Humans and prairie voles are among the 3-5% of mammals known to have monogamous relationships. Now, a study looking at prairie voles has found that when it comes to bonding, longing may be just as important as being together.
For the study, researchers at the University of Colorado Boulder used small cameras and technology known as in-vivo-calcium imaging to observe the brains of dozens of voles at three-time intervals. These were when they were meeting another vole, three days after they mated, and 20 days after they had practically ‘moved in’ together. They also observed how these voles interacted with others besides their partners.
Previous research has shown that when humans hold hands with a romantic partner as opposed to a stranger, their nucleus accumbens, the part of the brain for processing rewards, activates similarly to when using heroin or cocaine. To the researcher’s surprise, however, these findings were not present in voles. Whether with a stranger or a partner, the voles’ brains looked practically the same.
The researchers did nevertheless find differences in the voles’ brains while running to meet their partners. These differences were marked by the nucleus accumbens lighting up. They also found that the longer the voles had been together, the more this brain region would light up. Meanwhile, while approaching strangers, a completely different set of cells lit up.
The researchers suspect that chemicals such as oxytocin, dopamine, and vasopressin, all known for establishing closeness in animals and humans, are involved in this process. But how exactly they interact with the clusters of cells that lit up remains unknown.
Whether the same findings are present in humans also remains unknown until further research is conducted. The researchers nevertheless say that the study shows that monogamous animals are uniquely hardwired to be with one partner.