Ahead of Valentine's Day, research has suggested most of us seek out company, avoiding feeling lonely, because our brains are wired that way.
US and UK neuroscientists have located a neural circuit in the brains of mice that suggests social behaviours may be driven by a loneliness-like state.
"A neural substrate for a loneliness-like state has never been identified before," says senior study author Kay Tye of the Massachusetts Institute of Technology. "There have been a number of studies examining social reward, but none that have looked at the negative motivational drive to seek social contact."
The discovery came about mostly by accident while studying the effects cocaine has on DRN dopamine-releasing neurons in mice.
Researchers saw that the properties of these neurons changed when the mice were separated from other mice regardless of cocaine exposure.
To follow this up, researchers then monitored the DRN dopamine neurons on mice socially housed and isolated.
They found that releasing a young mouse into the cage of a mouse that had been isolated for 24 hours significantly increased the amount of DRN neuron activity.
Another experiment revealed these neurons also play a role in motivating social behaviour.
And the social rank of the mouse impacted the effect the neurons had on an individual.
"Dominant mice may experience a more pronounced loneliness-like state, increasing their drive to seek out social company after periods of isolation," researchers said.
The findings, published in journal Cell, could help our understanding of social anxiety and autism spectrum disorders.
"However, we cannot assume that mice experience loneliness in the same way that humans do."