Brain pathways tended to be more asymmetric at older ages
A cross-sectional analysis of 35,120 people aged 0 to 100 found that left–right differences varied by brain pathway and structural measure.
Cohort study
Limit: Each person contributed only one scan, preventing measurement of within-person changes in asymmetry
Edited by Boris Djordjevic · AgingResearch.News
Researchers analyzed brain scans from 35,120 typically developing and aging people aged 0 to 100 years in a cross-sectional observational study. The sample was 53.7% female and came from 50 population-based cohorts. The team charted six measures of tissue organization, volume and length across 30 paired white matter pathways—the bundles of nerve fibers connecting brain regions.
Left–right differences appeared in all 30 pathways. Their size and direction depended on both the pathway and the feature measured. Different features of the same pathway could favor opposite sides. The age-based charts showed distinct developmental patterns and a general trend toward greater asymmetry at older ages, particularly in later adulthood. Some pathways and measures instead showed greater symmetry at older ages.
Why it matters
For research on brain aging, the authors present the charts as a reference for interpreting departures from typical white matter organization, including those associated with clinical conditions.
Caveats
Each person contributed only one scan, so these cross-sectional comparisons could not show changes within individuals. The analysis excluded people with a pathological diagnosis and did not examine cognitive or behavioral measures.
The paper
Lifespan Trajectories of Asymmetry in White Matter Tracts
Vanderbilt University
Human Brain Mapping, Jun 1, 2026, Open access
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