Table 2.

WM microstructure results.

WM	Parameter	Description	Value ± SE	F(1, 419)	P
MD	β 1	Slope	(6.21 ± 1.77) × 10−6	12.29	5.03 × 10−4
	β 2	Improvement phase 1	(−9.54 ± 4.05) × 10−6	5.54	0.02
	β 4	Improvement phase 2	(−21.70 ± 8.79) × 10−6	6.10	0.01
AD	β 1	Slope	(6.63 ± 1.35) × 10−6	8.00	0.01
	β 2	Improvement phase 1	(−1.07 ± 0.52) × 10−5	4.19	0.04
	β 4	Improvement phase 2	(−2.34 ± 1.14) × 10−5	4.15	0.04
RD	β 1	Slope	(5.96 ± 1.56) × 10−6	14.63	1.51 × 10−4
	β 2	Improvement phase 1	(−8.92 ± 3.61) × 10−6	6.09	0.01
	β 4	Improvement phase 2	(−2.11 ± 0.78) × 10−5	7.43	0.01
FA	β 1	Slope	(−2.09 ± 0.79) × 10−3	6.97	0.01
	β 2	Improvement phase 1	(3.40 ± 1.94) × 10−3	3.07	0.08
	β 4	Improvement phase 2	(7.55 ± 3.75) × 10−3	4.06	0.05

Results of the nonlinear mixed effects model for each white matter metric in the full skeleton. The 2 improvement phases were estimated to begin during each training period. β₂ represents the degree of improvement relative to the slope in improvement phase 1. β₄ represents the degree of improvement relative to the slope in improvement phase 2. MD = mean diffusivity; AD = axial diffusivity; RD = radial diffusivity; FA = fractional anisotropy.