Scientists Look to Prairie Vole Brains to Understand Monogamy

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iStock

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.

Does Sound Travel Faster or Slower in Space?

iStock/BlackJack3D
iStock/BlackJack3D

Viktor T. Toth:

It is often said that sound doesn’t travel in space. And it is true … in empty space. Sound is pressure waves, that is, propagating changes in pressure. In the absence of pressure, there can be no pressure waves, so there is no sound.

But space is is not completely empty and not completely devoid of pressure. Hence, it carries sound. But not in a manner that would match our everyday experience.

For instance, if you were to put a speaker in interstellar space, its membrane may be moving back and forth, but it would be exceedingly rare for it to hit even a single atom or molecule. Hence, it would fail to transfer any noticeable sound energy to the thin interstellar medium. Even the somewhat denser interplanetary medium is too rarefied for sound to transfer efficiently from human scale objects; this is why astronauts cannot yell to each other during spacewalks. And just as it is impossible to transfer normal sound energy to this medium, it will also not transmit it efficiently, since its atoms and molecules are too far apart, and they just don’t bounce into each other that often. Any “normal” sound is attenuated to nothingness.

However, if you were to make your speaker a million times bigger, and let its membrane move a million times more slowly, it would be able to transfer sound energy more efficiently even to that thin medium. And that energy would propagate in the form of (tiny) changes in the (already very tiny) pressure of the interstellar medium, i.e., it would be sound.

So yes, sound can travel in the intergalactic, interstellar, interplanetary medium, and very, very low frequency sound (many octaves below anything you could possibly hear) plays an important role in the formation of structures (galaxies, solar systems). In fact, this is the mechanism through which a contracting cloud of gas can shed its excess kinetic energy and turn into something compact, such as a star.

How fast do such sounds travel, you ask? Why, there is no set speed. The general rule is that for a so-called perfect fluid (a medium that is characterized by its density and pressure, but has no viscosity or stresses) the square of the speed of sound is the ratio of the medium’s pressure to its energy density. The speed of sound, therefore, can be anything between 0 (for a pressureless medium, which does not carry sound) to the speed of light divided by the square root of three (for a very hot, so-called ultrarelativistic gas).

This post originally appeared on Quora. Click here to view.

How Fossil Fuel Use Is Making Carbon Dating Less Accurate

iStock.com/Harry Wedzinga
iStock.com/Harry Wedzinga

The scientific process of carbon dating has been used to determine the age of Ötzi the Iceman, seeds found in King Tutankhamun’s tomb, and many other archaeological finds under 60,000 years old. However, as SciShow points out in a recent episode, the excessive use of fossil fuels is making that method less reliable.

Carbon dating, also called radiocarbon or C-14 dating, involves analyzing the ratio of two isotopes of carbon: C-14 (a radioactive form of carbon that decays over time) and C-12 (a more stable form). By analyzing that ratio in a given object compared to a living organism, archaeologists, paleontologists, and other scientists can get a pretty clear idea of how old that first object is. However, as more and more fossil fuels are burned, more carbon dioxide is released into the environment. In turn, this releases more of another isotope, called C-12, which changes the ratio of carbon isotopes in the atmosphere and skews the carbon dating analysis. This phenomenon is called the Suess effect, and it’s been well-documented since the ‘70s. SciShow notes that the atmospheric carbon ratio has changed in the past, but it wasn’t anything drastic.

A recent study published in Nature Communications demonstrates the concept. Writing in The Conversation, the study authors suggest that volcanoes “can lie about their age." Ancient volcanic eruptions can be dated by comparing the “wiggly trace” of C-14 found in trees killed in the eruption to the reference "wiggle" of C-14 in the atmosphere. (This process is actually called wiggle-match dating.) But this method “is not valid if carbon dioxide gas from the volcano is affecting a tree’s version of the wiggle,” researchers write.

According to another paper cited by SciShow, we're adding so much C-12 to the atmosphere at the current rate of fossil fuel usage that by 2050 brand-new materials will seem like they're 1000 years old. Some scientists have suggested that levels of C-13 (a more stable isotope) be taken into account while doing carbon dating, but that’s only a stopgap measure. The real challenge will be to reduce our dependence on fossil fuels.

For more on how radiocarbon dating is becoming less predictable, check out SciShow’s video below.

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