Brain response during anticipation of incentive stimuli was probed using a modified MID task (Knutson et al., 2000; Figure 1). Each 6-second trial consisted of four events: incentive cues (five conditions: $0.20 win, $5 win, $0.20 loss, $5 loss, $0 no change); anticipation delay; variable duration target requiring a button press response to gain, or avoid loss, of money; feedback. Subjects were instructed to respond to neutral targets despite no incentive value. Trials were presented in pseudorandom order in two 5-minute runs of twenty trials/condition. Response target duration was calculated based on individual subject’s reaction time during a practice session prior to scanning and calibrated for overall success rate of approximately 60%. Participants were paid fixed participation rates plus additional money won during task.
