Talks and Conference Presentations

Organization for Human Brain Mapping
11th Annual Meeting
June 13-16, 2005
Toronto, Canada

• Effects of risk-reward context upon the evaluation of monetary rewards
  Evan M. Gordon¹, Brent T. Warner¹, Jonathan K. Smith¹, and Scott A. Huettel^{1,2
  1}Brain Imaging and Analysis Center; ²Department of Psychiatry, Duke University Medical Center

  A central component of decision making is the ability to accurately balance potential rewards against their associated risks. Single-unit and neuroimaging studies have demonstrated that the activity of reward systems in the brain, particularly of ventral dopaminergic systems, depends upon both reward magnitude and reward expectation.

  We investigated, using functional magnetic resonance imaging (fMRI), how risk context influences the brain response to decisions involving rewards. Participants selected among virtual slot machines with different payoff schedules and played the selected machine for a block of trials. Three machines were used: the first high-was risk/high-reward, the second was low-risk/low-reward, and the third gave no reward (perceptual/motor control). We evaluated whether risk context had an effect on brain activation when 1) subjects chose what machine to play on a given block, and 2) subjects received a large or small reward.

  View Poster (PDF)

• Differential effects of ambiguity and risk upon brain systems for decision making
  Brent T. Warner¹, Evan M. Gordon¹, C. Jill Stowe⁴, Michael L. Platt³, and Scott A. Huettel^{1,2
  1}Brain Imaging and Analysis Center; Departments of ²Psychiatry and ³Neurobiology, Duke University Medical Center; ⁴Fuqua School of Business, Duke University

  Many decisions are made under limited information about potential outcomes. When two or more outcomes are possible, with knowable probabilities, decisions are made under risk. Conversely, decisions made with limited knowledge of outcome probabilities are made under ambiguity. The distinction between risk and ambiguity has been long debated within the economics literature (see Knight, 1921). In the current study, we investigated using functional magnetic resonance imaging (fMRI) whether risk and ambiguity evoke distinct patterns of neural activity during decision making.

  Subjects participated in two sessions (one behavioral and one fMRI) of choices between pairs of monetary gambles. Each gamble showed one or more probabilistic rewards (displayed as a pie chart or “spinner”). Three gamble types were used: Ambiguous, Certain, and Risky. These gambles could be arranged in four possible pairings: Risky/Certain (RC), Risky/Risky (RR), Ambiguous/Certain (AC), or Ambiguous/Risky (AR).

  View Poster (PDF)