Tag Archives: trans teens

Prenatal exposure to anticonvulsants and psychosexual development

This is a 1999 study with intriguing results.

The authors followed-up on 243 people who were exposed to phenobarbital and/or phenytoin before they were born.

Three of them had medically and socially transitioned; two trans men (born female) and one trans woman (born male).*

Among the 147 people who they were able to speak to, the authors also found three possible cases of gender dysphoria.

One woman had had cross-gender feelings from childhood until age 21 when she became pregnant.

Another woman “did not feel very comfortable with her femininity, but had made the conscious decision to ‘to behave like a woman.'”

Finally one of the men “denied the changes his body had undergone during puberty. He claimed to have a female’s voice (although the researcher heard a male voice), he denied having facial hair (although he had a moustache), and he denied having erections.”

There were also two gay men among the people they interviewed.

The authors looked at a control group of people born at their hospital during the same time period (1957-1972). None of them had transitioned, none of them reported gender dysphoria, and none of them were gay.

In addition, the authors compared the number of trans people in their sample to the general population in the Netherlands and the difference was statistically significant.

Clearly, something is going on here.

Why hasn’t anyone followed up on this? Well, for one thing, phenobarbital and phenytoin are no longer given to pregnant women. We don’t need to worry about any possible risks from people taking them. Besides, it would be hard to find people born recently who had been exposed to phenobarbital before birth.

On the other hand, the results suggest that it may be worth looking for connections between gender dysphoria and medications mothers take during pregnancy.

The authors of the study theorized that in order to metabolize the anti-convulsants, the fetus would produce microsomal enzymes in its liver. Then, “these enzymes also catabolize steroid hormones so that the steroids cannot properly exert their action on brain and body.”

This would suggest that prenatal hormones were involved in developing gender dysphoria.

It might be, however, that the medications themselves affected the babies.  Both phenobarbital and phenytoin are known to cause fetal abnormalities.

It could also be that the medications affected the mothers’ eggs rather than affecting the baby.

If the mothers breastfeed the babies and continued to take the drugs, they might have affected the babies’ development after birth.

Another factor to consider is that phenytoin may cause babies to develop ambiguous genitals. That in turn might affect how children are raised, including the possibility of being raised as a sex different from your genetic sex. It would be useful to know if any of the people in the study had ambiguous genitals.

It’s also possible that the drugs themselves weren’t the issue here. The mothers were taking the drugs for a reason. Could the mothers have passed on genes related to epilepsy or emotional problems that also affected gender identity? Could being raised by a mother with epilepsy or emotional problems affect gender dysphoria?

In this study, one of the trans men had a mother with epilepsy; the mothers of the other trans man and the trans woman did not. It’s not clear from the article if the two non-epileptic mothers took phenobarbital for emotional problems or pregnancy-related complaints.

There’s no information given on the mothers of the three people who did not transition but had some symptoms of gender dysphoria.

This is not strong evidence of a link between epilepsy and gender dysphoria, but it might be worthwhile for someone to do a study looking at epilepsy in the families of people with gender dysphoria.

We don’t know anything about the non-epileptic mother of the trans man as the trans men did not participate in the follow-up interviews.

However, among the people the authors interviewed, cross-gender behavior was not related to parental psychiatric problems, family problems during childhood, or socioeconomic status. This should not be surprising – cross-gender behaviors are not a problem. They are also not the same thing as gender dysphoria.

Which leaves us where we started: it is possible that something about the mothers or their genes affected the children who developed gender dysphoria.

The study provides some other evidence about exposure to the medications and psychosexual development. The authors interviewed 147 people in depth and looked at other possible traits that might have been influenced if the prenatal hormones were abnormal. This group did not include the two trans men, but it did include the trans woman and the three people with some symptoms of gender dysphoria.

They did not find statistically significant differences between the people exposed to anti-convulsants and the controls in gender role behavior in childhood or adulthood, sexual orientation,** physical development during puberty, feelings about puberty, adult satisfaction with secondary sex characteristics, or experience of their first sexual activities.

In general, the overall psychosexual development of people exposed to the anti-convulsants prenatally was not different from the people who were not exposed.

