Fig. 4: Effect of mild TBI on ex vivo dMRI and axon morphology in ipsilateral major white matter tracts of male rat.

a Representative colored fractional anisotropy (FA) maps in sagittal and coronal views, with the cingulum (Cg), splenium of the corpus callosum (Scc), and body of the corpus callosum (Bcc) annotated. b Experimental axial DTI diffusivity D(t) plotted as a function of t and \(1/\sqrt{t}\), showing a power-law relation in all ipsilateral white matter regions of interest (ROIs). c Diffusion parameters D_∞ and c_D extracted by linear regression of D(t) with respect to \(1/\sqrt{t}\) in (b) for voxels within the ipsilateral Scc ROI (N_voxel = 245 per group). The optimal SVM-based linear combination z_D of the diffusion parameters is derived by projecting the points onto the dark blue dashed line perpendicular to the corresponding SVM hyperplane. d Corresponding geometric parameters 〈1/α〉 and Γ₀, computed by inverting Eqs. (2)-(3) from the diffusion parameters in (c), plotted for voxels in Scc. The optimal linear combination z_G of the morphological parameters is obtained by projecting the data points onto the dark blue dashed line, which is orthogonal to the SVM hyperplane. In (b), filled triangles with shaded areas indicate the mean and standard deviation across the ROI (N = 2 sham-operated and N = 3 TBI). In (c)-(d), each point represents a voxel. Filled circles with error bars indicate the mean and standard deviation across the ROI. Dashed vertical lines overlaid on the distributions denote their medians. Source data are provided in the Source Data file.