Local and Global Visual Processing in Autism: A Systematic Review and Meta-Analysis of Neuroimaging Studies

Autism Spectrum Condition (ASC) is linked to altered local and global visual processing. Previous meta-analyses demonstrated brain activation differences across a broad range of visual tasks in ASC compared to non-autistic individuals, suggesting alterations in visual processing. However, a more specific understanding of brain mechanisms underlying detail-oriented visual attention is still lacking. To address this question, we conducted a systematic review and an activation likelihood estimation (ALE) meta-analysis on brain imaging studies assessing 252 individuals with ASC and 263 neurotypical controls (CON).

We included tasks that either required focusing on details while ignoring global configurations (local visual processing) or vice versa (global visual processing). Using ALE, we performed between-group and within-group meta-analyses across 15 studies involving local and global visual tasks.

We found greater activation in the right inferior occipital gyrus (Brodmann Area, BA 19) in ASC compared to CON in the between-group meta-analysis of local and global visual studies. In the within-group analysis, we identified two activation convergences in the thalamus and middle occipital gyrus (BA 19) in the ASC group, and one in the inferior parietal lobule (BA 40) in the CON group.

In line with theories suggesting alterations in local and global visual processing in ASC, our results indicate that autistic individuals may rely more on the visual cortex for local/global visual processing, while non-autistic controls may rely more on parietal regions.