They did find, however, that there were more people in the group exposed to anti-convulsants who had high cross-gender behavior scores than in the control group. In other words, the group averages were comparable, but there were more people who were very gender non-conforming in the group that had been exposed to anti-convulsants.

So did the pre-natal hormones matter? We still don’t have the answer.

It could be that the anti-convulsants only affected some babies’ hormones. It could be that they affected the hormones, but that this isn’t enough to cause gender dysphoria in most people; perhaps the environment plays a role. It could be that the hormones are irrelevant and the medications directly affected the babies or the mothers’ eggs. It could be that something about the mothers who needed to take medications was different and affected their children.

What we do know is that taking these medications was linked to developing gender dysphoria severe enough for people to transition.

It’s a result worth some new research – does exposure to other medications affect gender dysphoria? does it matter if the father is exposed to the medication? are there any links between epilepsy and gender dysphoria?

Original Article:

Prenatal exposure to anticonvulsants and psychosexual development by Dessens AB, Cohen-Kettenis PT, Mellenbergh GJ, vd Poll N, Koppe JG, Boer K. in Arch Sex Behav. 1999 Feb;28(1):31-44.

 

 

*Some details about the transitioners:

The trans woman was exposed to phenobarbital during weeks 18-40 gestational age and one of the trans men was exposed to it during weeks 36-42.  Their mothers did not have epilepsy. They authors don’t mention the dose they took, but earlier they say that mothers who didn’t have epilepsy generally took a lower dose.

The other trans man was exposed to phenobarbitol, phenytoin, and amphetamines throughout the pregnancy. His mother had epilepsy.

All three of them started hormone therapy at age 18-23 and had sex reassignment surgery at 20-25. The trans woman had identified as a girl since early childhood; the authors did not have data on the trans men.

**However for sexual orientation in males, the p-value was 0.07 which is close to statistically significant. (There were two gay men in the group exposed to anti-convulsants and none in the control group.)

Depression and Gray Matter in the Brain

Depression causes gray matter in the brain to decrease. This is important to keep in mind when looking at studies of trans people’s brains as many trans people have experienced depression.

These are just a few links to studies looking at depression’s effects on the brain. A smaller hippocampus seems to be particularly related to depression, although studies have also found a link to an overall decrease in gray matter.

The bottom line is that studies of gray matter and gender identity need to take into account past and present depression in both trans people and controls.

For anyone with depression, the bad news is that it’s not good for your brain. The good news is that you can do things for your brain – exercise, meditate, and learn.

You may be able increase the volume of your hippocampus with regular exercise. Eight weeks of mindfulness meditation increases the volume of your hippocampus and may increase the gray matter volume in other areas of your brain as well. You can increase your gray matter by learning a new skill like juggling or by reading text written backwards. Going to medical school affects your gray matter.

Back to the studies and the link between gray matter volume and depression.

State-dependent changes in hippocampal grey matter in depression. 

This study found that patients who were currently depressed had lower volumes of gray matter in the hippocampus compared to both healthy controls and people who had had depression before but were not currently depressed. After taking citalopram, the patients with current depression had more gray matter in the hippocampus.

Insular and Hippocampal Gray Matter Volume Reductions in Patients with Major Depressive Disorder.

This study found that patients with major depressive disorder had “a strong gray-matter reduction in the right anterior insula. In addition, region-of-interest analyses revealed significant gray-matter reductions in the hippocampal formation.”

The effects were stronger for people who had had more episodes of depression than people who had only had one episode.

The more episodes of depression a patient had, the less gray-matter volume they had in the right hippocampus and right amygdala.

They conclude:

“The anterior insula gray matter structure appears to be strongly affected in major depressive disorder and might play an important role in the neurobiology of depression. The hippocampal and amygdala volume loss cumulating with the number of episodes might be explained either by repeated neurotoxic stress or alternatively by higher relapse rates in patients showing hippocampal atrophy.”

In other words, having depression might affect the hippocampus or having a small hippocampus might make you get depressed more often.

