Group differences in striatal responses to a hedonic reward task. Neural activation in the ventral striatum was assessed by blood oxygen level–dependent (BOLD) responses in the win-lose condition of a gambling task using functional magnetic resonance imaging. A, Right and left regions of interest (ROIs) (depicted here) reflect maximal activation in the groups combined, and the average percentage of BOLD signal change corresponding to the win-lose contrast across all ROI voxels (right, left, or bilateral) was used for group comparisons and correlations with behavioral end points. B, The interferon alfa treatment group (IFN) had significantly decreased activation in the right, left, and bilateral ventral striatal regions compared with the untreated control group (CTL) (P<.01 for all comparisons). The color bar ranges from t=0 to t=8, with a group activation threshold of P<.005 uncorrected and a cluster size k≥19 voxels (P<.05 corrected).