CA4 and Alzheimer disease: Terminal branches of the perforant path, by contrast, fill from the outset of the pathological process the outer two-thirds of the molecular layer, but they are probably not responsible for the transmission of AD-related tau seeds, inasmuch as the involvement of the granular cells is a late event that occurs only after the development of abnormally altered axonal terminals in the inner third of the molecular layer, i.e., following the appearance of involved CA4 mossy cells.