̽��ֱ�� of Cambridge - sex

Sex differences in brain structure present at birth

Anonymous — Tue, 07 Jan 2025 08:00:33 +0000

While male brains tended to be greater in volume than female brains, when adjusted for total brain volume, female infants on average had significantly more grey matter, while male infants on average had significantly more white matter in their brains.

Grey matter is made up of neuron cell bodies and dendrites and is responsible for processing and interpreting information, such as sensation, perception, learning, speech, and cognition. White matter is made up of axons, which are long nerve fibres that connect neurons together from different parts of the brain.

Yumnah Khan, a PhD student at the Autism Research Centre, who led the study, said: “Our study settles an age-old question of whether male and female brains differ at birth. We know there are differences in the brains of older children and adults, but our findings show that they are already present in the earliest days of life.

“Because these sex differences are evident so soon after birth, they might in part reflect biological sex differences during prenatal brain development, which then interact with environmental experiences over time to shape further sex differences in the brain.”

One problem that has plagued past research in this area is sample size. ̽��ֱ��Cambridge team tackled this by analysing data from the Developing Human Connectome Project, where infants receive an MRI brain scan soon after birth. Having over 500 newborn babies in the study means that, statistically, the sample is ideal for detecting sex differences if they are present.

A second problem is whether any observed sex differences could be due to other factors, such as differences in body size. ̽��ֱ��Cambridge team found that, on average, male infants had significantly larger brain volumes than did females, and this was true even after sex differences in birth weight were taken into account.

After taking this difference in total brain volume into account, at a regional level, females on average showed larger volumes in grey matter areas related to memory and emotional regulation, while males on average had larger volumes in grey matter areas involved in sensory processing and motor control.

̽��ֱ��findings of the study, the largest to date to investigate this question, are published in the journal Biology of Sex Differences.

Dr Alex Tsompanidis who supervised the study, said: “This is the largest such study to date, and we took additional factors into account, such as birth weight, to ensure that these differences are specific to the brain and not due to general size differences between the sexes.

“To understand why males and females show differences in their relative grey and white matter volume, we are now studying the conditions of the prenatal environment, using population birth records, as well as in vitro cellular models of the developing brain. This will help us compare the progression of male and female pregnancies and determine if specific biological factors, such as hormones or the placenta, contribute to the differences we see in the brain.”

̽��ֱ��researchers stress that the differences between males and females are average differences.

Dr Carrie Allison, Deputy Director of the Autism Research Centre, said: “ ̽��ֱ��differences we see do not apply to all males or all females, but are only seen when you compare groups of males and females together. There is a lot a variation within, and a lot of overlap between, each group.”

Professor Simon Baron-Cohen, Director of the Autism Research Centre, added: “These differences do not imply the brains of males and females are better or worse. It’s just one example of neurodiversity. This research may be helpful in understanding other kinds of neurodiversity, such as the brain in children who are later diagnosed as autistic, since this is diagnosed more often in males.”

̽��ֱ��research was funded by Cambridge ̽��ֱ�� Development and Research, Trinity College, Cambridge, the Cambridge Trust, and the Simons Foundation Autism Research Initiative.

Reference
Khan, Y T, Tsompanidis, A, Radecki, M A, et al. Sex differences in human brain structure at birth. Biol Sex Differ; 17 Oct 2024; DOI: 10.1186/s13293-024-00657-5

Sex differences in brain structure are present from birth, research from the Autism Research Centre at the ̽��ֱ�� of Cambridge has shown.

We know there are differences in the brains of older children and adults, but our findings show that they are already present in the earliest days of life

Yumnah Khan

Chayene Rafaela

Photograph of a young girl hugging a baby boy

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Not so 'swinging sixties' revealed by study of UK's first sexual health clinics

ta385 — Thu, 20 Jan 2022 08:00:00 +0000

Young people behaving responsibly in the 1960s helped to defeat fierce opposition to the UK’s first sexual health clinics, the Brook Advisory Centres, a new study argues.

