Random Samples

Science  21 Aug 2009:
Vol. 325, Issue 5943, pp. 923
  1. The Telltale Amygdala

    CREDIT: REUTERS PHOTOGRAPHER

    Brain scans of Israeli paramedics suggest that it's possible to predict how well an individual will respond to stress.

    Scientists at Tel Aviv University have performed an unusual prospective study to see if they could identify brain differences between emotionally resilient people and those who respond poorly to traumatic events. They recruited 50 18-year-old Israelis, half of them female, who were starting training as paramedics. They scanned them with functional magnetic resonance imaging while flashing photographs of military medical scenes. The recruits were also scored on stress-related symptoms such as anxiety and difficulty sleeping.

    Eighteen months later, all the paramedics had been through rough emotional experiences dealing with combat casualties. The scientists, led by brain imager Roee Admon, again put them through the brain-scan experiment. Reporting online 5 August in the Proceedings of the National Academy of Sciences, the researchers found that the paramedics who reported the largest increase in stress symptoms had also showed the most activity in the amygdala—the seat of fear in the brain—in the first test.

    Co-author Talma Hendler says the amygdala may turn out to be an “a priori biological marker” for factors that make people liable to post-traumatic stress disorder. The study shows that these factors “can be sensitively identified with brain imaging in otherwise healthy subjects,” says psychiatrist Amit Etkin of Stanford University in Palo Alto, California.

  2. Youth Bulge

    CREDIT: (SOURCE) PRB/U.N.

    Twenty percent of the world's population is between the ages of 18 and 24, according to the latest report from the Population Reference Bureau. In sub-Saharan African nations, two-thirds of the population is in that age range. The “youth bulge” won't be abating there anytime soon: In Mali, for example, 50% of women become mothers in their teens, and women's average ideal family size is slightly fewer than six children.

  3. Put on a Happy Face

    Helping others is supposed to make you feel good, but there may be surer routes to cheer, according to a U.K. psychologist.

    Richard Wiseman of the University of Hertfordshire wants to know how the general public can get happier, so this month he conducted an Internet experiment. He divided his 26,000 respondents—mostly young adults—into five groups. One was a control group. During the 5-day exercise, each of the other groups engaged in one type of upbeat behavior: being kind to others, dwelling on a happy memory, feeling grateful, or smiling.

    The results: All groups reported rises in happiness, including 50% of the controls. Among those who thought about something positive that had happened the day before, 65% felt better, and the gratitude and smiling groups came in at 58%. But those in the “acts of kindness” group were no cheerier than the controls—which was “a bit disappointing,” says Wiseman.

    Wiseman says in most surveys, about 50% report themselves as happy, 30% unhappy, and the rest don't know. He hasn't yet calculated from this experiment whether the already-happy got happier or whether actions such as gratitude and smiling can pull people up from the dumps.

  4. Hominids' Diverse Tastes

    CREDIT: CARLES LALUEZA-FOX

    Humans vary genetically in their ability to taste a bitter chemical known as phenylthiocarbamide, which has been compared to bitter flavors in Brussels sprouts, cabbage, and broccoli.

    About 75% of people can detect these flavors because they possess a “taster” variant of the TAS2R38 gene. People without this variant are insensitive to bitter fruits and vegetables. Now Spanish researchers say that analysis of DNA recovered from the bone of a Neandertal in El Sidrón cave in northern Spain reveals that he had both the taster and the nontaster versions of the gene, meaning that the gene existed 40,000 years ago. That indicates that a common ancestor of Neandertals and Homo sapiens must have carried both variants, suggesting that differences in the ability to detect bitterness stretch back at least half a million years, the team reported last week in Biology Letters.

    “The standard assumption is that these bitter chemicals are bad for us—and thus being a taster would be advantageous,” says anthropological geneticist Anne Stone of Arizona State University in Tempe. But the fact that both variants have survived suggests that some bitter foods may contain advantageous properties, she says. Study director Carles Lalueza-Fox of the Institute of Evolutionary Biology in Barcelona, Spain, adds that the study shows that Neandertals, renowned for their reliance on meat to thrive in frigid habitats, also “had some significant intake of vegetables in their diet.”

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