Previous research with captive male prairie voles, which form lifelong bonds with a single partner, indicated that the animals had high levels of vasopressin receptors in the ventral pallidum, a brain region closely associated with the reward system. In contrast, captive male meadow voles, which often take multiple partners throughout their lives, lacked vasopressin receptors. In the new work, Miranda M. Lim of Emory University and her colleagues inserted a gene that encodes for the vasopressin receptor protein directly into the brains of male meadow voles. The researchers then observed the animals' behavior as they were introduced to a variety of potential partners. They found that meadow voles treated with gene therapy acted more like their prairie vole counterparts--they spent more time huddling near their original companion. According to study co-author Larry J. Young of Emory University, the results provide evidence in a comparatively simple animal model that changes in the activity of a single gene profoundly can change a fundamental social behavior of animals within a species.
Of course, it's a big step from voles to people, but the researchers hope the results will contribute to a better understanding of how human attachments form. Such knowledge could inform treatment options for disorders such as autism, which disrupt a person's ability to form social bonds. It is intriguing, says Young, to consider that individual differences in vasopressin reception in humans might play a role in how differently people form relationships.