Sex and the brain: fruitless research?

cjb250 — Wed, 01 Jun 2016 23:01:34 +0000

̽��ֱ��sex life of the fruit fly is a simple affair. If a fly smells male pheromones, regardless of whether it is a male or a female fly, its response is clear and consistent. ̽��ֱ��pheromones activate different clusters of neurons in the brains of male and female flies and so, as a female fly, it would engage in courtship behaviour or as a male fly, it would become more aggressive. But the differences do not end here.

̽��ֱ��fruit fly carries an important gene nicknamed ‘fruitless’. It’s the master gene that controls the male fruit fly’s courtship ritual; when disabled, male flies don’t mate. In contrast, when the gene is activated in females, they show male courtship behaviour and begin wooing other females.

For humans, the story is far more complex and the study of sex differences in the brain is more controversial, and more emotionally laden than in any other species. This hot topic is frequently misrepresented in the media. Studies on sex differences are often oversimplified and taken out of context. For example, some articles claiming that we now know “why men are so obsessed with sex” were merely reporting a study focused on worms. This style of reporting promotes stereotypes and misconception of science. ̽��ֱ��truth is that the brains of men and women have a lot in common.

̽��ֱ��Royal Society recently released a special issue on sex differences in the brain. It features an opinion piece which argues that human brains do not fall into the two distinct categories of male and female. ̽��ֱ��piece is partly based on a study from last year: a revolutionary analysis on some 1,400 human brains. ̽��ֱ��authors looked at the volume of brain regions and connectivity between them to select the areas that differed most between the sexes. For each area, the researchers then designated the upper and lower ends of the spectrum as either ‘male’ or ‘female’, according to where men or women were more prevalent. If brains truly fell into two distinct categories, we would see brains which had either all ‘male’ or all ‘female’ areas. ̽��ֱ��study revealed that such consistent brains are indeed rare. Our brains are more like a patchwork quilt, with most people having a mixture of features that are ‘typical’ male or female, or common to both sexes.

Biology alone cannot explain why our brains are such a colourful mixture; we also need to consider the environment. How stressed was your mother during pregnancy? Did you grow up with close friends? How often did you exercise? All these factors will influence the development of your brain and consequently its appearance today. Even as an adult, your daily experiences shape the anatomy of your brain.

Despite the patchwork structure of our brains, there seem to be differences in brain anatomy between the average man and woman. But do these differences necessarily cause different behaviours? Actions such as mating, navigating through London, or writing an essay are controlled by complex networks. ̽��ֱ��underlying anatomy is important, but so are other internal and external influences, such as stress, hunger, or exhaustion. Our behaviour is shaped by many pathways.

Geert de Vries, director of the Neuroscience Institute at Georgia State ̽��ֱ��, has another take on sex differences in the brain. He argues that these differences do not produce, but instead prevent differences in behaviour. According to de Vries, men and women differ dramatically in their physiology and hormones; having different brains might be a way of compensating for these differences. Do male and female brains develop differently in order to promote similar behaviour?

We do not know if these structural differences really are compensatory. However, this concept is not new and we can observe such compensations on other levels. For example, female mammals have two copies of the X chromosome in their cells, while males only receive one copy. If all chromosomes were equally active, females would make twice as many gene products from their X chromosomes as males. To prevent this, females silence one of their X chromosomes, a process known as X-inactivation. A similar process might happen with brain structures on a more complex level.

So our brains are not distinctly male or female, and structural differences do not necessarily cause behavioural differences. Then why study sex differences at all? There are five times more studies with all-male than all-female animals in neuroscience and pharmacology; only one in four studies includes animals of both sexes. Researchers worry that hormonal fluctuations in females could confound their results, and often believe that sex differences are irrelevant for the research question. However, results from males do not always apply to females. Some drugs such as aspirin are taken up or cleared away differently in men and women. Sex is also important for some diseases: multiple sclerosis is more common in women, as are depression and anorexia. On the other hand, autism and some addictions are more common in males.

