Science & Technology/Deal or No Deal?

Issue Date: 
January 8, 2007

Need for immediate rewards linked to move active region of the brain

Deal or No Deal? How people might play this popular game show—whether they would likely accept an offer for quick cash or opt to hold out for the chance to take home $1 million—probably has less to do with what could be inside each briefcase than what’s inside each contestant’s brain, a new Pitt study suggests.
Pitt investigators didn’t study any of the game’s players nor did they offer stakes nearly as high, but their research on 45 normal adult volunteers, who were taunted with the prospect of getting between 10 cents and $105 at that very moment or waiting one week to five years for a sure $100, provides new insight about reward-based decision making and may have implications for understanding and treating addiction disorders.

Not only do people differ in their preferences for immediate over delayed rewards of larger value, the researchers wrote in the December Journal of Neuroscience, but these individual traits are mirrored by the level of activity in the ventral striatum, a key part of the brain’s circuitry involved in mediating behavioral responses and physiological states associated with reward and pleasure. Research volunteers classified as more impulsive decision makers, who tend to seek rewards in the here and now, had significantly more activity in the ventral striatum.

The preference for immediate over delayed rewards of larger value, which researchers term “delay discounting,” has already been linked to impulse-control problems such as substance abuse, addiction, and pathological gambling. Separate studies have shown that people with addiction disorders have a more active ventral striatum. The current study is the first to look at the relationship between individual differences in discounting behavior and individual ventral striatum activity, which in finding a strong connection between brain and behavior in normal subjects suggests the same neurocognitive mechanism could contribute to increased risk for addiction as well.

“The ventral striatum appears to be a nexus where we balance acting impulsively to achieve instant gratification and making prudent choices that may delay rewards. Understanding what drives individual differences in ventral striatal sensitivity could aid efforts to treat people who have difficulty controlling impulsive behavior, by adjusting the circuitry,” explained lead author Ahmad R. Hariri, Pitt assistant professor of psychiatry and director of the Developmental Imaging Genetics Program in the Pitt School of Medicine and Western Psychiatric Institute and Clinic.

Based on their findings, Hariri and his colleagues are looking at whether ventral striatum activity can help predict substance abuse disorders in those at risk. Since the activity of the ventral striatum is modulated by dopamine, a brain chemical also associated with reward, they plan to explore the role that variations in dopamine-related genes may play in determining differences in ventral striatum reactivity.

“Addiction and problem gambling represent behaviors on the extreme end of the continuum,” Hariri said. “But even in the most common, day-to-day situations, reward-based decisions dictate how we behave. For example, individual preferences for immediate versus delayed rewards could explain why some can’t resist the temptation of dessert, an immediate gratification, while others will opt for a five-mile run knowing it will help shed pounds, a delayed gratification. Food, sex, and money are all sources of pleasure, yet individuals differ greatly in the rewarding aspects they derive from these pleasures.”

The research was supported by the National Institute of Mental Health and the National Heart, Lung, and Blood Institute and by a NARSAD Young Investigators Award given to Hariri.