Letter to Editor Regarding: Statistical Significance versus Effect Size in Hemispheric White Matter Asymmetry

This letter comments on Khaniyev et al.'s comprehensive diffusion tensor imaging study of hemispheric asymmetry across 17 white matter tracts in 102 healthy adults. We raise three considerations. First, several reported asymmetries reach statistical significance despite negligible effect sizes (e.g., uncinate fasciculus total volume: p<0.0001, Cohen's d=0.02), reflecting how high measurement precision across many within-subject paired comparisons can render trivial differences "significant." Second, the Methods specify a q<0.01 threshold after Benjamini-Krieger-Yekutieli correction, yet the Abstract and Results report additional findings as significant at p<0.05, creating ambiguity about which threshold defines the headline conclusions. Third, deterministic tractography with randomized angular and step-size parameters carries known reconstruction-dependent variability. We suggest the authors clarify their significance criteria and consider cross-validation with an independent tractography approach to strengthen confidence that the observed asymmetries reflect true anatomy.

Diffusion tensor imaging Tractography Statistical significance