Body & Brain

Herpes sheds anytime
People carrying the contagious virus that causes genital herpes can unwittingly shed the pathogen and expose sex partners even if they never have symptoms, researchers at the University of Washington in Seattle and colleagues report in the April 13 Journal of the American Medical Association. But people who do get symptoms shed the virus more often. The scientists asked 410 people with symptomatic herpes and 88 infected people without symptoms to take daily swabs of their genital areas. These samples showed that the symptomatic people shed the virus on 20 percent of days compared with 10 percent of days in the people who showed no symptoms. It is estimated that 16 percent of U.S. adults have herpes simplex-2, but less than one-quarter of that group gets symptoms. —Nathan Seppa

More bad news on ecstasy
The club drug ecstasy may carry long-term cognitive risks, a Dutch research team finds. The scientists conducted magnetic resonance imaging on 10 young men who on average had taken 281 ecstasy tablets each over the previous six years, and also tested seven men who didn’t use the drug but who were similar to the users in other respects. The MRI brain scans showed that the users had roughly 5 percent less brain gray matter by volume than the nonusers. Reporting online April 6 in the Journal of Neurology, Neurosurgery and Psychiatry, the researchers also noted that volume of the hippocampus — the part of the brain that stores long-term memories — was 10 percent smaller in the drug users. —Nathan Seppa

High-fat diet’s quick effects on heart and brain
A high-fat, low-carb diet can trigger worrisome changes in the body in less than a week. University and hospital researchers in Oxford, England, fed 16 college-age men two different diets for five days each. One diet derived 75 percent of its calories from fat, the other got just 23 percent from fat. “Cognitive tests showed impaired attention, speed and mood after the high-fat, low-carbohydrate diet,” the researchers report in the April American Journal of Clinical Nutrition. Moreover, the scientists found that the high-fat diet boosted chemical markers of impaired heart metabolism and function in the volunteers. —Janet Raloff

Small body, big world
SAN FRANCISCO — When people are tricked into thinking their bodies are the size of Barbie’s boyfriend Ken, their world seems much bigger, a new study finds. And when the fake body is the size of a 4-meter-tall giant, the world seems to shrink. Researchers led by Henrik Ehrsson of the Karolinska Institute in Stockholm used sophisticated head-mounted cameras and simultaneous touches to a doll and the study volunteer to induce the body-swapping illusion. People who had been shrunk judged objects to be much larger than the objects were, and judged distances to be farther, too. The opposite was true for people who had been giant-sized. The results were presented April 2 at the annual meeting of the Cognitive Neuroscience Society. —Laura Sanders

Resetting elderly sleep clocks
Blame the early-bird special on a hormone imbalance. As people get older, they get up earlier, go to bed earlier and need more naps. Scientists used to think the change in sleep habits happened because molecular clocks that govern the body’s daily rhythms broke down. But researchers in Switzerland report online April 11 in the Proceedings of the National Academy of Sciences that early-to-bed, early-to-rise is in the blood. Older people’s daily, or circadian, clocks work fine; they are just being set wrong by some still-unknown hormone. The finding suggests sleep problems in the elderly might be fixable with therapies. —Tina Hesman Saey