A different take on differences between men's and women's brains

June 28, 2017, Leiden University
brain
Credit: public domain

There is greater variety in the size of men's brains than of women's. This could help explain why some psychiatric disorders such as ADHD and autism are more prevalent in boys. Leiden brain researcher Lara Wierenga has published an article about this in the international journal Cerebral Cortex.

Brain researcher Lara Wierenga studied 1234 children and young adults aged between three and 21 from a large MRI database at the University of California, San Diego. She compared the variation in in men with the variation in brain volume in women. What she found was that there was greater variation in brain volume in men than in women, so there are more boys than girls with exceptionally large or exceptionally small brain structures. These findings may explain why some developmental disorders such as ADHD or autism are more prevalent in boys than in girls.

Genetic difference

Prior studies of children's have found greater variation in boys than in girls. Wierenga: "I wanted to research whether we also see these in the brain and how they are given shape in the brain. I also wanted to know if the differences in variation between boys and girls were already present at an early stage or whether they develop over time. The former proved to be the case: differences in brain variation are already apparent at the age of three and remain stable as children become older. This suggests a genetic effect in the brain. The relationship with school performance was not investigated in this study. We suspect that environmental factors increase the differences between boys and in variation in school performance."

Possible explanation

Wierenga says that a possible explanation for the difference could be that men have only one X chromosome. "If this X chromosome contains a gene that is related to a smaller brain structure, you will therefore see this in all brain structures in men. Women's two X mean a tendency towards the average. As a different X chromosome is active in one brain cell than the other, the extremes balance each other out."

The results indicate that typical 'male' may be linked to the greater variation in brain volume in men and the single X chromosome. This may provide new insights into ADHD and autism. Incidentally, it is not the case that all men and all women differ from each other, nor is it the case that there are no outliers among women. Furthermore, there are no differences between the structure of most men and women. However, the number of men at either extreme is greater and thus more apparent.

"This study shows that you can test genetic models by comparing differences between men and differences between women," Wierenga continues. "Many other studies look at average differences between the groups, so between all men and all women. In small studies in particular you run the risk of finding average differences between men and that you would not find if you took a larger sample."

Explore further: Mounting challenge to brain sex differences

More information: Lara M. Wierenga et al. A Key Characteristic of Sex Differences in the Developing Brain: Greater Variability in Brain Structure of Boys than Girls, Cerebral Cortex (2017). DOI: 10.1093/cercor/bhx154

Related Stories

Mounting challenge to brain sex differences

January 17, 2017
How different are men and women's brains? The latest evidence to address this controversy comes from a study at Rosalind Franklin University of Medicine and Science, where a meta-analysis of human amygdala volumes found no ...

Why teen mental ability surges while brain shrinks

June 6, 2017
(HealthDay)—Scientists say they have an answer to a persistent and quirky puzzle about brain development.

Genes influence ability to read a person's mind from their eyes

June 7, 2017
Our DNA influences our ability to read a person's thoughts and emotions from looking at their eyes, suggests a new study published in the journal Molecular Psychiatry.

Brain anatomy differs in people with 22q genetic risk for schizophrenia, autism

May 24, 2017
A UCLA study characterizes, for the first time, brain differences between people with a specific genetic risk for schizophrenia and those at risk for autism, and the findings could help explain the biological underpinnings ...

ADHD a 'brain disorder', not just bad behaviour: study

February 16, 2017
People with ADHD have slightly smaller brains than those without the condition, according to a study released Thursday which insisted it is a physical disorder and not just bad behaviour.

ADHD may have different effects on brains of boys and girls

October 22, 2015
(HealthDay)—Attention-deficit/hyperactivity disorder (ADHD) manifests itself differently in the brains of girls than in the brains of boys, new research suggests.

Recommended for you

Research shows signalling mechanism in the brain shapes social aggression

October 19, 2018
Duke-NUS researchers have discovered that a growth factor protein, called brain-derived neurotrophic factor (BDNF), and its receptor, tropomyosin receptor kinase B (TrkB) affects social dominance in mice. The research has ...

Good spatial memory? You're likely to be good at identifying smells too

October 19, 2018
People who have better spatial memory are also better at identifying odors, according to a study published this week in Nature Communications. The study builds on a recent theory that the main reason that a sense of smell ...

How clutch molecules enable neuron migration

October 19, 2018
The brain can discriminate over 1 trillion odors. Once entering the nose, odor-related molecules activate olfactory neurons. Neuron signals first accumulate at the olfactory bulb before being passed on to activate the appropriate ...

Scientists discover the region of the brain that registers excitement over a preferred food option

October 19, 2018
At holiday buffets and potlucks, people make quick calculations about which dishes to try and how much to take of each. Johns Hopkins University neuroscientists have found a brain region that appears to be strongly connected ...

Gene plays critical role in noise-induced deafness

October 19, 2018
In experiments using mice, a team of UC San Francisco researchers has discovered a gene that plays an essential role in noise-induced deafness. Remarkably, by administering an experimental chemical—identified in a separate ...

Brain cells called astrocytes have unexpected role in brain 'plasticity'

October 18, 2018
When we're born, our brains have a great deal of flexibility. Having this flexibility to grow and change gives the immature brain the ability to adapt to new experiences and organize its interconnecting web of neural circuits. ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.