Male-to-Female Transsexuals”
http://cercor.oxfordjournals.org/content/early/2011/04/05/cercor.bhr032

Luders E, Sánchez FJ, Gaser C, Toga AW, Narr KL, Hamilton LS, Vilain E., “Regional gray matter variation in male-to-female transsexualism.”
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2754583/

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