The Alexithymia Hypothesis of Autism Revisited: Alexithymia Modulates Social Brain Activity During Facial Affect Recognition in Autistic Adults.

Background: Autism Spectrum Disorder (ASD) and alexithymia are both linked to difficulties in facial affect recognition (FAR) alongside differences in social brain activity. According to the Alexithymia Hypothesis, difficulties in emotion processing in ASD can be attributed to increased levels of co-occurring alexithymia. Despite substantial evidence supporting the hypothesis at the behavioral level, the effects of co-occurring alexithymia on brain function during FAR remain unexplored.

Methods: Data from 120 participants (60 ASD, 60 controls) who completed an FAR task were analyzed using functional magnetic resonance imaging and behavioral measures. The task included both explicit and implicit measures of FAR. Autistic participants were further categorized based on their alexithymia status. Group differences in FAR performance and associated brain activation were investigated.

Results: Autistic participants showed lower FAR performance compared to controls, regardless of alexithymia status. Imaging revealed three cortical clusters with reduced activation in alexithymic compared to non-alexithymic ASD participants during explicit FAR, including the left inferior parietal gyrus, cuneus, and middle temporal gyrus. During implicit FAR, alexithymic ASD participants showed three cortical clusters of increased activation, including the left precentral gyrus, right precuneus, and temporoparietal junction.

Discussion: Our study shows an unexpected dissociation between behavior and brain response: While ASD affects FAR performance, only co-occurring alexithymia modulates corresponding social brain activations. Though not supporting the Alexithymia Hypothesis on the behavioral level, the study highlights the complex relationship between ASD and co-occurring alexithymia, emphasizing the significance of co-occurring conditions in understanding emotion processing in ASD.