In his book, The Man Who Mistook His Wife for a Hat, Oliver Sacks tells the story of Jimmie, a former sailor, now a patient in a nursing home, whose severe neurological disorder had left him with a profound and permanent amnesia. He simply had no memory of anything from 1945 on. Having no ability to retrieve the past and no ability to construct a meaningful present, Jimmie lacked the continuity that makes for a sense of the self. He was, wrote Sacks, a person who "wore a look of infinite sadness and resignati…