Association of Depression Duration With Reduction of Global Cerebral Gray Matter Volume in Female Patients With Recurrent Major Depressive Disorder

This study found that the more months the patients had spent being depressed, the less total cerebral gray matter they had. More months of depression was also linked to less frontal gray matter, less temporal gray matter, and less parietal gray matter. The study only included female patients who had recurrent depression. They did not control for the anti-depressants the patients used, so it is possible that the medicines affected their gray matter.

Gray matter volume abnormalities in individuals with cognitive vulnerability to depression: A voxel-based morphometry study.

This study looked at people who don’t have depression but who might be vulnerable to it. The “cognitively vulnerable” group was chosen by their answers to two questionnaires. The first questionnaire looked at thinking styles that may contribute to depression – people may be vulnerable to depression based on how they think about causal attributions, consequences, and self-worth characteristics. The second questionnaire asked about symptoms of depression.

Cognitively vulnerable people had less gray matter volume in the left precentral gyrus and right fusiform gyrus compared to controls. In addition their right fusiform gyrus and right thalamus were smaller compared to people who had major depressive disorder. Patients with major depressive disorder had reduced gray matter volume in the left precentral gyrus and increased gray matter volume in the right thalamus.

They conclude:

“Reductions in brain gray matter volume exist widely in individuals with CVD. In addition, there exist similar abnormalities in gray matter volume in both CVD subjects and MDD patients. Reductions of gray matter volume in the left precentral gyrus might be correlated to the negative cognitive styles, as well as an increased risk for depression.”

Of course, we don’t know which way the causality goes – is the cognitive style causing a lower gray matter volume in the left precentral gyrus or is the lower volume of gray matter causing the cognitive style?

Widespread reductions in gray matter volume in depression.

This study found that people with major depressive disorder had 4.4% less global gray matter volume than controls. This would be the decrease expected in 14 years of normal aging.

The differences were greatest in the front and temporal lobes, but there were also significant differences in the parietal and occipital lobes.

There was not a significant difference in the cerebellar volumes.

The cortex was thinner in the left medial orbitofrontal cortex for the patients with depression.

The authors conclude:

“Our data demonstrate conclusively that widespread GM volume abnormalities are present in patients with depression. These alterations are substantial, corresponding to the amount of GM volume loss that, when averaged over the whole brain, would be expected from nearly 14 years of normal aging. The GM loss is also highly regionally specific, with focal regions showing decreases in GM volumes of nearly twice the magnitude of the global measure. The distributed and regionally specific nature of these alterations provides compelling support for considering MDD as a condition that involves the impairment of networks across the brain.”

Small frontal gray matter volume in first-episode depression patients.

This study found that patients who had had their first episode of depression had less gray matter volume in the frontal lobe than healthy controls. The lower volume was not correlated with length or severity of the illness. The patients had not yet taken any medication for their depression. The authors suggest that the changes in gray matter could have occurred before the symptoms of depression. (Although they also could have been caused by the depression, we really can’t tell.)

Anomalous Gray Matter Structural Networks in Major Depressive Disorder

This study found that the gray matter in people with depression is connected differently from in controls.

They say:

“Depressed participants had significantly decreased clustering in their brain networks across a range of network densities. Compared with control subjects, depressed participants had fewer hubs primarily in medial frontal and medial temporal areas, had higher degree in the left supramarginal gyrus and right gyrus rectus, and had higher betweenness in the right amygdala and left medial orbitofrontal gyrus.”

and they conclude:

“Networks of depressed individuals are characterized by a less efficient organization involving decreased regional connectivity compared with control subjects. Regional connections in the amygdala and medial prefrontal cortex may play a role in maintaining or adapting to depressive pathology.”

Gender and Autism – an article

This is an excellent article reviewing research on gender and autism. I highly recommend it.

Gender and Autism: a Preliminary Survey Post on the blog “Musings of an Aspie.”

The author discusses the “extreme male brain” theory of autism and suggests some alternatives.

She also talks about factors that might influence how people with autism spectrum disorders experience gender:

“This raises the question of what role being autistic might play in the formation of our personal experience of gender. For example, autistic children are less sensitive to social cues than typical children and may not make friends with or become part of groups of same-gender peers. If we’re not tuned in to what the social norms for children of our gender are, we’re less likely to adopt them early in life.

