Often, this happens when an experience evokes an unbroken joy a ray of light beaming into a warm room on a winter morning, the uninterrupted presence of someone I love next to me, and things, less concrete a memory, a song, a word.

NPR: Our Lives Are Ephemeral

The imaging agent can't be used to diagnose someone with Alzheimer's disease if the individual doesn't experience memory impairment because the presence of amyloid in the brain doesn't alone suggest that someone has Alzheimer's.

WSJ: FDA Approves Alzheimer's Test Developed by Eli Lilly