New research from the Autism Research Centre at the University of Cambridge reveals that sex differences in brain structures are present from birth. The study, the largest of its kind, sheds light on the foundational biological distinctions between male and female brains.
New research from the Autism Research Centre at the University of Cambridge, published in the journal Biology of Sex Differences, has revealed that sex differences in brain structures are evident from birth. The study, which analyzed data from over 500 newborns, is the largest of its kind to date.
The researchers found that, while male brains generally have a greater overall volume than female brains, female infants tend to have significantly more grey matter when adjusted for total brain volume. In contrast, male infants possess more white matter on average.
Grey matter is primarily composed of neuron cell bodies and dendrites, which are crucial for interpreting information related to sensation, perception, learning, speech, and cognition. White matter, consisting of axons, facilitates communication between different regions of the brain.
“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,” lead author Yumnah Khan, a doctoral student at the Autism Research Centre, said in a news release. “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.”
A key challenge in research on brain differences has been the issue of sample size. The Cambridge team overcame this by analyzing data from the Developing Human Connectome Project, which provided MRI scans of newborns shortly after birth. This large sample size enabled the detection of meaningful sex differences.
Additionally, the researchers controlled for other factors, such as variations in body size and birth weight, to ensure the differences observed were specific to brain structures. The study concludes that female infants typically have larger grey matter volumes in areas related to memory and emotional regulation, whereas male infants show larger grey matter volumes in regions involved in sensory processing and motor control.
“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,” co-author Alex Tsompanidis, a postdoctoral research associate at the Autism Research Centre who supervised the study, said in the news release.
He emphasized the importance of understanding the underlying causes of these differences by investigating prenatal conditions using population birth records and in vitro cellular models.
These average differences do not imply superiority of one sex over the other, a point stressed by the researchers.
“These differences do not imply the brains of males and females are better or worse. It’s just one example of neurodiversity,” added co-author Simon Baron-Cohen, the director of the Autism Research Centre. “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.”
The researchers are now looking into whether biological factors such as hormones or the placenta during prenatal development contribute to these observed differences, which could have far-reaching implications for understanding sex-specific brain development and neurodiversity.