There may also be an aspect of autistic-related body dysmorphia in general that factors into gender dysphoria for some autistic individuals. Many autistic people have difficulty feeling connected to their physical selves or being physically comfortable with their body.

Finally, there is the issue of sensory sensitivities. Dressing or presenting androgynously may be a result of gender dysphoria or it may be related to avoiding sensory triggers associated with certain types, textures or styles of clothing.”

Enjoy the article!

White matter microstructure in female to male transsexuals before cross-sex hormonal treatment. A diffusion tensor imaging study – Review

This study compared the white matter in the brains of males, females, and female to male transsexuals (FtM).*

This is one of a set of studies; another one looked at the white matter in the brains of male to female transsexuals (MtF) .

White matter is the stuff in your brain that transmits signals from one area to another. It is mostly made up of glial cells and axons. Glial cells are cells in the brain that aren’t nerve cells; they’re like a support system for the nerve cells. Axons are the long skinny part of your nerve cells that transmit information.

In three fasciculi (bundles of nerve fibers), FtM transsexuals had white matter that was like males and different from females.

In the corticospinal tract, FtM transsexuals’ white matter microstructure pattern was between the pattern of the male and female controls.

The study does not say if there were any other ways in which FtM transsexuals’ white matter was different from both males and females without gender dysphoria. I think they did not look at the question; they seem to have analyzed the data first to find sex differences and then to compare FtM transsexuals to the other groups in those areas.

It would be beyond interesting and relevant to find any areas of the brain in which people with gender dysphoria were different from people without gender dysphoria.

It is worth noting that the FtM transsexuals were all sexually attracted to females while the females were all attracted to males and the males were all attracted to females.

Thus the study was also comparing the brains of two groups of people attracted to males and one group of people attracted to females. The differences they found could be related to sexual orientation.

It is not clear what these differences mean, what caused them, or what their significance would be in brain function.

You can stop here if you just want the gist of the results. Otherwise, back to the study:

The study found sex differences in the fractional anisotropy (FA) values of white matter in four bundles of nerves with males having a higher FA value. The white matter structures with a higher FA value for males were the anterior** and posterior parts of the right superior longitudinal fasciculus, the forceps minor (right), and the corticospinal tract.***

In three of these four nerve areas, FtM transsexuals had FA values that were significantly larger than females and not significantly different from males.

In the inferior corticospinal tract, FtM transsexuals had FA values that were significantly larger than females and significantly smaller than males.

The authors conclude:

“…the main result of our study is that untreated FtM transsexuals differed from control females in two associative fasciculi (superior longitudinal fasciculus and forceps minor) and in the corticospinal tract. In contrast they only differed from control males in the corticospinal tract. These findings indicates that prior to hormonal cross-sex treatment the white matter microstructure of associative fascicles in untreated FtM transsexuals is more like that of individuals with the same gender identity than of individuals with the same biological sex.”

Their fascicles are also more like that of individuals with the same sexual orientation. We can not conclude that the cause is their gender identity, at least not from this data. We need more research in this area.

It is worth noting that we do not know what exactly made the white matter microstructures develop the way they did. It could be due to hormones or experience or an interaction of the two.

In addition, the microstructure in FtMs might have been affected by a different factor than the microstructure in males.

Finally, in the case of the corticospinal tract, it is possible that FtM transssexuals had white matter that developed like the control males, but then something caused their FA values to decrease. Changes in FA values can be due to age or illnesses, including depression or excessive alcohol consumption.

What do the differences they found mean practically?

This study found a sex difference in the FA values for the following fasciculi (bundles of nerves):

Superior longitudinal fasciculus (right, anterior and posterior) – a pair of long bundles of neurons connecting the front and back of the cerebrum (cerebrum=most of your brain). It is connected to many parts of the brain. One of its functions is to integrate auditory and speech nuclei.

Forceps minor (right) – a fiber bundle that connects that lateral and medial surfaces of the frontal lobes of the brain. It is part of the corpus collosum. The corpus collosum is responsible for interhemispheric sensory and auditory connectivity.

Corticalspinal tract (right) – connects the brain to the spinal cord. It is responsible for voluntary movement.

