Each volume consisted of 36 slices acquired parallel to the AC-PC plane (sequential acquisition; 3.5 mm thick with a 0.5 mm gap;

260 × 260 mm in-plane resolution, 64 × 64 matrix). The first three volumes were discarded to allow for magnetization equilibrium. A T1-weighted FSPGR structural image (TR = 7.7 msec, TE = 3.0 msec, flip angle 12°) was acquired for anatomical comparison. Cushions were placed around the participants’ head to minimize movement and earplugs and headphones were used to minimize noise. Behavioral analysis Effect of motivation on decision-making behavior Inhibitors,research,lifescience,medical Discrimination (d′) and response bias (c) were calculated using signal detection theory (Macmillan and Creelman 2009). Discrimination Inhibitors,research,lifescience,medical measures one’s ability to identify a target stimulus from a nontarget stimulus and is calculated using the inverse z-transformed hit rate (HR) and false-positive rate (FPR): A d′ score of 0 indicates an inability to discriminate GW-572016 molecular weight between stimuli. The better an individual’s discrimination, the larger the d′ score.

Response bias is calculated as: Inhibitors,research,lifescience,medical and measures a participant’s willingness to say the target stimulus is present. A response bias equal to 0 indicates that a participant is equally likely to say a target or nontarget stimulus is present. A larger positive score indicates that the participant is less likely to say the target stimulus is present (conservative bias), while a large negative score indicates an increased willingness to say the target stimulus is present Inhibitors,research,lifescience,medical (liberal bias). Given the equal proportion of target and nontarget trials and the neutral Inhibitors,research,lifescience,medical payoff matrix in this study, the mathematically optimal response bias is neutral (c = 0). Two one-way, repeated-measures ANOVAs were used to test the effect of motivation on discrimination and response bias (IBM SPSS Statistics for Windows, Version 19.0. Armonk, NY, USA: IBM Corp.). A two-way (4 × 2), repeated-measures ANOVA was used to examine the effect of motivation

and decision (Yes/No) on the natural log (ln) transformed response times (RT). Metalloexopeptidase Greenhouse–Geisser corrections were applied when the assumption of nonsphericity was broken. Significant differences were identified at P < 0.05. Effect sizes were calculated using Pearson’s r. Values of r = 0.10, 0.30, and 0.50 reflect small, medium, and large effect sizes, respectively (Cohen 1988). Where there was a significant difference in response bias between levels of motivation, the change in response bias (Δc) was calculated as: The more negative Δc, the bigger the shift toward a more liberal response bias. The more positive Δc, the bigger the shift toward a more conservative response bias.