Severely impaired memory deprives amnesics of a
sense of personal continuity in their daily lives, yet
there are no tests that accurately measure this impairment
(see Lezak, 1995). Several neuropsychological tasks have
been developed to document the severity of memory loss
in terms of memory span, such as the Brown–Peterson
Technique (Peterson & Peterson, 1959), but the ecological
validity of such tasks as measures of personal or temporal
continuity is not obvious (see Heinrichs, 1990). Instead
they measure memory in terms of how much information could
be held in working or short-term memory, not memory span
in the sense of continuity. To develop a new measure of
amnesia with greater relation to everyday function, we
had to examine the integrity of memory function in terms
of temporal continuity in a way that would engage the patient
in everyday behavior, such as informal conversation, and
still allow memory function to be quantifiable. Thus, we
set out to create a bedside task that could measure the
span in which the patient with amnesia experiences temporal
continuity. We call this measure the “span of temporal
continuity,” or “personal and present span
of existence.”