Figure 4

fMRI results related to expected reward uncertainty: orbitofrontal cortex. Significant (p < 0.05 FDR corrected) medial and left lateral orbitofrontal involvment as revealed by the repeated measures ANOVA 2 over the expectation phase with eight conditions (a: 25%-120¢, b: 25%-60¢, c: 50%-60¢, d: 50%-30¢, e: 75%-40¢, f: 75%-20¢, g: 100%-30¢, h: 100%-15¢) set up to model effects of reward uncertainty. Signal time courses in both regions are depicted in the right panel. Mean-corrected fMRI signal time courses (1^st eigenvariate of the fMRI signal intensity as provided by standard SPM functions and standard errors) were extracted from the two significant orbitofrontal ROIs for each subject and were averaged event-related to depict the fMRI signal. Grey shades indicate the period when reward expectation took place relative to the delayed MR signal. The fMRI signal peaks around scan 3 after onset of the trial (scan 1) with significantly (p < 0.005) higher values for scan 3 than for scan 7 in all eight conditions. Differences in signal time courses (50%, highest uncertainty and 100%, lowest uncertainty) increased from scan 1 to 5 over the course of reward expectation.