This is not an “eat dirt for your health and happiness” study. You don’t need to shovel soil in your mouth. Just go outside.

Biologist Dorothy Matthews and company wanted to test a particular bacteria, Mycobacterium vaccae. It’s found commonly in the soil and carried widely through the air, so if you take a walk in the park you’ll probably breathe it in. Previous studies have shown that the bacterium increases serotonin in the brain, and have even suggested that the bacterium has antidepressant qualities. Since the neurotransmitter serotonin is also involved in cognition, the team wanted to see if the bacterium could have a direct effect on learning. Indeed it did, Matthews’ team announced at the General Meeting of the American Society for Microbiology in San Diego.

In a classic test of learning ability, Matthews gave mice a treat – white bread with peanut butter – as a reward to encourage them to learn to run through a maze. When she laced the treat with a tiny bit of Mycobacterium vaccae, she found that the mice ran through the maze twice as fast as mice that were given plain peanut butter [New Scientist].

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Locusts are prompted to band together in enormous, destructive swarms by the same brain chemical that is linked to happiness in humans. A fascinating new study has found that locusts that are about to swarm experience a sudden surge of serotonin, the same neurotransmitter that’s targeted by antidepressant drugs. “Here we have a solitary and lonely creature, the desert locust. But just give them a little serotonin, and they go and join a gang,” observed Malcolm Burrows [AP], one of the study’s authors.

Researchers say the findings may lead to methods to block the formation of locust swarms. These infestations, which can cover hundreds of square miles and involve billions of vegetation-munching insects, can devastate agriculture and cost tens of millions of dollars to control [The New York Times].

Because locusts usually avoid each other, it’s only dire circumstances that bring them together in buzzing hordes. For instance, unpredictable desert rains cause vegetation blooms, which in turn makes locust populations skyrocket. But as the rains abate and fertile land shrivels up, locusts crowd together in the remaining green patches. Eventually, the swarm trigger goes off and the locusts take to the skies—”a strategy of desperation driven by hunger,” [National Geographic News], says coauthor Stephen Rogers. When they make that behavior shift they also change appearance dramatically, going from light green to dark brown.

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Researchers have the best evidence yet that the brain chemical serotonin plays a role in sudden infant death sydrome (SIDS).

In a new study, researchers genetically engineered mice to have low levels of serotonin at birth, and found that more than half of the mice abruptly died before they were 3 months old. More intriguing, they had erratic episodes where their heart rate would drop and, five to 10 minutes later, so would their body temperature, [study author Cornelius] Gross reported. Sometimes they died in the midst of what Gross calls those crises, other times afterward [AP].

Serotonin is most commonly known as a mood regulator involved in depression, but it also helps control some of the body’s most basic functions, including breathing, heart rate, and body temperature. The mouse study supports earlier data gathered from the autopsied brain tissue of SIDS babies, which showed alterations in brainstem nerve cells that communicate using serotonin.

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Here’s one easy way to help avoid conflict and strife in your interactions with others: When you eat your three square meals a day, don’t skimp on the meats and cheeses.

Those foods contain high levels of the amino acid tryptophan, which the body needs to produce the neurotransmitter serotonin, a chemical in the brain that plays a role in regulating mood, aggression and social behavior. In a new study, test subjects with high serotonin levels responded less aggressively while making emotionally charged financial decisions in a test known as the ultimatum game.

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