The “Love Hormone" Drives Human Urge for Social Connection
Oxytocin activates reward circuitry and drives our need for a social network.
Christopher Bergland
In a breakthrough study from Stanford University School of Medicine, researchers have shown that oxytocin — known as the “lovehormone” because of its important role in the formation and maintenance of mother-child bonding and sexual attachments — is actually involved in a much broader range of social connections. The researchers discovered that oxytocin released through any type of social connectivity triggered the release of serotonin. In a chain reaction, the serotonin then activated the ‘reward circuitry’ of the nucleus accumbens resulting in a happy feeling.
This new discovery offers clues to ourevolutionary psychology… The titled, “Social Reward Requires Coordinated Activity of Nucleus Accumbens Oxytocin and Serotonin” appears in the September 12, 2013 issue ofNature.
For this study, Malenka and lead author GülDölen, MD, PhD, a postdoctoral scholar in his group with over 10 years of autism-research expertise, teamed up to untangle the complicated neurophysiological underpinnings of oxytocin's role in social interactions. They focused on biochemical events taking place in abrainregion called the nucleus accumbens, known for being central to our reward system.
The Stanford study suggests that one-on-onepair bondingprobably evolved from the human affinity for living collectively in a group. Many other studies have found thatsocial isolationis detrimental for our well-being. One of the problems of modern living in a Facebook age is that many of us feel isolated because our social networkexists in cyberspace which causes our biology to short-circuit.
As hunter-gatherers, early humans traveled in small bands and lived in groups. It is believed that group living preceded the emergence of living as a pair by about 35 million years. The new study suggests that oxytocin's role in one-on-one bonding probably evolved from an existing, broader affinity for group living.
Oxytocin and the Human Urge to Tend-and-Befriend
In the 1970s, biologists learned that in prairie voles, which mate for life, the nucleus accumbens is packed full of oxytocin receptors. Blocking oxytocin receptors disrupted the prairie voles' monogamous behavior. In species that are not biologically wired to be monogamous, such as mountain voles and common mice, the nucleus accumbens doesn’t have oxytocin receptors.
"From this observation sprang a dogma that pair bonding is a special type of social behavior tied to the presence of oxytocin receptors in the nucleus accumbens. But what's driving the more common group behaviors that all mammals engage in–cooperation,altruismor just playing around–remained mysterious, since these oxytocin receptors were supposedly absent in the nucleus accumbens of most social animals," said Dölen.
The new discovery shows that mice need to have oxytocin receptors at a very specific location in the nucleus accumbens and, importantly, that blocking oxytocin's activity there significantly diminished these animals'appetitefor any type of socializing. Dölen, Malenka and their Stanford colleagues have identified–for the first time–the specific nerve tract that secretes oxytocin in the region, and were able to pinpoint the effects of oxytocin release on other nerve tracts projecting to this area.
Malenka points out, “Mice can squeak, but they can't talk. You can't ask a mouse, 'Hey, did hanging out with your buddies a while ago make you happier?" So, to explore the social-interaction effects of oxytocin activity in the nucleus accumbens, the investigators used a standard measure called the conditioned place preference test.
"It's very simple," Malenka said. "You like to hang out in places where you had fun, and avoid places where you didn't. We give the mice a 'house' made of two rooms separated by a door they can walk through at any time. But first, we let them spend 24 hours in one room with their littermates, followed by 24 hours in the other room all by themselves. On the third day we put the two rooms together to make the house, give them complete freedom to go back and forth through the door and log the amount of time they spend in each room."
Like humans, mice prefer to spend time in a space that reminds them of having fun and feeling good. The companionship of other mice was key to making the mice feel good. But the urge to have a social connection with other mice vanished when oxytocin activity in their nucleus accumbens was blocked…
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Oxytocin Questions
Directions: Read the article and then answer the questions which follow
1)Why is Oxytocin also known as the “love hormone?”
2)What types of human interaction is oxytocin involved in?
3)Oxytocin makes animals more likely to form what type of bonds with partners?
4)In a 1-2 page 8-mark response answer the following question:
“What behavior is affected by Oxytocin?”