We Are Our Brains (12 page)

Transsexuals feel that they have been born into a body of the wrong gender and are desperate for a sex change or gender reassignment. This is a gradual process that starts with an individual adopting the social role of the opposite sex and taking hormones, then undergoing a series of extensive operations—which only 0.4 percent later regret. The first person in the Netherlands to respond to the plight of transsexuals was Otto de Vaal, an endocrinologist and pharmacologist who taught at the University of Amsterdam. He treated them for free starting in 1965, feeling that his university pay was sufficient. The gender team of the VU University Medical Center in Amsterdam (VUmc) subsequently took on a pioneering role, headed first by Louis Gooren and now by Peggy Cohen-Kettenis. That's remarkable in itself because the Vrije Universiteit was established as a Calvinist university, and the Bible does say: “A woman shall not wear man's clothing, nor shall a man put on a woman's clothing; for whoever does these things is an abomination to the Lord your God” (Deuteronomy 22:5–6).

Since 1975, 3,500 people have undergone gender reassignment at the VUmc. The first time I learned about transsexuality was as a medical student in the 1960s. Coen van Emde Boas, a professor of sexology, entered the lecture room of the obstetrics and gynecology department with a bearded man. It wasn't exactly the place you would expect a man to be demonstrating anything. But he turned out to be a genetic woman, a female-to-male transsexual. This made a deep impression on me, and set me thinking about the possible underlying mechanism.

Male-to-female transsexuality (MtF) occurs in 1 in 10,000 individuals, and female-to-male transsexuality (FtM) in 1 in 30,000. Gender problems tend to become apparent from an early age. Mothers typically relate how their little boys dressed up in their frocks and shoes, were only interested in girls' toys, and mainly played with girls. But not all children with gender problems want to change sex later. If necessary, puberty can be delayed with the help of hormones to gain extra time in which to decide whether or not to undergo treatment.

All the data indicates that gender problems arise in the womb. Tiny variations in genes associated with the effect of hormones on brain development have been found to increase the likelihood of transsexuality. It can also be increased by abnormal fetal hormone levels or by medication taken during pregnancy that inhibits the breakdown of sex hormones. The differentiation of our sex organs takes place in the first months of pregnancy, while the sexual differentiation of the brain occurs in the second half of pregnancy. Since these two processes take place at different times, the theory is that in the case of transsexuality, they have been influenced independently of one another. If this is the case, one would expect to find female structures in the brains of MtF transsexuals and vice versa in the case of FtM transsexuals. In 1995 we indeed found, in postmortem studies of donor brains, a small structure in which the usual sex difference was reversed. We published our findings in
Nature.
The brain structure in question is the bed nucleus of the stria terminalis (BST), an area that's involved in many aspects of sexual behavior (
figs. 10
and
11
). The central part of this nucleus, the BSTc, is twice as large in men as in women and contains twice as many neurons. We found MtF transsexuals to have a “female” BSTc. The only FtM transsexual we could study—the material in question being yet rarer than the brains of MtF transsexuals—indeed proved to have a “male” BSTc. We were able to rule out the reversal of the sex difference in transsexuals being caused by altered hormone levels in adulthood, so the reversal must have happened at the developmental stage.

If you publish something truly interesting, the nicest thing you'll probably hear your colleagues say is, “It'll need to be confirmed by an independent research group.” And that can take a while, because it took me twenty years to collect the brain material for my study. So I was delighted when in 2008 the group headed by Ivanka Savic in Stockholm published a study involving functional brain scans of living MtF transsexuals. They had not yet been operated on, nor given hormones. As a stimulus they were given male and female pheromones, scents that aren't consciously perceived. In control groups,
these were shown to produce different patterns of stimulation in the hypothalamus and other brain areas in men and women. The stimulation pattern for MtF transsexuals fell between that of men and women.

In 2007 V. S. Ramachandran published an interesting hypothesis and provisional research findings on transsexuality. He believes that the neural body map of MtF transsexuals lacks a penis, while that of FtM transsexuals lacks breasts, due to these not being programmed into the map during development. As a result, they don't recognize these organs as their own and want to get rid of them. So everything indicates that the early development of sexual differentiation in the
brains of transsexuals is atypical and that they aren't, in fact, simply psychotic, as a Dutch psychiatrist was impertinent enough to claim recently. At the same time it is of course essential, before initiating treatment, to make sure that the desire to change sex isn't part of a psychosis, as it can be an occasional symptom of schizophrenia, bipolar depressions, and serious personality disorders.

FIGURE 10.
Located at the tip of the lateral ventricle (1) is the bed nucleus of the stria terminalis (BST), a region of the brain important for sexual behavior.

FIGURE 11.
The central part of the bed nucleus of the stria terminalis (BSTc) (see
fig. 10
for location) is twice as big in men (A, C) and contains twice as many neurons as in women (B). In male-to-female transsexuals we found a female BSTc (D). The only female-to-male transsexual we could study (these brains being rarer than those of MtF transsexuals) indeed proved to have a male BSTc. This reversal of the sex difference in transsexuals corresponds with their gender identity (the feeling of being a man or woman) rather than with their chromosomal sex, or the sex on their birth certificate. LV = lateral ventricle, BSTm = medial section of the BST. J-N Zhou et al.,
Nature
378 (1995): 68–70.

