Table 1.

Conduction speed models as function of age and DTI indices in the different bundles

Bundles spatial locationFractional anisotropyTransverse diffusivity
Model fitCovariate: ageCovariate: FAModel fitCovariate: ageCovariate: λ⊥
Optic radiationsaR2 = 0.85F = 14.9F = 8.2R2 = 0.86F = 6.3F = 9.7
p = 0.002p = 0.014p = 0.028p = 0.009
Corpus callosumR2 = 0.75F = 23.8F = 0.3R2 = 0.75F = 12.8F = 0.1
p < 0.001NSp = 0.004NS
Spinothalamic tractR2 = 0.75F = 16.9F = 0.1R2 = 0.75F = 18.8F = 0.0
p = 0.001NSp = 0.001NS
Corticospinal tractR2 = 0.75F = 11.4F = 0.2R2 = 0.76F = 12.5F = 1.0
p = 0.005NSp = 0.004NS
Anterior limb of the internal capsuleR2 = 0.84F = 25.1F = 7.1R2 = 0.77F = 17.7F = 1.1
p < 0.001p = 0.020p = 0.001NS
External capsuleR2 = 0.82F = 46.5F = 5.4R2 = 0.75F = 20.5F = 0.4
p < 0.001p = 0.038p = 0.001NS
Arcuate fasciculusR2 = 0.75F = 35.6F = 0.2R2 = 0.75F = 33.0F = 0.4
p < 0.001NSp < 0.001NS
Inferior longitudinal fasciculusR2 = 0.77F = 38.9F = 1.0R2 = 0.76F = 37.3F = 0.8
p < 0.001NSp < 0.001NS
Uncinate fasciculusR2 = 0.78F = 25.6F = 2.2R2 = 0.76F = 15.0F = 0.7
p < 0.001NSp = 0.002NS
CingulumR2 = 0.75F = 26.5F = 0.2R2 = 0.76F = 23.2F = 0.6
p < 0.001NSp < 0.001NS
FornixR2 = 0.77F = 16.2F = 1.5R2 = 0.76F = 14.2F = 0.9
p = 0.002NSp = 0.003NS
• The bundle spatial location for DTI quantification, the percentage of variance explained by the model (R2), and the statistical significance (F and p values; NS, not significant at the level of p < 0.05) for both covariates (age and DTI index, FA/λ) are outlined. The highest R2 values were measured for the models with FA and λ in the optic radiations.

• aFor the model of speed as a function of age and longitudinal diffusivity in the optic radiations: R2 = 0.77; age, F = 10.6; p = 0.007; λ//, F = 1.2; NS.