����������ý�Ļ���Ʒ

In CUriosity, experts across the ����������ý�Ļ���Ʒ campus answer pressing questions about humans, our planet and the universe beyond.

This week, Zoe Donaldson, a professor in the departments of Molecular, Cellular, and Developmental Biology and Psychology and Neuroscience, answers: "What is Love?"

For centuries, romantics have turned to musicians, artists, writers and philosophers in their quest to define one of humankind’s most complex, and arguably critical, emotions.

Neuroscientist Zoe Donaldson takes a different approach. She looks to fuzzy, palm-sized rodents called prairie voles.

“From a neuroscientific perspective, love is the biological drive that allows us to form relationships,” she explains, as a family of four hungry newborn voles chase their mom around a glass enclosure in her office, their dad looking on.

The scene unfolding behind her says a lot about the evolutionary utility of love, she explains: It enables babies to bond with mothers who provide them with food and siblings who protect them and keep them warm. For some, it ultimately leads them to a mate, with which they reproduce, perpetuating the species.��

“The vast majority of rodents out there mate and leave. But these guys are different,” she says.

Like humans, and only about 5% of all mammal species, prairie voles can form long-term bonds with a partner, staying together to build a home and raise offspring. They also experience something akin to longing when separated from their partner and grief when their partner dies. This makes them ideal for studying the neurochemical glue that bonds are made of, she says.

Three brain chemicals play a starring role in this love story: Dopamine, oxytocin and vasopressin.

Dopamine, the same brain chemical at the root of dependency to cocaine, heroin, alcohol and other drugs of addiction, appears to draw us in and keep us coming back.��

“There’s essentially more dopamine being released in the brain when an animal is engaging in an effort that will gain them access to their partner,” Donaldson says, noting that when a prairie vole presses a lever that opens a door leading to their partner, their tiny brain is awash with the endogenous love drug. “We think of this as a chemical signature of desire within the brain.”

(Importantly, she adds, dopamine is designed to do this to help us execute our daily lives, unlike when it is hijacked by drugs of abuse.)

��

����Previously in CUriosity

What is the smallest thing in the universe?

Or read more CUriosity stories here

Oxytocin is probably best known for its not-particularly-romantic role as the drug given to laboring women to induce contractions. But it also nudges the maternal brain to want to take care of a newborn and stimulates milk production when an infant suckles. In prairie voles (and likely in people), the brain produces oxytocin when lovers couple up for the first time.

Vasopressin, the yang to Oxytocin’s yin, is a particularly important ingredient for helping males to form a bond, says Donaldson. It makes blood pressure rise and warms up the body, pleasant sensations worth coming back for. It can also make males a bit more aggressive, which comes in handy when (at least in the wild) males need to defend their territory.

"Each of these molecules is evolutionarily ancient,” says Donaldson. “We find them in worms and snails, where they are also important for motivation and social interaction.”

By studying these and other brain chemicals, Donaldson hopes to better understand not only what brings people together but also: What prevents some people from being able to form such bonds? Or renders others unable to bounce back, and reengage with life, when they lose a loved one (a disorder known as prolonged grief disorder)?

But is love just a collection of brain chemicals?

Donaldson gets that question a lot and doesn’t love the way it’s phrased.

“Adding ‘just’ into the question diminishes the fact that your brain chemistry is ultimately the seat of love,” she says. “We are beginning to learn that love is not something you have to learn, but something that is literally hard-wired into our brain from the moment we are born.”

You can’t get much more romantic than that.