Figure 4. Associations between amyloid burden and parahippocampal white matter integrity are independent of hippocampus volume.

Plots shows within-person trajectories of change for hippocampal volume (A) and average estimates of annual decline for individuals with (Aβ+) and without (Aβ−) measurable amyloid burden (B). The effect of amyloid burden at baseline on FA decline in the parahippocampal cingulum bundle, independent of hippocampal atrophy, is shown in C. Significant increases for Aβ+ versus Aβ− are observed for radial diffusivity (solid lines) but not axial diffusivity (dashed lines). For illustration purposes, hippocampal atrophy was re-coded as low atrophy (Hip−, i.e. larger hippocampi) and high atrophy (Hip+, i.e. smaller hippocampi) by median split. Radial and axial diffusivity were z-transformed. Beta estimates from linear mixed models are shown for graphs B-D.