Scientists discover how orgasms rewire the brain and lead to lasting connection between partners

They say sex is the key to a happy marriage - and now science suggests it's true.

Orgasms rewire the brain in ways that encourage long-term bonding, according to new research.

A team of researchers at The University of Texas at Austin and Cold Spring Harbor Laboratory mapped the brains of male and female voles during their three stages of courtship: mating, bonding, and 'ongoing bond maintenance.'

They found that during these stages, 68 different regions of the brain underwent significant changes, rewiring and forming new connections.

Both members of a pair displayed similar brain changes, and the biggest changes seem to occur when the male has an orgasm.

This could mean that orgasms promote connection beyond just sex, something scientists think is true for people, too. 

Experiences change the brain, creating new connections between neurons and pruning old ones. Scientists use the vole as a model for examining the neuroscience of sex and love because it forms lifelong bonds.

Sex may be more than just a perk in long-term relationships. New research on voles suggests that sex is an important part of re-shaping the brain to support a lasting connection.

These changes could reflect evolutionary adaptations that increase the odds of survival, as a bonded pair will stand better odds of successfully raising their shared babies. 

'The brain and behavior data suggest that both sexes may be having orgasm-like responses, and these 'orgasms' coordinate the formation of a bond,' said study author Steven Phelps, professor of integrative biology at UT Austin, in a statement.

 'If true, it would imply that orgasms can serve as a means to promote connection, as has long been suggested in humans.'

Researcher saw that the most significant predictor of these changes was male orgasm, which seemed to affect the brain changes in both males and females.

In other words, the more the male orgasmed, the more profound their and their partner's brain rewiring was. They could not tell when or whether the females orgasmed.

Prairie voles form lifelong bonds. A bonded pair will comfort one another when stressed, defend their shared territory, and raise young together.

The study used prairie voles, a type of rodent species that has become an unlikely scientific window into how the brain handles sex and love.

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These small, North American animals form lifelong pairs, so scientists use them to study the neuroscience and behavior of monogamy. 

Of course, not all humans are monogamous.

But studies have shown that both prairie voles and humans express oxytocin, which has been dubbed 'the love hormone' for its role in bonding, both between romantic pairs and between mother and child.

In the new study, scientists started with voles that had never mated, to ensure that their brains were blank slates, sexually speaking. 

The team used wild-caught voles, a strategy that more labs are adopting in recent years, which may help avoid some of the reproducibility problems involved with inbred lab animals.

After giving female voles a hormone injection to ensure they were in heat, scientists paired them up with males. 

About 200 voles were paired up, and scientists observed their behavior carefully, recording everything the animals did, including mating, grooming, and even orgasming.

When the animals were around 10 weeks old, they were euthanized, and the researchers preserved their brains.

They mapped all the connections in them, and then did statistical analysis to link their behaviors to what they observed in the brains.

Past research has suggested that sex hormones like estrogen and testosterone, which are not the same between males and females, play important roles in bonding and sex.

But there was no significant difference between males' and females' brains, the researchers reported.

Scientists used light-sheet fluorescence microscopy (LSFM) imaging to examine vole brains after forming pair bonds. They found many areas were involved, areas not previously known to be associated with sex and bonding.

'That was a surprise,' Phelps said.

'Sex hormones like testosterone, estrogen and progesterone are important for sexual, aggressive and parental behaviors, so the prevailing hypothesis was that brain activity during mating and bonding would also be different between the sexes.' 

What they did find was that many areas that changed during bonding were not previously known to be linked to bonding. 

In fact, they identified 68 regions of the brain that had formed new connections during the pair's bonding process.

The study was published in the journal eLife.

Voles are known to form pair bonds quickly, going from strangers to partners in the span of a day.

And sex is a crucial part of this bonding process, the researchers found.

Often within the first 30 minutes of meeting, a male and female vole will begin having sex, and they will continue to do so repeatedly.

During this time, they form a bond that often lasts a lifetime.

A bonded pair of voles will groom one another, raise young together, comfort each other when stressed, and defend their shared territory and young.