APP and Alzheimer disease: One principal difference between the dynamics of iAβ in unconventional AD versus that in the conventional form of the disease is that, in the latter, the phase of slow accumulation of AβPP-derived iAβ changes into the phase of fast accumulation of iAβ produced independently of AβPP only with the crossing of the T1 threshold; only then can the neuronal ISR conventionally be elicited and the AβPP-independent C100/C99 generation pathway be activated.