The shocking scale of child abuse within the Catholic Church has come to light in recent years. The first cases emerged in the United States, then in Ireland, where, within the bishopric of Dublin alone, hundreds of children were abused between 1976 and 2004. Cases in Germany were subsequently exposed, after which hundreds of victims came forward in the Netherlands. These revelations show that, as a result of the taboo surrounding pedophilia, we have no idea how frequently such abuse actually occurs—not just in the church but in general.

Pedophilia can have different causes. If an adult suddenly experiences pedophilic urges, they may have a brain tumor in the prefrontal cortex, temporal cortex, or hypothalamus. Sometimes it is a symptom of dementia. A sudden switch in sexual inclination to pedophilia has also been caused by operations to cure epilepsy by removing part of the anterior temporal lobe. Such patients can go on to develop Klüver-Bucy syndrome, which involves the loss of sexual inhibition (see
chapter 4
). In the United States, a man who started to download child pornography after an operation of this kind was recently sentenced to nineteen months of imprisonment! Pedophilia can also be caused by infections of the brain, Parkinson's, multiple sclerosis, and brain trauma.

But a neurological cause for pedophilia is rare. Most pedophiles have always been attracted to children, and the cause can be traced to fetal brain development and early development after birth. Just as gender identity and sexual orientation are determined by genetic background and the interaction between a fetus's sex hormones and its developing brain (see earlier in this chapter), so too pedophilia can apparently be explained by genetic and other factors causing the brain to develop abnormally at an early stage, leading to structural differences. I was once shown a family tree that included three generations of pedophile men. Deviant sexual behavior (like pedophilia) is displayed by a high percentage (18 percent) of first-degree relatives of pedophiles, pointing to a genetic factor. In addition, pedophiles are more likely to have been sexually abused by adults as young children. At the end of 2009, the leader of the Northern Irish party Sinn Féin, Gerry Adams, went public with the painful family secret that his father had abused his own children, while his brother was in turn suspected of having sexually abused his daughter. Whether abuse as a child is a causal factor in the development of pedophilia in adulthood, or whether there's a genetic factor in such families, still needs to be investigated.

Daniel Gajdusek (1923–2008), a man of remarkable talent who studied physics, biology, mathematics, and medicine in the United States, thought that abuse as a child could cause pedophilia. He had himself been abused by an uncle as a child. I once had the dubious honor of chairing a lecture by the hypomanic Gajdusek; my colleagues were amused by my vain attempts to keep him in check. Gajdusek had been researching the cause of mass deaths of young women and children from the disease kuru in villages in the interior of New Guinea in 1957. At the time, it was still a Dutch colony, and he was able to find his way there using Dutch ordnance survey maps that he'd stolen from the Leiden endocrinology department headed by Dries Querido. Gajdusek discovered that the deaths were indirectly caused by cannibalism. Long after they had eaten the brains of conquered enemies, the victims were struck down by a slow-acting
virus, one of whose symptoms was dementia. The disease turned out to be caused by prions (infectious agents made of protein), just like mad cow disease. In 1996 Gajdusek was awarded the Nobel Prize for Medicine. However, when he returned from New Guinea and other remote locations it wasn't just with brain tissue for further research; he also brought back fifty-six children, mostly little boys. We always thought this was very odd. He took them into his home and gave them an education but, as an accusation made by a man who had lived with him as a child later revealed, also molested them. He was imprisoned for a year and died in 2008.

There are all kinds of factors in early development that could influence the risk of developing pedophilia. It would seem logical to study them, but the taboo on this condition stands in the way. Who in our society would dare openly admit to being a pedophile and take part in research into the causes of this disorder?

In recent years, the first structural differences have been reported between the brains of pedophiles and those of control groups. A study involving magnetic resonance imaging (MRI) showed that the former have less gray matter (neurons) in various areas of the brain, like the hypothalamus, the bed nucleus of the stria terminalis (whose size also differs in transsexuals; see earlier in this chapter), and the amygdala, which plays a role in sex, fear, and aggressive behavior. It moreover emerged that the smaller the amygdala, the more likely an individual was to commit pedophilic crimes. Exposure to emotional and erotic images of adults sparks less activity in the hypothalamus and prefrontal cortex of pedophile men than in control men, which ties in with the fact that pedophiles are less sexually interested in adults. Convicted pedophiles display greater amygdala activity than control men in response to images of children. Functional scans of the brains of homosexual, heterosexual, and pedophile men shown pictures of men, women, girls, and boys moreover show a clear difference between these groups in terms of brain activity. However, we must bear in mind that research into pedophilia focuses solely on
a small, selected group of pedophiles. The majority are able to control their urges, don't commit crimes, and therefore aren't studied.