Clearly it is not sufficient to investigate and address these questions by using subjects of only one sex. How can we expect to get the whole picture by looking at only one half of the population? Since 1993, the inclusion of women has been a requirement in clinical trials funded by the National Institutes of Health in the USA. Since 2014, all animal studies funded by them also have to include females. Many scientific journals now ask authors to publish the numbers of males and females included in their sample.

Steps like these are necessary to learn more about how sex and gender influence our development and eventually our brains. ̽��ֱ��findings need to be analysed and communicated carefully. Men and women might be different in subtle ways, but our similarities probably outweigh the differences. A small change in your complex anatomy would usually not reverse your behaviour – after all, you’re not a fruit fly!

This is an edited version of the article Does your brain have a sex?

̽��ֱ��male and female brains have more in common than media reports often suggest, argues Julia Gottwald, a third year PhD student at the Department of Psychiatry. Writing in the student science magazine BlueSci, she explains what we understand about the similarities and differences in our brains and why this is an important area of research.

Our brains are not distinctly male or female, and structural differences do not necessarily cause behavioural differences. Then why study sex differences at all?

Julia Gottwald

Oran Maguire, BlueSci

Brains

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Opinion: Losing your virginity: how we discovered that genes could play a part

Anonymous — Fri, 15 Apr 2016 08:13:05 +0000

As far as big life decisions go, choosing when to lose your virginity or the best time start a family are probably right up there for most people. It may seem that such decisions are mostly driven by social factors, such as whether you’ve met the right partner, social pressure or even your financial situation. But scientists are increasingly realising that such sexual milestones are also influenced by our genes.

In a new study of more than 125,000 people, published in Nature Genetics, we identified gene variants that affect when we start puberty, lose our virginity and have our first child. This is hugely important as the timing of these events affect educational achievements as well as physical and mental health.

Children can start puberty at any time between eight and 14-years-old. Yet it is only in recent years that we have begun to understand the biological reasons for this. Through studies of both animals and humans, we now know that there’s a complex molecular machinery in the brain that silences puberty hormones until the right time. At this point, chemical messengers secreted from the brain begin a cascade of events, leading to the production of sex hormones and reproductive maturity.

Human genetics studies have identified many genes that are linked to individual differences in the onset of puberty. There are broadly two approaches used to map such genes – studies of patients affected by rare disorders that affect puberty and large-scale population studies. ̽��ֱ��former is helpful because it can investigate gene variants that cause extremely early or delayed/absent puberty.

In previous research, we used population studies to survey a large number of individuals using questionnaires and then genome-wide association studies to scan these same participants for common genetic differences. We could then assess whether the participants' reported age at puberty was related to particular gene variants. In this way, we have in a number of studies identified more than 100 such variants, each modifying puberty timing by just a few weeks. However, together they contribute substantially.

We now understand that both nature and nurture play a roughly equal role in regulating the timing of puberty. For example, studies have consistently shown that obesity and excessive nutrition in children can cause an early onset of puberty.

Genetic factors

However, we know far less about the biological and genetic factors behind the ages that we first have sexual intercourse or have a first child. This is because previous research has focused more on environmental and family factors than genetics. But the launch of UK Biobank, a study with over half a million participants, has greatly helped to fill this lack of knowledge.

In our new study, we used this data to survey some 125,000 people in the same way as in the puberty studies. We found 38 gene variants associated with the age of first sexual intercourse. ̽��ֱ��genes that we identified fall broadly into two groups. One category is genes with known roles in other aspects of reproductive biology and pubertal development, such as the oestrogen receptors, a group of proteins found on cells in the reproductive tract and also in behaviour control centres of the brain.

