Be Well

Why success may breed success

By Elizabeth Cooney
Globe Correspondent / August 3, 2009

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We might not learn from our mistakes after all, according to new research from scientists at MIT. In experiments that give a snapshot of the learning process in the brain, they found that getting the correct answer to a challenge meant doing better on the next one. But wrong answers failed to bring any improvement.

Earl K. Miller of MIT’s Picower Institute for Learning and Memory and two colleagues gave monkeys the task of tracking two alternating images on a computer screen. For one picture, they were supposed to shift their gaze to the right and for the other they were supposed to look left. If they moved their eyes the correct way, they were rewarded with drops of juice. After a right answer - but not after a wrong one - the monkeys were more likely to be right on the pictures that flashed a few seconds later.

Signals between two parts of the brain involved in learning - the prefrontal cortex and the basal ganglia - showed the researchers what was happening. Single nerve cells fired for several seconds after both right and wrong answers, but the electrical impulses were more robust after the right answer, helping the monkeys on the next pair of pictures.

“This explains on a neural level why we seem to learn more from our successes than our failures,’’ Miller said.

BOTTOM LINE: Experiments tracking brain cell activity showed why monkeys learned from their successes but not their failures.

CAUTIONS: The monkey experiment considered the impact of only immediate rewards, not future benefits that might motivate human learning.

WHERE TO FIND IT: Neuron, July 30

Vitamin D deficit

A new study shows that most American children don’t have enough vitamin D and their low levels might put them at higher risk for bone and cardiovascular disease.

Seven out of 10 US children and adolescents are low in vitamin D, researchers led by Dr. Juhi Kumar of Albert Einstein College of Medicine report, based on data from more than 6,000 children ages 1 to 21 in the National Health and Nutrition Examination Survey 2001-2004. Expanded to the US population, that translates to 50.8 million children having vitamin D insufficiency and 7.6 million children having the more serious vitamin D deficiency, according to government standards.

Children who had low levels of vitamin D were more likely than other children to have high blood pressure, low levels of “good’’ cholesterol, and low calcium, all risk factors for heart disease and stroke. They also had lower levels of a hormone tied to bone disease than children with adequate vitamin D.

Girls, adolescents, obese children, children who drank milk less than once a week, and children who watched television or used a computer more than four hours a day were more likely than other children to have insufficient or deficient vitamin D. Even after accounting for these variables, non-Hispanic black and Mexican-American children were more likely to lack vitamin D and have higher cardiovascular risk factors. Other research suggests darker skin may absorb less sunlight, which helps the body make the vitamin.

BOTTOM LINE: Seven out of 10 American children aren’t getting the vitamin D they need, possibly putting them at risk for bone and cardiovascular disease.

CAUTIONS: The study can show an association between vitamin D levels and risk factors for disease, but it can’t determine cause and effect.

WHERE TO FIND IT: Pediatrics, September 2009