Brain activation to reward delivery. (a) No significant whole-brain family-wise error (FWE) corrected effect of diagnosis in the right ventral striatum. (b) Effect of diagnosis in the region of interest (ROI) analysis of the left and right ventral striatum with corresponding distribution plots. (c) ROI analysis in individuals with autism spectrum disorder (ASD) and elevated attention-deficit hyperactivity disorder (ADHD) symptoms (ASD+ADHD), individuals with ASD without elevated ADHD symptoms (ASD–ADHD) and typically developing individuals without elevated ADHD symptoms. Location and size of ROI mask shown in red. *P < 0.05. Error bars reflect standard error. Whole-brain results thresholded at PFWE < 05. Distributions of ROI activation in case and control participants were compared using the Kolmogorov–Smirnov test, which suggested no evidence for unequal distributions (left ventral striatum: D(205,174) = 0.120, P = 0.134; right ventral striatum: D(205,174) = 0.112, P = 0.190). EMM, estimated marginal means.