Alzheimer's starts in your hippocampus, the place responsible for forming new memories.

So, the very first symptoms of Alzheimer's will be not remembering what someone said a few minutes ago, repeating yourself over and over because you don't remember what you just said, not remembering what happened last week, even if it was meaningful. Things you would normally remember from last week won't get consolidated.

It will invade your frontal lobe, so you'll have problems with problem-solving and decision-making. It will invade parts of your brain that have to do with where things are in space, so you might get lost in your neighbourhood.

It will invade the parts of your brain that have to do with language so that you will have trouble to find the right words more and more.

The disease will then move on to your limbic system and cause changes in emotion and personality.

The accumulation of amyloid plaques takes 15 to 20 years and can be influenced by how we live.

Things that influence the amyloid plaque levels.

1. Sleep. While you sleep, the glial cells in your brain clear away all the metabolic debris and amyloid beta accumulated in your brain while you were awake.
2. Diet. A Mediterranean diet can reduce your risk of Alzheimer's by almost half.
3. Exercise. A brisk walk for 30 minutes, four to five times a week, is enough to decrease your amyloid plaque levels.
4. Chronic stress will increase your risk of developing Alzheimer's.
5. Learning something new.

Every time you learn something new, you build new synapses, neural connections, and a 'cognitive reserve.'

If someone with Alzheimer's built a lot of redundant connections,  they can dance around those roadblocks and still get to the memory they need. 

So, learning new things gives a way to build an Alzheimer-resistant brain.