WASHINGTON — Tuesday, November 18, 2008, was the fourth day of the Society for Neuroscience annual meeting, and topics remained diverse: What happens in the brain when teenagers feel peer pressure, a study in mice suggesting a new way to treat depression, the best way to relearn walking after a stroke, and the long lasting effects of disrupted sleep.
Peer pressure on the brain All too often, teenagers act recklessly and even dangerously around their friends. A new study suggests that this rash behavior feeds off the teen brain’s sensitivity to social and emotional influences, which is substantially unbridled because a cognitive and behavioral control network is not yet mature.
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Remembering and forgetting — and walking When out on a stroll, most people focus on the flowers or their surroundings, not their legs. But people recovering from a stroke often try to consciously control their movements in an effort to regain their normal gait. Now scientists propose a different tact for these folks: don’t think about it. A study at Johns Hopkins University shows that focusing on something other than walking may help patients in the long run. Researchers studied three groups of healthy volunteers on a treadmill to see how distraction affects learning and retention when learning a new walking pattern. A split-belt treadmill was set so that one leg moved three times faster than the other leg. The first group adapted to the new pace without instruction. A second group received visual and verbal feedback about their stepping patterns, while the third group was distracted during the training process and asked to watch a sitcom and then answer questions about the program. People in all three groups adapted to the new pace within 15 minutes, although the distracted walkers were slower to pick up the pace. When subjects were then instructed to return to normal walking patterns, the distracted walkers again lagged behind the others in adapting to the change, despite removal of the distraction. “By distracting subjects during training, we may be drawing on more subconscious areas of the brain,” says Laura Malone, a doctoral student who worked with Amy Bastian on the study. “While these brain centers are slower to learn new information, they are also slower to forget.” The scientists now plan to take the study a step further and test the approach on patients recovering from strokes. — Susan Gaidos
Weeks later, sluggishness from disrupted sleep remains Sleep that is constantly disrupted — such as that experienced by new parents, the elderly and those with sleep apnea — can cause sluggish thinking weeks after sleep habits return to normal, suggests new research in rats. Scientists knew that the rat dentate gyrus, an area of the brain’s hippocampus involved with memories, has difficulty growing new nerve cells when the rodents get only fragmented sleep. To investigate the longer term effect of fractured sleep on learning, researchers connected electrodes to the brains of 11 rats whose cage bottoms were treadmills. Whenever a computer detected that a rat had been sleeping for 30 seconds, the treadmill turned on, waking the animal. The rats experienced this disrupted sleep for 12 days and then were allowed to sleep as much as they wanted for two weeks. Led by Dennis McGinty, chief of neurophysiology research at the Sepulveda Veterans Affairs Medical Center in California, the researchers then gave the rats some tasks. In five trials over five days the rats had to pick out an escape hole from 22 holes on the perimeter of a large platform. On the sixth day, the position of the hole changed. Control rats, whose sleep had not been disrupted, began by randomly checking holes, then sequentially checking them, and then going right to the hole. But the sleep-deprived rats had trouble finding the escape hatch and took longer to find the new route when the location changed. McGinty likens the sleep-deprived rats to elderly people who no longer remember where their car is parked in a big garage. “Something about the continuity [of sleep] is crucial,” he says. —Rachel Ehrenberg