Proportion of WM subtype in the main fasciculi.

<p>Proportion of WM subtype in the main fasciculi.</p

Age and gender effect on MPF, R₁, and ADC.

<p><b>a.</b> Upper left graph: Age effect on MPF. All subtypes showed a similar decrease with aging (F(1,22) = 10.6, p = 4 10⁻³, no interaction). <b>b.</b> Lower left graph: Age effect on R₁. Whereas R₁ decreased with aging in f-WM as for MPF, it increased in t-WM and c-WM (f-WM vs. t-WM: F(1,22) = 16.6, p = 5.0 10⁻⁴; f-WM vs. c-WM: F(1,22) = 15.9, p = 6.2 10⁻⁴). There was a differential effect of aging on MPF and R1 in t-WM and c-WM only. <b>c.</b> Right graph: Gender effect on ADC. Gender had a selective effect on t-WM with females having larger ADC than males, whereas it had virtually no effect on f-WM and c-WM (t-WM vs. f-WM: F(1,23) = 5.7, p = 0.025; t-WM vs. c-WM: F(1,23) = 2.3, ns).</p

Spatial distribution of the average t-WM (red), f-WM (blue) and c-WM (green).

<p>Positive components are displayed on the average MPF map (not smoothed). z ≥ 2, k ≥ 200 vx (1.6 cm³). t-WM encompassed deep WM regions of well-structured tracts: the corpus callosum, the extreme, external and internal capsules, the corona radiata, the cerebellar peduncles (superior, middle and inferior), the pons and the mesencephalon. f-WM and c-WM mainly corresponded to subcortical WM regions: the centrum semiovale including U-fibers in some places. f-WM was mostly frontal while c-WM was essentially central corresponding to the cortico-bulbar and cortico-spinal tracts.</p

Parameter values of WM subtypes.

<p>Parameter values of WM subtypes.</p

Contribution of the different parameters in separating the subtypes.

<p>For each pairs of subtypes, the bars represent the distance between the subtypes expressed in the cumulative sums of Cohen’s d. The contribution of each parameter is shown in different color. t-WM showed the largest absolute difference with f- and c-WM essentially because of large differences in the AD parameter. However, it was virtually of no value to separate f-WM from c-WM. MPF was also a substantial contributor to subtyping, especially between f-WM from c-WM.</p