On Fri, 23 Apr 1999 [EMAIL PROTECTED] went:
> This term came up in class during memory unit. Student claims it is a
> term for a temporary loss of ability to recall, without any apparent
> physical damage. Help!
He's right. It is. If I (heh) recall correctly, transient global
amnesia is usually anterograde more than retrograde (i.e. you can
still remember your remote past, but you can't consolidate new
information). The condition may persist for hours or days; then it
goes away, and it doesn't seem to presage any further trouble. Last
time I checked the literature (more than two years ago), there were
some PET or SPECT studies showing temporary reductions in blood flow
to some areas of the brain during transient global amnesia--which may
explain why the student incorrectly abbreviated it TIA (that's a
"transient ischemic attack," and only a small subset of TIAs would be
accompanied by TGA).
Self-indulgent anecdote: One afternoon, about 18 months ago, I was
driving down a very familiar stretch of road near my home. Suddenly I
couldn't remember where I was. I knew it was a familiar place, but I
didn't know _which_ familar place; I didn't know which of my mental
"maps" I needed to refer to. Was I one mile from home, or was I
thirty miles from home? (I was one mile from home.) This lasted
perhaps 15 or 30 seconds (it felt much longer) and fortunately abated
when I reached a streetlight. I tentatively attribute it either to a
cerebral-blood-flow glitch as described above, or to a one-time-only
seizurelike event. It was, subjectively, quite a dramatic experience.
--David Epstein
[EMAIL PROTECTED]
