Associations among dopamine (DA), depression, and the Effort-Expenditure for Rewards Task. (A) Amphetamine increases the percentage of high effort choices (Wardle, Treadway, Mayo, Zald, & de Wit, 2011). PL = Placebo. Error bars represent the standard deviation. *p < .05. (B) Positron emission tomography imaging shows that individual differences in the percentage of high effort choices are positively associated with the magnitude of amphetamine-induced DA release in striatum and are (C) negatively associated with DA release in the insula (Treadway, Buckholtz, et al., 2012). (D) Patients with major depressive disorder (MDD) chose fewer high effort choices than matched controls (Treadway, Bossaller, Shelton, & Zald, 2012). Error bars represent the standard error of the mean. *p < .05.