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Rat Study Suggests Different Reward System in Teen Brain

By Rick
Nauert PhDSenior News Editor

Reviewed by John M.
Grohol, Psy.D. on January 19, 2012
A
laboratory study on rats has led researchers to propose that the growing
adolescent brain causes teens to be more susceptible to developing disorders
like addiction and depression.

The University of Pittsburgh study compared the brain activity
of adolescent and adult rats involved in a task in which they anticipated a
reward.

The researchers found increased brain cell activity in an area
of the brain called the dorsal striatum (DS) — a site commonly associated with
habit formation, decision-making, and motivated learning.

However, when adult rats were exposed to the situation, this
area of the adult rat brain did not become activated by an anticipated reward.

“The brain region traditionally associated with reward and
motivation, called the nucleus accumbens, was activated similarly in adults and
adolescents,” said Bita Moghaddam, Ph.D., a coauthor of the paper. “But the unique sensitivity of
adolescent DS to reward anticipation indicates that, in this age group, reward
can tap directly into a brain region that is critical for learning and habit
formation.”

Rather than studying the difference or similarities between the
behaviors of adolescents and adults, researchers studied brain actions to see
if similar activities were present among the two groups.

The researchers’ predictions proved accurate. Even though the
behavior was the same for both adult and adolescent rats, the researchers
observed age-related neural response differences that were especially dramatic
in the DS during reward anticipation.

This shows that not only is reward expectancy processed
differently in an adolescent brain, but also it can affect brain regions
directly responsible for decision-making and action selection.

“Adolescence is a time when the symptoms of most mental
illnesses—such as schizophrenia and bipolar and
eating disorders—are first manifested, so we believe that this is a critical
period for preventing these illnesses,” Moghaddam said.

“A better understanding of how the adolescent brain processes
reward and decision-making is critical for understanding the basis of these
vulnerabilities and designing prevention strategies.”

Researchers state that future research will continue to compare
adolescent and adult behavior, especially as it relates to stimulants—such as
amphetamines—and their influence on brain activity.

Researchers published a paper on their findings in the Proceedings of the National Academy
of Sciences.