Widespread alterations in white matter microstructure in autism: A multilevel meta-analysis

Area of Science:

• Neuroimaging
• Autism Spectrum Disorder Research
• Brain Connectivity

Background:

• Disrupted brain connectivity is a key neurobiological feature of autism spectrum disorder (ASD).
• Diffusion tensor imaging (DTI) is crucial for examining white matter microstructure in ASD.
• Previous DTI studies in ASD often report reduced fractional anisotropy (FA) and increased mean diffusivity (MD).

Purpose of the Study:

• To conduct a meta-analysis evaluating white matter microstructure alterations in ASD using FA and MD measures.
• To assess how factors like publication year, age, sex, IQ, and laterality moderate these alterations.
• To synthesize findings from numerous DTI studies on ASD.

Main Methods:

• A multivariate random-effects meta-analysis with a multilevel structure was employed.
• Included 881 effect sizes from 66 studies (N_ASD = 2231, N_TD = 1856).
• Analyzed data across 12 white matter tracts, considering participant characteristics and laterality as moderators.

Main Results:

• Significant reductions in FA (Hedges' g = -0.30 to -0.50) were found in nine white matter tracts in individuals with ASD.
• Significant increases in MD (Hedges' g = 0.29 to 0.97) were observed in eight white matter tracts in individuals with ASD.
• Moderator analyses revealed tract- and metric-specific effects on these alterations.

Conclusions:

• White matter microstructure alterations in ASD are complex and multidimensional.
• Findings underscore the heterogeneity of neurobiological differences in ASD.
• This meta-analysis provides a comprehensive overview of DTI findings in ASD white matter.