Looking at these descriptions, this study found sex differences in the nerves that connect the front and back of the brain, the nerves that connect the two hemispheres, and nerves that connect the brain to the spinal column.

It’s hard to predict how differences in these parts of the brain would affect men’s and women’s cognitive abilities and personalities.

The difference was found only on the right side of the brain. Does this mean anything? Maybe. According to the authors:

“Regarding brain laterality, we found that all the FA value decreases in women compared to men are seen in the right hemisphere. Similar asymmetries are also reported by Schmithorst et al. (2008), they described lower FA values in girls than in boys, and although there were decreases on both sides, the largest lost FA value clusters were on the right, indicating a right hemispheric predominance in sex differences. More recently Huster et al. (2009), focusing on the midcingulum bundle, found lower FA values in the right hemisphere than in the left and in women than in men.”

What specifically is the difference they observed in these bundles of nerves? What are FA values?

In another study, the authors say that FA values are “related to the ordered arrangement of myelinated fibers” and “an indication of white matter coherence and axonal integration.” Wikipedia says that FA is thought to reflect fiber density, axonal diameter, and myelination in white matter.

So finding higher FA values for males in certain bundles of nerves could mean that they have more dense nerve connections there or that those nerve connections are fatter or that they have more or fatter myelin sheaths. It might mean that the nerve connections in those bundles are more orderly, coherent, and integrated.

The next question, of course, is what does it mean if you have more or fatter or more coherent nerve connections between the front and back of your brain? between the two hemispheres? going to your spine?

Or, to look at it in terms of function, if the white matter responsible for voluntary movement is more coherent in males, it might give them faster reflexes. On the other hand, what does it mean if the white matter that connects auditory and speech nuclei is more coherent in males? It sounds like it ought to make it easier for males to process language.

My basic conclusion from all this is that we have found a sex difference in the brain, but we don’t really know what it means.

The authors try to connect their findings to differences in spatial abilities and verbal fluency, because the superior longitudinal fasciculus is “involved in the integration of inputs from multiple modalities and is a component of the network for spatial awareness that plays a major role in the visual and oculomotor aspects of spatial function such as spatial attention and spatial working memory.”

It might be, but there are a lot of other cognitive functions that use the integrations of inputs from multiple modalities. We have no way of knowing if the connections they observed were for spatial ability or giving a speech or cooking dinner without burning yourself.

I think they are overreaching in their conclusion here.

The authors also discuss the difference they found in the forceps minor. Again, I think it’s hard to know what exactly a sex difference here would mean; the forceps minor connects the two halves of the prefrontal cortex which controls our behavior. Does having more connectivity on the right make men better at controlling themselves or integrating their emotions?

The forceps is part of the corpus collosum. Another study found differences related to sexual orientation in this area of the brain. It is important to make sure that any differences found in this study are not due to sexual orientation.

The authors refer to a study which found that the shape of the corpus collousm in transsexual individuals matched their gender identity not their biological sex. I can only see the abstract of that study, so I don’t know if they looked at the sexual orientation of the people in that study.

Anyhow, here is the discussion of the forceps minor by the authors:

“The forceps minor connects, via the genu of the CC, orbitofrontal regions ( Park et al., 2008) involved in emotional functions and behavioral control. Kringelbach and Roll (2004), suggested that orbital cortex activity is related to the reward value of reinforcers and punishers.

The forceps minor is a part of the anterior region of the corpus callosum. The CC is the major interhemispheric pathway in the human brain and integrates sensory, motor, cognitive and emotional functions from both hemispheres; the isthmal area of the CC is larger in homosexual than in heterosexual males ( Witelson et al., 2008). FA values in the anterior part of the CC change during development ( Lebel et al., 2008). In a sample of children and adolescents, it was reported that girls have lower FA values than boys in the anterior CC region ( Schmithorst et al., 2008). In addition, the boys had lower FA values than girls in a small region of the splenium. We did not observe differences in the splenium between adult male and female controls.

There are only a couple of studies on the transsexual CC. Studying the CC shape, it was concluded that the shape in transsexuals is more similar to their gender identity than to their biological sex ( Yokota et al., 2005). However, when the whole CC surface was studied no differences in CC -regardless of genetic sex or gender- were reported (Emory et al., 1991). Our results cannot be compared to these works, which used surface measurements, while we have used FA analysis, which seems to be a more suitable technique for detecting microstructural white matter differences.”

