Disorder-Specific and Shared Reward Circuitry Dysfunction in Children with ASD Versus ADHD

Background: Although attention deficit hyperactivity disorders (ADHD) and autism spectrum disorders (ASD) share certain behavioral, cognitive and neurobiological characteristics, it has been hypothesized to differentiate both disorders based on their brain’s reward responsiveness to either social or monetary reward. 

Objectives: Thus, the goal of this fMRI study was to differentiate ADHD from ASD on the basis of their brain's reward system reactivity in response to these two types of reward, with greatest differences to be expected for social rewards.

Methods: We investigated the blood-oxygenation-level-dependent (BOLD) effect of both reward types in the context of an incentive go/no-go paradigm in age and IQ-matched boys with ADHD (N=16) versus boys with ASD (N=15) relative to typically developing male controls (TDC, N=17) between the ages of 9 to 18 years.  

Results: Task performance and subjective motivation ratings were comparable across all three groups. However, at the neural level a significant group by reward type interaction effect emerged in the ventral striatum with greater activation to monetary versus social reward only in TDC, whereas subjects with ADHD responded equally strong to both reward types, and subjects with ASD showed low striatal reactivity across both reward conditions. Moreover, disorder-specific and shared neural abnormalities during reward processing were revealed, including (a) striatal hypoactivation in response to monetary reward in ASD relative to TDC and ADHD, (b) orbitofrontal hyperactivation in response to social reward in ADHD relative to TDC and ASD, and (c) fronto-striato-parietal hypoactivation in both clinical groups relative to TDC when money was at stake. Interestingly, lower neural reactivity within the fronto-striato-parietal circuitry was associated with higher autistic traits across the entire sample.  

Conclusions: In sum, ASD and ADHD are neuropsychiatric disorders with distinct and shared neural dysfunction in response to reward.