If you went through puberty early you are more likely to have many children in life. Tom Adriaenssen/wikimedia, CC BY-SA

̽��ֱ��other group includes genes which play roles in brain development and personality. For example, the gene CADM2, which controls brain activity and also has strong effects on whether we regard ourselves to be risk-takers. We discovered that this gene was also associated with losing your virginity early and having a higher number of children throughout life. Similarly, the gene MSRA, linked to how irritable we are, was also associated with age at first sexual intercourse. Specifically, people who are more irritable typically have a later encounter. However, more research is needed to show exactly how these genes help regulate the timing of the reproductive milestones.

We were also able to quantify that around 25% of the variation in these milestones was due to genetic differences rather than other factors.

Implications for public health

An important reason why we study reproductive ageing is that these milestones impact reproductive outcomes and also broader health risks. Epidemiological studies show that individuals who go through puberty at younger ages have higher risks of many diseases of old age, such as diabetes, heart disease and breast cancer. Similarly, first sexual intercourse at an earlier age is linked to a number of adverse behavioural, educational and health outcomes.

Using a statistical genetics approach called Mendelian Randomisation, a technique that helps clarify the causal relationship between human characteristics, these studies can tell us whether such epidemiological associations are likely to be causal rather than just random associations. We managed to show that early puberty actually contributes to a higher likelihood of risk-taking behaviours, such as sexual intercourse at an earlier age. It was also linked to having children earlier, and having more children throughout life.

These findings, along with previous studies linking early puberty and loss of virginity to social and health risks, back the idea that future public health interventions should aim to help children avoid early puberty, for example by diet and physical activity and avoiding excess weight gain. Our findings predict that this would have benefits both on improving adolescent health and educational outcomes and also for future health at older ages.

John Perry, Senior Investigator Scientist, ̽��ֱ�� of Cambridge and Ken Ong, Group Leader of the Development Programme at the MRC Epidemiology Unit, ̽��ֱ�� of Cambridge

This article was originally published on ̽��ֱ��Conversation. Read the original article.

̽��ֱ��opinions expressed in this article are those of the individual author(s) and do not represent the views of the ̽��ֱ�� of Cambridge.

John Perry and Ken Ong (MRC Epidemiology Unit) discuss how sexual milestones are influenced by our genes and how this can impact on broader health risks.

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Brain activity in sex addiction mirrors that of drug addiction

cjb250 — Fri, 11 Jul 2014 18:00:00 +0000

Although precise estimates are unknown, previous studies have suggested that as many as one in 25 adults is affected by compulsive sexual behaviour, an obsession with sexual thoughts, feelings or behaviour which they are unable to control. This can have an impact on a person’s personal life and work, leading to significant distress and feelings of shame. Excessive use of pornography is one of the main features identified in many people with compulsive sexual behaviour. However, there is currently no formally accepted definition of diagnosing the condition.

In a study funded by the Wellcome Trust, researchers from the Department of Psychiatry at the ̽��ֱ�� of Cambridge looked at brain activity in nineteen male patients affected by compulsive sexual behaviour and compared them to the same number of healthy volunteers. ̽��ֱ��patients started watching pornography at earlier ages and in higher proportions relative to the healthy volunteers.

“ ̽��ֱ��patients in our trial were all people who had substantial difficulties controlling their sexual behaviour and this was having significant consequences for them, affecting their lives and relationships,” explains Dr Valerie Voon, a Wellcome Trust Intermediate Clinical Fellow at the ̽��ֱ�� of Cambridge. “In many ways, they show similarities in their behaviour to patients with drug addictions. We wanted to see if these similarities were reflected in brain activity, too.”

̽��ֱ��study participants were shown a series of short videos featuring either sexually explicit content or sports whilst their brain activity was monitored using functional magnetic resonance imaging (fMRI), which uses a blood oxygen level dependent (BOLD) signal to measure brain activity.