The authors say less about the corticospinal tract, but they mention that genes and motor experience interact in its development. This is an area where FtM transsexuals were in-between male and female controls, so perhaps they are suggesting that the males had more practice at motor skills.

Of course all of the sex differences found in this study could be related to experience or an interaction of genes and experiences.

The authors of this study imply that the sex differences they found were caused by hormones early in development, but we can’t actually know that.

This study had a couple of serious weaknesses.

1. They did not look for any general differences between the brains of trans and cis people, they only looked at how trans men compared to males and females in areas where they found a sex difference. This assumes that gender dysphoria is caused by something related to hormones – which is what the authors want to prove.

It would be helpful if future studies look at both issues – sex differences and general differences between cis and trans people. Perhaps the authors could of this study would be able to use the data they collected to do this.

2. They did not include any cis lesbians as control groups, although all of the FtM transsexuals were attracted to women. Without doing this, we can not be sure if the similarities between the FtM transsexuals and cis men attracted to women are caused by gender identity or sexual orientation.

The study also has some strengths.

1. They used only trans men who had not yet taken hormones. We know that taking cross-sex hormones changes your brain. (Early studies of gender identity and the brain used people who had already been on hormones.)

2. They tested the actual hormone levels of the FtMs before the brain scans. A Japanese study found that many of the trans men who came to their clinic had poly-cystic ovarian syndrome (PCOS). PCOS can lead to elevated levels of androgens which would confuse the results.

3. Everyone in the study was right-handed.

Original Article:

White matter microstructure in female to male transsexuals before cross-sex hormone treatment. A diffusion tensor imaging study by Rametti G, Carrillo B, Gómez-Gil E, Junque C, Segovia S, Gomez Á, Guillamon A in J Psychiatr Res. 2011 Feb;45(2):199-204.

* I am following the language used in the study to refer to trans men and control subjects.

** The abstract says that the white matter was different in the medial and posterior parts of the superior longitudinal fasciculus, but  in the text of the study, the results discuss the anterior and posterior parts. Anterior and posterior refer to front and back while medial means in the middle, so it makes more sense to talk about the anterior and posterior parts of the nerve bundle. I think they made an error in the abstract.

***A later study of white matter in MtF transsexuals found a sex difference in the same three bundles of nerves. They found a sex difference in three additional areas as well: the left superior longitudinal fasciculus, the right inferior front-occipital fasciculus, and the left cingulum. It’s not clear why one study found more sex differences in white matter than the other did. (The earlier study was done by the same people using the same methodology but different control groups.)

 

P.S. A fun link on the map of the connections of white matter in young men’s brains.

Sexual Orientation and the Brain – Links to studies

A number of studies have found differences in the brain that may be related to sexual orientation.

Because of this, studies of gender identity and the brain need to carefully control for sexual orientation.

It is important to remember that the majority of trans men (born female) are primarily attracted to women while only about 5% of cis women are primarily attracted to women. Thus if you find differences between trans men and a randomly selected group of females, the differences could be due to gender identity or sexual orientation.

Similarly, about half of trans women (born male) are attracted to men while only about 5% of cis men are primarily attracted to men. Again, differences found in studies of the brain could be due to gender identity or sexual orientation.

So far, I have found no studies of the brain and gender identity that included gay and lesbian controls.

Many studies discuss the sexual orientation of the trans people; some studies look only at trans women who are attracted to men or trans women who are attracted to women, but that is only half of what needs to be done.

A group of trans women who are all attracted to men is still different from your average group of cis men in two ways – gender identity and sexual orientation.

The studies listed below are proof this issue matters. We know that sexual orientation can affect the brain.

I have not read these studies, this is just a list of links for you to enjoy.

Sexual orientation and the size of the anterior commissure in the human brain by L.S. Allen, R.A. Gorski in Proc. Natl. Acad. Sci. U. S. A., 89 (1992), pp. 7199–7202.

A fiber tract that is larger in women than in men was even larger in gay men. (But the gay men had died of AIDs).

