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NIH Record - National Institutes of Health

NIH-Funded Study Reveals How Differences in Male, Female Brains Emerge

Two worms next to each other

Male and female worms engage in different behaviors, which may result from sex-specific wiring patterns in the brain.


Nematode worms may not be from Mars or Venus, but they do have sex-specific circuits in their brains that cause the males and females to act differently. According to new research published in Nature, scientists have determined how these sexually dimorphic (occurring in either males or females) connections arise in the worm nervous system. The research was funded by NINDS. 

“For decades, there has been little focus on the impact of sex on many areas of biomedical research,” said Dr. Coryse St. Hillaire-Clarke, program officer on this NINDS project. “This study helps us understand how sex can influence brain connectivity.”

In nematode worms (known as Caenorhabditis elegans or C. elegans), a small number of neurons are found exclusively in male or female brains. The remaining neurons are found in both sexes, although their connection patterns are different in male and female brains. Dr. Oliver Hobert, professor of biological sciences at Columbia University, and his colleagues looked at how these wiring patterns form.

Hobert’s team observed that in the worms’ juvenile state, before they reach sexual maturity, their brain connections were in a hybrid, or mixed state, consisting of both male and female arrangements. As they reached sexual maturity, however, their brains underwent a pruning process, which got rid of particular connections and led to either male or female patterns.

“We found that differences in male and female brains develop from a ground state, which contains features of both sexes. From this developmental state, distinctly male or female features eventually emerge,” said Hobert.

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