Compensatory Neural Mechanisms in Unaffected Siblings of Those with Autism: An fMRI Study

Abstract

Recent studies of siblings of those with Autism Spectrum Disorder (ASD) have led to the emergence of a compensatory mechanism hypothesis wherein siblings, while showing no behavioral abnormalities, exhibit minor hypo-activations in brain areas implicated in ASD while simultaneously showing hyper-activations in other brain areas compensating for the lowered activity. We explore this theory by using functional magnetic resonance imaging (fMRI) to evaluate brain activity during a Theory of Mind (ToM) task in 18 subjects. To date, this is the first known study to investigate ToM with unaffected siblings using fMRI. Compared to age-matched controls, siblings exhibited lower activation in the lingual gyri and a trend towards higher activation in the right superior temporal sulcus (STS). This suggests that for unaffected siblings, the STS may be recruited to compensate for potential deficits in the lingual gyri during the processing of complex social stimuli.