Research on transgenic mice suggests that memories are not destroyed irretrievably by Alzheimer’s Disease; there appears to be problems recalling these lost memories. Lost memories may be retrievable, under experimental conditions, by exposing “Engram Cells” with bright blue light (in the mouse model of the disease at least).
Note: The researchers caution readers that their techniques are not suitable for humans currently, and that Alzheimer’s Disease in humans may work in a different way.
Memories ‘taken’ by Alzheimer’s could possibly be retrieved. London: NHS Choices Behind the Headlines, March 17th 2016.
This relates to:
Full Text Link (Note: This article requires a suitable Athens password, a journal subscription or payment for access).
Roy, DS. Arons, A. [and] Mitchell, TI. [et al] (2016). Memory retrieval by activating engram cells in mouse models of early Alzheimer’s disease. Nature. March 24th 2016; 531(7595): 508-12.
The following earlier article by the same team is available freely:
Tonegawa, S. Pignatelli, M. [and] Roy, DS. [et al] (2015). Memory engram storage and retrieval. Current Opinion in Neurobiology. December 2015; 35: 101-9. Review.