Blogs / 80beats

In a counterintuitive new study, researchers have found that obese women get less pleasure from drinking a chocolate milkshake than average-weight women, and suggest that obese women are therefore more likely to overeat in an attempt to get that high. Researchers used a fMRI brain scanner to record women’s levels of the pleasure-providing brain chemical dopamine while they were sipping milkshakes, and found that obese women had a muted pleasure response.

They also studied a dopamine-regulating gene variant that has previously been linked to obesity, and showed that women with this variant had the lowest dopamine levels and were also very likely to gain weight over the ensuing year. Dopamine expert Nora Volkow says this furthers the research on the genetic component of obesity: “It takes the gene associated with greater vulnerability for obesity and asks the question why. What is it doing to the way the brain is functioning that would make a person more vulnerable to compulsively eat food and become obese?” [AP]

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A new study of the prairie vole, a rodent species famed for its monogamous ways, has shown that the vole’s brain chemistry changes when its mate is taken away, and that it loses some of its vim and vigor. Researchers compared the behavior of males who were separated from either their mates or their siblings, and found that those voles who had lost their loyal mates were passive and unresponsive–maybe even depressed.

Prairie voles are one of the few mammals that are generally monogamous; the mates form life-long bonds and rear their pups together. In the new study, researchers subjected all the male voles to stress tests, like dunking them in basins of water and holding them suspended by their tails, and found that the voles whose mates had been spirited away put up less struggle. In the water, for example, they floated listlessly instead of paddling for their lives. These voles “basically were passive — they gave up,” [study coauthor Larry] Young said. “I would be hesitant to say that these animals were depressed, but their behavior is reminiscent of what you would see in a depressed person” [HealthDay News].

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The little blue pills that have given so many men a sexual boost may be of some use to women as well. A small study looked at women whose sex lives had suffered as a side effect of taking antidepressants, and found that Viagra increased their sexual sensation and orgasms.

However, the pills didn’t boost the women’s sex drive, leading some experts to question whether the medication could help most women. “Viagra is not a desire drug. It dilates the blood vessels, allowing intercourse to occur,” said Rutgers University psychology professor Barry R. Komisaruk, an expert on sexual dysfunction. [Sexual health expert Leonard] Derogatis agreed: “The most prevalent female sexual dysfunction is not arousal but desire. Viagra doesn’t have a direct effect on that,” he said [Baltimore Sun].

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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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Researchers have made a map of the human brain that shows a dense network of connections at the top of the cerebral cortex, suggesting that electrical signals travel through this hub on their way to more specialized regions. “This is just about the coolest paper I’ve seen in a long time, and forward-looking in terms of where the science is going,” said Dr. Marcus E. Raichle, a professor of neurology and radiology… who was not involved in the research. He added, “They’ve found in the brain what looks like a hub map of the airline system for the United States” [The New York Times].

An international team of researchers used a technique called diffusion spectrum imaging to map the connections between different parts of the brain. The technique traces the path of water moving along axons, long fibers that extend from a neuron’s main body and carry electrical signals [Science News]. They found the most connections at the top of the cortex along the crack that separates the brain’s two hemispheres. According to researchers, that area is not only a relay station, it’s also the area that’s most active when the brain is in “default mode,” the activation state present when the brain is not engaged in any specific cognitive task [The Scientist].

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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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