Re: Long-term memory loss in immortals

Anders Sandberg (
Sun, 27 Jul 1997 23:13:10 +0200 (MET DST)

On Fri, 25 Jul 1997, Andrea Gallagher wrote:

> I'm curious if people thing long-term memory retention will be a problem
> for people who live much longer in their current bodies and brains.
- - -
> do we still think this will be a big
> concern? If we fix Alzheimer's, what are the reasons to think that
> long-term memory is more limited for 140 year olds than for 40 year olds?

I'm happy you asked, since I'm actually working in this area (human
memory) right now. This is what is sometimes called the "catastrophic
forgetting" problem - if you teach more and more to a neural network
eventually the stored information will start to interfere with itself
and recall goes down. In some networks (like Hopfield nets) this is a
very sudden collapse from a farily "lucid" network to an useless
"senile" network. In other kinds of networks (like Hopfield nets
with clipped weights) the disaster doesn't occur, instead old
memories are gradually erased by new ones.

We don't know what kind of network the human brain is most similar
to, but for a variety of reasons it is likely that it is the later
case. So far nobody has shown any evidence of catastrophic forgetting
(no, Alzheimer is not it, and besides, getting a lot of education
seems to *prevent* dementia instead of causing it). My current
research is looking into how neural plasticity is controlled so that
new memories doesn't erase old ones too fast or too slowly (the
dreade stability-plasticity dilemma).

What will happen if we can extend our lifespans for (say) 500
years? My guess is that no catastrophic forgetting will occur, but
that newer memories slowly erode older memories. Childhood memories
might be exempt from this, they appear to be very solid. The 500-year
old might remember what he or shw did the last decades fairly
clearly, while more distant eras have been gradually erased ("I have
some vague impressions of the 21st century, but they might be based
on some VR I once saw..."). Often used skills or memories will
likely remain, while less used concepts will fade. It might be a good
idea to regularly do a test to review what fields one need to freshen
up, say every 50th year or so.

> If this really is a problem, maybe it's a use for those life-recordings,
> no? It would suck if you lost all the experiences that happened between
> childhood and when you get uploaded.

I think it would be a good idea to store them just to be able to
review and document your life for all your future selves. They would
make ideal material for the memory freshening sessions.

Anders Sandberg Towards Ascension!
GCS/M/S/O d++ -p+ c++++ !l u+ e++ m++ s+/+ n--- h+/* f+ g+ w++ t+ r+ !y