Sex and gender are often conflated or equated in everyday conversations, and most American adults believe that a person’s gender is determined by the gender assigned at birth. But a new study of nearly 5,000 9- and 10-year-olds found that sex and gender are mapped to separate parts of the brain.
The research provides the first insight into how sex and gender may have “measurable and unique effects” on the brain, the study authors said, just as other brain-shaping experiences have shown.
“Moving forward, we need to consider gender and gender separately if we want to better understand the brain,” said Dr. Elvisha Dhamala, assistant professor of psychiatry at the Feinstein Institutes for Medical Research and Zucker Hillside Hospital in Glen Oaks. , California, and co-author of the study, published Friday in the journal Science Advances.
The researchers of the new study defined sex as what the child was assigned at birth. In the United States, clinicians perform this assignment based on the genitalia. Most people are assigned female or male, according to the research; the rest are intersex, someone whose sexual or reproductive anatomy does not fit this male/female binary.
The researchers defined gender as a person’s attitudes, feelings and behaviour, as well as socially constructed roles. They specifically noted that gender is not binary, meaning that not everyone identifies as female or male.
Sex and gender are an integral part of the human experience. They are crucial to how people perceive others and how they understand themselves. Both can influence behavior as well as health, say the study authors.
The researchers looked at brain imaging data from 4,757 children in the United States, 2,315 assigned female at birth and 2,442 assigned male at birth, who were 9 and 10 years old and were a subset of the Cognitive Brain Development study Adolescents (ABCD), the largest. a long-term study of brain development and child health in the United States. Over a 10-year period, the children in the ABCD study underwent comprehensive neuroimaging, behavioral, developmental and psychiatric assessments.
As well as tests such as MRI, the scientists conducted gender-specific surveys of the children and their parents, at the start of the research and then a year later. The children were asked about how they expressed their gender and how they felt about it. Parents were asked about a child’s sex-typed behavior during play and whether the child had any gender dysphoria, a term used by mental health professionals to describe clinically significant distress experienced because a person’s perception of their gender does not match their gender assigned at birth.
Parents were an integral part of the study, said study co-author Dr. Dani S. Bassett, a professor at the University of Pennsylvania with appointments in the Departments of Bioengineering, Electrical & Systems Engineering, Physics & Astronomy, Neurology, and Psychiatry.
“When children have a certain type of gender behavior or gender expression, that will affect how their parents and other caregivers and their friends and family … et cetera interact with them,” Bassett said. Information about a parent’s perception of a child’s gender gives researchers a better understanding of the child’s social environment and how it may affect their brain development.
The authors used a type of artificial intelligence called machine learning that built a model that could predict a child’s sex and reported gender from their brain scans. When the researchers looked at the children’s brain scans, the results seemed to show that sex affected different regions of the brain involved in visual processing, sensory processing and motor control and some regions involved with executive function, which allows an individual to organize and integrate information. over time.
Gender appears to affect some of the sex-specific sensory networks, but it also appears to have a broader effect and can be detected in different brain networks involved in executive function, including -includes things like attention, social cognition and emotional processing. .
“The fact that we can basically capture how gender maps on the brain tells us that gender affects our brain,” said Dhamala.
The structure of the human brain can be shaped by expertise and experiences. Research into London taxi drivers – who must undergo extensive tests to show they can navigate the city’s streets without maps or GPS – appears to show that they have significantly larger posterior hippocampi, the part of the brain associated with spatial memory and navigation, than in non-taxi drivers.
“Also, as individuals and as people, we are experts about ourselves and our gender. So it makes sense that gender is also mapped within our brains,” said Dhamala.
What the new study can’t do is predict what gender a person might identify with beyond a single, limited snapshot in time of the scans and surveys. Gender is not necessarily static, according to the authors, and a person’s understanding of their gender can change throughout their life.
The study also cannot determine what things in a person’s environment will influence their brain function in terms of sex or gender, nor can it identify what a person’s sexual orientation is.
“Sexual orientation is independent of gender and sex,” Bassett said, and may be mapped differently in the brain.
The researchers say they hope to someday learn more about how sex and gender interact in a person’s life and how they affect each other and the brain throughout life. They also hope to see how different cultures affect a person’s gender and brain development.
A 2022 poll showed that most American adults — and the vast majority of conservatives — believe that a person’s gender is determined by the gender assigned at birth. The distinction is critical to gender affirming care, the medical treatment of people who identify as a gender different from the one they were assigned at birth. Conservative politicians are pushing for a record number of bans on such care, and nearly half of US states have enacted bans on gender affirming care for minors.
The study did not look at whether sex or gender was congruent or incongruent in any study participant. Rather, it looked at the child’s sex and gender binary across self-report and parent measures. The study could not provide any specific results if the sex and gender were inconsistent.
“In the future, we hope to be able to encourage other scientists to consider science and gender in their analyzes of data collections in their programs and research,” said study co-author Dr. Avram Holmes, associate professor of psychiatry at Rutgers University. .
The field of neuroscience is just beginning to recognize and address the presence of biases and barriers to inclusiveness within research, Holmes said.
A more complete understanding of how the brain works in terms of sex and gender could have practical implications and could help scientists find better ways to treat people with brain-related illnesses to treat. For example, the study revealed how people assigned male at birth are more likely to be diagnosed with substance use and attention deficit disorders.
“Illness rates are not necessarily driven by sex and gender, but the cultures people are immersed in can also influence the likelihood of developing or not developing a particular illness,” Holmes said. “So the kinds of environmental pressures a child experiences across development may increase or decrease their risk of illness, independent of their initial brain biology.”
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