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Teen brain keeps change in high gear

BROWN (US) — Changes to the teenage brain are still going strong long after physical growth spurts have petered out.

During the teen years, the brain develops new connections  but spends more time pruning away those that are no longer needed. New research, published in the journal Sleep, finds that reduction keeps the pace even as the teens approach adulthood.

“There was a sense that the bulk of the change is happening in the younger adolescents,” says Mary Carskadon, professor of psychiatry at Brown University. “To see a continuation of this rapid and large change in the older adolescents was a surprise.”

For the study, five boys and nine girls aged 15 and 16 were asked to sleep to certain preparatory specifications for a week at home and then to spend two nights in the lab while the team took all-night measurements.

The teens were brought back two or three years later, between the ages of 17 and 19, for another week of preparatory sleep and then two more nights of monitored sleep.

Additional changes were noted over time. For example, late teens continue an earlier teen trend of spending less and less time in so-called “slow-wave” sleep in favor of “stage 2” sleep.

Also, the reduction in electroencephalography (EEG) power seems to shift from the left side early in the teen years to the right side later in adolescence. That shift means that by the end of the teen years, the developmental process has occurred equally on both sides.

Although many previous studies using EEG, magnetic resonance imaging, or postmortem examination have yielded similar measurements of adolescent brain changes, this study added insight because of how it was structured, says lead author Leila Tarokh, adjunct assistant professor of psychiatry and human behavior at Brown, and a researcher at the University of Zurich.

“The unique feature of this study is that it puts together these EEG measures of power and looks at these sleep stages longitudinally (in the same people over time) and across several regions around the brain.”

Sleep is a convenient time to take long-term, well controlled measurements of neural activity, but the study does not show the role sleep may play in neural renovation among older teenagers, Carskadon says. “For us, sleep is a window onto the brain.”

Researchers from the University of Colorado-Boulder contributed to the study, that was funded by the National Institute on Alcohol Abuse and Alcoholism.

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