The interstitial nuclei of the human anterior hypothalamus: an investigation of variation with sex, sexual orientation, and HIV status by W. Byne, S. Tobet, L.A. Mattiace, M.S. Lasco, E. Kemether, M.A. Edgar, S. Morgello, M.S. Buchsbaum, L.B. Jones in Horm. Behav., 40 (2001), pp. 86–92.

HIV status affected the size of the INAH1 cell group. The INAH3 cell group was bigger in presumed straight males than females and contained more neurons. There was a trend for INAH3 to have a larger volume in straight males than gay males, but they had the same number of neurons in the INAH3.

A difference in hypothalamic structure between heterosexual and homosexual men by S. LeVay in Science, 253 (1991), pp. 1034–1037.

The INAH3 cell group in the hypothalmus was bigger in men than women. It was also bigger in the brains of presumed straight men than in the brains of gay men.

Homosexual women have less grey matter in perirhinal cortex than heterosexual women by J. Ponseti, H.R. Siebner, S. Kloppel, S. Wolff, O. Granert, O. Jansen, H.M. Mehdorn, H.A. Bosinski in PLoS. ONE, 2 (2007), p. e762.

Women had more gray matter than men in a number of areas. In three areas straight women had more gray matter than lesbians; in one of these areas men also had less gray matter than women.

“The perirhinal cortex is located close to entorhinal cortex, hippocampus, parahippocampal gyrus and amygdala, and is known to be involved in a variety of functions like olfactory processing, memory encoding and spatial processing. These functions are related to the processing of sexual stimuli as well.”

PET and MRI show differences in cerebral asymmetry and functional connectivity between homo- and heterosexual subjects by I. Savic, P. Lindstrom in Proc. Natl. Acad Sci. U. S. A., 105 (2008), pp. 9403–9408.

Straight men and lesbians had a rightward cerebral asymmetry, gay men and straight women did not.

“Homosexual subjects also showed sex-atypical amygdala connections. In HoM, as in HeW, the connections were more widespread from the left amygdala; in HoW and HeM, on the other hand, from the right amygdala. Furthermore, in HoM and HeW the connections were primarily displayed with the contralateral amygdala and the anterior cingulate, in HeM and HoW with the caudate, putamen, and the prefrontal cortex. The present study shows sex-atypical cerebral asymmetry and functional connections in homosexual subjects.”

An enlarged suprachiasmatic nucleus in homosexual men by D.F. Swaab, M.A. Hofman in Brain Res., 537 (1990), pp. 141–148.

A nucleus in the hypothalmus is larger in gay men than straight men. A different nucleus that is sexually dimorphic was the same size in gay and straight men.

Corpus callosum anatomy in right-handed homosexual and heterosexual men by S.F. Witelson, D.L. Kigar, A. Scamvougeras, D.M. Kideckel, B. Buck, P.L. Stanchev, M. Bronskill, S. Black in Arch. Sex Behav., 37 (2008), pp. 857–863.

The isthmal area in the corpus callosum was larger for a group of gay men compared to straight men.

The citations for these studies are from the study Regional gray matter variation in male-to-female transsexualism by Luders E, Sánchez FJ, Gaser C, Toga AW, Narr KL, Hamilton LS, Vilain E. in Neuroimage. 2009 Jul 15;46(4):904-7. I reviewed the study here.

Brains of Children with Autism Fail to Trim Synapses – NY Times article and a Question

A fascinating article in the NYTimes about a new study of children with autism.

A few interesting points:

Babies grow many synapses connecting the neurons in their brain. As they grow up, they prune these synapses.

It looks like autistic children may not prune these synapses as well as other children and teenagers do. Their problems with social learning may be due to having too many connections in the brain.

They may also have a problem clearing out old and degraded cells.

From the NYT article:

“‘Impairments that we see in autism seem to be partly due to different parts of the brain talking too much to each other,” he said. “You need to lose connections in order to develop a fine-tuned system of brain networks, because if all parts of the brain talk to all parts of the brain, all you get is noise.'”

This overconnectivity in the brain could explain “symptoms like oversensitivity to noise or social experiences, as well as why many people with autism also have epileptic seizures.”

