The fog of Alzheimer’s is a commonly used metaphor, and I think it’s a pretty good one. It refers to the loss of mental acuity, disorientation, and forgetfulness that are common in Alzheimer’s. But one aspect of the metaphor that is not emphasized is that like the fog bank on the ocean, the fog of Alzheimer’s can come and go. It does for me. Sometimes there is an obvious cause such as running a fever, getting too tired, or having a second glass of wine. On the day after I got my second Covid-19 vaccination I was not mentally sharp and had trouble concentrating despite not having any other side effects. Once or twice a week on first awakening in the morning, I think I am in my childhood bedroom. It only takes a few seconds to get reoriented, and it actually is a pleasant rather than scary experience. Sometimes the fog comes in for no apparent reason, lasts a few minutes or a few hours, and then goes away. I wonder what is behind these mysterious, seemingly unprovoked but temporary episodes of cognitive impairment.