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Scientists Find Neurological Basis of Risk-Taking Trait

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How do we calculate the right time to take a risk? And why are some people (and dogs, and fish, and rats) bigger daredevils than others? Scientists working with rats say they’ve traced the answers back to a brain region called the nucleus accumbens. They published their findings this week in the journal Nature.

Animals and risk have a curious relationship. Scientists have tested the risk-taking behaviors of many species (including humans), and nearly all of them, when taken as a whole, are more conservative than they need to be. But within each species, there are individual animals who seem to throw care to the wind, and even the most conservative individuals take risks from time to time. 

“Risky behavior has its moments where it’s valuable,” psychiatrist, bioengineer, and study co-author Karl Deisseroth said in a press statement. “As a species, we wouldn’t have come as far as we have without it.”

A little risk-taking is important to keep a species, and an individual, going. But, Deisseroth notes, a predilection for dangerous choices is a liability. “I’ve seen patients whose aberrantly high-risk-seeking activity resulted in accidents, addictions and social, financial or occupational failures that exposed them to a lot of harm and blame.” 

The researchers were looking at the brain’s reward system, which uses hormones like dopamine to motivate us to seek out or avoid objects or experiences, from an angry boss to a cheeseburger. Inside your reward system, and the reward system of other animals, is a structure called the nucleus accumbens (NA). Your NA contains two categories of dopamine receptor cells called DR1 and DR2.

For this experiment, the researchers focused on DR2 cells. They implanted teeny-tiny optical fibers in the brains of lab rats, then taught the rats to gamble. (Fun fact: this is not the first time rats have learned to play the odds.) 

Each rat was set up with a little game center equipped with a hole. When they felt like playing, the rats could poke their noses into the hole, which would trigger the appearance of two levers. Pulling one lever produced sugar water—the same amount every time, no matter what, like a steady paycheck. The other lever was more like a freelance career. Most of the time, pulling lever 2 yielded a little bit of sugar water, but every so often it would pay off with a much bigger helping. The rats could (and did) play the game 200 times a day. 

As expected, about two-thirds of the rats repeatedly went for the dependable sugar water salary. The other third were bred-in-the-bone freelancers. Even after the researchers switched the levers, the rats kept to their preferences. But just like in the real world, some of the conservative rats occasionally went for the risky lever instead. If their risk paid off that first time, they’d keep taking the risk. If it didn’t, they’d go back to their steady sugar paycheck.

While the rats were gambling the day away, the researchers were watching their DR2 cells. They found that just before the conservative rats chose a level, DR2 activity spiked. When the scientists used the optical fibers to light up the risky rats’ DR2 cells, they became more risk-averse, but only as long as the fibers were lit. As soon as the light went off, they went back to their risky behavior. 

Then the researchers gave the rats small doses of pramipexole, a Parkinson’s disease drug that is notorious for causing impulsive gambling in patients. Sure enough, once the drug was in their system, the salaried rats turned to the high-risk freelance life. 

In other words, high DR2 activity in the nucleus accumbens kept conservative rats conservative. “It looks as though we have found a brain signal that, in most individuals, corresponds to a memory of a failed risky choice,” Deisseroth said. “It seems to represent the memory of that recent unfavorable outcome, manifested later at just the right time when it can, and does, modify an upcoming decision.” 

“Humans and rats have similar brain structures involved,” said Karl Deisseroth, MD, PhD, professor of bioengineering and of psychiatry and behavioral sciences. “And we found that a drug known to increase risk preference in people had the same effect on the rats. So every indication is that these findings are relevant to humans.”

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Big Questions
Why Do Cats Freak Out After Pooping?
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Cats often exhibit some very peculiar behavior, from getting into deadly combat situations with their own tail to pouncing on unsuspecting humans. Among their most curious habits: running from their litter box like a greyhound after moving their bowels. Are they running from their own fecal matter? Has waste elimination prompted a sense of euphoria?

Experts—if anyone is said to qualify as an expert in post-poop moods—aren’t exactly sure, but they’ve presented a number of entertaining theories. From a biological standpoint, some animal behaviorists suspect that a cat bolting after a deposit might stem from fears that a predator could track them based on the smell of their waste. But researchers are quick to note that they haven’t observed cats run from their BMs in the wild.

Biology also has a little bit to do with another theory, which postulates that cats used to getting their rear ends licked by their mother after defecating as kittens are showing off their independence by sprinting away, their butts having taken on self-cleaning properties in adulthood.

Not convinced? You might find another idea more plausible: Both humans and cats have a vagus nerve running from their brain stem. In both species, the nerve can be stimulated by defecation, leading to a pleasurable sensation and what some have labeled “poo-phoria,” or post-poop elation. In running, the cat may simply be working off excess energy brought on by stimulation of the nerve.

Less interesting is the notion that notoriously hygienic cats may simply want to shake off excess litter or fecal matter by running a 100-meter dash, or that a digestive problem has led to some discomfort they’re attempting to flee from. The fact is, so little research has been done in the field of pooping cat mania that there’s no universally accepted answer. Like so much of what makes cats tick, a definitive motivation will have to remain a mystery.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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Animals
Watch a School of Humpback Whales 'Fish' Using Nets Made of Bubbles 

Just like humans, humpback whales catch many fish at once by using nets—but instead of being woven from fibers, their nets are made of bubbles.

Unique to humpbacks, the behavior known as bubble-net feeding was recently captured in a dramatic drone video that was created by GoPro and spotted by Smithsonian. The footage features a school of whales swimming off Maskelyne Island in British Columbia, Canada, in pursuit of food. The whales dive down, and a large circle of bubbles forms on the water's surface. Then, the marine mammals burst into the air, like circus animals jumping through a ring, and appear to swallow their meal.

The video offers a phenomenal aerial view of the feeding whales, but it only captures part of the underwater ritual. It begins with the group's leader, who locates schools of fish and krill and homes in on them. Then, it spirals to the water's surface while expelling air from its blowhole. This action creates the bubble ring, which works like a net to contain the prey.

Another whale emits a loud "trumpeting feeding call," which may stun and frighten the fish into forming tighter schools. Then, the rest of the whales herd the fish upwards and burst forth from the water, their mouths open wide to receive the fruits of their labor.

Watch the intricate—and beautiful—feeding process below:

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