I felt sure this would be Oliver Sacks' piece on Clive Wearing in the New Yorker. Wearing's story is perhaps more poignant, and told well by Dr. Sacks, both in the New Yorker and in his book Musicophilia, which I wrote about a while back.
......Desperate to hold on to something, to gain some purchase, Clive started to keep a journal, first on scraps of paper, then in a notebook. But his journal entries consisted, essentially, of the statements “I am awake” or “I am conscious,” entered again and again every few minutes. He would write: “2:10 P.M: This time properly awake. . . . 2:14 P.M: this time finally awake. . . . 2:35 P.M: this time completely awake,” along with negations of these statements: “At 9:40 P.M. I awoke for the first time, despite my previous claims.” This in turn was crossed out, followed by “I was fully conscious at 10:35 P.M., and awake for the first time in many, many weeks.” This in turn was cancelled out by the next entry.