ohOur brains are shaped by our experiences — whether we’re a birdwatcher, a book lover, or a chess player — and new research is also giving us a clearer view of how sex and gender affect the brain.
Using artificial intelligence to analyze MRI scans from thousands of children, the researchers found that by looking at how brain regions interact, they could predict a subject’s sex or gender, albeit imperfectly. Notably, the connectivity patterns that predicted sex, which is primarily determined by biology, were not the same as those that predicted gender, which is defined by a person’s sense of identity.
The authors found that gender-related brain networks were more likely to involve brain regions involved in vision, sensory processing, motor control, planning and decision-making. In comparison, gender-related networks were less strongly connected to specific brain regions.
the study, Published The study, published Friday in Science Advances, leaves many questions unanswered, including how the brain connections differ in sex- and gender-nonconforming children, when these network differences arise, and how they change over time. But the authors stress that the findings underscore the importance of collecting data on both sex and gender, even though this is not standard practice in neurological studies.
“Going forward, if we want to better understand the brain, we need to consider sex and gender separately,” said Elvisha Damala, lead author of the study. “Beyond the scope of this study itself, the future of biomedical research depends on considering sex and gender separately.”
The terms sex and gender are often used interchangeably in everyday life, but to researchers they have distinct meanings: sex is a biological variable, shaped by hormones, anatomy, and genetics, while gender is a cultural concept, shaped by our sense of self and our interactions with others.
Researchers have long known that brain diseases such as Alzheimer’s disease and attention-deficit hyperactivity disorder vary in diagnosis and incidence by sex and gender, but determining the extent to which each factor contributes to these disparities has been difficult because, although data on sex is more routinely collected in biological studies since a 2015 National Institutes of Health mandate, sex is often not included as a separate category.
In a recent study, researchers analyzed data from the Adolescent Cognitive Brain Study, the largest longitudinal study of child brain development in the United States. They looked at functional MRI (fMRI) data from 4,757 participants, ages 9 to 10, roughly split between the sexes. The researchers also obtained gender data for all participants, based on self-report or parent responses.
fMRI measures brain activity by tracking blood flow and electrical activity, allowing researchers to understand which regions communicate with each other. The team then used machine learning algorithms to predict a person’s gender based on brain connectivity patterns.
The authors first found brain network patterns that could predict sex and gender. However, it was not clear from their analysis whether sex affects the brain beyond the influence of a person’s sex. To explore that question, the authors analyzed the data for men and women separately to isolate the effects of sex. They found that the network patterns associated with sex were different from those associated with sex, whether they looked at parent-reported or child-reported sex. The research team argued that this finding means that sex and gender do not affect the brain in the same way.
But Daniel Bayless, a neurobiologist at the Salk Institute who was not involved in the study, said the authors’ data don’t fully support that claim.
Bayless praised the study for incorporating gender, but noted that when the researchers built a gender predictive model using results from both men and women, they found that the gender- and sex-related connections largely overlapped.
They also noted that the study did not separately analyze data from children whose sex assigned at birth differed from their gender identity, a point the authors acknowledged in a press conference, explaining that the study considered gender as a continuum rather than a distinct category.
Although the study focused on sex and gender, these factors only explain about half of the variation in brain network patterns seen across participants, meaning there are other important factors as well. The paper also only looked at participants at one point in time; the researchers now plan to follow individuals and examine how these patterns change across adolescence and adulthood.
