fMRI Evidence for Social Motivation Hypothesis of Autism

Autism spectrum disorder (ASD) is associated with aberrant processing of social and nonsocial rewards and potentially restricted interests, according to a functional magnetic resonance imaging (fMRI) meta-analysis published in JAMA Psychiatry.

“These results offer what we believe to be the first fMRI evidence of domain general reward processing deficits in ASD, supporting a broader interpretation of the social motivation hypothesis,” the researchers wrote.

To evaluate whether individuals with ASD process reward stimuli differently than typically developing individuals and whether or not the difference is limited to social rewards, researchers extracted and synthesized data from previous studies published in PubMed, Embase, and PsycINFO that provide brain activation contrasts between ASD samples and control samples on reward tasks. 

Their meta-analysis included 13 studies with 30 total fMRI contrasts from 259 individuals with ASD and 246 control patients. All 259 participants with ASD presented atypical reward circuitry activation to both social and nonsocial rewards, as well as increased activation to stimuli associated with their restricted interests.

A secondary analysis included meta-analyses of wanting and liking, meta-regression with age, and correlations with ASD severity. The results suggested that prior mixed results may have been caused by sample age differences, which warrant further research focusing on the developmental trajectory for reward processing in ASD.

Limitations of the study include a relatively small sample size, heterogeneity between previous study paradigms, and the unavailability of some statistical maps.

These data show that ASD may arise from an early neurobiological difference in response to rewarding social stimuli, which could result in reduced social motivation. Atypical processing of rewards, which extend to nonsocial stimuli, may also contribute to increased motivation for restricted interests, sensory interests, and other symptoms encompassed by the ASD phenotype, the researchers concluded.

Reference

Clements CC, Zoltowski AR, Yankowitz LD, et al. Evaluation of the social motivation hypothesis of autism: a systematic review and meta-analysis [published June 13, 2018]. JAMA Psychiatry. doi:10.1001/jamapsychiatry.2018.1100