Knowing almost nothing about memory and the brain, I don't know if I agree with "Every memory your brain has ever produced is still there".
Memories seem to be constructed by a group of neurons together, and it seems clear that neurodegeneration is a thing, whether by trauma or due to aging. When pathways degenerate, maybe you have a partial memory that you brain can help fill the gaps with(and often incorrectly), but that does not make it the original memory.
Memories seem to be constructed by a group of neurons together, and it seems clear that neurodegeneration is a thing, whether by trauma or due to aging. When pathways degenerate, maybe you have a partial memory that you brain can help fill the gaps with(and often incorrectly), but that does not make it the original memory.