Memories in Early Alzheimer’s May Not Be Irretrievable After All

Alzheimer’s disease leads to tragic memory deficits, but it’s not clear whether those memories are actually lost. It’s also not clear whether this is a problem with memory formation and storage or a problem in memory retrieval. This is clinically relevant, since memory retrieval could potentially be restored by targeted brain stimulation.

Source: Memories in early Alzheimer’s may not be irretrievable after all

I am curious about the difference between whether the memory is actually being stored and not able to be retrieved later, or not being stored to begin with at all.  It never occurred to me to think about such a nuance.