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Scientists Look to Prairie Vole Brains to Understand Monogamy

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Neuroscientists studying prairie voles have identified circuits in the brain’s reward center that may be a key part of forming social connections. They published their study today in the journal Nature.

Monogamous relationships, or pair bonds, are a lot less common than you’d think, arising in fewer than 5 percent of mammal species, including us and prairie voles (Microtus ochrogaster). What makes us so dang determined to stick with just one other person (or vole)? And what prompts us to latch onto them in the first place?

It’s kind of hard to tell. Human pair bonding is notoriously difficult to study, says co-lead author Elizabeth Amadei of Emory University’s Silvio O. Conte Center for Oxytocin and Social Cognition. “As humans, we know the feelings we get when we view images of our romantic partners,” she said in a statement, "but, until now, we haven't known how the brain's reward system works to lead to those feelings and to the voles' pair bonding."

Scientists love prairie voles. They especially love prairie vole love—or at least the behaviors and brain chemistry that look like love to us. The voles are touchingly tender with one another, grooming, mating, and snuggling their partners until death does them part.

Previous studies have suggested that these intense connections may begin with hormones like oxytocin and dopamine swirling around the brain’s reward system. To learn more, the authors of the current study installed tiny probes in female prairie voles’ brains—the rodent neural version of a wiretap. They then paired the lady voles with males and left the couples alone to get to know each other a little better.

The neural wiretaps told a story of complex interactions between different regions of the female voles’ brains. As the ladies began to bond with their assigned dudes, a flurry of information was exchanged between their prefrontal cortices and nucleus accumbens, areas associated with decision-making and rewards, respectively.

The strength of these circuits varied by vole and seemed to influence her relationship. The stronger a vole’s connections were, the faster she started huddling with her partner. The reverse was also true: The more the two voles bonded, the stronger the neural connections became.

To further test their hypothesis, the researchers plopped lady voles down with new males, but only for a short period of time—not long enough to get attached and mate. During the voles’ brief date, the scientists sent a tiny pulse of light to the brain circuit in question, giving it a little boost. The next day, despite barely knowing the males they met the day prior, the light-pulsed ladies were significantly more likely to choose them over voles they’d never met. Just a little zap had been enough to kick off their courtship.

"It is amazing to think we could influence social bonding by stimulating this brain circuit with a remotely controlled light implanted into the brain," co-lead author Zack Johnson said in a statement.

Some caveats, of course: This study was on prairie voles, who are decidedly not people, and it only included female subjects. We couldn’t tell you what’s going on in those vole boys’ brains.

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Whale Sharks Can Live for More Than a Century, Study Finds
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Some whale sharks alive today have been swimming around since the Gilded Age. The animals—the largest fish in the ocean—can live as long as 130 years, according to a new study in the journal Marine and Freshwater Research. To give you an idea of how long that is, in 1888, Grover Cleveland was finishing up his first presidential term, Thomas Edison had just started selling his first light bulbs, and the U.S. only had 38 states.

To determine whale sharks' longevity, researchers from the Nova Southeastern University in Florida and the Maldives Whale Shark Research Program tracked male sharks around South Ari Atoll in the Maldives over the course of 10 years, calculating their sizes as they came back to the area over and over again. The scientists identified sharks that returned to the atoll every few years by their distinctive spot patterns, estimating their body lengths with lasers, tape, and visually to try to get the most accurate idea of their sizes.

Using these measurements and data on whale shark growth patterns, the researchers were able to determine that male whale sharks tend to reach maturity around 25 years old and live until they’re about 130 years old. During those decades, they reach an average length of 61.7 feet—about as long as a bowling lane.

While whale sharks are known as gentle giants, they’re difficult to study, and scientists still don’t know a ton about them. They’re considered endangered, making any information we can gather about them important. And this is the first time scientists have been able to accurately measure live, swimming whale sharks.

“Up to now, such aging and growth research has required obtaining vertebrae from dead whale sharks and counting growth rings, analogous to counting tree rings, to determine age,” first author Cameron Perry said in a press statement. ”Our work shows that we can obtain age and growth information without relying on dead sharks captured in fisheries. That is a big deal.”

Though whale sharks appear to be quite long-lived, their lifespan is short compared to the Greenland shark's—in 2016, researchers reported they may live for 400 years. 

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Scientists Find a Possible Link Between Beef Jerky and Mania
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Scientist have discovered a surprising new factor that may contribute to mania: meat sticks. As NBC News reports, processed meats containing nitrates, like jerky and some cold cuts, may provoke symptoms of mental illness.

For a new study, published in the journal Molecular Psychiatry, scientists surveyed roughly 1100 people with psychiatric disorders who were admitted into the Sheppard Pratt Health System in Baltimore between 2007 and 2017. They had initially set out to find whether there was any connection between certain infectious diseases and mania, a common symptom of bipolar disorder that can include racing thoughts, intense euphoria, and irritability.

While questioning participants about their diet, the researchers discovered that a significant number of them had eaten cured meats before their manic episodes. Patients who had recently consumed products like salami, jerky, and dried meat sticks were more likely to be hospitalized for mania than subjects in the control group.

The link can be narrowed down to nitrates, which are preservatives added to many types of cured meats. In a later part of the study, rats that were fed nitrate-free jerky acted less hyperactive than those who were given meat with nitrates.

Numerous studies have been published on the risks of consuming foods pumped full of nitrates: The ingredient can lead to the formation of carcinogens, and it can react in the gut in a way that promotes inflammation. It's possible that inflammation from nitrates can trigger mania in people who are already susceptible to it, but scientists aren't sure how this process might work. More research still needs to be done on the relationship between gut health and mental health before people with psychiatric disorders are told to avoid beef jerky altogether.

[h/t NBC News]

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