Males and females of many sexually reproducing species behave differently during mating or towards the young. Despite numerous documentation of sex differences in the brain at the cellular and molecular levels, how such sex differences relate to sexually dimorphic display of behaviors remain unclear.

In a recent study published in Nature Communications, Dr. XU Xiaohong's lab at  Institute of Neuroscience of the Chinese Academy of Sciences showed unexpectedly that a well-known sexually dimorphic brain nucleus can drive both male-typical and female-typical behaviors.

The medial preoptic area (mPOA) locates to the anterior tip of the hypothalamus at the base of the brain and is known to be larger in males than females in many species, including the human. The mPOA harbors sex-specific gene expression and connectivity patterns.

In this study, by recording neural activities of the mPOA, in particular mPOA neurons that express estrogen receptor a (Esr1), during male-typical mount and female-typical pup retrieval, the researchers first showed that mPOA neuronal activities strongly correlate with sexually dimorphic display of mount and pup retrieval.

They then revealed that optogenetic activation of the mPOA can drive both mount and pup retrieval at similar levels in male and female, indicating that the mPOA in both sexes contain neural substrates to activate these behaviors.

Ablation of mPOA Esr¹⁺ neurons essentially abolished sex differences in the display of mount and pup retrieval. Acute inhibition of activities of mPOA Esr¹⁺ neurons disrupts mount and pup retrieval.

These results suggested a fundamental bi-sexual layout of the brain for sex-specific behaviors where sexually dimorphic activation of neural circuits that exist in both sexes leads to sex biased display of behaviors.

This work was supported by grants from the National Nature Science Foundation of China, Ministry of Science and Technology office China 973 program, the Thousand Young Talents Program of China, the Strategic Priority Research Program of the Chinese Academy of Sciences, etc.