If you're familiar with the concept of running a diagnostic routine on a piece of software - for years I've run a self-diagnostic. I recite a litany of doggerel with a few formulas. I can do it internally (fully silent) or aloud in front of a mirror. Well, after doing this for a number of years, I experienced substantially mental fuzziness and I could not get through the recital. Went to Emergency. Whatever it was was temporary and have had no recurrence. I was impressed by the rapidity with which they accepted my reason for being there.