Summary: Researchers have identified a specific network in the brain that appears to be associated with risk and reward assessment.
New research provides fresh insight into how the brain processes reward and punishment, opening new avenues for developing treatment of conditions ranging from anxiety to addictive behaviors such as drug abuse.
The study, published in the journal eLife, used a rodent model to identify a specific network within the brain closely tied to risk assessment.
“Our actions often involve varying risks of an aversive outcome. Our brains need to factor in this risk for optimal decision making,” said study author Bita Moghaddam, Ph.D., professor and chair of behavioral neuroscience in the OHSU School of Medicine, Portland, Oregon. “An exaggerated response to risk may lead to anxiety whereas an abnormally low response may lead to impulsivity and reckless behavior.”
Moghaddam and co-author Junchol Park, Ph.D., at the University of Pittsburgh, found sharp distinctions in the level of coordination between a spike in dopamine neurons and activity within the prefrontal cortex, the portion of the brain that regulates complex cognitive functioning. They discovered close coordination between activity in the prefrontal cortex and dopamine levels when there was no risk of punishment – in this case, a food pellet dispensed in a chamber.
“In the real world, it’s almost never like that,” Moghaddam said. “Most of what we do involves risk.”
To that end, the researchers also measured brain activity in blocks of time when a small shock was administered 10 percent of the time. In sharp contrast to the no-punishment scenario, they found that coordination between the prefrontal cortex and dopamine levels collapsed when there was a small risk of punishment. Moghaddam said that may be a good thing because it means the brain encodes an ingrained assessment of risk in normal circumstances.
“There is a fine balance between normal functioning of risk assessment and harmful behaviors,” she said.
The study points the way toward additional research into behavioral or pharmaceutical treatments that may be effective in reducing either anxiety or impulsivity encoded within the physiology of the brain itself, Moghaddam said. She said the study suggests new avenues of research that could involve functional magnetic resonance imaging of people given risk-reward tasks such as gambling.
“Proper encoding of punishment risk and its contingency on actions and outcomes are fundamental to adaptive behavior and survival,” the authors concluded.
Funding: The study was supported by the National Institute of Mental Health of the National Institutes of Health (grant R56MH084906).
Source: Erik Robinson – OHSU
Publisher: Organized by NeuroscienceNews.com.
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Original Research: Abstract for “Risk of punishment influences discrete and coordinated encoding of reward-guided actions by prefrontal cortex and VTA neurons” by Junchol Park and Bita Moghaddam in eLife. Published online October 23 2017 doi:10.7554/eLife.30056
Risk of punishment influences discrete and coordinated encoding of reward-guided actions by prefrontal cortex and VTA neurons
Actions motivated by rewards are often associated with risk of punishment. Little is known about the neural representation of punishment risk during reward-seeking behavior. We modeled this circumstance in rats by designing a task where actions were consistently rewarded but probabilistically punished. Spike activity and local field potentials were recorded during task performance simultaneously from VTA and mPFC, two reciprocally connected regions implicated in reward-seeking and aversive behaviors. At the single unit level, we found that ensembles of putative dopamine and non-dopamine VTA neurons and mPFC neurons encode the relationship between action and punishment. At the network level, we found that coherent theta oscillations synchronize VTA and mPFC in a bottom-up direction, effectively phase-modulating the neuronal spike activity in the two regions during punishment-free actions. This synchrony declined as a function of punishment probability, suggesting that during reward-seeking actions, risk of punishment diminishes VTA-driven neural synchrony between the two regions.
“Risk of punishment influences discrete and coordinated encoding of reward-guided actions by prefrontal cortex and VTA neurons” by Junchol Park and Bita Moghaddam in eLife. Published online October 23 2017 doi:10.7554/eLife.30056