̽��ֱ��researchers found that three regions in particular were more active in the brains of the people with compulsive sexual behaviour compared with the healthy volunteers. Significantly, these regions – the ventral striatum, dorsal anterior cingulate and amygdala – were regions that are also particularly activated in drug addicts when shown drug stimuli. ̽��ֱ��ventral striatum is involved in processing reward and motivation, whilst the dorsal anterior cingulate is implicated in anticipating rewards and drug craving. ̽��ֱ��amygdala is involved in processing the significance of events and emotions.

̽��ֱ��researchers also asked the participants to rate the level of sexual desire that they felt whilst watching the videos, and how much they liked the videos. Drug addicts are thought to be driven to seek their drug because they want – rather than enjoy – it. This abnormal process is known as incentive motivation, a compelling theory in addiction disorders.

As anticipated, patients with compulsive sexual behaviour showed higher levels of desire towards the sexually explicit videos, but did not necessarily rate them higher on liking scores. In the patients, desire was also correlated with higher interactions between regions within the network identified – with greater cross-talk between the dorsal cingulate, ventral striatum and amygdala – for explicit compared to sports videos.

Dr Voon and colleagues also found a correlation between brain activity and age – the younger the patient, the greater the level of activity in the ventral striatum in response to pornography. Importantly, this association was strongest in individuals with compulsive sexual behaviour. ̽��ֱ��frontal control regions of the brain – essentially, the ‘brakes’ on our compulsivity – continue to develop into the mid-twenties and this imbalance may account for greater impulsivity and risk taking behaviours in younger people. ̽��ֱ��age-related findings in individuals with compulsive sexual behaviours suggest that the ventral striatum may be important in developmental aspects of compulsive sexual behaviours in a similar fashion as it is in drug addictions, although direct testing of this possibility is needed.

“There are clear differences in brain activity between patients who have compulsive sexual behaviour and healthy volunteers. These differences mirror those of drug addicts,” adds Dr Voon. “Whilst these findings are interesting, it’s important to note, however, that they could not be used to diagnose the condition. Nor does our research necessarily provide evidence that these individuals are addicted to porn – or that porn is inherently addictive. Much more research is required to understand this relationship between compulsive sexual behaviour and drug addiction.”

Dr John Williams, Head of Neuroscience and Mental Health at the Wellcome Trust, says: “Compulsive behaviours, including watching porn to excess, over-eating and gambling, are increasingly common. This study takes us a step further to finding out why we carry on repeating behaviours that we know are potentially damaging to us. Whether we are tackling sex addiction, substance abuse or eating disorders, knowing how best, and when, to intervene in order to break the cycle is an important goal of this research.”

Pornography triggers brain activity in people with compulsive sexual behaviour – known commonly as sex addiction – similar to that triggered by drugs in the brains of drug addicts, according to a ̽��ֱ�� of Cambridge study published in the journal PLOS ONE. However, the researchers caution that this does not necessarily mean that pornography itself is addictive.

There are clear differences in brain activity between patients who have compulsive sexual behaviour and healthy volunteers

Valerie Voon

Nick Olejniczak

Browsing (cropped). Homepage image: Ecstacy by Terminallychll

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Breaking sex education taboos in Africa to tackle AIDS

lw355 — Tue, 19 Jun 2012 13:59:40 +0000

In the absence of a cure or vaccine for HIV/AIDS, educating children about safe sex is regarded by many as the primary means for prevention – the United Nations and others have described it as “the social vaccine” – but the question of how best to do this has long been debated.

̽��ֱ��need for such efforts remains acute but is fraught with difficulty as deep-rooted socio-cultural, religious and moral constraints remain barriers to effective sex education across Africa and beyond.

Over a two-year period, a team of researchers from the ̽��ֱ�� of Cambridge’s Centre for Commonwealth Education, along with others in the UK and three countries in Africa, approached the problem by thinking beyond the classroom and asking a fundamental question: how much do children know already?

