X-Message-Number: 12634
From: Thomas Donaldson <>
Subject: about how brains work
Date: Tue, 26 Oct 1999 00:48:01 +1000 (EST)

Hi everyone!

While I hesitate to praise myself, I will point out that PERIASTRON has 
spent years discussing the different features of LTP and LTD, and how they
act as the initial stages in formation of memories. Clearly how our brains
work is important to any program to freeze or vitrify them so that they

Seriously, guys, if you don't study up on their background, these papers
on LTP or the density of "information" in neurons (otherwise known as
the density of synapses) are going to very easy to misunderstand. One
major misunderstanding which apparently exists in several recent posts
is that LTP or LTD are themselves the forms that long term memory takes.
The problem with this is that once rats or other animals have been
trained up, say, on a maze, then the experience of the maze will no
longer produce LTP or LTD in any of their neurons. No, they haven't
forgotten; it's just that both activities pertain only to the earlier
stages of learning. The end result consists of a modification of the
neuron's synapses, including sometimes the growth of new synapses, and
with this the animal will automatically behave according to its past

I will provide lots of references to anyone who is interested. But most
of all, I took up that subject of memory and how it worked precisely
because it was the one feature which we want to preserve but did not
know how to do that preservation. (All else can be done by cloning or
other such methods). And over the last 15 years there's been lots of
progress in understanding how brains work. No, we're not yet at a time
in which all pertinent questions have been answered, but many have and
we have a better understanding than we used to.

I'll also point out (to those who are so fond of returning, somehow, as
computers) that if you want your return to be successful, you too should
be interested in how your brain works, particularly for memory and 
your sense of identity (both of which are now researched by many neuro-
scientists). If we don't know how brains work, we can hardly know how
to resurrect you, even in a computer. (And even if you want to go on
from there into a quite different form, you still have to START with
your memories in a brainlike entity).

Finally, although the kind of neural net very likely differs from any
computer neural net yet devised, we consist of many interconnected
neural nets. And if you read about neural nets you'll find interesting
things --- particularly those which, like our brains, can learn without
explicitly being told. One interesting fact is that reading the content
of a neural net's memories into a binary scheme of bits isn't at all
trivial. Yes, in at least one special case it's made easy by the specific
structure of the neural net (each "neuron" gets 2 inputs, which only take
ON or OFF. It then passes the combined result to another "neuron"). But
it's quite clear that our brains are not built that way... most computer
neural nets, even, aren't built that way.

			Best wishes and long long life to all,

				Thomas Donaldson

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