More than a third of people with autism have epilepsy!!!!

Is there any connection between this and gender dysphoria?

Probably not, but it is interesting to speculate. What if gender dysphoria is also caused by overconnectivity in the brain, just less of it? Perhaps gender dysphoria is caused by too many connections in just one part of the brain. That might explain why there are more people than you would expect with both ASDs and gender dysphoria. Something for someone to research, perhaps.

It might also be interesting to find out if people with gender dysphoria have a higher rate of epilepsy than expected.

Effects of cross-sex hormone treatment on cortical thickness in transsexual individuals – Review of Abstract

This is an interesting study that found that taking cross-sex hormones changed the thickness of the cortex in the brain.

I have only been able to see the abstract; the study was published in May 2014 and I do not have access to it.

The study looked at 15 trans men (born female) before and after they took testosterone for at least six months. They also looked at 14 trans women (born male) before and after they took androgen blockers and estrogens for at least six months.

They found that :

“After testosterone treatment, FtMs (trans men) showed increases of CTh bilaterally in the postcentral gyrus and unilaterally in the inferior parietal, lingual, pericalcarine, and supramarginal areas of the left hemisphere and the rostral middle frontal and the cuneus region of the right hemisphere. There was a significant positive correlation between the serum testosterone and free testosterone index changes and CTh changes in parieto-temporo-occipital regions. In contrast, MtFs (trans women), after estrogens and antiandrogens treatment, showed a general decrease in CTh and subcortical volumetric measures and an increase in the volume of the ventricles.”

In other words, taking testosterone makes certain areas of your brain thicker and more testosterone changes your brain more.

Blocking testosterone and taking estrogens makes certain areas of your brain shrink. According to the abstract, this makes the ventricles get bigger – the ventricles are a network of cavities in the brain that contain cerebrospinal fluid.

We already know that there are sex differences in the thickness of the brain’s cortex, although we don’t know exactly what they mean. (You can read more about cortical thickness and what it might mean here.)

Thus study suggests that some of the sex differences we observe in the brain are related to the hormones in our bodies. Our brains are not set in stone by pre-natal exposure to hormones.

For transgender people this study shows that hormone therapy will change your brain.

It does not tell us what that will means in terms of changes in thoughts, feelings, or behaviors.

It’s also not clear if the changes in the trans women’s brains are caused by reducing the testosterone level or adding estrogen or both.

The abstract does not discuss whether the changes caused by the cross-sex hormones make the brain more “masculine” or “feminine” or neither.

It looks like this study is a follow-up to an earlier study, Cortical Thickness in Untreated Transsexuals. The earlier study found that before hormone therapy there were differences between transsexuals and control groups.

The differences the authors found in their earlier study were fairly complicated:

“We would suggest that transsexuals do not show a simple masculinization (FtMs) or feminization (MtFs) of their brains—rather, they present a complex picture in their process of sexual differentiation depending on the brain region studied and the kind of measurements taken.”

In other words, there were some ways in which trans men have brains like cis men’s and some ways in which their brains are like cis women’s while trans women have brains that are like cis women’s in some ways and like cis men’s in others.

One caveat to the pre-hormone part of the study – the authors only included people who were “erotically attracted to subjects with the same anatomical sex.” Thus, it is possible that the brain differences they observed were caused by sexual orientation, not gender identity.

Many studies of gender identity and the brain make this mistake. For example, they will compare a group of trans men who are attracted to women to a group of cis men who are attracted to women and a group of cis women who are attracted to men. It makes it impossible to be sure if any differences between the brains of trans men and cis women are due to gender identity or sexual orientation.

Studies of gender identity and the brain should include control groups of lesbians and gay men as well as straight people.

In any case, the current study shows that taking cross-sex hormones will further change the brain.

Original Article (Abstract):

Effects of cross-sex hormone treatment on cortical thickness in transsexual individuals by Zubiaurre-Elorza L, Junque C, Gómez-Gil E, Guillamon A in J Sex Med. 2014 May;11(5):1248-61.

Related blog post – Increased Cortical Thickness in Male-to-Female Transsexualism – A Review and a Hypothesis.