Neural Basis of Decisions about Uncertain Rewards

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DESCRIPTION (provided by applicant): The willingness to engage in risky behaviors is hallmark of drug addiction, gambling, and obesity. Presumably, one chooses to administer an illicit drug, over-consume a fat-laden meal, or put $1000 on red because the immediate outcome of the choice is potentially rewarding. The goal of this proposal is to identify patterns of activity in neural structures involved in evaluating rewards and making decisions between certain and risky outcomes that will inform how risk-preference is represented in the activity of single neurons. Rats will be trained to perform a Risk task, in which they choose between two levers in a test chamber that lead to different reward outcomes (sucrose pellets). Pressing the Certain lever always earns a Small reward, and pressing the Uncertain lever will either pay a Large reward or Omit the reward. Large or Omitted reward outcome is chosen randomly, so that subjects cannot track the number of Large outcomes to maximize overall payoffs across trials. In a forced response block, each lever will be presented alone on alternate trials, which provides the opportunity for the rat to equally sample both behavioral options and their associated consequences. This is followed by a free choice block, in which both levers are presented simultaneously and rats are able to select one. Analyses of choices will focus on risk-preference across sessions and the influence of reward-history on upcoming choices. While rats perform the Risk task we will record the electrophysiological activity of single neurons in the Nucleus Accumbens (NAc), which is critical for reward processing and in the Orbitofrontal cortex (OFC), an area thought to be important for making decisions based on reward outcome. In both NAc and OFC, we will measure responses to events leading up to, during, and following reward delivery or omission. The level of neural activity will be compared across the two behavioral responses (Certain-Uncertain), when freely chosen or not, and to the three possible outcomes (Small, Large, Omit). The long-term goal of our studies is to determine how aberrant signaling in these areas may underlie inaccurate representations of reward which may in turn lead to over-valuation of risky behaviors. PUBLIC HEALTH RELEVANCE: The pervasive problems associated with drug addiction, gambling, or overconsumption (of food or goods) stem from a willingness to engage in behaviors that yield risky outcomes. The goal of this project is to identify patterns of activity in neural structures involved in evaluating rewards and making decisions about choices with risky consequences that will inform how risk-preference is represented in the activity of single neurons. These studies have the potential to identify mechanisms of risk-prone behaviors and therefore new targets for their treatment.