Table 2.

Genetic group means for DTI parameters

		GCC	ATR	UNC	IFO	SCC
Fractional anisotrophy	met/met	0.46 a,b	0.44 a	0.41	0.46	0.54
	met/val	0.45 a	0.46 a,b	0.43	0.48	0.57
	val/val	0.47 b	0.47 b	0.44	0.49	0.58
Axial diffusivity (μm2/ms)	met/met	1.34 a,b	1.27 a	1.23 a,b	1.29	1.51
	met/val	1.32 a	1.25 a	1.24 a	1.28	1.48
	val/val	1.28 b	1.22 b	1.2 b	1.26	1.46
Radial diffusivity (μm2/ms)	met/met	0.63 a,b	0.63 a	0.64	0.60	0.59
	met/val	0.63 a	0.60 a	0.62	0.58	0.55
	val/val	0.59 b	0.57 b	0.59	0.55	0.52

GCC = genu of the corpus callosum; ATR = anterior thalamic radiation; UNC = uncinate fasciculus; IFO = inferior frontal occipital fasciculus; SCC = splenium of the corpus callosum. Multivariate analyses of variance conducted on IFO and SCC were not significant at p < .05; consequently, follow-up tests were not conducted for these tracts. Within GCC, ATR, and UNC, for each parameter, values with different subscripts differ significantly at p < .05.