[extropy-chat] The Story of a Brain

[Hal Finney]

I sent a version of this posting five years ago, but I thought people
might enjoy seeing it again.  Unfortunately I have not been able to find
an online copy of the essay that I paraphrase.

One of the articles in the collection The Mind's I, edited by Hofstadter
and Dennett, has always struck me as posing difficult problems relating
to instantiation and playback questions.  It is The Story of a Brain, by
Arnold Zuboff.  I will summarize a portion here.  This is a simplification
of Zuboff's arguments but I think catches the main idea.

A man greatly admired by his society has died.  However in order to show
their gratitude and love, his people have taken it upon themselves to
preserve his brain and induce pleasant experiences in it.  They believe
that by stimulating his neurons in appropriate patterns they are able
to create the corresponding conscious experiences.

At first this is just done by stimulating the sensory inputs to the brain.
Then at some point there is an accident, and the brain is damaged.  It is
split into its two hemispheres and the bridge between them is destroyed.
The brain is repaired by installing artificial connections between
the two hemispheres to replace the damaged nerve fibers.  With these
connections in place the brain is able to be stimulated as before.

Later, society realizes that the wires connecting the brain hemispheres
don't need to be solid and can be replaced by radio transmitters
and receivers.  The signals still get from one side to the other, but
now the two hemispheres can be separated, which is more convenient.
Many people want to be involved in the project and now two labs can
participate rather than just one.

However, separating the brains by too much causes problems due to
time lag for the radio signals.  At this point a new method is used.
Instead of actually communicating with the other hemisphere, the nerve
fibers for each side terminate in an "impulse cartridge".  This is a
device which produces the same signals that would have been produced by
the opposite hemisphere, but it computes them inside itself.  In this
way each hemisphere gets exactly the necessary signals even though it
is no longer communicating with the other side.

This change is successful, and now that the process has been shown to
work with the brain in two pieces, it gets divided further.  Many people
want to participate.  So each hemisphere gets subdivided and fitted
with an impulse cartridge which supplies the signals that would have
been produced by the rest of the brain.  In this way many labs can
participate.

Fast forward a few centuries, and the project has become a world-wide
obsession.  Everyone is involved.  Each person has one neuron that he
is responsible for.  The neurons sit in small nutrient baths, and when
it is time for a new experience to be delivered, each person receives
instructions for the timing of how they are to stimulate their neuron.
At the appropriate moment, each person delivers the specified patterns
of stimulation all over the world, and the neurons go through the same
patterns of activity which they would have if they were actually in
the man's brain when he was experiencing some pleasurable activity.
It is still thought that by doing this they actually bring about the
corresponding mental state.

Now it happens one day that just when a new experience-delivery is about
to begin, one person finds that his neuron has died.  He knows that this
won't affect the overall experience, since neurons die all the time and
we can't tell if there are a few more or less.  But he is personally
disappointed because he knows that he will not be able to play his own
small part in delivering the happy experience.

Then he gets an idea.  His own brain is full of neurons as well, firing
all the time.  At the appropriate time, he moves the neural bath out of
the way and bends over and puts his own brain into the position where
"his" neuron is normally kept.  Since his own brain is active, he is
sure to have a neuron fire which is in the right place and at the right
time for each of the stimulations he is supposed to give.  In this way
he can participate in delivering the experience using the neurons in
his head rather than the one in the bath.

But then he thinks, why bend over?  It doesn't matter where the neurons
are located, all that matters is the pattern of their stimulation.
And then he thinks, what about all the other people who are stimulating
their own neurons?  They have brains too, full of neurons just like his.
Any time they were supposed to be stimulating their neuron in its bath,
they had neurons in their head which were firing at exactly that moment.
If all that is necessary to produce a conscious experience is to have
neurons fire at the specified times and places, there is no need for
anyone to stimulate anything.  Just by standing there, their own brains
provide more than enough neural firings to produce any neural pattern
(and therefore any mental experience) imaginable.

It would seem to follow, then, that the entire enterprise has been
a folly.  Either all possible mental states are existing all the time
just due to random neural firings in disconnected brains all over the
world, or else these carefully planned stimulations, which were designed
to mimic actual neural patterns in a conscious brain, were not actually
producing any mental states.

So, what do you think?  Were they producing mental states by stimulating
those neurons?  And if so, are they still produced when they just stand
their and let their brains do the work of firing neurons?

Hal