As a species, voles have almost perfected monogamy – so scientists have turned to the tiny mammals to study the neuroscience of love

“Love looks not with the eyes, but with the mind. And therefore is winged Cupid painted blind,” Shakespeare wrote. Now scientists have pinpointed the specific patterns of brain activity that accompany romance, offering a new explanation for why love sends our judgement haywire.



As a relationship takes root, the study found, the brain’s reward circuit goes into overdrive, rapidly increasing the value placed on spending time with one’s love interest. This, at least, was the case in the prairie vole, scientists’ animal model of choice for studying the neuroscience of love.

Elizabeth Amadei, who co-led the work at Emory University in Atlanta, said: “As humans, we know the feelings we get when we view images of our romantic partners, but, until now, we haven’t known how the brain’s reward system works to lead to those feelings.”

In order to get more direct access to what is happening in the brain, Amadei and colleagues turned to the North American voles, which as a species have almost perfected monogamy. They mate for life, share nest-building duties and have an equal role in raising their young – although, like humans, voles have the occasional “extramarital” fling.

Using electrical probes, the scientists recorded directly from the brains of female voles as they encountered a potential partner, mated for the first time and began to show signs of having formed a lifelong bond, indicated by “huddling” behaviour.

Robert Liu, co-lead author also at Emory University, said: “It’s kind of like human cuddling: they like to sit side by side and veg out.”



The electrodes recorded peaks in activity in two brain areas known to be linked to the formation of a pair bond – the medial prefrontal cortex, which is involved in executive control, and the nucleus accumbens, the central hub of the brain’s reward system.

The team found that the baseline level of communication between the two regions predicted how likely a female was to form a bond, which Liu describes as “an individual predisposition to being affectionate”.

They also tracked changes in activity as animals socialised and mated (“kind of like watching vole porn,” according to Liu).

The first time the animals mated, the activity in the circuit changed, and how much stronger the activity got was predictive of how quickly the animals would start huddling.

“We think the circuit is involved in switching behaviours,” said Liu. “It maybe biases how you then feel toward that individual.”

As proof of this, the team used a technique called optogenetics that allowed them to artificially switch on the neural circuit by shining light directly onto the surface of the brain. They stimulated the circuit whilst a female spent time near a male, but without direct contact as the male was under a transparent cup. Later, the female vole acted as though they had already formed a bond, showing preference for this vole over strangers when given a choice the following day.

“The idea of a spark between individuals has been suggested,” said Liu. “I’m not sure that’s the right term here. It doesn’t just happen once, it’s probably building up over time.”

In future, the findings might shed light on disorders such as autism, in which social bonding can be impaired. The study is published in the journal Nature.