Jeff asked:

What is memory? How important is it to my identity? Why is my short term memory getting worse as I
age? Why am I starting to remember random things from my childhood that I haven't thought about
since they happened? Along the same lines (I think), what is the current thinking on the phenomenon
of deja vu?

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An interesting set of questions. I don't really know how to answer the first one, because I don't know
in what sense you're asking it. The recall of past events and objects? But surely you're asking more
than that... you mean, what are the mechanisms of memory? That's still being researched... off the
top of my head, here's some of it. You have, say, a visual experience: you see something, and you're
paying attention to it. The first thing that happens is, maybe, due to reverberating circuits in the visual
cortex (neural discharges which regenerate themselves): you have a very clear visual impression
which lasts for a few seconds. Second, that visual impression fades and is replaced by a less clear
visualization, if you make some effort, which lasts a few minutes: that is, if I recall correctly,
"short-term" memory. Then that fades, and you have an "intermediate-term memory" which lasts for a
few hours, perhaps days, during which you can recall the object fairly clearly (usually). Then if you
paid attention, you have a "long-term" memory, lasting for days, weeks, or whatever, in which, given
some cue, like a word, etc., you can recall the object, i.e., visualize it, attach meaning to it, etc., fairly
clearly. I think that's about it... there may be another stage in there that I'm forgetting (haha).

Now, what is happeningin all that. Well as I say, the first is probably reverberating circuits. The
second probably has to do with both the reverberating circuits (which are fatiguing) and evocations
from other sensory modalities and association areas... like, red is associated with apples, which feeds
back into the fire engine you're seeing to keep it active. Or something like that. The third has to do
with establishing those associations, and also with creating a trace of some sort in the hippocampus,
which somehow, no one knows how, stores memory for a while (hours or days, maybe) while it
somehow creates (probably by creating maps to and from) long-term memories, particular neural
paths, in the visual cortex and associated areas.

Loss of short-term memory with ageing is thought to be associated with gradual damage, basically
loss of cells, in the hippocampus. This area of the brain seems to be very sensitive to damage,
Alzheimer's, etc.... why, no one knows (and I'm notsaying you have Alzheimer's... everyone has this
memory problem with age). So the hippocampus either doesn't store the short-term memories well,
and/or doesn't "write" them into the cortex well. Or both.

As for remembering things from childhood... again, no one knows. I did see an article once, quite a
while ago, in which someone had studied some computer simulations of neural nets, and found that
when the nets were saturated, i.e., when learning something new caused something old to be
partially lost, old patterns would spontaneously emerge. I'm sorry that I cannot recall anything more
about this study... it was quite a while ago that I read it, and it may have been disproved in the
interim. The other explanation advanced is merely that repetition makes similar patterns more likely to
be evoked. Both of those, as you can imagine, have problems and are incomplete as explanations. I
don't know about the current thinking on deja vu. There is work being done on "feelings of knowing"
(FOKs) by several people, and they find that FOKs are real but not very reliable.

There's lotsof literature in the area of memory, most of it pretty technical. You need some
background in neuroanatomy and neurophysiology to really get into it, so I don't know if it's worth my
giving you many references. You might just browse around the Web until you find information; lots of
labs have pages on this topic. However, if you want refs:

Ebbinghaus, H. (1913). Memory; a contribution to experimental psychology.New York, NY: Teachers
College.

Kahneman, D., & Treisman, A. (1984). Changing view of attention and automaticity.New York, NY:
Academic Press.

Hasher, L., & Zacks, R. T. (1979). 'Automatic and effortful processes in memory'. Journal of
Experimental Psychology,108 (3), 356-388.

Koriat, A. (1994). Memory's knowledge of its own knowledge: the accessibility account of the feeling
of knowing.Cambridge, MA: Bradford.

Reisberg, D. (1997). Cognition: exploring the science of the mind.New York, NY: W. W. Norton &
Company, Inc.

Wegner, D. M., & Bargh, J. A. (1996). Control and automaticity in social life.Boston, MA:
McGraw-Hill.

These are just the tip of the iceberg... not even that, really.

Steven Ravett Brown