Striatal predicted outcome and prediction error activity. Gain learning is depicted on the left and loss learning on the right. The SPM images and contrast estimates show the significant striatal interaction effects (P<0.05 FWE corrected) comparing Parkinson's disease (PD) patients with problem gambling or shopping (DD) and PD controls on and off dopamine agonists (DA) (repeated measures ANOVA). (A) Gain predicted outcome (top) and positive prediction error (bottom). (B) Loss predicted outcome (top) and negative prediction error (bottom). (C) Ventral striatal prediction error activity. The bar graphs show the area under the curve (AUC) of the fitted event time course ROI analysis focusing on bilateral ventral striatal (VS) activity (repeated measures ANOVA). The left graph shows a significant group by medication interaction effect of bilateral ventral striatum for positive prediction error during gain learning. The right graph shows a significant medication effect of bilateral ventral striatum for negative prediction error during loss learning. The SPM images are shown at P<0.005 uncorrected. The error bars represent standard deviation. See also Tables S4, S5 and S6.

Learning task. (A) Subjects chose between probabilistic stimulus-pairs from three conditions: gain, loss and neutral. One stimulus-pair was associated with an 80:20 probability of either gaining, losing or “looking at” $10:$0 respectively with the opposite contingency in the other stimulus-pair. (B) Behavioral outcomes for model parameters. The learning rate (α) and temperature or choice randomness (β) are represented for gain and loss conditions. Higher α and β scores represent faster learning and greater temperature respectively. Parkinson disease (PD) patients with problem gambling or compulsive shopping (DD) and PD controls are represented on and off dopamine agonists. Error bars represent standard error of the mean. (*p<0.05 for mixed measures ANOVA group by medication interaction effects). (NV = Age- and gender-matched normal volunteers) (C) Learning curve. The learning curve plots indicate actual behavioral choices during gain and loss conditions. See also Tables S1, S2 and S3.

Negative prediction error activity during loss learning in Parkinson's disease controls and normal volunteers. The SPM images and bar graphs show the comparison of Parkinson's disease controls without gambling or shopping behaviors on dopamine agonists compared to normal volunteers (t-test, P<0.05 FDR corrected). The left shows the right orbitofrontal cortex and the right shows the right anterior insula. The SPM images are shown at P<0.005 uncorrected. Error bars represent standard deviation. See also Table S7.