I think I would argue that its neither technically. The neural degeneration of prototypic AD begins in the mediotemporal lobes, as well a certain frontal regions (mostly those associated with encoding, consolidation, and working memory). However, medial temporal lobe regions and structures such as the hippocampus and the entorhinal cortex tend to be most affected early on, and often have their input connections to the rest of the association areas of the neocorticies disturbed. Hence the massive memory impairment early in the course of the illness.
After this rather predictable and common pattern, the degeneration becomes more sparse and more variable but often progresses into the posterior and inferior temporal lobe regions. As the disease progresses, diffuse cortical atrophy and ventricular enlargement begin. The anterior parietal regions and occipital cortices tend to be relatively preserved well into the course of the illness as far as I know. However, there is a AD variant (which I am not very familiar with) that presents with extreme visuospatial disturbances with the initial degeneration taking place in the occipital lobe and the ventral stream and inferior sections of the temporal lobe. To my knowledge, this is relatively rare however.
