It may act as an ancillary factor, but by itself, the mutation in tau doesn't give you Alzheimer's disease. This is not to say the tau is not very important. It may be important in propagating the disorder from one cell to another. But as a causal mechanism, the evidence is strongest for beta amyloid abnormalities.

The brain is a complex biological organ possessing immense computational capability: it constructs our sensory experience, regulates our thoughts and emotions, and controls our actions.

If you have a lesion in the hippocampus in both sides, you have short term memory, but you can convert that short term memory into long term memory.

Eric Kandel Quotes