Figure 2.

(A) Task design from Stanek et al. (submitted). The task was designed to dissociate two putative Dopamine (DA) dynamics during reward anticipation—a rapid phasic response scaling with expected reward value, and a prolonged response that increases with uncertainty (following Fiorillo et al., 2003). These profiles are indicated by shaded triangles relative to trial events. Reward certainty and stimulus presentation epoch were manipulated trial-to-trial. Cues associated with 100%, 50%, or 0% reward probability were presented for 400 ms. Cue-reward relationships were learned and tested prior to task performance. Incidental encoding objects were presented either immediately following the cue (Early Epoch; 400 ms anticipation period) or shortly before the anticipated reward outcome (Late Epoch; 3000–3600 ms anticipation period). Following reward outcome, participants responded to a probe (yes/no answer; location counterbalanced) asking whether or not they had received a reward. (B) Early Epoch memory performance linearly increased with expected reward value in the 24-h retrieval group (performance 100% > 50% > 0%) but not in the immediate encoding group. (C) Late Epoch memory performance was greatest for items encoded during reward uncertainty (50% > 100% and 50% > 0%) in both the immediate and 24-h retrieval groups. Asterisks indicate significant effects (p < 0.05).