Next time you’re feeling lonely, take comfort that it’s not just because you’re listening to too much Drake — it actually is all in your head. For the first time, scientists have connected the feeling of loneliness to a cellular substrate.

A team of neuroscientists from the Massachusetts Institute of Technology have identified a cluster of cells located in the the dorsal raphe nucleus (DRN), a region near the back of the brain that researchers previously suspected was linked to depression. They found that these cells are responsible for stoking the desire for sociability after periods of isolation, a discovery that fellow neurobiologists at UCLA are calling “an amazing cornerstone for future studies of loneliness.”

So far, research has focused on only the behavior of mice (which comes with the usual caveats. Mice who were housed together had inactive DRN neurons. But when a mouse was isolated for one day and then reunited with its buddies, DRN activity surged. When the researchers suppressed the isolated mouse’s DRN neurons with optogenetics, they found that the rodents were far less sociable when they came back into the group.

“We think that this adaptive and evolutionarily conserved trait is what we are modeling in mice, and these neurons could play a role in that increased motivation to socialize,” says study co-author Kay Tye in a press release.

Lead study author Gillian Matthews told Wired that the DRN activation is certainly a “useful, adaptive response,” but they have yet to pinpoint what neural mechanisms are underlying the reaction. The neurobiologists hypothesize that innate brain features could be the cause, but it’s also possible the environment where the individual lives fires up the response. A dominant mouse will be happy in its social group; a bullied mouse won’t be.

The next step is to explore whether neurons simply detect loneliness, or the stimulation of them, in fact, causes the feelings of loneliness. Either way, this research further proves that contact with others provides the basic but necessary evolutionary advantage of making us happy.

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