Neural Reward Imbalance Between Social Incentives and Circumscribed Interests in Autism Spectrum Disorder

Background: Neurobiological research in autism spectrum disorders (ASD) has largely focused on the social impairments, with restricted and repetitive behaviors and interests (RRBIs) being much less well studied, particularly with regard to functional neuroimaging. A common notion in the field suggests that the two core symptom clusters share a modest neurobiological overlap. In fact, accumulating evidence indicates an imbalance in the brain’s reward system reactivity may contribute to both social deficits and RRBIs (Kohls, Yerys, Schultz 2014, Biol Psychiatry).

Objectives: This study’s central aim was to determine if preoccupying special interests engage the brain’s reward system in a fashion comparable to other incentives (e.g., social reward such as approval), and to compare brain responsivity to these different incentives in youth with ASD vs. typically developing control (TDC) children.

Methods: We conducted a 3T functional magnetic resonance imaging (fMRI) study to investigate the blood-oxygenation-level-dependent (BOLD) effect of social reward vs. personalized interest rewards (based on self-report) in 35 children with ASD relative to 19 TDC. To probe the reward system we used short video clips of actors providing social approval (social reward condition) and movies reflecting personal special interests (interest condition) as incentive stimuli, i.e., rewards. This optimization increases the task’s ecologically validity compared to still pictures that are often used in this literature.   

Results: There were no group differences with regard to type and number of individual interests, but children with ASD were rated to pursue their interests with greater intensity (according to parent report on the Interest Scale: Cohen’s d=1.42). Behavioral task performance on the incentive delay task was similar in both groups with faster responses and better accuracy under reward conditions vs. non-reward. As predicted, however, the imaging data revealed greater reward circuitry activation in children with ASD vs. TDC in response to individual interest rewards. Significant group differences were found in the ventral and dorsal striatum, thalamus, precuneus, dACC, OFC and insula (whole-brain cluster-corrected at p=<0.05). dACC activity was correlated with ASD symptom severity (ADOS: r=0.39, p=0.023). By contrast, amygdala activation was diminished in ASD vs. TDC in response to social reward as revealed by ROI analyses.       

Conclusions: The current data corroborate and extend prior findings that the brain’s reward circuitry in ASD, particularly frontostriatal areas, selectively overreacts to RRBIs like restricted interests, whereas it underreacts to social rewards. Because ASD may be rooted in the powerful reward circuitries that shape a great deal of behavior, strategically targeting the role of reward mechanisms promises to improve current treatment practices for individuals with ASD and their families.