From a study of rats, University of Pittsburgh researchers conclude that teens face a greater risk of suffering from depression and addiction than adults.
The researchers compared the brain activity of adolescent and adult rats as they worked on a task in which they anticipated a reward. Brain cell activity increased in the adolescent rats’ brains in an unusual area: the dorsal striatum (DS) — a region generally associated with habit formation, decision-making, and motivated learning. On the other hand, the adult rats’ DS areas were not triggered 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 study leader Bita Moghaddam, Ph.D., co-author of the paper and a professor of neuroscience in Pitt’s Kenneth P. Dietrich School of Arts and Sciences.
“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.”
Researchers usually investigate the association between different behaviors of adolescents and adults. This team, however, used a method they call “behavioral clamping” to see if an adolescent brain would process the same behavior differently.
To do this, they implanted electrodes into various parts of adolescent and adult rat brains, so the researchers could analyze the responses of both individual neurons and the sum of the neurons, or “population,” activity.
The teams’ hypothesis proved correct. Although the behavior was the same for both adult and adolescent rats, there was a dramatic difference in the age-related neural response in the DS during reward anticipation. This reveals that not only is reward anticipation processed differently in an adolescent brain, but that it also affects 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.”
The research team will further investigate the differences between adolescent and adult behavior, especially as it relates to stimulants — such as amphetamines — and how they influence brain activity.
David Sturman, an M.D./Ph.D. student in Pitt’s Medical Scientist Training Program, was also a co-author. The National Institute of Mental Health funded this project.
The study was recently published in the Proceedings of the National Academy of Science.
Source: University of Pittsburgh