Figure 6.

Comparison of V₁ to the local radial orientation. The distance from the lateral ventricular surface was computed for each voxel in the occipital and parietal lobes (A, underlay), and displayed for the same animal as in Figures 4, 5, at a different axial plane. The 3D gradient of the distance matrix is oriented along the radial direction (A, red vectors). For the same field of view, the principal axis of the diffusion tensor for each voxel (green vectors) is overlaid on an FA map (B). An image of angle θ between the radial direction vector, and the primary eigenvector of the diffusion tensor is shown in (C). In general, θ is larger near the lateral ventricles, indicating water diffusion is least restricted in tangential directions, and it is smaller in more superficial lamina, indicating radially-oriented diffusion anisotropy. A local maximum in θ with respect to laminar position is observed near the ventricular surface (C, yellow arrow heads). Twelve radial streamlines are projected onto the same field of view in (D). Each streamline originates at the center of a voxel bordering the ventricular surface, and ends at the pial surface. A parasagittal plane intersecting (D) at the dashed line location is shown as inset to provide a view that contains ventricular and pial radial streamline endpoints.