Longitudinal Changes of the White Matter Microstructural Properties of Autism Spectrum Disorder: A Normative Model Analysis.
White-matter tracts in ASD deviate increasingly from normative development over ~5 years, especially in callosal and motor-language pathways.
01Research in Context
What this study did
Chien et al. (2026) tracked white-matter growth in autistic young adults for about five years. They used a normative model to see how far each tract drifted from typical development.
The team looked at callosal and motor-language pathways. They asked whether early symptom severity predicts how much the wiring changes later.
What they found
Autistic brains moved further away from typical white-matter curves over time. The gap widened instead of closing.
Tracts that link the two hemispheres and those that move speech and motor signals showed the largest drift. Kids who started with more severe traits had the biggest changes.
How this fits with other research
Capio et al. (2013) first showed that white-matter maturation stalls in childhood ASD. Yi-Ling extends that story by showing the stall turns into a growing gap in young adulthood.
Roine et al. (2013) found higher white-matter organization in adults with Asperger syndrome. That seems opposite to the mixed drift seen here, but their sample was older and higher functioning. Different slices of the spectrum can show different directions.
Fitzgerald et al. (2019) gave a one-time snapshot of widespread white-matter disruption. Yi-Ling now shows how that disruption unfolds year by year, giving the field its first growth-curve view.
Why it matters
If white-matter deviation keeps widening, early wiring differences are not just delays—they are ongoing. This tells you to keep teaching social and language skills across the lifespan, not just in early childhood. When you see a teen lose previously mastered conversation turns, the neural roadmap may still be shifting. Build extra practice and visual supports into middle-school and high-school plans, and track progress more often than yearly.
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02At a glance
03Original abstract
Cross-sectional research documents atypical age-related development of white matter in autism spectrum disorder (ASD). However, little is known about the developmental changes in white matter microstructural properties in ASD. This study aims to investigate developmental changes in white matter tract microstructural properties in ASD using a longitudinal follow-up design and normative model analysis, and to examine clinical correlates of these changes. We assessed 75 autistic individuals (aged 15.3 ± 4.2 years) with diffusion spectrum imaging at baseline and 4.7 ± 1.9 years later. To measure the magnitude of deviation from the norm, we calculated z-scores for fractional anisotropy (FA), axial diffusivity (AD), radial diffusivity (RD), and mean diffusivity (MD) for each of 76 tracts based on a norm established in 680 typically developing individuals. Callosal fibers connecting the temporal poles, hippocampus, and amygdala in ASD individuals showed higher AD, RD, and MD at both time points. Several tracts showed significantly greater increases in FA z-scores from baseline to follow-up, including the right superior longitudinal fasciculus, precentral thalamic radiation, frontal aslant tract, right corticospinal tracts, left arcuate fasciculus, callosal fibers connecting genu, and bilateral thalamic radiation, implying a pattern of greater deviation from the norm at Time 2 than Time 1. Higher autistic severity or social deficits at baseline were related to greater increasing rates in the diffusion metrics of callosal fibers connecting the precuneus (AD, RD, and MD), corticospinal tract (AD), right geniculate fibers (AD and MD), and right medial lemniscus (AD and MD) from baseline to follow-up. Using the normative model method to analyze longitudinal data on white matter microstructures, our findings support persistent alterations in callosal fibers and developmental alterations of several tracts in ASD, which were associated with baseline autistic severity.
Autism research : official journal of the International Society for Autism Research, 2026 · doi:10.1002/aur.70174