These regions are all innervated by the basal forebrain cholinergic neurons. These neurons have direct and indirect cerebrovascular innervation (vasodilatory in nature). Cholinergic denervation may contribute to hypoperfusion in these regions. In addition, many of these regions are perfused by terminal arteries and may be at higher risk for hypoperfusion when there is coexisting vascular disease.
References: Claassen JA and Jansen RW. Cholinergically mediated augmentation of cerebral perfusion in Alzheimer's disease and related cognitive disorders: the cholinergic-vascular hypothesis. J Gerontol A Biol Sci Med Sci. 2006;61(3):267-71. Abstract