UNIVERSITY

PARK, Pa. — Different parts of the brain mature at different times,

which may help to explain impulsive behaviors in adolescence, suggest

researchers from Penn State and the University of Pittsburgh.

The team discovered that the brain’s salience network, a group of

regions that work together to help people assess the importance of

stimuli in their environment, played a key role in regulating

self-control behavior when participants were motivated by incentives.

Most previous research in this area had focused on one region of the

brain. Rather than using this approach, Michael Hallquist, assistant

professor of psychology, Penn State, and an Institute for CyberScience

faculty co-hire, sought to investigate communication among different

regions of the brain.

“This is one of the first studies to look at the integration of

reward circuitry and cognitive control from a functional network

perspective,” Hallquist said. “Rather than testing Region A or Region B,

our study describes the intrinsically connected networks, like the

salience network.”

They designed an experiment that combined eye-tracking and functional

magnetic resonance imaging tools to get a better view of what brain

regions were involved in a task requiring self-control. Study

participants had to look away from a dot that appeared on a screen, a

common neurocognitive test known as an antisaccade.

Hallquist and his collaborators built on this by integrating

motivational cues, such as the promise of a financial reward based on a

person’s performance on the test. This was designed to assess three

aspects of motivated behavior. They report their results in a recent

issue of NeuroImage.

“First, you process a cue that may have motivational significance,

such as seeing a box of cookies,” said Hallquist. “Second, there is

anticipation, like thinking about the taste of the cookies as you open

the box. Lastly, there is the hedonic value of eating the cookies,”

Hallquist said.

One hundred forty participants aged 10 to 25 years took part in the

study. After analyzing data with the help of Penn State’s supercomputer,

the ICS Advanced CyberInfrastructure, Hallquist was able to study the

interactions among brain regions during the task.

“Over the course of development,” Hallquist said, “people get better

at these kinds of tasks, and there is some evidence that providing

rewards can enhance your performance.”

The ventral striatum, a key player in reward processing, is often

more active in teens than children or adults when given rewards.

Although reward and loss cues boosted performance as expected, Hallquist

and colleagues did not find evidence that this reflected greater

integration of reward-related circuits and control networks. Rather,

incentives appear to facilitate developmental improvements on the tasks

via the salience network.

The salience network is involved in considering whether something is

worth our attention, whether it be good or bad. Greater activity of the

salience network immediately before the dot appeared on the screen

predicted that the individual would successfully look away.

Older individuals recruited the salience network to a greater extent

when preparing to complete the task, which the scientists suggest may

help increase their inhibitory control. By contrast, ventral striatum

activity was greater in teens in the outcome phase, yet this activity

was not associated with inhibitory control.

This finding is consistent with the idea that greater ventral

striatum activity in adolescence may be linked more with greater

experience of the third component of rewards, pleasure after an outcome

has occurred.

The developing salience network in adolescents may be one mechanism

underlying impulsive behavior. In particular, being able to assess the

importance of an upcoming decision based on reward or punishment cues

may help adults successfully inhibit choices that lead to an undesirable

outcome, whereas this ability is still developing in adolescence.

Charles F. Geier, associate professor of human development and family

studies, Penn State, and Beatriz Luna, Pittsburgh University of

Medicine, collaborated on this work.

The National Institute of Mental Health supported this research.