APP and Alzheimer disease: In AD, white matter deficits can be secondary to neuronal amyloid-β and amyloid precursor protein accumulation63 in the frontal and temporal lobes that eventually impact the associative tracts.64,65 In SZ, white mater deficits may be due to the abnormal expression of oligodendrocyte lineage genes or oligodendrocyte cellular dysfunctions.66,67 The reciprocal rise in RVI-SZ in AD and RVI-AD in SZ may reflect different underlying pathology that converges on similar white matter structures as the disorders progress.