Sensory Feature Representation in Autism: Insights from Naturalistic Neuroimaging

Abstract

Sensory-perceptual differences are widely reported in autism, affecting up to 90% of the population, yet the precise underlying neural mechanisms of these observed differences remain poorly characterized and understood. Neuroimaging studies hint at altered sensory cortical activation, but have had mixed findings across different brain regions and often lack theoretical grounding and ecological validity. Naturalistic stimuli, such as movies, have emerged as powerful tools that engage broad neural circuits and permit a more comprehensive mapping of sensory representations in the brain. Applying encoding models to large-scale fMRI datasets of this more ecologically valid data offers a rigorous approach to investigate perceptual differences across both individuals and broader diagnostic groups. Sensory-based theories of autism, such as enhanced perceptual functioning (EPF) and weak central coherence (WCC), posit differences in perceptual styles, such as enhanced low-level sensory processing or a local over global perceptual preference. More broadly across development, perceptual preferences have been observed as shifts in the dominance of sensory modalities. This dissertation employs naturalistic fMRI paired with encoding models to characterize brain-based sensory representations, quantifying the balance of different feature classes represented in the brain and providing a novel and nuanced framework for understanding the neural underpinnings of sensory differences in autism. The first study, Chapter 2, tested the theories of EPF and WCC by contrasting high- vs low-level feature representations during naturalistic movie viewing. This study found that encoding model-derived metrics aligned more with WCC than EPF, with results driven by differences in feature representation in key social and integration brain regions. The second study, Chapter 3, examined sensory dominance by comparing audio vs visual feature representations, and found few differences across autistic and neurotypical groups but widespread age-related effects. Together, these studies demonstrate differences in the balance of high- vs low-level sensory information represented in the brain in autism, but a generally conserved balance of features across audio and visual modalities. These results offer more context into sensory theories of autism and demonstrate the utility of naturalistic movies and encoding models in the context of neurodevelopmental conditions.