Teen brain learns to just say no

U. OREGON (US) — Just when they (and their parents) may need it most, children’s brains develop the ability to resist risky behavior as they enter adolescence.

For a new study, published in the journal Neuron, 24 girls and 14 boys from ethnically and socioeconomically diverse backgrounds underwent functional magnetic resonance imaging (fMRI) scans at age 10 and again at 13, when they moved into early adolescence.

Each time, they were presented with photos of faces making neutral, angry, fearful, happy, and sad emotional expressions.

Non-invasive fMRI, when focused on the brain, measures blood flow changes using a magnetic field and radio frequency pulses, producing detailed images depicting brain activity.

Activity significantly increased in the ventral striatum and the ventral medial portion of the prefrontal cortex between 10 and 13. In addition to the scans, children were asked to self-report on their ability to resist peer influences and engagement in risky or delinquent behavior.

The most enhanced response occurred in the ventral striatum, a brain region most frequently associated with reward-related processing. Over time, increases in brain activity there correlated with increases in children’s resistance to peer influence.

“This is a complex point, because people tend to think of adolescence as the time when teenagers are really susceptible to peer pressure,” says Jennifer H. Pfeifer, professor of psychology at the University of Oregon.

“That is the case, but in addition to that added susceptibility they are also improving their ability to resist it. It’s just that peer pressure is increasing because they spend a lot more time with peers during this time and less time with family. So it is a good thing that resistance to such influences is actually strengthening in their brains.”

This study, which researchers believe to be the first to report longitudinal fMRI findings about changes in the way the brain processes emotion during this time, appears to mesh with evidence that ventral striatum development during early adolescence is critical to emotional regulation carried out by the brain’s prefrontal circuitry.

“This is basic research that hopefully is laying the foundation for future studies with even more clinical relevance,” Pfeifer says.

“We really have a lot to learn about how the brain responds to really basic emotional stimuli across development.”

An unexpected side finding of the study shows significant increases in the amygdale—a small almond-shaped mass centrally located deep in the brain—but only when shown sad faces.

The amygdala plays a major role in emotional reactivity and Pfeifer says, the response to sad faces could somehow be tied to the emergence of depression, especially in girls.

“The span from age 9 to 13 is critical in pubertal development. How do individual differences apply here,” says Pfeifer.

“Identifying this response to ‘sadness’ might be related to the increase in depression that we see as kids enter puberty. Rates of depression are particularly enhanced for teen girls. Is this increased response to sad faces somehow part of that?”

Researchers at the University of California, Davis and the University of California, Los Angeles contributed to the study which was funded by National Institutes of Health.

More news from University of Oregon: http://uonews.uoregon.edu/