What if this instinct could be altered?

Scientists in Shanghai have figured out how to do just that. Experimenting on mice, a research team with the Institute of Neuroscience at the Chinese Academy of Sciences has identified neural circuitry that determines social hierarchical status. Their findings, published earlier this fall in the journal Science, detail how synapses in this circuitry can be manipulated to flip social standing.

Mice and humans share 99 percent of their genes, which makes the tiny rodent an optimal species in biomedical testing. They also share social behavioral tendencies. Like humans, mice organize themselves in hierarchies. A dominant mouse is able to gather more food than its more timid counterparts; it is also more gregarious when it comes to mating and marking territory.

Trying to interpret the meaning behind behaviors is challenging, according to Dr. Hu Hailan, who led the Shanghainese team. "The animals can't talk to you directly," she says by way of explanation. "So, experiments have to be very carefully designed to reduce ambiguity." Once they had identified the dominant-subordinate dynamics in their groups of mice, their attentions turned to the rodents' gray matter.

Social behavior and hierarchy are regulated in the brain's frontal lobe, in a small area known as the medial prefrontal cortex (mPFC). Using viruses, the scientists began to "tweak" synaptic strength between neurons in their subjects' mPFCs, transforming how the neurons communicated to each other. Dominant mice became more subservient, and subordinate mice whose synapses were strengthened began to act more like their alpha counterparts.

"The type of virus we used is transient," says Hu of the GluR4 gene, which caused subordinate mice to ascend the social ladder. (Another gene was used to propel dominant mice down to subservient level.) This transient quality is important: it allows for the change in the synapse to wear off naturally. "But there are other types that can have sustained expression [in the synapses]," Hu continues. "They probably will cause a more permanent change."

In stable hierarchies there tends to be less conflict because social status is relatively static. While the synaptic mechanism Hu's team discovered might have larger implications on group stability, this is something that hasn't been examined thoroughly. "[It's an] interesting thought," notes Hu. When it comes to practical applications, she explains, the research is basic. "I wouldn't predict medicines or therapies based on our study," she says. For now, her team's work is laying the groundwork for something far more holistic. "I hope our study will help [us] understand how social status influences different physiological functions, such as stress response, addiction and depression." she says.

Tech Bytes

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