Neurophysiological correlates of relatively enhanced local visual search in autistic adolescents

TLDR

Previous research shows autistic individuals often perform as well or better on local visual search tasks such as the Embedded Figures Task, with explanations ranging from weak central coherence to amplified early perceptual processing. This study aimed to differentiate between weak central coherence and early perceptual amplification explanations for EFT performance in autistic adolescents using fMRI. Functional MRI was conducted on 12 autistic adolescents and 12 matched controls to compare brain activation patterns during the EFT. Behaviorally, autistic adolescents performed normally on the EFT but poorly on a control task with minimal local search, and fMRI revealed that while controls showed left‑lateralised parietal and premotor activation, autistic participants exhibited right primary visual cortex and bilateral extrastriate activation, indicating enhanced early visual processing rather than impaired global context processing.

Abstract

Previous studies found normal or even superior performance of autistic patients on visuospatial tasks requiring local search, like the Embedded Figures Task (EFT). A well-known interpretation of this is "weak central coherence", i.e. autistic patients may show a reduced general ability to process information in its context and may therefore have a tendency to favour local over global aspects of information processing. An alternative view is that the local processing advantage in the EFT may result from a relative amplification of early perceptual processes which boosts processing of local stimulus properties but does not affect processing of global context. This study used functional magnetic resonance imaging (fMRI) in 12 autistic adolescents (9 Asperger and 3 high-functioning autistic patients) and 12 matched controls to help distinguish, on neurophysiological grounds, between these two accounts of EFT performance in autistic patients. Behaviourally, we found autistic individuals to be unimpaired during the EFT while they were significantly worse at performing a closely matched control task with minimal local search requirements. The fMRI results showed that activations specific for the local search aspects of the EFT were left-lateralised in parietal and premotor areas for the control group (as previously demonstrated for adults), whereas for the patients these activations were found in right primary visual cortex and bilateral extrastriate areas. These results suggest that enhanced local processing in early visual areas, as opposed to impaired processing of global context, is characteristic for performance of the EFT by autistic patients.