Cognitive variability links to white matter tracts in older adults
In 510 older adults, higher performance variability tracked lower anisotropy in specific tracts, with an effect size of 0.09 across 7.57% of whole-brain tract volume.
Neuropsychology
Participants were 510 community-dwelling older adults from the Health and Aging Brain Study-Health Disparities cohort, with an average age of 66.6 years. Researchers evaluated cognitive intraindividual variability across a multidomain neuropsychological battery by calculating the standard deviation of demographically normed performance scores. They then used diffusion MRI connectometry to identify associations between this variability and white matter quantitative anisotropy, adjusting for sex and intracranial volume.
Higher cognitive variability associated with lower quantitative anisotropy primarily in commissural corpus callosum, fronto-subcortical, and interhemispheric long-range connection fibers. Tracts of the forceps minor were the most robust to sensitivity analyses. The associations were spatially specific, accounting for 7.57% of total whole-brain tract volume.
Why it matters
Cognitive intraindividual variability serves as a sensitive marker of neurocognitive aging. Mapping these performance fluctuations onto specific white matter pathways helps clarify the network-level structural changes that occur in the aging brain.
Caveats
The study was cross-sectional, and the authors note that longitudinal research is needed to clarify neuroanatomical pathways. In addition, the magnitude of the effects was small, corresponding to an effect size of 0.09.
The paper
University of South Alabama
Neuropsychology · 1 Oct 2026