Thaindian News

Washington, June 4 (IANS) A specific brain system propels teenagers to indulge in risky behaviours, experiment with drugs or have unsafe sex, says new research.
Russell Poldrack, at the University of Texas, Austin, and associates have taken the first major step in identifying which brain systems cause adolescents to have these urges.

“Our results raise the hypothesis that these risky behaviours, such as experimenting with drugs or having unsafe sex, are actually driven by over-activity in the mesolimbic dopamine system, a system which appears to be the final pathway to all addictions, in the adolescent brain,” Poldrack said.

Dopamine is known to be important for the motivation to seek rewards.

Poldrack, professor of psychology and neurobiology, directs UT-A’s Imaging Research Centre, where researchers use functional Magnetic Resonance Imaging technology (fMRI) to study brain activity.

Participants aged between eight and 30 years performed a learning task in which they categorised an abstract image into one of two categories and were given feedback displaying the correct response.

To ensure motivation, they were given monetary rewards for each correct answer.

What the researchers were most interested in, however, was how each participant’s brain responded to “reward prediction error” (or the difference between an expected outcome of an action and the actual outcome) as they learnt to categorise the images.

“Learning seems to rely on prediction error because if the world is exactly as you expected it to be, there is nothing new to learn,” Poldrack said.

Previous research has shown that the dopamine system in the brain is directly responsive to prediction errors.

Researchers measured so-called positive prediction error signals in the participants’ brains as the participants discovered the results of their answers and the size of their rewards.

Teenagers showed the highest spikes in these prediction error signals, which likely means they had the largest dopamine response, said a University of Texas release.

It follows, then, that the greater prediction error signals in the adolescent brain could result in increased motivation to acquire more positive outcomes, and therefore greater risk-taking.

These findings were published online in Nature Neuroscience.