“We worked with children at grade 6 in primary school [median age 12] because this is the final year of compulsory education in the countries we were working in, Kenya, Tanzania and South Africa, and also because of a common perception that primary age is too young – that educating this age group is a risk rather than a protective factor,” said Dr Colleen McLaughlin, who leads the ASKAIDS project.

“Perhaps one of the more surprising findings was that their sexual knowledge was already wide-ranging.”

̽��ֱ��researchers used a technique called ‘photo-voice’, providing children with cameras to make a record of the people, places and things from which they learned about sex, love, AIDS and relationships – the resulting images are powerful and revealing (https://youtu.be/-837AuKdZwE).

“ ̽��ֱ��young people have a vigilant awareness of a highly sexual world around them, including prostitution, pornography and drug-related sex, and a fairly sophisticated knowledge of adults’ sexual practices,” said McLaughlin. “So much so, that it’s clear that children are at risk if treated as innocents in HIV/AIDS education.”

Asked to give their perceptions of current AIDS education classes and how they desired these classes to be, the children described how the curriculum centred on the giving of factual information – facts that they found difficult to connect to the confusing and mysterious world around them. Moreover, they felt that they couldn’t share their own knowledge with adults.

As one South African schoolboy from grade 6 put it: “ ̽��ֱ��teachers are careful with us because they think we are still young… They think we are going to be naughty or sometimes experiment what they told us... [but] who wants to experiment with AIDS?”

“When the teachers, parents and members of the community were presented with the findings, they were surprised and concerned at the extent of the young people’s knowledge,” explained researcher Dr Susan Kiragu.

“They thanked us for coming because it gave them a kind of ‘permission’ to talk about this sensitive, almost taboo, area, without feeling they were corrupting the children.”

̽��ֱ��project created what the researchers call a dialogic space; an opportunity for the children to ask questions based on what they already know, and for the teachers and the parents to respond openly and honestly.

“ ̽��ֱ��format we devised for the dialogues was engaging, interactive and rooted in the reality of the children’s experience – what is in fact simply a model of good sex education,” explained McLaughlin. “Because we want this to be a sustainable programme that will continue long after the duration of the project, we packaged the findings as a toolkit to support teachers through the process.”

In addition to in-depth interviews and focus-groups, conducted with children and adults separately, the researchers invited children to create their own mini-documentaries – involving group work and role-playing – to make up part of the toolkit. For example, in Kenya, the pupils portrayed moral stories about HIV/AIDS, such as pupils sneaking out of class to have sex, or a mother trying to influence her daughter to stop schooling and join her in prostitution.

“These role plays enabled pupils to voice their views, no matter how sensitive or incriminatory, in a de-personalised way,” said McLaughlin. “Overall, we found that children want a more interactive sexual education that allows them to engage with their own knowledge – and talk openly about their lack of knowledge.”

“They are concerned that the information they get is unrealistic and all too aware that it doesn’t reflect the world in which they live."

̽��ֱ��toolkit and a process for curriculum development is now being trialled in Botswana, Ghana, Kenya, South Africa, Swaziland and Tanzania. As the researchers gather the results of the trial over the next few months, the hope is that their innovative programme has offered the means to deliver the “social vaccine” by transcending cultural barriers to learning.

̽��ֱ��Centre for Commonwealth Education, Faculty of Education, is funded by the Commonwealth Education Trust.

Old Enough to Know: Consulting children about sex and AIDS education in three African countries, by Colleen McLaughlin, Sharlene Swartz, Susan Kiragu, Mussa Mohamed and Shelina Walli, is published by HSRC Press: Cape Town, South Africa.

New research focusing on educating young people about sex and HIV/AIDS in Africa is using innovative techniques – such as ‘photo-voice’ and role-play – to discover what African children know about sex and where they learn it from.

It’s clear that children are at risk if treated as innocents in HIV/AIDS education.

Dr Colleen McLaughlin

ASKAIDS Project

Centre for Commonwealth Education at the Faculty of Education

Photo-voice image from the AskAIDS project

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